203 results on '"Robert H. Becker"'
Search Results
2. Erratum: The properties of radio galaxies and the effect of environment in large-scale structures at z ∼ 1
- Author
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Lu Shen, Neal A Miller, Brian C Lemaux, Adam R Tomczak, Lori M Lubin, Nicholas Rumbaugh, Christopher D Fassnacht, Robert H Becker, Roy R Gal, Po-Feng Wu, and Gordon Squires
- Subjects
Space and Planetary Science ,Astronomy and Astrophysics - Published
- 2018
3. Possible evidence of the radio AGN quenching of neighbouring galaxies at z ̃ 1
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Lori M. Lubin, Adam Tomczak, Lu Shen, Roy R. Gal, N. Miller, Debora Pelliccia, Robert H. Becker, Po-Feng Wu, Gordon K. Squires, Christopher D. Fassnacht, Brian C. Lemaux, and Serena Perrotta
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Physics ,education.field_of_study ,Active galactic nucleus ,Stellar mass ,010308 nuclear & particles physics ,Star formation ,Population ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Radius ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Galaxy ,Redshift ,Space and Planetary Science ,Intracluster medium ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,education ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Using 57 Radio Active Galactic nuclei (RAGN) at 0.55 $\leq$ z $\leq$ 1.3 drawn from five fields of the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey, we study the effect of injection of energy from outbursts of RAGN on their spectroscopically-confirmed neighboring galaxies (SNGs). We observe an elevated fraction of quenched neighbors (fq) within 500 kpc projected radius of RAGN in the most dense local environments compared to those of non-RAGN control samples matched to the RAGN population in colour, stellar mass, and local environment at 2$\sigma$ significance. Further analyses show that there are offsets at similar significance between fqs of RAGN-SNGs and the appropriate control samples for galaxies specifically in cluster environments and those hosted by most massive cluster galaxies, which tentatively suggests that some negative feedback from the RAGN is occurring in these dense environments. In addition, we find that the median radio power of RAGN increases with increasing local overdensity, an effect which may lend itself to the quenching of neighboring galaxies. Furthermore, we find that, in the highest local overdensities, the fq of the sub-sample of lower stellar mass RAGN-SNGs is larger than that of the higher stellar mass RAGN-SNGs sub-sample, which indicates a more pronounced effect from RAGN on lower stellar mass galaxies. We propose a scenario in which RAGN residing within clusters might heat the intracluster medium (ICM) affecting both in situ star formation and any inflowing gas that remains in their neighboring galaxies., Comment: submitted to MNRAS, 15 pages, 2 tables and 6 figures, comments welcome
- Published
- 2019
4. Erratum: 'A New, Deep JVLA Radio Survey of M33' (2019, ApJS, 241, 37)
- Author
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Knox S. Long, Richard L. White, Robert H. Becker, P. Frank Winkler, William P. Blair, and David J. Helfand
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Physics ,Space and Planetary Science ,Astronomy ,Astronomy and Astrophysics - Published
- 2020
5. The Properties of Radio Galaxies and the Effect of Environment in Large Scale Structures at $z\sim1$
- Author
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Brian C. Lemaux, Adam Tomczak, Lu Shen, Christopher D. Fassnacht, Roy R. Gal, Robert H. Becker, Nicholas Rumbaugh, Lori M. Lubin, Po-Feng Wu, N. Miller, and Gordon K. Squires
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Physics ,education.field_of_study ,Active galactic nucleus ,Stellar mass ,010308 nuclear & particles physics ,Star formation ,Radio galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,Astronomy ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Redshift ,X-shaped radio galaxy ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,education ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
In this study we investigate 89 radio galaxies that are spectroscopically-confirmed to be members of five large scale structures in the redshift range of $0.65 \le z \le 0.96$. Based on a two-stage classification scheme, the radio galaxies are classified into three sub-classes: active galactic nucleus (AGN), hybrid, and star-forming galaxy (SFG). We study the properties of the three radio sub-classes and their global and local environmental preferences. We find AGN hosts are the most massive population and exhibit quiescence in their star-formation activity. The SFG population has a comparable stellar mass to those hosting a radio AGN but are unequivocally powered by star formation. Hybrids, though selected as an intermediate population in our classification scheme, were found in almost all analyses to be a unique type of radio galaxies rather than a mixture of AGN and SFGs. They are dominated by a high-excitation radio galaxy (HERG) population. We discuss environmental effects and scenarios for each sub-class. AGN tend to be preferentially located in locally dense environments and in the cores of clusters/groups, with these preferences persisting when comparing to galaxies of similar colour and stellar mass, suggesting that their activity may be ignited in the cluster/group virialized core regions. Conversely, SFGs exhibit a strong preference for intermediate-density global environments, suggesting that dusty starbursting activity in LSSs is largely driven by galaxy-galaxy interactions and merging., Comment: 28 pages, 10 figures, accepted to MNRAS
- Published
- 2017
- Full Text
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6. The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7
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Xiaohui Fan, Eduardo Bañados, Feige Wang, Robert H. Becker, Jin Wu, Kara Farnsworth, Yue Shen, Michael A. Strauss, Shu Wang, Ran Wang, Jinyi Yang, Linhua Jiang, Qian Yang, Richard L. White, Xue-Bing Wu, Fuyan Bian, and Ian D. McGreer
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media_common.quotation_subject ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Luminosity ,0103 physical sciences ,education ,010303 astronomy & astrophysics ,Reionization ,Luminosity function ,Astrophysics::Galaxy Astrophysics ,media_common ,Physics ,education.field_of_study ,010308 nuclear & particles physics ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Quasar ,Astrophysics - Astrophysics of Galaxies ,Redshift ,Space and Planetary Science ,Sky ,Magnitude (astronomy) ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
We present the discovery of nine quasars at $z\sim6$ identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of $z\sim6$ quasars in the SDSS footprint. Our final sample consists of 52 quasars at $5.7, Comment: 20 pages, 12 figures, Accepted for publication in The Astrophysical Journal
- Published
- 2016
7. A New, Deep JVLA Radio Survey of M33
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David J. Helfand, P. Frank Winkler, Richard L. White, Knox S. Long, William P. Blair, and Robert H. Becker
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,H II region ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Synchrotron radiation ,Local Group ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Galaxy ,Luminosity ,Jansky ,Supernova ,Space and Planetary Science ,0103 physical sciences ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,Image resolution ,Astrophysics::Galaxy Astrophysics - Abstract
We have performed new 1.4 GHz and 5 GHz observations of the Local Group galaxy M33 with the Jansky Very Large Array. Our survey has a limiting sensitivity of 20 uJy (4-sigma) and a resolution of 5.9 arcsec (FWHM), corresponding to a spatial resolution of 24 pc at 817 kpc. Using a new multi-resolution algorithm, we have created a catalog of 2875 sources, including 675 with well-determined spectral indices. We detect sources at the position of 319 of the X-ray sources in the Tuellmann et al. (2011) Chandra survey of M33, the majority of which are likely to be background galaxies. The radio source coincident with M33 X-8, the nuclear source, appears to be extended. Along with numerous H II regions or portions of H II region complexes, we detect 155 of the 217 optical supernova remnants included in the lists of Long et al. (2010) and Lee & Lee (2014), making this by far the largest sample of remnants at known distances with multiwavelength coverage. The remnants show a large dispersion in the ratio of radio to X-ray luminosity at a given diameter, a result that challenges the current generation of models for synchrotron radiation evolution in supernova remnants. See http://sundog.stsci.edu/m33 for access to catalogs and images., 37 pages, 24 figures; Accepted for publication in the Astrophysical Journal; see http://sundog.stsci.edu/m33 for access to catalogs and images
- Published
- 2019
8. Implications of dramatic broad absorption line variability in the quasar FBQS J1408+3054
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R. R. Gibson, W. N. Brandt, Donald P. Schneider, Konstantin Anosov, Patrick B. Hall, Richard L. White, Michael D. Gregg, and Robert H. Becker
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Luminous infrared galaxy ,Physics ,Line-of-sight ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,Continuum (design consultancy) ,Astronomy and Astrophysics ,Context (language use) ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Space and Planetary Science ,0103 physical sciences ,Outflow ,010303 astronomy & astrophysics ,Equivalent width ,Schwarzschild radius ,Astrophysics::Galaxy Astrophysics - Abstract
We have observed a dramatic change in the spectrum of the formerly heavily absorbed `overlapping-trough' iron low-ionization broad absorption line (FeLoBAL) quasar FBQS J1408+3054. Over a time span of between 0.6 to 5 rest-frame years, the Mg II trough outflowing at 12,000 km/s decreased in equivalent width by a factor of two and the Fe II troughs at the same velocity disappeared. The most likely explanation for the variability is that a structure in the BAL outflow moved out of our line of sight to the ultraviolet continuum emitting region of the quasar's accretion disk. Given the size of that region, this structure must have a transverse velocity of between 2600 km/s and 22,000 km/s. In the context of a simple outflow model, we show that this BAL structure is located between approximately 5800 and 46,000 Schwarzschild radii from the black hole. That distance corresponds to 1.7 to 14 pc, 11 to 88 times farther from the black hole than the H-beta broad-line region. The high velocities and the parsec-scale distance for at least this one FeLoBAL outflow mean that not all FeLoBAL outflows can be associated with galaxy-scale outflows in ultraluminous infrared galaxies transitioning to unobscured quasars. The change of FBQS J1408+3054 from an FeLoBAL to a LoBAL quasar also means that if (some) FeLoBAL quasars have multiwavelength properties which distinguish them from HiBAL quasars, then some LoBAL quasars will share those properties. Finally, we extend previous work on how multiple-epoch spectroscopy of BAL and non-BAL quasars can be used to constrain the average lifetime of BAL episodes (currently >60 rest-frame years at 90% confidence).
- Published
- 2010
9. FAINT, EVOLVING RADIO ACTIVE GALACTIC NUCLEI IN SDSS LUMINOUS RED GALAXIES
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R. L. White, Robert H. Becker, Gregory R. Zeimann, and Jacqueline Hodge
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Physics ,education.field_of_study ,Active galactic nucleus ,Star formation ,Radio galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Galaxy ,Luminosity ,Stars ,Space and Planetary Science ,education ,Astrophysics::Galaxy Astrophysics - Abstract
We detect and study the properties of faint radio active galactic nuclei (AGNs) in luminous red galaxies (LRGs). The LRG sample comprises 760,000 objects from a catalog of LRG photometric redshifts constructed from the Sloan Digital Sky Survey (SDSS) imaging data, and 65,000 LRGs from the SDSS spectroscopic sample. These galaxies have typical 1.4 GHz flux densities in the 10s-100s of μJy, with the contribution from a low-luminosity AGN dominating any contribution from star formation. To probe the radio properties of such faint objects, we employ a stacking technique whereby FIRST survey image cutouts at each optical LRG position are sorted by the parameter of interest and median-combined within bins. We find that median radio luminosity scales with optical luminosity (L opt) as L 1.4 GHz L β opt, where β depends on the redshift being probed. Above z 0.4, β appears to decrease from β 1 at z = 0.4 to β 0 at z = 0.7, a result which could be indicative of AGN cosmic downsizing. We also find that the overall LRG population, which is dominated by low-luminosity AGNs, experiences significant cosmic evolution between z = 0.2 and z = 0.7. A simultaneous fit to untangle the redshift and luminosity dependences yields redshift evolution of the form L 1.4 GHz (1 + z)3.15±0.07, implying a considerable increase in total AGN heating for these massive ellipticals with redshift. By matching against the FIRST catalog, we investigate the incidence and properties of LRGs associated with double-lobed (FR I/II) radio galaxies.
- Published
- 2009
10. THE FIRST-2MASS RED QUASAR SURVEY. II. AN ANOMALOUSLY HIGH FRACTION OF LoBALs IN SEARCHES FOR DUST-REDDENED QUASARS
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Michael D. Gregg, Tanya Urrutia, Eilat Glikman, Robert H. Becker, Jacqueline Hodge, Mark Lacy, and Richard L. White
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Physics ,Infrared ,Star formation ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Redshift ,Spectral line ,Space and Planetary Science ,Sky ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Galaxy Astrophysics ,Line (formation) ,media_common - Abstract
We present results on a survey to find extremely dust-reddened Type-1 Quasars. Combining the FIRST radio survey, the 2MASS Infrared Survey and the Sloan Digital Sky Survey, we have selected a candidate list of 122 potential red quasars. With more than 80% spectroscopically identified objects, well over 50% are classified as dust-reddened Type 1 quasars, whose reddenings (E(B-V)) range from approximately 0.1 to 1.5 magnitudes. They lie well off the color selection windows usually used to detect quasars and many fall within the stellar locus, which would have made it impossible to find these objects with traditional color selection techniques. The reddenings found are much more consistent with obscuration happening in the host galaxy rather than stemming from the dust torus. We find an unusually high fraction of Broad Absorption Line (BAL) quasars at high redshift, all but one of them belonging to the Low Ionization BAL (LoBAL) class and many also showing absorption the metastable FeII line (FeLoBAL). The discovery of further examples of dust-reddened LoBAL quasars provides more support for the hypothesis that BAL quasars (at least LoBAL quasars) represent an early stage in the lifetime of the quasar. The fact that we see such a high fraction of BALs could indicate that the quasar is in a young phase in which quasar feedback from the BAL winds is suppressing star formation in the host galaxy., 17 pages, 7 figures, accepted for publication in ApJ
- Published
- 2009
11. FIVE NEW HIGH-REDSHIFT QUASAR LENSES FROM THE SLOAN DIGITAL SKY SURVEY
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Robert H. Becker, Issha Kayo, Michael A. Strauss, Neta A. Bahcall, Donald P. Schneider, Masamune Oguri, Donald G. York, Min-Su Shin, Tomoki Morokuma, and Naohisa Inada
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Physics ,010308 nuclear & particles physics ,media_common.quotation_subject ,Image (category theory) ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Galaxy ,Redshift ,law.invention ,Lens (optics) ,Space and Planetary Science ,law ,Sky ,Image separation ,0103 physical sciences ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discovery of five gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). All five systems are selected as two-image lensed quasar candidates from a sample of high-redshift (z>2.2) SDSS quasars. We confirmed their lensing nature with additional imaging and spectroscopic observations. The new systems are SDSS J0819+5356 (source redshift z_s=2.237, lens redshift z_l=0.294, and image separation \theta=4.04"), SDSS J1254+2235 (z_s=3.626, \theta=1.56"), SDSS J1258+1657 (z_s=2.702, \theta=1.28"), SDSS J1339+1310 (z_s=2.243, \theta=1.69"), and SDSS J1400+3134 (z_s=3.317, \theta=1.74"). We estimate the lens redshifts of the latter four systems to be z_l=0.2-0.8 from the colors and magnitudes of the lensing galaxies. We find that the image configurations of all systems are well reproduced by standard mass models. Although these lenses will not be included in our statistical sample of z_s, Comment: 25 pages, 5 figures, 6 tables, accepted for publication in AJ; see http://www-utap.phys.s.u-tokyo.ac.jp/~sdss/sqls/ for an up-to-date status of the SQLS
- Published
- 2009
12. THE RADIO CONTENT OF GLIMPSE
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R. L. White, U. Giveon, and Robert H. Becker
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Physics ,Brightness ,Molecular cloud ,Young stellar object ,Galactic quadrant ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Galactic plane ,law.invention ,Stars ,Space and Planetary Science ,law ,Disc ,Maser - Abstract
We present results from matching a Very Large Array Galactic plane catalog at 6 cm covering the first Galactic quadrant (350° ≤ l ≤ 42°, |b| ≤ 0.4°), the MSX6C Galactic plane catalog, and the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire v1.0 (GLIMPSE I) catalog. The much higher angular resolution and better sensitivity provided by GLIMPSE should improve the identification of embedded Galactic star-forming regions, and enable the study of the relationships between the central stellar sources, the ionized gas, and the surrounding dust. The GLIMPSE catalog is so crowded compared to our 6 cm catalog that it actually leads to confusion in identifying chance alignments, but this is resolved when separating GLIMPSE into red (M 3.6 μm – M 8 μm > 2.5) and blue (M 3.6 μm – M 8 μm < 2.5) sub-catalogs. In spite of the improved properties of GLIMPSE, we find a very small number of GLIMPSE-6cm high-reliability matches in the overlapping area of the two samples (10° ≤ l ≤ 42°, |b| ≤ 0.4°)—132, only 55 of them have a Midcourse Space Experiment (MSX) counterpart. Even though the matching results are less successful than expected, there are still some general outcomes to them. First, we discover an obscuration effect around our candidates: the average local source density of blue sources, dominated by stars, is decreasing toward the radio positions; their average brightness increases, and their color reddens significantly, supporting the picture in which background sources disappear behind the opaque nebulae associated with the radio source. Second, the selected sources define near and mid-infrared color criteria, which are used to detect a total of 849 GLIMPSE sources in the entire GLIMPSE survey that have MSX matches and that show the same collective behavior. Only 15% of these sources are previously classified, mainly as H II regions, masers, young stellar objects, and molecular clouds.
- Published
- 2008
13. THE ENVIRONMENTS OF LOW- AND HIGH-LUMINOSITY RADIO GALAXIES AT MODERATE REDSHIFTS
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Robert H. Becker, Matthew W. Auger, and Christopher D. Fassnacht
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Physics ,Radio galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Universe ,Redshift ,Luminosity ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
In the local Universe, high-power radio galaxies live in lower density environments than low-luminosity radio galaxies. If this trend continues to higher redshifts, powerful radio galaxies would serve as efficient probes of moderate redshift groups and poor clusters. Photometric studies of radio galaxies at 0.3 < z < 0.5 suggest that the radio luminosity-environment correlation disappears at moderate redshifts, though this could be the result of foreground/background contamination affecting the photometric measures of environment. We have obtained multi-object spectroscopy of in the fields of 14 lower luminosity (L_1.4GHz < 4x10^24 W/Hz) and higher luminosity (L_1.4GHz > 1.2x10^25 W/Hz) radio galaxies at z ~ 0.3 to spectroscopically investigate the link between the environment and the radio luminosity of radio galaxies at moderate redshifts. Our results support the photometric analyses; there does not appear to be a correlation between the luminosity of a radio galaxy and its environment at moderate redshifts. Hence, radio galaxies are not efficient signposts for group environments at moderate redshifts., 7 pages, 9 figures, Accepted for publication in AJ
- Published
- 2008
14. A SURVEY OFz∼ 6 QUASARS IN THE SLOAN DIGITAL SKY SURVEY DEEP STRIPE. I. A FLUX-LIMITED SAMPLE ATzAB< 21
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Huan Lin, Robert H. Becker, Gordon T. Richards, Kuenley Chiu, James Annis, Xiaohui Fan, Michael A. Strauss, Robert H. Lupton, Linhua Jiang, Donald P. Schneider, Sebastian Jester, and Richard L. White
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Physics ,education.field_of_study ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Celestial equator ,Population ,Astrophysics::Instrumentation and Methods for Astrophysics ,Flux ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Power law ,Luminosity ,Space and Planetary Science ,Sky ,0103 physical sciences ,education ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Luminosity function ,media_common - Abstract
We present the discovery of five quasars at z~6 selected from 260 deg^2 of the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the Celestial Equator. The five quasars with 20 =6.0 and =-25.8 is (5.0+/-2.1) x 10^{-9} Mpc^{-3} mag^{-1}. We model the bright-end quasar luminosity function (QLF) at z~6 as a power law Phi(L_{1450}) \propto L_{1450}^{beta}. The slope beta calculated from a combination of our sample and the luminous SDSS quasar sample is -3.1+/-0.4, significantly steeper than the slope of the QLF at z~4. Based on the derived QLF, we find that the quasar/AGN population cannot provide enough photons to ionize the intergalactic medium (IGM) at z~6 unless the IGM is very homogeneous and the luminosity (L*_{1450}) at which the QLF power law breaks is very low.
- Published
- 2008
15. THE SLOAN DIGITAL SKY SURVEY QUASAR LENS SEARCH. II. STATISTICAL LENS SAMPLE FROM THE THIRD DATA RELEASE
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Michael D. Gregg, Masamune Oguri, Patrick B. Hall, Alejandro Clocchiatti, Bartosz Pindor, Hans-Walter Rix, David Johnston, Tomoki Morokuma, Neta A. Bahcall, Scott F. Anderson, Min-Su Shin, Michael A. Strauss, Robert H. Lupton, Daniel J. Eisenstein, Issha Kayo, Joshua A. Frieman, Scott Burles, Charles R. Keeton, Ryan Scranton, Yozo Kawano, Edwin L. Turner, Christopher S. Kochanek, Robert J. Brunner, Richard L. White, Robert H. Becker, Erin S. Sheldon, Gordon T. Richards, Joseph F. Hennawi, Donald G. York, Francisco J. Castander, Kuenley Chiu, Naohisa Inada, Donald P. Schneider, and Masataka Fukugita
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Physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Redshift ,law.invention ,Lens (optics) ,Space and Planetary Science ,Sky ,law ,Magnitude (astronomy) ,Astrophysics::Solar and Stellar Astrophysics ,Data release ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,media_common - Abstract
We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 (~4188 deg^2), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1'' and 20'' and flux ratios of faint to bright lensed images larger than 10^{-0.5}. We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations (~1''-2'') and one is a large separation (15'') system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample., Comment: 15 pages, 4 figures, 5 tables, accepted for publication in AJ; see http://www-utap.phys.s.u-tokyo.ac.jp/~sdss/sqls/ for supplemental information
- Published
- 2008
16. Star Formation in Low Radio Luminosity Active Galactic Nuclei from the Sloan Digital Sky Survey
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R. L. White, Robert H. Becker, W. H. de Vries, David J. Helfand, and J. A. Hodge
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Physics ,Active galactic nucleus ,Star formation ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Doubly ionized oxygen ,Velocity dispersion ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Galaxy ,Luminosity ,Space and Planetary Science ,Sky ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We investigate faint radio emission from low- to high-luminosity active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. Their radio properties are inferred by co-adding large ensembles of radio image cut-outs from the FIRST survey, as almost all of the sources are individually undetected. We correlate the median radio flux densities against a range of other sample properties, including median values for redshift, [O III] luminosity, emission-line ratios, and the strength of the 4000 A break. We detect a strong trend for sources that are actively undergoing star formation to have excess radio emission beyond the ~1028 ergs s-1 Hz-1 level found for sources without any discernible star formation. Furthermore, this additional radio emission correlates well with the strength of the 4000 A break in the optical spectrum, and may be used to assess the age of the star-forming component. We examine two subsamples, one containing the systems with emission-line ratios most like star-forming systems, and one with the sources that have characteristic AGN ratios. This division also separates the mechanism responsible for the radio emission (star formation vs. AGNs). For both cases we find a strong, almost identical correlation between [O III] and radio luminosity, with the AGN sample extending toward lower, and the star formation sample toward higher luminosities. A clearer separation between the two subsamples is seen as function of the central velocity dispersion σ of the host galaxy. For systems at similar redshifts and values of σ, the star formation subsample is brighter than the AGN in the radio by an order of magnitude. This underlines the notion that the radio emission in star-forming systems can dominate the emission associated with the AGN.
- Published
- 2007
17. Signals from the Noise: Image Stacking for Quasars in the FIRST Survey
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Eilat Glikman, Robert H. Becker, Richard L. White, Wim deVries, and David J. Helfand
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Physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Radio flux ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Rms noise ,Spectral line ,Loudness ,Focus stacking ,Distribution function ,Space and Planetary Science ,Sky ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We present a technique to explore the radio sky into the nanoJansky regime by employing image stacking using the FIRST survey. We first discuss the non-intuitive relationship between the mean and median values of a distribution that is dominated by noise, followed by an analysis of the systematic effects present in FIRST's 20cm VLA snapshot images. Image stacking allows us to recover the properties of source populations with fluxes a factor of 30 or more below the rms noise level. Mean estimates of radio flux density, luminosity, etc., are derivable for any source class having arcsecond positional accuracy. We use this technique to compute the mean radio properties for 41,295 quasars from the SDSS DR3 catalog. There is a tight correlation between optical and radio luminosity, with the radio luminosity increasing as the 0.85 power of optical luminosity. This implies declining radio-loudness with optical luminosity: the most luminous objects (M=-28.5) have average radio-to-optical ratios 3 times lower than the least luminous objects (M=-20). There is also a striking correlation between optical color and radio loudness: quasars that are either redder or bluer than the norm are brighter radio sources, with objects 0.8 magnitudes redder than the SDSS composite spectrum having radio-loudness ratios that are higher by a factor of 10. We explore the longstanding question of whether a radio-loud/radio-quiet dichotomy exists in quasars, finding that optical selection effects probably dominate the distribution function of radio loudness, which has at most a modest (~20%) inflection between the radio-loud and radio-quiet ends of the distribution. We also find, surprisingly, that broad absorption line quasars have higher mean radio flux densities, with the greatest disparity arising in the rare low-ionization BAL subclass., Comment: 17 pages, 19 figures, accepted by ApJ; corrected error in absolute magnitudes
- Published
- 2007
18. Two New Gravitationally Lensed Double Quasars from the Sloan Digital Sky Survey
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Robert H. Becker, Naohisa Inada, Richard L. White, Patrick B. Hall, Issha Kayo, Donald P. Schneider, Donald G. York, Gordon T. Richards, Christopher S. Kochanek, and Masamune Oguri
- Subjects
Physics ,Lens sample ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Cosmology ,Redshift ,law.invention ,Lens (optics) ,Space and Planetary Science ,law ,Sky ,Image separation ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discoveries of the two-image gravitationally lensed quasars, SDSS J0746+4403 and SDSS J1406+6126, selected from the Sloan Digital Sky Survey (SDSS). SDSS J0746+4403, which will be included in our lens sample for statistics and cosmology, has a source redshift of z_s=2.00, an estimated lens redshift of z_l~0.3, and an image separation of 1.08". SDSS J1406+6126 has a source redshift of z_s=2.13, a spectroscopically measured lens redshift of z_l=0.27, and an image separation of 1.98". We find that the two quasar images of SDSS J1406+6126 have different intervening MgII absorption strengths, which are suggestive of large variations of absorbers on kpc scales. The positions and fluxes of both the lensed quasar systems are easily reproduced by simple mass models with reasonable parameter values. These objects bring to 18 the number of lensed quasars that have been discovered from the SDSS data., Comment: 25 pages, 6 figures, The Astronomical Journal accepted
- Published
- 2006
19. SDSS J1029+2623: A Gravitationally Lensed Quasar with an Image Separation of 22.'5
- Author
-
Donald G. York, Joseph F. Hennawi, Naohisa Inada, Robert H. Becker, Tomoki Morokuma, Gordon T. Richards, Min-Su Shin, Issha Kayo, Masataka Fukugita, Donald P. Schneider, Masamune Oguri, Kohki Konishi, Christopher S. Kochanek, Erin S. Sheldon, Xinyu Dai, Mamoru Doi, Michael A. Strauss, Naoki Yasuda, and Hiroyuki Utsunomiya
- Subjects
Physics ,media_common.quotation_subject ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Optical spectra ,law.invention ,Lens (optics) ,Space and Planetary Science ,law ,Sky ,Image separation ,Physics::Space Physics ,Cluster (physics) ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,media_common - Abstract
We report the discovery of a cluster-scale lensed quasar, SDSS J1029+2623, selected from the Sloan Digital Sky Survey. The lens system exhibits two lensed images of a quasar at z_s=2.197. The image separation of 22.5" makes it the largest separation lensed quasar discovered to date. The similarity of the optical spectra and the radio loudnesses of the two components support the lensing hypothesis. Images of the field show a cluster of galaxies at z_l~0.55 that is responsible for the large image separation. The lensed images and the cluster light center are not collinear, which implies that the lensing cluster has a complex structure.
- Published
- 2006
20. Discovery of az= 6.1 Radio‐Loud Quasar in the NOAO Deep Wide Field Survey
- Author
-
David J. Helfand, Robert H. Becker, Richard L. White, and Ian D. McGreer
- Subjects
Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Population ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Spectral line ,law.invention ,Luminosity ,Telescope ,law ,0103 physical sciences ,education ,Spectroscopy ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common ,Physics ,education.field_of_study ,010308 nuclear & particles physics ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Quasar ,Redshift ,Space and Planetary Science ,Sky - Abstract
From examination of only 4 deg^2 of sky in the NOAO Deep Wide-Field Survey (NDWFS) region, we have identified the first radio-loud quasar at a redshift z>6. The object, FIRST J1427385+331241, was discovered by matching the FLAMEX IR survey to FIRST survey radio sources with NDWFS counterparts. One candidate z>6 quasar was found, and spectroscopy with the Keck II telescope confirmed its identification, yielding a redshift z=6.12. The object is a Broad Absorption Line (BAL) quasar with an optical luminosity of M_B ~ -26.9 and a radio-to-optical flux ratio ~ 60. Two MgII absorptions systems are present at redshifts of z=2.18 and z=2.20. We briefly discuss the implications of this discovery for the high-redshift quasar population.
- Published
- 2006
21. XMM-NewtonDetection of the Rare Fanaroff-Riley Type II Broad Absorption Line Quasar FIRST J101614.3+520916
- Author
-
Michael D. Gregg, Sally A. Laurent-Muehleisen, Mark Lacy, Justin J. Schaefer, Michael S. Brotherton, Zhaohui Shang, Richard L. White, and Robert H. Becker
- Subjects
Physics ,Jet (fluid) ,Photon ,Astrophysics::High Energy Astrophysical Phenomena ,Mirror reflection ,Flux ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Spectral line ,Space and Planetary Science ,Observatory ,Ionization - Abstract
We have detected FIRST J101614.3+520916 with the XMM-Newton X-ray Observatory. FIRST J101614.3+520916, one of the most extreme radio-loud, broad absorption line (BAL) quasars so far discovered, is also a Fanaroff-Riley type II (FR II) radio source. We find that, compared to its estimated intrinsic X-ray flux, the observed X-rays are likely suppressed, and that the observed hardness ratio indicates significant soft X-ray photons. This is inconsistent with the simplest model, a normal quasar spectrum absorbed by a large neutral HI column density, which would primarily absorb the softer photons. More complex models, involving partial covering, an ionized absorber, ionized mirror reflection, or jet contributions need to be invoked to explain this source. The suppressed but soft X-ray emission in this radio-loud BAL quasar is consistent with the behavior displayed by other BAL quasars, both radio-loud and radio-quiet.
- Published
- 2006
22. MAGPIS: A Multi-Array Galactic Plane Imaging Survey
- Author
-
Adam Fallon, David J. Helfand, Sarah Tuttle, Richard L. White, and Robert H. Becker
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Milky Way ,Galactic quadrant ,Astronomy ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galactic plane ,Pulsar wind nebula ,Stars ,Pulsar ,Space and Planetary Science ,Angular resolution ,Supernova remnant ,Astrophysics::Galaxy Astrophysics - Abstract
We present the Multi-Array Galactic Plane Imaging Survey (MAGPIS), which maps portions of the first Galactic quadrant with an angular resolution, sensitivity and dynamic range that surpasses existing radio images of the Milky Way by more than an order of magnitude. The source detection threshold at 20 cm is in the range 1-2 mJy over the 85% of the survey region (5{sup o} < l < 32{sup o}, |b| < 0.8{sup o}) not covered by bright extended emission; the angular resolution is {approx} 6''. We catalog over 3000 discrete sources (diameters mostly < 30'') and present an atlas of {approx} 400 diffuse emission regions. New and archival data at 90 cm for the whole survey area are also presented. Comparison of our catalogs and images with the MSX mid-infrared data allow us to provide preliminary discrimination between thermal and non-thermal sources. We identify 49 high-probability supernova remnant candidates, increasing by a factor of seven the number of known remnants with diameters smaller than 50 in the survey region; several are pulsar wind nebula candidates and/or very small diameter remnants (D < 45''). We report the tentative identification of several hundred H II regions based on a comparison with the mid-IR data; they range in size from unresolved ultra-compact sources to large complexes of diffuse emission on scales of half a degree. In several of the latter regions, cospatial nonthermal emission illustrates the interplay between stellar death and birth. We comment briefly on plans for followup observations and our extension of the survey; when complemented by data from ongoing X-ray and mid-IR observations, we expect MAGPIS to provide an important contribution to our understanding of the birth and death of massive stars in the Milky Way.
- Published
- 2006
23. FR II Broad Absorption Line Quasars and the Life Cycle of Quasars
- Author
-
Michael D. Gregg, Robert H. Becker, and Willem de Vries
- Subjects
Physics ,Absorption spectroscopy ,Large quasar group ,media_common.quotation_subject ,Astronomy ,Astronomy and Astrophysics ,Digitized Sky Survey ,Quasar ,Astrophysics ,Spectral line ,Space and Planetary Science ,Sky ,Absorption (electromagnetic radiation) ,OVV quasar ,media_common - Abstract
By combining the Sloan Digitized Sky Survey Third Data Release quasar list with the VLA FIRST survey, we have identified five objects having both broad absorption lines in their optical spectra and FR-II radio morphologies. We identify an additional example of this class from the FIRST Bright Quasar Survey, J1408+3054. Including the original FR-II-BAL object, J1016+5209, brings the number of such objects to eight. These quasars are relatively rare; finding this small handful has required the 45,000-large quasar sample of SDSS. The FR-II-BAL quasars exhibit a significant anti-correlation between radio-loudness and the strength of the BAL features. This is easily accounted for by the evolutionary picture in which quasars emerge from cocoons of BAL-producing material which stifle the development of radio jets and lobes. There is no such simple explanation for the observed properties of FR-II-BALs in the unification-by-orientation model of quasars. The rarity of the FR-II-BAL class implies that the two phases do not coexist for very long in a single quasar, perhaps less than 10{sup 5} years, with the combined FR-II, high ionization broad absorption phase being even shorter by another factor of 10 or more.
- Published
- 2006
24. A Survey ofz > 5.7 Quasars in the Sloan Digital Sky Survey. IV. Discovery of Seven Additional Quasars
- Author
-
Aleksandar M. Diamond-Stanic, Richard L. White, Scot Kleinman, J. Brinkmann, Stephanie A. Snedden, Eric H. Neilsen, J. Serena Kim, Atsuko Nitta, Marianne Vestergaard, Gillian R. Knapp, Xiaohui Fan, Wolfgang Voges, Michael A. Strauss, Robert H. Lupton, Michael Harvanek, Masataka Fukugita, Jennifer L. Donley, James E. Gunn, Neta A. Bahcall, Jurek Krzesinski, J. C. Barentine, Robert H. Becker, Joseph F. Hennawi, Gordon T. Richards, Jason E. Young, Dan Long, Donald P. Schneider, Howard Brewington, Linhua Jiang, and W. N. Brandt
- Subjects
Physics ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Type (model theory) ,01 natural sciences ,Galaxy ,Redshift ,13. Climate action ,Space and Planetary Science ,Sky ,0103 physical sciences ,Emission spectrum ,010303 astronomy & astrophysics ,Equivalent width ,Astrophysics::Galaxy Astrophysics ,BL Lac object ,media_common - Abstract
We present the discovery of seven quasars at z>5.7, selected from ~2000 deg^2 of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two have larger photometric errors and are not part of the complete sample. One of the new quasars, SDSS J1335+3533 (z=5.93), exhibits no emission lines; the 3-sigma limit on the rest-frame equivalent width of Ly alpha+NV line is 5 A. It is the highest redshift lineless quasar known, and could be a gravitational lensed galaxy, a BL Lac object or a new type of quasar. Two new z>6 quasars, SDSS 1250+3130 (z=6.13) and SDSS J1137+3549 (z=6.01), show deep Gunn-Peterson absorption gaps in Ly alpha. These gaps are narrower the complete Gunn-Peterson absorption troughs observed among quasars at z>6.2 and do not have complete Ly beta absorption., Comment: AJ in press, 16 pages, 3 figures
- Published
- 2006
25. SDSS J024634.11-082536.2: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
- Author
-
Naohisa Inada, Daniel J. Eisenstein, Masamune Oguri, Alexander S. Szalay, Richard L. White, Robert H. Becker, Donald G. York, Michael D. Gregg, Scott Burles, Patrick B. Hall, J. Brinkmann, Bartosz Pindor, David Johnston, Francisco J. Castander, Gordon T. Richards, Paul L. Schechter, and Donald P. Schneider
- Subjects
Absolute magnitude ,Physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Redshift ,law.invention ,Telescope ,Apparent magnitude ,Space and Planetary Science ,Sky ,Observatory ,law ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium's Walter Baade 6.5-m telescope and the spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images ($\Delta{\theta}=$1\farcs04) of a source quasar at z=1.68. Imaging observations with the Keck telescope and the Hubble Space Telescope reveal an extended object between the two quasar components, which is likely to be a lensing galaxy of this system. From the absorption lines in the spectra of quasar components and the apparent magnitude of the galaxy, combined with the expected absolute magnitude from the Faber-Jackson relation, we estimate the redshift of the lensing galaxy to be z=0.724. A highly distorted ring is visible in the Hubble Space Telescope images, which is likely to be the lensed host galaxy of the source quasar. Simple mass modeling predicts the possibility that there is a small (faint) lensing object near the primary lensing galaxy.
- Published
- 2005
26. ChandraX-Ray Observations of Radio-Loud Broad Absorption Line Quasars
- Author
-
Robert H. Becker, Zhaohui Shang, Michael D. Gregg, Gisela Telis, R. L. White, Sally A. Laurent-Muehleisen, and Michael S. Brotherton
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,X-ray ,Spectral density ,Astronomy ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Spectral line ,Space and Planetary Science ,Observatory ,Absorption (electromagnetic radiation) ,Astrophysics::Galaxy Astrophysics - Abstract
We report the results of a Chandra X-Ray Observatory survey of five formally radio-loud broad absorption line (BAL) quasars. These five objects include BAL quasars with a range of properties, including both high- and low-ionization BALs. All five BAL quasars are detected in 5 ks ACIS-S exposures, with counts ranging from 12 to 55. The X-ray count rates are down by factors of 40 or more compared to expectations based on the spectral energy distributions of normal, unabsorbed radio-loud quasars; this is the same sort of behavior seen in radio-quiet BAL quasars. Interestingly, the hardness ratios are rather soft and inconsistent with absorption from a neutral hydrogen column density large enough to suppress the X-rays as observed. We conclude that in many cases the X-rays emanating from BAL quasars must be reflected, scattered, or leaked through an ionized absorber or a neutral absorber that does not completely cover the X-ray source (covering ≥98%), or that we are seeing an unabsorbed X-ray source perhaps associated with a radio jet. Much higher counts are required to distinguish among these possibilities. We note several suggestive correlations involving X-ray properties that require verification using larger samples. One source, FIRST J1556+3517, appears to be the X-ray brightest low-ionization BAL quasar known, other than the special case of the nearby Mrk 231. The very faint X-ray emission from FIRST J1044+3656 is consistent with significant obscuration, which strongly favors the multiphase X-ray shielding models of this object in the literature.
- Published
- 2005
27. New Catalogs of Compact Radio Sources in the Galactic Plane
- Author
-
Robert H. Becker, David J. Helfand, and Richard L. White
- Subjects
Very large array ,Physics ,Milky Way ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Astrometry ,Galactic plane ,Latitude ,Space and Planetary Science ,Angular resolution ,Longitude - Abstract
Archival data have been combined with recent observations of the Galactic plane using the Very Large Array to create new catalogs of compact centimetric radio sources. The 20 cm source catalog covers a longitude range of -20 deg < l < 120 deg; the latitude coverage varies from +- 0.8 deg to +- 2.7 deg. The total survey area is ~331 sq deg; coverage is 90% complete at a flux density threshold of ~14 mJy, and over 5000 sources are recorded. The 6 cm catalog covers 43 sq deg in the region -10 deg < l < 42 deg, |b| < 0.4 deg to a 90% completeness threshold of 2.9 mJy; over 2700 sources are found. Both surveys have an angular resolution of ~6 arcsec. These catalogs provide a 30% (at 20 cm) to 50% (at 6 cm) increase in the number of high-reliability compact sources in the Galactic plane, as well as providing greatly improved astrometry, uniformity, and reliability; they should prove useful for comparison with new mid- and far-infrared surveys of the Milky Way., 14 pages, 7 figures, 6 tables; accepted for August 2005 Astronomical Journal; numerous minor revisions in paper and catalogs from first version
- Published
- 2005
28. Hubble Space TelescopeAdvanced Camera for Surveys Observations of thez= 6.42 Quasar SDSS J1148+5251: A Leak in the Gunn-Peterson Trough
- Author
-
Xiaohui Fan, Michael A. Strauss, Robert H. Becker, and Richard L. White
- Subjects
Physics ,Gravitational lens ,Space and Planetary Science ,Optical depth (astrophysics) ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Spectral resolution ,Gunn–Peterson trough ,Advanced Camera for Surveys ,Galaxy ,Redshift - Abstract
The Hubble Advanced Camera for Surveys has been used to obtain a narrow-band image of the weak emission peak seen at lambda=7205 A in the Gunn-Peterson Ly beta absorption trough of the highest redshift quasar, SDSS J1148+5251. The emission looks perfectly point-like; there is no evidence for the intervening galaxy that we previously suggested might be contaminating the quasar spectrum. We derive a more accurate astrometric position for the quasar in the two filters and see no indication of gravitational lensing. We conclude that the light in the Ly beta trough is leaking through two unusually transparent, overlapping windows in the IGM absorption, one in the Ly beta forest at z ~ 6 and one in the Ly alpha forest at z ~ 5. If there are significant optical depth variations on velocity scales small compared with our spectral resolution (~150 km/s), the Ly alpha trough becomes more transparent for a given Ly beta optical depth. Such variations can only strengthen our conclusion that the fraction of neutral hydrogen in the IGM increases dramatically at z>6. We argue that the transmission in the Ly beta trough is not only a more sensitive measure of the neutral fraction than is Ly alpha, it also provides a less biased estimator of the neutral hydrogen fraction than does the Ly alpha transmission.
- Published
- 2005
29. Discovery of Two Gravitationally Lensed Quasars with Image Separations of 3″ from the Sloan Digital Sky Survey
- Author
-
Jonathan Brinkmann, Bartosz Pindor, Robert H. Becker, Masamune Oguri, Neta A. Bahcall, Hans-Walter Rix, Robert J. Brunner, Michael A. Strauss, Joshua A. Frieman, Gordon T. Richards, Michael D. Gregg, Patrick B. Hall, Joseph F. Hennawi, David Johnston, Francisco J. Castander, Naohisa Inada, Donald G. York, and Donald P. Schneider
- Subjects
Physics ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Cosmology ,Galaxy ,Spectral line ,Redshift ,law.invention ,Gravitation ,Lens (optics) ,Space and Planetary Science ,law ,Sky ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discovery of two doubly-imaged quasars, SDSS J100128.61+502756.9 and SDSS J120629.65+433217.6, at redshifts of 1.838 and 1.789 and with image separations of 2.86'' and 2.90'', respectively. The objects were selected as lens candidates from the Sloan Digital Sky Survey (SDSS). Based on the identical nature of the spectra of the two quasars in each pair and the identification of the lens galaxies, we conclude that the objects are gravitational lenses. The lenses are complicated; in both systems there are several galaxies in the fields very close to the quasars, in addition to the lens galaxies themselves. The lens modeling implies that these nearby galaxies contribute significantly to the lens potentials. On larger scales, we have detected an enhancement in the galaxy density near SDSS J100128.61+502756.9. The number of lenses with image separation of ~3'' in the SDSS already exceeds the prediction of simple theoretical models based on the standard Lambda-dominated cosmology and observed velocity function of galaxies., Comment: 24 pages, 9 figures, accepted for publication in ApJ
- Published
- 2005
30. Imaging and Spectroscopy of Galaxies Associated with Twoz~0.7 Damped Ly Absorption Systems
- Author
-
Michael D. Gregg, Robert H. Becker, Lisa J. Storrie-Lombardi, Mark Lacy, Richard L. White, and Tanya Urrutia
- Subjects
Physics ,education.field_of_study ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Population ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Galaxy ,Luminosity ,Stars ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Spectroscopy ,education ,Astrophysics::Galaxy Astrophysics ,Luminosity function (astronomy) - Abstract
We have identified galaxies near two quasars which are at the redshift of damped Lyman-alpha (DLA) systems in the UV spectra of the quasars. Both galaxies are actively forming stars. One galaxy has a luminosity close to the break in the local galaxy luminosity function, L*, the other is significantly fainter than L* and appears to be interacting with a nearby companion. Despite the strong selection effects favoring spectroscopic identification of the most luminous DLA galaxies, many of the spectroscopically-identified DLA galaxies in the literature are sub-L*, suggesting that the majority of the DLA population is probably sub-L*, in contrast to MgII absorbers at similar redshifts whose mean luminosity is close to L*., Comment: 9 pages, to appear in AJ, November 2003 issue
- Published
- 2003
31. SDSS J090334.92+502819.2: A New Gravitational Lens
- Author
-
Mariangela Bernardi, Eric T. Johnson, Neta A. Bahcall, Donald P. Schneider, Joshua A. Frieman, Bartosz Pindor, Gordon T. Richards, Ryan Scranton, Patrick B. Hall, Donald G. York, Charles R. Keeton, David Johnston, Daniel J. Eisenstein, Mark SubbaRao, Jon Brinkmann, Richard L. White, Michael A. Strauss, Alexander S. Szalay, Masataka Fukugita, David J. Schlegel, Naohisa Inada, Robert H. Becker, Gillian R. Knapp, Erin S. Sheldon, and Zhaoming Ma
- Subjects
Physics ,Simple lens ,010308 nuclear & particles physics ,media_common.quotation_subject ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Galaxy ,Redshift ,law.invention ,Lens (optics) ,Telescope ,Gravitational lens ,Space and Planetary Science ,law ,Sky ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J090334.92+502819.2. This object was targeted for SDSS spectroscopy as a Luminous Red Galaxy (LRG), but manual examination of the spectrum showed the presence of a quasar at z= 3.6 in addition to a red galaxy at z=0.388, and the SDSS image showed a second possible quasar image nearby. Follow-up imaging and spectroscopy confirmed the lensing hypothesis. In images taken at the ARC 3.5-meter telescope, two quasars are separated by 2.8 arc-seconds; the lensing galaxy is clearly seen and is blended with one of the quasar images. Spectroscopy taken at the Keck II telescope shows that the quasars have identical redshifts of z=3.6 and both show the presence of the same broad absorption line-like troughs. We present simple lens models which account for the geometry and magnifications. The lens galaxy lies near two groups of galaxies and may be a part of them. The models suggest that the groups may contribute considerable shear and may have a strong effect on the lens configuration.
- Published
- 2003
32. Long-Term Variability of Sloan Digital Sky Survey Quasars
- Author
-
R. L. White, W. H. de Vries, and Robert H. Becker
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Structure function ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Light curve ,Photometry (optics) ,Space and Planetary Science ,Sky ,Data release ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We use a sample of 3791 quasars from the Sloan Digital Sky Survey (SDSS) Early Data Release and compare their photometry with historic plate material for the same set of quasars in order to study their variability properties. The time baseline we attain this way ranges from a few months to up to 50 yr. In contrast to monitoring programs, where relatively few quasars are photometrically measured over shorter time periods, we use existing databases to extend this baseline as much as possible, at the cost of sampling per quasar. Our method, however, can easily be extended to much larger samples. We construct variability structure functions and compare these with the literature and model functions. From our modeling, we conclude that (1) quasars are more variable toward shorter wavelengths, (2) their variability is consistent with an exponentially decaying light curve with a typical timescale of ~2 yr, and (3) these outbursts occur on typical timescales of ~200 yr. With the upcoming first data release of the SDSS, a much larger quasar sample can be used to put these conclusions on a more secure footing.
- Published
- 2003
33. SDSS J092455.87+021924.9: An Interesting Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
- Author
-
Francisco J. Castander, Scott Burles, Peter R. Newman, Eric H. Neilsen, David E. Johnston, Paul L. Schechter, Robert H. Becker, Gordon T. Richards, Bartosz Pindor, Naohisa Inada, Scot Kleinman, Stephanie A. Snedden, Maki Sekiguchi, Jurek Krzesinski, J. Brinkmann, Richard L. White, Daniel J. Eisenstein, Atsuko Nitta, Donald P. Schneider, Donald G. York, Dan Long, Joshua A. Frieman, and Patrick B. Hall
- Subjects
Physics ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Galaxy ,law.invention ,Telescope ,Lens (optics) ,Gravitational lens ,Space and Planetary Science ,Observatory ,law ,Sky ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was selected from among known SDSS quasars by an algorithm that was designed to select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate components, three of which are unresolved, are identified in photometric follow-up observations obtained with the Magellan Consortium's 6.5m Walter Baade telescope at Las Campanas Observatory. Two of the unresolved components (designated A and B) are confirmed to be quasars with z=1.524; the velocity difference is less than 100 km sec^{-1} according to spectra taken with the W. M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar component, designated C, has the colors of a quasar with redshift similar to components A and B. The maximum separation of the point sources is 1.78". The other two sources, designated G and D, are resolved. Component G appears to be the best candidate for the lensing galaxy. Although component D is near the expected position of the fourth lensed component in a four image lens system, its properties are not consistent with being the image of a quasar at z~1.5. Nevertheless, the identical redshifts of components A and B and the presence of component C strongly suggest that this object is a gravitational lens. Our observations support the idea that a foreground object reddens the fourth lensed component and that another unmodeled effect (such as micro- or milli-lensing) demagnificates it, but we cannot rule out the possibility that SDSS0924+0219 is an example of the relatively rare class of ``three component'' lens systems., 24 pages, 6 figures, accepted by AJ
- Published
- 2003
34. AnI-Band-selected Sample of Radio-emitting Quasars: Evidence for a Large Population of Red Quasars
- Author
-
William R. Oegerle, Michael D. Gregg, Tod R. Lauer, Richard L. White, Marc Postman, David J. Helfand, and Robert H. Becker
- Subjects
Physics ,I band ,education.field_of_study ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Population ,Extinction (astronomy) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Spectral line ,Luminosity ,Space and Planetary Science ,Magnitude (astronomy) ,Astrophysics::Solar and Stellar Astrophysics ,education ,Astrophysics::Galaxy Astrophysics - Abstract
We present a new sample of 35 quasars selected from the FIRST radio survey and the Deeprange I-band survey (Postman et al. 1998, 2002). A comparison with the FIRST Bright Quasar survey samples reveals that this I-band selected sample is redder by 0.25-0.5 mag in B-R, and that the color difference is not explained by the higher mean redshift of this sample but must be intrinsic. Our small sample contains five quasars with unusually red colors, including three that appear very heavily reddened. Our data are fitted well with normal blue quasar spectra attenuated by more than 2.5 magnitudes of extinction in the I-band. The red quasars are only seen at low redshifts (z, 19 pages, 12 figures; submitted to the Astronomical Journal
- Published
- 2003
35. CTQ 327: A New Gravitational Lens
- Author
-
R. L. White, N. Morgan, José Maza, Paul L. Schechter, Robert H. Becker, Lutz Wisotzki, and Michael D. Gregg
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Gravitational microlensing ,Redshift ,Galaxy ,Stars ,Gravitational lens ,Space and Planetary Science ,Elliptical galaxy ,Astrophysics::Galaxy Astrophysics ,Space Telescope Imaging Spectrograph - Abstract
We present the second gravitationally lensed quasar discovered during the course of a Hubble Space Telescope Space Telescope Imaging Spectrograph snapshot survey for small-separation gravitational lenses. CTQ 327 is a double quasar with an image separation of 122 and a g-band flux ratio of roughly 5 to 1. Spectra reveal both components to be z = 1.37 quasars, and the lensing galaxy is clearly visible after point-spread function subtraction of the two quasar components. The light profile of the lensing galaxy is well modeled by an r1/4 law, indicative of an early-type elliptical galaxy. An estimate of the lens galaxy redshift is z ~ 0.4–0.6, based on the Faber-Jackson relationship and photometric considerations, although values outside this range are still consistent with the present data. Resolved spectra of the two quasars show similar, but not identical, continuum and emission-line features: component A exhibits weaker emission lines with respect to the continuum than does component B, and there is evidence of intrinsic differences in the emission-line profiles between the two components. Optical monitoring of the quasar pair also shows a change in the g-band flux ratio of 0.14 mag over a 3 month period. These spectral and photometric differences may be due to microlensing fluctuations from stars in the lensing galaxy, intrinsic quasar variability coupled with the system's differential time delay, or some combination of the two. The observed variability makes CTQ 327 an attractive target for future flux monitoring, aimed at time-delay or microlensing studies.
- Published
- 2003
36. A Survey of [CLC][ITAL]z[/ITAL][/CLC] ] 5.7 Quasars in the Sloan Digital Sky Survey. II. Discovery of Three Additional Quasars at [CLC][ITAL]z[/ITAL][/CLC] ] 6
- Author
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Xiaohui Fan, Michael A. Strauss, Donald P. Schneider, Robert H. Becker, Richard L. White, Zoltán Haiman, Michael Gregg, Laura Pentericci, Eva K. Grebel, Vijay K. Narayanan, Yeong-Shang Loh, Gordon T. Richards, James E. Gunn, Robert H. Lupton, Gillian R. Knapp, Željko Ivezić, W. N. Brandt, Matthew Collinge, Lei Hao, Daniel Harbeck, Francisco Prada, Joop Schaye, Iskra Strateva, Nadia Zakamska, Scott Anderson, Jon Brinkmann, Neta A. Bahcall, Don Q. Lamb, Sadanori Okamura, Alex Szalay, and Donald G. York
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Imaging data ,Spectral line ,Redshift ,Luminosity ,Space and Planetary Science ,Sky ,Alpha decay ,Astrophysics::Galaxy Astrophysics ,media_common ,Luminosity function (astronomy) - Abstract
We present the discovery of three new quasars at z>6 in 1300 deg^2 of SDSS imaging data, J114816.64+525150.3 (z=6.43), J104845.05+463718.3 (z=6.23) and J163033.90+401209.6 (z=6.05). The first two objects have weak Ly alpha emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to 0.05 and could be affected by the presence of broad absorption line systems. The last object has a Ly alpha strength more typical of lower redshift quasars. Based on a sample of six quasars at z>5.7 that cover 2870 deg^2 presented in this paper and in Paper I, we estimate the comoving density of luminous quasars at z 6 and M_{1450} 5.7 quasars and high-resolution ground-based images (seeing 0.4'') of three additional z>5.7 quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshfit quasar sample suggests the bright end slope of the quasar luminosity function at z 6 is shallower than Psi L^{-3.5} (2-sigma), consistent with the absence of strongly lensed objects.
- Published
- 2003
37. Optical and Radio Properties of Extragalactic Sources Observed by the FIRST Survey and the Sloan Digital Sky Survey
- Author
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Željko Ivezić, Kristen Menou, Gillian R. Knapp, Michael A. Strauss, Robert H. Lupton, Daniel E. Vanden Berk, Gordon T. Richards, Christy Tremonti, Michael A. Weinstein, Scott Anderson, Neta A. Bahcall, Robert H. Becker, Mariangela Bernardi, Michael Blanton, Daniel Eisenstein, Xiaohui Fan, Douglas Finkbeiner, Kristian Finlator, Joshua Frieman, James E. Gunn, Pat B. Hall, Rita S. J. Kim, Ali Kinkhabwala, Vijay K. Narayanan, Constance M. Rockosi, David Schlegel, Donald P. Schneider, Iskra Strateva, Mark SubbaRao, Aniruddha R. Thakar, Wolfgang Voges, Richard L. White, Brian Yanny, Jonathan Brinkmann, Mamoru Doi, Masataka Fukugita, Gregory S. Hennessy, Jeffrey A. Munn, Robert C. Nichol, and Donald G. York
- Subjects
Physics ,010308 nuclear & particles physics ,Radio galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Galaxy ,Redshift ,Luminosity ,Stars ,13. Climate action ,Space and Planetary Science ,Sky ,0103 physical sciences ,Magnitude (astronomy) ,Astrophysics::Solar and Stellar Astrophysics ,10. No inequality ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We discuss the optical and radio properties of 30,000 FIRST sources positionally associated with an SDSS source in 1230 deg$^2$ of sky. The majority (83%) of the FIRST sources identified with an SDSS source brighter than r=21 are optically resolved. We estimate an upper limit of 5% for the fraction of quasars with broad-band optical colors indistinguishable from those of stars. The distribution of quasars in the radio flux -- optical flux plane supports the existence of the "quasar radio-dichotomy"; 8% of all quasars with i
- Published
- 2002
38. The Twice-Overlooked, Second Fanaroff-Riley II Broad Absorption Line Quasar LBQS 1138−0126
- Author
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Carlos De Breuck, Scott M. Croom, Robert H. Becker, Michael S. Brotherton, and Michael D. Gregg
- Subjects
Physics ,Absorption spectroscopy ,Space and Planetary Science ,Astronomy and Astrophysics ,Optical polarization ,Quasar ,Angstrom ,Astrophysics ,Position angle ,Polarization (waves) ,Spectral line - Abstract
We report the correct classification of an overlooked Fanaroff-Riley class II radio-loud quasar with broad absorption lines, only the second such object so identified. The rare properties of this quasar, LBQS 1138-0126, are twice overlooked. First LBQS 1138-0126 was found in the Large Bright Quasar Survey but only noted as a possible broad absorption line quasar without additional follow-up. Later LBQS 1138-0126 was rediscovered and classified as a radio-loud broad absorption line quasar but not recognized as an FR II radio source. We describe the radio, absorption line, and optical polarization properties of LBQS 1138-0126 and place it in context with respect to related quasars. In particular, spectropolarimetry shows that LBQS 1138-0126 has high continuum polarization increasing from 3% in the red (rest-frame 2400 Angstroms) to over 4% in the blue (rest-frame 1650 Ansgtroms), essentially confirming the intrinsic nature of the absorption. The polarization position angle rotates from about -30 degrees in the red to about 0 degrees in the blue; the radio lobe position angle is 52 degrees for comparison. LBQS 1138-0126 is additionally notable for being one of the most radio-loud broad absorption line quasars, and for having low-ionization broad absorption lines as well.
- Published
- 2002
39. An F[CLC]e[/CLC]L[CLC]o[/CLC]BAL Binary Quasar
- Author
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Xiaohui Fan, Robert H. Becker, F. H. Chaffee, Gordon T. Richards, Richard L. White, and Michael D. Gregg
- Subjects
Physics ,Infrared ,Astrophysics::High Energy Astrophysical Phenomena ,Continuum (design consultancy) ,Astrophysics::Instrumentation and Methods for Astrophysics ,Binary number ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Spectral line ,Space and Planetary Science ,Observatory ,Emission spectrum ,Astrophysics::Galaxy Astrophysics - Abstract
In an ongoing infrared imaging survey of quasars at Keck Observatory, we have discovered that the z=1.285 quasar SDSS J233646.2-010732.6 comprises two point sources with a separation of 1.67". Resolved spectra show that one component is a standard quasar with a blue continuum and broad emission lines; the other is a broad absorption line (BAL) quasar, specifically, a BAL QSO with prominent absorption from MgII and metastable FeII, making it a member of the ``FeLoBAL'' class. The number of known FeLoBALs has recently grown dramatically from a single example to more than a dozen, including a gravitationally lensed example and the binary member presented here, suggesting that this formerly rare object may be fairly common. Additionally, the presence of this BAL quasar in a relatively small separation binary adds to the growing evidence that the BAL phenomenon is not due to viewing a normal quasar at a specific orientation, but rather that it is an evolutionary phase in the life of many, if not all, quasars, and is particularly associated with conditions found in interacting systems.
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- 2002
40. The Reddest Quasars. II. A Gravitationally Lensed [CLC]FeLoBAL[/CLC] Quasar
- Author
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Robert H. Becker, David J. Helfand, Mark Lacy, Eilat Glikman, Richard L. White, Joshua N. Winn, and Michael D. Gregg
- Subjects
Physics ,education.field_of_study ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Redshift ,Spectral line ,Black hole ,symbols.namesake ,Space and Planetary Science ,Eddington luminosity ,Elliptical galaxy ,symbols ,Astrophysics::Solar and Stellar Astrophysics ,education ,Astrophysics::Galaxy Astrophysics - Abstract
We report the discovery of a z=2.65 low-ionization iron broad absorption line quasar, FIRST J100424.9+122922, which is gravitationally-lensed by a galaxy at z~0.95. The object was discovered as part of a program to find very red quasars by matching the FIRST radio survey with the 2-MASS near-infrared survey. J100424.9+122922 is the second lensed system to be found in this program, suggesting that many gravitational lenses are probably missed from conventional optical quasar surveys. We have made a simple lens model and a rough estimate of the reddening in the immediate environment of the quasar which suggests that the quasar is intrinsically very luminous and is accreting at close to the Eddington limit of its ~10^9 M_sun black hole. The lensing galaxy has a small amount of dust which is responsible for some excess reddening observed in the fainter image of the quasar, but is otherwise a fairly typical massive elliptical galaxy. We model the selection effects working against the detection of red quasars in both lensed and unlensed samples. We show that these selection effects are very effective at removing even lightly-reddened high redshift quasars from magnitude-limited samples, whether they are lensed or not. This suggests that the red quasar population in general could be very large, and in particular the class of iron broad absorption line quasars of which J100424.9+122922 is a member may be much larger than their rarity in magnitude-limited samples would suggest.
- Published
- 2002
41. Keck HIRES Spectroscopy of the Fe<scp>ii</scp>Low‐Ionization Broad Absorption Line Quasar FBQS 0840+3633: Evidence for Two Outflows on Different Scales
- Author
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Robert H. Becker, Nahum Arav, Richard L. White, Michael D. Gregg, and Martijn de Kool
- Subjects
Physics ,Electron density ,Absorption spectroscopy ,Space and Planetary Science ,Excited state ,Ionization ,Astronomy and Astrophysics ,Quasar ,Atomic physics ,Spectroscopy ,Collisional excitation ,Spectral line - Abstract
A Keck echelle spectrum of the quasar FBQS 0840+3633 reveals outflowing gas that gives rise to blueshifted absorption lines of many low-ionization species. The gas covers a range of velocities from -700 to -3500 km s-1, with two main components centered at -900 and -2800 km s-1. The physical conditions in the two main velocity components are found to be significantly different and can be attributed to a difference of a factor of ~100 in the distance from the central continuum source. The low-velocity gas shows absorption lines from excited states with relative strengths that indicate a low density. The level populations of low-lying Ni II, Si II, and Fe II states cannot be explained with a model based on collisional excitation and a single electron density. The lines of Si II provide an upper limit on the electron density of ne < 500 cm-3, and another excitation mechanism must be responsible for the observed excitation of Fe II and Ni II. Assuming that this mechanism is UV fluorescence leads to an estimate of the distance between the low-velocity gas and the active nucleus of ~230 pc. Absorption lines from excited states formed in the high-velocity gas indicate a much higher density. This gas gives rise to Fe III and strong Al III absorption, which indicates that it contains the hydrogen ionization front on our line of sight to the active nucleus. The observed Fe III and Al III column densities and the absence of detectable absorption from the He I 23S state allow us to derive an estimate of the typical distance between the high-velocity gas and the active nucleus of ~1 pc.
- Published
- 2002
42. Kinetics and Mechanisms of the Ozone/Bromite and Ozone/Chlorite Reactions
- Author
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Jeffrey S. Nicoson, Lu Wang, Robert H. Becker, Dale W. Margerum, Charles E. Muller, and Kara E. Huff Hartz
- Subjects
Inorganic Chemistry ,chemistry.chemical_compound ,Electron transfer ,Ozone ,Reaction rate constant ,chemistry ,Kinetics ,Disproportionation ,Physical and Theoretical Chemistry ,Bromine dioxide ,Kinetic energy ,Photochemistry ,Spectroscopy - Abstract
Ozone reactions with XO(2)(-) (X = Cl or Br) are studied by stopped-flow spectroscopy under pseudo-first-order conditions with excess XO(2)(-). The O(3)/XO(2)(-) reactions are first-order in [O(3)] and [XO(2)(-)], with rate constants k(1)(Cl) = 8.2(4) x 10(6) M(-1) s(-1) and k(1)(Br) = 8.9(3) x 10(4) M(-1) s(-1) at 25.0 degrees C and mu = 1.0 M. The proposed rate-determining step is an electron transfer from XO(2)(-) to O(3) to form XO(2) and O(3)(-). Subsequent rapid reactions of O(3)(-) with general acids produce O(2) and OH. The OH radical reacts rapidly with XO(2)(-) to form a second XO(2) and OH(-). In the O(3)/ClO(2)(-) reaction, ClO(2) and ClO(3)(-) are the final products due to competition between the OH/ClO(2)(-) reaction to form ClO(2) and the OH/ClO(2) reaction to form ClO(3)(-). Unlike ClO(2), BrO(2) is not a stable product due to its rapid disproportionation to form BrO(2)(-) and BrO(3)(-). However, kinetic spectra show that small but observable concentrations of BrO(2) form within the dead time of the stopped-flow instrument. Bromine dioxide is a transitory intermediate, and its observed rate of decay is equal to half the rate of the O(3)/BrO(2)(-) reaction. Ion chromatographic analysis shows that O(3) and BrO(2)(-) react in a 1/1 ratio to form BrO(3)(-) as the final product. Variation of k(1)(X) values with temperature gives Delta H(++)(Cl) = 29(2) kJ mol(-1), DeltaS(++)(Cl) = -14.6(7) J mol(-1) K(-1), Delta H(++)(Br) = 54.9(8) kJ mol(-1), and Delta S(++)(Br) = 34(3) J mol(-1) K(-1). The positive Delta S(++)(Br) value is attributed to the loss of coordinated H(2)O from BrO(2)(-) upon formation of an [O(3)BrO(2)(-)](++) activated complex.
- Published
- 2002
43. Intrinsic Absorption in the QSO FIRST J121442.3+280329
- Author
-
Martijn de Kool, Robert H. Becker, Richard L. White, Nahum Arav, and Michael D. Gregg
- Subjects
Physics ,Line-of-sight ,Absorption spectroscopy ,Space and Planetary Science ,Ionization ,Excited state ,Astronomy and Astrophysics ,Quasar ,Outflow ,Astrophysics ,Excitation temperature ,Spectral line - Abstract
This paper presents an analysis of a Keck HIRES spectrum of the QSO FIRST J121442.3+280329, covering the rest wavelength range from 2300 to 3500 A. The line of sight toward this quasar (QSO) contains an outflow giving rise to many blueshifted absorption lines. The outflow consists of material with a continuous range of velocities from -1200 to -2800 km s-1. Significant substructure is present in the absorption line profiles. The spectrum is dominated by absorption lines of Mg II and the singly ionized iron group elements Fe II, Cr II, and Mn II, including absorption lines from excited levels with energies above 30,000 cm-1 (~4 eV).We derive constraints on the physical conditions in the outflow by fitting a model to the observed spectrum that simultaneously optimizes the values for the column densities of all species, the excitation temperature, the shape of the unabsorbed continuum, and the covering factor. By comparing these constraints with ionization models, we conclude that the ionization parameter, density, and column density of the outflow is characterized by -2.0 < log U < -0.7, 7.5 < log nH < 9.5, and 21.4 < log NH < 22.2. These values place the absorbing outflow at a distance between 1 and 30 pc from the QSO core.
- Published
- 2002
44. Pulsed-accelerated-flow studies of the temperature dependence of fast reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany
- Author
-
Wenzel P. Bartlett, Dale W. Margerum, Robert H. Becker, and Edward T. Urbansky
- Subjects
Reaction rate ,Distribution system ,Chemical kinetics ,Hydrolysis ,Reaction rate constant ,Bromine ,Chemistry ,Flow (psychology) ,Analytical chemistry ,Peek ,chemistry.chemical_element ,General Chemistry - Abstract
A pulsed-accelerated-flow (PAF) spectrometer (model V) capable of non-ambient temperature studies of fast reaction kinetics is described. The PAF method uses accelerated flow mixing of reactants during short time periods to enable the resolution of mixing and reaction rate constants. A new mixing/observation cell and cell supports are designed to permit measurement of reaction kinetics from 40 °C to below 0 °C. The cell consists of two machined PEEK [(–OC6H4OC6H4COC6H4–)n] pieces joined together to give an internal solution distribution system, which greatly reduces the number of connections needed compared to previous instruments to bring the reactants together. The reaction between W(CN)84− and IrCl62− in 0.50 M H2SO4 is studied at 0.0, 25.0, and 40.0 °C. Second-order rate constants of 0.650 × 108 M−1 s−1, 1.05 × 108 M−1 s−1, and 1.29 × 108 M−1 s−1 are obtained, respectively. These data give activation parameters of ΔH‡ = 10.0 ± 0.8 kJ mol−1 and ΔS‡ = −58 ± 3 J mol−1 K−1. Activation parameters for reverse bromine hydrolysis (HOBr + Br− + H+ → Br2 + H2O) were determined from rate constants measured from 0.0 to 40.0 °C. These were used to calculate the activation parameters for the forward bromine hydrolysis (ΔH‡ = 66 ± 1 kJ mol−1 and ΔS‡ = 10 ± 20 J mol−1 K−1). The temperature dependence of the extremely rapid BrCl hydrolysis reaction (in equilibrium with BrCl2−) is determined as well. For reactions at temperatures of 25.0 °C, 10.0 °C, and 0.0 °C the values are 3.3 × 106 s−1, 2.06 × 106 s−1, and 1.75 × 106 s−1, respectively. These values correspond to activation parameters of ΔH‡ = 15 ± 7 kJ mol−1 and ΔS± = −71 ± 24 J mol−1 K−1 for BrCl hydrolysis.
- Published
- 2002
45. The Reddest Quasars
- Author
-
Robert H. Becker, Mark Lacy, David J. Helfand, Richard L. White, Michael D. Gregg, Michael S. Brotherton, and Eilat Glikman
- Subjects
Physics ,education.field_of_study ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,Population ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Rest frame ,Galaxy ,Observational evidence ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Local environment ,Spectral energy distribution ,education ,Astrophysics::Galaxy Astrophysics - Abstract
In a survey of quasar candidates selected by matching the FIRST and 2MASS catalogs, we have found two extraordinarily red quasars. FIRST J013435.7-093102 is a 1 Jy source at z=2.216 and has B-K > 10, while FIRST J073820.1+275045 is a 2.5 mJy source at z=1.985 with B-K = 8.4. FIRST J073820.1+275045 has strong absorption lines of MgII and CIV in the rest frame of the quasar and is highly polarized in the rest frame ultraviolet, strongly favoring the interpretation that its red spectral energy distribution is caused by dust reddening local to the quasar. FIRST J073820.1+275045 is thus one of the few low radio-luminosity, highly dust-reddened quasars known. The available observational evidence for FIRST J013435.7-093102 leads us to conclude that it too is reddened by dust. We show that FIRST J013435.7-093102 is gravitationally lensed, increasing the number of known lensed, extremely dust-reddened quasars to at least three, including MG0414-0534 and PKS1830-211. We discuss the implications of whether these objects are reddened by dust in the host or lensing galaxies. If reddened by their local environment, then we estimate that between 10 and 20% of the radio-loud quasar population is reddened by dust in the host galaxy. The discovery of FIRST J073820.1+275045 and objects now emerging from X-ray surveys suggests the existence of an analogous radio-quiet red quasar population. Such objects will be entirely missed by standard radio or optical quasar surveys. If dust in the lensing galaxies is primarily responsible for the extreme redness of the lensed quasars, then an untold number of gravitationally lensed quasars are being overlooked., AASTEX 24 pp., 7 figs; accepted by ApJ. See also the preprint astro-ph/0107435 by Winn et al., who independently discovered that J013435.7-093102 is gravitationally lensed
- Published
- 2002
46. A Survey of [CLC][ITAL]z[/ITAL][/CLC] > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at [CLC][ITAL]z[/ITAL][/CLC] ∼ 6
- Author
-
Xiaohui Fan, Vijay K. Narayanan, Robert H. Lupton, Michael A. Strauss, Gillian R. Knapp, Robert H. Becker, Richard L. White, Laura Pentericci, S. K. Leggett, Zoltán Haiman, James E. Gunn, Željko Ivezić, Donald P. Schneider, Scott F. Anderson, J. Brinkmann, Neta A. Bahcall, Andrew J. Connolly, István Csabai, Mamoru Doi, Masataka Fukugita, Tom Geballe, Eva K. Grebel, Daniel Harbeck, Gregory Hennessy, Don Q. Lamb, Gajus Miknaitis, Jeffrey A. Munn, Robert Nichol, Sadanori Okamura, Jeffrey R. Pier, Francisco Prada, Gordon T. Richards, Alex Szalay, and Donald G. York
- Subjects
Physics ,010308 nuclear & particles physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Continuum (design consultancy) ,Flux ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,Omega ,Redshift ,Black hole ,Space and Planetary Science ,Sky ,0103 physical sciences ,Galaxy formation and evolution ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We present the results from a survey of i-dropout objects selected from ~1550 deg^2 of multicolor imaging data from the Sloan Digital Sky Survey, to search for luminous quasars at z>5.8. Objects with i*-z*>2.2 and z* 0.90. The ARC 3.5m spectrum of the z=6.28 quasar shows that over a range of 300 A immediately blueward of the Ly alpha emission, the average transmitted flux is only 0.003 +/-0.020 times that of the continuum level, consistent with zero flux, and suggesting a tentative detection of the complete Gunn-Peterson trough. The existence of strong metal lines suggests early chemical enrichment in the quasar enviornment. The three new objects, together with the previously published z=5.8 quasar form a complete color-selected flux-limited sample at z>5.8. We estimate that at $z=6$, the comoving density of luminous quasars at M_1450 < -26.89 (h=0.5, Omega=1)is 1.1x10^-9 Mpc^-3. This is a factor of ~2 lower than that at z~5, and is consistent with an extrapolation of the observed quasar evolution at low-z. We discuss the contribution of quasars to the ionizing background at z~6. The luminous quasars discussed in the paper have central black hole masses of several times 10^9 M_sun by the Eddington argument. Their observed space density provides a sensitive test of models of quasar and galaxy formation at high redshift. (Abridged)
- Published
- 2001
47. Evidence for Reionization at [ITAL][CLC]z[/CLC][/ITAL] ∼ 6: Detection of a Gunn-Peterson Trough in a [ITAL][CLC]z[/CLC][/ITAL] = 6.28 Quasar
- Author
-
Richard L. White, Neta A. Bahcall, Paul C. Czarapata, Gordon T. Richards, István Csabai, Timothy M. Heckman, J. Brinkmann, Anirudda R. Thakar, Robert H. Becker, James Annis, Alexander S. Szalay, Jeffrey R. Pier, Mamoru Doi, Gillian R. Knapp, A. J. Connolly, Xiaohui Fan, D. Q. Lamb, Gregory S. Hennessy, Robert H. Lupton, James E. Gunn, Zeljko Ivezic, Michael A. Strauss, Chris Stoughton, D. G. York, Jeffrey A. Munn, Robert C. Nichol, Thomas Nash, Timothy A. McKay, Donald P. Schneider, and Vijay K. Narayanan
- Subjects
Physics ,010308 nuclear & particles physics ,Continuum (design consultancy) ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Gunn–Peterson trough ,01 natural sciences ,Redshift ,Space and Planetary Science ,0103 physical sciences ,Optical depth (astrophysics) ,Alpha decay ,010303 astronomy & astrophysics ,Reionization ,Astrophysics::Galaxy Astrophysics ,Line (formation) - Abstract
We present moderate resolution Keck spectroscopy of quasars at z=5.82, 5.99 and 6.28, discovered by the Sloan Digital Sky Survey (SDSS). We find that the Ly Alpha absorption in the spectra of these quasars evolves strongly with redshift. To z~5.7, the Ly Alpha absorption evolves as expected from an extrapolation from lower redshifts. However, in the highest redshift object, SDSSp J103027.10+052455.0 (z=6.28), the average transmitted flux is 0.0038+-0.0026 times that of the continuum level over 8450 A 150, and is consistent with zero flux in the Ly Alpha forest region immediately blueward of the Ly Alpha emission line, compared with a drop by a factor of ~10 at z(abs)~5.3. A similar break is seen at Ly Beta; because of the decreased oscillator strength of this transition, this allows us to put a considerably stronger limit, tau(eff) > 20, on the optical depth to Ly Alpha absorption at z=6. This is a clear detection of a complete Gunn-Peterson trough, caused by neutral hydrogen in the intergalactic medium. Even a small neutral hydrogen fraction in the intergalactic medium would result in an undetectable flux in the Ly Alpha forest region. Therefore, the existence of the Gunn-Peterson trough by itself does not indicate that the quasar is observed prior to the reionization epoch. However, the fast evolution of the mean absorption in these high-redshift quasars suggests that the mean ionizing background along the line of sight to this quasar has declined significantly from z~5 to 6, and the universe is approaching the reionization epoch at z~6.
- Published
- 2001
48. The Intrinsic Absorber in QSO 2359−1241: Keck andHubble Space TelescopeObservations
- Author
-
Trevor Price, Robert H. Becker, Richard L. White, Michael D. Gregg, Nahum Arav, Michael S. Brotherton, and Warren Hack
- Subjects
Physics ,Hydrogen ,Absorption spectroscopy ,010308 nuclear & particles physics ,Magnesium ,chemistry.chemical_element ,Astronomy and Astrophysics ,Astrophysics ,Polarization (waves) ,01 natural sciences ,chemistry ,13. Climate action ,Space and Planetary Science ,Ionization ,Excited state ,0103 physical sciences ,Outflow ,010303 astronomy & astrophysics ,Helium - Abstract
We present detailed analyses of the absorption spectrum seen in QSO 2359-1241 (NVSS J235953-124148). Keck HIRES data reveal absorption from twenty transitions arising from: He I, Mg I, Mg II, Ca II, and Fe II. HST data show broad absorption lines (BALs) from Al III 1857, C IV 1549, Si IV 1397, and N V 1240. Absorption from excited Fe II states constrains the temperature of the absorber to 2000K < T < 10,000K and puts a lower limit of 10^5 cm^{-3} on the electron number density. Saturation diagnostics show that the real column densities of He I and Fe II can be determined, allowing to derive meaningful constraints on the ionization equilibrium and abundances in the flow. The ionization parameter is constrained by the iron, helium and magnesium data to -3.0 < log(U) < -2.5 and the observed column densities can be reproduced without assuming departure from solar abundances. From comparison of the He I and Fe II absorption features we infer that the outflow seen in QSO 2359-1241 is not shielded by a hydrogen ionization front and therefore that the existence of low-ionization species in the outflow (e.g., Mg II, Al III, Fe II) does not necessitate the existence of such a front. We find that the velocity width of the absorption systematically increases as a function of ionization and to a lesser extent with abundance. Complementary analyses of the radio and polarization properties of the object are discussed in a companion paper (Brotherton et al. 2000).
- Published
- 2001
49. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data. III. A Color-selected Sample at [ITAL][CLC]i[/CLC][/ITAL]* < 20 in the Fall Equatorial Stripe
- Author
-
Xiaohui Fan, Michael A. Strauss, Gordon T. Richards, Jeffrey A. Newman, Robert H. Becker, Donald P. Schneider, James E. Gunn, Marc Davis, Richard L. White, Robert H. Lupton, John E. Anderson, Jr., James Annis, Neta A. Bahcall, Robert J. Brunner, István Csabai, Mamoru Doi, Masataka Fukugita, G. S. Hennessy, Robert B. Hindsley, Željko Ivezić, Gillian R. Knapp, Timothy A. McKay, Jeffrey A. Munn, Jeffrey R. Pier, Alexander S. Szalay, and Donald G. York
- Subjects
Physics ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Celestial equator ,Continuum (design consultancy) ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Redshift ,Photometry (optics) ,Space and Planetary Science ,Sky ,Equivalent width ,Astrophysics::Galaxy Astrophysics ,Luminosity function ,media_common - Abstract
This is the third paper in a series aimed at finding high-redshift quasars from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by the SDSS during its commissioning phase. In this paper, we first present the observations of 14 bright high-redshift quasars (3.66
- Published
- 2001
50. Five High-Redshift Quasars Discovered in Commissioning Imaging Data of the Sloan Digital Sky Survey
- Author
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Wei Zheng, Zlatan I. Tsvetanov, Donald P. Schneider, Xiaohui Fan, Robert H. Becker, Marc Davis, Richard L. White, Michael A. Strauss, John E. Anderson, Jr., James Annis, Neta A. Bahcall, A. J. Connolly, István Csabai, Arthur F. Davidsen, Masataka Fukugita, James E. Gunn, Timothy M. Heckman, G. S. Hennessy, Željko Ivezić, G. R. Knapp, Robert H. Lupton, Eric Peng, Alexander S. Szalay, Aniruddha R. Thakar, Brian Yanny, and Donald G. York
- Subjects
Physics ,Infrared ,Astrophysics::High Energy Astrophysical Phenomena ,media_common.quotation_subject ,Astrophysics (astro-ph) ,Astrophysics::Instrumentation and Methods for Astrophysics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Quasar ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Imaging data ,Redshift ,Photometry (optics) ,Space and Planetary Science ,Sky ,Intergalactic medium ,Emission spectrum ,Astrophysics::Galaxy Astrophysics ,media_common - Abstract
We report the discovery of five quasars with redshifts of 4.67 - 5.27 and z'-band magnitudes of 19.5-20.7 M_B ~ -27. All were originally selected as distant quasar candidates in optical/near-infrared photometry from the Sloan Digital Sky Survey (SDSS), and most were confirmed as probable high-redshift quasars by supplementing the SDSS data with J and K measurements. The quasars possess strong, broad Lyman-alpha emission lines, with the characteristic sharp cutoff on the blue side produced by Lyman-alpha forest absorption. Three quasars contain strong, broad absorption features, and one of them exhibits very strong N V emission. The amount of absorption produced by the Lyman-alpha forest increases toward higher redshift, and that in the z=5.27 object (D_A ~ 0.7) is consistent with a smooth extrapolation of the absorption seen in lower redshift quasars. The high luminosity of these objects relative to most other known objects at z >~ 5 makes them potentially valuable as probes of early quasar properties and of the intervening intergalactic medium., 13 pages in LaTex format, two postscirpt figures. Submitted to the Astronomical Journal
- Published
- 2000
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