Search

Given the anisotropic emission from quasar accretion discs, their viewing angle affects estimates of the quasar luminosity, black-hole mass and Eddington ratio. Discs appear overluminous when viewed pole-on and underluminous when viewed at high inclination. In radio-quiet quasars, the viewing angle is usually unknown, although spectroscopic indicators have been proposed. Here, we use a recently discovered universality in the variability structure function (SF) of quasar light curves (LCs), where all quasars show the same SF when clocks run in units of orbital timescale. As an offset from the mean relation can be caused by incorrect orbital timescales and thus incorrect luminosities, we correlate these offsets with suggested inclination indicators. We derive SFs from NASA/ATLAS LCs spanning $\sim 6$ years of observation, using a sample of 183 luminous quasars with measured H$\beta$ lines as well as 753 quasars with CIV and MgII lines. Starting from the proposed orientation indicators, we expect quasars with narrower H$\beta$ lines and with more blueshifted CIV lines to be viewed more pole-on and thus appear overluminous. In contrast, our SF analysis finds that presumed pole-on discs appear underluminous, consistently for both line indicators. We discuss possible explanations for the behaviour of quasars with highly blueshifted CIV lines irrespective of inclination angle, including dusty outflows that might render the accretion disc underluminous and flatter disc temperature profiles with longer orbital timescales than in thin-disc models but reach no satisfying conclusion., Comment: 15 pages, 10 figures, Accepted for publication in MNRAS

The Kuiper belt objects, the Centaurs, and the Jupiter-family comets form an evolutionary continuum of small outer Solar System objects, and their study allows us to gain insight into the history and evolution of the Solar System. Broadband photometry can be used to measure their phase curves, allowing a first-order probe into the surface properties of these objects, though limited telescope time makes measuring accurate phase curves difficult. We make use of serendipitous broadband photometry from the long-baseline, high-cadence ATLAS survey to measure the phase curves for a sample of 18 Kuiper belt objects, Centaurs, and Jupiter-family comets with unprecedentedly large datasets. We find phase curves with previously reported negative slopes become positive with increased data and are thus due to insufficient sampling of the phase curve profile, and not a real physical effect. We search for correlations between phase curve parameters, finding no strong correlations between any parameter pair, consistent with the findings of previous studies. We search for instances of cometary activity in our sample, finding a previously reported outburst by Echeclus and a new epoch of increased activity by Chiron. Applying the main belt asteroid HG1G2 phase curve model to three Jupiter-family comets in our sample with large phase angle spans, we find their slope parameters imply surfaces more consistent with those of carbonaceous main belt asteroids than silicaceous ones., 42 pages, 24 figures, accepted for publication to the Planetary Science Journal. Supplementary materials will be available in the online journal version

In this work we present the design of the ATLAS unit (Asteroid Terrestrial-impact Last Alert System) that will be installed at Teide Observatory in Tenerife island (Spain). ATLAS-Teide will be built by the Instituto de Astrofisica de Canarias (IAC) and will be operated as part of the ATLAS network in the framework of an operation and science exploitation agreement between the IAC and the ATLAS team at University of Hawaii. ATLAS-Teide will be the first ATLAS unit based on commercial on the shelf (COTS) components. Its design is modular, each module (building block) consist of four Celestron RASA 11 telescopes that point to the same sky field, equipped with QHY600PRO CMOS cameras on an equatorial Direct Drive mount. Each module is equivalent to a 56cm effective diameter telescope and provides a 7.3 deg^2 field of view and a 1.26 arcsec/pix plate scale. ATLAS-Teide will consist of four ATLAS modules in a roll-off roof building. This configuration allows to cover the same sky area of the actual ATLAS telescopes. The first ATLAS module was installed in November 2022 in an existing clamshell at the TO. This module (ATLAS-P) is being used as a prototype to test the system capabilities, develop the needed software (control, image processing, etc.) and complete the fully integration of ATLAS-Teide in the ATLAS network. The preliminary results of the tests are presented here, and the benefits of the new ATLAS design are discussed., Comment: 5 pages, 8 figures, Conference paper

The Galactic bulge and bar are critical to our understanding of the Milky Way. However, due to the lack of reliable stellar distances, the structure and kinematics of the bulge/bar beyond the Galactic center have remained largely unexplored. Here, we present a method to measure distances of luminous red giants using a period-amplitude-luminosity relation anchored to the Large Magellanic Cloud, with random uncertainties of 10-15% and systematic errors below 1-2%. We apply this method to data from the Optical Gravitational Lensing Experiment (OGLE) to measure distances to $190,302$ stars in the Galactic bulge and beyond out to 20 kpc. Using this sample we measure a distance to the Galactic center of $R_0$ = $8108\pm106_{\rm stat}\pm93_{\rm sys}$ pc, consistent with astrometric monitoring of stars orbiting Sgr A*. We cross-match our distance catalog with Gaia DR3 and use the subset of $39,566$ overlapping stars to provide the first constraints on the Milky Way's velocity field ($V_R,V_\phi,V_z$) beyond the Galactic center. We show that the $V_R$ quadrupole from the bar's near side is reflected with respect to the Galactic center, indicating that the bar is both bi-symmetric and aligned with the inner disk, and therefore dynamically settled along its full extent. We also find that the vertical height $V_Z$ map has no major structure in the region of the Galactic bulge, which is inconsistent with a current episode of bar buckling. Finally, we demonstrate with N-body simulations that distance uncertainty plays a major factor in the alignment of the major and kinematic axes of the bar and distribution of velocities, necessitating caution when interpreting results for distant stars., Comment: Submitted to AAS journals, comments welcome

We analyze high-cadence data from the Transiting Exoplanet Survey Satellite (TESS) of the ambiguous nuclear transient (ANT) ASASSN-18el. The optical changing-look phenomenon in ASASSN-18el has been argued to be due to either a drastic change in the accretion rate of the existing active galactic nucleus (AGN) or the result of a tidal disruption event (TDE). Throughout the TESS observations, short-timescale stochastic variability is seen, consistent with an AGN. We are able to fit the TESS light curve with a damped-random-walk (DRW) model and recover a rest-frame variability amplitude of $\hat{\sigma} = 0.93 \pm 0.02$ mJy and a rest-frame timescale of $\tau_{DRW} = 20^{+15}_{-6}$ days. We find that the estimated $\tau_{DRW}$ for ASASSN-18el is broadly consistent with an apparent relationship between the DRW timescale and central supermassive black hole mass. The large-amplitude stochastic variability of ASASSN-18el, particularly during late stages of the flare, suggests that the origin of this ANT is likely due to extreme AGN activity rather than a TDE., Comment: 13 pages, 8 figures. Will be submitted to AAS journals. Comments welcome

We characterize the spatial density of the Pan-STARRS1 (PS1) sample of RR Lyrae stars, to study the properties of the old Galactic stellar halo as traced by RRab stars. This sample of 44,403 sources spans Galactocentric radii of $0.55 \; \mathrm{kpc} \leq R_{\mathrm{gc}} \leq 141 \; \mathrm{kpc}$ with a distance precision of 3\% and thus is able to trace the halo out to larger distances than most previous studies. After excising stars that are attributed to dense regions such as stellar streams, the Galactic disc and bulge as well as halo globular clusters, the sample contains ${\sim}11,000$ sources within $20 \; \mathrm{kpc} \leq R_{\mathrm{gc}} \leq 131 \; \mathrm{kpc}$. We then apply forward modeling using ellipsoidal stellar density models $��(l,b,R_{\mathrm{gc}})$ both with a constant and a radius-dependent halo flattening $q(R_{\mathrm{gc}})$. Assuming constant flattening $q$, the distribution of the sources is reasonably well fit from $20 \; \mathrm{kpc}$ to $131 \; \mathrm{kpc}$ by a single power law with $n=4.40^{+0.05}_{-0.04}$ and $q=0.918^{+0.016}_{-0.014}$. The distance distribution is fit comparably well by an Einasto profile with $n=9.53^{+0.27}_{-0.28}$, an effective radius $r_{\mathrm{eff}}=1.07 \pm 0.10 \; \mathrm{kpc}$ and a halo flattening of $q=0.923 \pm 0.007$. If we allow for a radius-dependent flattening $q(R_{\mathrm{gc}})$, we find evidence for a distinct flattening of $q{\sim}0.8$ of the inner halo at ${\sim} 25 \; \mathrm{kpc}$. Additionally, we find that the south Galactic hemisphere is more flattened than the north Galactic hemisphere. The results of our work are largely consistent with many earlier results, e.g. \cite{Watkins2009}, \cite{Iorio2017}. We find that the stellar halo, as traced in RR Lyrae stars, exhibits a substantial number of further significant over- and underdensities, even after all known overdensities have been masked.

A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 3�� Steradian Survey Processing Version 2 to construct the White Dwarf Luminosity Functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalised maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833 sr, which is 83% of the 3�� sky and 62% of the whole sky. By dividing the sky using Voronoi tessellation, photometric and astrometric uncertainties are recomputed at each step of the integration to improve the accuracy of the maximum volume. Interstellar reddening is considered throughout the work. We find a disc-to-halo white dwarf ratio of about 100., 18 pages, 13 figures, 2 tables in text, 4 tables in Appendix A, supplementary online materials are available on MNRAS. Accepted for publication on 3 Oct 2018

A detection of the predicted anticorrelation between 21cm and either Ly-alpha or H-alpha from the Epoch of Reionization (EOR) would be a powerful probe of the first galaxies. While 3D intensity maps isolate foregrounds in low k_\parallel modes, infrared surveys cannot yet match the field of view and redshift resolution of radio intensity mapping experiments. In contrast, 2D (i.e., broad band) infrared intensity maps can be measured with current experiments and are limited by foregrounds instead of photon or thermal noise. We show 2D experiments can measure most of the 3D fluctuation power at k, Comment: 24 pages, 13 f igures

We present a recalibration of the Sloan Digital Sky Survey (SDSS) photometry with new flat fields and zero points derived from Pan-STARRS1 (PS1). Using PSF photometry of 60 million stars with $16 < r < 20$, we derive a model of amplifier gain and flat-field corrections with per-run RMS residuals of 3 millimagnitudes (mmag) in $griz$ bands and 15 mmag in $u$ band. The new photometric zero points are adjusted to leave the median in the Galactic North unchanged for compatibility with previous SDSS work. We also identify transient non-photometric periods in SDSS ("contrails") based on photometric deviations co-temporal in SDSS bands. The recalibrated stellar PSF photometry of SDSS and PS1 has an RMS difference of {9,7,7,8} mmag in $griz$, respectively, when averaged over $15'$ regions., 13 pages, 7 figures, ApJ, in press. "Hypercalibration" refers to using repeat measurements of many stars from multiple surveys to constrain calibration parameters

We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an SDSS-IV eBOSS subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and AGN) across 7,500 square degrees selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate (KDE) analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4,000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as LSST., 22 pages, 18 figures, accepted by ApJ

We present a new satellite in the outer halo of the Galaxy, the first Milky Way satellite found in the stacked photometric catalog of the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1) Survey. From follow-up photometry obtained with WFI on the MPG/ESO 2.2m telescope, we argue that the object, located at a heliocentric distance of 145+/-17 kpc, is the most distant Milky Way globular cluster yet known. With a total magnitude of M_V=-4.3+/-0.2 and a half-light radius of 20+/-2 pc, it shares the properties of extended globular clusters found in the outer halo of our Galaxy and the Andromeda galaxy. The discovery of this distant cluster shows that the full spatial extent of the Milky Way globular cluster system has not yet been fully explored., 6 pages, 4 figures, accepted

We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 r_P1- and i_P1-band imaging data. Both are luminous systems (M_V ~ -12) located at projected distances of 20.3�� and 10.5�� from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756^{+44}_{-28} kpc and 772^{+61}_{-56} kpc, respectively, and corresponding M31-centric distances of 275+/-7 kpc and 144^{+6}_{-4} kpc . The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes (r_h = 4.2^{+0.4}_{-0.5} arcmin or 912^{+124}_{-93} pc for Lac I; r_h = 6.5^{+1.2}_{-1.0} arcmin or 1456+/-267 pc for Cas III), and consequently low surface brightness (��_0 ~ 26.0 mag/arcsec^2), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3�� Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies., 7 pages, 5 figures. Accepted for publication in ApJ

The NGVS-IR project (Next Generation Virgo Survey - Infrared) is a contiguous near-infrared imaging survey of the Virgo cluster of galaxies. It complements the optical wide-field survey of Virgo (NGVS). The current state of NGVS-IR consists of Ks-band imaging of 4 deg^2 centered on M87, and J and Ks-band imaging of 16 deg^2 covering the region between M49 and M87. In this paper, we present the observations of the central 4 deg^2 centered on Virgo's core region. The data were acquired with WIRCam on the Canada-France-Hawaii Telescope and the total integration time was 41 hours distributed in 34 contiguous tiles. A survey-specific strategy was designed to account for extended galaxies while still measuring accurate sky brightness within the survey area. The average 5\sigma limiting magnitude is Ks=24.4 AB mag and the 50% completeness limit is Ks=23.75 AB mag for point source detections, when using only images with better than 0.7" seeing (median seeing 0.54"). Star clusters are marginally resolved in these image stacks, and Virgo galaxies with \mu_Ks=24.4 AB mag arcsec^-2 are detected. Combining the Ks data with optical and ultraviolet data, we build the uiK color-color diagram which allows a very clean color-based selection of globular clusters in Virgo. This diagnostic plot will provide reliable globular cluster candidates for spectroscopic follow-up campaigns needed to continue the exploration of Virgo's photometric and kinematic sub-structures, and will help the design of future searches for globular clusters in extragalactic systems. Equipped with this powerful new tool, future NGVS-IR investigations based on the uiK diagram will address the mapping and analysis of extended structures and compact stellar systems in and around Virgo galaxies., Comment: 23 pages, 18 figures. Accepted for publication in ApJS

Photometric calibration is currently the dominant source of systematic uncertainty in exploiting type Ia supernovae to determine the nature of the dark energy. We review our ongoing program to address this calibration challenge by performing measurements of both the instrumental response function and the optical transmission function of the atmosphere. A key aspect of this approach is to complement standard star observations by using NIST-calibrated photodiodes as a metrology foundation for optical flux measurements. We present our first attempt to assess photometric consistency between synthetic photometry and observations, by comparing predictions based on a NIST-diode-based determination of the PanSTARRS-1 instrumental response and empirical atmospheric transmission measurements, with fluxes we obtained from observing spectrophotometric standards., 11 pages, submitted to Proceedings of the Calibration and Standardization of Large Surveys and Missions in Astronomy and Astrophysics Conference, held at Fermilab April 16-19 2012

We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last 10 billion years. These objects, which include 13 spectroscopically confirmed SNe Ia at z > 1, were discovered during 14 epochs of reimaging of the GOODS fields North and South over two years with the Advanced Camera for Surveys on HST. Together with a recalibration of our previous HST-discovered SNe Ia, the full sample of 23 SNe Ia at z > 1 provides the highest-redshift sample known. Combined with previous SN Ia datasets, we measured H(z) at discrete, uncorrelated epochs, reducing the uncertainty of H(z>1) from 50% to under 20%, strengthening the evidence for a cosmic jerk--the transition from deceleration in the past to acceleration in the present. The unique leverage of the HST high-redshift SNe Ia provides the first meaningful constraint on the dark energy equation-of-state parameter at z >1. The result remains consistent with a cosmological constant (w(z)=-1), and rules out rapidly evolving dark energy (dw/dz >>1). The defining property of dark energy, its negative pressure, appears to be present at z>1, in the epoch preceding acceleration, with ~98% confidence in our primary fit. Moreover, the z>1 sample-averaged spectral energy distribution is consistent with that of the typical SN Ia over the last 10 Gyr, indicating that any spectral evolution of the properties of SNe Ia with redshift is still below our detection threshold., typos, references corrected, minor additions to exposition 82 pages, 17 figures, 6 tables. Data also available at: http://braeburn.pha.jhu.edu/~ariess/R06. Accepted, Astrophysical Journal vol. 656 for March 10, 2007

We describe the scientific motivation for achieving photometric precision and accuracy below the 1% level, and we present a calibration philosophy based on using calibrated detectors rather than celestial sources as the fundamental metrology reference. A description of the apparatus and methodology is presented, as well as preliminary measurements of relative system throughput vs. wavelength for the Mosaic imager at the CTIO Blanco 4m telescope. We measure the throughput of the optics, filter, and detector by comparing the flux seen by the instrument to that seen by a precisely calibrated monitor photodiode, using a tunable laser as the illumination source. This allows us to measure the transmission properties of the system, passband by passband, with full pupil illumination of the entire optical train. These preliminary results are sufficiently promising that we intend to further pursue this technique, particularly for next-generation survey projects such as PanSTARRS and LSST., Comment: To Appear in "The Future of Photometric, Spectrophotometric and Polarimetric Standardization" Conference Proceedings, C. Sterken ed

As part of the Advanced Camera for Survey (ACS) Virgo Cluster Survey, we have measured Surface Brightness Fluctuations (SBF) in a sample of 100 early-type Virgo galaxies. Distances derived from these measurements are needed to explore the three-dimensional structure of the Virgo Cluster, study the intrinsic parameters of globular clusters associated with the program galaxies, and compare with the galaxy distances derived from globular cluster luminosity functions. Our SBF measurements have been performed in the F850LP bandpass of the Wide Field Channel of the ACS on the Hubble Space Telescope. These are the first measurements of this kind, and we present the first SBF calibration for this bandpass. The measured fluctuations depend on galaxy stellar population variations, which we quantify by galaxy color (g_475-z_850)_0, where g_475 and z_850 are the galaxy magnitudes, respectively, in the F475W and F850LP ACS filters. We derive the following calibration for the absolute SBF magnitude M_850: M_850 = -2.06 +/- 0.04 + (2.0 +/ 0.2) [ (g_475-z_850)_0-1.3 ] in the range 1.3, Comment: 23 pages, 7 figures

The ACIS instrument on board the Chandra X-ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87. We identify 174 X-ray point-sources, of which ~150 are likely LMXBs. This LMXB catalog is combined with deep F475W and F850LP images taken with ACS on HST to examine the connection between LMXBs and globular clusters in M87. Of the 1688 globular clusters in our catalog, f_X = 3.6 +- 0.5% contain a LMXB and we find that the metal-rich clusters are 3 +- 1 times more likely to harbor a LMXB than their metal-poor counterparts. In agreement with previous findings for other galaxies, we find that brighter, more metal-rich clusters are more likely to contain a LMXB. For the first time, however, we are able to demonstrate that the probability, p_X, that a given cluster will contain a LMXB depends sensitively on the dynamical properties of the host cluster. Specifically, we use the HST images to measure the half-light radius, concentration index and central density, \rho_0, for each globular, and define a parameter, \Gamma, which is related to the tidal capture and binary-neutron star exchange rate. Our preferred form for p_X is then p_X \propto \Gamma \rho_0^{-0.42\pm0.11} (Z/Z_{\odot})^{0.33\pm0.1}. We argue that if the form of p_X is determined by dynamical processes, then the observed metallicity dependence is a consequence of an increased number of neutron stars per unit mass in metal-rich globular clusters. Finally, we find no compelling evidence for a break in the luminosity distribution of resolved X-ray point sources. Instead, the LMXB luminosity function is well described by a power law with an upper cutoff at L_X ~ 10^39 erg/s. (abridged), Comment: 23 pages, 21 figures. Accepted for publication in ApJ. Also available at http://www.physics.rutgers.edu/~pcote/acs/publications.html

We have discovered 16 Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to provide the first conclusive evidence for cosmic deceleration that preceded the current epoch of cosmic acceleration. These objects, discovered during the course of the GOODS ACS Treasury program, include 6 of the 7 highest-redshift SNe Ia known, all at z>1.25, and populate the Hubble diagram in unexplored territory. The luminosity distances to these and 170 previous SNe Ia are provided. A purely kinematic interpretation of the SN Ia sample provides evidence at the > 99% confidence level for a transition from deceleration to acceleration or similarly, strong evidence for a cosmic jerk. Using a simple model of the expansion history, the transition between the two epochs is constrained to be at z=0.46 +/- 0.13. The data are consistent with the cosmic concordance model of Omega_M ~ 0.3, Omega_Lambda~0.7 (chi^2_dof=1.06), and are inconsistent with a simple model of evolution or dust as an alternative to dark energy. For a flat Universe with a cosmological constant. When combined with external flat-Universe constraints we find w=-1.02 + 0.13 - 0.19 (and $, Accepted Astrophysical Journal, to Appear June 2004 72 pages, 17 Figures

We present photometric and spectroscopic observations of 23 high redshift supernovae spanning a range of z=0.34-1.03, 9 of which are unambiguously classified as Type Ia. These supernovae were discovered during the IfA Deep Survey, which began in September 2001 and observed a total of 2.5 square degrees to a depth of approximately m=25-26 in RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional observations continuing until April 2002. We give a brief description of the survey motivations, observational strategy, and reduction process. This sample of 23 high-redshift supernovae includes 15 at z>0.7, doubling the published number of objects at these redshifts, and indicates that the evidence for acceleration of the universe is not due to a systematic effect proportional to redshift. In combination with the recent compilation of Tonry et al. (2003), we calculate cosmological parameter density contours which are consistent with the flat universe indicated by the CMB (Spergel et al. 2003). Adopting the constraint that Omega_total = 1.0, we obtain best-fit values of (Omega_m, Omega_Lambda)=(0.33, 0.67) using 22 SNe from this survey augmented by the literature compilation. We show that using the empty-beam model for gravitational lensing does not eliminate the need for Omega_Lambda > 0. Experience from this survey indicates great potential for similar large-scale surveys while also revealing the limitations of performing surveys for z>1 SNe from the ground., 67 pages, 12 figures, 12 tables, accepted for publication in the Astrophysical Journal

We present discoveries of SNe Ia at z > 1 and the photometric diagnostic used to discriminate them from other types of SNe detected during the GOODS Hubble Space Telescope Treasury program with the Advanced Camera for Surveys (ACS). Photometric redshift measurements of the hosts combined with deep f606w, f775w, and f850lp imaging discriminates hydrogen-rich SNe II from SNe I at z > 1 by exploiting the ultraviolet (UV) deficit in the energy distributions of SNe Ia. This sorting allows rapid follow-up of space-based discoveries. Subsequent spectroscopy of 11 GOODS SNe Ia obtained from the ground and with the grism on ACS confirmed the reliability of our photometric screening. We present the highest-redshift spectrum of any supernova published to date, SN Ia 2002fw at z = 1.3 observed near maximum brightness with the ACS grism. The lack of UV flux for true SNe Ia provides an effective tool for our ongoing efforts to build a sample of SNe Ia at 1.2 < z < 1.8 which will extend the useful range of the magnitude-redshift relation of SNe Ia., accepted for publication, ApJ Letters

We present the discovery of a distant methane dwarf, the first from the Institute for Astronomy (IfA) Deep Survey. The object ("IfA 0230-Z1") was identified from deep optical I and z'-band imaging, being conducted as an IfA-wide collaboration using the prime-focus imager Suprime-Cam on the Subaru 8.2-m Telescope. IfA 0230-Z1 is extremely red in the Iz'J (0.8--1.2 micron) bands but relatively blue in J-H; such colors are uniquely characteristic of T dwarfs. A near-IR spectrum taken with the Keck Telescope shows strong H2O absorption and a continuum break indicative of CH4, confirming the object has a very cool atmosphere. Comparison with nearby T dwarfs gives a spectral type of T3-T4 and a distance of ~45 pc. Simple estimates based on previous T dwarf discoveries suggest that the IfA survey will find a comparable number of T dwarfs as the 2MASS survey, albeit at a much larger average distance. We also discuss the survey's ability to probe the galactic scale height of ultracool (L and T) dwarfs., Astrophysical Journal Letters, in press

We present optical spectra, obtained with the Keck 10-m telescope, of two high-redshift type Ia supernovae (SNe Ia) discovered by the High-z Supernova Search Team: SN 1999ff at z=0.455 and SN 1999fv at z~1.2, the highest-redshift published SN Ia spectrum. Both SNe were at maximum light when the spectra were taken. We compare our high-z spectra with low-z normal and peculiar SNe Ia as well as with SNe Ic, Ib, and II. There are no significant differences between SN 1999ff and normal SNe Ia at low redshift. SN 1999fv appears to be a SN Ia and does not resemble the most peculiar nearby SNe Ia., Comment: 6 pages including 2 figures; to appear in The Astrophysical Journal Letters

Using published photometry and spectroscopy, we construct the fundamental plane and D_n-Sigma relations in Leo I, Virgo and Fornax. The published Cepheid P-L relations to spirals in these clusters fixes the relation between angular size and metric distance for both the fundamental plane and D_n-Sigma relations. Using the locally calibrated fundamental plane, we infer distances to a sample of clusters with a mean redshift of cz \approx 6000 \kms, and derive a value of H_0=78+- 5+- 9 km/s/Mpc (random, systematic) for the local expansion rate. This value includes a correction for depth effects in the Cepheid distances to the nearby clusters, which decreased the deduced value of the expansion rate by 5% +- 5%. If one further adopts the metallicity correction to the Cepheid PL relation, as derived by the Key Project, the value of the Hubble constant would decrease by a further 6%+- 4%. These two sources of systematic error, when combined with a +- 6% error due to the uncertainty in the distance to the Large Magellanic Cloud, a +- 4% error due to uncertainties in the WFPC2 calibration, and several small sources of uncertainty in the fundamental plane analysis, combine to yield a total systematic uncertainty of +- 11%. We find that the values obtained using either the CMB, or a flow-field model, for the reference frame of the distant clusters, agree to within 1%. The Dn-Sigma relation also produces similar results, as expected from the correlated nature of the two scaling relations. A complete discussion of the sources of random and systematic error in this determination of the Hubble constant is also given, in order to facilitate comparison with the other secondary indicators being used by the Key Project., Comment: 21 pages, 3 figures, Accepted for publication in ApJ

We present analysis of local large scale flows using the Surface Brightness Fluctuation (SBF) Survey for the distances to 300 early-type galaxies. Our models of the distribution function of mean velocity and velocity dispersion at each point in space include a uniform thermal velocity dispersion and spherical attractors whose position, amplitude, and radial shape are free to vary. Our fitting procedure performs a maximum likelihood fit of the model to the observations. We obtain a Hubble constant of Ho = 77 +/- 4 +/- 7 km/s/Mpc, but a uniform Hubble flow is not acceptable fit to the data. Inclusion of two attractors, one of whose fit location coincides with the Virgo cluster and the other whose fit location is slightly beyond the Centaurus clusters nearly explain the peculiar velocities, but the quality of the fit can be further improved by the addition of a quadrupole correction to the Hubble flow. Although the dipole and quadrupole may be genuine manifestations of more distant density fluctuations, we find evidence that they are more likely due to non-spherical attractors. We find no evidence for bulk flows which include our entire survey volume (R < 3000 km/s); our volume is at rest with respect to the CMB. The fits to the attractors both have isothermal radial profiles (v ~ 1/r) over a range of overdensity between about 10 and 1, but fall off more steeply at larger radius. The best fit value for the small scale, cosmic thermal velocity is 180 +/- 14 km/s., 37 pages, AASTeX Latex, including 30 Postscript figures, submitted to Astrophysical Journal, July 2, 1999

We present the $V$-band globular cluster luminosity functions (GCLFs) of the Fornax Cluster galaxies NGC 1344, NGC 1380, NGC 1399, and NGC 1404. Our observations reach to $V = 24.8$, roughly one magnitude beyond the GCLF turnover $m^0_V$, with $\sim90\%$ completeness. From the amplitude of the galaxy surface brightness fluctuations, we also estimate the number of globular clusters fainter than this cutoff magnitude. The GCLFs of these galaxies are well fitted by Gaussians; the weighted means of their turnover magnitudes and dispersions are $\langle m^0_V\rangle = 23.88 \pm 0.10$ mag and $\langle\sigma\rangle = 1.35\pm 0.07$ mag. The assumption of a universal value for the absolute magnitude of the turnover $M^0_V$ places the Fornax cluster $0.13 \pm 0.11$ mag more distant than Virgo. However, in light of recent Cepheid and other high-precision distance measurements, as well as ongoing HST observations of GCLFs for the purpose of determining the extra-galactic distance scale, we choose to re-examine the universal GCLF hypothesis. Based on data from groups and clusters of galaxies, we find evidence that $M^0_V$ becomes fainter as the local density of galaxies increases. We speculate on the possible cause of this trend; if it is confirmed, GCLF observations will be less useful for determining distances, but may provide important information for constraining theories of star formation in primordial galaxy halos., Comment: Accepted for publication in the Astrophysical Journal Letters; eight pages including figures, uses aas2pp4.sty (included)

We present an IDL graphical user interface-driven software package designed for the analysis of extrasolar planet transit light curves. The Transit Analysis Package (TAP) software uses Markov Chain Monte Carlo (MCMC) techniques to fit light curves using the analytic model of Mandel and Agol (2002). The package incorporates a wavelet based likelihood function developed by Carter and Winn (2009) which allows the MCMC to assess parameter uncertainties more robustly than classic chi-squared methods by parameterizing uncorrelated "white" and correlated "red" noise. The software is able to simultaneously analyze multiple transits observed in different conditions (instrument, filter, weather, etc). The graphical interface allows for the simple execution and interpretation of Bayesian MCMC analysis tailored to a user's specific data set and has been thoroughly tested on ground-based and Kepler photometry. AutoKep provides a similar GUI for the preparation of Kepler MAST archive data for analysis by TAP or any other analysis software. This paper describes the software release and provides instructions for its use., 8 pages, 2 figures

The proper usage of Type Ia supernovae (SNe Ia) as distance indicators has revolutionized cosmology, and added a new dominant component to the energy density of the Universe, dark energy. Following the discovery and confirmation era, the currently ongoing SNe Ia surveys aim to determine the properties of the dark energy. ESSENCE is a five year ground-based supernova survey aimed at finding and characterizing 200 SNe Ia in the redshift domain z=[0.2-0.8]. The goal of the project is to put constraints on the equation of state parameter, w, of the dark energy with an accuracy of, Submitted to EPS13

The practice of measuring galaxy distances from their spatial fluctuations in surface brightness is now a decade old. While several past articles have included some review material, this is the first intended as a comprehensive review of the surface brightness fluctuation (SBF) method. The method is conceptually quite simple, the basic idea being that nearby (but unresolved) star clusters and galaxies appear "bumpy", while more distant ones appear smooth. This is quantified via a measurement of the amplitude of the Poisson fluctuations in the number of unresolved stars encompassed by a CCD pixel (usually in an image of an elliptical galaxy). Here, we describe the technical details and difficulties involved in making SBF measurements, discuss theoretical and empirical calibrations of the method, and review the numerous applications of the method from the ground and space, in the optical and near-infrared. We include discussions of stellar population effects and the "universality" of the SBF standard candle. A final section considers the future of the method., Invited review article to appear in: `Post-Hipparcos Cosmic Candles', A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in press. 22 pages, including 3 postscript figures; uses Kluwer's crckapb.sty LaTex macro file, enclosed

Significant progress has been made during the last 10 years toward resolving the debate over the expansion rate of the Universe. The current value of the Hubble parameter, Ho, is now arguably known with an accuracy of 10%, largely due to the tremendous increase in the number of galaxies in which Cepheid variable stars have been discovered. Increasingly accurate secondary distance indicators, many calibrated using Cepheids, now provide largely concordant measurements of Ho well out into the Hubble flow, and deviations from the smooth Hubble flow allow us to better measure the dynamical structure of the local Universe. The change in the Hubble parameter with redshift provided the first direct evidence for acceleration and "dark energy" in the Universe. Extragalactic distance measurements are central to determining the size, age, composition, and fate of the Universe. We discuss remaining systematic uncertainties, particularly related to the Cepheid calibration, and identify where improvements are likely to be made in the next few years., Comment: 18 pages, 1 figure; contribution to Measuring and Modeling the Universe, Carnegie Observatories Astrophysics Series Vol. 2, ed. W. L. Freedman

Standard inflationary hot big bang cosmology predicts small fluctuations in the Cosmic Microwave Background (CMB) with isotropic Gaussian statistics. All measurements support the standard theory, except for a few anomalies discovered in the Wilkinson Microwave Anisotropy Probe maps and confirmed recently by the Planck satellite. The Cold Spot is one of the most significant of such anomalies, and the leading explanation of it posits a large void that imprints this extremely cold area via the linear Integrated Sachs-Wolfe (ISW) effect due to the decay of gravitational potentials over cosmic time, or via the Rees-Sciama (RS) effect due to late-time non-linear evolution. Despite several observational campaigns targeting the Cold Spot region, to date no suitably large void was found at higher redshifts $z > 0.3$. Here we report the detection of an $R =(192 \pm 15) h^{-1}Mpc$ size supervoid of depth $\delta = -0.13 \pm 0.03$, and centred at redshift $z = 0.22$. This supervoid, possibly the largest ever found, is large enough to significantly affect the CMB via the non-linear RS effect, as shown in our Lemaitre-Tolman-Bondi framework. This discovery presents the first plausible explanation for any of the physical CMB anomalies, and raises the possibility that local large-scale structure could be responsible for other anomalies as well., Comment: 8 pages, 4 figures, to appear in the proceedings of the Moriond Cosmology Conference 2014