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We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGN) and their host galaxies with a novel state-of-the-art AGN radio- to-X-ray spectral energy distribution model fitting code (ARXSED). ARXSED combines multiple components to fit the spectral energy distributions (SEDs) of AGN and their host galaxies. Emission components include radio structures such as lobes and jets, infrared emission from the AGN torus, visible-to-X-ray emission from the accretion disk, and radio-to-ultraviolet emission from the host galaxy. Applying ARXSED to the radio SEDs of 20 3CRR quasars at 1 < z < 2 verifies the need for more than a simple power law when compact radio structures are present. The non-thermal emission contributes 91%-57% of the observed-frame 1.25mm to 850μm flux, and this component must be accounted for when using these wavelengths to estimate star-formation properties. We predict the presence of strong radio-linked X-ray emission in more than half the sample sources. ARXSED estimates median (and the associated first and third quartile ranges) BH mass of $2.9_{1.7}^{6.0} \times 10^9~\rm M_{\odot}$, logarithm of Eddington ratio of $ -1.0_{-1.2}^{-0.6} $, and spin of $ 0.98_{0.94}^{0.99} $ for our sample. The inferred AGN torus and accretion disk parameters agree with those estimated from spectroscopic analyses of similar samples in the literature. We present the median intrinsic SED of the luminous radio-loud quasars at 1 < z < 2 ; this SED represents a significant improvement in the way each component is modeled.

Low radio frequency surveys are important for testing unified models of radio-loud quasars and radio galaxies. Intrinsically similar sources that are randomly oriented on the sky will have different projected linear sizes. Measuring the projected linear sizes of these sources provides an indication of their orientation. Steep-spectrum isotropic radio emission allows for orientation-free sample selection at low radio frequencies. We use a new radio survey of the Bo��tes field at 150 MHz made with the Low Frequency Array (LOFAR) to select a sample of radio sources. We identify 44 radio galaxies and 16 quasars with powers $P>10^{25.5}$ W Hz$^{-1}$ at 150 MHz using cross-matched multi-wavelength information from the AGN and Galaxy Evolution Survey (AGES), which provides spectroscopic redshifts. We find that LOFAR-detected radio sources with steep spectra have projected linear sizes that are on average 4.4$\pm$1.4 larger than those with flat spectra. The projected linear sizes of radio galaxies are on average 3.1$\pm$1.0 larger than those of quasars (2.0$\pm$0.3 after correcting for redshift evolution). Combining these results with three previous surveys, we find that the projected linear sizes of radio galaxies and quasars depend on redshift but not on power. The projected linear size ratio does not correlate with either parameter. The LOFAR data is consistent within the uncertainties with theoretical predictions of the correlation between the quasar fraction and linear size ratio, based on an orientation-based unification scheme., 14 pages, accepted for publication in MNRAS

Using the Herschel Space Observatory we have observed a representative sample of 87 powerful 3CR sources at redshift z < 1. The far-infrared (FIR, 70-500 micron) photometry is combined with mid-infrared (MIR) photometry from the Wide-Field Infrared Survey Explorer (WISE) and catalogued data to analyse the complete spectral energy distributions (SEDs) of each object from optical to radio wavelength. To disentangle the contributions of different components, the SEDs are fitted with a set of templates to derive the luminosities of host galaxy starlight, dust torus emission powered by active galactic nuclei (AGN) and cool dust heated by stars. The level of emission from relativistic jets is also estimated, in order to isolate the thermal host galaxy contribution. The new data are in line with the orientation-based unification of high-excitation radio-loud AGN, in that the dust torus becomes optically thin longwards of 30 micron. The low excitation radio galaxies and the MIR weak sources represent MIR- and FIR-faint AGN population different from the high-excitation MIR-bright objects; it remains an open question whether they are at a later evolutionary state or an intrinsically different population. The derived luminosities for host starlight and dust heated by star formation are converted to stellar masses and star formation rates (SFR). The host-normalized SFR of the bulk of the 3CR sources is low when compared to other galaxy populations at the same epoch. Estimates of the dust mass yield a 1--100 times lower dust/stellar mass ratio than for the Milky Way, indicating that these 3CR hosts have very low levels of interstellar matter explaining the low level of star formation. Less than 10% of the 3CR sources show levels of star formation above those of the main sequence of star forming galaxies., Submitted to the Astronomical Journal on 2015-07-28, accepted on 2016-02-22, not all figures are included in the preprint due to size limitations but available from http://www.cfa.harvard.edu/irac/publications/

Chandra observations of a complete, flux-limited sample of 38 high-redshift (10) indicating obscuration (log N_H ~ 22-24 cm^-2). These properties and the correlation between obscuration and radio core-fraction are consistent with orientation-dependent obscuration as in Unification models. About half the NLRGs have soft X-ray hardness ratios and/or high [OIII] emission line to X-ray luminosity ratio suggesting obscuration by Compton thick (CT) material so that scattered nuclear or extended X-ray emission dominates (as in NGC1068). The ratios of unobscured to Compton-thin (10^{22}< N_H(int) < 1.5 x 10^{24} cm^-2) to CT (N_H(int) > 1.5 x 10^{24} cm^-2) is 2.5:1.4:1 in this high luminosity, radio-selected sample. The obscured fraction is 0.5, higher than is typically reported for AGN at comparable luminosities from multi-wavelength surveys (0.1-0.3). Assuming random nuclear orientation, the unobscured half-opening angle of the disk/wind/torus structure is ~ 60deg and the obscuring material covers 30deg of which ~ 12deg is Compton thick. The multi-wavelength properties reveal that many NLRGs have intrinsic absorption 10-1000x higher than indicated by their X-ray hardness ratios, and their true L_X values are ~10--100x larger than the hardness-ratio absorption corrections would indicate., Comment: 42 pages, 11 figures, 3 tables; ApJ, in press

Herschel will represent a breakthrough in the study of nearby gas-rich and gas-poor galaxies, as it will for the first time permit imaging photometric and spectroscopic observations of their ISM in the FIR-submm wavelength range. The unprecedented sensitivity and angular resolution of Herschel will furthermore yield a breakthrough in our understanding of distant galaxies and AGN, as their gas and dust - both the ISM- and the AGN-related - will for the first time come within reach. Herschel will undoubtedly yield major discoveries concerning the cosmologically evolving gas and dust properties in galaxies, back to very early epochs., Comment: Invited review, at conference "The Dusty and Molecular Universe - A Prelude to HERSCHEL and ALMA", Paris, 27-29 October 2004

In order to test the unification scheme for double-lobed radio sources, the far-infrared properties of matched samples of radio-galaxies and radio-loud quasars were studied using ISOPHOT. The quasar data were complemented with nearly simultaneous submillimeter and centimeter radio data. The results show that quasars are generally brighter than radio-galaxies in their far-infrared output and that beamed non-thermal radiation must be excluded as source for this infrared excess. However, non-thermal flares or optically thick tori can still reconcile these results with the unification scheme., Comment: 4 pages including 1 figure, to be published in the proceedings of ESA conference 'The Universe as seen by ISO', ed. M. Kessler (ESA Special Publications series SP-427)

We try to explain the unusually high far-infrared emission seen by IRAS in the double-lobed radio-loud quasars 3C47, 3C207 and 3C334. High resolution cm--mm observations were carried out to determine their radio core spectra, which are subsequently extrapolated to the far-infrared in order to determine the strength of the synchrotron far-infrared emission. The extrapolated flux densities being considerably lower than the observed values, a significant nonthermal far-infrared component is unlikely in the case of 3C47 and 3C334. However, this component could be responsible for the far-infrared brightness of 3C207. Our analysis demonstrates that nonthermal emission cannot readily account for the difference between quasars and radio galaxies in the amount of their far-infrared luminosity. On the other hand, a significant role for this mechanism is likely; full sampling of the mm-submm spectral energy distributions is needed to address the issue quantitatively., Comment: 7 pages, incl. 3 figures; accepted for publication in A&A

著者人数: 93名, Accepted: 2007-08-09, 資料番号: SA1000719000

VLA imaging at kiloparsec-scale resolution of sixteen core-dominated radio-loud QSOs is presented. Many objects appear to display variable radio emission and their radio morphologies are significantly smaller than those of steep-spectrum quasars, consistent with these objects being observed at sight lines close to their (relativistic, $\gamma \approx$ 4-7) jet axes. The usefulness of the radio source orientation indicator R_V, being defined as ratio of radio core and rest frame optical V-band luminosity, is confirmed., Comment: 11 pages, 11 postscript figures, uses aa.cls 4.03 for LaTeX2e To appear in Astronomy and Astrophysics

著者人数: 60名, Accepted: 2007-08-06, 資料番号: SA1000718000

At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIF phased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically increase the survey speed for the WSRT. Combined surveys with these two facilities will deeply chart the northern sky over almost two decades in radio frequency from \sim 15 up to 1400 MHz. Here we briefly describe some of the capabilities of these new facilities and what radio surveys are planned to study fundamental issues related the formation and evolution of galaxies and clusters of galaxies. In the second part we briefly review some recent observational results directly showing that diffuse radio emission in clusters traces shocks due to cluster mergers. As these diffuse radio sources are relatively bright at low frequencies, LOFAR should be able to detect thousands of such sources up to the epoch of cluster formation. This will allow addressing many question about the origin and evolution of shocks and magnetic fields in clusters. At the end we briefly review some of the first and very preliminary LOFAR results on clusters., Comment: 11 pages, 2 figures, Invited talk at the conference "Diffuse Relativistic Plasmas", Bangalore, 1-4 March 2011; in press for publication in special issue of Journal of Astrophysics and Astronomy