相关论文: Obscuration by Gas and Dust in Luminous Quasars

We explore the extinction/reddening of ~35,000 uniformly selected quasars with 0<z<5.3 in order to better understand their intrinsic optical/ultraviolet spectral energy distributions. Using rest-frame optical-UV photometry taken from the…

We present results of a study of 12 dust-reddened quasars with 0.4 < z < 2.65 and reddenings in the range 0.15 < E(B-V) < 1.7. We obtained ACIS-S X-ray spectra of these quasars, estimated the column densities towards them, and hence…

A majority of quasar surveys have been based on criteria which assume strong blue continua or a UV-excess. Any amount of dust along the line-of-sight is expected to drastically extinguish the optical/UV flux leading to a selection bias.…

We present short \chandra observations of twelve bright (i<18) z_em~1.5 quasars from the Sloan Digital Sky Survey chosen to have significantly redder optical colors than most quasars at the same redshift. Of the five quasars with optical…

Red quasars are very red in the optical through near-infrared (NIR) wavelengths, which is possibly due to dust extinction in their host galaxies as expected in a scenario in which red quasars are an intermediate population between…

We present NuSTAR hard X-ray (3-79 keV) observations of three Type 2 quasars at z ~ 0.4-0.5, optically selected from the Sloan Digital Sky Survey (SDSS). Although the quasars show evidence for being heavily obscured Compton-thick systems on…

Hard X-ray surveys have uncovered a large population of heavily obscured AGN. They also reveal a population of quasars with moderate obscuration at both visible and X-ray wavelengths. We use Chandra selected samples of quasars from the…

We present a measurement of the star formation properties of a uniform sample of mid-IR selected, unobscured and obscured quasars (QSO1s and QSO2s) in the Bo\"otes survey region. We use an spectral energy distribution (SED) analysis for…

We present a comparison of the gas and dust properties of the dense interstellar matter in six nearby star-forming regions (d<500 pc): rho Oph, Cha I, R CrA, IC 348, NGC 1333, and Orion. We measure from Chandra and XMM-Newton observations…

We present a survey for neutral atomic-carbon (CI) along gamma-ray burst (GRB) sightlines, which probes the shielded neutral gas-phase in the interstellar medium (ISM) of GRB host galaxies at high redshift. We compile a sample of 29 medium-…

Recent works have suggested that selection criteria based on MIR colors can be used to reveal a population of dust-enshrouded, extremely luminous quasars at z>1. However the X-ray spectral properties of these intriguing sources still remain…

The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. However, direct gas measurements are limited by sensitivity and other…

The spectral energy distributions and infrared (IR) spectra of a sample of obscured AGNs selected in the mid-IR are modeled with recent clumpy torus models to investigate the nature of the sources, the properties of the obscuring matter,…

The Infrared Space Observatory (ISO), launched in November 1995, allows us to measure the far-infrared (far-IR) emission of quasars in greater detail and over a wider energy range than previously possible. In this paper, preliminary results…

We analyze the near-infrared to UV data of 16 quasars with redshifts ranging from 0.71 $<$ $z$ $<$ 2.13 to investigate dust extinction properties. The sample presented in this work is obtained from the High $A_V$ Quasar (HAQ) survey. The…

Mid-infrared spectroscopic measurements from the Infrared Spectrometer on Spitzer (IRS) are given for 125 hard X-ray AGN (14-195 keV) from the Swift Burst Alert Telescope sample and for 32 AGN with black hole masses from reverberation…

We combine two approaches to isolate the AGN luminosity at near-infrared wavelengths and relate the near-IR pure AGN luminosity to other tracers of the AGN. Using integral-field spectroscopic data of an archival sample of 51 local AGNs, we…

Submillimeter (and in some cases millimeter) wavelength continuum measurements are presented for a sample of 40 active galactic nuclei (probably all quasars) lensed by foreground galaxies. The object of this study is to use the lensing…

We present the ISO far-IR photometry of a complete sub-sample of optically selected bright quasars belonging to two complete surveys selected through multicolour (U,B,V,R,I) techniques. The ISOPHOT camera on board of the ISO Satellite was…

We have searched for redshifted neutral hydrogen 21cm absorption toward sources from the Stickel et al. `red quasar' sub-sample. Five of these red quasars have been searched for redshifted HI 21cm absorption to optical depth levels of a few…