相关论文: SDSS-V: Revealing a weak accretion state in X-ray …
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…
A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In this paper, we…
Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the one…
We investigate the continuum and emission line properties of 4576 SDSS quasars as a function of their optical/UV SEDs. The optical/UV color distribution of our sample is roughly Gaussian, but with a red tail; we distinguish between 1)…
Fundamental differences in the radio properties of red quasars (QSOs), as compared to blue QSOs, have been recently discovered, positioning them as a potential key population in the evolution of galaxies and black holes across cosmic time.…
We investigate the X-ray properties of the color-selected radio-quiet quasars (RQQs) in the Sloan Digital Sky Survey (SDSS) Early Data Release using ROSAT, Chandra, and XMM-Newton data. In the 0.16-6.28 redshift range, 136 RQQs have X-ray…
There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of…
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…
We have cross-correlated the SDSS DR3 Schneider et al. (2005) quasar catalog with the XMM-Newton archive. Color and redshift selections (g - r > 0.5 and 0.9 z < 2.1) result in a sample of 17 red, moderate redshift quasars. The redshift…
We present the results of a search for red QSOs using a selection based on optical imaging from SDSS and near-infrared imaging from UKIDSS. For a sample of 58 candidates 46 (79%) are confirmed to be QSOs. The QSOs are predominantly…
Observations of quasars (QSOs) shining through or close to galaxies offer a way to probe the properties of the foreground matter through dust extinction and gravitational lensing. In this paper the feasibility of measuring the dust…
We present new X-ray observations of luminous heavily dust-reddened quasars (HRQs) selected from infrared sky surveys. HRQs appear to be a dominant population at high redshifts and the highest luminosities, and may be associated with a…
We present a highly complete sample of broad-line (Type 1) QSOs out to z ~ 3 selected by their mid-infrared colors, a method that is minimally affected by dust reddening. We remove host galaxy emission from the spectra and fit for excess…
We present a new measurement of the space density of high redshift (3.0<z<4.5), X-ray selected QSOs obtained by exploiting the deep and uniform multiwavelength coverage of the COSMOS survey. We have assembled a statistically large (40…
Quasar feedback is a key ingredient in shaping galaxy evolution. A rare population of extremely red quasars (ERQs) at $z=2-3$ are often associated with high-velocity [O III]$\lambda5008$ outflows and may represent sites of strong feedback.…
We use photometric data from Spitzer to explore the mid- and far-IR properties of 10 red QSOs (J-K>2, R-K>5) selected by combining the 2MASS in the NIR with the SDSS at optical wavelengths. Optical and/or near-infrared spectra are available…
We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the FIRST survey with the near-infrared 2MASS catalog and color-selecting red sources. Optical and/or near-infrared spectroscopy…
Webster et al (1995) claimed that up to 80% of QSOs may be obscured by dust. They inferred the presence of this dust from the remarkably broad range of B-K optical-infrared colours of a sample of flat-spectrum PKS radio QSOs. If such dust…
We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper we use X-shooter data, providing spectral coverage from $\sim 3000-25000$ Ang, of a sample of 40 red…
Red quasi-stellar objects (QSOs) are a subset of the luminous end of the cosmic population of active galactic nuclei (AGN), most of which are reddened by intervening dust along the line-of-sight towards their central engines. In recent work…