We explore how the local environment is related to the type and luminosity of AGN. Recent simulations and observations are converging on the view that the extreme luminosity of quasars is fueled in major mergers of gas-rich galaxies. In such a picture, quasars are expected to be located in regions with higher density of galaxies where mergers are more likely to take place. However, in this pict...

We report on 293 quasars with strong N iv] λ1486 or N iii] λ1750 emission lines (rest-frame equivalent width > 3 Å) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ∼ 1.1% of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properti...

Where do quasars reside? Are quasars located in environments similar to those of typical L galaxies, and, if not, how do they differ? An answer to this question will help shed light on the triggering process of quasar activity. We use the Sloan Digital Sky Survey to study the environment of quasars and compare it directly with the environment of galaxies. We find that quasars (Mi ≤ −22, z ≤ 0.4...

We present the results of the “Quasars near Quasars” (QNQ) survey, a CCD-based slitless spectroscopic survey for faint V <∼ 22 quasars at 1.7 <∼ z <∼ 3.6 on 18 26.2 × 33.5 fields centred on bright quasars at 2.76 < z < 4.69. In total 169 quasar candidates with emission lines were selected from the extracted flux-calibrated spectra on the basis of well-defined automatic selection criteria follow...

We have carried out the first systematic survey of the sub-millimeter properties of broad absorption line (BAL) quasars. 30 BAL quasars drawn from a homogeneously selected sample from the Sloan Digital Sky Survey at redshifts 2 < z < 2.6 were observed with the SCUBA array at the JCMT to a typical rms sensitivity of 2.5mJy. Eight quasars were detected at > 2σ significance, four of which are at >...

We have conducted a pilot survey for z > 3.5 quasars by combining the FIRST radio survey with the SDSS. While SDSS already targets FIRST sources for spectroscopy as quasar candidates, our survey includes fainter quasars and greatly improves the discovery rate by using strict astrometric criteria for matching the radio and optical positions. Our method allows for selection of high-redshift quasa...

A statistical study is presented of (a) the frequency of narrow C iv λ1549 absorption lines in 1.5 < ∼ z < ∼ 3.6 radio-quiet and radio-loud quasars, and of (b) the UV and radio properties of the absorbed quasars. The quasar sample is unbiased with respect to absorption properties and the radio-quiet and radio-loud subsamples are well matched in redshift and luminosity. A similarly high incidenc...

I review recent observations on the evolution of quasars, describe new surveys for quasars at z > 5 and for quasars with z > 3.3 down to luminosities corresponding to L* galaxies, and note the possible connection between the evolution of the star formation rate in young galaxies and the evolution of quasars.

With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar’s environment in absorption. We search 149 moderate resolution background quasar spectra, from Gemini, Keck, the MMT, and the SDSS to survey Lyman Limit Systems (LLSs) and Damped Lyα systems (DLAs) in the vicinity of 1.8 < z < 4.0 luminous foreground quasars. A sample of 27...

We present 4–7 ks Chandra observations of 35 Broad Absorption Line (BAL) quasars from the Large Bright Quasar Survey, the largest sample of sensitive, 0.5–8.0 keV X-ray observations of this class of quasars to date. The limited ranges in both redshift (z = 1.42–2.90) and ultraviolet luminosity (a factor of ≈ 12) of the sample also make it relatively uniform. Of 35 targets, 27 are detected for a...