"We have found the first case of a physical triple-quasar system," said astronomer George Djorgovski of the California Institute of Technology (Caltech) in Pasadena, leader of an international team reporting the discovery at the meeting. Two of the quasars in the group, designated QQQ 1432-0106, were discovered before 1989. Astronomers originally believed that the pair was an illusion created b...

Current microlensing searches calibrate the mass fraction of the Milky Way halo which is in the form of Massive Compact Halo Objects (MACHOs). We show that surveys like the Sloan Digital Sky Survey (SDSS) can probe the same quantity in halos of distant galaxies. Microlensing of background quasars by MACHOs in intervening galaxies would distort the equivalent width distribution of the quasar emi...

We present both photometry and spectra of the individual images of the quadruple gravitational lens system Q2237+0305. Comparison of spectra obtained at two epochs, separated by ∼ 3 years, shows evidence for significant changes in the emission line to continuum ratio of the strong ultraviolet CIV λ1549, CIII] λ1909 and MgII λ2798 lines. The short, ∼ 1 day, light–travel time differences between ...

We report on imaging and spectroscopic observations of the radio-loud, highly polarized quasar PKS 1610–771 (z = 1.71). Our long-slit spectroscopy of the companion 4.55 NW of the quasar confirms the stellar nature of this object, so ruling out the previously suspected gravitationally lensed nature of this system. PKS 1610–771 looks fuzzy on our sub-arcsecondR and I images and appears located in...

This is the first paper of a series on the methods and results of the Active Galactic Nuclei In Cosmological Simulations (AGNICS) project, which incorporates the physics of AGN into GalICS, a galaxy formation model that combines large cosmological Nbody simulations of dark matter hierarchical clustering and a semi-analytic approach to the physics of the baryons. The project explores the quasar-...

Much evidence has been presented in favor of and against the existence of two distinct populations of quasars, radio-loud and radio-quiet. The SDSS differs from earlier optically selected quasar surveys in the large number of quasars and the targeting of FIRST radio source counterparts as quasar candidates. This allows a qualitatively different approach of constructing a series of samples at di...

We report the serendipitous discovery of a previously unknown quasar at 10.5 from Q2225-403 (z = 2.410). The observation of the broad emission line of Mg iiλ2798 and of the surrounding Fe ii multiplets indicates that the companion quasar is at z = 0.932. The spectrum of Q2225-403 shows a number of absorption lines, the most noteworthy is the Mg ii line at the same redshift of the companion, sug...

We examine the recent report by Prochter et al. that gamma-ray burst (GRB) sight lines have a much higher incidence of strong Mg II absorption than quasar sight lines. We give further evidence that this observed difference is not due to intervening dust extinction that would cause selection effects in the quasar sample. Instead, we propose that the difference is due to the different beam sizes ...

The high-redshift radio-loud quasar PKS 2126−158 is found to have a large number of red galaxies in close apparent proximity. We use the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to obtain optical spectra for a large fraction of these sources. We show that there is a group of galaxies at z ∼ 0.66, coincident with a metal-line absorption system seen in the quasar’s optical spectrum...

We compare quasar-selection techniques based on their optical variability using data from the Catalina Real-time Transient Survey (CRTS). We introduce a new technique based on Slepian wavelet variance (SWV) that shows comparable or better performance to structure functions and damped random walk models but with fewer assumptions. Combining these methods with Wide-field Infrared Survey Explorer ...