We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z<=0.08) catalogue of visually selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2x10^10^M_{sun}_, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4]-[4.6] colours associated with dust-obscured or 'dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fibre spectral diagnostics, we map the [3.4]-[4.6] versus [4.6]-[12] colours of different emission-line galaxies and find that one-quarter of Seyferts have colours indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGNs missed at shorter wavelengths are at the heart of the ongoing AGN-merger connection debate. The vast majority of mergers hosting dusty AGNs are star forming and located at the centres of M_halo_<10^13^Mc1l_{sun}_ groups. Assuming plausibly short-duration dusty-AGN phases, we speculate that a large fraction of gas-rich mergers experience a brief obscured AGN phase, in agreement with the strong connection between central star formation and black hole growth seen in merger simulations.
We present the first large sample of metal absorption systems in pairs of QSOs with sightlines separated by about 1Mpc at z=2. We found 690 absorption systems in the spectra of 310 QSOs in 170 pairings. Most systems show CIV or MgII absorption.
We have identified a metal-strong [logN(Zn+)>=13.15 or logN(Si^+^)>=15.95] damped Ly{alpha} (MSDLA) population from an automated quasar (QSO) absorber search in the Sloan Digital Sky Survey (SDSS) Data Release 3 quasar sample and find that MSDLAs comprise >>5% of the entire DLA population with z_abs_>=2.2 found in QSO sight lines with r<19.5. We have also acquired 27 Keck ESI (Echellete Spectrograph and Imager) follow-up spectra of metal strong candidates in order to evaluate our automated technique and examine the MSDLA candidates at higher resolution.
We study the cross-correlation between 212 Mg II quasar absorption systems and ~20000 luminous red galaxies (LRGs) selected from the Sloan Digital Sky Survey Data Release 1 (Cat. <J/AJ/126/2579>) in the redshift range 0.4<=z<=0.8. The Mg II systems were selected to have {lambda}{lambda}2796 and 2803 rest-frame equivalent widths >=1.0{AA} and identifications confirmed by the Fe II {lambda}2600 or Mg I {lambda}2852 lines.
The Millennium Galaxy Catalogue (MGC) is a 37.5deg^2^, medium-deep, B-band imaging survey along the celestial equator, taken with the Wide Field Camera on the Isaac Newton Telescope. The survey region is contained within the regions of both the Two Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). The survey has a uniform isophotal detection limit of 26mag.arcsec^-2^ and it provides a robust, well-defined catalogue of stars and galaxies in the range 16<=B_MGC_<24 mag. Here we describe the survey strategy, the photometric and astrometric calibration, source detection and analysis, and present the galaxy number counts that connect the bright and faint galaxy populations within a single survey. We argue that these counts represent the state of the art and use them to constrain the normalizations ({phi}*) of a number of recent estimates of the local galaxy luminosity function. We find that the 2dFGRS, SDSS Commissioning Data (CD), ESO Slice Project, Century Survey, Durham/UKST, Mt Stromlo/APM, SSRS2 and NOG luminosity functions require a revision of their published {phi}* values by factors of 1.05+/-0.05, 0.76+/-0.10, 1.02+/-0.22, 1.02+/-0.16, 1.16+/-0.28, 1.75+/-0.37, 1.40+/-0.26 and 1.01+/-0.39, respectively. After renormalizing the galaxy luminosity functions we find a mean local b_J_ luminosity density of 1.986+/-0.031x10^8^h L_{sun}_.Mpc^-3^
A catalogue of 328 positions, redshifts, bJ magnitudes and bJ-rF colours of galaxies down to bJ=20.5 in 4x0.67 degrees slice close to the North Galactic Pole is presented. Two additional tables containing positions, magnitudes, colours and radial velocities for stars and galaxies not in the main catalogue are also included. The photometry errors are about 0.2 for magnitudes and 0.3 for the colours. The radial velocity errors are estimated as being about 70 km/s. The redshift completeness level of the sample is of the order of ~35% at bj=20.
We present data from a kinematic and photometric study of six mixed pairs. High resolution rotation and velocity dispersion curves, for both gas and stellar components, are presented. Slit orientations were along the major axis of the spiral and, in most of the cases, along the line connecting the galaxy nuclei. B and V luminosity and geometrical profiles and photometric parameters including effective radius and disk scale length are also presented.
Based on drizzled F606W and F814W images, we present quantitative structural parameters in the V-band rest-frame for all galaxies with z<1 and I_814_(AB)<24.5mag in the Hubble Deep Fields North and South. Our structural parameters are based on a two-component surface brightness distribution using a Sersic bulge and an exponential disc. Detailed simulations and comparisons with previous work are presented.
We present unequivocal evidence for a huge (~80x100x100Mp^3^) superstructure at redshift z=0.27 in the three-dimensional distribution of radio galaxies from the Texas-Oxford NVSS Structure 08h region (TONS08) sample, confirming tentative evidence for such a structure from the 7C redshift survey (7CRS). A second, newly discovered superstructure is also found less securely at redshift 0.35 (of dimensions ~100x100x100Mpc^3^). We present full observational details on the TONS08 sample which was constructed to probe structures in the redshift range 0<z<0.5 by matching NVSS sources with objects in APM catalogues to obtain a sample of optically bright (E~R<=19.83), radio-faint (1.4GHz flux density S_1.4_>=3mJy) radio galaxies in the same 25deg^2^ area as part II of the 7CRS.
We studied the correlations of the flux of the broad-line emission (FBLR) with the X-ray emission flux, optical emission flux at 5500{AA} and radio emission flux at 5GHz, respectively, for a large sample of 50 blazars (39 flat-spectrum radio quasars (FSRQs) and 11 BL Lac objects).
