Christopher N. A. Willmer

AEGIS: Enhancement of Dust-enshrouded Star Formation in Close Galaxy Pairs and Merging Galaxies up to z ~ 1*

Using data from the DEEP2 Galaxy Redshift Survey and HST/ACS imaging in the Extended Groth Strip, we select nearly 100 interacting galaxy systems, including kinematic close pairs and morphologically identified merging galaxies. Spitzer MIPS 24 μm fluxes of these systems reflect the current dusty star formation activity, and at a fixed stellar mass (M*) the median infrared luminosity (LIR) among merging galaxies and close pairs of blue galaxies is twice (1.9 ± 0.4) that of control pairs drawn from isolated blue galaxies. Enhancement declines with galaxy separation, being strongest in close pairs and mergers and weaker in wide pairs compared to the control sample. At ~ 0.9, 7.1% ± 4.3% of massive interacting galaxies (M* > 2 × 1010 M☉) are found to be ULIRGs, compared to 2.6% ± 0.7% in the control sample. The large spread of LIR/M* among interacting galaxies suggests that this enhancement may depend on the merger stage as well as other as yet unidentified factors (e.g., galaxy structure, mass ratio, orbital characteristics, presence of AGN or bar). The contribution of interacting systems to the total IR luminosity density is moderate (36%).

Observational constraints on the physics behind the evolution of AGN since z 1

We explore the evolution with redshift of the rest-frame colours and space densities of active galactic nuclei (AGN) hosts (relative to normal galaxies) to shed light on the dominant mechanism that triggers accretion on to supermassive black holes as a function of cosmic time. Data from serendipitous wide-area XMM surveys of the Sloan Digital Sky Survey (SDSS) footprint (XMM/SDSS; Needles in the Haystack Survey) are combined with Chandra deep observations in the All-wavelength Extended Groth Strip International Survey (AEGIS), GOODS-North and GOODS-South to compile uniformly selected samples of moderate-luminosity X-ray AGN [LX(2–10xa0keV) = 1041–1044xa0ergxa0s−1] at redshifts 0.1, 0.3 and 0.8. It is found that the fraction of AGN hosted by red versus blue galaxies does not change with redshift. Also, the X-ray luminosity density associated with either red or blue AGN hosts remains nearly constant since z= 0.8. X-ray AGN represent a roughly fixed fraction of the space density of galaxies of given optical luminosity at all redshifts probed by our samples. In contrast the fraction of X-ray AGN among galaxies of a given stellar mass decreases with decreasing redshift. These findings suggest that the same process or combination of processes for fuelling supermassive black holes is in operation in the last 5xa0Gyr of cosmic time. The data are consistent with a picture in which the drop of the accretion power during that period (1xa0dex since z= 0.8) is related to the decline of the space density of available AGN hosts, as a result of the evolution of the specific star formation rate of the overall galaxy population. Scenarios which attribute the evolution of moderate-luminosity AGN since z≈ 1 to changes in the suppermassive black hole accretion mode are not favoured by our results.

A Medium-deep Survey of a Minislice at the North Galactic Pole. II. The Data

We report 328 redshifts, b

Oxford SWIFT IFS and multi-wavelength observations of the Eagle galaxy at z=0.77

_J

Optimizing parallel observations for the JWST/MIRI instrument

magnitudes and b

Observational constraints on the physics behind the evolution of active galactic nuclei since z∼ 1: The physics of AGN evolution

_J

Oxford SWIFT integral field spectrograph and multiwavelength observations of the Eagle galaxy at z= 0.77: The Eagle galaxy at z = 0.77

--r

A medium-deep redshift survey of a minislice at the north Galactic pole

_F

Erratum: “Metallicity Effects on Dust Properties in Starbursting Galaxies” (ApJ, 678, 804 [2008])

colors of galaxies measured in a redshift survey of a 4

Astronomical Software Wants To Be Free: A Manifesto

^circ