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Title

Galaxy group at z=0.3 associated with the damped Lyman alpha system towards quasar Q1127-145

Author(s)

Kacprzak, Glenn G.;  Murphy, Michael T.;  Churchill, Christopher W.

Abstract

We performed a spectroscopic galaxy survey, complete to mF814W≤ 20.3 (LB > 0.15L★B at z= 0.3), within 100 × 100 arcsec2 of the quasar Q1127& 8211;145 (zem= 1.18). The Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph (UVES) quasar spectrum contains three zabs < 0.33 Mg ii absorption systems. We obtained eight new galaxy redshifts, adding to the four previously known, and galaxy star formation rates (SFRs) and metallicities were computed where possible. A strong Mg ii system [Wr(2796) = 1.8Å], which is a known damped Lyman α absorber (DLA), had three previously identified galaxies; we found two additional galaxies associated with this system. These five galaxies form a group with diverse properties, such as a luminosity range of 0.04 ≤LB≤ 0.63 L★B, an impact parameter range of 17 ≤D≤ 241 kpc and a velocity dispersion of σ= 115 km s−1. The DLA group galaxy redshifts span beyond the 350 km s−1 velocity spread of the metallic absorption lines of the DLA itself. The two brightest group galaxies have SFRs of ∼few M⊙ yr−1 and should not have strong winds. We have sufficient spectroscopic information to directly compare three of the five group galaxies' (emission-line) metallicities with the DLA (absorption) metallicity: the DLA metallicity is one-tenth solar, substantially lower than the three galaxies' metallicity which ranges between less than 1/2 solar to solar. Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC-2) imaging shows perturbed morphologies for the three brightest group galaxies, with tidal tails extending ∼25 kpc. We favour a scenario where the DLA absorption originates from tidal debris in the group environment. Another absorber exhibits weak Mg ii absorption [Wr(2796) = 0.03Å] and had a previously identified galaxy at a similar redshift. We have identified a second galaxy associated with this system. Both galaxies have solar metallicities and unperturbed morphologies in the HST/WFPC-2 image. The SFR of one galaxy is much lower than that expected for strong outflows. Finally, we have also identified five galaxies at large impact parameters with no associated Mg ii absorption [Wr(2796) ≲ 5.7 mÅ, 3σ] in the spectrum of Q1127–145.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Monthly Notices of the Royal Astronomical Society, Vol. 406, no. 1 (Jul 2010), pp. 445-459

Publication year

2010

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Absorption lines;  Haloes;  Interactions;  ISM galaxies;  Quasars

Publisher

Wiley-Blackwell Publishing

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2010.16667.x

Copyright

Copyright © 2010 The Authors. Journal compilation copyright © 2010 Royal Astronomical Society. The accepted manuscript is reproduced in accordance with the copyright policy of the publisher. The definitive publication is available at www.interscience.wiley.com.

Research Projects

Galaxy formation and femtosecond frequency combs, Australian Research Council grant number DP0877998

Full text

Peer reviewed