A study of the circumgalactic medium at z similar to 0.6 using damped Lyman alpha galaxies

作者：Rahmani Hadi; Peroux Celine; Turnshek David A; Rao Sandhya M; Quiret Samuel; Hamilton Timothy S; Kulkarni Varsha P; Monier Eric M; Zafar Tayyaba

来源：Monthly Notices of the Royal Astronomical Society, 2016, 463(1): 980-1007.

DOI：10.1093/mnras/stw1965

• galaxies: abundances
• intergalactic medium
• quasars: absorption lines

We present the study of a sample of nine quasi-stellar object fields, with damped Lyman alpha (DLA) or sub-DLA systems at z similar to 0.6, observed with the X-Shooter spectrograph at the Very Large Telescope. By suitably positioning the X-Shooter slit based on high spatial resolution images of Hubble Space Telescope/Advanced Camera for Surveys we are able to detect absorbing galaxies in seven out of nine fields (similar to 78 per cent success rate) at impact parameters from 10 to 30 kpc. In five out of seven fields the absorbing galaxies are confirmed via detection of multiple emission lines at the redshift of DLAs where only one out of five also emits a faint continuum. In two out of these five fields we detect a second galaxy at the DLA redshift. Extinction corrected star formation rates (SFRs) of these DLA galaxies, estimated using their H alpha fluxes, are in the range 0.3-6.7 M-aS (TM) yr(-1). The emission metallicities of these five DLA galaxies are estimated to be from 0.2 to 0.9 Z(aS (TM)). Based on the Voigt profile fits to absorption lines we find the metallicity of the absorbing neutral gas to be in a range of 0.05-0.6 Z(aS (TM)). The two remaining DLA galaxies are quiescent galaxies with SFR < 0.4 M-aS (TM) yr(-1) (3 sigma) presenting continuum emission but no emission lines. Using X-Shooter spectrum we estimate i-band absolute magnitude of -19.5 +/- 0.2 for both these DLA galaxies that indicates they are sub-L-a <dagger galaxies. Comparing our results with that of other surveys in the literature we find a possible redshift evolution of the SFR of DLA galaxies.

• 出版日期2016-11-21