A search for Ly α emitters around a concentrated region of strong Ly α absorbers at z = 2.3

Abstract

In order to investigate the physical relationship between strong Ly α absorbers (NHI ≥ 20.0cm-2) such as damped Ly α absorption systems (DLAs) and young star-forming galaxies at high redshift, we have conducted narrow-band observations of Ly α emitters (LAEs) in a concentrated region of strong Ly α absorbers at z = 2.3, the J1230+34 field. Using a catalog of Ly α absorbers with log NHI ≥ 20.0cm-2 based on the Baryon Oscillation Spectroscopic Survey, we found six fields where three or more absorbers are concentrated within a (50 Mpc) 3 cubic box in the comoving scale. Among them, we focus on the J1230+34 field, where two DLAs and two sub-DLAs are present. Our narrow-band imaging observations with Subaru/Suprime-Cam using a custom-made filter, NB400 (λc = 4003 Å and FWHM = 92 Å) yield a sample of 149 LAEs in this field. In the large scale (∼50 Mpc), we have found no differences between the obtained Ly α luminosity function and those in the blank fields at similar redshifts. We also compare the frequency distribution of the Ly α rest-frame equivalent width (EW0) in the target field and other fields including both overdensity region and blank field, but find no differences. On the other hand, in the small scale (∼10 Mpc), we have found a possible overdensity of LAEs around a DLA with the highest HI column density (NHI = 21.08cm-2) in the target field while there are no density excesses around the other absorbers with a lower NHI.