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 Lyα absorbers (logN HI ≥ 20.0 cm −2 ) such as damped Lyα absorption systems (DLAs) and young star-forming galaxies at high redshift, we have conducted narrow-band observations of Lyα emitters (LAEs) in a concentrated region of strong Lyα absorbers at z = 2.3, the J1230+34 field. Using a catalog of Lyα absorbers with logN HI ≥ 20.0 cm −2 based on the baryon oscillation spectroscopic survey (BOSS), we found 6 fields where 3 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 2 DLAs and 2 sub-DLAs present. Our narrow-band imaging observations with Subaru/Suprime-Cam using a custom-made filter, N B400 (λ c = 4003Å and FWHM= 92Å) yield a sample of 149 LAEs in this field. In the large scale (∼50 Mpc), we have found no differences between the obtained Lyα luminosity function and those in the blank fields at similar redshifts. We also compare the frequency distribution of the Lyα rest-frame equivalent width (EW 0 ) 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 H I column density (N HI = 21.08 cm −2 ) in the target field while there are no density excess around the other absorbers with a lower N HI .

Quantifying the Effect of Field Variance on the Hα Luminosity Function with the New Numerical Galaxy Catalog (ν2GC)

“…For investigating the evolution of the galaxies and structure formation, emission-line galaxies (ELGs) have been often used (e.g., Shimasaku et al 2003;Hayashino et al 2004;Matsuda et al 2004;Ouchi et al 2008;Geach et al 2008;Hayashi et al 2010;Mawatari et al 2012;Kodama et al 2013;Darvish et al 2014;Khostovan et al 2015;Shimakawa et al 2017;Ogura et al 2017;Ouchi et al 2018;Shibuya et al 2018) because emission lines from galaxies, such as [O ii] (λλ3727, 3730), [O iii] (λλ4959, 5007), and Hα (λ6563), are good indicators for the star-formation rate (SFR) of galaxies (e.g., Kennicutt 1998;Kewley et al 2004;Moustakas et al 2006;Hayashi et al 2013;Suzuki et al 2016). A strong point to focus on ELGs is that we can observe them over a significantly wide area by utilizing the combination of narrow-band (NB) filters and widefield cameras.…”

Characterizing the circum-galactic medium of damped Lyman-α absorbing galaxies

“…Traditionally, people have used imaging and follow-up spectroscopy (Steidel et al 1997) or narrow-band imaging (Rauch et al 2008;Ogura et al 2017). To find the counterparts of DLAs in a more systematic way, a strategy using triangulation of the X-Shooter slit has been developed.…”

Investigating the early phase of the galaxy evolution through high-z damped Lyα absorption systems

“…For investigating the relationship between DLAs and galaxies, we define a "DLA-concentrated region" as a region where 3 or more DLAs exist within a (50 Mpc) 3 box (Ogura et al 2017). This definition is based on the size of high-z protoclusters (e.g., Overzier (2016); Franck & McGaugh 2016).…”