TY - JOUR
T1 - Hδ-Strong Galaxies in the Sloan Digital Sky Survey
T2 - I. The Catalog
AU - Goto, Tomotsugu
AU - Nichol, Robert C.
AU - Okamura, Sadanori
AU - Sekiguchi, Maki
AU - Miller, Christopher J.
AU - Bernardi, Mariangela
AU - Hopkins, Andrew
AU - Tremonti, Christy
AU - Connolly, Andrew
AU - Castander, Francisco J.
AU - Brinkmann, Jon
AU - Fukugita, Masataka
AU - Harvanek, Michael
AU - Ivezić, Željko
AU - Kleinman, Scot J.
AU - Krzesinski, Jurek
AU - Long, Dan
AU - Loveday, Jon
AU - Neilsen, Eric H.
AU - Newman, Peter R.
AU - Nitta, Atsuko
AU - Snedden, Stephanie A.
AU - Subbarao, Mark
PY - 2003
Y1 - 2003
N2 - We present here a new and homogeneous sample of 3340 galaxies selected from the Sloan Digital Sky Survey (SDSS) based solely on the observed strength of their Hδ hydrogen Balmer absorption line. The presence of a strong Hδ line within the spectrum of a galaxy indicates that the galaxy has undergone a significant change in its star-formation history within the last Gigayear. Therefore, such galaxies have received considerable attention in recent years, because they provide an opportunity to study galaxy evolution in action. These galaxies are commonly known as "post-starburst", "E+A", "k+a", and Hδ-strong galaxies. Their study has been severely hampered by the lack of a large, statistical sample of such galaxies. In this paper, we rectify this problem by selecting a sample of galaxies which possess an absorption Hδ equivalent width of EW(Hδmax) - ΔEW(Hδmax) > 4Å from 106682 galaxies in the SDSS. The measured abundance of our Hδ-strong (HDS) galaxies is 2.6 ± 0.1% of all galaxies within a volumelimited sample of 0.05 < z < 0.1 and Mr*- < -20.5, which is consistent with previous studies of such galaxies described in the literature. We find that only 25 of our HDS galaxies in this volume-limited sample (3.5 ± 0.7%) show no, or little, evidence for [OII] and Hα emission lines, thus indicating that true E+A galaxies (as originally defined by Dressler and Gunn) are extremely rare objects at low redshift, i.e., only 0.09 ± 0.02% of all galaxies in this volume-limited sample are true E + A galaxies. In contrast, 89 ± 5% of our HDS galaxies in the volume-limited sample have significant detections of the [OII] and Hα emission lines. Of these, only 131 galaxies are robustly classified as Active Galactic Nuclei (AGNs) and, therefore, a majority of these emission-line HDS galaxies are star-forming galaxies. We find that 52 ± 12% (27/52) of the galaxies in our volume-limited HDS sample that possess no detectable [OII] emission, do however possess detectable Ha emission lines. These may be dusty star-forming galaxies. We provide the community with this new catalog of Hδ-strong galaxies to aid in our understanding of these galaxies, via detailed follow-up observations, as well as providing a low-redshift sample for comparison with higher redshift studies of HDS galaxies.
AB - We present here a new and homogeneous sample of 3340 galaxies selected from the Sloan Digital Sky Survey (SDSS) based solely on the observed strength of their Hδ hydrogen Balmer absorption line. The presence of a strong Hδ line within the spectrum of a galaxy indicates that the galaxy has undergone a significant change in its star-formation history within the last Gigayear. Therefore, such galaxies have received considerable attention in recent years, because they provide an opportunity to study galaxy evolution in action. These galaxies are commonly known as "post-starburst", "E+A", "k+a", and Hδ-strong galaxies. Their study has been severely hampered by the lack of a large, statistical sample of such galaxies. In this paper, we rectify this problem by selecting a sample of galaxies which possess an absorption Hδ equivalent width of EW(Hδmax) - ΔEW(Hδmax) > 4Å from 106682 galaxies in the SDSS. The measured abundance of our Hδ-strong (HDS) galaxies is 2.6 ± 0.1% of all galaxies within a volumelimited sample of 0.05 < z < 0.1 and Mr*- < -20.5, which is consistent with previous studies of such galaxies described in the literature. We find that only 25 of our HDS galaxies in this volume-limited sample (3.5 ± 0.7%) show no, or little, evidence for [OII] and Hα emission lines, thus indicating that true E+A galaxies (as originally defined by Dressler and Gunn) are extremely rare objects at low redshift, i.e., only 0.09 ± 0.02% of all galaxies in this volume-limited sample are true E + A galaxies. In contrast, 89 ± 5% of our HDS galaxies in the volume-limited sample have significant detections of the [OII] and Hα emission lines. Of these, only 131 galaxies are robustly classified as Active Galactic Nuclei (AGNs) and, therefore, a majority of these emission-line HDS galaxies are star-forming galaxies. We find that 52 ± 12% (27/52) of the galaxies in our volume-limited HDS sample that possess no detectable [OII] emission, do however possess detectable Ha emission lines. These may be dusty star-forming galaxies. We provide the community with this new catalog of Hδ-strong galaxies to aid in our understanding of these galaxies, via detailed follow-up observations, as well as providing a low-redshift sample for comparison with higher redshift studies of HDS galaxies.
KW - Galaxies: evolution
KW - Galaxies: interaction
KW - Galaxies: peculiar
KW - Galaxies: starburst
UR - http://www.scopus.com/inward/record.url?scp=0242361672&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0242361672
SN - 0004-6264
VL - 55
SP - 771
EP - 787
JO - Publications of the Astronomical Society of Japan
JF - Publications of the Astronomical Society of Japan
IS - 4
ER -