TY - JOUR
T1 - HIghMass-High HI Mass, HI-Rich Galaxies at z~0 Sample Definition, Optical and H alpha imaging, and star formation properties
AU - Huang, Shan
AU - Haynes, Martha P.
AU - Giovanelli, Riccardo
AU - Hallenbeck, Gregory
AU - Jones, Michael G.
AU - Adams, Elizabeth A. K.
AU - Brinchmann, Jarle
AU - Chengalur, Jayaram N.
AU - Hunt, Leslie K.
AU - Masters, Karen L.
AU - Matsushita, Satoki
AU - Saintonge, Amelie
AU - Spekkens, Kristine
PY - 2014/9/20
Y1 - 2014/9/20
N2 - We present first results of the study of a set of exceptional H I sources identified in the 40% ALFALFA extragalactic H I survey catalog α.40 as both being H I massive ($M_{{\rm H}\,\scriptsize{I}} \gt 10^{10}\, M_\odot$) and having high gas fractions for their stellar masses: the HIghMass galaxy sample. We analyze UV- and optical-broadband and Hα images to understand the nature of their relatively underluminous disks in optical and to test whether their high gas fractions can be tracked to higher dark matter halo spin parameters or late gas accretion. Estimates of their star formation rates (SFRs) based on spectral energy distribution fitting agree within uncertainties with the Hα luminosity inferred current massive SFRs. The H II region luminosity functions, parameterized as dN/dlog LvpropL α, have standard slopes at the luminous end (α ~ –1). The global SFRs demonstrate that the HIghMass galaxies exhibit active ongoing star formation (SF) with moderate SF efficiency but, relative to normal spirals, a lower integrated SFR in the past. Because the SF activity in these systems is spread throughout their extended disks, they have overall lower SFR surface densities and lower surface brightness in the optical bands. Relative to normal disk galaxies, the majority of HIghMass galaxies have higher Hα equivalent widths and are bluer in their outer disks, implying an inside-out disk growth scenario. Downbending double exponential disks are more frequent than upbending disks among the gas-rich galaxies, suggesting that SF thresholds exist in the downbending disks, probably as a result of concentrated gas distribution.
AB - We present first results of the study of a set of exceptional H I sources identified in the 40% ALFALFA extragalactic H I survey catalog α.40 as both being H I massive ($M_{{\rm H}\,\scriptsize{I}} \gt 10^{10}\, M_\odot$) and having high gas fractions for their stellar masses: the HIghMass galaxy sample. We analyze UV- and optical-broadband and Hα images to understand the nature of their relatively underluminous disks in optical and to test whether their high gas fractions can be tracked to higher dark matter halo spin parameters or late gas accretion. Estimates of their star formation rates (SFRs) based on spectral energy distribution fitting agree within uncertainties with the Hα luminosity inferred current massive SFRs. The H II region luminosity functions, parameterized as dN/dlog LvpropL α, have standard slopes at the luminous end (α ~ –1). The global SFRs demonstrate that the HIghMass galaxies exhibit active ongoing star formation (SF) with moderate SF efficiency but, relative to normal spirals, a lower integrated SFR in the past. Because the SF activity in these systems is spread throughout their extended disks, they have overall lower SFR surface densities and lower surface brightness in the optical bands. Relative to normal disk galaxies, the majority of HIghMass galaxies have higher Hα equivalent widths and are bluer in their outer disks, implying an inside-out disk growth scenario. Downbending double exponential disks are more frequent than upbending disks among the gas-rich galaxies, suggesting that SF thresholds exist in the downbending disks, probably as a result of concentrated gas distribution.
KW - galaxies: evolution
KW - galaxies: fundamental parameters
KW - galaxies: ISM
KW - galaxies: star formation
U2 - 10.1088/0004-637X/793/1/40
DO - 10.1088/0004-637X/793/1/40
M3 - Article
SN - 0004-637X
VL - 793
SP - 1
EP - 36
JO - The Astrophysical Journal
JF - The Astrophysical Journal
IS - 1
ER -