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Title: HIghMass-high H I mass, H I-rich galaxies at z ∼ 0 sample definition, optical and Hα imaging, and star formation properties

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{sub HI}>10{sup 10} M{sub ⊙}) 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 L∝L {sup 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,more » 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.« less
Authors:
;  [1] ; ; ; ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8]
  1. Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, National Taiwan University, Taipei 10617, Taiwan (China)
  2. Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States)
  3. Sterrewacht Leiden, Leiden University, NL-2300 RA Leiden (Netherlands)
  4. National Centre for Radio Astrophysics, Tata Institute for Fundamental Research, Pune 411007 (India)
  5. INAF-Osservatorio Astrofisico di Arcetri, Largo East Fermi 5, I-50125, Firenze (Italy)
  6. Institute of Cosmology and Gravitation, Dennis Sciama Building, Burnaby Road, Portsmouth POI 3FX (United Kingdom)
  7. Department of Physics and Astronomy, University College London, Gower Place, London WC1E 6BT (United Kingdom)
  8. Royal Military College of Canada, Department of Physics, P.O. Box 17000, Station Forces, Kingston, ON K7K 7B4 (Canada)
Publication Date:
OSTI Identifier:
22365012
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFALFA; BRIGHTNESS; CATALOGS; DENSITY; DISTRIBUTION; EFFICIENCY; ENERGY SPECTRA; GALAXIES; IMAGES; LUMINOSITY; MASS; NONLUMINOUS MATTER; SPIN; STARS; SURFACES