The luminosities of bright H II regions in NGC 628 and its O star formation rate

Journal Article · Wed Aug 01 04:00:00 EDT 1990 · Astronomical Journal; (USA)

DOI:https://doi.org/10.1086/115524· OSTI ID:6478887

Von Hippel, T; Bothun, G ^[1]

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1. Michigan Univ., Ann Arbor (USA)

H-alpha photometric observations of the face-on Sc spiral galaxy NGC 628, obtained using 10-nm-bandwidth filters and a CCD detector on the 1.5-m Palomar telescope during October 1985, are reported and analyzed. Absolute luminosities are determined for 183 bright H II regions, and it is estimated that they contain clusters of about 100 young ionizing stars on average. Two theoretical models are constructed to explain the observed H II region luminosity function: in model (1) clusters differ only in the mass of gas involved in high-mass star formation and stellar evolution is ignored, while in model (2) clusters differ only in their state of evolution from initially identical conditions. Although both (1) and (2) can fit the observations, physical arguments are presented favoring (2), which also permits estimation of the slope of the massive-star initial mass function (near the Salpeter value of 2.35), the O-star formation rate (about 0.004/yr), the rate of type II SN (about 0.01/yr), and the number of WR stars in NGC 628 (about 800). 28 refs.

• OSTI ID: 6478887
• Journal Information: Astronomical Journal; (USA), Journal Name: Astronomical Journal; (USA) Vol. 100; ISSN 0004-6256; ISSN ANJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHARGE-COUPLED DEVICES
CONFIGURATION
COSMIC RADIO SOURCES
GALAXIES
H2 REGIONS
LUMINOSITY
MAIN SEQUENCE STARS
MASS
MATHEMATICAL MODELS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
POPULATIONS
PROTOSTARS
SEMICONDUCTOR DEVICES
SPIRAL CONFIGURATION
STAR CLUSTERS
STAR EVOLUTION
STARS
STELLAR ATMOSPHERES
WOLF-RAYET STARS