THE YOUNG STELLAR POPULATION OF THE NEARBY LATE-TYPE GALAXY NGC 1311

Journal Article · Mon Nov 15 04:00:00 EST 2010 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/140/5/1137· OSTI ID:21443214

Eskridge, Paul B ^[1]; Windhorst, Rogier A; Jansen, Rolf A ^[2]

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1. Department of Physics and Astronomy, Minnesota State University, Mankato, MN 56001 (United States)
2. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)

We have extracted point-spread-function-fitted stellar photometry from near-ultraviolet, optical, and near-infrared images, obtained with the Hubble Space Telescope, of the nearby (D {approx} 5.5 Mpc) SBm galaxy NGC 1311. The ultraviolet and optical data reveal a population of hot main-sequence (MS) stars with ages of 2-10 Myr. We also find populations of blue supergiants with ages between 10 and 40 Myr and red supergiants with ages between 10 and 100 Myr. Our near-infrared data show evidence of star formation going back {approx}1 Gyr, in agreement with previous work. Fits to isochrones indicate a metallicity of Z {approx} 0.004. The ratio of blue to red supergiants is consistent with this metallicity. This indicates that NGC 1311 follows the well-known luminosity-metallicity relation for late-type dwarf galaxies. About half of the hot MS stars and blue supergiants are found in two regions in the inner part of NGC 1311. These two regions are each about 200 pc across, and thus have crossing times roughly equal to the 10 Myr age we find for the dominant young population. The luminosity functions of the supergiants indicate a slowly rising star formation rate ({approx}10{sup -3} M{sub sun} yr{sup -1}) from {approx}100 Myr ago until {approx}15 Myr ago, followed by a strong enhancement ({approx}10{sup -2} M{sub sun} yr{sup -1}) at {approx}10 Myr ago. We see no compelling evidence for gaps in the star-forming history of NGC 1311 over the last 100 Myr, and, with lower significance, none over the last Gyr. This argues against a bursting mode, and in favor of a gasping or breathing mode for the recent star formation history.

• OSTI ID: 21443214
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 5 Vol. 140; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ELECTROMAGNETIC RADIATION
GALAXIES
LUMINOSITY
OPTICAL PROPERTIES
PHOTOMETRY
PHYSICAL PROPERTIES
RADIATIONS
STARS
TELESCOPES
ULTRAVIOLET RADIATION