STAR-FORMING OR STARBURSTING? THE ULTRAVIOLET CONUNDRUM

Journal Article · Fri Nov 20 00:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/706/1/553· OSTI ID:21378181

Boquien, M; Calzetti, D; Hong, S ^[1]; Kennicutt, R ^[2]; Dale, D ^[3]; Engelbracht, C; Portouw, J ^[4]; Gordon, K D ^[5]

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1. University of Massachusetts, Department of Astronomy, LGRT-B 619E, Amherst, MA 01003 (United States)
2. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
3. Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States)
4. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
5. STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

Compared to starburst galaxies, normal star-forming galaxies have been shown to display a much larger dispersion of the dust attenuation at fixed reddening through studies of the IRX-beta diagram (the IR/UV ratio 'IRX' versus the UV color 'beta'). To investigate the causes of this larger dispersion and attempt to isolate second parameters, we have used GALEX UV, ground-based optical, and Spitzer infrared imaging of eight nearby galaxies, and examined the properties of individual UV and 24 mum selected star-forming regions. We concentrated on star-forming regions, in order to isolate simpler star formation histories than those that characterize whole galaxies. We find that (1) the dispersion is not correlated with the mean age of the stellar populations; (2) a range of dust geometries and dust extinction curves are the most likely causes for the observed dispersion in the IRX-beta diagram, (3) together with some potential dilution of the most recent star-forming population by older unrelated bursts, at least in the case of star-forming regions within galaxies; and (4) we also recover some general characteristics of the regions, including a tight positive correlation between the amount of dust attenuation and the metal content. Although generalizing our results to whole galaxies may not be immediate, the possibility of a range of dust extinction laws and geometries should be accounted for in the latter systems as well.

• OSTI ID: 21378181
• Journal Information: Astrophysical Journal, Vol. 706, Issue 1; Other Information: DOI: 10.1088/0004-637X/706/1/553; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COLOR
DIAGRAMS
DILUTION
DISPERSIONS
DUSTS
GALAXIES
GEOMETRY
METALS
STARS
ULTRAVIOLET RADIATION
ELECTROMAGNETIC RADIATION
ELEMENTS
INFORMATION
MATHEMATICS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS