Star formation and selective dust extinction in luminous starburst galaxies

Citation
Bm. Poggianti et al., Star formation and selective dust extinction in luminous starburst galaxies, ASTROPHYS J, 550(1), 2001, pp. 195-203
Citations number
47
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004-637X → ACNP
Volume
550
Issue
1
Year of publication
2001
Part
1
Pages
195 - 203
Database
ISI
SICI code
0004-637X(20010320)550:1<195:SFASDE>2.0.ZU;2-K
Abstract
We investigate the star formation and dust extinction properties of very lu minous infrared galaxies whose spectra display a strong H delta line in abs orption and a moderate [O II] emission [e(a) spectrum]. This spectral combi nation has been suggested to be a useful method to identify dusty starburst galaxies at any redshift on the basis of optical data alone. We compare th e average e(a) optical spectrum with synthetic spectra that include both th e stellar and the nebular contribution, allowing dust extinction to affect differentially the stellar populations of different ages. We find that repr oducing the e(a) spectrum requires the youngest stellar generations to be s ignificantly more extinguished by dust than older stellar populations and i mplies a strong ongoing star formation activity at a level higher than in q uiescent spirals. A model fitting the optical spectrum does not necessarily produce the observed FIR luminosity, and this can be explained by the exis tence of stellar populations which are practically obscured at optical wave lengths. Models in which dust and stars are uniformly mixed yield a reddeni ng of the emerging emission lines which is too low compared to observations : additional foreground reddening is required.