An evolutionary model of star formation for elliptical galaxies.
Abstract
An evolutionary model of an elliptical galaxy with a continuous efficient star-formation rate depending on the gas density appears to explain the strong ultraviolet (UV) excess of two elliptical galaxies, NGC 4486 (M87) and NGC 4649, in the Virgo Cluster. The initial mass function is standard. The synthetic spectrum fits the far-UV to visible spectra of galaxies at age 13 Gyr. The present star formation rate is 1.2 x 10^-3^ M_sun_ Gyr^-1^ x (mass/M_sun_). We show that it is compatible with the mass deposition rate in the inner parts of galaxies, estimated from cooling-flows detected by X-rays with the Einstein Observatory HRI. This so-called UV-hot model also reproduces the Lyα (1215 A) emission line of distant star-forming galaxies at ages between ~0.3-4 Gyr, depending on the cosmological model adopted. The presence of hot coronae or plasmas in such galaxies supports the idea of a closed-box model, although this model cannot be applied to the brightest cluster members or the reddest galaxies of clusters at very high redshifts, which probably have a different history.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 1989
- DOI:
- 10.1093/mnras/236.1.47
- Bibcode:
- 1989MNRAS.236...47R
- Keywords:
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- Elliptical Galaxies;
- Galactic Evolution;
- Star Formation;
- Gas Density;
- Lyman Alpha Radiation;
- Ultraviolet Radiation;
- Astrophysics