J. Lequeux — Page 2

arXiv1996

UV HST Spectroscopy of Star-Forming Galaxies

HST spectroscopical observations of 8 HII galaxies are reported. Ly alpha emission was detected in 4 of them. We find that the velocity structure of the gas is the main determining factor for the escape of the Ly alpha photons, and not the abundance of dust. The rest of the sample shows broad damped Ly alpha absorption attributed to large HI column densities, that is static with respect to the emitted Ly alpha photons, emerging from the HII regions. The star-forming galaxies IZW18 and even more SBS0335-052 may have extremely metal deficient HI clouds, the latter with [O/H] as low as -7.2.

astro-ph↗

arXiv1996

V- and I-band observations of the halo of NGC 5907

Using long exposures taken in the V and I bands with a 4096$\times$4096 pixel CCD array at the prime focus of the Canada-France-Hawaii telescope, we have confirmed the discovery by Sackett et al. (1994) of a flat, faint luminous halo around the edge-on Sc galaxy NGC$\thinspace$5907. This halo is redder than the disk. Its nature is still an observational challenge. We suggest however that its color can only be accounted for by stars less massive than 0.8 $M_{\odot}$. Their total mass in NGC$\thinspace$5907 is very uncertain, but it might possibly account for the excess dynamical mass in this galaxy. Alternatively their distribution might trace the dark potential without contributing signifi- cantly to the mass. We give upper limits to the extinction by an hypothetical dust in the halo.

astro-ph↗