Hubble and FUSE studies of Ly-alpha absorbers at low redshift
| dc.creator | Shull, J. Michael | |
| dc.date | 2001-07-25 | |
| dc.date.accessioned | 2026-07-07T01:59:26Z | |
| dc.date.available | 2026-07-07T01:59:26Z | |
| dc.description | Ultraviolet spectrographs aboard the Hubble Space Telescope (HST) and the Far Ultraviolet Spectroscopic Explorer (FUSE) have proved their value as sensitive probes of the low-density intergalactic medium (IGM) at low redshifts (z < 0.1). Recent observations in Ly-alpha, Ly-beta, and occasional higher Lyman lines show that warm photoionized gas in the low-z IGM may contain 20-25% of the baryons, with a N(HI)^-1.8 distribution in column density. Measurements of resonance lines of Si III, C III, C IV, and O VI suggest that the metallicity of these absorbers ranges from 1-10% of solar abundance down to values below 0.003 Z(solar). A comparison of Ly-beta/Ly-alpha ratios (FUSE and HST) yields a distribution of Doppler parameters with mean b = 31.4 +/- 7.4 km/s and median 28 km/s, comparable to values at z = 2-3. The curve-of-growth (CoG) b-values are considerably less than widths derived from Ly-alpha profile fitting, with mean b(CoG)/b(width) = 0.52, which suggests that low-z absorbers contain sizable non-thermal motions or velocity components arising from cosmological expansion and infall. A challenge for future UV spectroscopic missions (HST/COS and SUVO) is to obtain precision measurements of Omega(IGM) and metallicities for the strong Ly-alpha absorbers that dominate the IGM baryon content. This program will require accurate determinations of: (1) curves of growth using higher Lyman series lines; (2) the ionizing radiation field at 1-5 Ryd; and (3) characteristic sizes and shapes of the absorbers. | |
| dc.description | 12 pages, 6 figures. To appear in "Extragalactic Gas at Low Redshift" (ASP Conf. Series, Weymann Conf.) | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0107473 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0107473 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/3111 | |
| dc.subject | Astrophysics | |
| dc.title | Hubble and FUSE studies of Ly-alpha absorbers at low redshift | |
| dc.type | text |