The Nature of the Low-redshift Ly-alpha Clouds
| dc.creator | Shull, J. Michael | |
| dc.date | 1997-09-11 | |
| dc.date.accessioned | 2026-07-07T02:24:12Z | |
| dc.date.available | 2026-07-07T02:24:12Z | |
| dc.description | I discuss recent HST observations and interpretation of low-z Ly-alpha clouds toward nearby Seyferts and QSOs, including their frequency, space density, estimated mass, association with galaxies, and contribution to Omega_b. Our HST/GHRS detections of 73 Lya absorbers with N_HI > 10^12.6 cm^(-2) along 11 sightlines covering pathlength Delta(cz) = 86,000 km/s show f(>N_HI) proportional to N_HI^(-0.6 +/- 0.2). A group of strong absorbers toward PKS~2155-304 may be associated with gas (400-800)/h_75 kpc from 4 large galaxies with low metallicity (<0.004 solar) and D/H < 2 x 10^-4. At low-z, we derive a metagalactic ionizing radiation field and Lya-forest baryon density J_0 = (1.1 +/- 0.4) x 10^(-23) ergs/cm^2/s/Hz/sr and Omega_b = (0.008 +/- 0.004) h_75^(-1) [J_-23 N_14 b_100]^0.5 for clouds of characteristic size b = (100 kpc)b_100. | |
| dc.description | 8 pages LATEX, with 5 PostScript figures, conf_iap.sty To appear in Proceedings of 13th IAP (Paris) Colloquium, (July 1-5, 1997) Structure and Evolution of the IGM from QSO Absorption Lines, ed. P. Petitjean, S. Charlot | |
| dc.identifier | https://arxiv.org/abs/astro-ph/9709109 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/9709109 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/11530 | |
| dc.subject | Astrophysics | |
| dc.title | The Nature of the Low-redshift Ly-alpha Clouds | |
| dc.type | text |