A deep search for faint galaxies associated with very low-redshift C iv absorbers. II. Program design, absorption-line measurements, and absorber statistics
- Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003-9305 (United States)
- UCO/Lick Observatory, University of California, Santa Cruz, CA (United States)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
- Department of Chemistry and Physics, Saint Michaels College, One Winooski Park, Colchester, VT 05439 (United States)
- Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
To investigate the evolution of metal-enriched gas over recent cosmic epochs as well as to characterize the diffuse, ionized, metal-enriched circumgalactic medium, we have conducted a blind survey for C iv absorption systems in 89 QSO sightlines observed with the Hubble Space Telescope Cosmic Origins Spectrograph. We have identified 42 absorbers at z < 0.16, comprising the largest uniform blind sample size to date in this redshift range. Our measurements indicate an increasing C iv absorber number density per comoving path length (dN/dX= 7.5 ± 1.1) and modestly increasing mass density relative to the critical density of the universe (Ω{sub C iv} = 10.0 ± 1.5 × 10{sup −8}) from z ∼ 1.5 to the present epoch, consistent with predictions from cosmological hydrodynamical simulations. Furthermore, the data support a functional form for the column density distribution function that deviates from a single power law, also consistent with independent theoretical predictions. As the data also probe heavy element ions in addition to C iv at the same redshifts, we identify, measure, and search for correlations between column densities of these species where components appear to be aligned in velocity. Among these ion–ion correlations, we find evidence for tight correlations between C ii and Si ii, C ii and Si iii, and C iv and Si iv, suggesting that these pairs of species arise in similar ionization conditions. However, the evidence for correlations decreases as the difference in ionization potential increases. Finally, when controlling for observational bias, we find only marginal evidence for a correlation (86.8% likelihood) between the Doppler line width b(C iv) and column density N(C iv).
- OSTI ID:
- 22882350
- Journal Information:
- Astrophysical Journal, Vol. 815, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
Similar Records
A deep search for faint galaxies associated with very low redshift C iv absorbers. III. The mass- and environment-dependent circumgalactic medium
Tracing the cosmic metal evolution in the low-redshift intergalactic medium