|
| | | | |
| | | |
| Stat |
Members: 3645
Articles: 2'500'096
Articles rated: 2609
18 April 2024 |
|
| | | | |
|
Article overview
| |
|
|
Predominantly Low Metallicities Measured in a Stratified Sample of Lyman Limit Systems at z=3.7 | | Ana Glidden
; Thomas J. Cooper
; Kathy L. Cooksey
; Robert A. Simcoe
; John M. O'Meara
; | | Date: |
7 Apr 2016 | | Abstract: | We analyzed metallicities for 33 z=3.4-4.2 absorption line systems with large
neutral hydrogen column densities, drawn from a sample of H I-selected of Lyman
limit systems (LLSs) identified in Sloan Digital Sky Survey (SDSS) quasar
spectra, and stratified based on metal line features. We obtained
higher-resolution spectra with the Keck Echellette Spectrograph and Imager
(ESI), selecting targets according to our stratification scheme in an effort to
fully sample the LLS population metallicity distribution. We established a
plausible range of H I column densities and measured the metal column densities
(or limits) for ions of carbon, silicon, and aluminum. With simulations, we
found ionization-corrected metallicities or upper limits, when appropriate.
Interestingly, our ionization models were better constrained with enhanced
{alpha}-to-aluminum abundances, with a median abundance ratio of
[{alpha}/Al]=0.3. Measured metallicities were generally low, ranging from
[M/H]=-3 to -1.68, with even lower metallicities likely for some systems with
upper limits. We constructed the cumulative distribution function (CDF) for the
metallicity of the LLS population, using survival statistics to incorporate
information from limits. Recent models of galaxy evolution propose that
galaxies replenish their gas from the low-metallicity intergalactic medium
(IGM) via high-density H I "flows" and eject enriched interstellar gas via
outflows. Thus, there has been some expectation that LLSs at the peak of cosmic
star formation (z~3) might have a bimodal metallicity distribution. We modeled
our CDF as a mix of two Gaussian distributions, one reflecting the metallicity
of the IGM and the other representative of the interstellar medium of
star-forming galaxies. This bimodal distribution yielded a poor fit. A single
Gaussian distribution better represented the sample with a low mean metallicity
of [M/H]~-2.5. | | Source: | arXiv, 1604.2144 | | Services: | Forum | Review | PDF | Favorites | |
|
|
No review found.
Did you like this article?
Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.
browser claudebot
|
| |
|
|
|
|
News, job offers and information for researchers and scientists:
| |
REGISTER