|
| | | | |
| | | |
| Stat |
Members: 3645
Articles: 2'506'133
Articles rated: 2609
27 April 2024 |
|
| | | | |
|
Article overview
| |
|
|
The Incidence of Low-Metallicity Lyman-Limit Systems at z~3.5: Implications for the Cold-Flow Hypothesis of Baryonic Accretion | | Thomas J. Cooper
; Robert A. Simcoe
; Kathy L. Cooksey
; John M. O'Meara
; Paul Torrey
; | | Date: |
22 May 2015 | | Abstract: | Cold accretion is a primary growth mechanism of simulated galaxies, yet
observational evidence of "cold flows" at redshifts where they should be most
efficient ($z=2$-4) is scarce. In simulations, cold streams manifest as
Lyman-limit absorption systems (LLSs) with low heavy-element abundances similar
to those of the diffuse IGM. Here we report on an abundance survey of 17 H
I-selected LLSs at $z=3.2$-4.4 which exhibit no metal absorption in SDSS
spectra. Using medium-resolution spectra obtained at Magellan, we derive
ionization-corrected metallicities (or limits) with a Markov-Chain Monte Carlo
sampling that accounts for the large uncertainty in $N_{
m HI}$ measurements
typical of LLSs. The metal-poor LLS sample overlaps with the IGM in metallicity
and is best described by a model where $71^{+13}_{-11}\%$ are drawn from the
IGM chemical abundance distribution. These represent roughly half of all LLSs
at these redshifts, suggesting that 28-40$\%$ of the general LLS population at
$zsim3.7$ could trace unprocessed gas. An ancillary sample of ten LLSs without
any a priori metal-line selection is best fit with $48^{+14}_{-12}\%$ of
metallicities drawn from the IGM. We compare these results with regions of a
moving-mesh simulation; the simulation finds only half as many baryons in
IGM-metallicity LLSs, and most of these lie beyond the virial radius of the
nearest galaxy halo. A statistically significant fraction of all LLSs have low
metallicity and therefore represent candidates for accreting gas; large-volume
simulations can establish what fraction of these candidates actually lie near
galaxies and the observational prospects for detecting the presumed hosts in
emission. | | Source: | arXiv, 1505.6210 | | 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 Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
|
| |
|
|
|
|
News, job offers and information for researchers and scientists:
| |
REGISTER