Science-advisor
REGISTER info/FAQ
Login
username
password
     
forgot password?
register here
 
Research articles
  search articles
  reviews guidelines
  reviews
  articles index
My Pages
my alerts
  my messages
  my reviews
  my favorites
 
 
Stat
Members: 3643
Articles: 2'488'730
Articles rated: 2609

29 March 2024
 
  » arxiv » 1208.3260

 Article overview


First Spectroscopic Evidence for High Ionization State and Low Oxygen Abundance in Lya Emitters
Kimihiko Nakajima ; Masami Ouchi ; Kazuhiro Shimasaku ; Takuya Hashimoto ; Yoshiaki Ono ; Janice C. Lee ;
Date 16 Aug 2012
AbstractWe present results from Keck/NIRSPEC and Magellan/MMIRS follow-up spectroscopy of Lya emitters (LAEs) at z=2.2 identified in our Subaru narrowband survey. We successfully detect Ha emission from seven LAEs, and perform a detailed analysis of six LAEs free from AGN activity, two out of which, CDFS-3865 and COSMOS-30679, have [OII] and [OIII] line detections. They are the first [OII]-detected LAEs at high-z, and their [OIII]/[OII] ratios and R23-indices provide the first simultaneous determinations of ionization parameter and oxygen abundance for LAEs. CDFS-3865 has a very high ionization parameter (q_{ion}=2.4^{+2.0}_{-0.9}x10^8 cm s^{-1}) and a low oxygen abundance (12+log(O/H)=7.84^{+0.24}_{-0.25}) in contrast with moderate values of other high-z galaxies such as Lyman-break galaxies (LBGs). COSMOS-30679 also possesses a relatively high ionization parameter (q_{ion}=(3.4-15)x10^7 cm s^{-1}) and a low oxygen abundance (12+log(O/H)=8.08-8.67), and falls below the mass-metallicity relation of z~2 LBGs. Similarly, a low metallicity of 12+log(O/H)<8.4 is independently indicated for typical LAEs from a composite spectrum and the [NII]/Ha index. Such high ionization parameters and low oxygen abundances can be found in local star-forming galaxies, but this extreme local population occupies only <0.3% of the SDSS spectroscopic galaxy sample with a number density >10 times smaller than that of LAEs. With their high ionization parameters and low oxygen abundances, LAEs would represent an early stage of galaxy formation dominated by massive stars in compact star-forming regions. Thus, low-mass galaxies such as LAEs produce ionizing photons efficiently probably with a high escape fraction achieved by density-bounded HII regions, which would significantly contribute to cosmic reionization at z>6. (abriged)
Source arXiv, 1208.3260
Services Forum | Review | PDF | Favorites   
 
Visitor rating: did you like this article? no 1   2   3   4   5   yes

No review found.
 Did you like this article?

This article or document is ...
important:
of broad interest:
readable:
new:
correct:
Global appreciation:

  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






ScienXe.org
» my Online CV
» Free


News, job offers and information for researchers and scientists:
home  |  contact  |  terms of use  |  sitemap
Copyright © 2005-2024 - Scimetrica