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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 710219.0, MPI für Astronomie / Publikationen_mpia
Evidence of very low metallicity and high ionization state in a strongly lensed, star-forming dwarf galaxy at z= 3.417
Authors:Amorín, R.; Grazian, A.; Castellano, M.; Pentericci, L.; Fontana, A.; Sommariva, V.; van der Wel, A.; Maseda, M.; Merlin, E.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:The Astrophysical Journal Letters
Issue / Number:1
Start Page:id. L4 (5 pp)
Audience:Not Specified
Abstract / Description:We investigate the gas-phase metallicity and Lyman continuum (LyC) escape fraction of a strongly gravitationally lensed, extreme emission-line galaxy at z = 3.417, J1000+0221S, recently discovered by the CANDELS team. We derive ionization- and metallicity-sensitive emission-line ratios from H+K band Large Binocular Telescope (LBT)/LUCI medium resolution spectroscopy. J1000+0221S shows high ionization conditions, as evidenced by its enhanced [O III]/[O II] and [O III]/Hbeta ratios. Strong-line methods based on the available line ratios suggest that J1000+0221S is an extremely metal-poor galaxy, with a metallicity of 12+log (O/H) < 7.44 (Z < 0.05 Z &sun;), placing it among the most metal-poor star-forming galaxies at z gsim 3 discovered so far. In combination with its low stellar mass (2 × 108 M &sun;) and high star formation rate (5 M &sun; yr-1), the metallicity of J1000+0221S is consistent with the extrapolation of the mass-metallicity relation traced by Lyman-break galaxies at z gsim 3 to low masses, but it is 0.55 dex lower than predicted by the fundamental metallicity relation at z lsim 2.5. These observations suggest a rapidly growing galaxy, possibly fed by massive accretion of pristine gas. Additionally, deep LBT/LBC photometry in the UGR bands are used to derive a limit to the LyC escape fraction, thus allowing us to explore for the first time the regime of sub-L* galaxies at z > 3. We find a 1sigma upper limit to the escape fraction of 23%, which adds a new observational constraint to recent theoretical models predicting that sub-L* galaxies at high-z have high escape fractions and thus are the responsible for the reionization of the universe. Based on Large Binocular Telescope (LBT) observations.
Free Keywords:galaxies: abundances; galaxies: dwarf; galaxies: evolution; galaxies: fundamental parameters; galaxies: high-redshift; galaxies: starburst; gravitational lensing: strong
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/2041-8205/788/1/L4
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