A Window on the Earliest Star Formation: Extreme Photoionization Conditions of a High-ionization, Low-metallicity Lensed Galaxy at z similar to 2
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A Window on the Earliest Star Formation : Extreme Photoionization Conditions of a High-ionization, Low-metallicity Lensed Galaxy at z similar to 2. / Berg, Danielle A.; Erb, Dawn K.; Auger, Matthew W.; Pettini, Max; Brammer, Gabriel B.
In: Astrophysical Journal, Vol. 859, No. 2, 164, 01.06.2018.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - A Window on the Earliest Star Formation
T2 - Extreme Photoionization Conditions of a High-ionization, Low-metallicity Lensed Galaxy at z similar to 2
AU - Berg, Danielle A.
AU - Erb, Dawn K.
AU - Auger, Matthew W.
AU - Pettini, Max
AU - Brammer, Gabriel B.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - We report new observations of SL2S J021737-051329, a lens system consisting of a bright arc at z = 1.84435, magnified similar to 17 x by a massive galaxy at z = 0.65. SL2S0217 is a low-mass (M <10(9) M-circle dot, low-metallicity (Z similar to 1/20 Z(circle dot)) galaxy, with extreme star-forming conditions that produce strong nebular UV emission lines in the absence of any apparent outflows. Here we present several notable features from rest-frame UV Keck/LRIS spectroscopy: (1) Very strong narrow emission lines are measured for C IV lambda lambda 1548, 1550, He II lambda 1640, O III lambda lambda 1661, 1666, Si III] lambda lambda 1883, 1892, and C lambda lambda 1907, 1909. (2) Double-peaked Ly alpha emission is observed with a dominant blue peak and centered near the systemic velocity. (3) The low- and high-ionization absorption features indicate very little or no outflowing gas along the sight line to the lensed galaxy. The relative emission-line strengths can be reproduced with a very high ionization, low-metallicity starburst with binaries, with the exception of He II, which indicates that an additional ionization source is needed. We rule out large contributions from active galactic nuclei and shocks to the photoionization budget, suggesting that the emission features requiring the hardest radiation field likely result from extreme stellar populations that are beyond the capabilities of current models. Therefore, 5L250217 serves as a template for the extreme conditions that are important for reionization and thought to be more common in the early universe.
AB - We report new observations of SL2S J021737-051329, a lens system consisting of a bright arc at z = 1.84435, magnified similar to 17 x by a massive galaxy at z = 0.65. SL2S0217 is a low-mass (M <10(9) M-circle dot, low-metallicity (Z similar to 1/20 Z(circle dot)) galaxy, with extreme star-forming conditions that produce strong nebular UV emission lines in the absence of any apparent outflows. Here we present several notable features from rest-frame UV Keck/LRIS spectroscopy: (1) Very strong narrow emission lines are measured for C IV lambda lambda 1548, 1550, He II lambda 1640, O III lambda lambda 1661, 1666, Si III] lambda lambda 1883, 1892, and C lambda lambda 1907, 1909. (2) Double-peaked Ly alpha emission is observed with a dominant blue peak and centered near the systemic velocity. (3) The low- and high-ionization absorption features indicate very little or no outflowing gas along the sight line to the lensed galaxy. The relative emission-line strengths can be reproduced with a very high ionization, low-metallicity starburst with binaries, with the exception of He II, which indicates that an additional ionization source is needed. We rule out large contributions from active galactic nuclei and shocks to the photoionization budget, suggesting that the emission features requiring the hardest radiation field likely result from extreme stellar populations that are beyond the capabilities of current models. Therefore, 5L250217 serves as a template for the extreme conditions that are important for reionization and thought to be more common in the early universe.
KW - dark ages, reionization, first stars
KW - galaxies: abundances
KW - galaxies: evolution
KW - galaxies: ISM
KW - gravitational lensing: strong
KW - REST-FRAME ULTRAVIOLET
KW - GALACTIC CHEMICAL EVOLUTION
KW - EMISSION-LINE DIAGNOSTICS
KW - POPULATION-III STARS
KW - LY-ALPHA RADIATION
KW - BLACK-HOLE
KW - PHYSICAL-PROPERTIES
KW - FORMING GALAXIES
KW - RECOMBINATION LINES
KW - INTERSTELLAR-MEDIUM
U2 - 10.3847/1538-4357/aab7fa
DO - 10.3847/1538-4357/aab7fa
M3 - Journal article
VL - 859
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
M1 - 164
ER -
ID: 245614467