TY - JOUR
T1 - THE ACS LCID PROJECT. XI. on the EARLY TIME RESOLUTION of SFHs of LOCAL GROUP DWARF GALAXIES
T2 - COMPARING the EFFECTS of REIONIZATION in MODELS with OBSERVATIONS
AU - Aparicio, Antonio
AU - Hidalgo, Sebastian L.
AU - Skillman, Evan
AU - Cassisi, Santi
AU - Mayer, Lucio
AU - Navarro, Julio
AU - Cole, Andrew
AU - Gallart, Carme
AU - Monelli, Matteo
AU - Weisz, Daniel
AU - Bernard, Edouard
AU - Dolphin, Andrew
AU - Stetson, Peter
N1 - Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.
PY - 2016/5/20
Y1 - 2016/5/20
N2 - The analysis of the early star formation history (SFH) of nearby galaxies, obtained from their resolved stellar populations, is relevant as a test for cosmological models. However, the early time resolution of observationally derived SFHs is limited by several factors. Thus, direct comparison of observationally derived SFHs with those derived from theoretical models of galaxy formation is potentially biased. Here we investigate and quantify this effect. For this purpose, we analyze the duration of the early star formation activity in a sample of four Local Group dwarf galaxies and test whether they are consistent with being true fossils of the pre-reionization era; i.e., if the quenching of their star formation occurred before cosmic reionization by UV photons was completed. Two classical dSph (Cetus and Tucana) and two dTrans (LGS-3 and Phoenix) isolated galaxies with total stellar masses between 1.3 × 106 and 7.2 × 106 M⊙ have been studied. Accounting for time resolution effects, the SFHs peak as much as 1.25 Gyr earlier than the optimal solutions. Thus, this effect is important for a proper comparison of model and observed SFHs. It is also shown that none of the analyzed galaxies can be considered a true fossil of the prereionization era, although it is possible that the outer regions of Cetus and Tucana are consistent with quenching by reionization.
AB - The analysis of the early star formation history (SFH) of nearby galaxies, obtained from their resolved stellar populations, is relevant as a test for cosmological models. However, the early time resolution of observationally derived SFHs is limited by several factors. Thus, direct comparison of observationally derived SFHs with those derived from theoretical models of galaxy formation is potentially biased. Here we investigate and quantify this effect. For this purpose, we analyze the duration of the early star formation activity in a sample of four Local Group dwarf galaxies and test whether they are consistent with being true fossils of the pre-reionization era; i.e., if the quenching of their star formation occurred before cosmic reionization by UV photons was completed. Two classical dSph (Cetus and Tucana) and two dTrans (LGS-3 and Phoenix) isolated galaxies with total stellar masses between 1.3 × 106 and 7.2 × 106 M⊙ have been studied. Accounting for time resolution effects, the SFHs peak as much as 1.25 Gyr earlier than the optimal solutions. Thus, this effect is important for a proper comparison of model and observed SFHs. It is also shown that none of the analyzed galaxies can be considered a true fossil of the prereionization era, although it is possible that the outer regions of Cetus and Tucana are consistent with quenching by reionization.
KW - early universe
KW - galaxies: dwarf
KW - galaxies: evolution
KW - galaxies: photometry
KW - galaxies: stellar content
KW - galaxies: structure
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U2 - 10.3847/0004-637X/823/1/9
DO - 10.3847/0004-637X/823/1/9
M3 - Article
AN - SCOPUS:84971577133
SN - 0004-637X
VL - 823
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 9
ER -