THE ACS LCID PROJECT. XI. ON THE EARLY TIME RESOLUTION OF SFHs OF LOCAL GROUP DWARF GALAXIES: COMPARING THE EFFECTS OF REIONIZATION IN MODELS WITH OBSERVATIONS
- Instituto de Astrofísica de Canarias, Vía Láctea s/n, E38200—La Laguna, Tenerife, Canary Islands (Spain)
- INAF–Osservatorio Astronomico di Collurania, Teramo (Italy)
- Department of Physics, Institut für Astronomie, ETH Zürich, Zürich (Switzerland)
- Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States)
- School of Physical Sciences, University of Tasmania, Hobart, Tasmania (Australia)
- Astronomy Department, Box 351580, University of Washington, Seattle, WA 92895 (United States)
- Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)
- Raytheon, 1151 East Hermans Road, Tucson, AZ 85706 (United States)
- Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)
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 1.3×10{sup 6} and 7.2×10{sup 6} M{sub ⊙} 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 pre-reionization era, although it is possible that the outer regions of Cetus and Tucana are consistent with quenching by reionization.
- OSTI ID:
- 22862937
- Journal Information:
- Astrophysical Journal, Vol. 823, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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