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THE ACS LCID Project.III. The Star Formation History of the Cetus dSph Galaxy: A Post-Reionization Fossil


Monelli, M and Hidalgo, SL and Stetson, PB and Aparicio, A and Gallart, C and Dolphin, AE and Cole, AA and Weisz, DR and Skillman, ED and Bernard, EJ and Mayer, L and Navarro, JF and Cassisi, S and Drozdovsky, I and Tolstoy, E, THE ACS LCID Project.III. The Star Formation History of the Cetus dSph Galaxy: A Post-Reionization Fossil, Astrophysical Journal, 720, (2) pp. 1225-1245. ISSN 0004-637X (2010) [Refereed Article]

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© 2010 The American Astronomical Society

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DOI: doi:10.1088/0004-637X/720/2/1225


We use deep HST/ACS observations to calculate the star formation history (SFH) of the Cetus dwarf spheroidal (dSph) galaxy. Our photometry reaches below the oldest main-sequence turnoffs, which allows us to estimate the age and duration of the main episode of star formation in Cetus. This is well approximated by a single episode that peaked roughly 12 +/- 0.5 Gyr ago and lasted no longer than about 1.9 +/- 0.5 Gyr (FWHM). Our solution also suggests that essentially no stars formed in Cetus during the past 8 Gyr. This makes Cetus' SFH comparable to that of the oldest Milky Way dSphs. Given the current isolation of Cetus in the outer fringes of the Local Group, the dominant old population implies that Cetus is a clear outlier in the morphology-Galactocentric distance relation that holds for the majority of the Milky Way dwarf satellites. Our results also show that Cetus continued forming stars until z 1, long after the universe was reionized, and that there is no clear signature of the epoch of reionization in Cetus' SFH. We briefly discuss the implications of these results for dwarf galaxy evolution models. Finally, we present a comprehensive account of the data reduction and analysis strategy adopted for all galaxies targeted by the LCID (Local Cosmology from Isolated Dwarfs) project. We employ two different photometry codes (DAOPHOT/ALLFRAME and DOLPHOT), three different SFH reconstruction codes (IAC-pop/MinnIAC, MATCH, and COLE), and two stellar evolution libraries (BaSTI and Padova/Girardi), allowing for a detailed assessment of the modeling and observational uncertainties.

Item Details

Item Type:Refereed Article
Keywords:galaxies: evolution – galaxies: individual (Cetus) – galaxies: photometry – galaxies: stellar content
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Cole, AA (Professor Andrew Cole)
ID Code:65222
Year Published:2010
Web of Science® Times Cited:120
Deposited By:Physics
Deposited On:2010-10-15
Last Modified:2022-07-07

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