THE ACS LCID PROJECT. III. THE STAR FORMATION HISTORY OF THE CETUS dSph GALAXY: A POST-REIONIZATION FOSSIL

Monelli, M.; Hidalgo, Sebastián L.; Stetson, P. B.; Aparicio, A.; Gallart, Carme; Dolphin, Andrew E.; Cole, A. A.; Weisz, Daniel R.; Skillman, Evan D.; Bernard, Edouard J.; Mayer, Lucio; Navarro, Julio F.; Cassisi, S.; Drozdovsky, I.; Tolstoy, Eline

doi:10.1088/0004-637x/720/2/1225

Cited by 160 publications

(194 citation statements)

References 81 publications

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“…Although some such CMDs are available within the LG sample, none are present for the more distance galaxies in the ANGST sample. Thus, while the two samples are generally comparable in their cumulative SFHs, studies of the detailed ancient SFHs indicate that galaxies can show wide variation in their patterns of star formation at the oldest epochs (e.g., Cole et al 2007;Monelli et al 2010aMonelli et al , 2010b. These early variations may show correlations with environment or other galaxy properties.…”

Section: Measuring the Star Formation Historiesmentioning

confidence: 98%

“…Five of the LG dwarfs (Cetus, Tucana, IC 1613, Leo A, and LGS3) were more recently observed with ACS as part of the Local Cosmology with Isolated Dwarfs program (LCID; Gallart et al 2007) and have significantly deeper CMDs compared to the corresponding WFPC2 photometry (e.g., Cole et al 2007;Monelli et al 2010aMonelli et al , 2010b. Photometry of ACS observations was performed with DOLPHOT, 12 an update of HSTPHOT with an ACS specific module, which allows us to include these five SFHs without compromising uniformity.…”

Section: The Local Group Dwarf Galaxy Samplementioning

confidence: 99%

“…Specifically, we chose a single power-law stellar IMF with a spectral index of −1.30 with mass limits of 0.1 to 120 M and a binary fraction of 0.35. Due to age-metallicity degeneracies in relatively shallow CMDs (e.g., Gallart et al 2005;Cole et al 2005), we required that the metallicity increase as a monotonic function of time, except in the case of the LCID galaxies, where chemical evolution was well determined without this constraint (e.g., Gallart et al 2005;Cole et al 2007;Monelli et al 2010aMonelli et al , 2010bHidalgo et al 2011).…”

Section: Measuring the Star Formation Historiesmentioning

confidence: 99%

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How Typical Are the Local Group Dwarf Galaxies?

Weisz¹,

Dolphin²,

Dalcanton³

et al. 2011

ApJ

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We compare the cumulative star formation histories (SFHs) of Local Group (LG) dwarf galaxies with those in the volume-limited ACS Nearby Galaxy Survey Treasury (ANGST) sample (D 4 Mpc), in order to understand how typical the LG dwarf galaxies are relative to those in the nearby universe. The SFHs were derived in a uniform manner from high-quality optical color-magnitude diagrams constructed from Hubble Space Telescope imaging. We find that the mean cumulative SFHs of the LG dwarfs are comparable to the mean cumulative SFHs of the ANGST sample for the three different morphological types (dwarf spheroidals/ellipticals: dSph/dE; dwarf irregulars: dI; transition dwarfs: dTrans). We also discuss effects such as population gradients and systematic uncertainties in the stellar models that may influence the derived SFHs. Both the ANGST and LG dwarf galaxies show a consistent and strong morphology-density relationship, emphasizing the importance of environment in the evolution of dwarf galaxies. Specifically, we confirm that dIs are found at lower densities and higher luminosities than dSphs, within this large sample. We also find that dTrans are located in similar environments to those occupied by dwarf irregular galaxies, but have systematically lower luminosities that are more comparable to those of dwarf spheroidals. The similarity of the SFHs and morphology-density relationships of the LG and ANGST dwarf galaxies suggests that the LG dwarfs are a good representation of dwarf galaxies in the local universe.

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Section: Measuring the Star Formation Historiesmentioning

confidence: 98%

Section: The Local Group Dwarf Galaxy Samplementioning

confidence: 99%

Section: Measuring the Star Formation Historiesmentioning

confidence: 99%

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How Typical Are the Local Group Dwarf Galaxies?

Weisz¹,

Dolphin²,

Dalcanton³

et al. 2011

ApJ

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“…They are not currently forming stars and show prominent old stellar populations, but their star formation histories (SFHs) are not uniformly old (see the recent reviews of Tolstoy et al 2009;Weisz et al 2014). Indeed, dSphs show a wide variety of SFHs; from systems that essentially completed forming their stars ∼ 10 Gyr ago, like Cetus and Draco (Monelli et al 2010;Aparicio et al 2001) to others where star formation was sustained over a long time and ceased only as recently as 6 Gyr ago (e.g., Leo II, Dolphin 2002) or even < 1 Gyr ago (e.g., Fornax, Stetson et al 1998;Saviane et al 2000;Battaglia et al 2006;de Boer et al 2012, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Mergers and the outside-in formation of dwarf spheroidals

Benítez-Llambay¹,

Navarro²,

Abadi³

et al. 2015

Mon. Not. R. Astron. Soc.

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We use a cosmological simulation of the formation of the Local Group to explore the origin of age and metallicity gradients in dwarf spheroidal galaxies. We find that a number of simulated dwarfs form "outside-in", with an old, metal-poor population that surrounds a younger, more concentrated metal-rich component, reminiscent of dwarf spheroidals like Sculptor or Sextans. We focus on a few examples where stars form in two populations distinct in age in order to elucidate the origin of these gradients. The spatial distributions of the two components reflect their diverse origin; the old stellar component is assembled through mergers, but the young population forms largely in situ. The older component results from a first episode of star formation that begins early but is quickly shut off by the combined effects of stellar feedback and reionization. The younger component forms when a late accretion event adds gas and reignites star formation. The effect of mergers is to disperse the old stellar population, increasing their radius and decreasing their central density relative to the young population. We argue that dwarf-dwarf mergers offer a plausible scenario for the formation of systems with multiple distinct populations and, more generally, for the origin of age and metallicity gradients in dwarf spheroidals.

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“…The aim of this project is to recover the full SFHs of six isolated dwarf galaxies of the Local Group: Phoenix, LGS-3, Cetus, Tucana, IC1613, and Leo-A, which have been already described in [4][5][6][7]10], and [2]. We have selected a subsample of the dwarf galaxies of the LCID project to obtain the SFH as a function of radius: two transition galaxies (Phoenix and LGS-3) and two dSph galaxies (Cetus and Tucana).…”

Section: Introductionmentioning

confidence: 99%