THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I. HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS

By D. Weisz, A. Dolphin, E. Skillman, J. Holtzman, K. Gilbert, J. J. Dalcanton, B. Williams. 2014

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We present uniformly measured star formation histories (SFHs) of 40 Local Group (LG) dwarf galaxies based on color–magnitude diagram (CMD) analysis from archival Hubble Space Telescope imaging. We demonstrate that accurate SFHs can be recovered from CMDs that do not reach the oldest main sequence turn-off (MSTO), but emphasize that the oldest MSTO is critical for precisely constraining the earliest epochs of star formation. We find that: (1) the average lifetime SFHs of dwarf spheroidals (dSphs) can be approximated by an exponentially declining SFH with τ ∼ 5 Gyr; (2) lower luminosity dSphs are less likely to have extended SFHs than more luminous dSphs; (3) the average SFHs of dwarf irregulars (dIrrs), transition dwarfs, and dwarf ellipticals can be approximated by the combination of an exponentially declining SFH (τ ∼ 3–4 Gyr) for lookback ages >10–12 Gyr ago and a constant SFH thereafter; (4) the observed fraction of stellar mass formed prior to z = 2 ranges considerably (80% for galaxies with M < 105 M☉ to 30% for galaxies with M > 107 M☉) and is largely explained by environment; (5) the distinction between “ultra-faint” and “classical” dSphs is arbitrary; (6) LG dIrrs formed a significantly higher fraction of stellar mass prior to z = 2 than the Sloan Digital Sky Survey galaxies from Leitner and the SFHs from the abundance matching models of Behroozi et al. This may indicate higher than expected star formation efficiencies at early times in low mass galaxies. Finally, we provide all the SFHs in tabulated electronic format for use by the community.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6fe84620c7c5f07a4884e14ba80c41bf2787d4c6

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Citations in the corpus

The impact of baryonic physics on the structure of dark matter haloes: the view from the FIRE cosmological simulations (2015, background): “From the observations of dwarf galaxies in the Local Group, Weisz et al. (2014) show that a large fraction of dwarf galaxies have active late time star formations, especially for field galaxies and galaxies with M∗ > 106M .”
(Star)bursts of FIRE: observational signatures of bursty star formation in galaxies (2015, background): “…these fluctuations could be probed for local galaxies by analysing their resolved stellar populations (for recent examples of such analyses, see e.g. Weisz et al. 2008, 2011, 2014; Johnson et al. 2013; Williams et al. 2015). c© 2015 RAS, MNRAS 000, 1–18 c© 2015 RAS, MNRAS 000, 1–18 c© 2015 RAS,…”
FIRE in the field: Simulating the threshold of galaxy formation (2016, background): “…likely to serve as sensitive probes of reionization-induced feedback, which may contribute to the diversity of star formation histories observed for low-mass galaxies (e.g., Tolstoy et al. 2009; Skillman et al. 2014; Weisz et al. 2014; Brown et al. 2014; Gallart et al. 2015; Skillman et al. 2016).”
Farthest Neighbor: The Distant Milky Way Satellite Eridanus II (2016, background): “…dwarf galaxy located close to, but beyond, the virial radius of Milky Way, Eri II is a key object for studying environmental influences on low-mass galaxies and the quenching of star formation in such systems (Weisz et al. 2014; Wetzel et al. 2015; Wheeler et al. 2015; Fillingham et al. 2016).”
Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 (2019, background): “…et al. 2015, 2019; Munshi et al. 2019; Agertz et al. 2020), reionization and the first stars (e.g., Bullock et al. 2000; Shapiro et al. 2004; Weisz et al. 2014a,b; Boylan-Kolchin et al. 2015; Ishiyama et al. 2016; Weisz & Boylan-Kolchin 2017; Tollerud & Peek 2018; Graus et al. 2019; Katz et…”
Quenching and ram pressure stripping of simulated Milky Way satellite galaxies (2017, background): “E-mail: Christine.Simpson@h-its.org the high-redshift Universe by constraining these histories over 12 Gyr (e.g. Weisz et al. 2014).”
ETHOS - an effective theory of structure formation: dark matter physics as a possible explanation of the small-scale CDM problems (2015, background): “…required for supernovae feedback to dramatically alter the inner DM distribution, but such time resolution is still not possible for the dwarf galaxies that show the CDM problems (Weisz et al. 2014), although there is evidence that this process is indeed efficient at larger masses (Kauffmann 2014).”
BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES (2015, background): “…for multiple episodes of star formation separated by periods of quiescence ranging from a few 10’s of Myr to several Gyr (for example, Dolphin et al. 2003; Rizzi et al. 2004; Skillman 2005; Lianou & Cole 2013; de Boer et al. 2014; Weisz et al. 2014; VandenBerg et al. 2015; Geha et al. 2015).”
THE QUENCHING OF THE ULTRA-FAINT DWARF GALAXIES IN THE REIONIZATION ERA (2014, background): “…2009, 2010; Okamoto et al. 2008, 2010, 2012; de Jong et al. 2008b; Hughes et al. 2008; Martin et al. 2008a; Greco et al. 2008; Muñoz et al. 2010; Weisz et al. 2014b), while spectroscopy of their giant stars indicates low metallicities, but with a dispersion significantly larger than the…”
Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies (2015, background): “Observations of the star formation rate of dwarf galaxies (Tolstoy et al. 2009; Skillman et al. 2014; Weisz et al. 2014; Brown et al. 2014; Cole et al. 2014) show a relatively high dispersion for a fixed stellar mass, but all the histories of our simulated galaxies seem realistic when compared with…”
RECONCILING DWARF GALAXIES WITH ΛCDM COSMOLOGY: SIMULATING A REALISTIC POPULATION OF SATELLITES AROUND A MILKY WAY–MASS GALAXY (2016, background): “Finally, Figure 5 shows the cumulative star-formation histories of Latte’s satellites, Mstar(z), computed from their stellar populations at z = 0, along with observed MW satellites from Weisz et al. (2014).”