THE ACS NEARBY GALAXY SURVEY TREASURY. VIII. THE GLOBAL STAR FORMATION HISTORIES OF 60 DWARF GALAXIES IN THE LOCAL VOLUME

By D. Weisz, J. J. Dalcanton, B. Williams, K. Gilbert, E. Skillman, Anil Seth, A. Dolphin, K. McQuinn, Stephanie M. Gogarten, J. Holtzman and 4 more. 2011

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We present uniformly measured star formation histories (SFHs) of 60 nearby (D ≲ 4 Mpc) dwarf galaxies based on color–magnitude diagrams of resolved stellar populations from images taken with the Hubble Space Telescope and analyzed as part of the ACS Nearby Galaxy Survey Treasury program (ANGST). This volume-limited sample contains 12 dwarf spheroidal (dSph)/dwarf elliptical (dE), 5 dwarf spiral, 28 dwarf irregular (dI), 12 dSph/dI (transition), and 3 tidal dwarf galaxies. The sample spans a range of ∼10 mag in MB and covers a wide range of environments, from highly interacting to truly isolated. From the best-fit SFHs, we find three significant results for dwarf galaxies in the ANGST volume: (1) the majority of dwarf galaxies formed the bulk of their mass prior to z ∼ 1, regardless of current morphological type; (2) the mean SFHs of dIs, transition dwarf galaxies (dTrans), and dSphs are similar over most of cosmic time, and only begin to diverge a few Gyr ago, with the clearest differences between the three appearing during the most recent 1 Gyr; and (3) the SFHs are complex and the mean values are inconsistent with simple SFH models, e.g., single bursts, constant star formation rates (SFRs), or smooth, exponentially declining SFRs. The mean SFHs show clear divergence from the cosmic SFH at z ≲ 0.7, which could be evidence that low-mass systems have experienced delayed star formation relative to more massive galaxies. The sample shows a strong density–morphology relationship, such that the dSphs in the sample are less isolated than the dIs. We find that the transition from a gas-rich to gas-poor galaxy cannot be solely due to internal mechanisms such as stellar feedback, and instead is likely the result of external mechanisms, e.g., ram pressure and tidal stripping and tidal forces. In terms of their environments, SFHs, and gas fractions, the majority of the dTrans appear to be low-mass dIs that simply lack Hα emission, similar to Local Group (LG) dTrans DDO 210. However, a handful of dTrans have remarkably low gas fractions, suggesting that they have nearly exhausted their gas supply, analogous to LG dTrans such as Phoenix. Finally, we have also included extensive exploration of uncertainties in the SFH recovery method, including the optimization of time resolution, the effects of photometric depth, and impact of systematic uncertainties due to the limitations in current stellar evolution models.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a85c61222e646518ec6fdf9ac46f0f650c034106

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Citations in the corpus

UPDATED NEARBY GALAXY CATALOG (2013, result): “As shown by Dalcanton et al. (2009), Weisz et al. (2011) and other authors, the deep color–magnitude diagrams obtained at the Hubble Space Telescope for stellar population of nearby galaxies provides an opportunity to reconstruct the history of star formation in them with a resolution of ∼ (0.1 −…”
DIRECT OXYGEN ABUNDANCES FOR LOW-LUMINOSITY LVL GALAXIES (2012, background): “…and GR 8 have detailed star formation histories derived from Hubble Space Telescope observations of their resolved stars which clearly show that the bulk of their star formation occurred well before the last 40 Myr (Tolstoy et al. 1998; Cole et al. 2007; Dohm-Palmer et al. 1998; Weisz et al. 2011).”
(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,…”
LOW CO LUMINOSITIES IN DWARF GALAXIES (2012, background): “Observations of strongly variable star formation histories and starbursts readily indicate that it does not hold in all environments (e.g. Lee et al. 2009; Weisz et al. 2011).”
A BUDGET AND ACCOUNTING OF METALS AT z ∼ 0: RESULTS FROM THE COS-HALOS SURVEY (2013, background): “Moreover, dwarf galaxies have had more stochastic star formation histories (Weisz et al. 2011) and appear to have larger spread in gas-phase metallicities (Zahid et al. 2012a) than ∼ L∗ galaxies.”
GALEX–SDSS–WISE LEGACY CATALOG (GSWLC): STAR FORMATION RATES, STELLAR MASSES, AND DUST ATTENUATIONS OF 700,000 LOW-REDSHIFT GALAXIES (2016, background): “While both parametrizations perform reasonably well, the two-component exponential SF histories yield better fits (geometric mean of reduced χ2 0.7 vs. 1.0), presumably because, by not being smooth, they are able to better match the bursty SF history of low-mass galaxies Weisz et al. (2011).”
THE UNIVERSAL STELLAR MASS–STELLAR METALLICITY RELATION FOR DWARF GALAXIES (2013, background): “Alternatively, at least some dTs may simply be dIrrs that are experiencing a temporary lull in SFR (Skillman et al. 2003), but the morphology–density relation indicates that proximity to a host plays some role in making the transition from dSph to dIrr (Weisz et al. 2011).”
CONVERTING FROM 3.6 AND 4.5 μm FLUXES TO STELLAR MASS (2012, background): “The uncertainties in the recovered star formation rates from CMD synthesis are difficult to ascertain (Harris & Zaritsky 2001; Dolphin 2002; Weisz et al. 2011).”
THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I. HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS (2014, methodology): “The uncertainties were propagated following the method described in the appendix of Weisz et al. (2011a).”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “However, Weisz et al. (2011) have recently shown that dSphs with MB < −10 have extended SFHs, suggesting that the majority of observed gas-free satellites at z = 0 had gas until recently.”
WHY BARYONS MATTER: THE KINEMATICS OF DWARF SPHEROIDAL SATELLITES (2012, background): “Observationally, there is a hint that dSphs do have a faster rise in SF at early times compared to dIrr in the ANGST data (Weisz et al. 2011).”
BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES (2015, background): “…University, Evanston, IL, USA 6 Moore Prize Fellow 7 Carnegie Fellow in Theoretical Astrophysics Stinson et al. 2007; McQuinn et al. 2010; Weisz et al. 2011; González-Samaniego et al. 2014), which in turn can have significant effects on these galaxies’ dynamical and morphological…”
A STELLAR MASS THRESHOLD FOR QUENCHING OF FIELD GALAXIES (2012, background): “…of galaxies below this stellar mass. Studies of dwarf galaxies within 10Mpc with stellar masses below 107 M⊙ are consistent with our results: low mass quenched galaxies exist only within a few virial radius of the Milky Way, M31 or the nearby M81 group (Grcevich & Putman 2009; Weisz et al. 2011).”
A BARYONIC SOLUTION TO THE MISSING SATELLITES PROBLEM (2012, result): “…= 0 reach vpeak at relatively low z (see Figure 2), and may have extended star formation to quite low z. Z12 also found that satellites with MV < −8 had extended star formation histories, consistent with observational estimates (Grebel & Gallagher 2004; Dellenbusch et al. 2008; Weisz et al. 2011).”
Modeling the Panchromatic Spectral Energy Distributions of Galaxies (2013, methodology): “Leitner (2012) compared the SFHs derived by Weisz et al. (2011) to the SFHs derived from integrated light spectra by Tojeiro et al. (2009).”
MadDM v.3.0: A comprehensive tool for dark matter studies (2018, background): “These Milky Way satellite galaxies are known to be dark matter dominated objects, with a reduced baryonic content in terms of recent stellar formation activity and interstellar gas medium [66–69].”
Making Galaxies in a Cosmological Context: The Need for Early Stellar Feedback (2012, background): “Looking at nearby dwarf galaxies, Weisz et al. (2011) finds that star formation histories are also mostly flat with variations limited to factors of a few, which again compares well with the simulation.”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, background): “We expect that Im→ Sph conversion is still easier, as implied by evidence in the Local Group below.”