THE QUENCHING OF THE ULTRA-FAINT DWARF GALAXIES IN THE REIONIZATION ERA

By T. Brown, Jason Tumlinson, M. Geha, J. Simon, L. Vargas, D. VandenBerg, E. Kirby, J. Kalirai, R. Avila, M. Gennaro and 4 more. 2014

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We present new constraints on the star formation histories of six ultra-faint dwarf galaxies: Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I. Our analysis employs a combination of high-precision photometry obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, medium-resolution spectroscopy obtained with the DEep Imaging Multi-Object Spectrograph on the W. M. Keck Observatory, and updated Victoria-Regina isochrones tailored to the abundance patterns appropriate for these galaxies. The data for five of these Milky Way satellites are best fit by a star formation history where at least 75% of the stars formed by z ∼ 10 (13.3 Gyr ago). All of the galaxies are consistent with 80% of the stars forming by z ∼ 6 (12.8 Gyr ago) and 100% of the stars forming by z ∼ 3 (11.6 Gyr ago). The similarly ancient populations of these galaxies support the hypothesis that star formation in the smallest dark-matter sub-halos was suppressed by a global outside influence, such as the reionization of the universe.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/f9d74612c262b5870b5f94b9dd42b525c5faf26e

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Citations in the corpus

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…”
Cosmic Dawn (CoDa): the first radiation-hydrodynamics simulation of reionization and galaxy formation in the Local Universe (2015, background): “While this is currently a matter of debate, it seems that at least the low-mass satellites of the MW and M31 may have star formation histories compatible with a very early suppression (Brown et al. 2014; Weisz et al. 2015), e.g. by reionization.”
Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites (2015, background): “Remarkably, this appears to be the case with the known ultra faint dwarfs of the Milky Way (Brown et al. 2014).”
Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1 (2019, background): “…reionization and stellar feedback drastically suppress dwarf galaxy formation in low-mass halos (e.g., Bullock et al. 2000; Somerville 2002; Brown et al. 2014), and tidal interactions with the Galactic disk are expected to disrupt a significant number of systems (e.g., Garrison-Kimmel et…”
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).”
A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters (2018, methodology): “Brown et al. (2014) presented HST/ACS photometry for Leo IV and argued that the system is composed exclusively of old, metal-poor stars: i.e., the system formed more than 80% of its stars by z = 6.”
Farthest Neighbor: The Distant Milky Way Satellite Eridanus II (2016, background): “We note that Eri II is more distant and more massive than any of the Milky Way satellites strongly suspected to be quenched by reionization based on previous deep HST imaging (Brown et al. 2014).”
EIGHT NEW MILKY WAY COMPANIONS DISCOVERED IN FIRST-YEAR DARK ENERGY SURVEY DATA (2015, background): “Like the previously known ultra-faint dwarfs, the new DES systems are old and metal-poor (e.g., Brown et al. 2014).”
Co-formation of the disc and the stellar halo (2018, background): “Most dwarf spheroidals host stars nearly as old as the Universe itself (see Tolstoy et al. 2009), while many ultra-faint dwarfs appear to have formed the bulk of their stellar populations only slightly less than a Hubble time ago (see e.g. Belokurov et al. 2007; Brown et al. 2014).”