Star Formation Histories of Ultra-Faint Dwarf Galaxies: environmental differences between Magellanic and non-Magellanic satellites?

Abstract

We present the color-magnitude diagrams and star formation histories (SFHs) of seven ultra-faint dwarf galaxies: Horologium 1, Hydra 2, Phoenix 2, Reticulum 2, Sagittarius 2, Triangulum 2, and Tucana 2, derived from high-precision Hubble Space Telescope photometry. We find that the SFH of each galaxy is consistent with them having created at least 80% of the stellar mass by $z\sim 6$. For all galaxies, we find quenching times older than 11.5 Gyr ago, compatible with the scenario in which reionization suppresses the star formation of small dark matter halos. However, our analysis also reveals some differences in the SFHs of candidate Magellanic Cloud satellites, i.e., galaxies that are likely satellites of the Large Magellanic Cloud and that entered the Milky Way potential only recently. Indeed, Magellanic satellites show quenching times about 600 Myr more recent with respect to those of other Milky Way satellites, on average, even though the respective timings are still compatible within the errors. This finding is consistent with theoretical models that suggest that satellites' SFHs may depend on their host environment at early times, although we caution that within the error bars all galaxies in our sample are consistent with being quenched at a single epoch.

arXiv comment7 pages, 3 figures, 2 tables. Accepted for publication in ApJL

References in corpus (46)

• On the variation of the Initial Mass Function
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• Reconciling dwarf galaxies with LCDM cosmology: Simulating a realistic population of satellites around a Milky Way-mass galaxy
• Eight New Milky Way Companions Discovered in First-Year Dark Energy Survey Data
• The Faintest Dwarf Galaxies
• Beasts of the Southern Wild: Discovery of nine Ultra Faint satellites in the vicinity of the Magellanic Clouds
• Eight Ultra-faint Galaxy Candidates Discovered in Year Two of the Dark Energy Survey
• The Quenching of the Ultra-Faint Dwarf Galaxies in the Reionization Era
• Universal structure of dark matter haloes over a mass range of 20 orders of magnitude
• Gaia DR2 Proper Motions of Dwarf Galaxies within 420 kpc: Orbits, Milky Way Mass, Tidal Influences, Planar Alignments, and Group Infall
• Sagittarius II, Draco II and Laevens 3: three new Milky Way satellites discovered in the Pan-STARRS 1 3pi Survey
• The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater
• Pre-reionization Fossils, Ultra-faint Dwarfs and the Missing Galactic Satellite Problem
• Be it therefore resolved: Cosmological Simulations of Dwarf Galaxies with Extreme Resolution
• Small Dwarf Galaxies Within Larger Dwarfs: Why Some Are Luminous While Most Go Dark
• The Star Formation Histories of Local Group Dwarf Galaxies II. Searching For Signatures of Reionization
• The Orbital Histories of Magellanic Satellites Using Gaia DR2 Proper Motions
• Hydra II: a faint and compact Milky Way dwarf galaxy found in the Survey of the Magellanic Stellar History
• Ultra-faint dwarfs in a Milky Way context: Introducing the Mint Condition DC Justice League Simulations
• SMASH - Survey of the MAgellanic Stellar History
• The Missing Satellites of the Magellanic Clouds? Gaia Proper Motions of the Recently Discovered Ultra-Faint Galaxies
• Connecting the first galaxies with ultra faint dwarfs in the Local Group: chemical signatures of Population~III stars
• Discovery of two neighboring satellites in the Carina constellation with MagLiteS
• Snake in the Clouds: A new nearby dwarf galaxy in the Magellanic bridge
• Limit on the LMC mass from a census of its satellites
• Satellites of LMC-Mass Dwarfs: Close Friendships Ruined by Milky Way Mass Halos
• The Star Formation Histories of Local Group Dwarf Galaxies III. Characterizing Quenching in Low-Mass Galaxies
• Identifying true satellites of the Magellanic Clouds
• Isochrones for Old (> 5 Gyr) Stars and Stellar Populations. I. Models for $-2.4\le$ [Fe/H] $\le +0.6$, $0.25\le Y\le 0.33$, and $-0.4\le$ [$\alpha$\Fe] $\le +0.4$
• A Deeper Look at the New Milky Way Satellites: Sagittarius II, Reticulum II, Phoenix II, and Tucana III
• The predicted luminous satellite populations around SMC and LMC-mass galaxies - A missing satellite problem around the LMC?
• Hubble Tarantula Treasury Project: Unraveling Tarantula's Web. II. Optical and Near Infrared Star Formation History of the Starburst Cluster NGC 2070 in 30 Doradus
• Clues to the "Magellanic Galaxy" from Cosmological Simulations
• The imprint of cosmic reionisation on the luminosity function of galaxies
• The Frequency of Dwarf Galaxy Multiples at Low Redshift in SDSS vs. Cosmological Expectations
• The cumulative star-formation histories of dwarf galaxies with TNG50. I: Environment-driven diversity and connection to quenching
• Dark and luminous satellites of LMC-mass galaxies in the FIRE simulations
• The binary fraction of stars in dwarf galaxies: the case of Leo II
• A Gaia DR 2 and VLT/FLAMES search for new satellites of the LMC
• Comparing the Quenching Times of Faint M31 and Milky Way Satellite Galaxies
• The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies
• The Pristine Dwarf-Galaxy survey - II. In-depth observational study of the faint Milky Way satellite Sagittarius II
• The Pristine Dwarf-Galaxy survey -- III. Revealing the nature of the Milky Way globular cluster Sagittarius II
• Where are All the Gas-Bearing Local Dwarf Galaxies? Quantifying Possible Impacts of Reionization
• A Megacam Survey of Outer Halo Satellites. II. Blue Stragglers in the Lowest Stellar Density Systems

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• Symphony: Cosmological Zoom-in Simulation Suites over Four Decades of Host Halo Mass
• Tucana B: A Potentially Isolated and Quenched Ultra-faint Dwarf Galaxy at D$\approx$1.4 Mpc
• Metallicity Distribution Functions of 13 Ultra-Faint Dwarf Galaxy Candidates from Hubble Space Telescope Narrowband Imaging
• Timing the r-Process Enrichment of the Ultra-Faint Dwarf Galaxy Reticulum II
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• Inhomogeneous Galactic Chemical Evolution: Modelling Ultra-Faint Dwarf Galaxies of the Large Magellanic Cloud
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• The Low-Mass Stellar Initial Mass Function in Nearby Ultrafaint Dwarf Galaxies
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• Measuring Resolved Star Formation Histories from High-Precision Color-Magnitude Diagrams with StarFormationHistories.jl
• Understanding Stellar Mass-Metallicity and Size Relations in Simulated Ultra-Faint Dwarf Galaxies
• The THESAN project: environmental drivers of Local Group reionization
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• How Many Bursts Does it Take to Form a Core at the Center of a Galaxy?
• A detailed star formation history of the distant Milky Way satellite Canes Venatici I: An old dwarf spheroidal forming most of its stars after reionisation
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