A MegaCam Survey of Outer Halo Satellites. VI: The Spatially Resolved Star Formation History of the Carina Dwarf Spheroidal Galaxy

Abstract

We present the spatially resolved star formation history (SFH) of the Carina dwarf spheroidal galaxy, obtained from deep, wide-field g,r imaging and a metallicity distribution from the literature. Our photometry covers $\sim 2$ deg${}^2$, reaching up to $\sim 10$ times the half-light radius of Carina with a completeness higher than $50\%$ at $g\sim 24.5$, more than one magnitude fainter than the oldest turnoff. This is the first time a combination of depth and coverage of this quality has been used to derive the SFH of Carina, enabling us to trace its different populations with unprecedented accuracy. We find that Carina's SFH consists of two episodes well separated by a star formation temporal gap. These episodes occurred at old ($>10$ Gyr) and intermediate ($2$-$8$ Gyr) ages. Our measurements show that the old episode comprises the majority of the population, accounting for $54\pm 5\%$ of the stellar mass within $1.3$ times the King tidal radius, while the total stellar mass derived for Carina is $1.60\pm 0.09\times 10^6{M}_{\odot }$, and the stellar mass-to-light ratio $1.8\pm 0.2$. The SFH derived is consistent with no recent star formation which hints that the observed blue plume is due to blue stragglers. We conclude that the SFH of Carina evolved independently of the tidal field of the Milky Way, since the frequency and duration of its star formation events do not correlate with its orbital parameters. This result is supported by the age/metallicity relation observed in Carina, and the gradients calculated indicating that outer regions are older and more metal poor.

Accepted in ApJ (22 pages, 13 figures)

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Cited by in corpus (9)

• APOGEE Chemical Abundance Patterns of the Massive Milky Way Satellites
• The Populations of Carina. II. Chemical Enrichment
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• The bursty star formation history of the Fornax dwarf spheroidal galaxy revealed with the HST
• Dissecting the stellar content of Leo I: a dwarf irregular caught in transition
• Homogeneity in the early chemical evolution of the Sextans dwarf Spheroidal galaxy
• The RR Lyrae Delay-Time Distribution: A Novel Perspective on Models of Old Stellar Populations
• Star Formation Histories of Dwarf Spheroidal and Dwarf Elliptical Galaxies in the Local Universe
• The Populations of Carina. I. Decoding the Color--Magnitude Diagram