The episodic Star Formation History of the Carina Dwarf Spheroidal Galaxy

Abstract

We present deep photometry of the Carina dwarf Spheroidal galaxy in the B,V filters from CTIO/MOSAIC, out to and beyond the tidal radius. The accurately calibrated photometry is combined with spectroscopic metallicity distributions of Red Giant Branch stars to determine the detailed star formation and chemical evolution history. The star formation history confirms the episodic formation history of Carina and quantifies the duration and strength of each episode in great detail, as a function radius from the centre. Two main episodes of star formation occurred at old (>8 Gyr) and intermediate (2-8 Gyr) ages, both enriching stars starting from low metallicities ([Fe/H]<-2 dex). By dividing the SFH into two components, we determine that 60pm9 percent of the total number of stars formed within the intermediate age episode. Furthermore, within the tidal radius (0.48 degrees or 888 pc) a total mass in stars of 1.07pm0.08 x10^6 M_sun was formed, giving Carina a stellar mass-to-light ratio of 1.8pm0.8. Combining the detailed star formation history with spectroscopic observations of RGB stars, we are able to determine the detailed age-metallicity relation of each episode and the timescale of alpha-element evolution of Carina from individual stars. The oldest episode displays a tight age-metallicity relation over 6 Gyr with steadily declining alpha-element abundances and a possible alpha-element knee at [Fe/H]~ -2.5 dex. The intermediate age sequence displays a more complex age-metallicity relation starting from low metallicity and a sequence in alpha-element abundances with a slope much steeper than observed in the old episode, starting from [Fe/H]=-1.8 dex and [Mg/Fe]~0.4 dex and declining to Mg-poor values ([Mg/Fe]<-0.5 dex). This indicates clearly that both episodes of star formation formed from gas with different abundance patterns, inconsistent with simple evolution in an isolated system.

arXiv commentaccepted for publication in A&A. 14 pages, 17 figures

References in corpus (44)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Dwarf Galaxies of the Local Group
• The observed properties of dwarf galaxies in and around the Local Group
• The Dartmouth Stellar Evolution Database
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• A Universal Mass Profile for Dwarf Spheroidal Galaxies?
• A Method for Measuring (Slopes of) the Mass Profiles of Dwarf Spheroidal Galaxies
• Numerical Methods of Star Formation History Measurement and Applications to Seven Dwarf Spheroidals
• VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies: I. Nucleosynthesis and Abundance Ratios
• Two distinct ancient components in the Sculptor Dwarf Spheroidal Galaxy: First Results from DART
• The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy
• Population Gradients in Local Group Dwarf Spheroidals
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• A new view of the dwarf spheroidal satellites of the Milky Way from VLT/FLAMES: Where are the very metal poor stars?
• Exploring Halo Substructure with Giant Stars XI: The Tidal Tails of the Carina Dwarf Spheroidal and the Discovery of Magellanic Cloud Stars in the Carina Foreground
• Complexity on Small Scales: The Metallicity Distribution of the Carina Dwarf Spheroidal Galaxy
• The Star Formation & Chemical Evolution History of the Fornax Dwarf Spheroidal Galaxy
• The Star Formation & Chemical Evolution History of the Sculptor Dwarf Spheroidal Galaxy
• Nucleosynthesis and the Inhomogeneous Chemical Evolution of the Carina Dwarf Galaxy
• Complexity on Small Scales III: Iron and alpha Element Abundances in the Carina Dwarf Spheroidal Galaxy
• The Star Formation History of the Carina Dwarf Galaxy
• Study of the Sextans dwarf spheroidal galaxy from the DART CaII triplet survey
• UBVRI Photometric Standard Stars Around the Sky at -50 Degrees Declination
• Non-parametric star formation histories for 5 dwarf spheroidal galaxies of the local group
• The Stellar Populations of the Carina Dwarf Spheroidal Galaxy: I. a New Color-Magnitude Diagram for the Giant and Horizontal Branches
• The ACS LCID project. V. The Star Formation History of the Dwarf Galaxy \objectname[]{LGS-3}: Clues for Cosmic Reionization and Feedback
• Exploring Halo Substructure with Giant Stars: II. Mapping the Extended Structure of the Carina Dwarf Spheroidal Galaxy
• The Carina Project: II. Stellar Populations
• VLT/FLAMES spectroscopy of Red Giant Branch stars in the Carina dwarf spheroidal galaxy
• WFPC2 Observations of the Carina Dwarf Spheroidal Galaxy
• The Araucaria Project. Infrared TRGB distances to the Carina and Fornax dwarf spheroidal galaxies
• Deep Wide-Field Imaging down to the oldest Main Sequence Turnoffs in the Sculptor dwarf spheroidal galaxy
• The Star Formation History of the Pegasus Dwarf Irregular Galaxy
• Orbital evolution of the Carina dwarf galaxy and self-consistent star formation history determination
• The Carina Project: I. Bright Variable Stars
• Dwarf Cepheids in the Carina Dwarf Spheroidal Galaxy
• The extensive age gradient of the Carina dwarf galaxy
• Sailing under the Magellanic Clouds: A DECam View of the Carina Dwarf
• On the stellar content of the Carina dwarf spheroidal galaxy
• Clues on the evolution of the Carina dwarf spheroidal galaxy from the color distribution of its red giant stars
• A Comprehensive, Wide-Field Study of Pulsating Stars in the Carina Dwarf Spheroidal Galaxy
• Star formation history of resolved galaxies. I. The Method
• Chemical Evolution of the Carina Dwarf Spheroidal

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