Metallicities, Age--Metallicity relationships, and Kinematics of Red Giant Branch Stars in the Outer Disk of the Large Magellanic Cloud

Abstract

The outer disk of the LMC is studied in order to unveil clues about its formation and evolution. Complementing our previous studies in innermost fields (3<R<7 kpc), we obtained deep color magnitude diagrams in 6 fields with radius from 5.2 to 9.2 kpc. The comparison with isochrones shows that while the oldest population is approximately coeval in all fields, the age of the youngest populations increases with increasing radius. Low-resolution spectroscopy in the infrared CaII triplet region has been obtained for about 150 stars near the tip red giant branch in the same fields. Radial velocities and stellar metallicities have been obtained from these spectra. The metallicity distribution of each field has been analyzed together with those previously studied. The metal content of the most metal-poor objects, which are also the oldest according to the derived age-metallicity relationships, is similar in all fields independently of the radius. However, while the metallicity of the most metal-rich objects measured, which are the youngest ones, remains constant in the inner 6 kpc, it decreases with increasing radius from there off. The same is true for the mean metallicity. According to the derived age-metallicity relationships, which are consistent with being the same in all fields, this result may be interpreted as an outside-in formation scheme in opposition with the inside-out scenario predicted by LCDM cosmology for a galaxy like the LMC. The analysis of the radial velocities of our sample of giants shows that they follow a rotational cold disk kinematics. The velocity dispersion increases as metallicity decreases indicating that the most metal-poor/oldest objects are distributed in a thicker disk than the most metal-rich/youngest ones in agreement with the findings in other disks such as that of the Milky Way. They do not seem to be part of a hot halo, if one exists in the LMC.

50 pages, 12 figures, accepted for publication in AJ

References in corpus (13)

• Are the Magellanic Clouds on their First Passage about the Milky Way?
• The NIR Ca II triplet at low metallicity - Searching for extremely low-metallicity stars in classical dwarf galaxies
• Analysis and calibration of CaII triplet spectroscopy of Red Giant Branch stars from VLT/FLAMES observations
• Calcium II Triplet Spectroscopy of LMC Red Giants. I. Abundances and Velocities for a Sample of Populous Clusters
• The Chemical Enrichment History of the Large Magellanic Cloud
• The Chemical Enrichment History of the Small Magellanic Cloud and Its Gradients
• The ACS LCID project. V. The Star Formation History of the Dwarf Galaxy \objectname[]{LGS-3}: Clues for Cosmic Reionization and Feedback
• The chemical abundance of the very metal rich old Open Clusters NGC 6253 and NGC 6791
• The Infrared Ca II triplet as metallicity indicator
• The Stellar Populations of M33's Outer Regions IV: Inflow History and Chemical Evolution
• The Stellar Populations of M33's Outer Regions III: Star Formation History
• Outside-in disk evolution in the LMC
• Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud. II. The extended sample

Cited by in corpus (45)

• The Dark Energy Survey: more than dark energy - an overview
• Third-Epoch Magellanic Cloud Proper Motions II: The Large Magellanic Cloud Rotation Field in Three Dimensions
• The Close Binary Fraction of Solar-type Stars is Strongly Anti-correlated with Metallicity
• The Near Infrared Ca II Triplet as Metallicity Indicator: II Extension to extremely metal-poor metallicity regimes
• The VMC Survey IV. The LMC star formation history and disk geometry from four VMC tiles
• SMASHing the LMC: A Tidally-induced Warp in the Outer LMC and a Large-scale Reddening Map
• The age-metallicity relationship of the Large Magellanic Cloud field star population from wide-field Washington photometry
• A 10 kpc stellar substructure at the edge of the Large Magellanic Cloud: perturbed outer disk or evidence for tidal stripping?
• 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
• The ACS LCID project. IX. Imprints of the early Universe in the radial variation of the star formation history of dwarf galaxies
• Spatially resolved LMC star formation history: I. Outside in evolution of the outer LMC disk
• The panchromatic view of the Magellanic Clouds from Classical Cepheids. I. Distance, Reddening and Geometry of the Large Magellanic Cloud disk
• The VMC survey -- XLIII. The spatially resolved star formation history across the Large Magellanic Cloud
• The OCCASO survey: Presentation and radial velocities of twelve Milky Way Open Clusters
• Anomalous Cepheids in the Large Magellanic Cloud: Insight into their origin and connection with the star formation history
• The MAGellanic Inter-Cloud project (MAGIC) I: Evidence for intermediate-age stellar populations in between the Magellanic Clouds
• The Magellanic Inter-Cloud Project (MAGIC) III: First spectroscopic evidence of a dwarf stripping a dwarf
• Metallicity distribution functions of the old populations of the Magellanic Clouds from RR Lyrae stars
• Formation of S0s via disc accretion around high-redshift compact ellipticals
• SMASH 1: a very faint globular cluster disrupting in the outer reaches of the LMC?
• A Possible Solution for the $M/L-[Fe/H]$ Relation of Globular Clusters in M31. II. the Age-Metallicity Relation
• The Magellanic Edges Survey I. Description and First Results
• Physical properties of star clusters in the outer LMC as observed by the Dark Energy Survey
• Distinguishing between symbiotic stars and planetary nebulae
• Search for an intrinsic metallicity spread in old globular clusters of the Large Magellanic Cloud
• Radial velocities and metallicities from infrared Ca II triplet spectroscopy of open clusters: Berkeley 26, Berkeley 70, NGC 1798, and NGC 2266
• A homogeneous comparison between the chemical composition of the Large Magellanic Cloud and the Sagittarius dwarf galaxy
• The star cluster frequency throughout the Large Magellanic Cloud
• The Magellanic Edges Survey III. Kinematics of the disturbed LMC outskirts
• Chemical and structural analysis of the Large Magellanic Cloud using the fundamental mode RR Lyrae stars
• A search for star clusters in the outskirts of the Large Magellanic Cloud: indication of clusters in the age gap
• Chemical abundances of metal-poor RR Lyrae stars in the Magellanic Clouds
• Ultra-faint dwarf galaxies as a test of early enrichment and metallicity-dependent star formation
• Shape of the outer stellar warp in the Large Magellanic Cloud disk
• The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy
• The open cluster King~1 in the second quadrant
• Dynamical Masses and Mass-to-light Ratios of Resolved Massive Star Clusters. I. NGC 419 and NGC 1846
• Astrophysical properties of newly discovered Magellanic Cloud star clusters
• A likely runaway star cluster in the outer disc of the Large Magellanic Cloud
• An Expanded Chemo-dynamical Sample of Red Giants in the Bar of the Large Magellanic Cloud
• Chemo-Dynamical Tagging in the Outskirts: The Origins of Stellar Substructures in the Magellanic Clouds
• Sizing the star cluster population of the Large Magellanic Cloud
• Revisiting the near infrared Calcium triplet as metallicity indicator
• The Origin of the Large Magellanic Cloud Globular Cluster NGC 2005
• The Magellanic Edges Survey -- II. Formation of the LMC's northern arm