Blue Horizontal Branch Stars in the Sagittarius dwarf spheroidal galaxy

Abstract

We report on the recovery of a Blue Horizontal Branch (BHB) population belonging to the Sagittarius Dwarf Spheroidal Galaxy (Sgr). The sequence is clearly identified in the (V, V-I) Color Magnitude Diagram (CMD) obtained for about 500,000 stars in the region of the globular cluster M~54. The BHB morphology is similar to the analogous sequence in M~54, but it is unambiguously associated with Sgr since {\it(i)} it is detected well outside the main body of the cluster, up to more than 5 tidal radii from the cluster center and {\it(ii)} the BHB stars follow the radial distribution of the other stellar populations of Sgr. This finding finally demonstrates that the Sgr galaxy hosts a significant (of the order of $\sim$10%) old and metal-poor stellar population ([Fe/H]\ltsima -1.3; age \gtsima 10 Gyr), similar to that of its oldest clusters (M~54, Ter~8). We also show that the Sgr BHB sequence found here is the counterpart of the analogous feature observed by Newberg et al. (2002) in the Sgr Stream, in a field more than 80$\degr$ away from the center of the galaxy.

arXiv comment12 pages, 4 figures. Accepted for publication in ApJ Letters

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Cited by in corpus (35)

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• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: Variation of the Metallicity Distribution Function Along the Sagittarius Stream
• The Ital-FLAMES survey of the Sagittarius dwarf Spheroidal galaxy. I. Chemical abundances of bright RGB stars
• Tracing out the Northern Tidal Stream of the Sagittarius Dwarf Spheoridal Galaxy
• A Sequoia in the Garden: FSR 1758 - Dwarf Galaxy or Giant Globular Cluster?
• Origins of ultra-diffuse galaxies in the Coma cluster II. Constraints from their stellar populations
• High-resolution spectroscopy of RGB stars in the Sagittarius Streams. I. Radial velocities and chemical abundances
• Chemical abundances in the nucleus of the Sagittarius dwarf spheroidal galaxy
• The central density cusp of the Sagittarius dwarf spheroidal galaxy
• The distance to the Leo I dwarf spheroidal galaxy from the Red Giant Branch Tip
• The age of the main population of the Sagittarius dwarf spheroidal galaxy. Solving the "M giant conundrum"
• Detection of a population gradient in the Sagittarius Stream
• The core of the Canis Major galaxy as traced by Red Clump stars
• The Progenitors of the Milky Way Stellar Halo: Big Bricks Favoured over Little Bricks
• Kinematics and Chemistry of Stars Along the Sagittarius Trailing Tidal Tail and Constraints on the Milky Way Mass Distribution
• The Structure of the Sagittarius Stellar Stream as Traced by Blue Horizontal Branch Stars
• Kinematic Structure in the Galactic Halo at the North Galactic Pole: RR Lyrae and BHB Stars show different kinematics
• The Northern wraps of the Sagittarius Stream as traced by Red Clump stars: distances, intrinsic widths and stellar densities
• Discovery of Blue Hook Stars in the Massive Globular Cluster M54
• Surveying the Inner Halo of the Galaxy with 2MASS-Selected Horizontal Branch Candidates
• Still at Odds with Conventional Galaxy Evolution: The Star Formation History of Ultra-Diffuse Galaxy Dragonfly 44
• The IGIMF and other IMFs in dSphs: the case of Sagittarius
• A homogeneous comparison between the chemical composition of the Large Magellanic Cloud and the Sagittarius dwarf galaxy
• The population of variable stars in M54 (NGC6715)
• Clean catalogues of blue horizontal-branch stars using Gaia EDR3
• The metallicity distribution in the core of the Sagittarus dwarf spheroidal: minimising the metallicity biases
• The STREGA survey. II. Globular Cluster Palomar 12
• Photometric Metallicity Calibration with SDSS and SCUSS and its Application to distant stars in the South Galactic Cap
• AGC 226178 and NGVS 3543: Two deceptive dwarfs towards Virgo
• The Pristine Inner Galaxy Survey (PIGS) IV: A photometric metallicity analysis of the Sagittarius dwarf spheroidal galaxy
• Probing the Sagittarius stream with blue horizontal branch stars
• The Blue Straggler Population in Dwarf Galaxies
• Young stars raining through the Galactic Halo: the nature and orbit of Price-Whelan 1