Blue straggler stars in dwarf spheroidal galaxies

Abstract

Blue straggler star (BSS) candidates have been observed in all old dwarf spheroidal galaxies (dSphs), however whether or not they are authentic BSSs or young stars has been a point of debate. To both address this issue and obtain a better understanding of the formation of BSSs in different environments we have analysed a sample of BSS candidates in two nearby Galactic dSphs, Draco and Ursa Minor. We have determined their radial and luminosity distributions from wide field multicolour imaging data extending beyond the tidal radii of both galaxies. BSS candidates are uniformly distributed through the host galaxy, whereas a young population is expected to show a more clumpy distribution. Furthermore, the observed radial distribution of BSSs, normalized to both red giant branch (RGB) and horizontal branch (HB) stars, is almost flat, with a slight decrease towards the centre. Such a distribution is at odds with the predictions for a young stellar population, which should be more concentrated. Instead, it is consistent with model predictions for BSS formation by mass transfer in binaries (MT-BSSs). Such results, although not decisive, suggest that these candidates are indeed BSSs and that MT-BSSs form in the same way in Draco and Ursa Minor as in globular clusters. This favours the conclusion that Draco and Ursa Minor are truly 'fossil' galaxies, where star formation ceased completely more than 8 billion years ago.

16 pages, 10 figures, MNRAS, in press

References in corpus (44)

• Galactic Stellar and Substellar Initial Mass Function
• Dwarf Galaxies of the Local Group
• Theoretical isochrones in several photometric systems I. Johnson-Cousins-Glass, HST/WFPC2, HST/NICMOS, Washington, and ESO Imaging Survey filter sets
• 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
• A Complete N-body Model of the Old Open Cluster M67
• A Dynamical Fossil in the Ursa Minor Dwarf Spheroidal Galaxy
• Direct N-body Modelling of Stellar Populations: Blue Stragglers in M67
• Kinematically Cold Populations at Large Radii in the Draco and Ursa Minor Dwarf Spheroidals
• Stellar Collisions and the Interior Structure of Blue Stragglers
• Blue straggler production in globular clusters
• Early Gas Stripping as the Origin of the Darkest Galaxies in the Universe
• Non-parametric star formation histories for 5 dwarf spheroidal galaxies of the local group
• Dynamics and Interactions of Binaries and Neutron Stars in Globular Clusters
• The Draco and Ursa Minor dwarf spheroidals. A comparative study
• The Star Formation History and the spatial distribution of stellar populations in the Ursa Minor Dwarf Spheroidal Galaxy
• Blue Straggler Stars: a direct comparison of Star counts and population ratios in six Galactic Globular Clusters
• The Star Formation History and the Morphological Evolution of the Draco Dwarf Spheroidal Galaxy
• Evolution of Stellar Collision Products in Globular Clusters - II. Off-axis Collision
• The contribution of primordial binaries to the blue straggler population in 47 Tucanae
• The radial distribution of blue straggler stars and the nature of their progenitors
• The pure non-collisional Blue Straggler population in the giant stellar system omega Centauri
• Discovery of another peculiar radial distribution of Blue Stragglers in Globular Clusters: The case of 47 Tuc
• A New Culprit in the Second Parameter Problem in the Sculptor Dwarf Spheroidal Galaxy?
• The blue plume population in dwarf spheroidal galaxies: genuine blue stragglers or young stellar population?
• A photometrically and kinematically distinct core in the Sextans dwarf spheroidal galaxy
• A comprehensive set of simulations of high-velocity collisions between main sequence stars
• The RR Lyrae Distance to the Draco Dwarf Spheroidal Galaxy
• A Panchromatic Study of the Globular Cluster NGC 1904. I: The Blue Straggler Population
• On Kinematic Substructure in the Sextans Dwarf Spheroidal Galaxy
• Metal-poor Field Blue Stragglers: More Evidence for Mass Transfer
• The Blue Straggler Population of the Globular Cluster M5
• The blue stragglers formed via mass transfer in old open clusters
• The INT Wide Field Imaging Survey(WFS)
• The small Blue Straggler star population in the dense Galactic Globular Cluster NGC 6752
• Draco, a flawless dwarf galaxy
• The Distribution of Collisionally Induced Blue Stragglers in the Colour-Magnitude Diagram
• Modeling the Radial Distribution of Blue Stragglers in M3
• Formation of Omega Centauri by Tidal Stripping of a Dwarf Galaxy
• The Formation Rate of Blue Stragglers in 47 Tucanae
• Stars of the Draco Dwarf Spheroidal Galaxy Beyond its Measured Tidal Boundary
• The Blue Straggler Population of the Globular Cluster M5: Comparison with M3
• A Catalog of Candidate Field Horizontal-Branch and A-Type Stars. III. A 2MASS-Cleaned Version
• Tracing the Dynamical History of the Globular Cluster 47 Tucanae

Cited by in corpus (40)

• Star Formation Histories, Abundances and Kinematics of Dwarf Galaxies in the Local Group
• The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations
• The ACS LCID project. III. The star formation history of the Cetus dSph galaxy: a post-reionization fossil
• The First Detection of Blue Straggler Stars in the Milky Way Bulge
• Formation and Evolution of Dwarf Elliptical Galaxies - II. Spatially resolved star-formation histories
• The Star Formation Histories of Local Group Dwarf Galaxies III. Characterizing Quenching in Low-Mass Galaxies
• Stellar population models in the UV: I. Characterisation of the New Generation Stellar Library
• The ISLAndS project II: The Lifetime Star Formation Histories of Six Andromeda dSphs
• Implications for the Formation of Blue Straggler Stars from HST Ultraviolet Observations of NGC 188
• The Stellar Populations and Structural Properties of Ultra Faint Dwarf Galaxies, Canes Venatici I, Bootes I, Canes Venatici II, and Leo IV
• Star Formation History and Chemical Evolution of the Sextans Dwarf Spheroidal Galaxy
• Stellar Collisions and Blue Straggler Stars in Dense Globular Clusters
• Blue Straggler masses from pulsation properties. I. The case of NGC6541
• A deep view into the nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. I. Data and stellar population characterization
• Deep Wide-Field Imaging down to the oldest Main Sequence Turnoffs in the Sculptor dwarf spheroidal galaxy
• Blue straggler stars in dwarf spheroidal galaxies II: Sculptor and Fornax
• Spatial dependence of the Star Formation History in the Central Regions of the Fornax Dwarf Spheroidal Galaxy
• A Deeper Look at Leo IV: Star Formation History and Extended Structure
• The ACS LCID project VII: the blue stragglers population in the isolated dSph galaxies Cetus and Tucana
• The evolved stars of Leo II dSph galaxy from near-infrared UKIRT/WFCAM observations
• Local Group dSph radio survey with ATCA (II): Non-thermal diffuse emission
• Tracing the stellar component of low surface brightness Milky Way Dwarf Galaxies to their outskirts I: Sextans
• Pegasus W: An Ultra-Faint Dwarf Galaxy Outside the Halo of M31 Not Quenched by Reionization
• The ISLANDS project I: Andromeda XVI, An Extremely Low Mass Galaxy not Quenched by Reionization
• A Megacam Survey of Outer Halo Satellites. II. Blue Stragglers in the Lowest Stellar Density Systems
• Evidence for Blue Straggler Stars Rejuvenating the Integrated Spectra of Globular Clusters
• The HST/ACS star formation history of the Tucana dwarf spheroidal galaxy: clues from the horizontal branch
• UOCS.VI. UVIT/AstroSat detection of low-mass white dwarf companions to 4 more blue stragglers in M67
• Mock Observations of Blue Stragglers in Globular Cluster Models
• MOCCA code for star cluster simulations - VI. Bimodal spatial distribution of blue stragglers
• MOCCA code for star cluster simulations - V. Initial globular cluster conditions influence on blue stragglers
• Variable Stars in Local Group Galaxies. IV. RR Lyrae stars in the central regions of the low-density galaxy Crater II
• Simple Stellar Population Models as probed by the Large Magellanic Cloud Star Cluster ESO 121-SC03
• The central Blue Straggler population in four outer-halo globular clusters
• The Rich Lack Close Neighbours: The Dependence of Blue-Straggler Fraction on Metallicity
• The survival of dynamical fossils in dwarf spheroidal galaxies in conventional and modified dynamics
• Blue Straggler Bimodality: a Brownian Motion Model
• Blue straggler stars beyond the Milky Way. II. A binary origin for blue straggler stars in Magellanic Cloud clusters
• The Blue Straggler Population in Dwarf Galaxies
• Unveiling Bifurcated Blue Straggler Sequences in NGC 2173: Insights from Binary Evolution