The SDSS-Gaia View of the Color-Magnitude Relation for Blue Horizontal-branch Stars

Abstract

We present an updated sample of blue horizontal-branch (BHB) stars selected from the photometric and spectroscopic data from Sloan Digital Sky Survey and its associated project Sloan Extension for Galactic Understanding and Exploration (SEGUE). With this data, we selected candidates for A-type stars in the color-color space and then a mixture modeling technique was implemented in order to distinguish between BHB and main-sequence/blue-straggler stars based on their surface gravity values ($\log \mathrm{g}$) estimated by the SEGUE Stellar Parameter Pipeline. Our robust approach allows us to attribute individual probabilities of each star truly being in the BHB stage. Hence, our method is advantageous in comparison to previous SEGUE BHB selections that adopted simple $\log \mathrm{g}$ cuts. We also revisit the color-magnitude relation for these stars and propose two calibrations, based on updated distances for Galactic globular clusters, to estimate absolute magnitudes with $(g-r{)}_0$ and $(u-r{)}_0$ colors.

arXiv commentPublished in The Astrophysical Journal

References in corpus (55)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Sloan Digital Sky Survey: Technical Summary
• The Gaia mission
• The SIMBAD astronomical database
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• API design for machine learning software: experiences from the scikit-learn project
• The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
• The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
• The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• Co-formation of the Galactic disc and the stellar halo
• The Milky Way's Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from Kinematics of ~2400 SDSS Blue Horizontal Branch Stars
• The SEGUE Stellar Parameter Pipeline. I. Description and Initial Validation Tests
• Gaia EDR3 view on Galactic globular clusters
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• Streams, substructures and the early history of the Milky Way
• The SEGUE Stellar Parameter Pipeline. II. Validation with Galactic Globular and Open Clusters
• The Milky Way stellar halo out to 40 kpc : Squashed, broken but smooth
• Precession of the Sagittarius stream
• Ghostly Tributaries to the Milky Way: Charting the Halo's Stellar Streams with the Gaia DR2 catalogue
• One large blob and many streams frosting the nearby stellar halo in Gaia DR2
• Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
• Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. I. Crowded Field Photometry and Cluster Fiducial Sequences in ugriz
• Blue horizontal branch stars in the Sloan Digital Sky Survey: I. Sample selection and structure in the Galactic halo
• The cold veil of the Milky Way stellar halo
• Apocenter Pile-Up: Origin of the Stellar Halo Density Break
• The Milky Way Halo in Action Space
• Detection of the Milky Way reflex motion due to the Large Magellanic Cloud infall
• The Halo's Ancient Metal-Rich Progenitor Revealed with BHB Stars
• Detection of the LMC-induced sloshing of the Galactic halo
• $S^5$: The Orbital and Chemical Properties of One Dozen Stellar Streams
• A Low-Mass Stellar-Debris Stream Associated with a Globular Cluster Pair in the Halo
• Stellar streams around the Magellanic Clouds
• The mass of the Milky Way out to 100 kpc using halo stars
• The slight spin of the old stellar halo
• Distant field BHB stars and the mass of the Galaxy I: Classification of halo A-type stars
• A stellar stream remnant of a globular cluster below the metallicity floor
• Microarcsecond Astrometry: Science Highlights from Gaia
• A-type stars in the Canada-France Imaging Survey I. The stellar halo of the Milky Way traced to large radius by blue horizontal branch stars
• Identifying Blue Horizontal Branch Stars Using the z Filter
• The Milky Way's Shell Structure Reveals the Time of a Radial Collision
• Milky Way Mass with K Giants and BHB Stars Using LAMOST, SDSS/SEGUE, and Gaia: 3D Spherical Jeans Equation and Tracer Mass Estimator
• The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO
• Chronography of the Milky Way's Halo System with Field Blue Horizontal-Branch Stars
• Revealing the Complicated Story of the Cetus Stream with StarGO
• The Frequency of Field Blue-Straggler Stars in the Thick Disk and Halo System of the Galaxy
• The Pristine survey -- VII. A cleaner view of the Galactic outer halo using blue horizontal branch stars
• Identification of Sagittarius stream members in Angular Momentum space with Gaussian mixture techniques
• Contribution of Gaia Sausage to the Galactic Stellar Halo Revealed by K Giants and Blue Horizontal Branch Stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and Gaia
• A new calibration for the Blue Horizontal Branch
• Distances to Galactic OB-stars: Photometry vs. Parallax
• A Semi-Empirical Study of the Mass Distribution of Horizontal Branch Stars in M3 (NGC 5272)
• Constraints on the Galactic Inner Halo Assembly History from the Age Gradient of Blue Horizontal-branch Stars
• Calibrating the BHB Star Distance Scale and the Halo Kinematic Distance to the Galactic Centre
• A Simulated Annealing algorithm to quantify patterns in astronomical data

Cited by in corpus (3)

• Mapping the anisotropic Galactic stellar halo with Blue Horizontal Branch stars
• Exploring the interaction between the MW and LMC with a large sample of blue horizontal branch stars from the DESI survey
• A Pristine-UNIONS view on the Galaxy: Kinematics of the distant spur feature of the Sagittarius stream traced by Blue Horizontal Branch stars