A New Sample of Cool Subdwarfs from SDSS: Properties and Kinematics

Abstract

We present a new sample of M subdwarfs compiled from the 7th data release of the Sloan Digital Sky Survey. With 3517 new subdwarfs, this new sample significantly increases the number of spectroscopically confirmed low-mass subdwarfs. This catalog also includes 905 extreme and 534 ultra sudwarfs. We present the entire catalog including observed and derived quantities, and template spectra created from co-added subdwarf spectra. We show color-color and reduced proper motion diagrams of the three metallicity classes, which are shown to separate from the disk dwarf population. The extreme and ultra subdwarfs are seen at larger values of reduced proper motion as expected for more dynamically heated populations. We determine 3D kinematics for all of the stars with proper motions. The color-magnitude diagrams show a clear separation of the three metallicity classes with the ultra and extreme subdwarfs being significantly closer to the main sequence than the ordinary subdwarfs. All subdwarfs lie below (fainter) and to the left (bluer) of the main sequence. Based on the average $(U,V,W)$ velocities and their dispersions, the extreme and ultra subdwarfs likely belong to the Galactic halo, while the ordinary subdwarfs are likely part of the old Galactic (or thick) disk. An extensive activity analysis of subdwarfs is performed using H$\alpha$ emission and 208 active subdwarfs are found. We show that while the activity fraction of subdwarfs rises with spectral class and levels off at the latest spectral classes, consistent with the behavior of M dwarfs, the extreme and ultra subdwarfs are basically flat.

arXiv comment66 pages, 23 figures, accepted in ApJ

References in corpus (41)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• The Sloan Digital Sky Survey: Technical Summary
• Local Kinematics and the Local Standard of Rest
• Constraining the Age-Activity Relation for Cool Stars: The SDSS DR5 Low-Mass Star Spectroscopic Sample
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• A Catalog of Northern Stars With Annual Proper Motions Larger Than 0.15 Seconds of Arc (LSPM catalog - North)
• The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk: II. The Field
• M-Subdwarfs: Spectroscopic Classification and the Metallicity Scale
• The Palomar/MSU Nearby Star Spectroscopic Survey III: Chromospheric Activity, M-dwarf Ages and the Local Star Formation History
• Spectroscopic Properties of Cool Stars in the SDSS: An Analysis of Magnetic Activity and a Search for Subdwarfs
• Discoveries from a Near-infrared Proper Motion Survey using Multi-epoch 2MASS Data
• The Sloan Digital Sky Survey Data Release 7 Spectroscopic M Dwarf Catalog I: Data
• Low-Mass Dwarf Template Spectra from the Sloan Digital Sky Survey
• The Brown Dwarf Kinematics Project (BDKP) I. Proper Motions and Tangential Velocities for a Large Sample of Late-type M, L and T Dwarfs
• A Spectroscopic Catalog of the Brightest (J<9) M Dwarfs in the Northern Sky
• Revised metallicity classes for low-mass stars: dwarfs (dM), subdwarfs (sdM), extreme subdwarfs (esdM), and ultra subdwarfs (usdM)
• Prospecting in late-type dwarfs: a calibration of infrared and visible spectroscopic metallicities of late-K and M dwarfs spanning 1.5 dex
• Spectroscopy of New High Proper Motion Stars in the Northern Sky. I. New Nearby Stars, New High Velocity Stars, and an Enhanced Classification Scheme for M Dwarfs
• Colors and Kinematics of L Dwarfs From the Sloan Digital Sky Survey
• M Dwarfs in SDSS Stripe 82: Photometric Light Curves and Flare Rate Analysis
• The Solar Neighborhood XIII: Parallax Results from the CTIOPI 0.9-m Program -- Stars with mu >= 1"/year (MOTION Sample)
• Characteristics of the Galaxy according to Cepheids
• Optical Spectroscopy of 2MASS Color-Selected Ultracool Subdwarfs
• The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk: I. The Calibration Region
• The χFactor: Determining the Strength of Activity in Low Mass Dwarfs
• Cool Subdwarf Investigations (CSI) I: New Thoughts for the Spectral Types of K and M Subdwarfs
• Using the Galactic Dynamics of M7 Dwarfs to Infer the Evolution of Their Magnetic Activity
• The kinematics of late type stars in the solar cylinder studied with SDSS data
• The Solar Neighborhood XXIV. Parallax Results from the CTIOPI 0.9-m Program: Stars with $\mu$ $\ge$ 1\farcs0 yr${}^{-1}$ (MOTION Sample) and Subdwarfs
• The Effects of Close Companions (and Rotation) on the Magnetic Activity of M Dwarfs
• Ultra-cool dwarfs: new discoveries, proper motions, and improved spectral typing from SDSS and 2MASS photometric colors
• Refined Metallicity Indices for M Dwarfs Using the SLoWPoKES Catalog of Wide, Low-mass Binaries
• Twenty-three new ultra-cool subdwarfs from the Sloan Digital Sky Survey
• The Solar Neighborhood XV: Discovery of New High Proper Motion Stars with mu >= 0.4"/yr between Declinations -47 degrees and 00 degrees
• Constraints on thick disc and halo parameters from HST photometry of field stars in the Galaxy
• Chi Values for Blue Emission Lines in M Dwarfs
• New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools: Part I: UKIDSS LAS DR5 vs SDSS DR7
• The Solar Neighborhood XII: Discovery of New High Proper Motion Stars with 1.0"/yr > mu >= 0.4"/yr between Declinations -90 degrees and -47 degrees
• Identifying Ultra-Cool Dwarfs at Low Galactic Latitudes: A Southern Candidate Catalogue
• Mapping the Local Halo: Statistical Parallax Analysis of SDSS Low-Mass Subdwarfs
• Ages of White Dwarf-Red Subdwarf Systems

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• The Solar Neighborhood XLII. Parallax Results from the CTIOPI 0.9-m Program --- Identifying New Nearby Subdwarfs Using Tangential Velocities and Locations on the H-R Diagram
• M Subdwarf Research. II. Atmospheric Parameters and Kinematics
• Collisions of Terrestrial Worlds: The Occurrence of Extreme Mid-Infrared Excesses around Low-Mass Field Stars
• Wide companions to M and L subdwarfs with Gaia and the Virtual Observatory
• Discovery of a Possible Cool White Dwarf Companion from the AllWISE Motion Survey
• M dwarfs and the fraction of high carbon-to-oxygen stars in the solar neighbourhood
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• Search for Ultraviolet Luminous Objects in GALEX data