Dwarfs or giants? Stellar metallicities and distances in the Canada-France-Imaging-Survey from $ugrizG$ multi-band photometry

Abstract

We present a new fully data-driven algorithm that uses photometric data from the Canada-France-Imaging-Survey (CFIS; $u$), Pan-STARRS 1 (PS1; $griz$), and Gaia ($G$) to discriminate between dwarf and giant stars and to estimate their distances and metallicities. The algorithm is trained and tested using the SDSS/SEGUE spectroscopic dataset and Gaia photometric/astrometric dataset. At [Fe/H]$<-1.2$, the algorithm succeeds in identifying more than 70% of the giants in the training/test set, with a dwarf contamination fraction below 30% (with respect to the SDSS/SEGUE dataset). The photometric metallicity estimates have uncertainties better than 0.2 dex when compared with the spectroscopic measurements. The distances estimated by the algorithm are valid out to a distance of at least $\sim 80$ kpc without requiring any prior on the stellar distribution, and have fully independent uncertainities that take into account both random and systematic errors. These advances allow us to estimate these stellar parameters for approximately 12 million stars in the photometric dataset. This will enable studies involving the chemical mapping of the distant outer disc and the stellar halo, including their kinematics using the Gaia proper motions. This type of algorithm can be applied in the Southern hemisphere to the first release of LSST data, thus providing an almost complete view of the external components of our Galaxy out to at least $\sim 80$ kpc. Critical to the success of these efforts will be ensuring well-defined spectroscopic training sets that sample a broad range of stellar parameters with minimal biases. A catalogue containing the training/test set and all relevant parameters within the public footprint of CFIS is available online.

arXiv comment27 pages. 21 Figures. Accepted for publication in AAS. Training/testing sample available at: http://www.canfar.net/storage/list/gthomas/dwarfOrGiants.fits

References in corpus (35)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Gaia Data Release 2: The astrometric solution
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Evolution of asymptotic giant branch stars II. Optical to far-infrared isochrones with improved TP-AGB models
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• Gaia Data Release 2: Photometric content and validation
• Gaia Data Release 2: using Gaia parallaxes
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• The SEGUE Stellar Parameter Pipeline. I. Description and Initial Validation Tests
• Estimating distances from parallaxes
• Detection of a 63 Degree Cold Stellar Stream in the Sloan Digital Sky Survey
• Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18
• StarHorse: A Bayesian tool for determining stellar masses, ages, distances, and extinctions for field stars
• The Gaia astrophysical parameters inference system (Apsis). Pre-launch description
• Constraining the Milky Way Halo Potential with the GD-1 stellar stream
• Off the beaten path: Gaia reveals GD-1 stars outside of the main stream
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• Tracing the formation of the Milky Way through ultra metal-poor stars
• The Canada-France Imaging Survey: First results from the u-band component
• The SEGUE K giant survey II: A Catalog of Distance Determinations for the SEGUE K giants in the Galactic Halo
• 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
• Improved distances and ages for stars common to TGAS and RAVE
• Spectrophotometric parallaxes with linear models: Accurate distances for luminous red-giant stars
• Pan-STARRS1: Galaxy Clustering in the Small Area Survey 2
• The stellar halo of the Milky Way traced by blue horizontal-branch stars in the Subaru Hyper Suprime-Cam Survey
• A new study of the variable star population in the Hercules globular cluster (M13; NGC 6205)
• Precision distances to dwarf galaxies and globular clusters from Pan-STARRS1 3$\pi$ RR Lyrae
• Chemical Mapping of the Milky Way With The Canada-France Imaging Survey: A Non-parametric Metallicity-Distance Decomposition of the Galaxy
• A-type stars in the Canada-France Imaging Survey II. Tracing the height of the disc at large distances with Blue Stragglers
• Unbiased TGAS$\times$LAMOST distances and the role of binarity