The Photo-Astrometric Vertical Tracer Density of the Milky Way I: The Method

Abstract

We introduce a method to infer the vertical distribution of stars in the Milky Way using a Poisson likelihood function, with a view to applying our method to the Gaia catalogue. We show how to account for the sample selection function and for parallax measurement uncertainties. Our method is validated against a simulated sample drawn from a model with two exponential discs and a power-law halo profile. A mock Gaia sample is generated using the Gaia astrometry selection function, whilst realistic parallax uncertainties are drawn from the Gaia Astrometric Spread Function. The model is fit to the mock in order to rediscover the input parameters used to generate the sample. We recover posterior distributions which accurately fit the input parameters to within statistical uncertainties, demonstrating the efficacy of our method. Using the GUMS synthetic Milky Way catalogue we find that our halo parameter fits can be heavily biased by our overly simplistic model, however, the fits to the thin and thick discs are not significantly impacted. We apply this method to Gaia Early Data Release 3 in a companion paper where we also quantify the systematic uncertainties introduced by oversimplifications in our model.

Accepted for publication in MNRAS

References in corpus (22)

• The Gaia mission
• Gaia Early Data Release 3: The astrometric solution
• Improving PARSEC models for very low mass stars
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• Gaia Early Data Release 3: The Gaia Catalogue of Nearby Stars
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances
• Constraining the thick disc formation scenario of the Milky Way
• The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs
• A radial age gradient in the geometrically thick disk of the Milky Way
• Touching The Void: A Striking Drop in Stellar Halo Density Beyond 50 kpc
• Completeness of the Gaia-verse II: what are the odds that a star is missing from Gaia DR2?
• Spatial distribution and galactic model parameters of cataclysmic variables
• Galactic longitude dependent Galactic model parameters
• Selection Functions in Astronomical Data Modeling, with the Space Density of White Dwarfs as Worked Example
• Completeness of the Gaia-verse I: when and where were Gaia's eyes on the sky during DR2?
• The stellar halo of the Milky Way traced by blue horizontal-branch stars in the Subaru Hyper Suprime-Cam Survey
• Completeness of the Gaia-verse IV: The Astrometry Spread Function of Gaia DR2
• Completeness of the Gaia-verse V: Astrometry and Radial Velocity sample selection functions in Gaia EDR3
• Completeness of the Gaia-verse III: using hidden states to infer gaps, detection efficiencies and the scanning law from the DR2 light curves
• A Bayesian Approach to the Vertical Structure of the Disk of the Milky Way

Cited by in corpus (4)

• Self-consistent models of our Galaxy
• Milky Way thin and thick disk kinematics with GAIA EDR3 and RAVE DR5
• Mapping Milky Way disk perturbations in stellar number density and vertical velocity using Gaia DR3
• Completeness of the Gaia-verse V: Astrometry and Radial Velocity sample selection functions in Gaia EDR3