Structure of the outer Galactic disc with Gaia-DR2

Abstract

AIMS. We calculate the stellar density using star counts obtained from Gaia DR2 up to a Galactocentric distance R=20 kpc with a deconvolution technique for the parallax errors. Then we analyse the density in order to study the structure of the outer Galactic disc, mainly the warp. METHODS. In order to carry out the deconvolution, we used the Lucy inversion technique for recovering the corrected star counts. We also used the Gaia luminosity function of stars with $M_G<10$ to extract the stellar density from the star counts. RESULTS. The stellar density maps can be fitted by an exponential disc in the radial direction $h_r=2.07\pm 0.07$ kpc, with a weak dependence on the azimuth, extended up to 20 kpc without any cut-off. The flare and warp are clearly visible. The best fit of a symmetrical S-shaped warp gives $z_w=z_{\odot }+(37\pm 4.2(stat.)-0.91(syst.))$ pc $(R/R_{\odot }{)}^{2.42\pm 0.76(stat.)+0.129(syst.)}sin(\varphi +9.3\pm 7.37(stat.)+4.48(syst.))$ for the whole population. When we analyse the northern and southern warps separately, we obtain an asymmetry of an $\sim 25\%$ larger amplitude in the north. This result may be influenced by extinction because the Gaia G band is quite prone to extinction biases. However, we tested the accuracy of the extinction map we used, which shows that the extinction is determined very well in the outer disc. Nevertheless, we recall that we do not know the full extinction error, and neither do we know the systematic error of the map, which may influence the final result. The analysis was also carried out for very luminous stars alone ($M_G<-2$), which on average represents a younger population. We obtain similar scale-length values, while the maximum amplitude of the warp is $20-30\%$ larger than with the whole population. The north-south asymmetry is maintained.

arXiv comment19 pages, 21 figures, accepted to be published in A&A

References in corpus (46)

• 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 Gaia mission
• Gaia Data Release 2: The astrometric solution
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• Gaia Data Release 2: using Gaia parallaxes
• Modelling the Galactic Interstellar Extinction Distribution in Three Dimensions
• Gaia Data Release 2: Catalogue validation
• Milky Way Cepheid Standards for Measuring Cosmic Distances and Application to Gaia DR2: Implications for the Hubble Constant
• A Three-Dimensional Map of Milky-Way Dust
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• The spatial structure of mono-abundance sub-populations of the Milky Way disk
• A three-dimensional Galactic extinction model
• The Distribution of Nearby Stars in Velocity Space Inferred from Hipparcos Data
• Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• Old stellar Galactic disc in near-plane regions according to 2MASS: scales, cut-off, flare and warp
• On Galactic density modeling in the presence of dust extinction
• Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18
• Stellar populations in the Milky Way bulge region : Towards solving the Galactic bulge and bar shapes using 2MASS data
• StarHorse: A Bayesian tool for determining stellar masses, ages, distances, and extinctions for field stars
• The Vertical Structure of the Outer Milky Way HI Disk
• A three-dimensional map of the Milky Way using classical Cepheid variable stars
• Confirmation of the $Gaia$ DR2 parallax zero-point offset using asteroseismology and spectroscopy in the $Kepler$ field
• The Milky Way's external disc constrained by 2MASS star counts
• An intuitive 3D map of the Galactic warp's precession traced by classical Cepheids
• Warp, Waves, and Wrinkles in the Milky Way
• The Galactic warp revealed by Gaia DR2 kinematics
• Warped Galaxies From Misaligned Angular Momenta
• Evolution over time of the Milky Way's disc shape
• Generation of galactic disc warps due to intergalactic accretion flows onto the disc
• Flare in the Galactic stellar outer disc detected in SDSS-SEGUE data
• Revised Geometric Estimates of the North Galactic Pole and the Sun's Height Above the Galactic Midplane
• The Edge of the Milky Way Stellar Disk Revealed Using Clump Giant Stars as Distance Indicators
• The Edge of the Galactic Disc
• Mapping the Milky Way with LAMOST I: Method and overview
• Formation of Warped Disks by Galactic Fly-by Encounters. I. Stellar Disks
• A Gaia DR2 Mock Stellar Catalog
• Inversion of stellar statistics equation for the Galactic Bulge
• The Information Of The Milky Way From 2MASS Whole Sky Star Count: The Structure Parameters
• The Structure of the Outer Galactic Disc as revealed by IPHAS early A Stars
• Gaia-DR2 extended kinematical maps. Part I: Method and application
• Evidence for a deficit of young and old stars in the Milky Way inner in-plane disc
• Vertical velocities from proper motions of red clump giants
• Gaia-DR2 extended kinematical maps. Part II: Dynamics in the Galactic disk explaining radial and vertical velocities
• A star cluster at the edge of the Galaxy

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