Abstract
Context.WhileGaiaenables us to probe the extended local neighbourhood in great detail, the thin disc structure at larger distances remains sparsely explored.Aims.We aim here to build a non-parametric 3D model of the thin disc structures handling both the extinction and the stellar density simultaneously.Methods.We developed a Bayesian deconvolution method in two dimensions: extinction and distance. It uses a reference catalogue whose completeness information defines the selection function. It is designed so that any complementary information from other catalogues can be added. It has also been designed to be robust to outliers, which are frequent in crowded fields, and differential extinction. The prior information is designed to be minimal: only a reference H-R diagram. We derived for this an empirical H-R diagram of the thin disc usingGaiaDR2 data, but synthetic isochrone-based H-R diagrams can also be used.Results.We validated the method on simulations and real fields using 2MASS and UKIDSS data complemented byGaiaDR2 photometry and parallaxes. We detail the results of two test fields: a 2MASS field centred around the NGC 4815 open cluster, which shows an over-density of both extinction and stellar density at the cluster distance, and a UKIDSS field atl = 10° where we recover the position of the Galactic bar.
Highlights
We used 711 2MASS stars located in an area of 0.1◦x0.1◦ around l = 306.6◦, b = −2.1◦; 87% of those stars have Gaia parallaxes. This field is complex for FEDReD as it suffers from differential extinction requiring a very small field of view and a small number of stars, and has the presence of a cluster that differs from the mix of age and metallicities of our empirical H-R diagram (HRD)
We presented here a Bayesian deconvolution method, FEDReD, allowing us to derive the extinction distribution and stellar density maps at the same time, taking into account the incompleteness of the surveys
We showed the performances of the algorithm on simulated data and on two test fields, one using 2MASS data centred around NGC 4815 and another using UKIDSS data towards the galactic bar at l = 10◦
Summary
Uncovering the Galactic structure within the Galactic plane is a challenging issue due to the mix between stars and dust at different distances, the dust affecting the light of the stars, which becomes fainter and redder. Non-parametric stellar density models have been derived up to now when the extinction could be handled independently, for example assuming that most of the extinction occurs in the foreground of the structure under study: this is suitable at high galactic latitudes (e.g. de Jong et al 2008) and for the bulge structure outside of the Galactic plane (e.g. López-Corredoira et al 2000; Wegg & Gerhard 2013, both using deconvolution methods). We wish to work within the Galactic plane and derive the non-parametric distribution of both the extinction and the stellar density at the same time. This is the first time this has been attempted in the Galactic disc.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
