Abstract
Context. The first Gaia data release unlocked the access to photometric information for 1.1 billion sources in the G-band. Yet, given the high level of degeneracy between extinction and spectral energy distribution for large passbands such as the Gaia G-band, a correction for the interstellar reddening is needed in order to exploit Gaia data. Aims. The purpose of this manuscript is to provide the empirical estimation of the Gaia G-band extinction coefficient kG for both the red giants and main sequence stars in order to be able to exploit the first data release DR1. Methods. We selected two samples of single stars: one for the red giants and one for the main sequence. Both samples are the result of a cross-match between Gaia DR1 and 2MASS catalogues; they consist of high-quality photometry in the G-, J- and KS-bands. These samples were complemented by temperature and metallicity information retrieved from APOGEE DR13 and LAMOST DR2 surveys, respectively. We implemented a Markov chain Monte Carlo method where we used (G – KS)0 versus Teff and (J – KS)0 versus (G – KS)0, calibration relations to estimate the extinction coefficient kG and we quantify its corresponding confidence interval via bootstrap resampling. We tested our method on samples of red giants and main sequence stars, finding consistent solutions. Results. We present here the determination of the Gaia extinction coefficient through a completely empirical method. Furthermore we provide the scientific community with a formula for measuring the extinction coefficient as a function of stellar effective temperature, the intrinsic colour (G – KS)0, and absorption.
Highlights
When it comes to understanding the physics of disk galaxies, our location within the Milky Way plays an important role
While we tested the significance of high-order ai parameters with the Deviance Information Criterion (DIC) test, some coefficients in Table 3 appear as non-significant due to bootstrap errors being significantly larger than the MCMC derived ones
We present here the empirical estimation of the Gaia G-band extinction coefficient kG that can be used as a unique solution for both red giants and main sequence stars
Summary
When it comes to understanding the physics of disk galaxies, our location within the Milky Way plays an important role. By observing our visible sky and studying the astrophysical processes of its individual components, we can learn about the structure and dynamics of the Galaxy, and infer its formation and evolution. This prospect would not be possible only by examining other galaxies. In the midst of all these surveys, the mapping process of the Milky Way is culminating with Gaia, the ESA space mission that has just started providing data to study formation, dynamical, chemical and star-formation evolution (Perryman et al 2001; Gaia Collaboration 2016). Despite the unrivalled completeness of its information, Gaia, like the other surveys, does not rule out astrophysical selection effects such as interstellar extinction
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