Bayesian inference of T Tauri star properties using multi-wavelength survey photometry

Abstract

There are many pertinent open issues in the area of star and planet formation. Large statistical samples of young stars across star-forming regions are needed to trigger a breakthrough in our understanding, but most optical studies are based on a wide variety of spectrographs and analysis methods, which introduces large biases. Here we show how graphical Bayesian networks can be employed to construct a hierarchical probabilistic model which allows pre-main sequence ages, masses, accretion rates, and extinctions to be estimated using two widely available photometric survey databases (IPHAS r/i/Halpha and 2MASS J-band magnitudes.) Because our approach does not rely on spectroscopy, it can easily be applied to homogeneously study the large number of clusters for which Gaia will yield membership lists. We explain how the analysis is carried out using the Markov Chain Monte Carlo (MCMC) method and provide Python source code. We then demonstrate its use on 587 known low-mass members of the star-forming region NGC 2264 (Cone Nebula), arriving at a median age of 3.0 Myr, an accretion fraction of 20+/-2% and a median accretion rate of 10^-8.4 Msol/yr. The Bayesian analysis formulated in this work delivers results which are in agreement with spectroscopic studies already in the literature, but achieves this with great efficiency by depending only on photometry. It is a significant step forward from previous photometric studies, because the probabilistic approach ensures that nuisance parameters, such as extinction and distance, are fully included in the analysis with a clear picture on any degeneracies.

17 pages & 14 figures. Accepted for publication in MNRAS

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• Gaia 19ajj: A Young Star Brightening Due to Enhanced Accretion + Reduced Extinction
• Pre-main sequence accretion in the low metallicity Galactic star-forming region Sh 2-284
• A study of light travel time effect in short-period MOA eclipsing binaries via eclipse timing
• Photometric determination of the mass accretion rates of pre-main sequence stars. VI. The case of LH 95 in the Large Magellanic Cloud
• Mon-735: A new low-mass pre-main sequence eclipsing binary in NGC 2264
• Infrared polarimetry of Mrk 231: Scattering off hot dust grains in the central core
• LkH$\alpha$ 225 (V1318 Cyg) South in Outburst
• Population-based identification of Hα-excess sources in the Gaia DR2 and IPHAS catalogues
• Young Stellar Object candidates toward the Orion region selected from GALEX
• Linear line spectropolarimetry of Herbig Ae/Be stars
• Dichroic polarization at mid-infrared wavelengths: a Bayesian approach