Understanding the formation and evolution of our Galaxy requires accurate distances , ages and chemistry for large populations of field stars .
Here we present several updates to our spectro-photometric distance code , that can now also be used to estimate ages , masses , and extinctions for individual stars .
Given a set of measured spectro-photometric parameters , we calculate the posterior probability distribution over a given grid of stellar evolutionary models , using flexible Galactic stellar-population priors .
The code ( called StarHorse ) can acommodate different observational datasets , prior options , partially missing data , and the inclusion of parallax information into the estimated probabilities .
We validate the code using a variety of simulated stars as well as real stars with parameters determined from asteroseismology , eclipsing binaries , and isochrone fits to star clusters .
Our main goal in this validation process is to test the applicability of the code to field stars with known Gaia -like parallaxes .
The typical internal precision ( obtained from realistic simulations of an APOGEE+ Gaia -like sample ) are \simeq 8 \% in distance , \simeq 20 \% in age , \simeq 6 \% in mass , and \simeq 0.04 mag in A _ { V } .
The median external precision ( derived from comparisons with earlier work for real stars ) varies with the sample used , but lies in the range of \simeq [ 0 , 2 ] \% for distances , \simeq [ 12 , 31 ] \% for ages , \simeq [ 4 , 12 ] \% for masses , and \simeq 0.07 mag for A _ { V } .
We provide StarHorse distances and extinctions for the APOGEE DR14 , RAVE DR5 , GES DR3 and GALAH DR1 catalogues .