Interstellar medium, young stars, and astrometric binaries in Galactic archaeology spectroscopic surveys

TL;DR

This paper discusses how ongoing spectroscopic surveys of the Milky Way enable auxiliary scientific studies of the interstellar medium, young stars, and binary systems, providing insights into Galactic structure, star formation, and stellar masses.

Contribution

It highlights the potential of current surveys to advance auxiliary science in Galactic archaeology, including interstellar medium mapping, young star identification, and binary mass determination.

Findings

Interstellar medium can be studied via diffuse bands and atomic absorptions.

Emission spectra serve as indicators of stellar youth.

Astrometric binaries can have their masses accurately determined.

Abstract

Current ongoing stellar spectroscopic surveys (RAVE, GALAH, Gaia-ESO, LAMOST, APOGEE, Gaia) are mostly devoted to studying Galactic archaeology and structure of the Galaxy. But they allow for important auxiliary science: (i) Galactic interstellar medium can be studied in four dimensions (position in space + radial velocity) through weak but numerous diffuse insterstellar bands and atomic absorptions seen in spectra of background stars, (ii) emission spectra which are quite frequent even in field stars can serve as a good indicator of their youth, pointing e.g. to stars recently ejected from young stellar environments, (iii) astrometric solution of the photocenter of a binary to be obtained by Gaia can yield accurate masses when joined by spectroscopic information obtained serendipitously during a survey. These points are illustrated by first results from the first three surveys mentioned above. These hint at the near future: spectroscopic studies of the dynamics of the interstellar medium can identify and quantify Galactic fountains which may sustain star formation in the disk by entraining fresh gas from the halo; RAVE already provided a list of ~14,000 field stars with chromosperic emission in Ca II lines, to be supplemented by many more observations by Gaia in the same band, and by GALAH and Gaia-ESO observations of Balmer lines; several millions of astrometric binaries with periods up to a few years which are being observed by Gaia can yield accurate masses when supplemented with measurements from only a few high-quality ground based spectra.