Fakultät für Physik und Astronomie
STEPHEN PHILLIPS hostreviews.co.uk / UNSPLASH

MALT: Milky Way Archaeology using RR Lyrae and Type-II Cepheids

Hitesh Lala , ARI

RR Lyraes and Type-II Cepheids are old, low-mass variable stars and are invaluable distance indicators. We have created a comprehensive catalog of ~250,000 RR Lyraes and ~4000 Type-II & Anomalous Cepheids containing 7-D information (positions, proper motions, distances, radial velocities, metallicities). In the process, we have homogeneously combined 10 photometric and 6 spectroscopic surveys. Gaia EDR3 proper motions (and parallaxes) are available for ~95% of the sample. Using EDR3 parallaxes, along with the LMC population, we have derived new period-luminosity(-metallicity) and period-Wesenheit(-Metallicity) relationships in the Gaia DR2 & EDR3 GBPRP, VI, griz, JHKs, and W12 bands for all the sub-types (RRab, RRc, BL Her, W Vir, pW Vir, RV Tau, ACep_F, ACep_1O). Simultaneously solving the P-L/W relationships, we have computed individual reddenings (~15% uncertainty) to our sample stars. For our RR Lyrae sample (both RRab and RRc sub-types), we have also obtained photometric metallicity estimates on a new homogeneous scale creating the largest sample of RR Lyrae iron-abundances. Putting it all together, we have computed precise distances (~5% uncertainty) for an unprecedented number of RR Lyraes and Type-II Cepheids resulting in the most complete catalog yet of these populations. Harnessing this catalog, we have discovered many new members of Galactic streams and over-densities. For a few well-studied substructures like Orphan, Pal 5, GD-1, Sagittarius, etc., the re-discovery of known members helps us present more precise distances and metallicities for them, while the new ones enable precise measurement of these parameters for the very first time for many of the less-studied substructures. Our catalog places the community in a good state to exploit the imminent arrival of numerous spectra from WEAVE, 4MOST, DESI, Gaia DR3/4 and ultimately facilitate not only the chemo-dynamically analysis but also the discovery of several other streams and over-densities. The homogeneity of our catalog can also be exploited to uniformly study the Milky Way halo at unrivaled depths.

ARI Institute Colloquium
22 Jul 2021, 11:15
ARI, Moenchhofstrasse 12-14, Seminarraum 1, 1.OG

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