my first Monday at MPIA

[Very few posts for the last few days, because I was on a mini-vacation and getting ready for the annual move to Heidelberg.]

My research day started in the garden with Rix, looking at Anna Ho's paper using The Cannon to transfer APOGEE-like stellar parameter labels onto stars with LAMOST spectra. We worked through the figures and made comments.

At the weekly PanSTARRS meeting, Nina Hernitschek (MPIA) showed beautiful samples of QSO candidates and RR Lyrae candidates found with time-domain analysis. Her method involves Gaussian-process modeling multi-band time-domain data, and then a supervised classification. The results are very convincing: For example, on a map of the sky with the MW dwarf galaxies and star clusters circled, there are clear overdensities of RRL stars in many of the circles. Also, the RRL stars clearly trace the MW halo, bulge, and disk. She also has incredible 3π maps of QSOs, which are amazingly isotropic near the Galactic poles, but also have many QSOs in (or near) the disk plane and even behind the Galactic center. I bet she has the best low-latitude QSO sample ever.

At lunch-time I had a conversation with Laura Inno (MPIA), Rix, Eddie Schlafly (MPIA), and others about Cepheid stars in the Milky Way disk. There should be tens of thousands but hundreds are known. Rix gave some very good reasons for finding them all: Cepheids are very young stars but they are cool (5000 K) not hot, so you can measure their abundances. They are also luminous, so you can see them at large distance and through the dust. We discussed how to find them with PanSTARRS and WISE data, perhaps starting from what Hernitschek has already done.