The Dynamics of the Galactic Bulge: Uncovering the Old Populations that Formed Before the Bar

Wed 11 Dec 2019

Space Telescope Science Institute (STScI)
3700 San Martin Drive
Baltimore, MD 21218


2:45 PM - 4:00 PM

Contact Information:

Have questions? Please contact Kevin Schlaufman and David Nataf.


Using mainly bulge red clump giants (RCG) and giants as tracers, a picture has emerged of the Galactic bulge consisting of a rotating peanut-shaped structure made up largely of old and metal-rich stars (~10 Gyr, [Fe/H] falling between -0.5 and +0.5 dex).  However, there is a more metal-poor population of stars present in the bulge, a scarcer, lesser explored population of stars.  I will present results from our spectroscopic survey of bulge RR Lyrae variables, tracers of possibly the oldest and most metal-poor stars in the bulge ([Fe/H] peaking at -1.0 dex).  To date, we have obtained spectra of ~3000 OGLE bulge RR Lyrae stars in ten 2 degree windows.  Our results indicate that the RR Lyrae stars exhibit hot kinematics and null or negligible rotation and are therefore members of a separate population from the bar/pseudobulge that currently dominates the mass and luminosity of the inner Galaxy.  Our RR Lyrae stars predate these structures, and have metallicities, kinematics, and spatial distribution that are consistent with a "classical" bulge, or an inner halo.

Speaker: Andrea Kunder (Saint Martin's University)


All 2019 Fall Colloquia talks are held on Wednesdays in the STScI John N. Bahcall Auditorium at 3:00 p.m. preceded by tea at 2:45 p.m.

Please direct questions or comments to the contact above. The 2019-20 committee members are Paule Sonnentrucker (STScI Chair), Annalisa Calamida (STScI), Will Fischer (STScI), Ethan Vishniac (JHU Co-chair), Kevin Schlaufman (JHU), and Graeme Addison (JHU).