Contatto di riferimento: Donatella Romano
Partecipanti: Andrea Kunder (AIP, Potsdam, DE)
Abstract
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 ~1000 OGLE bulge RR Lyrae stars in four 2 degree windows for which NIR-photometry from the VVV surveys exists. Therefore, our RR Lyrae stars have accurate (3%) distances based on near infrared light curves. 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, although we cannot yet completely rule out the possibility that they are the metal-poor tail of a more metal rich ([Fe/H] ~ -1 dex) halo-bulge population.
See you tomorrow in sala seminari, Via Ranzani 1, floor -1, on time at 14:00.
Next seminars:
* Thursday May 5th, at 14:00
Ivan Cabrera-Ziri (Liverpool John Moore Univ., UK and ESO, DE)
* Thursday May 12th, at 14:00
Sirio Belli (MPE, Garching, DE)
* Tuesday May 17th, at 14:00, AULA DELLA SPECOLA
Daniela Calzetti (Dept. of Astronomy, Univ. of Massachusetts, US)
* Thursday May 26th, at 14:00
Valentina D'Orazi (INAF, Oss. Astron. di Padova)
The complete list of seminars is available at: http://davide2.bo.astro.it/?page_id=4531
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