S317p.30 — Near-Field Cosmology with RR Lyrae Variable Stars: A first view of substructure in the Southern Sky

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Aug 4th at 6:00 PM until 6:00 PM

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Author(s): Camila Navarrete3, Sonia Duffau4, Márcio Catelan3, Anna Katherina Vivas1, Gergely Hajdu3, Gabriel Torrealba2

Institution(s): 1. Cerro Tololo Interamerican Observatory, 2. Institute of Astronomy, University of Cambridge, 3. Institute of Astrophysics, Pontificia Universidad Catolica de Chile, 4. Millennium Institute of Astrophysics


The arrival of the SDSS revealed that the northern-hemisphere halo has plenty of substructures (e.g., the Field of Streams; Belokurov et al. 2006). The southern-hemisphere sky, on the other hand, remains a "terra incognita" where only recently some substructure candidates have been found, thanks to ongoing wide-field surveys. Extending the census of halo overdensities to the southern sky is important as these structures provide clues into the Milky Way's merger history. Very recently, more than 20 southern overdensity candidates were found, using RR Lyrae data from the Catalina Real-time Transient Survey (Torrealba et al, 2015). However, the confirmation of those RR Lyrae overdensities as remnants of protogalactic fragments that may have helped build the present-day Galactic halo requires spectroscopic confirmation, in order to distinguish, using radial velocities and chemical information alike, bona-fide overdensities from random clumping among halo field stars. In this contribution, we will present preliminary results of a spectroscopic follow-up of several of the Torrealba et al. southern overdensity candidates, based on low-resolution spectra obtained with the SOAR and Magellan telescopes.