Browsing by Author "Duffau, Sonia"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- ItemDISENTANGLING THE VIRGO OVERDENSITY WITH RR LYRAE STARS(IOP PUBLISHING LTD, 2016) Vivas, A. Katherina; Zinn, Robert; Farmer, John; Duffau, Sonia; Ping, YidingWe use a combination of spatial distribution and radial velocity to search for halo substructures in a sample of 412 RR Lyrae stars (RRLSs) that covers a. region of similar to 525 square degrees. of the Virgo overdensity (VOD) and spans distances from the Sun from 4 to 75 kpc. With a friends-of-friends algorithm we identified six high-significance groups of RRLSs in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high-significance and three. lower-significance groups have distances between similar to 10 and 20 kpc, which places them in the distance range attributed by others to the VOD. The largest of these is the Virgo stellar stream. at 19 kpc, which has 18 RRLSs, a factor of two increase over the number known previously. While these VOD groups are distinct according to our selection criteria, their overlap in position and distance. and, in a few cases, similarity in radial velocity are suggestive that they may not all stem from separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sagittarius (Sgr). stream is a very obvious feature in the background of the VOD at a mean distance of 44 kpc. Two additional high-significance. groups were detected at distances >40 kpc. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.
- ItemRR Lyrae stars as tracers of halo substructures(2017) Duffau, Sonia; Vivas, A. Katherina; Navarrete, Camila; Carballo-Bello, Julio; Hajdu, Gergel; Catelan, MarcioThree RR Lyrae overdensity candidates in the southern sky have been studied using low resolution spectra obtained with the Goodman spectrograph at SOAR. We search for unidentified velocity peaks indicative of the possible presence of streams within the overdensities. Our results suggest that all three overdensities present an excess of radial velocity signal at high mean radial velocities which cannot be explained as a contribution from any known Galactic component....
- ItemSearching for fossil remnants in the Galactic halo: photometric follow-up of southern CRTScandidates(2015) Chan, Siukuen Josephine; Navarrete, Camila; Catelan, Marcio; Duffau, Sonia; Torrealba, Gabriel. I.; Drake, Andrew J.; Belokurov, Vasily; Koposov, SergeyObservations of the fossil record of the early formation stages of the Milky Way galaxy provide important constraints on cosmological scenarios for the formation of large galaxies like our own. While the northern celestial hemisphere has been extensively examined for the presence and degree of halo substructure, the southern halo has until recently remained "terra incognita" for such studies. However, based on RR Lyrae stars detected in the course of the Catalina Real-time Transients Survey (CRTS), our team has identified a number of new candidate overdensities in the southern Galactic halo (Torrealba et al. 2015, MNRAS, 446, 2251). Here we describe some preliminary results of a deeper search for the Torrealba et al. overdensity candidates, using photometric data from selected wide-field surveys that have mapped the immediate vicinity of some of the more promising among these candidates....
- ItemWhiting 1: Confirmation of its accretion by the Milky Way(2017) Carballo-Bello, Julio A.; Corral-Santana, Jesús M.; Martínez-Delgado, David; Sollima, Antonio; Muñoz, Ricardo R.; Duffau, Sonia; Catelan, MarcioWe investigate the association of Whiting 1 with the Sagittarius tidal stream by obtaining radial velocities for a sample of 101 stars observed with VIMOS. Our results reveal the presence of a component of the Sagittarius tidal stream with a radial velocity - and distance - compatible with that of the globular cluster. Therefore, we conclude that Whiting1 was formed in the interior of the Sagittarius dwarf spheroidal galaxy and later accreted by the Milky Way. In addition, our data also reveal the detection for the first time of an ancient wrap of the Sagittarius tidal stream along the same line-of-sight and at the same heliocentric distance....