Bibcode
Majewski, Steven R.; Hasselquist, Sten; Łokas, Ewa L.; Nidever, David L.; Frinchaboy, Peter M.; García Pérez, Ana E.; Johnston, Kathryn V.; Mészáros, Sz.; Shetrone, Matthew; Allende-Prieto, C.; Beaton, Rachael L.; Beers, Timothy C.; Bizyaev, Dmitry; Cunha, Katia; Damke, Guillermo; Ebelke, Garrett; Eisenstein, Daniel J.; Hearty, Fred; Holtzman, Jon; Johnson, Jennifer A.; Law, David R.; Malanushenko, Viktor; Malanushenko, Elena; O'Connell, Robert W.; Oravetz, Daniel; Pan, Kaike; Schiavon, Ricardo P.; Schneider, Donald P.; Simmons, Audrey; Skrutskie, Michael F.; Smith, Verne V.; Wilson, John C.; Zasowski, Gail
Bibliographical reference
The Astrophysical Journal Letters, Volume 777, Issue 1, article id. L13, 7 pp. (2013).
Advertised on:
11
2013
Citations
32
Refereed citations
32
Description
The dynamics of the core of the Sagittarius (Sgr) dwarf spheroidal
(dSph) galaxy are explored using high-resolution (R ~ 22, 500), H-band,
near-infrared spectra of over 1000 giant stars in the central 3
deg2 of the system, of which 328 are identified as Sgr
members. These data, among some of the earliest observations from the
Sloan Digital Sky Survey III/Apache Point Observatory Galactic Evolution
Experiment (APOGEE) and the largest published sample of high resolution
Sgr dSph spectra to date, reveal a distinct gradient in the velocity
dispersion of Sgr from 11 to 14 km s–1 for radii
>0.°8 from center to a dynamical cold point of 8 km
s–1 in the Sgr center—a trend differing from that
found in previous kinematical analyses of Sgr over larger scales that
suggests a more or less flat dispersion profile at these radii.
Well-fitting mass models with either cored and cusped dark matter
distributions can be found to match the kinematical results, although
the cored profile succeeds with significantly more isotropic stellar
orbits than required for a cusped profile. It is unlikely that the cold
point reflects an unusual mass distribution. The dispersion gradient may
arise from variations in the mixture of populations with distinct
kinematics within the dSph; this explanation is suggested (e.g., by
detection of a metallicity gradient across similar radii), but not
confirmed, by the present data. Despite these remaining uncertainties
about their interpretation, these early test data (including some from
instrument commissioning) demonstrate APOGEE's usefulness for precision
dynamical studies, even for fields observed at extreme airmasses.
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Chemical Abundances in Stars
Stellar spectroscopy allows us to determine the properties and chemical compositions of stars. From this information for stars of different ages in the Milky Way, it is possible to reconstruct the chemical evolution of the Galaxy, as well as the origin of the elements heavier than boron, created mainly in stellar interiors. It is also possible to
Carlos
Allende Prieto