Bibcode
Siegel, Michael H.; Majewski, Steven R.; Law, David R.; Sarajedini, Ata; Dotter, Aaron; Marín-Franch, A.; Chaboyer, Brian; Anderson, Jay; Aparicio, A.; Bedin, Luigi R.; Hempel, Maren; Milone, A. P.; Paust, Nathaniel; Piotto, Giampaolo; Reid, I. Neill; Rosenberg, A.
Referencia bibliográfica
The Astrophysical Journal, Volume 743, Issue 1, article id. 20 (2011).
Fecha de publicación:
12
2011
Revista
Número de citas
38
Número de citas referidas
35
Descripción
We use observations from the Hubble Space Telescope Advanced Camera for
Surveys (HST/ACS) study of Galactic globular clusters to investigate the
spatial distribution of the inner regions of the disrupting Sagittarius
dwarf spheroidal galaxy (Sgr). We combine previously published analyses
of four Sgr member clusters located near or in the Sgr core (M54, Arp 2,
Terzan 7, and Terzan 8) with a new analysis of diffuse Sgr material
identified in the background of five low-latitude Galactic bulge
clusters (NGC 6624, 6637, 6652, 6681, and 6809) observed as part of the
ACS survey. By comparing the bulge cluster color-magnitude diagrams to
our previous analysis of the M54/Sgr core, we estimate distances to
these background features. The combined data from four Sgr member
clusters and five Sgr background features provide nine independent
measures of the Sgr distance and, as a group, provide uniformly measured
and calibrated probes of different parts of the inner regions of Sgr
spanning 20° over the face of the disrupting dwarf. This allows us,
for the first time, to constrain the three-dimensional orientation of
Sgr's disrupting core and globular cluster system and compare that
orientation to the predictions of an N-body model of tidal disruption.
The density and distance of Sgr debris are consistent with models that
favor a relatively high Sgr core mass and a slightly greater distance
(28-30 kpc, with a mean of 29.4 kpc). Our analysis also suggests that
M54 is in the foreground of Sgr by ~2 kpc, projected on the center of
the Sgr dSph. While this would imply a remarkable alignment of the
cluster and the Sgr nucleus along the line of sight, we cannot identify
any systematic effect in our analysis that would falsely create the
measured 2 kpc separation. Finally, we find that the cluster Terzan 7
has the most discrepant distance (25 kpc) among the four Sgr core
clusters, which may suggest a different dynamical history than the other
Sgr core clusters.
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