Bibcode
DOI
Vivas, A. Katherina; Zinn, Robert; Gallart, Carme
Bibliographical reference
The Astronomical Journal, Volume 129, Issue 1, pp. 189-200.
Advertised on:
1
2005
Citations
62
Refereed citations
56
Description
Sixteen RR Lyrae variables from the QUEST survey that lie in the leading
arm of the tidal stream from the Sagittarius dSph galaxy have been
observed spectroscopically to measure their radial velocities and metal
abundances. The systemic velocities of 14 stars, which were determined
by fitting a standard velocity curve to the individual measurements,
have a sharply peaked distribution with a mean of 33 km s-1
and a standard deviation of only 25 km s-1. The [Fe/H]
distribution of these stars has a mean of -1.76 and a standard deviation
of 0.22. These measurements are in good agreement with previous ones
from smaller samples of stars. The mean metallicity is consistent with
the age-metallicity relation that is observed in the main body of the
Sgr dSph galaxy. The radial velocities and the distances from the Sun of
these stars are compared with recent numerical simulations of the Sgr
streams that assume different shapes for the dark matter halo. Models
that assume a oblate halo do not fit the data as well as ones that
assume a spherical or a prolate distribution. However, none of the fits
are completely satisfactory. Every model fails to reproduce the long
extent of the stream in right ascension (36°) that is seen in the
region covered by the QUEST survey. Further modeling is required to see
if this and the other mismatches between theory and observation can be
removed by judicial choices for the model parameters or instead rule out
a class of models.