Bibcode
DOI
Chou, Mei-Yin; Majewski, Steven R.; Cunha, Katia; Smith, Verne V.; Patterson, Richard J.; Martínez-Delgado, David; Law, David R.; Crane, Jeffrey D.; Muñoz, Ricardo R.; Garcia López, Ramón; Geisler, Doug; Skrutskie, Michael F.
Bibliographical reference
The Astrophysical Journal, Volume 670, Issue 1, pp. 346-362.
Advertised on:
11
2007
Journal
Citations
141
Refereed citations
129
Description
We present reliable measurements of the metallicity distribution
function (MDF) at different points along the tidal stream of the
Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy, based on
high-resolution, echelle spectroscopy of candidate M giant members of
the Sgr system. The Sgr MDF is found to evolve significantly from a
median [Fe/H]~-0.4 in the core to ~-1.1 dex over a Sgr leading arm
length representing ~2.5-3.0 Gyr of dynamical (i.e., tidal stripping)
age. This is direct evidence that there can be significant chemical
differences between current dSph satellites and the bulk of the stars
they have contributed to the halo. Our results suggest that Sgr
experienced a significant change in binding energy over the past several
gigayears, which has substantially decreased its tidal boundary across a
radial range over which there must have been a significant metallicity
gradient in the progenitor galaxy. By accounting for MDF variation along
the debris arms, we approximate the MDF Sgr would have had several
gigayears ago. We also analyze the MDF of a moving group of M giants we
previously discovered toward the north Galactic cap. These objects have
the opposite radial velocities to the infalling Sgr leading arm stars
there, and we propose that most of them represent Sgr trailing arm stars
overlapping the Sgr leading arm in this part of the sky. If so, these
trailing arm stars further demonstrate the strong MDF evolution within
the Sgr stream.