Issue |
A&A
Volume 446, Number 2, February I 2006
|
|
---|---|---|
Page(s) | L1 - L4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:200500223 | |
Published online | 13 January 2006 |
Letter to the Editor
The age of the main population of the Sagittarius dwarf spheroidal galaxy
Solving the “M giant conundrum”
1
INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, 20127 Bologna, Italy e-mail: [michele.bellazzini;paolo.montegriffo]@bo.astro.it
2
Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, 20127 Bologna, Italy e-mail: [francesco.ferraro3;matteo.correnti]@studio.unibo.it
3
ESO – European Southern Observatory, Alonso de Cordova 3107, Santiago 19, Chile e-mail: lmonaco@eso.org
Received:
15
September
2005
Accepted:
3
December
2005
We present a statistically decontaminated Color
Magnitude Diagram of a field in the core
of the Sagittarius dSph galaxy. Coupling this CMD with
the most recent metallicity distributions obtained from high resolution
spectroscopy we derive robust constraints on the mean age of the stellar
population that dominates the galaxy (Pop A). Using
three different sets of theoretical isochrones in the metallicity range
and taking into consideration distance moduli
in the range
we find that the mean age of Pop A
is larger than 5 Gyr, and the best-fit value is age =
Gyr. Since Pop A provides the vast majority of the M giants that traces
the tidal stream of Sgr dSph all over the sky, our estimate resolves the so
called “M giant conundrum” (Majewski et al. 2003, ApJ, 599, 1082). The time needed by
the M giants that currently populates the stream to diffuse within the main
body of Sgr and to reach the extremes of the tidal tails once torn apart
from the parent galaxy (
Gyr) can be easily accommodated into
the time lapsed since their birth (
Gyr).
Key words: Galaxies: dwarf / Galaxies: evolution / stars: abundances
© ESO, 2006
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