Bibcode
DOI
Gallart, Carme; Stetson, Peter B.; Hardy, Eduardo; Pont, Frederic; Zinn, Robert
Referencia bibliográfica
The Astrophysical Journal, Volume 614, Issue 2, pp. L109-L112.
Fecha de publicación:
10
2004
Revista
Número de citas
44
Número de citas referidas
33
Descripción
We present a high-quality color-magnitude diagram (CMD) for a
36'×36' field located 8° (~=7 kpc) from
the Large Magellanic Cloud (LMC) center, as well as a precise
determination of the LMC surface brightness derived from the resolved
stellar population out to this large galactocentric radius. This deep
CMD shows for the first time the detailed age distribution at this
position, where the surface brightness is V~=26.5 mag
arcsec-2. At a radius R~=474' the main sequence is
well populated from the oldest turnoff at I~=21.5 to the 2.5 Gyr turnoff
at I~=19.5. Beyond this radius, a relatively strong gradient in the
density of stars with ages in the ~=2.5-4 Gyr range is apparent. There
are some stars brighter and bluer than the main population, quite
uniformly distributed over the whole area surveyed, which are well
matched by a 1.5 Gyr isochrone and may be indicative of a relatively
recent star formation, or merger, event. The surface brightness profile
of the LMC remains exponential to this large galactocentric radius and
shows no evidence of disk truncation. Combining the information on
surface brightness and stellar population, we conclude that the LMC disk
extends (and dominates over a possible stellar halo) out to a distance
of at least 7 kpc. These results confirm that the absence of blue stars
in the relatively shallow off-center CMDs of dwarf irregular galaxies is
not necessarily evidence for an exclusively old stellar population
resembling the halo of the Milky Way.