Bibcode
Stephens, A. W.; Frogel, J. A.; Davies, R.; Freedman, W.; Gallart, C.; Jablonka, P.; Ortolani, S.; Renzini, A.; Rich, R. M.
Referencia bibliográfica
American Astronomical Society, 195th AAS Meeting, #03.09; Bulletin of the American Astronomical Society, Vol. 31, p.1370
Fecha de publicación:
12
1999
Número de citas
0
Número de citas referidas
0
Descripción
We have obtained JHK images of 5 bulge fields and 5 metal-rich globular
clusters in M31 with the NICMOS camera NIC2 on the Hubble Space
Telescope. The globulars we have observed are G1, G170, G174, G177 &
G280. We calibrate our data using the NICMOS transformations determined
by Stephens et al. (1999). For each cluster and field we have created a
color-magnitude diagram for the upper 6-8 magnitudes of the giant
branch, and determined their bolometric luminosity function. Higher
spatial resolution and deeper J band observations taken in parallel with
NIC1 are used to evaluate the effects of crowding on our primary
observations. From these observations we estimate the metallicity for
each cluster and field. We also compare the giant branches of the M31
globulars and bulge field with those of ground-based observations of the
giant branches of globular clusters and fields in the Galactic bulge.
Our data resolve the long standing controversy regarding the presence of
luminous giants -- and by implication an intermediate age population in
M31's bulge. These data will help further our understanding of the
evolution of metal rich stars, and improve population synthesis models
meant to study the stellar content of distant, unresolvable bulges and
elliptical galaxies. Support for this work was provided by NASA through
grant number GO-7826 and GO-7876 from the Space Telescope Science
Institute.