HST/NICMOS Imaging of Red Giants in NGC3379

NGC3379 (M105) is the nearest normal giant elliptical galaxy and so is our best hope for determining the stellar populations of such galaxies. Using NICMOS, we have obtained deep J and H band observations of 3 fields in the halo of NGC3379; the H-band for the inner field is shown here. This image reaches about 1 magnitude below the tip of the red giant branch with S/N of 5. There are roughly 750 stars in this 19"x19" field. The goal is to derive the mean metallicity of the red giants for use in calibrating spectral synthesis using the integrated light of elliptical galaxies.

We divided the observations into 2 epochs to look for variables. Much to our surprise, there appear to be quite a few; at least 2 are evident in the inserts which show a small portion of the field at each epoch.

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UCD Physics Dept.
Cosmology Research Group
Institute of Geophysics and Planetary Physics at the Lawrence Livermore National Laboratory

Modified February, 2003
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