Abstract
M giants play a significant role in determining the shape of the spectral energy
distribution of elliptical galaxies, producing the TiO bands seen at optical
wavelengths and contributing the majority of the flux in the infrared. However,
these stars have proven to be notoriously difficult to model. Previous
measurements of angular diameters by Ridgway et al. (1980), Dyck et al. (1996)
and di Benedetto & Rabbia (1987) have produced very similar relations between
spectral type and effective temperature for K and M giants. We present here
an alternative temperature scale for these stars which is based upon
recent angular diameter measurements of Mozurkewich. This new relation is in
reasonable agreement with the older ones for K giants but differs from them in
being sytematically cooler at a given spectral type for the M giants. In this
poster, we contrast models based upon this new effective temperature scale and
that of Dyck et al. (1996). We examine the effects on the synthetic spectra
which we use in our galaxy population synthesis program, concentrating upon the
TiO and CO molecular absorption features. We estimate the spectral types of our
synthetic spectra using three methods - the strengths of the TiO bands, the
equivalent width of the CO bandhead near 2.3 microns and the eight-color
photometric system of Wing - and check the agreement of the three.
Back to Mark Houdashelt's Home Page