3 research outputs found
Dust and the Infrared Kinematic Properties of Early-Type Galaxies
We have obtained spectra and measured the stellar kinematics in a sample of
25 nearby early-type galaxies (with velocity dispersions from less than 100
km/s to over 300 km/s) using the near-infrared CO absorption bandhead at 2.29
microns. Our median uncertainty for the dispersions is ~10%. We examine the
effects of dust on existing optical kinematic measurements. We find that the
near-infrared velocity dispersions are in general smaller than optical velocity
dispersions, with differences as large as 30%. The median difference is 11%
smaller, and the effect is of greater magnitude for higher dispersion galaxies.
The lenticular galaxies (18 out of 25) appear to be causing the shift to lower
dispersions while the classical ellipticals (7 out of 25) are consistent
between the two wavelength regimes. If uniformly distributed dust causes these
differences, we would expect to find a correlation between the relative amount
of dust in a galaxy and the fractional change in dispersion, but we do not find
such a correlation. We do see correlations both between velocity dispersion and
CO bandhead equivalent width, and velocity dispersion and Mg2 index. The
differences in dispersion are not well explained by current models of dust
absorption. The lack of correlation between the relative amount of dust and
shift in dispersion possibly suggets that dust does not have a similar
distribution from galaxy to galaxy. The CO equivalent widths of these galaxies
are quite high (>10 angstroms for almost all), requiring the light at these
wavelengths to be dominated by very cool stars.Comment: 17 pages, 14 figures, accepted to The Astronomical Journa