Bulge and Halo Kinematics Across the Hubble Sequence - AstrophysicsReport as inadecuate

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Abstract: The correlation between the maximum rotational velocity of the disk v m andthe central stellar velocity dispersion of the bulge sigma offers insightsinto the relationship between the halo and the bulge. We have assembledintegrated H I line widths and central stellar velocity dispersions to studythe v m-sigma relation for 792 galaxies spanning a broad range of Hubble types.Contrary to earlier studies based on much smaller samples, we find that thev m-sigma relation exhibits significant intrinsic scatter and that itszeropoint varies systematically with galaxy morphology, bulge-to-disk ratio,and light concentration, as expected from basic dynamical considerations.Nucleated but bulgeless late-type spiral galaxies depart significantly from thev m-sigma relation. While these results render questionable any attempt tosupplant the bulge with the halo as the fundamental determinant of the centralblack hole mass in galaxies, the observed distribution of v m-sigma, whichdepends on both the density profile and kinematic structure of the galaxy,offers a useful constraint on galaxy formation models. With the aid of anear-infrared Tully-Fisher relation, we identify a population of otherwisenormal, luminous galaxies that have exceptionally low values of v m-sigma. Weargue that a significant fraction of the H I gas in these kinematicallyanomalous objects is dynamically unrelaxed, having been acquired externallyeither through capture from tidal interactions or through cold accretion fromthe intergalactic medium.

Author: Luis C. Ho The Observatories of the Carnegie Institution of Washington

Source: https://arxiv.org/

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