Dynamical Centers and Noncircular Motions in THINGS Galaxies: Implications for Dark Matter Halos

We present harmonic decompositions of the velocity fields of 19 galaxies from The H I Nearby Galaxy Survey (THINGS) which quantify the magnitude of the noncircular motions in these galaxies and yield observational estimates of the elongations of the dark matter halo potentials. Additionally, we pres...

Full description

Saved in:
Bibliographic Details
Published inThe Astronomical journal Vol. 136; no. 6; pp. 2720 - 2760
Main Authors Trachternach, C, de Blok, W. J. G, Walter, F, Brinks, E, Kennicutt, R. C
Format Journal Article
LanguageEnglish
Published United States IOP Publishing 01.12.2008
Subjects
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
DWARF STARS
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
LUMINOSITY
MATTER
MOTION
NONLUMINOUS MATTER
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
ROTATION
SIMULATION
STARS
VELOCITY
Online AccessGet full text

Cover

More Information
Summary:We present harmonic decompositions of the velocity fields of 19 galaxies from The H I Nearby Galaxy Survey (THINGS) which quantify the magnitude of the noncircular motions in these galaxies and yield observational estimates of the elongations of the dark matter halo potentials. Additionally, we present accurate dynamical center positions for these galaxies. We show that the positions of the kinematic and photometric centers of the large majority of the galaxies in our sample are in good agreement. The median absolute amplitude of the noncircular motions, averaged over our sample, is 6.7 km s{sup -1}, with {approx}90% of the galaxies having median noncircular motions of less than {approx}9 km s{sup -1}. As a fraction of the total rotation velocity, this translates into 4.5% on average. The mean elongation of the gravitational potential, after a statistical correction for an unknown viewing angle, is 0.017 {+-} 0.020, which is consistent with a round potential. Our derived noncircular motions and elongations are smaller than what is needed to bring cold dark matter (CDM) simulations in agreement with the observations. In particular, the amplitudes of the noncircular motions are not high enough to hide the steep central mass-density profiles predicted by CDM simulations. We show that the amplitudes of the noncircular motions decrease toward lower luminosities and later Hubble types.
ISSN:1538-3881
0004-6256
1538-3881
DOI:10.1088/0004-6256/136/6/2720