DARK AND LUMINOUS MATTER IN THINGS DWARF GALAXIES
- Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, AL10 9AB (United Kingdom)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany)
- Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
We present mass models for the dark matter component of seven dwarf galaxies taken from 'The H I Nearby Galaxy Survey' (THINGS) and compare these with those taken from numerical {Lambda} cold dark matter ({Lambda}CDM) simulations. The THINGS high-resolution data significantly reduce observational uncertainties and thus allow us to derive accurate dark matter distributions in these systems. We here use the bulk velocity fields when deriving the rotation curves of the galaxies. Compared to other types of velocity fields, the bulk velocity field minimizes the effect of small-scale random motions more effectively and traces the underlying kinematics of a galaxy more properly. The 'Spitzer Infrared Nearby Galaxies Survey' 3.6 {mu}m and ancillary optical data are used for separating the baryons from their total matter content in the galaxies. The sample dwarf galaxies are found to be dark matter dominated over most radii. The relation between total baryonic (stars + gas) mass and maximum rotation velocity of the galaxies is roughly consistent with the baryonic Tully-Fisher relation calibrated from a larger sample of gas-dominated low-mass galaxies. We find discrepancies between the derived dark matter distributions of the galaxies and those of {Lambda}CDM simulations, even after corrections for non-circular motions have been applied. The observed solid body-like rotation curves of the galaxies rise too slowly to reflect the cusp-like dark matter distribution in cold dark matter halos. Instead, they are better described by core-like models such as pseudo-isothermal halo models dominated by a central constant-density core. The mean value of the logarithmic inner slopes of the mass density profiles is {alpha} = -0.29 {+-} 0.07. They are significantly different from the steep slope of {approx} - 1.0 inferred from previous dark-matter-only simulations, and are more consistent with shallower slopes found in recent {Lambda}CDM simulations of dwarf galaxies in which the effects of baryonic feedback processes are included.
- OSTI ID:
- 21583099
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 6 Vol. 141; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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