Kinematics of the faintest gas rich galaxy in the local group: DDO210

Begum, A. ; Chengalur, J. N. (2004) Kinematics of the faintest gas rich galaxy in the local group: DDO210 Astronomy & Astrophysics, 413 (2). pp. 525-534. ISSN 0004-6361

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We present deep, high velocity resolution (~ 1.6 km s −1) Giant Meterwave Radio Telescope (GMRT) HI 21 cm synthesis images of the faint ( MB ~ −10.6) local group dwarf galaxy DDO210. We find that the HI distribution in the galaxy is not axi-symmetric, but shows density enhancements in the eastern and southern halves of the galaxy. The optical emission is lopsided with respect to the HI, most of the bright optical emission arises from the eastern half of the HI disk. The velocity field of the galaxy is however quite regular and shows a systematic large scale pattern, consistent with the rotational motion. The rotation curve for the galaxy shows a peak (inclination corrected) rotation velocity of only ~8 km s−1, comparable to the random motions in the HI gas. After correcting for the dynamical support provided by random motions (the "asymmetric drift" correction), we find the corrected peak rotation velocity of ~ 16.0 km s −1. Mass modeling of the corrected rotation curve shows that the kinematics of DDO210 can be well fit with either a modified isothermal halo (with a central density ρ0 ~ 29 × 10−3 M pc−3 for a stellar mass to light ratio of 3.4) or an NFW halo. In the case of the NFW halo however, a good fit is obtained for a wide range of parameters; the halo parameters could not be uniquely determined from the fit. Density profiles with inner slope steeper than ~ 1.2 however provide a poor fit to the data. Finally, the rotation curve derived using MOND also provides a reasonable fit to the observed rotation curve.

Item Type:Article
Source:Copyright of this article belongs to EDP Sciences.
Keywords:Galaxies: Evolution; Galaxies: Dwarf; Galaxies: Kinematics and Dynamics; Galaxies: Individual: DDO210; Radio Lines: Galaxies
ID Code:63528
Deposited On:29 Sep 2011 04:06
Last Modified:29 Sep 2011 04:06

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