2003/01/12 by Ayesha Begum, Jayaram N. Chengalur, U. Hopp +1 · 2 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.1016/s1384-1076(02)00238-5
published as New Astron. 8 (2003) 267-281 · Accepted for publication in New Astronomy. For copyright reasons this version is slightly different from the accepted version, although the differences are minor
arxiv created 2003/01/12 · openalex publication_date 2003/03/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present deep, high velocity resolution (1.6 km/s) GMRT HI as well as optical data for the faint (MB ~ -10.9) galaxy Camelopardalis B. We find that the HI in the galaxy has a regular velocity field, consistent with rotational motion. The implied kinematical major axis is well aligned with the major axis of both the HI and optical images. Cam B is the faintest known galaxy with such relatively well behaved kinematics. From the HI velocity field we derive a rotation curve for the galaxy. The peak (inclination corrected) rotation velocity is only 7km/s, comparable to the observed velocity dispersion. After correcting the observed rotation velocities for random motions (the "asymmetric drift" correction) we find a corrected peak rotation velocity of ~ 20 km/s. On fitting mass models to corrected rotation curve we find that the kinematics of Cam B is well fit with a modified isothermal halo with central density ρ0 approximately 12.0 M_\odot pc -3. This derived central density has only a very weak dependence on the assumed M/L ratio of the stellar disk. We also find that the corrected rotation curve cannot be fit with an NFW halo regardless of the assumed M/L ratio. We compile from the literature a sample of galaxies with rotation curves obtained from HI synthesis observations. From this sample (which has an absolute magnitude range of ~ 12) we find (i) that Cam B lies on the Tully-Fisher relation defined by these galaxies, provided we use the corrected rotation velocity, and (ii) a weak trend for increasing halo central density with decreasing galaxy size. Such a trend is expected in hierarchical models of halo formation.