Volume 426, Number 1, October IV 2004
|Page(s)||L9 - L13|
|Published online||05 October 2004|
Letter to the Editor
H I observations of an Ultra-Compact High-Velocity Cloud
Radioastronomisches Institut, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: firstname.lastname@example.org
Accepted: 6 September 2004
We present observations of the compact high-velocity cloud HVC289+33+251 that was discovered by Putman et al. ([CITE]). Observations with the 100-m Effelsberg telescope demonstrate that this cloud is still unresolved by the 9´ beam of the Effelsberg telescope. The cloud shows a small line width of km s-1 providing an upper limit to the kinetic temperature of the gas of K. The total observed flux indicates an mass of M() = . Follow-up observations using the Australia Telescope Compact Array (ATCA) resolve HVC289+33+251 into 5 condensations that are embedded in a common envelope. The HVC shows a faint tail, indicating an ongoing ram-pressure interaction with an ambient low-density medium. A FWHM diameter of ϑ = 44 makes this HVC the by far most compact HVC known till now. The observed parameters suggest that pressure stabilization by an ambient medium is rather unlikely. At a distance of 150 kpc, the virial mass is by a factor of 5.6 higher than the observed gas mass – consistent with HVC289+33+251 being one of the “missing” dark matter mini halos that were predicted by cosmological ΛCDM simulations (e.g. Klypin et al. [CITE]; Moore et al. [CITE]). Comparable clouds in other groups of galaxies or even around the Milky Way are not detectable with the resolution and sensitivity of present surveys.
Key words: Galaxy: halo / ISM: clouds / ISM: individual objects: high-velocity clouds / dark matter
© ESO, 2004
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.