Volume 457, Number 3, October III 2006
|Page(s)||917 - 926|
|Section||Interstellar and circumstellar matter|
|Published online||12 September 2006|
Physical properties of two compact high-velocity clouds possibly associated with the leading arm of the Magellanic system
Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: email@example.com
Accepted: 7 July 2006
Aims.We observed two compact high-velocity clouds HVC 291+26+195 and HVC 297+09+253 to analyse their structure, dynamics, and physical parameters. In both cases there is evidence for an association with the Leading Arm of the Magellanic Clouds. The goal of our study is to learn more about the origin of the two CHVCs and to use them as probes for the structure and evolution of the Leading Arm.
Methods.We have used the Parkes 64-m radio telescope and the Australia Telescope Compact Array (ATCA) to study the two CHVCs in the 21-cm line emission of neutral hydrogen. The observations with a single-dish and a synthesis telescope allow us to analyse both the diffuse, extended emission as well as the small-scale structure of the clouds. We present a method to estimate the distance of the two CHVCs.
Results.The investigation of the line profiles of HVC 297+09+253 reveals the presence of two line components in the spectra which can be identified with a cold and a warm gas phase. In addition, we find a distinct head-tail structure in combination with a radial velocity gradient along the tail, suggesting a ram-pressure interaction of this cloud with an ambient medium. HVC 291+26+195 has only a cold gas phase and no head-tail structure. The ATCA data show several cold, compact clumps in both clouds which, in the case of HVC 297+09+253, are embedded in the warm, diffuse envelope. All these clumps have very narrow lines with typical line widths between 2 and FWHM, yielding an upper limit for the kinetic temperature of the gas of . We obtain distance estimates for both CHVCs of the order of 10 to 60 kpc, providing additional evidence for an association of the clouds with the Leading Arm. Assuming a distance of 50 kpc, we get masses of and for HVC 291+26+195 and HVC 297+09+253, respectively.
Key words: Galaxy: halo / ISM: clouds / ISM: structure / ISM: kinematics and dynamics / galaxies: Magellanic Clouds
© ESO, 2006
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.