Issue |
A&A
Volume 391, Number 1, August III 2002
|
|
---|---|---|
Page(s) | 159 - 178 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20020870 | |
Published online | 29 July 2002 |
An automated search for compact high–velocity clouds in the Leiden/Dwingeloo Survey*
1
Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
2
Netherlands Foundation for Research in Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
3
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903, USA
Corresponding author: R. Braun, rbraun@astron.nl
Received:
20
June
2001
Accepted:
31
May
2002
We describe an automated search through the Leiden/Dwingeloo
H i Survey (LDS) for high–velocity clouds north of
. From the general catalog we extract a sample of
relatively small (less than about
) and isolated
high–velocity clouds, CHVCs: anomalous–velocity H i clouds which are
sharply bounded in angular extent with no kinematic or spatial
connection to other H i features down to a limiting column density of
cm-2. This column density is an order of
magnitude lower than the critical H i column density,
~
cm-2, (e.g. Maloney [CITE])
where the ionized fraction is thought to increase dramatically due to
the extragalactic radiation field. As such, these objects are likely to
provide their own shielding to ionizing radiation. Their small angular
size, of less than about
FWHM, might then imply substantial
distances, since the partially ionized H i skin in a power–law
ionizing photon field has a typical exponential scale–length of 1 kpc
(e.g. Corbelli & Salpeter [CITE]). The automated search
algorithm has been applied to the HIPASS and to the Leiden/Dwingeloo
data sets. The results from the LDS are described here; Putman et
al. ([CITE]) describe application of this algorithm to the
HIPASS material. We identify 67 CHVCs in the LDS which satisfy
stringent requirements on isolation, and an additional 49 objects which
satisfy somewhat less stringent requirements. Independent confirmation
is available for all of these objects, either from earlier data in the
literature or from new observations made with the Westerbork Synthesis
Radio Telescope and reported here. The catalog includes 54 of the 65
CHVCs listed by Braun & Burton ([CITE]) on the basis of a
visual search of the LDS data.
SM: clouds – ISM: kinematics and dynamics – Galaxy: evolution – galaxies: dwarf
– galaxies: evolution – galaxies: Local Group
© ESO, 2002
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.