NDLI: An all–sky study of compact, isolated high

Content Provider	EDP Sciences
Author	V. de Heij R. Braun W. B. Burton
Abstract	We combine the catalog of compact high–velocity H i clouds extracted by de Heij et al. ([CITE]) from the Leiden/Dwingeloo Survey in the northern hemisphere with the catalog extracted by Putman et al. ([CITE]) from the Parkes HIPASS data in the southern hemisphere, and analyze the all–sky properties of the ensemble. Compact high–velocity clouds are a subclass of the general high–velocity cloud phenomenon which are isolated in position and velocity from the extended high–velocity Complexes and Streams down to column densities below cm^{-2^{. Objects satisfying these criteria for isolation are found to have a median angular size of less than one degree. We discuss selection effects relevant to the two surveys; in particular the crucial role played by obscuration due to Galactic H i. Five principal observables are defined for the CHVC population: (1) the spatial deployment of the objects on the sky, (2) the kinematic distribution, (3) the number distribution of observed H i column densities, (4) the number distribution of angular sizes, and (5) the number distribution of H i linewidth. Two classes of models are considered to reproduce the observed properties. The agreement of models with the data is judged by extracting these same observables from simulations, in a manner consistent with the sensitivities of the observations and explicitly taking account of Galactic obscuration. We show that models in which the CHVCs are the H i counterparts of dark–matter halos evolving in the Local Group potential provide a good match to the observables. The best–fitting populations have a maximum HI mass of , a power-law slope of the HI mass distribution in the range -1.7 to -1.8, and a Gaussian dispersion for their spatial distributions of between 150 and 200 kpc centered on both the Milky Way and M 31. Given its greater mean distance, only a small fraction of the M 31 sub–population is predicted to have been detected in present surveys. An empirical model for an extended Galactic halo distribution for the CHVCs is also considered. While reproducing some aspects of the population, this class of models does not account for some key systematic features of the population.}}
Ending Page	451
Starting Page	417
Page Count	35
File Format	HTM / HTML PDF
ISSN	00046361
Alternate Webpage(s)	https://www.aanda.org/articles/aa/abs/2002/35/aa2407/aa2407.html
e-ISSN	14320746
Issue Number	2
Journal	Astronomy & Astrophysics
Volume Number	392
DOI	10.1051/0004-6361:20020908
Language	English
Publisher	EDP Sciences
Publisher Date	2002-09-01
Access Restriction	Open
Rights Holder	© ESO, 2002
Subject Keyword	ISM: atoms ISM: clouds Galaxy: evolution Galaxy: formation galaxies: dwarf galaxies: Local Group ISM: atoms / ISM: clouds / Galaxy: evolution / Galaxy: formation / galaxies: dwarf / galaxies: Local Group
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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