Query : 2008A&A...491L..45D

2008A&A...491L..45D - Astronomy and Astrophysics, volume 491, L45-48 (2008/12-1)

An enigmatic HI cloud.


Abstract (from CDS):

The discovery of an HI cloud with peculiar properties at equatorial coordinates (J2000) α=07h49m, δ=04d30' is presented. The HI object was detected at 21cm using the 300-m NAIC Arecibo telescope. Subsequent follow-up high-resolution observations with the NRAO Very Large Array (VLA) telescope at L-Band revealed more details about its morphology. The most intriguing aspect of the object is the clear velocity gradient of 1km/s, which is present in the data, an indication of either rotation or expansion. The gas appears to be cold, and its morphology is somewhat elliptical with clumpy substructure. Assuming disk rotation, the dynamical mass could be determined as a function of distance. Depending on the exact nature of the velocity gradient in the HI cloud, we can reach some preliminary conclusions about the nature of the object. Expansion would imply association with a circumstellar envelope of an evolved AGB star, while in the case of rotation, a comparison between the visible and the dynamical mass can lead to some preliminary conclusions. A common feature of those conclusions is the presence of a gravitational potential well, which is required to account for the rotation of the trapped HI gas. This potential well could be associated with a dark galaxy or some other exotic object.

Abstract Copyright:

Journal keyword(s): ISM: structure - Galaxy: halo - radio lines: general

Nomenclature: Text: [DDK2008] JHHMMSS.sss+DDMMSS N=1.

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6632 1
2 [DDK2008] J074949.613+043030 HI 07 49 49.613 +04 30 30.00           ~ 3 0
3 TYC 188-839-1 * 07 49 53.4903673104 +04 30 23.928534864   11.73 11.62   10.94 ~ 2 0
4 NAME Galactic Bulge reg ~ ~           ~ 4052 0

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