Query : 2002A&A...393L..41H

2002A&A...393L..41H - Astronomy and Astrophysics, volume 393, L41-44 (2002/10-2)

Small-area molecular structures without shielding.


Abstract (from CDS):

Using the IRAM 30m telescope two molecular structures have been detected which cover very small areas, FWHM≤1'. The clouds have velocities of vlsr≃5km/s and linewidth of Δv≃0.8km/s; thus they belong most likely to the Milky Way. Applying standard conversion factors one finds that even at the upper distance limit of 2200pc the structures are low mass objects (M=(1-6)x10–4(d/100pc)2M) which are not gravitationally virialized. HI 21 cm line data towards the clouds show no prominent HI clouds. The total HI column densities for both structures are below N(HI)≤2.1x1020cm–2, corresponding to AV≤0.2mag, assuming a standard gas-to-dust ratio. IRAS 100µm data towards the structures show also only low emission, consistent with low extinction. Unless there is unseen cold dust associated with the structures this shielding is too low for the structures to survive the interstellar radiation field for a long time. The detection of 2 such structures in a rather limited sample of observations suggests that they could be a rather common feature in the interstellar medium, however, so far not recognized as such due to the weakness of their lines and their small extent.

Abstract Copyright:

Journal keyword(s): interstellar medium (ISM): abundances - ISM: clouds - ISM: molecules - dark matter candidates

Nomenclature: Table 1: SAMS Na (Nos 1-2, 2a-2b).

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 NAME M 81-82 Group GrG 09 55 +69.1           ~ 717 0
2 SAMS 2b MoC 09 56 56.5 +69 20 02           ~ 1 0
3 SAMS 2 MoC 09 57.0 +69 20           ~ 2 0
4 SAMS 2a MoC 09 57 00.3 +69 19 22           ~ 1 0
5 SAMS 1 MoC 10 03 30.3 +68 41 42           ~ 2 0

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