A1 Refereed original research article in a scientific journal
Chemical and Physical Conditions in Molecular Cloud Core Dc 000.4-19.5 (Sl42) in Corona Australis
Authors: E Hardegree-Ullman, J Harju, M Juvela, O Sipila, D C B Whittet, S Hotzel
Publisher: IOP PUBLISHING LTD
Publishing place: BRISTOL; TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND
Publication year: 2013
Journal: Astrophysical Journal
Journal name in source: Astrophysical Journal
Journal acronym: Astrophys.J.
Number in series: 1
Volume: 763
Issue: 1
First page : 45
Last page: 45
Number of pages: 1
ISSN: 0004-637X
DOI: https://doi.org/10.1088/0004-637X/763/1/45
Abstract
Chemical reactions in starless molecular clouds are heavily dependent on interactions between gas phase material and solid phase dust and ices. We have observed the abundance and distribution of molecular gases in the cold, starless coreDC000.4-19.5 (SL42) in Corona Australis using data from the Swedish ESO Submillimeter Telescope. We present column density maps determined from measurements of (CO)-O-18 (J = 2-1, 1-0) and N2H+ (J = 1-0) emission features. Herschel data of the same region allow a direct comparison to the dust component of the cloud core and provide evidence for gas phase depletion of CO at the highest extinctions. The dust color temperature in the core calculated from Herschel maps ranges from roughly 10.7 to 14.0 K. This range agrees with the previous determinations from Infrared Space Observatory and Planck observations. The column density profile of the core can be fitted with a Plummer-like density distribution approaching n(r) similar to r(-2) at large distances. The core structure deviates clearly from a critical Bonnor-Ebert sphere. Instead, the core appears to be gravitationally bound and to lack thermal and turbulent support against the pressure of the surrounding low-density material: it may therefore be in the process of slow contraction. We test two chemical models and find that a steady-state depletion model agrees with the observed (CO)-O-18 column density profile and the observed N((CO)-O-18) versus AV relationship.
Chemical reactions in starless molecular clouds are heavily dependent on interactions between gas phase material and solid phase dust and ices. We have observed the abundance and distribution of molecular gases in the cold, starless coreDC000.4-19.5 (SL42) in Corona Australis using data from the Swedish ESO Submillimeter Telescope. We present column density maps determined from measurements of (CO)-O-18 (J = 2-1, 1-0) and N2H+ (J = 1-0) emission features. Herschel data of the same region allow a direct comparison to the dust component of the cloud core and provide evidence for gas phase depletion of CO at the highest extinctions. The dust color temperature in the core calculated from Herschel maps ranges from roughly 10.7 to 14.0 K. This range agrees with the previous determinations from Infrared Space Observatory and Planck observations. The column density profile of the core can be fitted with a Plummer-like density distribution approaching n(r) similar to r(-2) at large distances. The core structure deviates clearly from a critical Bonnor-Ebert sphere. Instead, the core appears to be gravitationally bound and to lack thermal and turbulent support against the pressure of the surrounding low-density material: it may therefore be in the process of slow contraction. We test two chemical models and find that a steady-state depletion model agrees with the observed (CO)-O-18 column density profile and the observed N((CO)-O-18) versus AV relationship.
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