Universität zu Köln

Sandell, G., Mookerjea, B., Guesten, R., Requena-Torres, M. A., Riquelme, D. and Okada, Y. (2015). High spectral and spatial resolution observations of the PDR emission in the NGC 2023 reflection nebula with SOFIA and APEX. Astron. Astrophys., 578. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

We have mapped the NGC 2023 reflection nebula in [CII] and CO(11-10) with the heterodyne receiver GREAT on SOFIA and obtained slightly smaller maps in (CO)-C-13(3-2), CO(3-2), CO(4-3), CO(6-5), and CO(7-6) with APEX in Chile. We use these data to probe the morphology, kinematics, and physical conditions of the C II region, which is ionized by FUV radiation from the B2 star HD37903. The [CII] emission traces an ellipsoidal shell-like region at a position angle of similar to-50 degrees, and is surrounded by a hot molecular shell. In the southeast, where the C II region expands into a dense, clumpy molecular cloud ridge, we see narrow and strong line emission from high-J CO lines, which comes from a thin, hot molecular shell surrounding the [C II] emission. The [CII] lines are broader and show photo evaporating gas flowing into the C II region. Based on the strength of the [(CII)-C-13] F = 2-1 line, the [CII] line appears to be somewhat optically thick over most of the nebula with an optical depth of a few. We model the physical conditions of the surrounding molecular cloud and the PDR emission using both RADEX and simple PDR models. The temperature of the CO emitting PDR shell is similar to 90-120 K, with densities of 10(5)-10(6) cm(-3), as deduced from RADEX modeling. Our PDR modeling indicates that the PDR layer where [C II] emission dominates has somewhat lower densities, 10(4) to a few times 10(5) cm(-3).

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Sandell, G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mookerjea, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED Guesten, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Requena-Torres, M. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Riquelme, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Okada, Y. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-402285
DOI:	10.1051/0004-6361/201525881
Journal or Publication Title:	Astron. Astrophys.
Volume:	578
Date:	2015
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOLECULAR-HYDROGEN EMISSION; CLUMPY PHOTODISSOCIATION REGIONS; STAR-FORMING REGIONS; MU-M EMISSION; C-II; VIBRATIONAL FLUORESCENCE; PHYSICAL CONDITIONS; H-2; NGC-2023; HERSCHEL Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/40228