Universität zu Köln

Lippok, N., Launhardt, R., Henning, Th., Balog, Z., Beuther, H., Kainulainen, J., Krause, O., Linz, H., Nielbock, M., Ragan, S. E., Robitaille, T. P., Sadavoy, S. I. and Schmiedeke, A. (2016). Earliest phases of star formation (EPoS) Dust temperature distributions in isolated starless cores. Astron. Astrophys., 592. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. Stars form by the gravitational collapse of cold and dense molecular cloud cores. Constraining the temperature and density structure of such cores is fundamental for understanding the initial conditions of star formation. We use Herschel observations of the thermal far-infrared (FIR) dust emission from nearby and isolated molecular cloud cores and combine them with ground-based submillimeter continuum data to derive observational constraints on their temperature and density structure. Aims. The aim of this study is to verify the validity of a ray-tracing inversion technique developed to derive the dust temperature and density structure of nearby and isolated starless cores directly from the dust emission maps and to test if the resulting temperature and density profiles are consistent with physical models. Methods. We have developed a ray-tracing inversion technique that can be used to derive the temperature and density structure of starless cores directly from the observed dust emission maps without the need to make assumptions about the physical conditions. Using this ray-tracing inversion technique, we derive the dust temperature and density structure of six isolated starless molecular cloud cores from dust emission maps in the wavelengths range 100 mu m-1.2 mm. We then employ self-consistent radiative transfer modeling to the density profiles derived with the ray-tracing inversion method. In this model, the interstellar radiation field (ISRF) is the only heating source. The local strength of the ISRF as well as the total extinction provided by the outer envelope are treated as semi-free parameters which we scale within defined limits. The best-fit values of both parameters are derived by comparing the self-consistently calculated temperature profiles with those derived by the ray-tracing method. Results. We confirm earlier results and show that all starless cores are significantly colder inside than outside, with central core temperatures in the range 7.5 - 11.9 K and envelope temperatures that are 2.4 - 9.6 K higher. The core temperatures show a strong negative correlation with peak column density which suggests that the thermal structure of the cores is dominated by external heating from the ISRF and shielding by dusty envelopes. We find that temperature profiles derived with the ray-tracing inversion method can be well-reproduced with self-consistent radiative transfer models if the cores have geometry that is not too complex and good data coverage with spatially resolved maps at five or more wavelengths in range between 100 mu m and 1.2 mm. We also confirm results from earlier studies that found that the usually adopted canonical value of the total strength of the ISRF in the solar neighbourhood is incompatible with the most widely used dust opacity models for dense cores. However, with the data available for this study, we cannot uniquely resolve the degeneracy between dust opacity law and strength of the ISRF.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Lippok, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Launhardt, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Henning, Th. UNSPECIFIED UNSPECIFIED UNSPECIFIED Balog, Z. UNSPECIFIED UNSPECIFIED UNSPECIFIED Beuther, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kainulainen, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Krause, O. UNSPECIFIED UNSPECIFIED UNSPECIFIED Linz, H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Nielbock, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ragan, S. E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Robitaille, T. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sadavoy, S. I. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schmiedeke, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-267292
DOI:	10.1051/0004-6361/201525792
Journal or Publication Title:	Astron. Astrophys.
Volume:	592
Date:	2016
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 PRE-STELLAR CORES; MOLECULAR CLOUD CORES; PRESTELLAR CORES; BOK GLOBULES; INITIAL CONDITIONS; PROTOSTELLAR CORES; RADIATIVE-TRANSFER; THERMAL STRUCTURE; SIZE DISTRIBUTION; PIPE NEBULA Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/26729