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Gaches, Brandt A. L., Offner, Stella S. R. and Bisbas, Thomas G. (2019). The Astrochemical Impact of Cosmic Rays in Protoclusters. II. CI-to-H-2 and CO-to-H-2 Conversion Factors. Astrophys. J., 883 (2). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

We utilize a modified astrochemistry code that includes cosmic-ray (CR) attenuation in situ to quantify the impact of different CR models on the CO-to-H-2 and CI-to-H-2 conversion factors, Xco and XcI, respectively. We consider the impact of CRs accelerated by accretion shocks, and show that clouds with star formation efficiencies greater than 2% have X-CO = (2.5 1) x 10(20) cm(-2)(K km s(-1)) 1, consistent with Milky Way observations. We find that changing the CR ionization rate from external sources from the canonical zeta approximate to 10(-17) to zeta approximate to 10(-16) s(-1), which better represents observations in diffuse gas, reduces X-CO by 0.2 dex for clusters with surface densities below 3 g cm z. We show that embedded sources regulate X-CO and decrease its variance across a wide range of surface densities and star formation efficiencies. Our models reproduce the trends of a decreased X-CO in extreme CR environments. X-CI has been proposed as an alternative to Xco due to its brightness at high redshifts. The inclusion of internal CR sources leads to 1.2 dex dispersion in XcI ranging from 2 x 102 1 1 < XcI < 4 x 1021 cm (K km s). We show that X-CI is highly sensitive to the underlying CR model.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Gaches, Brandt A. L. UNSPECIFIED UNSPECIFIED UNSPECIFIED Offner, Stella S. R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bisbas, Thomas G. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-131822
DOI:	10.3847/1538-4357/ab3c5c
Journal or Publication Title:	Astrophys. J.
Volume:	883
Number:	2
Date:	2019
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	1538-4357
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language C-I EMISSION; MOLECULAR GAS; INTERSTELLAR-MEDIUM; STAR-FORMATION; MILKY-WAY; X-FACTOR; TRACER; GALAXIES; LINES Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/13182