Universität zu Köln

Mueller, Holger S. P., Muller, Sebastien, Schilke, Peter ORCID: 0000-0003-2141-5689, Bergin, Edwin A., Black, John H., Gerin, Maryvonne, Lis, Dariusz C., Neufeld, David A. and Suri, Suemeyye (2015). Detection of extragalactic argonium, ArH+, toward PKS 1830-211. Astron. Astrophys., 582. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 1432-0746

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Abstract

Context. Argonium has recently been detected as a ubiquitous molecule in our Galaxy. Model calculations indicate that its abundance peaks at molecular fractions in the range of 10(-4) to 10(-3) and that the observed column densities require high values of the cosmic ray ionization rate. Therefore, this molecular cation may serve as an excellent tracer of the very diffuse interstellar medium (ISM), as well as an indicator of the cosmic ray ionization rate. Aims. We attempted to detect ArH+ in extragalactic sources to evaluate its diagnostic power as a tracer of the almost purely atomic ISM in distant galaxies. Methods. We obtained ALMA observations of a foreground galaxy at z = 0.89 in the direction of the lensed blazar PKS 1830-211. Results. Two isotopologs of argonium, (ArH+)-Ar-36 and (ArH+)-Ar-38, were detected in absorption along two different lines of sight toward PKS 1830-211, known as the SW and NE images of the background blazar. The argonium absorption is clearly enhanced on the more diffuse line of sight (NE) compared to other molecular species. The isotopic ratio Ar-36/Ar-38 is 3.46 +/- 0.16 toward the SW image, i.e., significantly lower than the solar value of 5.5. Conclusions. Our results demonstrate the suitability of argonium as a tracer of the almost purely atomic, diffuse ISM in high-redshift sources. The evolution of the isotopic ratio with redshift may help to constrain nucleosynthetic scenarios in the early Universe.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Mueller, Holger S. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Muller, Sebastien UNSPECIFIED UNSPECIFIED UNSPECIFIED Schilke, Peter UNSPECIFIED orcid.org/0000-0003-2141-5689 UNSPECIFIED Bergin, Edwin A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Black, John H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gerin, Maryvonne UNSPECIFIED UNSPECIFIED UNSPECIFIED Lis, Dariusz C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Neufeld, David A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Suri, Suemeyye UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-390384
DOI:	10.1051/0004-6361/201527254
Journal or Publication Title:	Astron. Astrophys.
Volume:	582
Date:	2015
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	1432-0746
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOLECULAR ABSORPTION; HERSCHEL/HIFI DISCOVERY; ROTATIONAL SPECTRUM; COLOGNE DATABASE; H2O+; Z=0.89; SPECTROSCOPY; H3O+; OH+; SUBMILLIMETER Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/39038