An ALMA Early Science survey of molecular absorption lines toward PKS 1830−211^⋆,⋆⋆

Analysis of the absorption profiles

¹ Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
e-mail: mullers@chalmers.se
² Observatoire de Paris, LERMA, CNRS, 61 Av. de l’Observatoire, 75014 Paris, France
³ Institut de Radioastronomie Millimétrique, 300, rue de la piscine, 38406 St Martin d’Hères, France
⁴ LRA/LERMA, CNRS UMR 8112, Observatoire de Paris & École Normale Supérieure, 75231 Paris, France
⁵ Institut d’Astrophysique Spatiale, Bât. 121, Université Paris-Sud, 91405 Orsay Cedex, France
⁶ Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
⁷ ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)  
⁸ Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309-0389, USA
⁹ Institute of Physics, Vietnam Academy of Science and Technology, 10 DaoTan, ThuLe, BaDinh, Hanoi, Vietnam
¹⁰ Observatorio Astronómico Nacional, Alfonso XII, 3, 28014 Madrid, Spain
¹¹ Max-Planck-Institut für Radioastonomie, Auf dem Hügel 69, 53121 Bonn, Germany
¹² Astron. Dept., King Abdulaziz University, PO Box 80203, Jeddah, Saudi Arabia
¹³ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
¹⁴ National Radio Astronomy Observatory, PO Box O, 1003 Lopezville Road, Socorro, NM 87801, USA
¹⁵ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
¹⁶ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany

Received: 14 February 2014
Accepted: 9 April 2014

Abstract

We present the first results of an ALMA spectral survey of strong absorption lines for common interstellar species in the z = 0.89 molecular absorber toward the lensed blazar PKS 1830−211. The dataset brings essential information on the structure and composition of the absorbing gas in the foreground galaxy. In particular, we find absorption over large velocity intervals (≳100 km s^-1) toward both lensed images of the blazar. This suggests either that the galaxy inclination is intermediate and that we sample velocity gradients or streaming motions in the disk plane, that the molecular gas has a large vertical distribution or extraplanar components, or that the absorber is not a simple spiral galaxy but might be a merger system. The number of detected species is now reaching a total of 42 different species plus 14 different rare isotopologues toward the SW image, and 14 species toward the NE line-of-sight. The abundances of CH, H₂O, HCO⁺, HCN, and NH₃ relative to H₂ are found to be comparable to those in the Galactic diffuse medium. Of all the lines detected so far toward PKS 1830−211, the ground-state line of ortho-water has the deepest absorption. We argue that ground-state lines of water have the best potential for detecting diffuse molecular gas in absorption at high redshift.