Herschel Measurements of Molecular Oxygen in Orion
Artikel i vetenskaplig tidskrift, 2011

We report observations of three rotational transitions of molecular oxygen (O2) in emission from the H2 Peak 1 position of vibrationally excited molecular hydrogen in Orion. We observed the 487 GHz, 774 GHz, and 1121 GHz lines using the Heterodyne Instrument for the Far Infrared on the Herschel Space Observatory, having velocities of 11 km s–1 to 12 km s–1 and widths of 3 km s–1. The beam-averaged column density is N(O2) = 6.5 × 1016 cm–2, and assuming that the source has an equal beam-filling factor for all transitions (beam widths 44, 28, and 19''), the relative line intensities imply a kinetic temperature between 65 K and 120 K. The fractional abundance of O2 relative to H2 is (0.3-7.3) × 10–6. The unusual velocity suggests an association with a ~5'' diameter source, denoted Peak A, the Western Clump, or MF4. The mass of this source is ~10 Msun and the dust temperature is ≥150 K. Our preferred explanation of the enhanced O2 abundance is that dust grains in this region are sufficiently warm (T ≥ 100 K) to desorb water ice and thus keep a significant fraction of elemental oxygen in the gas phase, with a significant fraction as O2. For this small source, the line ratios require a temperature ≥180 K. The inferred O2 column density sime5 × 1018 cm–2 can be produced in Peak A, having N(H2) sime 4 × 1024 cm–2. An alternative mechanism is a low-velocity (10-15 km s–1) C-shock, which can produce N(O2) up to 1017 cm–2.

astrochemistry

interstellar molecules

submillimeter

interstellar medium

Författare

Paul F. Goldsmith

Jet Propulsion Laboratory, California Institute of Technology

René Liseau

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

Tom A. Bell

Centro de Astrobiologia (CAB)

John H Black

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

Jo-Hsin Chen

Jet Propulsion Laboratory, California Institute of Technology

David Hollenbach

SETI Institute

Michael J. Kaufman

San Jose State University

Di Li

Jet Propulsion Laboratory, California Institute of Technology

D. Lis

CalTech

G. J. Melnick

Harvard-Smithsonian Center for Astrophysics

D. A. Neufeld

Johns Hopkins University

Laurent Pagani

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

Ronald Snell

University of Massachusetts

A. O. Benz

Eidgenössische Technische Hochschule Zürich (ETH)

E. A. Bergin

University of Michigan

S. Bruderer

Eidgenössische Technische Hochschule Zürich (ETH)

P. Caselli

University of Leeds

E. Caux

Centre national de la recherche scientifique (CNRS)

Université de Toulouse

P. J. Encrenaz

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

E. Falgarone

Centre national de la recherche scientifique (CNRS)

M. Gerin

Centre national de la recherche scientifique (CNRS)

Javier R. Goicoechea

Centro de Astrobiologia (CAB)

Åke Hjalmarson

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

Bengt Larsson

Stockholm Observatory

Jacques Le Bourlot

LUTH - Laboratoire de l'Univers et de ses Theories

Franck Le Petit

LUTH - Laboratoire de l'Univers et de ses Theories

Massimo De Luca

LUTH - Laboratoire de l'Univers et de ses Theories

Zsofia Nagy

Rijksuniversiteit Groningen

Evelyne Roueff

LUTH - Laboratoire de l'Univers et de ses Theories

A. Sandqvist

Stockholm Observatory

F. F. S. van der Tak

Rijksuniversiteit Groningen

E. F. van Dishoeck

Max Planck-institutet

Universiteit Leiden

Charlotte Vastel

Centre national de la recherche scientifique (CNRS)

Université de Toulouse

Serena Viti

University College London (UCL)

U. A. Yildiz

Universiteit Leiden

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 737 2 96 (1-17) 96

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.1088/0004-637X/737/2/96

Mer information

Senast uppdaterat

2018-09-07