Herschel observations of extra-ordinary sources: H{sub 2}S as a probe of dense gas and possibly hidden luminosity toward the Orion KL hot core

Journal Article · Sat Feb 01 04:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/781/2/114· OSTI ID:22348098

Crockett, N. R.; Bergin, E. A.; Neill, J. L. ^[1]; Black, J. H. ^[2]; Blake, G. A.; Kleshcheva, M. ^[3]

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1. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
2. Department of Earth and Space Sciences, Chalmers University of Technology, Onsala (Sweden)
3. California Institute of Technology, Division of Geological and Planetary Sciences, MS 150-21, Pasadena, CA 91125 (United States)

We present Herschel/HIFI observations of the light hydride H{sub 2}S obtained from the full spectral scan of the Orion Kleinmann-Low nebula (Orion KL) taken as part of the Herschel Observations of EXtra-Ordinary Sources GT (guaranteed time) key program. In total, we observe 52, 24, and 8 unblended or slightly blended features from H{sub 2} {sup 32}S, H{sub 2} {sup 34}S, and H{sub 2} {sup 33}S, respectively. We only analyze emission from the so-called hot core, but emission from the plateau, extended ridge, and/or compact ridge are also detected. Rotation diagrams for ortho and para H{sub 2}S follow straight lines given the uncertainties and yield T {sub rot} = 141 ± 12 K. This indicates H{sub 2}S is in local thermodynamic equilibrium and is well characterized by a single kinetic temperature or an intense far-IR radiation field is redistributing the population to produce the observed trend. We argue the latter scenario is more probable and find that the most highly excited states (E {sub up} ≳ 1000 K) are likely populated primarily by radiation pumping. We derive a column density, N {sub tot}(H{sub 2} {sup 32}S) = 9.5 ± 1.9 × 10{sup 17} cm{sup –2}, gas kinetic temperature, T {sub kin} = 120±{sub 10}{sup 13} K, and constrain the H{sub 2} volume density, n{sub H{sub 2}} ≳ 9 × 10 {sup 7} cm{sup –3}, for the H{sub 2}S emitting gas. These results point to an H{sub 2}S origin in markedly dense, heavily embedded gas, possibly in close proximity to a hidden self-luminous source (or sources), which are conceivably responsible for Orion KL's high luminosity. We also derive an H{sub 2}S ortho/para ratio of 1.7 ± 0.8 and set an upper limit for HDS/H{sub 2}S of <4.9 × 10 {sup –3}.

• OSTI ID: 22348098
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 781; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
DENSITY
EMISSION
EXCITED STATES
HYDRIDES
HYDROGEN
HYDROGEN SULFIDES
INFRARED RADIATION
LTE
LUMINOSITY
MOLECULES
NEBULAE
SULFUR 32
SULFUR 33
SULFUR 34
VISIBLE RADIATION