Document Detail

Hot, metastable hydronium ion in the Galactic centre: formation pumping in X-ray-irradiated gas?
MedLine Citation:
PMID:  23028163     Owner:  NLM     Status:  PubMed-not-MEDLINE    
With a 3.5 m diameter telescope passively cooled to approximately 80 K, and a science payload comprising two direct detection cameras/medium resolution imaging spectrometers (PACS and SPIRE) and a very high spectral resolution heterodyne spectrometer (HIFI), the Herschel Space Observatory is providing extraordinary observational opportunities in the 55-670 μm spectral range. HIFI has opened for the first time to high-resolution spectroscopy the submillimetre band that includes the fundamental rotational transitions of interstellar hydrides, the basic building blocks of astrochemistry. We discuss a recent HIFI discovery of metastable rotational transitions of the hydronium ion (protonated water, H(3)O(+)), with rotational level energies up to 1200 K above the ground state, in absorption towards Sagittarius B2(N) in the Galactic centre. Hydronium is an important molecular ion in the oxygen chemical network. Earlier HIFI observations have indicated a general deficiency of H(3)O(+) in the diffuse gas in the Galactic disc. The presence of hot H(3)O(+) towards Sagittarius B2(N) thus appears to be related to the unique physical conditions in the central molecular zone, manifested, for example, by the widespread presence of abundant H(3)(+). One intriguing theory for the high rotational temperature characterizing the population of the H(3)O(+) metastable levels may be formation pumping in molecular gas irradiated by X-rays emitted by the Galactic centre black hole. Alternatively, the pervasive presence of enhanced turbulence in the central molecular zone may give rise to shocks in the lower-density medium that is exposed to energetic radiation.
Dariusz C Lis; Peter Schilke; Edwin A Bergin; Martin Emprechtinger;
Related Documents :
22947053 - Molecular dynamics simulations of the interactions of dmso with dppc and dopc phospholi...
23712623 - Travelling wave ion mobility and negative ion fragmentation for the structural determin...
18961803 - Radioisotope studies of carboxyl sites on strong acid and strong base ion-exchange resi...
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Philosophical transactions. Series A, Mathematical, physical, and engineering sciences     Volume:  370     ISSN:  1364-503X     ISO Abbreviation:  Philos Trans A Math Phys Eng Sci     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-10-02     Completed Date:  2012-11-13     Revised Date:  2013-04-24    
Medline Journal Info:
Nlm Unique ID:  101133385     Medline TA:  Philos Trans A Math Phys Eng Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  5162-73     Citation Subset:  -    
Cahill Center for Astronomy and Astrophysics 301-17, California Institute of Technology, Pasadena, CA 91125, USA.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Exploring the central molecular zone of the Galaxy using spectroscopy of H3+ and CO.
Next Document:  Hydride spectroscopy of the diffuse interstellar medium: new clues on the gas fraction in molecular ...