dc.contributor.author | Tine, S. | |
dc.contributor.author | Lepp, S. | |
dc.contributor.author | Gredel, R. | |
dc.contributor.author | Dalgarno, A. | |
dc.date.accessioned | 2019-09-24T17:24:57Z | |
dc.date.issued | 1997 | |
dc.identifier.citation | Tine, S., S. Lepp, R. Gredel, and A. Dalgarno. 1997. “Infrared Response of H2to X‐Rays in Dense Clouds.” The Astrophysical Journal 481 (1): 282–95. https://doi.org/10.1086/304048. | |
dc.identifier.issn | 0004-637X | |
dc.identifier.issn | 1538-4357 | |
dc.identifier.uri | http://nrs.harvard.edu/urn-3:HUL.InstRepos:41397389 | * |
dc.description.abstract | The excitation by X-rays and cosmic rays of molecular hydrogen in interstellar clouds is analyzed. We carried out detailed calculations of entry efficiencies in rovibrational levels of H-2 following impact with fast electrons produced by X-ray ionization of the gas. The competing effect of collisional excitation, and quenching, by the ambient gas is examined in detail. Up to date values for H-H-2 collisional rate coefficients are adopted, and some derivations of H-2-H-2 rovibrational rate coefficients from existing literature data are proposed. Several models as a function of temperature, density, and ionization rate are presented. We found that H-2 infrared emission in X-ray dominated regions (XDR) is potentially observable for temperatures and ionization rates lower than certain critical values (typically T < 1000 K and zeta/n(H) < 10(-15) cm(3) s(-1), where zeta is the ionization rate). At higher temperatures, collisional excitation by the ambient gas dominates the population of low vibrational levels, and at higher values of zeta/n(H), the abundance of H-2 is negligible. If such conditions are satisfied, the resulting infrared emission spectrum can be used as a diagnostic of nearby X-ray sources such as in cooling flows in galaxy clusters, quasars, Seyfert galaxies and supernova remnants. The intensity ratio of the 2-1S(1) and 1-0S(1) lines measured for the Seyfert galaxy NGC 1275 is consistent with X-ray pumping. | |
dc.language.iso | en_US | |
dc.publisher | American Astronomical Society | |
dash.license | LAA | |
dc.title | Infrared Response of H 2 to X‐Rays in Dense Clouds | |
dc.type | Journal Article | |
dc.description.version | Version of Record | |
dc.relation.journal | The Astrophysical Journal | |
dash.depositing.author | Dalgarno, Alexander::501fae4cfad8b04754ee2838c45fc5d0::600 | |
dc.date.available | 2019-09-24T17:24:57Z | |
dash.workflow.comments | 1Science Serial ID 95214 | |
dc.identifier.doi | 10.1086/304048 | |
dash.source.volume | 481;1 | |
dash.source.page | 282-295 | |