أعرض تسجيلة المادة بشكل مبسط

dc.creator Goicoechea, Javier R.
dc.creator Rodríguez-Fernández, Nemesio J.
dc.creator Cernicharo, José
dc.date 2008-01-02T15:46:26Z
dc.date 2008-01-02T15:46:26Z
dc.date 2003-03-05
dc.date.accessioned 2017-01-31T00:59:38Z
dc.date.available 2017-01-31T00:59:38Z
dc.identifier Astronomische Nachrichten Volume 324, Issue S1 , Pages 139 - 143
dc.identifier arXiv:astro-ph/0303118v1
dc.identifier http://hdl.handle.net/10261/2648
dc.identifier 10.1002/asna.200385087
dc.identifier.uri http://dspace.mediu.edu.my:8181/xmlui/handle/10261/2648
dc.description We present large scale 9' x 27' (25 pc x 70 pc) far-IR observations of the Sgr B2 complex using the spectrometers on board the Infrared Space Observatory (ISO). The far-IR spectra are dominated by the strong continuum emission of dust and by the fine structure lines of high excitation potential ions (NII, NIII and OIII) and those of neutral or weakly ionized atoms (OI and CII). The line emission has revealed a very extended component of ionized gas. The study of the NIII 57 microns/NII 122 microns and OIII 52/88 microns line intensity ratios show that the ionized gas has a density of n_e~10^{2-3} cm^-3 while the ionizing radiation can be characterized by a diluted but hard continuum, with effective temperatures of ~35000 K. Photoionization models show that the total number of Lyman photons needed to explain such an extended component is approximately equal to that of the HII regions in Sgr B2(N) and (M) condensations. We propose that the inhomogeneous and clumpy structure of the cloud allows the radiation to reach large distances through the envelope. Therefore, photodissociation regions (PDRs) can be numerous at the interface of the ionized and the neutral gas. The analysis of the OI (63 and 145 microns) and CII (158 microns) lines indicates an incident far-UV field (G_0, in units of the local interstellar radiation field) of 10^{3-4} and a H density of 10^{3-4} cm^{-3} in such PDRs. We conclude that extended photoionization and photodissociation are also taking place in Sgr B2 in addition to more established phenomena such as widespread low--velocity shocks.
dc.description Peer reviewed
dc.format 483417 bytes
dc.format application/pdf
dc.language eng
dc.publisher John Wiley & Sons
dc.relation Preprint
dc.rights closedAccess
dc.subject Galaxy: center
dc.subject Infrared: ISM: lines and ba
dc.subject Nds
dc.subject ISM: dust
dc.subject Extinction
dc.subject H II regions
dc.subject ISM: individual (Sagittarius B2)
dc.title Extended photoionization and photodissociation in Sgr B2
dc.type Pre-print


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