Limits on the cosmic-ray ionization rate toward massive young stars
| dc.creator | van der Tak, Floris F. S. | |
| dc.creator | van Dishoeck, Ewine F. | |
| dc.date | 2000-06-19 | |
| dc.date.accessioned | 2026-07-07T01:54:00Z | |
| dc.date.available | 2026-07-07T01:54:00Z | |
| dc.description | Recent models of the envelopes of seven massive protostars are used to analyze observations of H3+ infrared absorption and H13CO+ submillimeter emission lines toward these stars, and to constrain the cosmic-ray ionization rate zeta. The H13CO+ gives best-fit values of zeta=(2.6+/- 1.8) x 10^-17 s^-1, in good agreement with diffuse cloud models and with recent Voyager/Pioneer data but factors of up to 7 lower than found from the H3+ data. No relation of zeta with luminosity or total column density is found, so that local (X-ray) ionization and shielding against cosmic rays appear unimportant for these sources. The difference between the H3+ and H13CO+ results and the correlation of N(H3+) with heliocentric distance suggest that intervening clouds contribute significantly to the H3+ absorptions in the more distant regions. The most likely absorbers are low-density (<~10^4 cm^-3) clouds with most carbon in neutral form or in CO. | |
| dc.description | To be published in A&A 358 (Letters); 4 pages including 3 figures | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0006246 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0006246 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/1182 | |
| dc.subject | Astrophysics | |
| dc.title | Limits on the cosmic-ray ionization rate toward massive young stars | |
| dc.type | text |