A VLT spectroscopic study of the ultracompact HII region G29.96-0.02
| Autor: | Arjan Bik, Margaret M. Hanson, Alexander G. G. M. Tielens, N. L. Martin-Hernandez, Lex Kaper |
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| Přispěvatelé: | Astronomy, Low Energy Astrophysics (API, FNWI) |
| Jazyk: | angličtina |
| Rok vydání: | 2003 |
| Předmět: |
HII regions
infrared : ISM NEAR-INFRARED SPECTROSCOPY Astrophysics::High Energy Astrophysical Phenomena RECOMBINATION-LINE FOS: Physical sciences PHYSICAL-PROPERTIES Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics ISM : individual : G29.96-0.02 Astrophysics::Solar and Stellar Astrophysics Bow shock (aerodynamics) Emission spectrum RADIO-CONTINUUM Astrophysics::Galaxy Astrophysics ISM : kinematics and dynamics Line (formation) O-type star Physics Nebula Very Large Telescope LUMINOUS STARS Astrophysics (astro-ph) EFFECTIVE TEMPERATURE Astronomy and Astrophysics Effective temperature H-II-REGIONS Space and Planetary Science stars : early type Electron temperature VELOCITY STRUCTURE Astrophysics::Earth and Planetary Astrophysics ISM : lines and bands ISO SPECTROSCOPY MASSIVE STARS |
| Zdroj: | Astronomy & astrophysics, 405(1), 175-188. EDP Sciences Astronomy & Astrophysics, 405, 175-188. EDP Sciences |
| ISSN: | 1432-0746 0004-6361 |
| DOI: | 10.1051/0004-6361:20030631 |
| Popis: | A high quality, medium-resolution K-band spectrum has been obtained of the ultracompact HII region G29.96-0.02 with the Very Large Telescope (VLT). The slit was positioned along the symmetry axis of the cometary shaped nebula. Besides the spectrum of the embedded ionizing O star, the long-slit observation revealed the rich emission-line spectrum produced by the ionized nebula with sub-arcsec spatial resolution. The nebular spectrum includes Br$\gamma$, several helium emission lines and a molecular hydrogen line. A detailed analysis is presented of the variation in strength, velocity and width of the nebular emission lines along the slit. The results are consistent with previous observations, but the much better spatial resolution allows a critical evaluation of models explaining the cometary shape of the nebula. Our observations support neither the wind bow shock model nor the champagne flow model. The measured line ratios of the nebular hydrogen and helium lines are compared to predictions from case B recombination-line theory. The results indicate an electron temperature between 6400 and 7500 K, in good agreement with other determinations and the Galactocentric distance of 4.6 kpc. The He$^{+}$/H$^{+}$ ratio is practically constant over the slit; we argue that He is singly ionized throughout the nebula. We review the various observational constraints on the effective temperature of the ionizing star and show that these are in agreement with its K-band spectral type of O5-O6V. Comment: 15 pages including 11 figures and 2 tables, LaTex, A&A style. Accepted for publication in A&A |
| Databáze: | OpenAIRE |
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