Volume 464, Number 3, March IV 2007
|Page(s)||995 - 1002|
|Section||Interstellar and circumstellar matter|
|Published online||11 January 2007|
Helium abundance and ionization structure in the Orion nebula: radio recombination lines observations*
INAF – Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Str. 54, 09012 Capoterra (CA), Italy e-mail: firstname.lastname@example.org
2 P.N Lebedev Physical Institute, Academy of Sciences of Russia, Moscow, Russia
3 Isaac Newton Institute of Chile, Pushchino Branch, Pushchino, 142290 Russia
4 INAF – IASF Sezione di Bologna, via P. Gobetti 101, 40129 Bologna, Italy
5 Università degli Studi, Dipartimento di Astronomia, 40129 Bologna, Italy
Accepted: 27 November 2006
Results of the Ori A HII region mapping based on hydrogen (H), helium (He) and carbon (C) Radio Recombination lines (RRL) are presented. Observations were made with the same angular resolution () using the 32 m VLBI dish of Medicina (Italy, 22.4 GHz) and the Pushchino RT-22 dish (Russia, 36.5 GHz). The behaviour of the ionized helium abundance, y+, with distance from the center shows that the He+ zone size is smaller than that of H+. Such a behaviour is different for the core and for the envelope, as well as for different directions from the center. The helium abundance, %, is measured. Derived line radial velocities, their widths and y+ data support the well-known “blister-type” structure of this HII region. LTE electron temperatures ( K) are also measured.
Key words: ISM: abundances / ISM: HII regions / radio lines: ISM / ISM: individual objects: Orion Nebula
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.