Journal Article

Sh2-205 – I. The surrounding interstellar medium

G. A. Romero and C. E. Cappa

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 3, pages 1080-1092
Published in print July 2008 | ISSN: 0035-8711
Published online May 2008 | e-ISSN: 1365-2966 | DOI:
Sh2-205 – I. The surrounding interstellar medium

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We investigate the distribution of the interstellar matter in the environs of the H ii region Sh2-205, based on neutral hydrogen 21-cm-line data and radio continuum images at 408 and 1420 MHz obtained from the CGPS, 12CO (J=1 →0) observations, high-resolution IRAS data (HIRES), and MSX data.

Sh2-205 can be separated into three distinct optical structures: SH 149.25–0.0, SH 148.83–0.67, and LBN 148.11–0.45. The three regions are detected at both 408 and 1420 MHz. The derived spectral indices show the thermal nature of SH 148.83–0.67 and LBN 148.11–0.45.

LBN 148.11–0.45 is a classical H ii region surrounded by an H i shell. The associated neutral atomic and ionized masses are 65 M and 70 M, respectively. Dust and molecular gas (∼6 × 104M) related to this ionized region have been found. In particular, a photodissociation region is detected at the interface between the ionized and molecular regions. If the proposed exciting star HD 24094 were an O8–O9 type star, as suggested by its near-infrared colours, its UV photon flux would be strong enough to explain the ionization of the nebula.

The optical, radio continuum, and 21-cm-line data allow us to conclude that SH 148.83–0.67 is an interstellar bubble powered by the energetic action of HD 24431. The associated neutral atomic and ionized masses are 180 M and 300 M, respectively. The emission of SH 149.25–0.0 is too faint to derive the dust and gas parameters.

An H i shell centred at (l, b) = (149°0′, −1°30′) was also identified. It correlates morphologically with the molecular gas emission. The neutral atomic and molecular masses of the shell are 1600 M and 2.6 × 104M, respectively. The open cluster NGC 1444 is probably responsible for shaping this H i structure.

Keywords: stars: individual: HD 24431; stars: individual: ALS 7793; stars: individual: HD 24094; ISM: bubbles - ISM: structure

Journal Article.  8744 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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