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Astron. Astrophys. 355, 194-210 (2000)


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ISO spectroscopy of young intermediate-mass stars in the BD+40o4124 group *

M.E. van den Ancker 1,2, P.R. Wesselius 3 and A.G.G.M. Tielens 3,4,5

1 Astronomical Institute "Anton Pannekoek", University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 42, Cambridge, MA 02138, USA
3 SRON, P.O. Box 800, 9700 AV Groningen, The Netherlands
4 Kapteyn Astronomical Institute, Groningen University, P.O. Box 800, 9700 AV Groningen, The Netherlands
5 NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA

Received 15 June 1999 / Accepted 4 January 2000

Abstract

We present the results of ISO SWS and LWS grating scans towards the three brightest members of the BD+40o4124 group in the infrared: BD+40o4124 (B2Ve), LkH[FORMULA] 224 (A7e) and the embedded source LkH[FORMULA] 225. Emission from the pure rotational lines of H2, from ro-vibrational transitions of CO, from PAHs, from H I recombination lines and from the infrared fine structure lines of [Fe II], [Si II], [S I], [O I], [O III] and [C II] was detected. These emission lines arise in the combination of a low-density ([FORMULA] 102 cm-3) H II region with a clumpy PDR in the case of BD+40o4124. The lower transitions of the infrared H I lines observed in BD+40o4124 are optically thick; most likely they arise in either a dense wind or a circumstellar disk. This same region is also responsible for the optical H I lines and the radio continuum emission. In the lines of sight towards LkH[FORMULA] 224 and LkH[FORMULA] 225, the observed emission lines arise in a non-dissociative shock produced by a slow ([FORMULA] 20 km s-1) outflow arising from LkH[FORMULA] 225. Toward LkH[FORMULA] 225 we also observe a dissociative shock, presumably located closer to the outflow source than the non-dissociative shock. In the line of sight towards LkH[FORMULA] 225 we observed absorption features due to solid water ice and amorphous silicates, and due to gas-phase H2O, CO and CO2. No solid CO2 was detected towards LkH[FORMULA] 225, making this the first line of sight where the bulk of the CO2 is in the gas-phase.

Key words: shock waves – stars: circumstellar matter – stars: formation – ISM: H ii regions – ISM: jets and outflows – infrared: stars

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

Send offprint requests to: M.E. van den Ancker (mario@astro.uva.nl)

© European Southern Observatory (ESO) 2000

Online publication: March 17, 2000

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