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
Received 15 June 1999 / Accepted 4 January 2000
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 224 (A7e) and the embedded source LkH 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 ( 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 224 and LkH 225, the observed emission lines arise in a non-dissociative shock produced by a slow ( 20 km s-1) outflow arising from LkH 225. Toward LkH 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 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 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 (firstname.lastname@example.org)
© European Southern Observatory (ESO) 2000
Online publication: March 17, 2000