2000A&A...355..194V

We present the results of ISO SWS and LWS grating scans towards the three brightest members of the BD+40 4124 group in the infrared: BD+40 4124 (B2Ve), LkHα 224 (A7e) and the embedded source LkHα 225. Emission from the pure rotational lines of H₂, from ro-vibrational transitions of CO, from PAHs, from HI recombination lines and from the infrared fine structure lines of [FeII], [SiII], [SI], [OI], [OIII] and [CII] was detected. These emission lines arise in the combination of a low-density (≃10²cm^–3) HII region with a clumpy PDR in the case of BD+40 4124. The lower transitions of the infrared HI lines observed in BD+40 4124 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 HI lines and the radio continuum emission. In the lines of sight towards LkHα 224 and LkHα 225, the observed emission lines arise in a non-dissociative shock produced by a slow (≃20km/s) outflow arising from LkHα 225. Toward LkHα 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 LkHα 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 LkHα 225, making this the first line of sight where the bulk of the CO₂ is in the gas-phase.