A multiwavelength study of IRAS 19550+3248: A protostar possibly formed by a cloud-cloud collision

초록

We have carried out radio, near-infrared, and optical observations of the IRAS point source IRAS 19550+3248. 12CO J = 1-0 line observations revealed a high-velocity (HV) molecular outflow centered on IRAS 19550+3248. The HV gas has a bipolar pattern with the blue and red peaks separated by 1′ along the north-south direction. The mechanical luminosity of the HV molecular outflow is ∼9 × 1031d<inf>2</inf> ergs s-1, and its dynamical age is ∼5 × 104d<inf>2</inf> yr, where d<inf>2</inf> is the distance to the source normalized to 2 kpc. Inside the 95% confidence ellipse of IRAS position, we have detected a nebulous K band source. The nebulosity extends to 0.1d<inf>2</inf> pc in the east-west direction. In R and I bands, the source appears to be composed of two extended weak peaks shifted toward the blueshifted CO lobe from the peak position in K band. These near-infrared emission features are likely scattered stellar light. The infrared source has a steep spectral index between 2 and 25 μm (d log [vF<inf>v</inf>]/d log v = -0.93), which indicates that it is a protostar deeply embedded in a dense molecular cloud core. The bolometric luminosity based on R, I, H, and K band photometry together with the IRAS data is 150d2<inf>2</inf> L<inf>⊙</inf>. IRAS 19550+3248 is located at the center of a small (4′ × 7′) dense molecular clump. The clump is at the tip of a long (∼1°) filamentary molecular cloud. The molecular cloud is composed of clumps which are not confined by gravity and nor, probably, by external pressure. The characteristic timescale for dispersal is ∼6 × 106 yr. We suggest cloud-cloud collision as a possible mechanism for the disruption of the cloud and for the formation of IRAS 19550+3248.

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