Far and mid infrared observations of two ultracompact $\ion{H}{ii}$ regions and one compact CO clump

Abstract

Abstract.Two ultracompact H  regions (IRAS 19181+1349 and 20178+4046) and one compact molecular clump (20286+4105) have been observed at far infrared wavelengths using the TIFR 1 m balloon-borne telescope and at mid infrared wavelengths using ISO. Far infrared observations have been made simultaneously in two bands with effective wavelengths of ∼150 and ∼210 µm, using liquid 3 He cooled bolometer arrays. ISO observations have been made in seven spectral bands using the ISOCAM instrument; four of these bands cover the emission from Polycyclic Aromatic Hydrocarbon (PAH) molecules. In addition, IRAS survey data for these sources in the four IRAS bands have been processed using the HIRES routine. In the high resolution mid infrared maps as well as far infrared maps multiple embedded energy sources have been resolved. There are structural similarities between the images in the mid infrared and the large scale maps in the far infrared bands, despite very different angular resolutions of the two. Dust temperature and optical depth (τ 150 ) maps have also been generated using the data from balloon-borne observations. Spectral energy distributions (SEDs) for these sources have been constructed by combining the data from all these observations. Radiation transfer calculations have been made to understand these SEDs. Parameters for the dust envelopes in these sources have been derived by fitting the observed SEDs. In particular, it has been found that the radial density distribution for three sources is different. Whereas in the case of IRAS 20178+4046 a steep distribution of the form r −2 is favoured, for IRAS 20286+4105 it is r −1 and for IRAS 19181+1349 it is a uniform distribution (r 0 ). Line ratios for PAH bands have generally been found to be similar to those for other compact H  regions but different to general H  regions.

Radio and infrared study of the star-forming region IRAS 20286+4105

“…The cold dust environment sampled by 250 µm (red) emission is more extended and dominant towards the northern edge, whereas the warm dust sampled by the 24 µm (blue) emission is mostly localized in these two regions being brighter towards the southern one. These regions are also identified as the northern and southern cores and studied by Verma et al (2003). From the radiative transfer modeling of the MIR and FIR data, these authors suggest the luminosities of the two cores to be consistent with ZAMS stars of spectral type B0.5 (northern core) and B0 -B0.5 (southern core).…”

“…The spectral type determined from this work is within one subclass of the estimates obtained from previous radio continuum studies by Odenwald & Schwartz (1989) and McCutcheon et al (1991) after scaling to the distance and electron temperature used in our study. Verma et al (2003) carried out the radiative transfer modeling of two FIR cores located towards the cloud centre (see Section 3.5) using MIR and FIR data and estimated the spectral type of the sources associated with these cores to be between B0.5 -B0. Their modeling predicted no radio emission.…”

“…This complex has been the target of a couple of radio continuum observations (Wendker 1984;Wendker, Higgs & Landecker 1991;McCutcheon et al 1991). In the FIR, this region has been studied in detail by Verma et al (2003) at 150 and 210 µm using the balloon-borne TIFR telescope. IRAS 20286+4105 also forms part of the Balloonborne Large Aperture Submillimeter Telescope (BLAST) survey of the Cygnus region at 250, 350 and 500 µm (Roy et al 2011).…”

A multiwavelength study of the ultracompact HII region associated with IRAS 20178+4046

“…In a recent study, Verma et al (2003) mapped this source in two FIR bands (∼150 and 210 µm) with the 1 m TIFR GMRT data is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/468/1001…”

High Excitation ISM and Gas

“…Several studies were devoted to the spatial distribution of the different emission components Verstraete et al, 1996;Pilbratt et al, 1998;Créte et al, 1999;Klein et al, 1999;Zavagno & Ducci, 2001;Urquhart et al, 2003;Verma et al, 2003). It is overwhelmingly clear that the UIR bands peak in the PDR, though closer to the ionized star with respect to H 2 , while the strong dust continuum peaks towards the H ii region.…”