THE BALLOON-BORNE LARGE APERTURE SUBMILLIMETER TELESCOPE (BLAST) 2005: A 10 deg²SURVEY OF STAR FORMATION IN CYGNUS X

Abstract

We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500 μm, combined with rich data sets for this well-studied region. Our primary goal is to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40 K contain well-known compact H ii regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (∼10 K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold "starless cores" more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are "starless" in the sense that to date there is no massive protostar in a vigorous accretion phase. We discuss evolution in the context of the L-M diagram. Theory raises some interesting possibilities: some cold massive compact sources might never form a cluster containing massive stars, and clusters with massive stars might not have an identifiable compact cold massive precursor.

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

“…In this paper we adopt a recent distance estimate of 1.61 kpc, obtained from maser astrometry . This is consistent with the adopted values in recent studies of the Cygnus region (Schneider et al 2006;Roy et al 2011). Based on its luminosity and IRAS colours, IRAS 20286+4105 has been proposed as a candidate highmass protostellar object (Molinari et al 1996).…”

“…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). Based on the near-infrared (NIR) H2 line maps, Varricatt et al (2010) have identified two outflows, the positions of which are consistent with the CO outflow results of Zhang et al (2005).…”

“…Based on the age of the Cyg OB2 cluster and the distance to it, it is possible that the ionization front emanating from the massive stellar population of the cluster would have reached and ionized the IRAS 20286+4105 cloud. From the mass, luminosity and the geometry of the IRAS 20286+4105 cloud, Roy et al (2011) suggest that the radio emission is possibly due to this external ionization field. It should be noted here that the authors do not give any quantitative proof for the above inference.…”

“…IRAS 20286+4105 cloud falls within the radius of influence of this cluster (Schneider et al 2006;Roy et al 2011) being located at a distance of ∼20 pc from the cluster centre. Based on the age of the Cyg OB2 cluster and the distance to it, it is possible that the ionization front emanating from the massive stellar population of the cluster would have reached and ionized the IRAS 20286+4105 cloud.…”

“…IRAS 20286+4105 (Mol 126; G79.873+1.179; α2000 = 20 h 30 m 29.9 s , δ2000 = +41 • 15 51 ) is a star forming complex in the Cygnus -X region with a far-infrared (FIR) luminosity of 5.3 ×10 3 L (Roy et al 2011). The distance estimates for this region vary from ∼ 1 kpc (Comerón & Torra 2001;Odenwald & Schwartz 1989) to ∼ 4 kpc (Palla et al 1991).…”