Similarity and randomness in the molecular clouds associated with Spitzer GLIMPSE Extended Green Objects (EGOs)

Abstract

EGOs are candidates of massive star forming regions that show signatures of outflows. A 1.1mm line survey has been performed to 89 EGOs using the AROSMT. Our high detection rates of H¹³CO⁺ 3-2 and SiO 6-5 lines support EGOs to be dense clouds harboring outflows.

Ubiquitous line luminosity linear correlations are found among different kinds of tracer lines: dense gas tracer H¹³CO⁺ 3-2, outflow tracer SiO 6-5, mixed dense gas and outflow tracers SO³Σ 6₅ − 5₄ and CH₃OH lines, and relatively lower density gas tracers ¹²CO, ¹³CO, C¹⁸O 1-0 (see an example in Fig. 1). This can be explained if a universal similarity of density and thermal structures and probably of shock properties among all these EGO clouds are assumed. Furthermore, the outflow shocks are also required to be produced mainly inside of the natal clouds of the YSOs.

The data scatter of the luminosity (and line width) correlations show a clear trend of worsening across larger cloud substructure size scales or toward larger cloud sizes, which demonstrates the growth of randomness in cloud structures and velocity fields. See more details in our paper (He et al. 2012).