THE JET AND ARC MOLECULAR CLOUDS TOWARD WESTERLUND 2, RCW 49, AND HESS J1023–575;¹²CO AND¹³CO (J= 2-1 andJ= 1-0) OBSERVATIONS WITH NANTEN2 AND MOPRA TELESCOPE

Abstract

We have made new CO observations of two molecular clouds, which we call "jet" and "arc" clouds, toward the stellar cluster Westerlund 2 and the TeV γ -ray source HESS J1023−575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023−575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be ∼Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV γ -ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV γ -rays, although none of the known microquasars have a Myr age or steady TeV γ -rays. Alternatively, an anisotropic supernova explosion which occurred ∼Myr ago may be able to form the jet and arc clouds, whereas the TeV γ -ray emission requires a microquasar formed after the explosion.

A High-resolution Multiband Survey of Westerlund 2 with the Hubble Space Telescope. III. The Present-day Stellar Mass Function

“…The studies of the CO emission spectrum in combination with the 21 cm absorption spectrum by Dame (2007) suggest that Wd2 must be located in between two molecular clouds. Wd2 was studied in more detail by Furukawa et al (2009Furukawa et al ( , 2014 and Ohama et al (2010) using the NAN-TEN 2 4m submillimeter/millimeter telescope (from the NANTEN CO Galactic Plane Survey, Mizuno & Fukui 2004) in combination with Spitzer data. They detected three different CO clouds with 3 different velocities (16, 4, and −4 km s −1 , relative to the local standard of rest (LSR), see Fig.…”

“…Using the rotation curve of Brand & Blitz (1993), Furukawa et al (2009) obtained kinematic distances of 6.5, 5.2, and 4.0 kpc for the 16, 4, and −4 km s −1 clouds, respectively. Furukawa et al (2009Furukawa et al ( , 2014 and Ohama et al (2010) also suggested that the creation of the RCW 49 region, with the Wd2 cluster as its central ionizing cluster, was induced by a cloud-cloud collision of two of these observed molecular clouds. This collision may have caused the formation of the spatially uniformly distributed low-mass PMS stars that we see in our HST data.…”

Magnetohydrodynamic Simulations of the Formation of Molecular Clouds toward the Stellar Cluster Westerlund 2: Interaction of a Jet with a Clumpy Interstellar Medium

“…Let us compare our results with CO observations (Furukawa et al 2014). The velocity dispersion of the molecular clouds formed by the jet-cloud interaction depends on the jet speed.…”

“…HESS J1023-575 is observed both at the high energy band (above 2.5 TeV) and the low energy band (0.7 − 2.5 TeV). The cooling by the pp-interaction and diffusion time scales of the relativistic particles are estimated to be about 5 × 10 6 yr and 2 × 10 4 yr, respectively, by Furukawa et al (2014). If the arc and the jet clouds and TeV γ-ray source are produced by a single object, a supernova remnant or a pulsar wind nebulae is not likely as the origin for TeV γ-ray source since the diffusion time scale of the relativistic particles is shorter than the age of the arc and jet clouds (∼ Myr).…”

High-J CO emission spatial distribution and excitation in the Orion Bar

“…The reduced maps (FITS files) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A77 in many environments, for instance, in photodissociation regions (PDRs), protoplanetary disks, young stellar objects (YSOs; Martín et al 2009;Sturm et al 2010;Furukawa et al 2014), and different extragalactic environments, such as low surface brightness galaxies, high-redshift galaxies, and ultra-luminous infrared galaxies (ULIRGs;O'Neil et al 2000;Schleicher et al 2010;Papadopoulos et al 2010).…”