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Register a new userCatalogue of 12CO(J=1-0) and 13CO(J=1-0) Molecular Clouds in the Carina Flare Supershell
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We present a catalogue of 12CO(J=1-0) and 13CO(J=1-0) molecular clouds in the spatio-velocity range of the Carina Flare supershell, GSH 287+04-17. The data cover a region of ~66 square degrees and were taken with the NANTEN 4m telescope, at spatial and velocity resolutions of 2.6 and 0.1 km/s. Decomposition of the emission results in the identification of 156 12CO clouds and 60 13CO clouds, for which we provide observational and physical parameters. Previous work suggests the majority of the detected mass forms part of a comoving molecular cloud complex that is physically associated with the expanding shell. The cloud internal velocity dispersions, degree of virialization and size-linewidth relations are found to be consistent with those of other Galactic samples. However, the vertical distribution is heavily skewed towards high-altitudes. The robust association of high-z molecular clouds with a known supershell provides some observational backing for the theory that expanding shells contribute to the support of a high-altitude molecular layer.
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We present 12CO J=1-0 observations from the Caltech Millimeter Array of a field in the nearby spiral galaxy M81. We detect emission from three features that are the size of large giant molecular clouds (GMCs) in the Milky Way Galaxy and M31, but are larger than any known in M33 or the SMC. The M81 clouds have diameters approximately 100 pc and molecular masses 3 * 10^5 solar masses. These are the first GMCs to be detected in such an early type galaxy (Sab) or in a normal galaxy outside the Local Group. The clouds we have detected do not obey the size-linewidth relation obeyed by GMCs in our Galaxy and in M33, and some of them may be GMC complexes that contain several small GMCs. One of these does show signs of sub-structure, and is shaped like a ring section with three separate peaks. At the center of this ring section lies a giant HII region, which may be associated with the molecular clouds.
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 gamma-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 ~Myrs. 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 gamma-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 gamma-rays, although none of the known microquasars have a Myr age or steady TeV gamma-rays. Alternatively, an anisotropic supernova explosion which occurred ~Myr ago may be able to form the jet and arc clouds, whereas the TeV gamma-ray emission requires a microquasar formed after the explosion.
We present 13CO(1-0) and 12CO(2-1) aperture synthesis maps of the barred spiral galaxy NGC1530. The angular resolutions are respectively 3.1 and 1.6. Both transitions show features similar to the 12CO(1-0) map, with a nuclear feature (a ring or unresolved spiral arms) surrounded by two curved arcs. The average line ratios are 12CO(1-0)/13CO(1-0)=9.3 and 12CO(2-1)/12CO(1-0)=0.7. The 12CO/13CO ratio is lower in the circumnuclear ring (6-8) than in the arcs (11-15). We fit the observed line ratios by escape probability models, and deduce that the gas density is probably higher in the nuclear feature (>= 5 10^2 cm^{-3}) than in the arcs (~2 10^2 cm^{-3}), confirming earlier HCN results. The kinetic temperatures are in the range 20-90K, but are weakly constrained by the model. The average filling factor of the 12CO(1-0) emitting gas is low, ~0.15. The cm-radio continuum emission also peaks in the nuclear feature, indicating a higher rate of star formation than in the arcs. We derive values for the CO luminosity to molecular gas mass conversion factor between 0.3 and 2.3 Msolar (K km/s pc^2)^{-1}, significantly lower than the standard Galactic value.
M16, the Eagle Nebula, is an outstanding HII region where extensive high-mass star formation is taking place in the Sagittarius Arm, and hosts the remarkable pillars observed with HST. We made new CO observations of the region in the 12CO J=1--0 and J=2--1 transitions with NANTEN2. These observations revealed for the first time that a giant molecular cloud of $sim 1.3 times 10^5$ Msun is associated with M16, which is elongated vertically to the Galactic plane over 35 pc at a distance of 1.8 kpc. We found a cavity of the molecular gas of $sim 10$ pc diameter toward the heart of M16 at lbeq (16.95degree, 0.85degree), where more than 10 O-type stars and $sim 400$ stars are associated, in addition to a close-by molecular cavity toward a Spitzer bubble N19 at lbeq (17.06degree, 1.0degree). We found three velocity components which show spatially complementary distribution in the entire M16 giant molecular cloud (GMC) including NGC6611 and N19, suggesting collisional interaction between them. Based on the above results we frame a hypothesis that collision between the red-shifted and blue-shifted components at a relative of $sim 10$ kms triggered formation of the O-type stars in the M16 GMC in the last 1-2 Myr. The collision is two fold in the sense that one of the collisional interactions is major toward the M16 cluster and the other toward N19 with a RCW120 type, the former triggered most of the O star formation with almost full ionization of the parent gas, and the latter an O star formation in N19.
We present a study using the Karl G. Jansky Very Large Array of 12CO J=1-0 emission in three strongly lensed submillimetre-selected galaxies (SMMJ16359, SMMJ14009 and SMMJ02399) at z=2.5-2.9. These galaxies span L(IR) = 10^11 - 10^13 Lsun, offering an opportunity to compare the interstellar medium of LIRGs and ULIRGs at high redshift. We estimate molecular gas masses in the range (2-40) x 10^9 Msun using a method that assumes canonical underlying brightness temperature ratios for star-forming and non-star-forming gas phases and a maximal star-formation efficiency. A more simplistic method using X(CO) = 0.8 yields gas masses twice as high. The observed CO(3-2)/CO(1-0) brightness temperature ratio for SMMJ14009, r(3-2)/(1-0) = (0.95 pm 0.12), is indicative of warm star-forming gas, possibly influenced by the central AGN. We search for 12CO(1-0) emission in the Lyman-break galaxy, A2218 #384, located at z=2.517 in the same field as SMMJ16359, and assign a 3-sigma gas mass limit of <6 x 10^8 Msun. We use rest-frame 115-GHz free-free flux densities in SMMJ14009 and SMMJ02399 - measurements tied directly to the photionisation rate of massive stars and made possible by the VLAs bandwidth - to estimate star-formation rates of 400-600 Msun/yr and to estimate the fraction of L(IR) due to the AGN.
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