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Register a new userVLA imaging of 12CO J=1-0 and free-free emission in lensed submillimetre galaxies
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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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We present Submillimeter Array (SMA) [CII] 158um and Jansky Very Large Array (JVLA) $^{12}$CO(1-0) line emission maps for the bright, lensed, submillimeter source at $z=5.2430$ behind Abell 773: HLSJ091828.6+514223 (HLS0918). We combine these measurements with previously reported line profiles, including multiple $^{12}$CO rotational transitions, [CI], water and [NII], providing some of the best constraints on the properties of the interstellar medium (ISM) in a galaxy at $z>5$. HLS0918 has a total far-infrared (FIR) luminosity L_FIR(8-1000um) = (1.6$pm$0.1)x10^14 L_sun/mu, where the total magnification mu_total = 8.9$pm$1.9, via a new lens model from the [CII] and continuum maps. Despite a HyLIRG luminosity, the FIR continuum shape resembles that of a local LIRG. We simultaneously fit all of the observed spectral line profiles, finding four components which correspond cleanly to discrete spatial structures identified in the maps. The two most redshifted spectral components occupy the nucleus of a massive galaxy, with a source plane separation <1 kpc. The reddest dominates the continuum map (de-magnified L_FIR = (1.1$pm$0.2)x10^13 L_sun), and excites strong water emission in both nuclear components via a powerful FIR radiation field from the intense star formation. A third star-forming component is most likely a region of a merging companion (dV ~ 500 km/s) exhibiting generally similar gas properties. The bluest component originates from a spatially distinct region, and photo-dissociation region (PDR) analysis suggests that it is lower density, cooler and forming stars less vigorously than the other components. Strikingly, it has very strong [NII] emission which may suggest an ionized, molecular outflow. This comprehensive view of gas properties and morphology in HLS0918 previews the science possible for a large sample of high-redshift galaxies once ALMA attains full sensitivity.
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.
We report the results of a pilot study with the EVLA of 12CO J=1-0 emission from four SMGs at z=2.2-2.5, each with an existing detection of CO J=3-2. Using the EVLAs most compact configuration we detect strong, broad J=1-0 line emission from all of our targets. The median line width ratio, sigma(1-0)/sigma(3-2) = 1.15 +/- 0.06, suggests that the J=1-0 is more spatially extended than the J=3-2 emission, a situation confirmed by our maps which reveal velocity structure in several cases and typical sizes of ~16 kpc FWHM. The median Tb ratio is r(3-2/1-0) = 0.55 +/- 0.05, noting that our value may be biased high because of the J=3-2-based sample selection. Naively, this suggests gas masses ~2x higher than estimates made using higher-J transitions of CO, with the discrepency due to the difference in assumed Tb ratio. We also estimate masses using the 12CO J=1-0 line and the observed global Tb ratios, assuming standard underlying Tb ratios as well as a limiting SFE, i.e. without calling upon X(CO). Using this new method, we find a median molecular gas mass of (2.5 +/- 0.8) x 10^10 Msun, with a plausible range stretching 3x higher. Even larger masses cannot be ruled out, but are not favoured by dynamical constraints: the median dynamical mass for our sample is (2.3 +/- 1.4) x 10^11 Msun. We examine the Schmidt-Kennicutt relation for all the distant galaxy populations for which CO J=1-0 or J=2-1 data are available, finding small systematic differences. These have previously been interpreted as evidence for different modes of star formation, but we argue that these differences are to be expected, given the still considerable uncertainties. Finally, we discuss the morass of degeneracies surrounding molecular gas mass estimates, the possibilities for breaking them, and the future prospects for imaging and studying cold, quiescent molecular gas at high redshifts [abridged].
The analysis of optical images of galaxy-galaxy strong gravitational lensing systems can provide important information about the distribution of dark matter at small scales. However, the modeling and statistical analysis of these images is extraordinarily complex, bringing together source image and main lens reconstruction, hyper-parameter optimization, and the marginalization over small-scale structure realizations. We present here a new analysis pipeline that tackles these diverse challenges by bringing together many recent machine learning developments in one coherent approach, including variational inference, Gaussian processes, differentiable probabilistic programming, and neural likelihood-to-evidence ratio estimation. Our pipeline enables: (a) fast reconstruction of the source image and lens mass distribution, (b) variational estimation of uncertainties, (c) efficient optimization of source regularization and other hyperparameters, and (d) marginalization over stochastic model components like the distribution of substructure. We present here preliminary results that demonstrate the validity of our approach.
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.
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