https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34949 1,6–5_2,3 maser line at 22.235 GHz, and several other molecular lines. We present a representative portion of the data from the pilot survey, including NH₃(1,1) and NH₃(2,2) integrated intensity maps, H₂O maser positions, maps of NH₃ velocity, NH₃ line width, total NH₃ column density, and NH₃ rotational temperature. These data and the data cubes from which they were produced are publicly available on the RAMPS website (http://sites.bu.edu/ramps/).]]> Tue 03 Sep 2019 18:17:26 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34924 10⁴ M_⊙), remains an open problem, largely because they are so rare that examples of their cold, dense, molecular progenitors continue to be elusive. The molecular cloud G337.342−0.119, the "Pebble," is a candidate cold progenitor. Although G337.342−0.119 was originally identified as four separate ATLASGAL clumps, the similarities in their molecular line velocities and line widths in the MALT90 data set demonstrate that these four clumps are in fact one single, coherent cloud. This cloud is unique in the MALT90 survey for its combination of both cold temperatures (T _dust ~ 14 K) and large line widths (ΔV ~ 10 km s−1). The near/far kinematic distance ambiguity is difficult to resolve for G337.342−0.119. At the near kinematic distance (4.7 kpc), the mass is 5000 M_⊙ and the size is 7 × 2 pc. At the far kinematic distance (11 kpc), the mass is 27,000 M_⊙ and the size is 15 × 4 pc. The unusually large line widths of G337.342−0.119 are difficult to reconcile with a gravitationally bound system in equilibrium. If our current understanding of the Galaxy's Long Bar is approximately correct, G337.342−0.119 cannot be located at its end. Rather, it is associated with a large star-forming complex that contains multiple clumps with large line widths. If G337.342−0.119 is a prototypical cold progenitor for a high-mass cluster, its properties may indicate that the onset of high-mass star cluster formation is dominated by extreme turbulence.]]> Tue 03 Sep 2019 17:58:48 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34944 + (1–0) line for the "blue asymmetry" spectroscopic signature of infall motion in a large sample of high-mass, dense molecular clumps observed to be at different evolutionary stages of star cluster formation according to their mid-infrared appearance. To quantify the degree of the line asymmetry, we measure the asymmetry parameter A=[formula could not be replicated], the fraction of the integrated intensity that lies to the blueshifted side of the systemic velocity determined from the optically thin tracer N₂H⁺ (1–0). For a sample of 1093 sources, both the mean and median of A are positive (A=0.0830 ± 010 and 0.065 ± 0.009, respectively) with high statistical significance, and a majority of sources (a fraction of 0.607 ± 0.015 of the sample) show positive values of A, indicating a preponderance of blue asymmetric profiles over red asymmetric profiles. Two other measures, the local slope of the line at the systemic velocity and the δv parameter of Mardones et al. (1997), also show an overall blue asymmetry for the sample, but with smaller statistical significance. This blue asymmetry indicates that these high-mass clumps are predominantly undergoing gravitational collapse. The blue asymmetry is larger (A ∼ 0.12) for the earliest evolutionary stages (quiescent, protostellar, and compact H ii region) than for the later H ii region (A ∼ 0.06) and photodissociation region (A ∼ 0) classifications.]]> Tue 03 Sep 2019 17:57:00 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34952 ⊙), cold (14 K) 3.6–70 μm dark IRDC, G331.372-00.116. This infrared dark cloud (IRDC) has the potential to form high-mass stars, and given the absence of current star formation signatures, it seems to represent the earliest stages of high-mass star formation. We have mapped the whole IRDC with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.1 and 1.3 mm in dust continuum and line emission. The dust continuum reveals 22 cores distributed across the IRDC. In this work, we analyze the physical properties of the most massive core, ALMA1, which has no molecular outflows detected in the CO (2–1), SiO (5–4), and H₂CO (3–2) lines. This core is relatively massive (M = 17.6 M _⊙), subvirialized (virial parameter α _vir = M_vir/M = 0.14), and is barely affected by turbulence (transonic Mach number of 1.2). Using the HCO⁺ (3–2) line, we find the first detection of infall signatures in a relatively massive, prestellar core (ALMA1) with the potential to form a high-mass star. We estimate an infall speed of 1.54 km s⁻¹ and a high accretion rate of 1.96 × 10⁻³ M _⊙ yr⁻¹. ALMA1 is rapidly collapsing, out of virial equilibrium, which is more consistent with competitive accretion scenarios rather than the turbulent core accretion model. On the other hand, ALMA1 has a mass ~6 times larger than the clumps Jeans mass, as it is in an intermediate mass regime (M_J = 2.7 ⊙), contrary to what both the competitive accretion and turbulent core accretion theories predict.]]> Tue 03 Sep 2019 17:56:50 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34953 Tue 03 Sep 2019 17:56:40 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45526 J = 4(0, 4) − 3(0, 3) data at 3 mm, using two new pieces of software that we make available to the community. First, SCOUSEPY, a Python implementation of the spectral line fitting algorithm SCOUSE. Secondly, ACORNS (Agglomerative Clustering for ORganising Nested Structures), a hierarchical n-dimensional clustering algorithm designed for use with discrete spectroscopic data. Together, these tools provide an unbiased measurement of the line-of-sight velocity dispersion in this cloud, σ_vlos,1D=4.4±2.1 km s⁻¹, which is somewhat larger than predicted by velocity dispersion-size relations for the central molecular zone (CMZ). The dispersion of centroid velocities in the plane of the sky are comparable, yielding σ_vlos,1D/σ_vpos,1D∼1.2±0.3⁠. This isotropy may indicate that the line-of-sight extent of the cloud is approximately equivalent to that in the plane of the sky. Combining our kinematic decomposition with radiative transfer modelling, we conclude that G0.253+0.016 is not a single, coherent, and centrally condensed molecular cloud; ‘the Brick’ is not a brick. Instead, G0.253+0.016 is a dynamically complex and hierarchically structured molecular cloud whose morphology is consistent with the influence of the orbital dynamics and shear in the CMZ.]]> Thu 03 Nov 2022 12:56:08 AEDT ]]>