Analysis of Hydrogen Cyanide Hyperfine Spectral Components towards Star Forming Cores

Although hydrogen cyanide has become quite a common molecular tracing species for a variety of astrophysical sources, it, however, exhibits dramatic non-LTE behaviour in its hyperfine line structure. Individual hyperfine components can be strongly boosted or suppressed. If these so-called hyperfine line anomalies are present in the HCN rotational spectra towards low or high mass cores, this will affect the interpretation of various physical properties such as the line opacity and excitation temperature in the case of low mass objects and infall velocities in the case of their higher mass counterparts. This is as a consequence of the direct effects that anomalies have on the underlying line shape, be it with the line structural width or through the inferred line strength. This work involves the first observational investigation of these anomalies in two HCN rotational transitions, J=1!0 and J=3!2, towards both low mass starless cores and high mass protostellar objects. The degree of anomaly in these two rotational transitions is considered by computing the ratios of neighboring hyperfine lines in individual spectra. Results indicate some degree of anomaly is present in all cores considered in our survey, the most likely cause being line overlap effects among hyperfine components in higher rotational transitions.Comment: 8th Serbian Conference on Spectral Line Shapes in Astrophysics, Divicibare; 8 pages, 5 figure

Meeting Report of the Third Annual Tri-Service Microbiome Consortium Symposium

The Tri-Service Microbiome Consortium (TSMC) was founded to enhance collaboration, coordination, and communication of microbiome research among U.S. Department of Defense (DoD) organizations and to facilitate resource, material and information sharing among consortium members. The 2019 annual symposium was held 22–24 October 2019 at Wright-Patterson Air Force Base in Dayton, OH. Presentations and discussions centered on microbiome-related topics within five broad thematic areas: 1) human microbiomes; 2) transitioning products into Warfighter solutions; 3) environmental microbiomes; 4) engineering microbiomes; and 5) microbiome simulation and characterization. Collectively, the symposium provided an update on the scope of current DoD microbiome research efforts, highlighted innovative research being done in academia and industry that can be leveraged by the DoD, and fostered collaborative opportunities. This report summarizes the presentations and outcomes of the 3rd annual TSMC symposium

The Radio Ammonia Mid-plane Survey (RAMPS) Pilot Survey

The Radio Ammonia Mid-Plane Survey (RAMPS) is a molecular line survey that aims to map a portion of the Galactic midplane in the first quadrant of the Galaxy (l = 10°–40°, | b| \leqslant 0\buildrel{\circ}\over{.} 4) using the Green Bank Telescope. We present results from the pilot survey, which has mapped approximately 6.5 square degrees in fields centered at l = 10°, 23°, 24°, 28°, 29°, 30°, 31°, 38°, 45°, and 47°. RAMPS observes the NH3 inversion transitions NH3(1,1)–(5,5), the H2O 61,6–52,3 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/)

Hierarchical gravitational fragmentation. I. Collapsing cores within collapsing clouds

The Hierarchical Gravitational Fragmentation scenario is investigated through numerical simulations of the prestellar stages of the collapse of a marginally gravitationally unstable isothermal sphere immersed in a strongly gravitationally unstable, uniform background medium. The core developes a Bonnor–Ebert (BE)-like density profile, while at the time of singularity (the protostar) formation the envelope approaches a singular-isothermal sphere (SIS)-like r^−2 density profile. However, these structures are never hydrostatic. In this case, the central flat region is characterized by an infall speed linear with radius, while the envelope is characterized by a uniform infall speed. This implies that the hydrostatic SIS initial condition leading to Shuʼs classical inside-out solution is not expected to occur, and therefore neither should the inside-out solution. Instead, the solution collapses from the outside-in, naturally explaining the observation of extended infall velocities. The core, defined by the radius at which it merges with the background, has time-variable mass and radius, and evolves along the locus of the ensemble of observed prestellar cores in a plot of Mcore/MBE versus Mcore, spanning the range from the “stable” to the “unstable” regimes, even though it is collapsing at all times. We conclude that the presence of an unstable background allows a core to evolve dynamically from the time when it first appears, even when it resembles a pressure-confined, stable BE-sphere. The core can be thought of as a ram-pressure confined BE-sphere, with an increasing mass due to the accretion from the unstable background