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Although surveys of infall motions in dense cores have been carried out for years, few surveys have focused on mapping infall across cores using multiple spectral line observations. To fill this gap, we present IRAM 30-m Telescope maps of…

We develop an analytic model of thermal state-to-state rotationally inelastic collisions of asymmetric-top molecules with closed-shell atoms in electric fields, and apply it to the Ar--H$_2$O collision system. The predicted cross sections…

Chemical Physics · Physics 2010-01-05 Mikhail Lemeshko , Bretislav Friedrich

Resonance lines encode rich information about astrophysical sources and their environments, yet fully analytic treatments of multi-line radiative transfer remain almost entirely unexplored. We present exact, closed-form solutions for…

Astrophysics of Galaxies · Physics 2026-02-18 Ethan Stace , Aaron Smith , Kevin Lorinc , Olof Nebrin

We explore millimeter line diagnostics of an obscuring molecular torus modeled by a hydrodynamic simulation with three-dimensional nonLTE radiative transfer calculations. Based on the results of high-resolution hydrodynamic simulation of…

Astrophysics · Physics 2009-11-13 Masako Yamada , Keiichi Wada , Kohji Tomisaka

Observations of dark cloud cores have been carried out in the mid-infrared using ISOCAM and in the far-infrared using ISOPHOT, both aboard the Infrared Space Observatory. The cores are in most cases detected in emission at 200 and 170…

Astrophysics · Physics 2007-05-23 Aurore Bacmann , Philippe Andre , Derek Ward-Thompson

We present a numerical method and computer code to calculate the radiative transfer and excitation of molecular lines. Formulating the Monte Carlo method from the viewpoint of cells rather than photons allows us to separate local and…

Astrophysics · Physics 2007-05-23 Michiel R. Hogerheijde , Floris F. S. van der Tak

This paper presents results from modelling 450 micron and 850 micron continuum and HCO+ line observations of three distinct cores of an infrared dark cloud (IRDC) directed toward the W51 GMC. In the sub-mm continuum these cores appear as…

Astrophysics · Physics 2009-11-11 C. W. Ormel , R. F. Shipman , V. Ossenkopf , F. P. Helmich

This study explores the transitional characteristics of blue-core helicon discharge, which to our knowledge was not particularly focused on before. Parameters are measured on recently built advanced linear plasma device, i.e. Multiple…

[Abridged] We present a molecular survey of the starless cores L1498 and L1517B. These cores have been selected for their relative isolation and close-to-round shape, and they have been observed in a number of lines of 13 molecular species…

Astrophysics · Physics 2009-11-11 M. Tafalla , J. Santiago , P. C. Myers , P. Caselli , C. M. Walmsley , A. Crapsi

The HCN 1-0 hyperfine lines have been observed toward 24 young stellar objects (YSOs) of class 0 and I. We examined how their line shapes and velocity shifts vary along with their relative optical depths and compared them with those of CS…

Astrophysics · Physics 2009-10-31 Y. -S. Park , J. Kim , Y. C. Minh

The physical structure of hot molecular cores, where forming massive stars have heated up dense dust and gas, but have not yet ionized the molecules, poses a prominent challenge in the research of high-mass star formation and…

Astrophysics of Galaxies · Physics 2018-07-04 Rainer Rolffs , Peter Schilke , Qizhou Zhang , Luis Zapata

We present the results of a series of calculations studying the collapse of molecular cloud cores performed using a three-dimensional smoothed particle hydr odynamics code with radiative transfer in the flux-limited diffusion approximation.…

Astrophysics · Physics 2009-11-13 Stuart C. Whitehouse , Matthew R. Bate

We present the results of the first detailed millimeter and submillimeter molecular line survey of bright rimmed clouds, observed at FCRAO in the CO (J=1-0), C18O (J=1-0), HCO+ (J=1-0), H13CO+ (J=1-0), and N2H+ (J=1-0) transitions, and at…

Astrophysics · Physics 2009-11-07 Christopher H. De Vries , Gopal Narayanan , Ronald L. Snell

Gravitational collapse is fundamental to star formation, yet direct kinematic evidence of infall at the core scale in high-mass star-forming regions remains poorly constrained. We present the first large-scale statistical study of infall…

Astrophysics of Galaxies · Physics 2026-05-14 Kaho Morii , Patricio Sanhueza , Qizhou Zhang , James M. Jackson

We use state-of-the-art radiation-MHD simulations and 3D non-LTE radiative transfer computations to investigate \Halpha\ line formation in the solar chromosphere and apply the results of this investigation to develop the potential of…

Solar and Stellar Astrophysics · Physics 2015-06-04 Jorrit Leenaarts , Mats Carlsson , Luc Rouppe van der Voort

A plausible model is proposed for the enhancement of the abundance of molecular species in bipolar outflow sources. In this model, levels of HCO+ enhancement are considered based on previous chemical calculations, that are assumed to result…

Astrophysics · Physics 2009-11-10 J. M. C Rawlings , M. P. Redman , E. Keto , D. A. Williams

Using a Monte Carlo technique, we have developed a 3D lyman-alpha radiation transfer code allowing for prescribed arbitrary hydrogen density, ionisation, temperature structures, and dust distribution, and arbitrary velocity fields and UV…

Astrophysics · Physics 2009-11-11 Anne Verhamme , Daniel Schaerer , Antonella Maselli

[This is truncated to suit the whims of the archivers ...] Parameter studies in LVG models are used to show how the low-lying rotational transitions of common polar molecules HCO+, HCN and CS vary with number density, column density and…

Astrophysics of Galaxies · Physics 2015-06-03 H. S. Liszt

We present the results of an extensive observational study of the active star-forming complex W51 that was observed in the J=2-1 transition of the 12CO and 13CO molecules over a 1.25 deg x 1.00 deg region with the University of Arizona…

Astrophysics of Galaxies · Physics 2015-05-19 Miju Kang , John H. Bieging , Craig A. Kulesa , Youngung Lee , Minho Choi , William L. Peters

Forty molecular cloud cores in the southern hemisphere from the initial Spitzer Space Telescope Cores-to-Disks (c2d) Legacy program source list have been surveyed in 13CO(2-1), 12CO(4-3), and 12CO(7-6) with the Antarctic Submillimeter…

Astrophysics · Physics 2009-11-13 A. Loehr , T. L. Bourke , A. P. Lane , P. C. Myers , S. C. Parshley , A. A. Stark , N. F. H. Tothill