CN line emission from the molecular clouds associated with S106 and and NGC 7538

1982 ◽  
Vol 258 ◽  
pp. 515 ◽  
Author(s):  
E. Churchwell ◽  
J. H. Bieging
Keyword(s):  
Molecular Clouds ◽  
Line Emission

scholarly journals Molecular clouds photoevaporation and FIR line emission

2017 ◽  
pp. stx180 ◽  
Author(s):  
L. Vallini ◽  
A. Ferrara ◽  
A. Pallottini ◽  
S. Gallerani
Keyword(s):  
Molecular Clouds ◽  
Line Emission

scholarly journals Understanding biases in measurements of molecular cloud kinematics using line emission

2020 ◽  
Vol 498 (2) ◽  
pp. 2440-2455
Author(s):  
Yuxuan (宇轩) Yuan (原) ◽  
Mark R Krumholz ◽  
Blakesley Burkhart
Keyword(s):  
Magnetic Field ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Velocity Dispersion ◽  
Signal To Noise Ratio ◽  
Line Emission ◽  
Molecular Line ◽  
Velocity Dispersions ◽  
Cloud Kinematics ◽  
Measurement Biases

ABSTRACT Molecular line observations using a variety of tracers are often used to investigate the kinematic structure of molecular clouds. However, measurements of cloud velocity dispersions with different lines, even in the same region, often yield inconsistent results. The reasons for this disagreement are not entirely clear, since molecular line observations are subject to a number of biases. In this paper, we untangle and investigate various factors that drive linewidth measurement biases by constructing synthetic position–position–velocity cubes for a variety of tracers from a suite of self-gravitating magnetohydrodynamic simulations of molecular clouds. We compare linewidths derived from synthetic observations of these data cubes to the true values in the simulations. We find that differences in linewidth as measured by different tracers are driven by a combination of density-dependent excitation, whereby tracers that are sensitive to higher densities sample smaller regions with smaller velocity dispersions, opacity broadening, especially for highly optically thick tracers such as CO, and finite resolution and sensitivity, which suppress the wings of emission lines. We find that, at fixed signal-to-noise ratio, three commonly used tracers, the J = 4 → 3 line of CO, the J = 1 → 0 line of C18O, and the (1,1) inversion transition of NH3, generally offer the best compromise between these competing biases, and produce estimates of the velocity dispersion that reflect the true kinematics of a molecular cloud to an accuracy of $\approx 10{{\ \rm per\ cent}}$ regardless of the cloud magnetic field strengths, evolutionary state, or orientations of the line of sight relative to the magnetic field. Tracers excited primarily in gas denser than that traced by NH3 tend to underestimate the true velocity dispersion by $\approx 20{{\ \rm per\ cent}}$ on average, while low-density tracers that are highly optically thick tend to have biases of comparable size in the opposite direction.

scholarly journals Enhanced UV radiation and dense clumps in the molecular outflow of Mrk 231

2020 ◽  
Vol 633 ◽  
pp. A163 ◽  
Author(s):  
Claudia Cicone ◽  
Roberto Maiolino ◽  
Susanne Aalto ◽  
Sebastien Muller ◽  
Chiara Feruglio
Keyword(s):  
Gas Phase ◽  
Uv Radiation ◽  
Molecular Clouds ◽  
Line Emission ◽  
Molecular Gas ◽  
Spectral Features ◽  
Giant Molecular Clouds ◽  
Dense Phase ◽  
Molecular Outflow ◽  
First Time

We present interferometric observations of the CN(1–0) line emission in Mrk 231 and combine them with previous observations of CO and other H2 gas tracers to study the physical properties of the massive molecular outflow. We find a strong boost of the CN/CO(1–0) line luminosity ratio in the outflow of Mrk 231, which is unprecedented compared to any other known Galactic or extragalactic astronomical source. For the dense gas phase in the outflow traced by the HCN and CN emissions, we infer XCN ≡ [CN]/[H2]> XHCN by at least a factor of three, with H2 gas densities of nH2 ∼ 105−6 cm−3. In addition, we resolve for the first time narrow spectral features in the HCN(1–0) and HCO+(1–0) high-velocity line wings tracing the dense phase of the outflow. The velocity dispersions of these spectral features, σv ∼ 7−20 km s−1, are consistent with those of massive extragalactic giant molecular clouds detected in nearby starburst nuclei. The H2 gas masses inferred from the HCN data are quite high, Mmol ∼ 0.3−5 × 108 M⊙. Our results suggest that massive complexes of denser molecular gas survive embedded into the more diffuse H2 phase of the outflow, and that the chemistry of these outflowing dense clouds is strongly affected by UV radiation.

Radio observations of molecules in the interstellar gas

1981 ◽  
Vol 303 (1480) ◽  
pp. 469-486 ◽  
Keyword(s):  
Molecular Clouds ◽  
Large Scale ◽  
Heavy Atom ◽  
Linear Chain ◽  
Angular Size ◽  
Line Emission ◽  
Spectral Lines ◽  
Interstellar Gas ◽  
Interstellar Molecules ◽  
Branched Chains

Radio astronomers have succeeded since 1968 in identifying nearly 50 molecules in the dense concentrations of the interstellar gas now generally termed molecular clouds. Most interstellar molecules are stable compounds familiar to the terrestrial chemist, but nearly one-fifth are ions, radicals and acetylenic carbon chains so reactive in the laboratory that before being detected in Space they had rarely been observed or were entirely unknown. The heavy atom backbone of the known interstellar molecules is a linear chain of C, N, O or S (Si is found in two diatomic molecules) ; rings and branched chains are missing. The most readily observed spectral lines of most interstellar molecules are rotational transitions at millimetre wavelengths. These are generally excited by H 2 collisions, and depending on the H 2 number density, the levels can be either in rotational equilibrium, or far from it. Maser line emission from OH, H 2 0 , SiO and CH 3 OH - extremely intense, small sources typically much less than 1" in angular size, often polarized and sometimes time-dependent - are the most striking examples of nonequilibrium excitation. A number of rare isotopic species are observed in interstellar molecules, those ol C, N and O having been studied the most intensively. Isotopic ratios differing from those on Earth by two- or threefold apparently exist, and in all but one case can be attributed to stellar nucleosynthesis since the formation of the Solar System. Molecular clouds apparently constitute an appreciable fraction of the interstellar medium by mass and are the largest reservoir of matter in Nature subject to the chemical bond. They are of great astronomical interest because of their central role in star formation and galactic structure: it is possible that all stars form in molecular clouds, and as molecular clouds are largely restricted to the spiral arms, they provide a new and highly specific tracer of the large-scale structure of the galactic system.

scholarly journals Origin of 6.4 keV Line Emission from Molecular Clouds in the Galactic Center

2009 ◽  
Vol 61 (4) ◽  
pp. 901-907 ◽  
Author(s):  
Vladimir Dogiel ◽  
Kwong-Sang Cheng ◽  
Dmitrii Chernyshov ◽  
Aya Bamba ◽  
Atsushi Ichimura ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Line Emission

scholarly journals Extragalactic science with ALMA

2011 ◽  
Vol 7 (S284) ◽  
pp. 494-495
Author(s):  
George J. Bendo ◽  
Keyword(s):  
Molecular Clouds ◽  
High Redshift ◽  
Atacama Desert ◽  
Line Emission ◽  
Continuum Emission ◽  
Synchrotron Emission ◽  
Molecular Line ◽  
Molecular Lines ◽  
Nearby Galaxies ◽  
Detailed Imaging

AbstractThe Atacama Large Millimeter/submillimeter Array (ALMA) is a telescope comprising 66 antennas that is located in the Atacama Desert in Chile, one of the driest locations on Earth. When the telescope is fully operational, it will perform observations over ten receiver bands at wavelengths from 9.5-0.32 mm (31-950 GHz) with unprecedented sensitivities to continuum emission from cold (<20 K) dust, Bremsstrahlung, and synchrotron emission as well as submillimetre and millimetre molecular lines. With baselines out to 16km and dynamic reconfiguration, ALMA will achieve spatial resolutions ranging from 3″ to 0.010″, allowing for detailed imaging of continuum or molecular line emission from 0.1-1 kpc scale gas and dust discs in high-redshift sources or 10-100 pc scale molecular clouds and substructures within nearby galaxies. Science observations started on 30 September 2011 with 16 antennas and four receiver bands on baselines up to 400 m. The telescope's capabilities will steadily improve until full operations begin in 2013.

scholarly journals Radio emission during the formation of stellar clusters in M 33

2020 ◽  
Vol 639 ◽  
pp. A27
Author(s):  
Edvige Corbelli ◽  
Jonathan Braine ◽  
Fatemeh S. Tabatabaei
Keyword(s):  
Radio Emission ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Supernova Remnants ◽  
Line Emission ◽  
Radio Continuum ◽  
Stellar Clusters ◽  
Nonthermal Radio ◽  
Early Formation ◽  
5 Ghz

Aims. We investigate thermal and nonthermal radio emission associated with the early formation and evolution phases of young stellar clusters (YSCs) selected by their mid-infrared (MIR) emission at 24 μm in M 33. We consider regions in their early formation period, which are compact and totally embedded in the molecular cloud, and in the more evolved and exposed phase. Methods. Thanks to recent radio continuum surveys between 1.4 and 6.3 GHz we are able to find radio source counterparts to more than 300 star forming regions of M 33. We identify the thermal free–free component for YSCs and their associated molecular complexes using the Hα line emission. Results. A cross-correlation of MIR and radio continuum is established from bright to very faint sources, with the MIR-to-radio emission ratio that shows a slow radial decline throughout the M 33 disk. We confirm the nature of candidate embedded sources by recovering the associated faint radio continuum luminosities. By selecting exposed YSCs with reliable Hα flux, we establish and discuss the tight relation between Hα and the total radio continuum at 5 GHz over four orders of magnitude. This holds for individual YSCs as well as for the giant molecular clouds hosting them, and allows us to calibrate the radio continuum–star formation rate relation at small scales. On average, about half of the radio emission at 5 GHz in YSCs is nonthermal with large scatter. For exposed but compact YSCs and their molecular clouds, the nonthermal radio continuum fraction increases with source brightness, while for large HII regions the nonthermal fraction is lower and shows no clear trend. This has been found for YSCs with and without identified supernova remnants and underlines the possible role of massive stars in triggering particle acceleration through winds and shocks: these particles diffuse throughout the native molecular cloud prior to cloud dispersal.

CO(J = 1-0) line emission from giant molecular clouds

1993 ◽  
Vol 402 ◽  
pp. 195 ◽  
Author(s):  
Mark G. Wolfire ◽  
David Hollenbach ◽  
A. G. G. M. Tielens
Keyword(s):  
Molecular Clouds ◽  
Line Emission ◽  
Giant Molecular Clouds

The Orion Molecular Clouds OMC‐1 and OMC‐2 Mapped in the Far‐Infrared Fine‐Structure Line Emission of C+and O0

1997 ◽  
Vol 481 (1) ◽  
pp. 343-354 ◽  
Author(s):  
F. Herrmann ◽  
S. C. Madden ◽  
T. Nikola ◽  
A. Poglitsch ◽  
R. Timmermann ◽  
...  
Keyword(s):  
Fine Structure ◽  
Molecular Clouds ◽  
Line Emission ◽  
Far Infrared ◽  
Structure Line
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