Molecular clouds in the Carina arm - Large-scale properties of molecular gas and comparison with H I

1987 ◽  
Vol 315 ◽  
pp. 122 ◽  
Author(s):  
D. A. Grabelsky ◽  
R. S. Cohen ◽  
L. Bronfman ◽  
P. Thaddeus ◽  
J. May
Keyword(s):  
Molecular Clouds ◽  
Large Scale ◽  
Molecular Gas ◽  
Scale Properties

The magnetic evolution of the Taurus molecular clouds. I - Large-scale properties

1987 ◽  
Vol 321 ◽  
pp. 855 ◽  
Author(s):  
Mark H. Heyer ◽  
Frederick J. Vrba ◽  
Ronald L. Snell ◽  
F. P. Schloerb ◽  
Stephen E. Strom ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Large Scale ◽  
Scale Properties

scholarly journals The headlight cloud in NGC 628: An extreme giant molecular cloud in a typical galaxy disk

2020 ◽  
Vol 634 ◽  
pp. A121 ◽  
Author(s):  
Cinthya N. Herrera ◽  
Jérôme Pety ◽  
Annie Hughes ◽  
Sharon E. Meidt ◽  
Kathryn Kreckel ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Stellar Population ◽  
High Mass ◽  
Molecular Gas ◽  
Giant Molecular Cloud ◽  
The Impact

Context. Cloud-scale surveys of molecular gas reveal the link between giant molecular cloud properties and star formation across a range of galactic environments. Cloud populations in galaxy disks are considered to be representative of the normal star formation process, while galaxy centers tend to harbor denser gas that exhibits more extreme star formation. At high resolution, however, molecular clouds with exceptional gas properties and star formation activity may also be observed in normal disk environments. In this paper we study the brightest cloud traced in CO(2–1) emission in the disk of nearby spiral galaxy NGC 628. Aims. We characterize the properties of the molecular and ionized gas that is spatially coincident with an extremely bright H II region in the context of the NGC 628 galactic environment. We investigate how feedback and large-scale processes influence the properties of the molecular gas in this region. Methods. High-resolution ALMA observations of CO(2–1) and CO(1−0) emission were used to characterize the mass and dynamical state of the “headlight” molecular cloud. The characteristics of this cloud are compared to the typical properties of molecular clouds in NGC 628. A simple large velocity gradient (LVG) analysis incorporating additional ALMA observations of 13CO(1−0), HCO+(1−0), and HCN(1−0) emission was used to constrain the beam-diluted density and temperature of the molecular gas. We analyzed the MUSE spectrum using Starburst99 to characterize the young stellar population associated with the H II region. Results. The unusually bright headlight cloud is massive (1 − 2 × 107 M⊙), with a beam-diluted density of nH2 = 5 × 104 cm−3 based on LVG modeling. It has a low virial parameter, suggesting that the CO emission associated with this cloud may be overluminous due to heating by the H II region. A young (2 − 4 Myr) stellar population with mass 3 × 105 M⊙ is associated. Conclusions. We argue that the headlight cloud is currently being destroyed by feedback from young massive stars. Due to the large mass of the cloud, this phase of the its evolution is long enough for the impact of feedback on the excitation of the gas to be observed. The high mass of the headlight cloud may be related to its location at a spiral co-rotation radius, where gas experiences reduced galactic shear compared to other regions of the disk and receives a sustained inflow of gas that can promote the mass growth of the cloud.

scholarly journals CO (J=2-1) Observations of the Molecular Cloud Complex in the Galactic Center

1994 ◽  
Vol 140 ◽  
pp. 168-169
Author(s):  
Tomoharu Oka ◽  
Tetsuo Hasegawa ◽  
Masahiko Hayashi ◽  
Toshihiro Handa ◽  
Sei'ichi Sakamoto
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Center ◽  
Molecular Gas ◽  
Star Forming ◽  
Near Future ◽  
Cloud Complex ◽  
Mapping Observation

AbstractWe report a large scale mapping observation of the Galactic center region in the CO (J=2-1) line using the Tokyo-NRO 60cm survey telescope. Distribution of the CO (J=2-1) emission in the I-V plane suggests that molecular clouds forms a huge complex (Nuclear Molecular cloud Complex, NMC). Tracers of star formation activities in the last 106-108 years show that star formation has occured in a ring ~ 100 pc in radius. Relative to this Star Forming Ring, the molecular gas is distributed mainly on the positive longitude side. This may indicate that much of the gas in NMC is in transient orbit to fall into the star forming ring or to the nucleus in the near future.

scholarly journals Large-Scale Molecular Gas Survey in 12CO, 13CO and C18O (J = 2–1) with the Osaka 1.85m mm-submm Telescope

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Toshikazu Onishi ◽  
Atsushi Nishimura ◽  
Kazuki Tokuda ◽  
Ryohei Harada ◽  
Kazuhito Dobashi ◽  
...  
Keyword(s):  
Physical Properties ◽  
Molecular Clouds ◽  
Large Scale ◽  
Molecular Gas ◽  
Beam Size ◽  
Radio Observatory ◽  
Target Frequency ◽  
Scientific Goal ◽  
The Galaxy ◽  
Scientific Results

AbstractWe have developed a new mm-submm telescope with a diameter of 1.85 m (hereafter, Osaka 1.85-m telescope) installed at the Nobeyama Radio Observatory. The scientific goal is to precisely reveal physical properties of molecular clouds in the Galaxy by obtaining a large-scale distribution of molecular gas, which also can be compared with large-scale observations in various wavelengths. The target frequency is ~230 GHz; simultaneous observations in J = 2–1 lines of 12CO, 13CO and C18O are achieved with a beam size (HPBW) of 2.7 arcmin. Here we present the progress of observations and the scientific results obtained by Osaka 1.85-m telescope. We note that these J = 2–1 data of the Galactic molecular clouds will be precious for the comparison with those of extra-galactic ones that will be obtained with the ALMA with the comparable spatial resolutions.

scholarly journals CHIMPS: physical properties of molecular clumps across the inner Galaxy

2019 ◽  
Vol 632 ◽  
pp. A58 ◽  
Author(s):  
A. J. Rigby ◽  
T. J. T. Moore ◽  
D. J. Eden ◽  
J. S. Urquhart ◽  
S. E. Ragan ◽  
...  
Keyword(s):  
Physical Properties ◽  
Molecular Clouds ◽  
Large Scale ◽  
Angular Resolution ◽  
Galactic Plane ◽  
Continuum Emission ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Excitation Temperature ◽  
Galactocentric Distance

The latest generation of high-angular-resolution unbiased Galactic plane surveys in molecular-gas tracers are enabling the interiors of molecular clouds to be studied across a range of environments. The CO Heterodyne Inner Milky Way Plane Survey (CHIMPS) simultaneously mapped a sector of the inner Galactic plane, within 27.8° ≲ ℓ ≲ 46.2° and |b|≤ 0°.5, in 13CO (3–2) and C18O (3–2) at an angular resolution of 15 arcsec. The combination of the CHIMPS data with 12CO (3–2) data from the CO High Resolution Survey (COHRS) has enabled us to perform a voxel-by-voxel local-thermodynamic-equilibrium (LTE) analysis, determining the excitation temperature, optical depth, and column density of 13CO at each ℓ, b, v position. Distances to discrete sources identified by FELLWALKER in the 13CO (3–2) emission maps were determined, allowing the calculation of numerous physical properties of the sources, and we present the first source catalogues in this paper. We find that, in terms of size and density, the CHIMPS sources represent an intermediate population between large-scale molecular clouds identified by CO and dense clumps seen in thermal dust continuum emission, and therefore represent the bulk transition from the diffuse to the dense phase of molecular gas. We do not find any significant systematic variations in the masses, column densities, virial parameters, mean excitation temperature, or the turbulent pressure over the range of Galactocentric distance probed, but we do find a shallow increase in the mean volume density with increasing Galactocentric distance. We find that inter-arm clumps have significantly narrower linewidths, and lower virial parameters and excitation temperatures than clumps located in spiral arms. When considering the most reliable distance-limited subsamples, the largest variations occur on the clump-to-clump scale, echoing similar recent studies that suggest that the star-forming process is largely insensitive to the Galactic-scale environment, at least within the inner disc.

scholarly journals On the structure and kinematics of molecular clouds from large scale mapping of mm-lines

1991 ◽  
Vol 147 ◽  
pp. 11-20
Author(s):  
J. Bally ◽  
W. D. Langer ◽  
R. W. Wilson ◽  
A. A. Stark ◽  
M. W. Pound
Keyword(s):  
Molecular Clouds ◽  
Large Scale ◽  
Massive Stars ◽  
Vital Role ◽  
Solar Neighborhood ◽  
Young Stellar Objects ◽  
Small Scale ◽  
Molecular Gas ◽  
Main Body ◽  
Stellar Objects

Molecular gas in the interior of the Orion superbubble consists of sheets, filaments, and partial shells in which the active star forming dense cloud cores are embedded. The main body of the Orion A and B clouds and at least 14 smaller clouds in Orion region are cometary in appearance suggesting strong interaction with massive stars in the Orion OB association. While the small scale (< 1 pc) structure of the clouds may be determined primarily by internal magnetic fields, gravity, and the effects of outflows from young stellar objects, the large scale morphology and kinematics is affected by the energy injected by massive stars. Supernovae, stellar winds, and radiation have compressed, accelerated, ablated, and dispersed molecular gas over the last 107 years. Most GMC/OB star complexes in the Solar neighborhood exhibit morphological and kinematic properties similar to the Orion region. We argue that energy injection by massive stars plays a vital role in the evolution of the ISM and may be responsible for much of the observed large-scale structure and kinematics of molecular clouds.

scholarly journals The Structure of Molecular Clouds from Large Scale Surveys of CO and CS

1989 ◽  
Vol 120 ◽  
pp. 308-314
Author(s):  
John Bally
Keyword(s):  
Kinetic Energy ◽  
Energy Budget ◽  
Strong Interaction ◽  
Molecular Clouds ◽  
Large Scale ◽  
Molecular Gas ◽  
Active Star ◽  
Star Forming ◽  
Line Widths ◽  
Cloud Cores

The molecular gas lying in the interior of the Orion superbubble consists of sheets, filaments and bubbles in which the dense active star forming cloud cores are embedded. Many regions have a wind-swept or cometary appearance suggesting strong interaction with the Orion OB association. External heating dominates the cloud energy budget, resulting in cold (˜10K) cloud cores surrounded by hot (>20K) envelopes. Non-ionizing UV radiation emitted by late B and A stars may be the source of the kinetic energy needed to form some of the large scale cavities and contributes to the supersonic line widths seen in many clouds.

scholarly journals Stochastic Star Formation and Magnetic Fields

1990 ◽  
Vol 140 ◽  
pp. 257-258
Author(s):  
J. V. Feitzinger ◽  
E. Harfst ◽  
J. Spicker
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Molecular Clouds ◽  
Large Scale ◽  
Spiral Structure ◽  
Galactic Plane ◽  
Molecular Gas ◽  
Cell Content ◽  
Star Forming ◽  
Flat Rotation Curves

The model of selfpropagating star formation uses local processes (200 pc cell size) in the interstellar medium to simulate the large scale cooperative behaviour of spiral structure in galaxies. The dynamic of the model galaxies is taken into account via the mass distribution and the resulting rotation curve; flat rotation curves are used. The interstellar medium is treated as a multiphase medium with appropriate cooling times and density history. The phases are: molecular gas, cool HI gas, warm intercloud and HII gas and hot coronal fountain gas. A detailed gas reshuffeling between the star forming cells in the plane and outside the galactic plane controls the cell content. Two processes working stochastically are incooperated: the building and the decay of molecular clouds and the star forming events in the molecular clouds.

scholarly journals Two New Views of the Galactic Center

1996 ◽  
Vol 169 ◽  
pp. 283-284 ◽  
Author(s):  
D.T. Jaffe ◽  
R. Plume ◽  
S. Pak
Keyword(s):  
Interstellar Medium ◽  
High Velocity ◽  
Molecular Clouds ◽  
Large Scale ◽  
Galactic Center ◽  
Molecular Gas ◽  
The Galaxy ◽  
Physical Effects ◽  
Velocity Dispersions ◽  
Internal Velocity

The inner few hundred parsecs of the Galactic Center contains ∼10% of the molecular ISM in the Galaxy. The conditions in this gas are significantly different from those in molecular clouds elsewhere in the Galaxy. Typical temperatures, densities, and internal velocity dispersions are higher (Güesten 1989). There is also evidence for a large amount of molecular gas which is not bound to distinct clouds (Stark et al. 1989). High velocity bulk gas motions and velocity discontinuities open up the possibility of a role for powerful large-scale shocks in ISM excitation. The very different nature of the dense ISM in the inner Galaxy make it useful as a laboratory for physical effects in the interstellar medium and a proving ground for ideas about the interaction of gas and stars in the nuclei of other galaxies.

scholarly journals On the structure and kinematics of molecular clouds from large scale mapping of mm-lines

1991 ◽  
Vol 147 ◽  
pp. 11-20
Author(s):  
J. Bally ◽  
W. D. Langer ◽  
R. W. Wilson ◽  
A. A. Stark ◽  
M. W. Pound
Keyword(s):  
Molecular Clouds ◽  
Large Scale ◽  
Massive Stars ◽  
Vital Role ◽  
Solar Neighborhood ◽  
Young Stellar Objects ◽  
Small Scale ◽  
Molecular Gas ◽  
Main Body ◽  
Stellar Objects

Molecular gas in the interior of the Orion superbubble consists of sheets, filaments, and partial shells in which the active star forming dense cloud cores are embedded. The main body of the Orion A and B clouds and at least 14 smaller clouds in Orion region are cometary in appearance suggesting strong interaction with massive stars in the Orion OB association. While the small scale (< 1 pc) structure of the clouds may be determined primarily by internal magnetic fields, gravity, and the effects of outflows from young stellar objects, the large scale morphology and kinematics is affected by the energy injected by massive stars. Supernovae, stellar winds, and radiation have compressed, accelerated, ablated, and dispersed molecular gas over the last 107 years. Most GMC/OB star complexes in the Solar neighborhood exhibit morphological and kinematic properties similar to the Orion region. We argue that energy injection by massive stars plays a vital role in the evolution of the ISM and may be responsible for much of the observed large-scale structure and kinematics of molecular clouds.

Sign in / Sign up

Export Citation Format

Share Document