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 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 The global star formation law: from dense cores to extreme starbursts

2006 ◽  
Vol 2 (S237) ◽  
pp. 331-335
Author(s):  
Yu Gao
Keyword(s):  
Star Formation ◽  
Linear Correlation ◽  
Molecular Clouds ◽  
High Redshift ◽  
Gas Content ◽  
Molecular Gas ◽  
Giant Molecular Clouds ◽  
Active Star ◽  
Dense Cores ◽  
The Galaxy

AbstractActive star formation (SF) is tightly related to the dense molecular gas in the giant molecular clouds' dense cores. Our HCN (measure of the dense molecular gas) survey in 65 galaxies (including 10 ultraluminous galaxies) reveals a tight linear correlation between HCN and IR (SF rate) luminosities, whereas the correlation between IR and CO (measure of the total molecular gas) luminosities is nonlinear. This suggests that the global SF rate depends more intimately upon the amount of dense molecular gas than the total molecular gas content. This linear relationship extends to both the dense cores in the Galaxy and the hyperluminous extreme starbursts at high-redshift. Therefore, the global SF law in dense gas appears to be linear all the way from dense cores to extreme starbursts, spanning over nine orders of magnitude in IR luminosity.

scholarly journals Bipolar Outflows and Stellar Jets

1987 ◽  
Vol 115 ◽  
pp. 213-237 ◽  
Author(s):  
Ronald L. Snell
Keyword(s):  
Physical Properties ◽  
High Velocity ◽  
Molecular Clouds ◽  
Early Stage ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
Bipolar Outflows ◽  
Stellar Objects ◽  
Stellar Jets ◽  
Almost All

A wealth of data is now available on the energetic mass outflows that are associated with young stellar objects. This phenomenon is thought to occur at a very early stage in the evolution of stars of almost all masses. The discovery of this energetic event was first made through observations of the rapidly expanding molecular gas that surrounds many of these young stellar objects. A review of the physical properties, including the energetics and morphology, of the expanding molecular gas is presented in this paper. In addition, the role these energetic winds play in affecting the dynamics of the parental molecular clouds is also discussed. Finally, the results of detailed studies of the structure and kinematics of the high velocity molecular gas are reviewed and the evidence for existance of wind-swept cavities and molecular shells within the clouds are presented.

scholarly journals Simulations of the star-forming molecular gas in an interacting M51-like galaxy

2020 ◽  
Vol 492 (2) ◽  
pp. 2973-2995 ◽  
Author(s):  
Robin G Tress ◽  
Rowan J Smith ◽  
Mattia C Sormani ◽  
Simon C O Glover ◽  
Ralf S Klessen ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Formation Rate ◽  
Three Dimensional ◽  
Molecular Gas ◽  
Secondary Importance ◽  
Star Forming ◽  
The Galaxy ◽  
Cold Star ◽  
Self Gravity

ABSTRACT We present here the first of a series of papers aimed at better understanding the evolution and properties of giant molecular clouds (GMCs) in a galactic context. We perform high-resolution, three-dimensional arepo simulations of an interacting galaxy inspired by the well-observed M51 galaxy. Our fiducial simulations include a non-equilibrium, time-dependent, chemical network that follows the evolution of atomic and molecular hydrogen as well as carbon and oxygen self-consistently. Our calculations also treat gas self-gravity and subsequent star formation (described by sink particles), and coupled supernova feedback. In the densest parts of the simulated interstellar medium (ISM), we reach sub-parsec resolution, granting us the ability to resolve individual GMCs and their formation and destruction self-consistently throughout the galaxy. In this initial work, we focus on the general properties of the ISM with a particular focus on the cold star-forming gas. We discuss the role of the interaction with the companion galaxy in generating cold molecular gas and controlling stellar birth. We find that while the interaction drives large-scale gas flows and induces spiral arms in the galaxy, it is of secondary importance in determining gas fractions in the different ISM phases and the overall star formation rate. The behaviour of the gas on small GMC scales instead is mostly controlled by the self-regulating property of the ISM driven by coupled feedback.

scholarly journals Methanol at the Edge of the Galaxy: New Observations to Constrain the Galactic Habitable Zone

2021 ◽  
Vol 922 (2) ◽  
pp. 106
Author(s):  
J. J. Bernal ◽  
C. D. Sephus ◽  
L. M. Ziurys
Keyword(s):  
Molecular Clouds ◽  
Organic Molecules ◽  
Galactic Center ◽  
Solar Neighborhood ◽  
Habitable Zone ◽  
Line Profiles ◽  
Galactocentric Distance ◽  
Radio Observatory ◽  
The Galaxy ◽  
Co Observations

Abstract The Galactic Habitable Zone (GHZ) is a region believed hospitable for life. To further constrain the GHZ, observations have been conducted of the J = 2 → 1 transitions of methanol (CH3OH) at 97 GHz, toward 20 molecular clouds located in the outer Galaxy (R GC = 12.9–23.5 kpc), using the 12 m telescope of the Arizona Radio Observatory. Methanol was detected in 19 out of 20 observed clouds, including sources as far as R GC = 23.5 kpc. Identification was secured by the measurement of multiple asymmetry and torsional components in the J = 2 → 1 transition, which were resolved in the narrow line profiles observed (ΔV 1/2 ∼ 1–3 km s−1). From a radiative transfer analysis, column densities for these clouds of N tot = 0.1–1.5 × 1013 cm−2 were derived, corresponding to fractional abundances, relative to H2, of f (CH3OH) ∼ 0.2–4.9 × 10−9. The analysis also indicates that these clouds are cold (T K ∼ 10–25 K) and dense (n(H2) ∼ 106 cm−3), as found from previous H2CO observations. The methanol abundances in the outer Galaxy are comparable to those observed in colder molecular clouds in the solar neighborhood. The abundance of CH3OH therefore does not appear to decrease significantly with distances from the Galactic Center, even at R GC ∼ 20–23 kpc. Furthermore, the production of methanol is apparently not affected by the decline in metallicity with galactocentric distance. These observations suggest that organic chemistry is prevalent in the outer Galaxy, and methanol and other organic molecules may serve to assess the GHZ.

scholarly journals Molecular Line Observations of the Galactic Center Region

1989 ◽  
Vol 136 ◽  
pp. 129-133 ◽  
Author(s):  
A. A. Stark ◽  
J. Bally ◽  
R. W. Wilson ◽  
M. W. Pound
Keyword(s):  
Molecular Clouds ◽  
Virial Theorem ◽  
Galactic Center ◽  
Galactic Disk ◽  
High Mass ◽  
Molecular Gas ◽  
Molecular Line ◽  
Center Region ◽  
The Galaxy ◽  
Cloud Medium

A decade of galactic center observations at the Crawford Hill 7 m antenna is summarized. The galactic center region contains several hundred high-mass, high-density molecular clouds with physical properties very different from clouds in the outer galactic disk. There is also a considerable amount of molecular gas not bound into clouds, but sheared by differential rotation into a molecular inter-cloud medium not seen elsewhere in the Galaxy. These observations can be explained by a combination of the tidal density limit and the virial theorem. The distribution of emission on the sky and in velocity suggests that most of the dense gas is confined to a 500 pc long ridge of emission which may be a dust lane along the central bar.

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.

Constraining Baryons in the M31 galactic halo by Planck data

2019 ◽  
Vol 28 (07) ◽  
pp. 1950088 ◽  
Author(s):  
Noraiz Tahir ◽  
Francesco De Paolis ◽  
Asghar Qadir ◽  
Achille Nucita
Keyword(s):  
Physical Properties ◽  
Molecular Clouds ◽  
Galactic Halo ◽  
Molecular Gas ◽  
Galactic Halos ◽  
Planck Data ◽  
Nearby Galaxies ◽  
Galaxy Halo ◽  
Difficult Subject

The rotation of galactic halos is a particularly difficult subject to be dealt with. It has been shown that CMB data toward nearby galaxies can be used to probe the galactic halo rotation and can be ascribed to cold molecular clouds populating the halos. We present some methods to study the physical properties and distribution of such molecular gas clouds in the M31 galaxy halo.

Sign in / Sign up

Export Citation Format

Share Document