Hunt for variations in molecular gas and cloud properties across the inner, northern Galactic disk

1993 ◽  
Vol 411 ◽  
pp. 720 ◽  
Author(s):  
Harvey S. Liszt
Keyword(s):  
Galactic Disk ◽  
Molecular Gas ◽  
Cloud Properties

scholarly journals Cloud–cloud collisions in the common foot point of molecular loops 1 and 2 in the Galactic Center

2019 ◽  
Author(s):  
Rei Enokiya ◽  
Kazufumi Torii ◽  
Yasuo Fukui
Keyword(s):  
Star Formation ◽  
Galactic Center ◽  
Galactic Disk ◽  
Volume Density ◽  
High Mass ◽  
Molecular Gas ◽  
Large Area ◽  
Elapsed Time ◽  
The Common ◽  
First Time

Abstract Recent large-area, deep CO surveys in the Galactic disk have revealed the formation of ~50 high-mass stars or clusters triggered by cloud–cloud collisions (CCCs). Although the Galactic Center (GC)—which contains the highest volume density of molecular gas—is the most favorable place for cloud collisions, systematic studies of CCCs in that region are still untouched. Here we report for the first time evidence of CCCs in the common foot point of molecular loops 1 and 2 in the GC. We have investigated the distribution of molecular gas toward the foot point by using a methodology for identifying CCCs, and we have discovered clear signatures of CCCs. Using the estimated displacements and relative velocities of the clouds, we find the elapsed time since the beginnings of the collisions to be 105–106yr. We consider possible origins for previously reported peculiar velocity features in the foot point and discuss star formation triggered by CCCs in the GC.

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 A Vertical Structure of the Edge-On Galaxy, NGC 891

1994 ◽  
Vol 140 ◽  
pp. 361-362
Author(s):  
Toshihiro Handa ◽  
Yoshiaki Sofue ◽  
Satoru Ikeuchi ◽  
Sumio Ishizuki ◽  
Ryohei Kawabe
Keyword(s):  
Vertical Structure ◽  
Galactic Disk ◽  
Local Maximum ◽  
Major Axis ◽  
Field Of View ◽  
Molecular Gas ◽  
Standard Data ◽  
The Galaxy ◽  
Fisher Relation ◽  
Co Emission

Most of observational researches on molecular gas in galaxies have focused on the two-dimensional distributions in galactic disks so far. In order to investigate vertical structure of the galactic disk and the disk-halo interaction we need high-resolution observations of edge-on galaxies.So we observed the nearest edge-on galaxy, NGC 891, using the Nobeyama Millimeter Array (NMA). Its distance is estimated to be 8.9 Mpc using the Tully-Fisher relation and H-band photometric data. The synthesized beamsize was 4.5” x 4.4” and the field of view due to attenuation of the element antenna (Handa et al. 1992). The field center is 90”-offset from the center of the galaxy along the major axis toward the northern side, where the CO intensity has a local maximum (Sofue et al. 1987). After the standard data reduction procedure in AIPS, including CLEAN, we obtained 10 channel-maps with a 19.5 km s−1 velocity width from 289.8 km s−1 to 465.2 km s−1 with respect to the local standard of rest.In the integrated intensity map a narrow CO emission ridge is seen (Figure 1). It is an edge-on view of molecular gas disk of the galaxy. The confinement of the CO emission in the thin disk suggests that most of the molecular gas is belonging to the population-I objects like in our Galaxy. The apparent thickness of the ridge is about 7”, which means that the deconvolved width is about 6” or 270 pc (FWHM). The position-velocity diagram averaged along the major axis over the field of view shows no systematic velocity gradient along the minor axis (Figure 2). It means that the deconvolved thickness of the CO disk is intrinsic. This width is broader than that of our Galaxy by factor 2. The geometrically thick CO disk of NGC 891 may be due to active star formation in the disk.

Molecular Gas Cloud Properties and Star Formation in Dwarf Galaxies

2008 ◽  
pp. 93-96
Author(s):  
Alberto D. Bolatto ◽  
Adam K. Leroy ◽  
Fabian Walter ◽  
Leo Blitz ◽  
Erik Rosolowsky
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Molecular Gas ◽  
Cloud Properties ◽  
Gas Cloud

scholarly journals The Galactic Centre - a laboratory for starburst galaxies (?)

2011 ◽  
Vol 7 (S284) ◽  
pp. 371-378
Author(s):  
Roland M. Crocker
Keyword(s):  
Star Formation ◽  
Cosmic Rays ◽  
Gamma Ray ◽  
Galactic Disk ◽  
Starburst Galaxies ◽  
Radio Continuum ◽  
Galactic Centre ◽  
Molecular Gas ◽  
Thermal Activity ◽  
The Galaxy

AbstractThe Galactic centre – as the closest galactic nucleus – holds both intrinsic interest and possibly represents a useful analogue to starburst nuclei which we can observe with orders of magnitude finer detail than these external systems. The environmental conditions in the GC – here taken to mean the inner 200 pc in diameter of the Milky Way – are extreme with respect to those typically encountered in the Galactic disk. The energy densities of the various GC ISM components are typically ~two orders of magnitude larger than those found locally and the star-formation rate density ~three orders of magnitude larger. Unusually within the Galaxy, the Galactic centre exhibits hard-spectrum, diffuse TeV (=1012 eV) gamma-ray emission spatially coincident with the region's molecular gas. Recently the nuclei of local starburst galaxies NGC 253 and M82 have also been detected in gamma-rays of such energies. We have embarked on an extended campaign of modelling the broadband (radio continuum to TeV gamma-ray), non- thermal signals received from the inner 200 pc of the Galaxy. On the basis of this modelling we find that star-formation and associated supernova activity is the ultimate driver of the region's non-thermal activity. This activity drives a large-scale wind of hot plasma and cosmic rays out of the GC. The wind advects the locally-accelerated cosmic rays quickly, before they can lose much energy in situ or penetrate into the densest molecular gas cores where star-formation occurs. The cosmic rays can, however, heat/ionize the lower density/warm H2 phase enveloping the cores. On very large scales (~10 kpc) the non-thermal signature of the escaping GC cosmic rays has probably been detected recently as the spectacular ‘Fermi bubbles’ and corresponding ‘YWMAP haze’.

scholarly journals HCN AND HCO+EMISSION IN M31 : TRACING THE DENSE MOLECULAR GAS IN A GALACTIC DISK

2005 ◽  
Vol 38 (2) ◽  
pp. 245-248
Author(s):  
SEBASTIEN MULLER ◽  
NATHALIE BROUILLET ◽  
FABRICE HERPIN ◽  
JONATHAN BRAINE ◽  
THIERRY JACQ
Keyword(s):  
Galactic Disk ◽  
Molecular Gas

scholarly journals A Large-Scale CO Imaging of the Galactic Center

1998 ◽  
Vol 179 ◽  
pp. 189-190
Author(s):  
T. Oka ◽  
T. Hasegawa ◽  
F. Sato ◽  
H. Yamasaki ◽  
M. Tsuboi ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Center ◽  
Galactic Disk ◽  
Molecular Gas ◽  
Physical Conditions ◽  
Relative Paucity ◽  
Center Region ◽  
Star Formation Activity

Molecular gas in the Galactic center region is spatially and kinematically complex, and its physical conditions are distinctively different from those of molecular gas in the Galactic disk (e.g., Morris 1996). Relative paucity of current star formation activity, despite the abundance of dense molecular gas in this region, is one of the problem at issue.

scholarly journals Atomic carbon [C i](3P1–3P0) mapping of the nearby galaxy M 83

2021 ◽  
Author(s):  
Yusuke Miyamoto ◽  
Atsushi Yasuda ◽  
Yoshimasa Watanabe ◽  
Masumichi Seta ◽  
Nario Kuno ◽  
...  
Keyword(s):  
Galactic Disk ◽  
Abundance Ratio ◽  
Molecular Gas ◽  
Nearby Galaxy ◽  
Atomic Carbon ◽  
Single Temperature ◽  
Integrated Intensity ◽  
Spectrum Distribution ◽  
Good Tracer ◽  
Ir Emission

Abstract Atomic carbon (C i) has been proposed to be a global tracer of the molecular gas as a substitute for CO, however, its utility remains unproven. To evaluate the suitability of C i as the tracer, we performed [C i](3P1–3P0) [hereinafter [C i](1–0)] mapping observations of the northern part of the nearby spiral galaxy M 83 with the Atacama Submillimeter Telescope Experiment (ASTE) telescope and compared the distributions of [C i](1–0) with CO lines [CO(1–0), CO(3–2), and 13CO(1–0)], H i, and infrared (IR) emission (70, 160, and 250 μm). The [C i](1–0) distribution in the central region is similar to that of the CO lines, whereas [C i](1–0) in the arm region is distributed outside the CO. We examined the dust temperature, Tdust, and dust mass surface density, Σdust, by fitting the IR continuum-spectrum distribution with a single-temperature modified blackbody. The distribution of Σdust shows a much better consistency with the integrated intensity of CO(1–0) than with that of [C i](1–0), indicating that CO(1–0) is a good tracer of the cold molecular gas. The spatial distribution of the [C i] excitation temperature, Tex, was examined using the intensity ratio of the two [C i] transitions. An appropriate Tex at the central, bar, arm, and inter-arm regions yields a constant [C]$/$[H2] abundance ratio of ∼7 × 10−5 within a range of 0.1 dex in all regions. We successfully detected weak [C i](1–0) emission, even in the inter-arm region, in addition to the central, arm, and bar regions, using spectral stacking analysis. The stacked intensity of [C i](1–0) is found to be strongly correlated with Tdust. Our results indicate that the atomic carbon is a photodissociation product of CO, and consequently, compared to CO(1–0), [C i](1–0) is less reliable in tracing the bulk of “cold” molecular gas in the galactic disk.

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