A large-scale cloud collision in the galactic center molecular cloud near Sagittarius B21

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.

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Disk-halo interactions: molecular clouds in the Galactic center

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314000490 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 177-181

Author(s):

D. Riquelme ◽

J. Martín-Pintado ◽

R. Mauersberger ◽

S. Martín ◽

L. Bronfman

Keyword(s):

Molecular Cloud ◽

Molecular Clouds ◽

Large Scale ◽

Galactic Center ◽

Galactic Disk ◽

Isotopic Ratio ◽

Small Scale ◽

Kinetic Temperature ◽

Temperature Regimes ◽

Gas Accretion

AbstractWe study the disk-halo interaction, in the context of orbits and Giant Molecular loops (GMLs) in the Galactic center (GC) region. From a large scale survey of the central kpc of the Galaxy, in SiO J = (2 − 1), HCO+J = (1 − 0) and H13CO+J = (1 − 0) molecular emission, we identify shock regions traced by the enhancement of the SiO. These positions were studied using the 12C/13C isotopic ratio to trace gas accretion/ejection. We found a systematically higher 12C/13C isotopic ratio (> 40) toward the GMLs and the x1 orbits than for the GC standard molecular clouds (20–25). The high isotopic ratios are consistent with the accretion of the gas from the halo and from the outskirts of the Galactic disk. From multi-transitional observations of NH3, we derive two kinetic temperature regimes (one warm at ∼150 K and one cold at ∼40 K) for all the positions, except for the GMLs positions where only the warm component is present. The fractional abundances derived from the different molecules support the shock origin for the heating mechanism in the GC. We also present a detailed study of one molecular cloud placed in the foot points of two giant molecular loops, where two of the previously selected positions are placed. Using the 22m Mopra telescope we mapped the molecular cloud M − 3.8 + 0.9 in 3-mm molecular lines. The data show structures at small scale in SiO emission, with narrower line profiles than those of, e.g, HCO+ or HCN, which indicate that the shocks are dynamically confined. The data also show clear differences between different molecular tracers, e.g., between the SiO and HCO+ emission, which would indicate differences in the physical properties and chemistry within the cloud.

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4.6. Structure of the molecular cloud and star-forming activity in the Sagittarius B2 region

Symposium - International Astronomical Union ◽

10.1017/s0074180900084527 ◽

1998 ◽

Vol 184 ◽

pp. 177-178 ◽

Cited By ~ 1

Author(s):

Fumio Sato ◽

Tetsuo Hasegawa ◽

John B. Whiteoak ◽

Ryosuke Miyawaki

Keyword(s):

Star Formation ◽

Molecular Cloud ◽

Large Scale ◽

Massive Star ◽

Galactic Center ◽

Full Description ◽

Grid Spacing ◽

Restricted Area ◽

Star Forming ◽

Right Ascension

Sgr B2 is one of the most active star-forming complexes in our Galaxy located ~100 pc from the Galactic center. Whiteoak et al. (1987) found that groups of the OH and H2CO masers and the compact HII regions are aligned in a north-south line, and suggested that star formation there is being triggered by a single large-scale event such as an interaction between molecular clouds. In order to investigate the total molecular cloud distribution and the triggering mechanism of the active massive-star formation in the Sgr B2 region, we mapped it in the 13CO and C18O (J = 1–0) lines with the Nobeyama 45 m telescope in 1988 March and May. In the 13CO line, an area was mapped of 345″ in right ascension and 495″ in declination covering the whole Sgr B2 molecular cloud at a grid spacing of 15″. In the C18O line, more restricted area was observed at 7.5″ or 15″ spacing. The HPBW of the 45 m telescope was 16″ at 110 GHz. Full description of the observations will be given elsewhere (Whiteoak et al. 1997).

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Remarkable Symmetries in the Milky Way Disc's Magnetic Field

Publications of the Astronomical Society of Australia ◽

10.1071/as10045 ◽

2011 ◽

Vol 28 (2) ◽

pp. 171-176 ◽

Cited By ~ 15

Author(s):

P. P. Kronberg ◽

K. J. Newton-McGee

Keyword(s):

Magnetic Structure ◽

Large Scale ◽

Milky Way ◽

Galactic Center ◽

Galactic Plane ◽

Galactic Disk ◽

Field Structure ◽

Field Pattern ◽

Close Coupling ◽

Sign Change

AbstractWe apply a new, expanded compilation of extragalactic source Faraday rotation measures (RM) to investigate the broad underlying magnetic structure of the Galactic disk at latitudes ∣b∣ ≲15° over all longitudes l, where our total number of RMs is comparable to those in the combined Canadian Galactic Plane Survey (CGPS) at ∣b∣ < 4° and the Southern Galactic Plane (SGPS) ∣b∣<1.5°. We report newly revealed, remarkably coherent patterns of RM at ∣b∣≲15° from l∼270° to ∼90° and RM(l) features of unprecedented clarity that replicate in l with opposite sign on opposite sides of the Galactic center. They confirm a highly patterned bisymmetric field structure toward the inner disc, an axisymmetic pattern toward the outer disc, and a very close coupling between the CGPS/SGPS RMs at ∣b∣≲3° (‘mid-plane’) and our new RMs up to ∣b∣∼15° (‘near-plane’). Our analysis also shows the vertical height of the coherent component of the disc field above the Galactic disc's mid-plane—to be ∼1.5 kpc out to ∼6 kpc from the Sun. This identifies the approximate height of a transition layer to the halo field structure. We find no RM sign change across the plane within ∣b∣∼15° in any longitude range. The prevailing disc field pattern and its striking degree of large-scale ordering confirm that our side of the Milky Way has a very organized underlying magnetic structure, for which the inward spiral pitch angle is 5.5°±1° at all ∣b∣ up to ∼12° in the inner semicircle of Galactic longitudes. It decreases to ∼0° toward the anticentre.

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The magnetic structure of our Galaxy: a review of observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309031123 ◽

2008 ◽

Vol 4 (S259) ◽

pp. 455-466 ◽

Cited By ~ 8

Author(s):

JinLin Han

Keyword(s):

Magnetic Fields ◽

Magnetic Structure ◽

Large Scale ◽

Galactic Halo ◽

Galactic Center ◽

Galactic Plane ◽

Galactic Disk ◽

Dust Emission ◽

Measure Data ◽

Radio Sources

AbstractThe magnetic structure in the Galactic disk, the Galactic center and the Galactic halo can be delineated more clearly than ever before. In the Galactic disk, the magnetic structure has been revealed by starlight polarization within 2 or 3 kpc of the Solar vicinity, by the distribution of the Zeeman splitting of OH masers in two or three nearby spiral arms, and by pulsar dispersion measures and rotation measures in nearly half of the disk. The polarized thermal dust emission of clouds at infrared, mm and submm wavelengths and the diffuse synchrotron emission are also related to the large-scale magnetic field in the disk. The rotation measures of extragalactic radio sources at low Galactic latitudes can be modeled by electron distributions and large-scale magnetic fields. The statistical properties of the magnetized interstellar medium at various scales have been studied using rotation measure data and polarization data. In the Galactic center, the non-thermal filaments indicate poloidal fields. There is no consensus on the field strength, maybe mG, maybe tens of μG. The polarized dust emission and much enhanced rotation measures of background radio sources are probably related to toroidal fields. In the Galactic halo, the antisymmetric RM sky reveals large-scale toroidal fields with reversed directions above and below the Galactic plane. Magnetic fields from all parts of our Galaxy are connected to form a global field structure. More observations are needed to explore the untouched regions and delineate how fields in different parts are connected.

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Low frequency (74 MHz) radio continuum observations of the inner 13° × 7° of the Galactic center

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314001161 ◽

2013 ◽

Vol 9 (S303) ◽

pp. 464-466

Author(s):

M. Rickert ◽

F. Yusef-Zadeh ◽

C. Brogan

Keyword(s):

High Resolution ◽

Molecular Cloud ◽

Supernova Remnant ◽

Galactic Center ◽

Low Frequency ◽

Radio Continuum ◽

Large Array ◽

Very Large Array ◽

Image Displays ◽

Western Side

AbstractWe analyze a high resolution (114″ × 60″) 74 MHz image of the Galactic center taken with the Very Large Array (VLA). We have identified several absorption and emission features in this region, and we discuss preliminary results of two Galactic center sources: the Sgr D complex (G1.1–0.1) and the Galactic center lobe (GCL).The 74 MHz image displays the thermal and nonthermal components of Sgr D and we argue the Sgr D supernova remnant (SNR) is consistent with an interaction with a nearby molecular cloud and the location of the Sgr D Hii region on the near side of the Galactic center. The image also suggests that the emission from the eastern side of the GCL contains a mixture of both thermal and nonthermal sources, whereas the western side is primarily thermal.

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