scholarly journals FOREST Unbiased Galactic Plane Imaging Survey with the Nobeyama 45 m telescope (FUGIN). IV. Galactic shock wave and molecular bow shock in the 4 kpc arm of the Galaxy

2018 ◽  
Vol 71 (Supplement_1) ◽  
Author(s):  
Yoshiaki Sofue ◽  
Mikito Kohno ◽  
Kazufumi Torii ◽  
Tomofumi Umemoto ◽  
Nario Kuno ◽  
...  
Keyword(s):  
Shock Wave ◽  
Shock Front ◽  
Galactic Plane ◽  
Tangential Direction ◽  
Bow Shock ◽  
Radio Continuum ◽  
Dimensional Structure ◽  
H Ii Regions ◽  
Ionized Gas ◽  
The Galaxy

Abstract The FUGIN CO survey revealed the three-dimensional structure of a galactic shock wave in the tangential direction of the 4 kpc molecular arm. The shock front is located at G30.5+00.0 + 95 km s−1 on the upstream (lower longitude) side of the star-forming complex W 43 (G30.8−0.03), and comprises a molecular bow shock (MBS) concave to W 43, exhibiting an arc-shaped molecular ridge perpendicular to the galactic plane with width ∼0${^{\circ}_{.}}$1(10 pc) and vertical length ∼1° (100 pc). The MBS is coincident with the radio continuum bow of thermal origin, indicating association of ionized gas and similarity to a cometary bright-rimmed cloud. The upstream edge of the bow is sharp, with a growth width of ∼0.5 pc indicative of the shock front property. The velocity width is ∼10 km s−1, and the center velocity decreases by ∼15 km s−1 from the bottom to the top of the bow. The total mass of molecular gas in the MBS is estimated to be ∼1.2 × 106 M⊙, and ionized gas ∼2 × 104 M⊙. The vertical disk thickness has a step-like increase at the MBS by ∼2 times from lower to upper longitudes, which indicates hydraulic jump in the gaseous disk. We argue that the MBS was formed by the galactic shock compression of an accelerated flow in the spiral-arm potential encountering the W 43 molecular complex. A bow-shock theory can reproduce the bow morphology well. We argue that molecular bows are common in galactic shock waves, not only in the Galaxy but also in galaxies, where MBSs are associated with giant cometary H ii regions. We also analyzed the H i data in the same region to obtain a map of H i optical depth and molecular fraction. We found firm evidence of the H i to H2 transition in the galactic shock as revealed by a sharp molecular front at the MBS front.

scholarly journals Gas kinematics and star formation in the filamentary molecular cloud G47.06+0.26

2018 ◽  
Vol 609 ◽  
pp. A43 ◽  
Author(s):  
Jin-Long Xu ◽  
Ye Xu ◽  
Chuan-Peng Zhang ◽  
Xiao-Lan Liu ◽  
Naiping Yu ◽  
...  
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Mass Density ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Filamentary Structure ◽  
Gas Kinematics ◽  
Mean Width ◽  
The Galaxy

Aims. We performed a multi-wavelength study toward the filamentary cloud G47.06+0.26 to investigate the gas kinematics and star formation. Methods. We present the 12CO (J = 1−0), 13CO (J = 1−0) and C18O (J = 1−0) observations of G47.06+0.26 obtained with the Purple Mountain Observation (PMO) 13.7 m radio telescope to investigate the detailed kinematics of the filament. Radio continuum and infrared archival data were obtained from the NRAO VLA Sky Survey (NVSS), the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey, and the Multi-band Imaging Photometer Survey of the Galaxy (MIPSGAL). To trace massive clumps and extract young stellar objects in G47.06+0.26, we used the BGPS catalog v2.0 and the GLIMPSE I catalog, respectively. Results. The 12CO (J = 1−0) and 13CO (J = 1−0) emission of G47.06+0.26 appear to show a filamentary structure. The filament extends about 45′ (58.1 pc) along the east-west direction. The mean width is about 6.8 pc, as traced by the 13CO (J = 1−0) emission. G47.06+0.26 has a linear mass density of ~361.5 M⊙pc-1. The external pressure (due to neighboring bubbles and H II regions) may help preventing the filament from dispersing under the effects of turbulence. From the velocity-field map, we discern a velocity gradient perpendicular to G47.06+0.26. From the Bolocam Galactic Plane Survey (BGPS) catalog, we found nine BGPS sources in G47.06+0.26, that appear to these sources have sufficient mass to form massive stars. We obtained that the clump formation efficiency (CFE) is ~18% in the filament. Four infrared bubbles were found to be located in, and adjacent to, G47.06+0.26. Particularly, infrared bubble N98 shows a cometary structure. CO molecular gas adjacent to N98 also shows a very intense emission. H II regions associated with infrared bubbles can inject the energy to surrounding gas. We calculated the kinetic energy, ionization energy, and thermal energy of two H II regions in G47.06+0.26. From the GLIMPSE I catalog, we selected some Class I sources with an age of ~105 yr, which are clustered along the filament. The feedback from the H II regions may cause the formation of a new generation of stars in filament G47.06+0.26.

scholarly journals An Hα Survey of the Galactic Plane

1998 ◽  
Vol 179 ◽  
pp. 179-181
Author(s):  
Q.A. Parker ◽  
S. Phillipps
Keyword(s):  
Galactic Plane ◽  
Narrow Band ◽  
Interference Filter ◽  
Low Noise ◽  
Magellanic Clouds ◽  
Coverage Depth ◽  
Ionized Gas ◽  
Fine Grain ◽  
The Galaxy ◽  
Very High

We describe a major new Anglo-Australian proposal for a U.K. Schmidt Telescope (UKST) Hα survey of the Southern Galactic plane, Magellanic clouds and selected regions. The agreed survey will use a new 12 × 12 inch monolithic Hα interference filter of very high specification in combination with Tech Pan film. Tech Pan offers significant advantages for this work due to an inherent sensitivity at Hα and its extremely fine grain, high resolution, exceptional DQE, excellent imaging and low noise (e.g., Parker et al. 1994). The combination of Tech Pan and a narrow band Hα filter will provide a survey of unprecendented area coverage, depth and resolution, superior to any previous optical survey of ionized gas in the galaxy. It should to lead to exciting new discoveries and avenues of research.

scholarly journals Giant Molecular Clouds in the Galaxy: The Massachusetts-Stony Brook CO Galactic Plane Survey

1987 ◽  
Vol 115 ◽  
pp. 499-499 ◽  
Author(s):  
P. M. Solomon
Keyword(s):  
Molecular Clouds ◽  
Galactic Plane ◽  
Far Infrared ◽  
Formation Mechanisms ◽  
H Ii Regions ◽  
Giant Molecular Clouds ◽  
Star Forming ◽  
The Galaxy ◽  
Two Populations ◽  
Spiral Arm

The CO Galactic Plane Survey consists of 40,572 spectral line observations in the region between 1 = 8° to 90° and b = −1°.05 to +1°.05 spaced every 3 arc minutes, carried out with the FCRAO 14-m antenna. The velocity coverage from −100 to +200 km/s includes emission from all galactic radii. This high resolution survey was designed to observe and identify essentially all molecular clouds or cloud components larger than 10 parsecs in the inner galaxy. There are two populations of molecular clouds which separate according to temperature. The warm clouds are closely associated with H II regions, exhibit a non-axisymmetric galactic distribution and are a spiral arm population. The cold clouds are a disk population, are not confined to any patterns in longitude-velocity space and must be widespread in the galaxy both in and out of spiral arms. The correlation between far infrared luminosities from IRAS, and molecular masses from CO is utilized to determine a luminosity to mass ratio for the clouds. A face-on picture of the galaxy locating the warm population is presented, showing ring like or spiral arm features at R ∼ 5, 7.5 and 9 kpc. The cloud size and mass spectrum will be discussed and evidence presented showing the presence of clusters of giant molecular clouds with masses of 106 to 107 M⊙. The two populations of clouds probably have different star forming luminosity functions. The implication of the two populations for star formation mechanisms will be discussed.

scholarly journals Ultracompact H ii regions with extended emission: the complete view

2019 ◽  
Vol 492 (1) ◽  
pp. 895-914 ◽  
Author(s):  
Eduardo de la Fuente ◽  
Alicia Porras ◽  
Miguel A Trinidad ◽  
Stanley E Kurtz ◽  
Simon N Kemp ◽  
...  
Keyword(s):  
Morphological Study ◽  
Galactic Plane ◽  
Radio Continuum ◽  
H Ii Regions ◽  
Direct Connection ◽  
Infrared Excess ◽  
Very Large Array ◽  
Bubble Structure ◽  
Colour Composite ◽  
Extended Emission

ABSTRACT In this paper, we present the results of a morphological study performed on a sample of 28 ultracompact H ii (UC H ii) regions located near extended free–free emission, using radio continuum (RC) observations at 3.6 cm with the C and D Very Large Array (VLA) configurations, with the aim of determining a direct connection between them. By using previously published observations in B and D VLA configurations, we compiled a final catalogue of 21 UC H ii regions directly connected with the surrounding extended emission (EE). The observed morphology of most of the UC H ii regions in RC emission is irregular (single- or multipeaked sources) and resembles a classical bubble structure in the Galactic plane with well-defined cometary arcs. RC images superimposed on colour composite Spitzer images reinforce the assignations of direct connection by the spatial coincidence between the UC components and regions of saturated 24 μm emission. We also find that the presence of EE may be crucial to understand the observed infrared excess because an underestimation of ionizing Lyman photons was considered in previous works (e.g. Wood & Churchwell; Kurtz, Churchwell & Wood).

scholarly journals GLOSTAR: Radio Source Catalog I. 28° <  ℓ < 36° and |b| < 1°

2019 ◽  
Vol 627 ◽  
pp. A175 ◽  
Author(s):  
S.-N. X. Medina ◽  
J. S. Urquhart ◽  
S. A. Dzib ◽  
A. Brunthaler ◽  
B. Cotton ◽  
...  
Keyword(s):  
Star Formation ◽  
Software Package ◽  
Large Scale ◽  
Galactic Plane ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Spectral Indices ◽  
The Galaxy ◽  
Reported Data ◽  
Cross Matching

Context. Radio continuum surveys of the Galactic plane are an excellent way to identify different source populations such as planetary nebulae, H II regions, and radio stars and characterize their statistical properties. The Global View of Star Formation in the Milky Way (GLOSTAR) survey will study the star formation in the Galactic plane between −2° < ℓ < 85° and |b| < 1° with unprecedented sensitivity in both flux density (∼40 μJy beam−1) and range ofangular scales (∼1".5 to the largest radio structures in the Galaxy). Aims. In this paper we present the first results obtained from a radio continuum map of a 16-square-degree-sized region of the Galactic plane centered on ℓ = 32° and b = 0° (28° < ℓ < 36° and |b| < 1°). This map has a resolution of 18″ and a sensitivity of ∼60−150 μJy beam−1. Methods. We present data acquired in 40 h of observations with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and they were centered at 4.7 and 6.9 GHz. These data were calibrated and imaged using the Obit software package. The source extraction was performed using the BLOBCAT software package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys. Results. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By cross-matching with other catalogs and calculating the spectral indices (S(ν) ∝ να), we have classified 231 continuum sources as H II regions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources. Conclusions. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature, and relation to previously reported data. These first GLOSTAR results have increased the number of reliable H II regions in this part of the Galaxy by a factor of four.

scholarly journals Linearly Polarised Radio Emission from M83 (NGC 5236) and NGC 891

1990 ◽  
Vol 140 ◽  
pp. 215-218 ◽  
Author(s):  
S. Sukumar ◽  
R.J. Allen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Radio Emission ◽  
Galactic Plane ◽  
Radio Continuum ◽  
The Galaxy ◽  
The Magnetic Field

Recent VLA 20 cm radio continuum observations of the southern face-on barred spiral M83 reveal that the magnetic field is very highly aligned at the outer regions (~12 kpc radius) and totally disrupted in the inner regions (<6 kpc) of the galaxy. The RM variation suggests an axisymmetric morphology for the magnetic field. VLA 6 cm continuum polarization observations of the edge-on spiral NGC 891 reveal ordered magnetic fields at large Z-distances (~3 kpc) from the galactic plane, probably emanating from the disk through instabilities.

scholarly journals Radio and infrared study of southern H II regions G346.056−0.021 and G346.077−0.056

2018 ◽  
Vol 612 ◽  
pp. A36 ◽  
Author(s):  
S. R. Das ◽  
A. Tej ◽  
S. Vig ◽  
T. Liu ◽  
S. K. Ghosh ◽  
...  
Keyword(s):  
Column Density ◽  
Near Infrared ◽  
Local Density ◽  
Far Infrared ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Ionized Gas ◽  
Mid Infrared ◽  
Dust Temperature

Aim. We present a multiwavelength study of two southern Galactic H II regions G346.056−0.021 and G346.077−0.056 which are located at a distance of 10.9 kpc. The distribution of ionized gas, cold and warm dust, and the stellar population associated with the two H II regions are studied in detail using measurements at near-infrared, mid-infrared, far-infrared, submillimeter and radio wavelengths. Methods. The radio continuum maps at 1280 and 610 MHz were obtained using the Giant Metrewave Radio Telescope to probe the ionized gas. The dust temperature, column density, and dust emissivity maps were generated using modified blackbody fits in the far-infrared wavelength range 160–500 μm. Various near- and mid-infrared color and magnitude criteria were adopted to identify candidate ionizing star(s) and the population of young stellar objects in the associated field. Results. The radio maps reveal the presence of diffuse ionized emission displaying distinct cometary morphologies. The 1280 MHz flux densities translate to zero age main sequence spectral types in the range O7.5V–O7V and O8.5V–O8V for the ionizing stars of G346.056−0.021 and G346.077−0.056, respectively. A few promising candidate ionizing star(s) are identified using near-infrared photometric data. The column density map shows the presence of a large, dense dust clump enveloping G346.077−0.056. The dust temperature map shows peaks towards the two H II regions. The submillimeter image shows the presence of two additional clumps, one being associated with G346.056−0.021. The masses of the clumps are estimated to range between ~1400 and 15250 M⊙. Based on simple analytic calculations and the correlation seen between the ionized gas distribution and the local density structure, the observed cometary morphology in the radio maps is better explained invoking the champagne-flow model.

The Marseille Observatory Hα Survey: Comparisons by CO, 6 CM and IRAS Data

1998 ◽  
Vol 179 ◽  
pp. 186-188
Author(s):  
D. Russeil ◽  
P. Amram ◽  
Y.P. Georgelin ◽  
Y.M. Georgelin ◽  
M. Marcelin ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Large Scale ◽  
Galactic Plane ◽  
Photon Counting ◽  
Hii Regions ◽  
Radio Continuum ◽  
Line Of Sight ◽  
Ionized Gas ◽  
Hii Region ◽  
Pattern Determination

The Marseille Observatory Hα survey supplies Hα velocities of the ionized hydrogen over large zones of the sky towards the galactic plane. This survey, led at the ESO La Silla, uses a 36 cm telescope equiped with a scanning Fabry-Perot interferometer and a photon counting camera (Le Coarer et al. 1992). About 250 fields (39′×39′) toward the galactic plane have already been covered (see Figure 1) with a spatial resolution of 9″×9″ and a spectral resolution of 5 km s–1. This allows us to observe the discrete HII regions and the diffuse ionized gas widely distributed between them and to separate the distinct layers found along the line of sight. HII regions are often grouped on the molecular cloud surface, then CO, radio continuum and recombination lines surveys of the galactic plane are also essential to distinguish the HII region-molecular cloud complexes met on the line of sight, and in order to take dynamical effects into account, such as the champagne effect, for the kinematic distance determination. Indeed, the spiral structure pattern determination requires avoiding any artificial spread by clearly identifying the giant complexes composed of molecular clouds, HII regions, diffuse ionized hydrogen widely surrounding them, and exciting stars. On the other hand the ionized gas data (Hα and recombination lines) associated with IRAS data help us to study the nature of the young objects constituent of these complexes and to assess their detectability. We present two fields from the Hα survey and parallel large scale investigations.

scholarly journals The Large-Scale Distribution of Synchrotron Emissivity in the Galaxy

1981 ◽  
Vol 94 ◽  
pp. 223-224 ◽  
Author(s):  
S. Kearsey ◽  
J. L. Osborne ◽  
S. Phillipps ◽  
C.G.T. Haslam ◽  
C. J. Salter ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Radio Continuum ◽  
3 Dimensional ◽  
The Galaxy ◽  
Dimensional Distribution ◽  
Alternative Approaches ◽  
Best Fit

The all-sky radio continuum map at 408 MHz presented at this symposium by Haslam et al. can be interpreted in terms of the large-scale 3-dimensional distribution of synchrotron emissivity in the Galaxy when due allowance is made for the thermal emission. Its derivation from a 2-dimensional map must involve a number of assumptions so it is instructive to compare the results of alternative approaches (described in detail in forthcoming papers by the present authors). In both cases the variation of emissivity in the galactic plane is obtained from the observed intensity profile at b=0o and then the z-variation is chosen to give the best fit to the complete map. The observed profile is shown in the figure with and without the contributions of catalogued supernova remnants and HII regions.

scholarly journals G−0.02−0.07, the compact H ii region complex nearest to the galactic center with ALMA

2019 ◽  
Vol 71 (6) ◽  
Author(s):  
Masato Tsuboi ◽  
Yoshimi Kitamura ◽  
Kenta Uehara ◽  
Atsushi Miyazaki ◽  
Ryosuke Miyawaki ◽  
...  
Keyword(s):  
Shock Wave ◽  
Galactic Center ◽  
Emission Lines ◽  
Continuum Emission ◽  
Molecular Gas ◽  
H Ii Regions ◽  
Recombination Line ◽  
The Galaxy ◽  
H Ii Region ◽  
Absorption Features

Abstract We have observed the compact H ii region complex nearest to the dynamical center of the Galaxy, G−0.02−0.07, using ALMA in the H42α recombination line, CS J = 2–1, H13CO+J = 1–0, and SiO v = 0, J = 2–1 emission lines, and the 86 GHz continuum emission. The H ii regions HII-A to HII-C in the cluster are clearly resolved into a shell-like feature with a bright half and a dark half in the recombination line and continuum emission. The analysis of the absorption features in the molecular emission lines show that H ii-A, B, and C are located on the near side of the “Galactic center 50 km s−1 molecular cloud” (50MC), but HII-D is located on the far side of it. The electron temperatures and densities ranges are Te = 5150–5920 K and ne = 950–2340 cm−3, respectively. The electron temperatures in the bright half are slightly lower than those in the dark half, while the electron densities in the bright half are slightly higher than those in the dark half. The H ii regions are embedded in the ambient molecular gas. There are some molecular gas components compressed by a C-type shock wave around the H ii regions. From the line width of the H42α recombination line, the expansion velocities of HII-A, HII-B, HII-C, and HII-D are estimated to be Vexp = 16.7, 11.6, 11.1, and 12.1 km s−1, respectively. The expansion timescales of HII-A, HII-B, HII-C, and HII-D are estimated to be tage ≃ 1.4 × 104, 1.7 × 104, 2.0 × 104, and 0.7 × 104 yr, respectively. The spectral types of the central stars from HII-A to HII-D are estimated to be O8V, O9.5V, O9V, and B0V, respectively. These derived spectral types are roughly consistent with the previous radio estimation. The positional relation among the H ii regions, the SiO molecule enhancement area, and Class-I maser spots suggest that a shock wave caused by a cloud–cloud collision propagated along the line from HII-C to HII-A in the 50MC. The shock wave would have triggered the massive star formation.

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