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 A multiwavelength study of filamentary cloud G341.244-00.265

2019 ◽  
Vol 622 ◽  
pp. A155 ◽  
Author(s):  
Nai-Ping Yu ◽  
Jing-Long Xu ◽  
Jun-Jie Wang
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Galactic Plane ◽  
Mass Density ◽  
Spectral Energy Distribution ◽  
Radio Continuum ◽  
Spectral Energy ◽  
Wide Field ◽  
Molecular Line ◽  
Filamentary Structure

We present a multiwavelength study toward the filamentary molecular cloud G341.244-00.265, to investigate the physical and chemical properties, as well as star formation activities taking place therein. Our radio continuum and molecular line data were obtained from the Sydney University Molonglo Sky Survey (SUMSS), Atacama Pathfinder Experiment Telescope Large Area Survey of the Galaxy (ATLASGAL), Structure, excitation, and dynamics of the inner Galactic interstellar medium (SEDIGISM) and Millimeter Astronomy Legacy Team Survey at 90 GHz (MALT90). The infrared archival data come from Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE), Wide-field Infrared Survey Explorer (WISE), and Herschel InfraRed Galactic Plane Survey (Hi-GAL). G341.244-00.265 displays an elongated filamentary structure both in far-infrared and molecular line emissions; the “head” and “tail” of this molecular cloud are associated with known infrared bubbles S21, S22, and S24. We made H2 column density and dust temperature maps of this region by the spectral energy distribution (SED) method. G341.244-00.265 has a linear mass density of about 1654 M⊙ pc−1 and has a projected length of 11.1 pc. The cloud is prone to collapse based on the virial analysis. Even though the interactions between this filamentary cloud and its surrounding bubbles are evident, we found these bubbles are too young to trigger the next generation of star formation in G341.244-00.265. From the ATLASGAL catalog, we found eight dense massive clumps associated with this filamentary cloud. All of these clumps have sufficient mass to form massive stars. Using data from the GLIMPSE and WISE survey, we search the young stellar objects (YSOs) in G341.244-00.265. We found an age gradient of star formation in this filamentary cloud: most of the YSOs distributed in the center are Class I sources, while most Class II candidates are located in the head and tail of G341.244-00.265, indicating star formation at the two ends of this filament is prior to the center. The abundance ratio of N(N2H+)/N(C18O) is higher in the center than that in the two ends, also indicating that the gas in the center is less evolved. Taking into account the distributions of YSOs and the N(N2H+)/N(C18O) ratio map, our study is in agreement with the prediction of the so-called “end-dominated collapse” star formation scenario.

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.

Resolved star formation in the metal-poor star-forming region Magellanic Bridge C

2020 ◽  
Vol 499 (2) ◽  
pp. 2534-2553
Author(s):  
Venu M Kalari ◽  
Monica Rubio ◽  
Hugo P Saldaño ◽  
Alberto D Bolatto
Keyword(s):  
Star Formation ◽  
Infrared Imaging ◽  
Far Infrared ◽  
Young Stellar Objects ◽  
Molecular Gas ◽  
Stellar Objects ◽  
Filamentary Structure ◽  
Star Forming ◽  
The Galaxy ◽  
Pms Stars

ABSTRACT Magellanic Bridge C (MB-C) is a metal-poor (∼1/5 Z⊙) low-density star-forming region located 59 kpc away in the Magellanic Bridge, offering a resolved view of the star formation process in conditions different to the Galaxy. From Atacama Large Millimetre Array CO (1–0) observations, we detect molecular clumps associated with candidate young stellar objects (YSOs), pre-main sequence (PMS) stars, and filamentary structure identified in far-infrared imaging. YSOs and PMS stars form in molecular gas having densities between 17 and 200 M⊙ pc−2, and have ages between ≲0.1 and 3 Myr. YSO candidates in MB -C have lower extinction than their Galactic counterparts. Otherwise, our results suggest that the properties and morphologies of molecular clumps, YSOs, and PMS stars in MB -C present no patent differences with respect to their Galactic counterparts, tentatively alluding that the bottleneck to forming stars in regions similar to MB-C is the conversion of atomic gas to molecular.

scholarly journals The Seahorse Nebula: New views of the filamentary infrared dark cloud G304.74+01.32 from SABOCA, Herschel, and WISE

2018 ◽  
Vol 609 ◽  
pp. A123 ◽  
Author(s):  
O. Miettinen
Keyword(s):  
Star Formation ◽  
Mass Density ◽  
Surrounding Medium ◽  
High Mass ◽  
Mass Star ◽  
Wide Field ◽  
Intermediate Mass ◽  
Filamentary Structure ◽  
Mean Width ◽  
The Mean

Context. Filamentary molecular clouds, such as many of the infrared dark clouds (IRDCs), can undergo hierarchical fragmentation into substructures (clumps and cores) that can eventually collapse to form stars. Aims. We aim to determine the occurrence of fragmentation into cores in the clumps of the filamentary IRDC G304.74+01.32 (hereafter, G304.74). We also aim to determine the basic physical characteristics (e.g. mass, density, and young stellar object (YSO) content) of the clumps and cores in G304.74. Methods. We mapped the G304.74 filament at 350 μm using the Submillimetre APEX Bolometer Camera (SABOCA) bolometer. The new SABOCA data have a factor of 2.2 times higher resolution than our previous Large APEX BOlometer CAmera (LABOCA) 870 μm map of the cloud (9″ vs. 19 .̋ 86). We also employed the Herschel far-infrared (IR) and submillimetre, and Wide-field Infrared Survey Explorer (WISE) IR imaging data available for G304.74. The WISE data allowed us to trace the IR emission of the YSOs associated with the cloud. Results. The SABOCA 350 μm data show that G304.74 is composed of a dense filamentary structure with a mean width of only 0.18 ± 0.05 pc. The percentage of LABOCA clumps that are found to be fragmented into SABOCA cores is 36% ± 16%, but the irregular morphology of some of the cores suggests that this multiplicity fraction could be higher. The WISE data suggest that 65% ± 18% of the SABOCA cores host YSOs. The mean dust temperature of the clumps, derived by comparing the Herschel 250, 350, and 500 μm flux densities, was found to be 15.0 ± 0.8 K. The mean mass, beam-averaged H2 column density, and H2 number density of the LABOCA clumps are estimated to be 55 ± 10M⊙, (2.0 ± 0.2) × 1022 cm-2, and (3.1 ± 0.2) × 104 cm-3. The corresponding values for the SABOCA cores are 29 ± 3M⊙, (2.9 ± 0.3) × 1022 cm-2, and (7.9 ± 1.2) × 104 cm-3. The G304.74 filament is estimated to be thermally supercritical by a factor of ≳ 3.5 on the scale probed by LABOCA, and by a factor of ≳ 1.5 for the SABOCA filament. Conclusions. Our data strongly suggest that the IRDC G304.74 has undergone hierarchical fragmentation. On the scale where the clumps have fragmented into cores, the process can be explained in terms of gravitational Jeans instability. Besides the filament being fragmented, the finding of embedded YSOs in G304.74 indicates its thermally supercritical state, although the potential non-thermal (turbulent) motions can render the cloud a virial equilibrium system on scale traced by LABOCA. The IRDC G304.74 has a seahorse-like morphology in the Herschel images, and the filament appears to be attached by elongated, perpendicular striations. This is potentially evidence that G304.74 is still accreting mass from the surrounding medium, and the accretion process can contribute to the dynamical evolution of the main filament. One of the clumps in G304.74, IRAS 13039-6108, is already known to be associated with high-mass star formation, but the remaining clumps and cores in this filament might preferentially form low and intermediate-mass stars owing to their mass reservoirs and sizes. Besides the presence of perpendicularly oriented, dusty striations and potential embedded intermediate-mass YSOs, G304.74 is a relatively nearby (d ~ 2.5 kpc) IRDC, which makes it a useful target for future star formation studies. Owing to its observed morphology, we propose that G304.74 could be nicknamed the Seahorse Nebula.

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 Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane

2017 ◽  
Vol 605 ◽  
pp. A35 ◽  
Author(s):  
P. Palmeirim ◽  
A. Zavagno ◽  
D. Elia ◽  
T. J. T. Moore ◽  
A. Whitworth ◽  
...  
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Formation Rate ◽  
Radio Continuum ◽  
Young Stellar Objects ◽  
Evolutionary Trend ◽  
Stellar Objects ◽  
Star Forming ◽  
Early Stages ◽  
Local Environments

We present a comprehensive statistical analysis of star-forming objects located in the vicinities of 1360 bubble structures throughout the Galactic plane and their local environments. The compilation of ~70 000 star-forming sources, found in the proximity of the ionized (Hii) regions and detected in both Hi-GAL and GLIMPSE surveys, provided a broad overview of the different evolutionary stages of star-formation in bubbles, from prestellar objects to more evolved young stellar objects (YSOs). Surface density maps of star-forming objects clearly reveal an evolutionary trend where more evolved star-forming objects (Class II YSO candidates) are found spatially located near the center, while younger star-forming objects are found at the edge of the bubbles. We derived dynamic ages for a subsample of 182 H ii regions for which kinematic distances and radio continuum flux measurements were available. We detect approximately 80% more star-forming sources per unit area in the direction of bubbles than in the surrounding fields. We estimate the clump formation efficiency (CFE) of Hi-GAL clumps in the direction of the shell of the bubbles to be ~15%, around twice the value of the CFE in fields that are not affected by feedback effects. We find that the higher values of CFE are mostly due to the higher CFE of protostellar clumps, in particular in younger bubbles, whose density of the bubble shells is higher. We argue that the formation rate from prestellar to protostellar phase is probably higher during the early stages of the (H ii ) bubble expansion. Furthermore, we also find a higher fraction of massive YSOs (MYSOs) in bubbles at the early stages of expansion (<2 Myr) than older bubbles. Evaluation of the fragmentation time inside the shell of bubbles advocates the preexistence of clumps in the medium before the bubble expansion in order to explain the formation of MYSOs in the youngest H ii regions (<1 Myr), as supported by numerical simulations. Approximately 23% of the Hi-GAL clumps are found located in the direction of a bubble, with 15% for prestellar clumps and 41% for protostellar clumps. We argue that the high fraction of protostellar clumps may be due to the acceleration of the star-formation process cause by the feedback of the (Hii) bubbles.

scholarly journals Three generations of stars: a possible case of triggered star formation

2020 ◽  
Vol 496 (1) ◽  
pp. 870-874
Author(s):  
M B Areal ◽  
A Buccino ◽  
S Paron ◽  
C Fariña ◽  
M E Ortega
Keyword(s):  
Star Formation ◽  
Young Stellar Objects ◽  
H Ii Regions ◽  
Stellar Objects ◽  
Three Generations ◽  
The North ◽  
Western Border ◽  
H Ii Region ◽  
New Generation ◽  
North Western

ABSTRACT Evidence for triggered star formation linking three generations of stars is difficult to assemble, as it requires convincingly associating evolved massive stars with H ii regions that, in turn, would need to present signs of active star formation. We present observational evidence for triggered star formation relating three generations of stars in the neighbourhood of the star LS II +26 8. We carried out new spectroscopic observations of LS II +26 8, revealing that it is a B0 III-type star. We note that LS II +26 8 is located exactly at the geometric centre of a semi-shell-like H ii region complex. The most conspicuous component of this complex is the H ii region Sh2-90, which is probably triggering a new generation of stars. The distances to LS II +26 8 and to Sh2-90 are in agreement (between 2.6 and 3 kpc). Analysis of the interstellar medium on a larger spatial scale shows that the H ii region complex lies on the north-western border of an extended H2 shell. The radius of this molecular shell is about 13 pc, which is in agreement with what an O9 V star (the probable initial spectral type of LS II +26 8 as inferred from evolutive tracks) can generate through its winds in the molecular environment. In conclusion, the spatial and temporal correspondences derived in our analysis enable us to propose a probable triggered star formation scenario initiated by the evolved massive star LS II +26 8 during its main-sequence stage, followed by stars exciting the H ii region complex formed in the molecular shell, and culminating in the birth of young stellar objects around Sh2-90.

scholarly journals Molecular and ionized gas kinematics in the GC Radio Arc

2016 ◽  
Vol 11 (S322) ◽  
pp. 133-136
Author(s):  
N. Butterfield ◽  
C.C. Lang ◽  
E. A. C. Mills ◽  
D. Ludovici ◽  
J. Ott ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Radio Continuum ◽  
Molecular Gas ◽  
The South ◽  
Ionized Gas ◽  
Molecular Emission ◽  
Gas Kinematics

AbstractWe present NH3 and H64α+H63α VLA observations of the Radio Arc region, including the M0.20 – 0.033 and G0.10 – 0.08 molecular clouds. These observations suggest the two velocity components of M0.20 – 0.033 are physically connected in the south. Additional ATCA observations suggest this connection is due to an expanding shell in the molecular gas, with the centroid located near the Quintuplet cluster. The G0.10 – 0.08 molecular cloud has little radio continuum, strong molecular emission, and abundant CH3OH masers, similar to a nearby molecular cloud with no star formation: M0.25+0.01. These features detected in G0.10 – 0.08 suggest dense molecular gas with no signs of current star formation.

scholarly journals Gas and hidden star formation in NGC 5253

1999 ◽  
Vol 193 ◽  
pp. 758-759
Author(s):  
Jean L. Turner ◽  
Sara C. Beck ◽  
Paul T.P. Ho
Keyword(s):  
Star Formation ◽  
Radio Continuum ◽  
H Ii Regions ◽  
The North

We confirm the presence of compact H II regions in the center of the starburst in NGC 5253 through the detection of optically thick free-free emission. The number of O-type stars implied by the excitation of these nebulae is nearly two orders of magnitude larger than what is indicated by the radio continuum fluxes. The compact H II regions are located 70 pc to the north of the location of the Wolf-Rayet feature. Implied extinctions are extremely high. Not all WR galaxies can be identified as such due to extinction.

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