scholarly journals Induced Star Formation in M17: High Resolution NH3 and IR Observations

1987 ◽  
Vol 115 ◽  
pp. 141-142
Author(s):  
M. Felli ◽  
M. Massi ◽  
R. Stanga ◽  
E. Churchwell
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Type Structure ◽  
Radio Continuum ◽  
Ionization Front ◽  
The South ◽  
The West ◽  
H Ii Region ◽  
Linear Diameter

A VLA radio continuum study of the H II region M17 (Felli, Churchwell and Massi, 1984) has shown the presence of an elongated sharp arc structure in the South Bar of the nebula, in a region of heavy obscuration. The arc has been interpreted as an ionization boundary, viewed edge on, located between the diffuse H II region, to the east, and a dense component of the extended molecular cloud, to the west. About 3″ to the west of this arc, an ultra-compact H II region has been found. This has a shell type structure, a linear diameter of 0.004 pc and probably is the result of induced star formation in the molecular cloud produced by the pressure front preceding the ionization front.

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

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.

scholarly journals The Star Formation Region Associated with the Cometary Nebula GM24

1987 ◽  
Vol 115 ◽  
pp. 188-188
Author(s):  
M. Tapia ◽  
M. Roth ◽  
L.F. Rodríguez ◽  
J. Cantó ◽  
P. Persi ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Near Infrared ◽  
Broad Band ◽  
Large Temperature ◽  
Stellar Objects ◽  
Star Formation Region ◽  
The Past ◽  
Visible Part ◽  
H Ii Region

GM24 is a small visible nebulosity in the vicinity of a molecular cloud. In this contribution we present the results of continuum (6-cm) and CO line (J = 1 → 0) radio observations, infrared maps, broad-band photometry and low-resolution spectroscopy as well as long-slit Echelle Ha spectroscopy. We found evidence that the GM24 = PP85 nebula is part of a larger region where star formation occurred in the past 104 years; the region is embedded in a typical molecular cloud with a dimension of ∼ 10 pc and mass of ∼104 M⊙. A compact radio H II region seems to be associated with GM24 and with one of the mid-infrared peaks detected. The nebula is most probably the visible part of an embedded H II region that is starting to emerge from the cloud. The other infrared peaks found in its vicinity (∼ 1 pc) are probably associated with less evolved stellar objects. The complex also shows an extended near-infrared flux which we believe to arise in a reflection nebula. From energy arguments, we found that the luminosity required to power the H II region and keep the cloud at the observed large temperature (TK ≅33 K), is ∼105 L⊙ which is consistent with the infrared total flux from the present measurements and those from IRAS of 4x104 L⊙; this corresponds to the flux of ∼3 BO ZAMS stars. The details of the present work have appeared in the Revista Mexicana de Astronomía y Astrofísica, Volume 11, 83, 1985.

scholarly journals Dense core structure and fragmentation in the Rho Ophiuchi molecular cloud

1991 ◽  
Vol 147 ◽  
pp. 229-233
Author(s):  
Alwyn Wootten
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Surface Density ◽  
Core Structure ◽  
Dense Core ◽  
Dense Cores ◽  
Rho Ophiuchi ◽  
Very High ◽  
Taurus Molecular Cloud

About a dozen distinct dense cores have been identified in the Rho Ophiuchi molecular cloud. The properties of these cores are summarized and compared to the properties of cores in the Taurus molecular cloud, a less efficient region of star formation, and in DR21(OH), a more massive region of star formation. The data are consistent with a picture in which more massive clouds have a higher surface density of cores, which in turn are more massive. The adjacent cores in L1689N have been studied with very high resolution; one has formed stars and one never has. The structure of these cores shows a tendency for duplicity of structures from the largest scales (1 pc) to the smallest (50 AU).

scholarly journals Triggered high-mass star formation in the H ii region W 28 A2: A cloud–cloud collision scenario

2020 ◽  
Author(s):  
Katsuhiro Hayashi ◽  
Satoshi Yoshiike ◽  
Rei Enokiya ◽  
Shinji Fujita ◽  
Rin Yamada ◽  
...  
Keyword(s):  
Star Formation ◽  
Intensity Ratio ◽  
Molecular Clouds ◽  
Early Stage ◽  
Infrared Emission ◽  
Radio Continuum ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
H Ii Region

Abstract We report on a study of the high-mass star formation in the H ii region W 28 A2 by investigating the molecular clouds that extend over ∼5–10 pc from the exciting stars using the 12CO and 13CO (J = 1–0) and 12CO (J = 2–1) data taken by NANTEN2 and Mopra observations. These molecular clouds consist of three velocity components with CO intensity peaks at VLSR ∼ −4 km s−1, 9 km s−1, and 16 km s−1. The highest CO intensity is detected at VLSR ∼ 9 km s−1, where the high-mass stars with spectral types O6.5–B0.5 are embedded. We found bridging features connecting these clouds toward the directions of the exciting sources. Comparisons of the gas distributions with the radio continuum emission and 8 μm infrared emission show spatial coincidence/anti-coincidence, suggesting physical associations between the gas and the exciting sources. The 12CO J = 2–1 to 1–0 intensity ratio shows a high value (≳0.8) toward the exciting sources for the −4 km s−1 and +9 km s−1 clouds, possibly due to heating by the high-mass stars, whereas the intensity ratio at the CO intensity peak (VLSR ∼ 9 km s−1) decreases to ∼0.6, suggesting self absorption by the dense gas in the near side of the +9 km s−1 cloud. We found partly complementary gas distributions between the −4 km s−1 and +9 km s−1 clouds, and the −4 km s−1 and +16 km s−1 clouds. The exciting sources are located toward the overlapping region in the −4 km s−1 and +9 km s−1 clouds. Similar gas properties are found in the Galactic massive star clusters RCW 38 and NGC 6334, where an early stage of cloud collision to trigger the star formation is suggested. Based on these results, we discuss the possibility of the formation of high-mass stars in the W 28 A2 region being triggered by cloud–cloud collision.

scholarly journals FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VIII. Possible evidence of cloud–cloud collisions triggering high-mass star formation in the giant molecular cloud M 16 (Eagle Nebula)

2020 ◽  
Author(s):  
Atsushi Nishimura ◽  
Shinji Fujita ◽  
Mikito Kohno ◽  
Daichi Tsutsumi ◽  
Tetsuhiro Minamidani ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Velocity Structure ◽  
Galactic Plane ◽  
High Mass ◽  
Mass Star ◽  
Collision Event ◽  
Giant Molecular Cloud ◽  
Eagle Nebula ◽  
H Ii Region

Abstract M 16, the Eagle Nebula, is an outstanding H ii region which exhibits extensive high-mass star formation and hosts remarkable “pillars.” We herein obtained new 12COJ = 1–0 data for the region observed with NANTEN2, which were combined with the 12COJ = 1–0 data obtained using the FOREST unbiased galactic plane imaging with Nobeyama 45 m telescope (FUGIN) survey. These observations revealed that a giant molecular cloud (GMC) of ∼1.3 × 105 M⊙ is associated with M 16, which extends for 30 pc perpendicularly to the galactic plane, at a distance of 1.8 kpc. This GMC can be divided into the northern (N) cloud, the eastern (E) filament, the southeastern (SE) cloud, the southeastern (SE) filament, and the southern (S) cloud. We also found two velocity components (blueshifted and redshifted components) in the N cloud. The blueshifted component shows a ring-like structure, and the redshifted one coincides with the intensity depression of the ring-like structure. The position–velocity diagram of the components showed a V-shaped velocity feature. The spatial and velocity structures of the cloud indicated that two different velocity components collided with each other at a relative velocity of 11.6 km s−1. The timescale of the collision was estimated to be ∼4 × 105 yr. The collision event reasonably explains the formation of the O9V star ALS 15348, as well as the shape of the Spitzer bubble N19. A similar velocity structure was found in the SE cloud, which is associated with the O7.5V star HD 168504. In addition, the complementary distributions of the two velocity components found in the entire GMC suggested that the collision event occurred globally. On the basis of the above results, we herein propose a hypothesis that the collision between the two components occurred sequentially over the last several 106 yr and triggered the formation of O-type stars in the NGC 6611 cluster in M 16.

scholarly journals Stochastic star formation and spiral structure

1985 ◽  
Vol 106 ◽  
pp. 551-558
Author(s):  
Philip E. Seiden
Keyword(s):  
Star Formation ◽  
Long Range ◽  
Molecular Cloud ◽  
Short Range ◽  
Spiral Structure ◽  
Open Cluster ◽  
Gravitational Interaction ◽  
Range Order ◽  
Ionization Front ◽  
Long Range Order

Most approaches to explaining the long-range order of the spiral arms in galaxies assume that it is induced by the long-range gravitational interaction. However, it is well-known in many fields of physics that long-range order may be induced by short-range interactions. A typical example is magnetism, where the exchange interaction between magnetic spins has a range of only 10 ångströms, yet a bar magnet can be made as large as one likes. Stochastic self-propagating star formation (SSPSF) starts from the point of view of a short-range interaction and examines the spiral structure arising from it (Seiden and Gerola 1982). We assume that the energetic processes of massive stars, stellar winds, ionization-front shocks and supernova shocks, in an OB association or open cluster can induce the creation of a new molecular cloud from cold interstellar atomic hydrogen. In turn this new molecular cloud will begin to form stars that will allow the process to repeat, creating a chain reaction. The differential rotation existing in a spiral galaxy will stretch the aggregation of recently created stars into spiral features.

scholarly journals Star Formation in the NGC 2071 Molecular Cloud

1989 ◽  
Vol 120 ◽  
pp. 128-128
Author(s):  
N.J. Evans
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Density Distribution ◽  
Molecular Cloud ◽  
Large Scale ◽  
Far Infrared ◽  
Infrared Emission ◽  
Molecular Outflow ◽  
Broad Array ◽  
Coherent Picture

The NGC 2071 molecular cloud has been studied with a broad array of techniques, including a large scale study of CS emission, high resolution scans in the far-infrared, N H3 studies with the VLA, and near-infrarred imaging. The far-infrared emission constrains the density distribution to fall off approximately as r−1. The NH3 data strongly supports the presence of a disk oriented perpendicular to the molecular outflow, while the CS emission indicates the presence of dense gas in the region. The results will be combined into a coherent picture of this region of current star formation and molecular outflow.

scholarly journals Massive Star Formation in W49

1987 ◽  
Vol 115 ◽  
pp. 143-145
Author(s):  
J. Dreher ◽  
S. Vogel ◽  
S. Terebey ◽  
W. J. Welch
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Massive Star ◽  
Hii Regions ◽  
Molecular Line ◽  
The Galaxy ◽  
Molecular Lines ◽  
H Ii Region ◽  
Scale Structures ◽  
The Continuum

W49 is the most luminous H II region complex in the galaxy. VLA maps in the continuum reveal a complex of more than two dozen compact HII regions, including a ring-like distribution of a dozen such regions within a volume of 1 pc. In addition to the VLA maps, we have obtained high resolution maps in this field with the Hat Creek Millimeter Interferometer in the following molecular lines: HCO+(1-0), H13CO+(1-0), SiO(v = 0, J = 2-1), SiO(v = 1, J = 2-1), H13CN(1-0), HC15N(1-0), SO2 [8(3,5)-9(2,8)], SO2[8(1,7)-8(0,8)], SO[2(2)-1(1)], and CH3CH2CN[10(1,10)-9(1,9)], all near 3 mm wavelengh. These maps will be discussed. The HCO+distribution corresponds to the larger scale structures observed in the continuum maps. In contrast the SO and SiO sources are quite compact. Using the detailed molecular line results obtained in the ORION/KL region as a guide, we are able to identify these latter sources as regions in which the star formation is at an earlier stage, regions where there are outflows.

scholarly journals Supersonic Expansion of the Bipolar H ii Region Sh2-106: A 3500 Year Old Explosion?

2022 ◽  
Vol 924 (2) ◽  
pp. 50
Author(s):  
John Bally ◽  
Zen Chia ◽  
Adam Ginsburg ◽  
Bo Reipurth ◽  
Kei E. I Tanaka ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Hubble Space Telescope ◽  
Radio Continuum ◽  
Proper Motions ◽  
The West ◽  
Supersonic Expansion ◽  
Near Ir ◽  
H Ii Region ◽  
Direct Illumination ◽  
Projected Distance

Abstract Multi-epoch narrowband Hubble Space Telescope images of the bipolar H ii region Sh2-106 reveal highly supersonic nebular proper motions that increase with projected distance from the massive young stellar object S106 IR, reaching over ∼30 mas yr−1 (∼150 km s−1 at D = 1.09 kpc) at a projected separation of ∼1.′4 (0.44 pc) from S106 IR. We propose that S106 IR experienced a ∼1047 erg explosion ∼3500 yr ago. The explosion may be the result of a major accretion burst or a recent encounter with another star, or a consequence of the interaction of a companion with the bloated photosphere of S106 IR as it grew from ∼10 through ∼15 M ⊙ at a high accretion rate. Near-IR images reveal fingers of H2 emission pointing away from S106 IR and an asymmetric photon-dominated region surrounding the ionized nebula. Radio continuum and Brγ emission reveal a C-shaped bend in the plasma, indicating either the motion of S106 IR toward the east, or the deflection of plasma toward the west by the surrounding cloud. The H ii region bends around a ∼1′ diameter dark bay west of S106 IR that may be shielded from direct illumination by a dense molecular clump. Herbig–Haro and Molecular Hydrogen Objects tracing outflows powered by stars in the Sh2-106 protocluster such as the Class 0 source S106 FIR are discussed.

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