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 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 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 Magnetic fields and massive star formation

2018 ◽  
Vol 14 (A30) ◽  
pp. 141-141
Author(s):  
Qizhou Zhang
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Dense Core ◽  
Continuum Emission ◽  
Massive Star Formation ◽  
Stellar Objects ◽  
Star Forming ◽  
Dense Cores ◽  
The Mean

AbstractMassive stars ( ${\rm{M}} > \,8{M_ \odot }$ ) often form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. The role of magnetic fields during the formation of massive dense cores is still not clear. The steady improvement in sensitivity of (sub)millimeter interferometers over the past decade enabled observations of dust polarization of large samples of massive star formation regions. We carried out a polarimetric survey with the Submillimeter Array of 14 massive star forming clumps in continuum emission at a wavelength of 0.89 mm. This unprecedentedly large sample of massive star forming regions observed by a submillimeter interferometer before the advent of ALMA revealed compelling evidence of strong magnetic influence on the gas dynamics from 1 pc to 0.1 pc scales. We found that the magnetic fields in dense cores tend to be either parallel or perpendicular to the mean magnetic fields in their parental molecular clumps. Furthermore, the main axis of protostellar outflows does not appear to be aligned with the mean magnetic fields in the dense core where outflows are launched. These findings suggest that from 1 pc to 0.1 pc scales, magnetic fields are dynamically important in the collapse of clumps and the formation of dense cores. From the dense core scale to the accretion disk scale of ∼102 au, however, gravity and angular momentum appear to be more dominant relative to the magnetic field.

scholarly journals The headlight cloud in NGC 628: An extreme giant molecular cloud in a typical galaxy disk

2020 ◽  
Vol 634 ◽  
pp. A121 ◽  
Author(s):  
Cinthya N. Herrera ◽  
Jérôme Pety ◽  
Annie Hughes ◽  
Sharon E. Meidt ◽  
Kathryn Kreckel ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Stellar Population ◽  
High Mass ◽  
Molecular Gas ◽  
Giant Molecular Cloud ◽  
The Impact

Context. Cloud-scale surveys of molecular gas reveal the link between giant molecular cloud properties and star formation across a range of galactic environments. Cloud populations in galaxy disks are considered to be representative of the normal star formation process, while galaxy centers tend to harbor denser gas that exhibits more extreme star formation. At high resolution, however, molecular clouds with exceptional gas properties and star formation activity may also be observed in normal disk environments. In this paper we study the brightest cloud traced in CO(2–1) emission in the disk of nearby spiral galaxy NGC 628. Aims. We characterize the properties of the molecular and ionized gas that is spatially coincident with an extremely bright H II region in the context of the NGC 628 galactic environment. We investigate how feedback and large-scale processes influence the properties of the molecular gas in this region. Methods. High-resolution ALMA observations of CO(2–1) and CO(1−0) emission were used to characterize the mass and dynamical state of the “headlight” molecular cloud. The characteristics of this cloud are compared to the typical properties of molecular clouds in NGC 628. A simple large velocity gradient (LVG) analysis incorporating additional ALMA observations of 13CO(1−0), HCO+(1−0), and HCN(1−0) emission was used to constrain the beam-diluted density and temperature of the molecular gas. We analyzed the MUSE spectrum using Starburst99 to characterize the young stellar population associated with the H II region. Results. The unusually bright headlight cloud is massive (1 − 2 × 107 M⊙), with a beam-diluted density of nH2 = 5 × 104 cm−3 based on LVG modeling. It has a low virial parameter, suggesting that the CO emission associated with this cloud may be overluminous due to heating by the H II region. A young (2 − 4 Myr) stellar population with mass 3 × 105 M⊙ is associated. Conclusions. We argue that the headlight cloud is currently being destroyed by feedback from young massive stars. Due to the large mass of the cloud, this phase of the its evolution is long enough for the impact of feedback on the excitation of the gas to be observed. The high mass of the headlight cloud may be related to its location at a spiral co-rotation radius, where gas experiences reduced galactic shear compared to other regions of the disk and receives a sustained inflow of gas that can promote the mass growth of the cloud.

scholarly journals Compact Disks in a High-resolution ALMA Survey of Dust Structures in the Taurus Molecular Cloud

2019 ◽  
Vol 882 (1) ◽  
pp. 49 ◽  
Author(s):  
Feng Long ◽  
Gregory J. Herczeg ◽  
Daniel Harsono ◽  
Paola Pinilla ◽  
Marco Tazzari ◽  
...  
Keyword(s):  
High Resolution ◽  
Molecular Cloud ◽  
Compact Disks ◽  
Taurus Molecular Cloud

scholarly journals AN AMMONIA SPECTRAL MAP OF THE L1495-B218 FILAMENTS IN THE TAURUS MOLECULAR CLOUD. I. PHYSICAL PROPERTIES OF FILAMENTS AND DENSE CORES

2015 ◽  
Vol 805 (2) ◽  
pp. 185 ◽  
Author(s):  
Young Min Seo ◽  
Yancy L. Shirley ◽  
Paul Goldsmith ◽  
Derek Ward-Thompson ◽  
Jason M. Kirk ◽  
...  
Keyword(s):  
Physical Properties ◽  
Molecular Cloud ◽  
Dense Cores ◽  
Taurus Molecular Cloud

scholarly journals What is a GMC? Are observers and simulators discussing the same star-forming clouds?

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Hsi-An Pan ◽  
Yusuke Fujimoto ◽  
Elizabeth J. Tasker
Keyword(s):  
Data Structure ◽  
Star Formation ◽  
High Resolution ◽  
Molecular Cloud ◽  
Velocity Dispersion ◽  
Line Of Sight ◽  
Data Sets ◽  
Star Forming ◽  
Cloud Properties ◽  
Small Scatter

AbstractObservations and simulations have now reached the point where the giant molecular cloud (GMCs) populations can be studied over a whole galaxy. This is immensely helpful for understanding star formation. Yet, are these two groups really comparing the same objects? While simulators work in 6D (x, y, z, vx, vy, vz) position-position-position (PPP) space, observers see 2 + 1D (RA, Dec, vlos) projected properties along the line of sight, identifying clouds in position-position-velocity (PPV) space. In this research we generated PPP and PPV data for a high-resolution simulated galaxy and compared the identified clouds in both data sets. The results show that 70% of the clouds have a single counterpart in each data structure. Cloud boundaries of these clouds are indeed the same. Scatter of the derived cloud properties (radius and velocity dispersion) between PPP and PPV are typically within a factor of two. However, this small scatter can make it difficult to determine if a cloud is truly gravitationally bound.

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.

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