scholarly journals Constraining How Star Formation Proceeds: Surveys in the Sub-mm and FIR

2009 ◽  
Vol 5 (H15) ◽  
pp. 406-407
Author(s):  
Doug Johnstone
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Mass Star ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Multi Wavelength ◽  
Low Mass ◽  
High Column

AbstractCoordinated multi-wavelength surveys of molecular clouds are providing strong constraints on the physical conditions within low-mass star-forming regions. In this manner, Perseus and Ophiuchus have been exceptional laboratories for testing the earliest phases of star formation. Highlights of these results are: (1) dense cores form only in high column density regions, (2) dense cores contain only a few percent of the cloud mass, (3) the mass distribution of the dense cores is similar to the IMF, (4) the more massive cores are most likely to contain embedded protostars, and (5) the kinematics of the dense cores and the bulk gas show significant coupling.

scholarly journals Objective Prism Study of Star Forming Regions

1994 ◽  
Vol 161 ◽  
pp. 470-472
Author(s):  
M. Kun
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Wavelength Region ◽  
Mass Star ◽  
Star Forming ◽  
Millimeter Wavelength ◽  
Star Forming Regions ◽  
Low Mass ◽  
Objective Prism

Radio molecular observations in the millimeter wavelength region in the last decade have revealed a number of giant molecular cloud complexes at relatively high galactic latitudes. Examples for such cloud complexes are Cepheus Flare (Lebrun 1986), and Ursa Major and Camelopardalis clouds (Heithausen et al. 1993). Because of their high galactic latitudes, these cloud complexes probably belong to the nearest molecular clouds and among them we may find some nearby regions of low-mass star formation.

scholarly journals Low-Mass Versus High-Mass Star Formation

1997 ◽  
Vol 182 ◽  
pp. 537-549
Author(s):  
T. W. Hartquist ◽  
J. E. Dyson
Keyword(s):  
Star Formation ◽  
Young Stars ◽  
High Mass ◽  
Mass Star ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Global Properties ◽  
Low Mass

Structures like the clumps identified in the CO maps of the Rosette Molecular Cloud and the dense cores such as those in B5, a cluster of cores and young low-mass stars, are key to considerations of star formation. Whether star formation is a self-inducing process or one that causes itself to turn off depends greatly on whether the responses of the interclump and intercore media to young stars cause the collapse of clumps or cores to be faster than their ablation. We present a naive introduction to the lengthscales over which such responses are significant, mention ways in which the responses might induce collapse, review some of the little that is known of how flows of media around clumps and cores ablate them, and then return to the issue of the lengthscales over which such responses are significant by considering the global properties of mass-loaded flows in clumpy star forming regions.

scholarly journals Deuterium fractionation in low-mass star-forming regions

2021 ◽  
Author(s):  
A. F. Punanova ◽  
◽  
I. V. Petrashkevich ◽  
Keyword(s):  
Molecular Clouds ◽  
Mass Star ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Low Mass

In this work, we study how deuterium fraction changes depending on the physical conditions in cold cores embedded in the molecular clouds of Taurus, Perseus and Ophiuchus. The results show that the deuterium fraction in cold cores varies in different star-forming regions. In the densest and most turbulent of the studied regions, L1688 in Ophiuchus, the deuterium fraction is two times higher than that of L1495 in Taurus and B5 in Perseus. In L1495 and L1688, the deuterium fraction in the central parts of the cores and in their envelopes differ by a factor of 10, while in B5 only by a factor of 2—3.

scholarly journals Submillimeter Array Observations of Magnetic Fields in Star Forming Regions

2010 ◽  
Vol 6 (S270) ◽  
pp. 103-106
Author(s):  
R. Rao ◽  
J.-M. Girart ◽  
D. P. Marrone
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Computational Models ◽  
Dominant Role ◽  
Theoretical Models ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

AbstractThere have been a number of theoretical and computational models which state that magnetic fields play an important role in the process of star formation. Competing theories instead postulate that it is turbulence which is dominant and magnetic fields are weak. The recent installation of a polarimetry system at the Submillimeter Array (SMA) has enabled us to conduct observations that could potentially distinguish between the two theories. Some of the nearby low mass star forming regions show hour-glass shaped magnetic field structures that are consistent with theoretical models in which the magnetic field plays a dominant role. However, there are other similar regions where no significant polarization is detected. Future polarimetry observations made by the Submillimeter Array should be able to increase the sample of observed regions. These measurements will allow us to address observationally the important question of the role of magnetic fields and/or turbulence in the process of star formation.

scholarly journals Warm gas in protostellar outflows

2019 ◽  
Vol 629 ◽  
pp. A77
Author(s):  
A. I. Gómez-Ruiz ◽  
A. Gusdorf ◽  
S. Leurini ◽  
K. M. Menten ◽  
S. Takahashi ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
High Velocity ◽  
The Other ◽  
Mass Star ◽  
Intermediate Mass ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Low Mass ◽  
Kinematic Properties

Context. OMC-2/3 is one of the nearest embedded cluster-forming regions that includes intermediate-mass protostars at early stages of evolution. A previous CO (3–2) mapping survey towards this region revealed outflow activity related to sources at different evolutionary phases. Aims. The present work presents a study of the warm gas in the high-velocity emission from several outflows found in CO (3–2) emission by previous observations, determines their physical conditions, and makes a comparison with previous results in low-mass star-forming regions. Methods. We used the CHAMP+ heterodyne array on the APEX telescope to map the CO (6–5) and CO (7–6) emission in the OMC-2 FIR 6 and OMC-3 MMS 1-6 regions, and to observe 13CO (6–5) at selected positions. We analyzed these data together with previous CO (3–2) observations. In addition, we mapped the SiO (5–4) emission in OMC-2 FIR 6. Results. The CO (6–5) emission was detected in most of the outflow lobes in the mapped regions, while the CO (7–6) was found mostly in the OMC-3 outflows. In the OMC-3 MMS 5 outflow, a previously undetected extremely high-velocity gas was found in CO (6–5). This extremely high-velocity emission arises from the regions close to the central object MMS 5. Radiative transfer models revealed that the high-velocity gas from MMS 5 outflow consists of gas with nH2 = 104–105 cm−3 and T > 200 K, similar to what is observed in young Class 0 low-mass protostars. For the other outflows, values of nH2 > 104 cm−3 were found. Conclusions. The physical conditions and kinematic properties of the young intermediate-mass outflows presented here are similar to those found in outflows from Class 0 low-mass objects. Due to their excitation requirements, mid − J CO lines are good tracers of extremely high-velocity gas in young outflows likely related to jets.

scholarly journals Drama of HII regions: Clustered and Triggered Star Formation

2015 ◽  
Vol 12 (S316) ◽  
pp. 129-130
Author(s):  
Jin-Zeng Li ◽  
Jinghua Yuan ◽  
Hong-Li Liu ◽  
Yuefang Wu ◽  
Ya-Fang Huang
Keyword(s):  
Star Formation ◽  
Hii Regions ◽  
Radio Telescopes ◽  
Physical Status ◽  
Mid Infrared ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores ◽  
Compressed Gas ◽  
Multi Wavelength

AbstractIn order to understand the star formation process under the influence of H ii regions, we have carried out extensive investigations to well selected star-forming regions which all have been profoundly affected by existing massive O type stars. On the basis of multi-wavelength data from mid-infrared to millimeter collected using Spitzer, Herschel, and ground based radio telescopes, the physical status of interstellar medium and star formation in these regions have been revealed. In a relatively large infrared dust bubble, active star formation is undergoing and the shell is still expanding. Signs of compressed gas and triggered star formation have been tentatively detected in a relatively small bubble. The dense cores in the Rosette Molecular Complex detected at 1.1 mm using SMA have been speculated to have a likely triggered origin according to their spatial distribution. Although some observational results have been obtained, more efforts are necessary to reach trustworthy conclusions.

scholarly journals HIGH- AND LOW-MASS STAR-FORMING REGIONS FROM HIERARCHICAL GRAVITATIONAL FRAGMENTATION. HIGH LOCAL STAR FORMATION RATES WITH LOW GLOBAL EFFICIENCIES

2009 ◽  
Vol 707 (2) ◽  
pp. 1023-1033 ◽  
Author(s):  
Enrique Vázquez-Semadeni ◽  
Gilberto C. Gómez ◽  
A.-Katharina Jappsen ◽  
Javier Ballesteros-Paredes ◽  
Ralf S. Klessen
Keyword(s):  
Star Formation ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

scholarly journals Class I methanol masers in low-mass star formation regions

2017 ◽  
Vol 13 (S336) ◽  
pp. 33-36
Author(s):  
S. Kalenskii ◽  
S. Kurtz ◽  
P. Hofner ◽  
P. Bergman ◽  
C.M. Walmsley ◽  
...  
Keyword(s):  
Star Formation ◽  
Class I ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Brightness Temperatures ◽  
Push Forward ◽  
Low Mass ◽  
Methanol Masers ◽  
Star Formation Regions

AbstractWe present a review of the properties of Class I methanol masers detected in low-mass star forming regions (LMSFRs). These masers, henceforth called LMMIs, are associated with postshock gas in the lobes of chemically active outflows in LMSFRs NGC1333, NGC2023, HH25, and L1157. LMMIs share the main properties with powerful masers in regions of massive star formation and are a low-luminosity edge of the total Class I maser population. However, the exploration of just these objects may push forward the exploration of Class I masers, since many LMSFRs are located only 200–300 pc from the Sun, making it possible to study associated objects in detail. EVLA observations with a 0.2″ spatial resolution show that the maser images consist of unresolved or barely resolved spots with brightness temperatures up to 5 × 105 K. The results are “marginally” consistent with the turbulent model of maser emission.

scholarly journals Star Formation in Young Cluster NGC 1893

2007 ◽  
Vol 3 (S246) ◽  
pp. 73-74
Author(s):  
Saurabh Sharma ◽  
A. K. Pandey ◽  
D. K. Ojha ◽  
W. P. Chen ◽  
S. K. Ghosh ◽  
...  
Keyword(s):  
Star Formation ◽  
Narrow Band ◽  
Massive Stars ◽  
Broad Band ◽  
Archival Data ◽  
Mass Star ◽  
Star Forming ◽  
Multi Wavelength ◽  
Low Mass

AbstractWe have carried out a multi-wavelength study of the star forming region NGC 1893 to make a comprehensive exploration of the effects of massive stars on low mass star formation. Using deep optical U BV RI broad band, Hα narrow band photometry and slit-less spectroscopy along with archival data from the surveys such as 2MASS, MSX, IRAS and NVSS, we have studied the region to understand the star formation scenario in the region.

scholarly journals Recent Developments in Simulations of Low-mass Star Formation

2010 ◽  
Vol 6 (S270) ◽  
pp. 65-72
Author(s):  
Masahiro N. Machida
Keyword(s):  
Star Formation ◽  
Numerical Simulations ◽  
Formation Process ◽  
Molecular Clouds ◽  
Circumstellar Disks ◽  
Mass Star ◽  
Star Forming ◽  
Protostellar Jets ◽  
Recent Developments ◽  
Low Mass

AbstractIn star forming regions, we can observe different evolutionary stages of various objects and phenomena such as molecular clouds, protostellar jets and outflows, circumstellar disks, and protostars. However, it is difficult to directly observe the star formation process itself, because it is veiled by the dense infalling envelope. Numerical simulations can unveil the star formation process in the collapsing gas cloud. Recently, some studies showed protostar formation from the prestellar core stage, in which both molecular clouds and protostars are resolved with sufficient spatial resolution. These simulations showed fragmentation and binary formation, outflow and jet driving, and circumstellar disk formation in the collapsing gas clouds. In addition, the angular momentum transfer and dissipation process of the magnetic field in the star formation process were investigated. In this paper, I review recent developments in numerical simulations of low-mass star formation.

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