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 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 The Formation and Destruction of Molecular Clouds and Galactic Star Formation

2015 ◽  
Vol 11 (S315) ◽  
pp. 61-68
Author(s):  
Shu-ichiro Inutsuka ◽  
Tsuyoshi Inoue ◽  
Kazunari Iwasaki ◽  
Takashi Hosokawa ◽  
Masato I. N. Kobayashi
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Massive Stars ◽  
Age Determination ◽  
Mass Function ◽  
Mass Star ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions

AbstractWe discuss an overall picture of star formation in the Galaxy. Recent high-resolution magneto-hydrodynamical simulations of two-fluid dynamics with cooling/heating and thermal conduction have shown that the formation of molecular clouds requires multiple episodes of supersonic compression. This finding enables us to create a new scenario of molecular cloud formation through interacting shells or bubbles on galactic scales. We estimate the ensemble-averaged growth rate of individual molecular clouds, and predict the associated cloud mass function. This picture naturally explains the accelerated star formation over many million years that was previously reported by stellar age determination in nearby star forming regions. The recent claim of cloud-cloud collisions as a mechanism for forming massive stars and star clusters can be naturally accommodated in this scenario. This explains why massive stars formed in cloud-cloud collisions follows the power-law slope of the mass function of molecular cloud cores repeatedly found in low-mass star forming regions.

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 A VLBI Study of H2O Maser Spots Associated with a Molecular Outflow ρ Oph-East

1994 ◽  
Vol 140 ◽  
pp. 60-61
Author(s):  
Takahiro Iwata ◽  
Hiroshi Takaba ◽  
Kin-Ya Matsumoto ◽  
Seiji Kameno ◽  
Noriyuki Kawaguchi
Keyword(s):  
Molecular Cloud ◽  
Observational Evidence ◽  
Molecular Gas ◽  
Mass Star ◽  
Dynamical Interaction ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Outflow ◽  
Low Mass ◽  
A Site

A molecular outflow is one of the most conspicuous active phenomena associated with protostars, and the kinetic energy of its outflowing mass is as large as that of random motions of ambient molecular cloud, which suggests that outflow has dynamically influence on ambient molecular gas. Possible observational evidence which suggests the existence of dynamical interaction between molecular outflow and ambient molecular cloud has been detected in several star forming regions (Fukui et al. 1986; Iwata et al. 1988). Recent detections of H2O maser emission associated with low-mass protostars (e.g. Comoretto et al. 1990) also suggest that there still exist active phenomena in the low-mass star forming regions.Molecular outflow ρ Oph-East, discovered toward a low-mass protostar IRAS 16293-2422 (Fukui et al. 1986), has been known as a site of dynamical interaction between molecular outflowing gas and ambient molecular cloud by CO and NH3 observation (Mizuno et al. 1990). Existence of several strong H2O maser spots (Wilking & Claussen 1987; Wotten 1989; Terebey et al. 1992) also suggests that active phenomena are occurring in this region. In this paper, we report our result of H2O maser observation for molecular outflow ρ Oph-East with milli-arcsecond resolution by VLBI.

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 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.

scholarly journals The effects of ionizing radiation on star formation in molecular clouds

1991 ◽  
Vol 147 ◽  
pp. 391-393
Author(s):  
F. Bertoldi ◽  
C.F. McKee ◽  
R.I. Klein
Keyword(s):  
Star Formation ◽  
Ionizing Radiation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Massive Star ◽  
Mass Star ◽  
Massive Star Formation ◽  
Before And After ◽  
Low Mass ◽  
Gravitational Stability

The gravitational stability of molecular cloud clumps before and after the onset of massive star formation is discussed. We suggest that the most massive clumps are magnetically supercritical but gravitationally stabilized by the hydromagnetic turbulence caused by FUV photoionization-regulated low-mass star formation in their interiors. The ionizing radiation of an O star can trigger star formation in initially sub- and supercritical clumps.

scholarly journals Masers in SGR B2: Sites of Star-Forming Regions

1987 ◽  
Vol 115 ◽  
pp. 161-163 ◽  
Author(s):  
J. B. Whiteoak ◽  
F. F. Gardner ◽  
J. R. Forster ◽  
P. Palmer ◽  
V. Pankonin
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Large Scale ◽  
Star Forming ◽  
Star Forming Regions ◽  
H Ii Region ◽  
Cloud Complex

H2CO and OH masers in the H II-region/molecular-cloud complex Sgr B2 have been observed with the VLA and combined with other observations of OH and H2O masers. It is found that groups of the masers and compact continuum components are located along a north-south line extending across the complex. The overall alignment suggests that star formation is being triggered by a single large-scale event such as an interaction between molecular clouds.

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.

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