scholarly journals Dynamical processes in star forming regions: feedback and turbulence generation

2006 ◽  
Vol 2 (S237) ◽  
pp. 165-171
Author(s):  
John Bally
Keyword(s):  
Kinetic Energy ◽  
Massive Stars ◽  
Young Stellar Objects ◽  
Stellar Winds ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Cloud Cores ◽  
Turbulence Generation

AbstractYoung stellar objects (YSOs) inject large amounts of momentum and kinetic energy into their surroundings. Feedback from low mass YSOs is dominated by their outflows. However, as stellar mass increases, UV photo-heating and ionization play increasingly important roles. Massive stars produce powerful stellar winds and explode as supernovae within 3 – 40 Myr after birth. While low-mass protostellar feedback can drive turbulence in cloud cores and even disrupt the star forming environment, feedback from massive stars plays important roles in the generation of cloud structure and motions in the entire ISM.

scholarly journals Physical Properties of Molecular Envelopes in Low-Mass Star-Forming Regions

2000 ◽  
Vol 197 ◽  
pp. 61-70
Author(s):  
Nagayoshi Ohashi
Keyword(s):  
Physical Properties ◽  
Young Stellar Objects ◽  
Mass Star ◽  
Narrow Line ◽  
Stellar Objects ◽  
Velocity Pattern ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Line Widths

We have carried out interferometric observations of pre-protostellar and protostellar envelopes in Taurus. Protostellar envelopes are dense gaseous condensations with young stellar objects or protostars, while pre-protostellar envelopes are those without any known young stellar objects. Five pre-protostellar envelopes have been observed in CCS JN=32–21, showing flattened and clumpy structures of the envelopes. The observed CCS spectra show moderately narrow line widths, ~0.1 to ~0.35 km s–1. One pre-protostellar envelope, L1544, shows a remarkable velocity pattern, which can be explained in terms of infall and rotation. Our C18O J=1–0 observations of 8 protostellar envelopes show that they have also flattened structures like pre-protostellar envelopes but no clumpy structures. Four out the eight envelopes show velocity patterns that can be explained by motions of infall (and rotation). Physical properties of pre-protostellar and protostellar envelopes are discussed in detail.

scholarly journals Photometric and spectroscopic studies of very low mass YSOs and young Brown Dwarfs in S106

2006 ◽  
Vol 2 (S237) ◽  
pp. 457-457
Author(s):  
Yumiko Oasa
Keyword(s):  
Massive Star ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Spectroscopic Studies ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Hii Region ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

Young brown dwarfs have been identified in a significant population in various star forming regions. Some deep surveys have yielded less massive objects with planetary-mass (e.g., Oasa et al. 1999; Lucas & Roche 2000). Nevertheless, it is not yet clear how abundant these very low-mass objects are formed. S106 is one of the nearest massive star-forming regions associated with prominent bipolar nebulae and an HII region. We have conducted near-infrared photometric and spectroscopic observations of very low-mass young stellar objects (YSOs) in the S106 region.

scholarly journals Chemistry in the Envelopes around Massive Young Stars

2000 ◽  
Vol 197 ◽  
pp. 97-112 ◽  
Author(s):  
Ewine F. van Dishoeck ◽  
Floris F. S. van der Tak
Keyword(s):  
Young Stars ◽  
Physical Models ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Chemical Models ◽  
Low Mass

Recent observational studies of intermediate- and high-mass star-forming regions at submillimeter and infrared wavelengths are reviewed, and chemical diagnostics of the different physical components associated with young stellar objects are summarized. Procedures for determining the temperature, density and abundance profiles in the envelopes are outlined. A detailed study of a set of infrared-bright massive young stars reveals systematic increases in the gas/solid ratios, the abundances of evaporated molecules, and the fraction of heated ices with increasing temperature. Since these diverse phenomena involve a range of temperatures from < 100 K to 1000 K, the enhanced temperatures must be communicated to both the inner and outer parts of the envelopes. This ‘global heating’ plausibly results from the gradual dispersion of the envelopes with time. Similarities and differences with low-mass YSOs are discussed. The availability of accurate physical models will allow chemical models of ice evaporation followed by ‘hot core’ chemistry to be tested in detail.

scholarly journals The Circumstellar Environment of Embedded Massive Stars

2002 ◽  
Vol 12 ◽  
pp. 143-145 ◽  
Author(s):  
Lee G. Mundy ◽  
Friedrich Wyrowski ◽  
Sarah Watt
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Low Mass Stars ◽  
Submillimeter Wavelength ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Circumstellar Environments ◽  
Near Future

Millimeter and submillimeter wavelength images of massive star-forming regions are uncovering the natal material distribution and revealing the complexities of their circumstellar environments on size scales from parsecs to 100’s of AU. Progress in these areas has been slower than for low-mass stars because massive stars are more distant, and because they are gregarious siblings with different evolutionary stages that can co-exist even within a core. Nevertheless, observational goals for the near future include the characterization of an early evolutionary sequence for massive stars, determination if the accretion process and formation sequence for massive stars is similar to that of low-mass stars, and understanding of the role of triggering events in massive star formation.

scholarly journals Far-IR Spectrophotometry of HH Flows with the ISO Long-Wavelength Spectrometer

1997 ◽  
Vol 182 ◽  
pp. 111-120
Author(s):  
R. Liseau ◽  
T. Giannini ◽  
B. Nisini ◽  
P. Saraceno ◽  
L. Spinoglio ◽  
...  
Keyword(s):  
Mass Loss ◽  
Line Emission ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Shock Models ◽  
Ir Spectrophotometry ◽  
Hh Objects ◽  
Loss Rates

Full Iso-Lws spectral scans between about 45 to 190 μm of 17 individual HH objects in 7 star forming regions have revealed essentially only [O I] 63 μm line emission, implying that the Fircooling of these objects is totally dominated by this line alone. In this case, J-shock models can be used to determine the mass loss rates of the HH exciting sources. These mass loss rates are in reasonably good agreement with those estimated for the accompanying CO flows, providing first observational evidence that HH and molecular flows are driven by the same agent. The Lmech – Lbol relation, based on our results with the Lws, implies that young stellar objects of lower mass are loosing mass at relatively higher rates than their more massive counterparts.

Magnetic Fields and Disks in Star-forming Regions

1993 ◽  
Vol 10 (3) ◽  
pp. 247-249 ◽  
Author(s):  
C.M. Wright ◽  
D.K. Aitken ◽  
C.H. Smith ◽  
P.F. Roche
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Transverse Component ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Molecular Outflow ◽  
The Magnetic Field

AbstractThe star-formation process is an outstanding and largely unsolved problem in astrophysics. The role of magnetic fields is unclear but is widely considered to be important at all stages of protostellar evolution, from cloud collapse to ZAMS. For example, in some hydromagnetic models, the field may assist in removing angular momentum, thereby driving accretion and perhaps bipolar outflows.Spectropolarimetry between 8 and 13μm provides information on the direction of the transverse component of a magnetic field through the alignment of dust grains. We present results of 8–13μm spectropolarimetric observations of a number of bipolar molecular outflow sources, and compare the field directions observed with the axes of the outflows and putative disk-like structures observed to be associated with some of the objects. There is a strong correlation, though so far with limited statistics, between the magnetic field and disk orientations. We compare our results with magnetic field configurations predicted by current models for hydromagnetically driven winds from the disks around Young Stellar Objects (YSOs). Our results appear to argue against the Pudritz and Norman model and instead seem to support the Uchida and Shibata model.

scholarly journals GAMMA-RAY EMISSION FROM MASSIVE STAR FORMING REGIONS

2008 ◽  
Vol 17 (10) ◽  
pp. 1889-1894 ◽  
Author(s):  
A. T. ARAUDO ◽  
G. E. ROMERO ◽  
V. BOSCH-RAMON ◽  
J. M. PAREDES
Keyword(s):  
Gamma Ray ◽  
Surrounding Medium ◽  
Strong Shock ◽  
High Energy ◽  
Young Stellar Objects ◽  
Present Contribution ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Impact

Recent radio observations support a picture for star formation where there is accretion of matter onto a central protostar with the ejection of molecular outflows that can affect the surrounding medium. The impact of a supersonic outflow on the ambient gas can produce a strong shock that could accelerate particles up to relativistic energies. Strong evidence for this has been the detection of nonthermal radio emission coming from the jet termination region of some young massive stars. In the present contribution, we study the possible high-energy emission due to the interaction of relativistic particles, electrons and protons, with the magnetic, photon and matter fields inside a giant molecular cloud. Electrons lose energy via relativistic Bremsstrahlung, synchrotron radiation and inverse Compton interactions, and protons cool mainly through inelastic collisions with atoms in the cloud. We conclude that some massive young stellar objects (YSOs) might be detectable at gamma-rays by next generation instruments, both satellite-borne and ground based.

scholarly journals A Systematic Study of X-Ray Flares from Low-Mass Young Stellar Objects in the $\rho$ Ophiuchi Star-Forming Region with Chandra

2003 ◽  
Vol 55 (3) ◽  
pp. 653-681 ◽  
Author(s):  
Kensuke Imanishi ◽  
Hiroshi Nakajima ◽  
Masahiro Tsujimoto ◽  
Katsuji Koyama ◽  
Yohko Tsuboi
Keyword(s):  
Systematic Study ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
X Ray ◽  
Star Forming ◽  
Low Mass ◽  
Rho Ophiuchi

scholarly journals The extended solar neighborhood: precision astrometry from the Pan-STARRS 1 3π Survey

2007 ◽  
Vol 3 (S248) ◽  
pp. 553-559 ◽  
Author(s):  
E. A. Magnier ◽  
M. Liu ◽  
D. G. Monet ◽  
K. C. Chambers
Keyword(s):  
Solar Neighborhood ◽  
Dynamical Structure ◽  
Nearby Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Low Mass ◽  
Single Epoch ◽  
Insight Into

AbstractThe Pan-STARRS pathfinding telescope PS1 will begin a major set of surveys starting in 2008, and lasting for 3.5 years. One of these, the PS1 3π Survey, will repeatedly observe the entire sky north of −30 degrees, visiting every position 12 times in each of 5 filters. With single-epoch astrometry of 10 milliarcseconds, these observations will yield parallaxes for stars within 100 pc and proper motions out to several hundred pc. The result will be an unprecedented view on nearby stellar populations and insight into the dynamical structure of the local portions of the Galaxy. One exciting science product will be a volume-limited sample of nearby low-mass objects including thousands of L dwarfs, hundreds of T dwarfs, and perhaps even cooler sub-stellar objects. Another project will use proper-motion measurements to improve the membership of nearby star forming regions.

scholarly journals A (Sub)Millimeter survey of massive star-forming regions identified by the ISOPHOT Serendipity Survey (ISOSS)

2006 ◽  
Vol 2 (S237) ◽  
pp. 424-424
Author(s):  
Martin Hennemann ◽  
Stephan M. Birkmann ◽  
Oliver Krause ◽  
Dietrich Lemke
Keyword(s):  
Molecular Cloud ◽  
Massive Star ◽  
Infrared Emission ◽  
Evolutionary Stage ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Low Levels ◽  
Cloud Cores ◽  
Mass Case

AbstractA sample of potential massive starforming regions identified at 170 m by ISO was observed in the submillimeter and millimeter regime. These observations allow us to infer physical properties of the molecular cloud cores. Two sources are presented in detail: ISOSS J23053+5953 and J183640221 show viable candidates for massive protocluster cores. Our analysis shows very low temperatures and low levels of turbulence of the major mass fraction in the molecular cloud cores besides active star formation at an early evolutionary stage. These conditions seem similar to the low mass case and may precede phases of luminous infrared emission observed towards young massive protostars.

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