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 Outflows and Turbulence in Young Stellar Clusters — An Observer's View

2010 ◽  
Vol 6 (S270) ◽  
pp. 287-290
Author(s):  
Héctor G. Arce
Keyword(s):  
Point Of View ◽  
Young Stellar Objects ◽  
Stellar Clusters ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Numerical Studies ◽  
Formation Efficiency ◽  
The Impact ◽  
Cloud Complex

AbstractRecent numerical studies have focused their interest on the impact outflows have on the cloud's turbulence. The contradictory results obtained by these studies indicate that it is essential for observers to provide the required data to constrain the models. Here we discuss the impact of outflows on the environment surrounding clusters of young stellar objects, from an observer's point of view. We have conducted several studies of outflows in different active star-forming regions. In all cases it is clear that outflows have the power to sustain the observed turbulence in the gas surrounding protostellar clusters. We investigate whether there is a correlation between outflow strength and star formation efficiency, as predicted by numerical simulations, for six different regions in the Perseus molecular cloud complex. We argue that results of other recent studies that use CO line maps to study the turbulence driving length should not be used to discard outflows as major drivers of turbulence in clusters.

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.

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.

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.

Gamma-ray Observation of Nearby Starburst Galaxy IC342

2005 ◽  
Vol 20 (14) ◽  
pp. 3167-3169
Author(s):  
◽  
Tomoyuki Nagai ◽  
Vladimir Vassiliev
Keyword(s):  
Cosmic Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Critical Parameters ◽  
Starburst Galaxy ◽  
Star Forming ◽  
High Energy Cosmic Rays ◽  
Star Forming Regions ◽  
Progenitor Stars ◽  
Current Paradigm

Regions with high star formation rates (SFR) in starburst galaxies (SBGs) are frequently accompanied by high density clouds of interstellar matter (ISM). This may create nearly perfect conditions for generating diffuse gamma-ray radiation as high energy cosmic rays accelerated in supernovae explosions of massive progenitor stars interact with the ambient protons. If the current paradigm that supernovae are the origin sites of high energy cosmic rays is valid, then the star forming regions rich in supernovae may become the laboratories to test and study this phenomenon. The gamma-ray luminosity of these extragalactic objects is suppressed by a large distance factor compared to supernovae in our own galaxy. However, flux estimates indicate that if star bursting regions have a proper combination of critical parameters (intersteller medium density, age, size, supernova rate, magnetic field strength) the cumulative enhancement of the gamma-ray luminosity resulting from multiple explosions of supernovae into dense ISM may generate an observable flux for nearby SBGs such as M82, IC342. A search for TeV gamma-ray emission from IC342 was conducted with the Whipple 10m gamma-ray telescope from September 2002 to March 2004.

scholarly journals Identifying young stellar objects in nine Large Magellanic Cloud star-forming regions

2012 ◽  
Vol 542 ◽  
pp. A66 ◽  
Author(s):  
L. R. Carlson ◽  
M. Sewiło ◽  
M. Meixner ◽  
K. A. Romita ◽  
B. Lawton
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals SK 1: A possible case of triggered star formation in perseus

2006 ◽  
Vol 2 (S237) ◽  
pp. 217-221
Author(s):  
Miriam Rengel ◽  
Klaus Hodapp ◽  
Jochen Eislöffel
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Thermal Emission ◽  
Young Stellar Objects ◽  
Wide Field ◽  
Dust Shell ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
Suitable Target

AbstractAccording to a triggered star formation scenario (e.g. Martin-Pintado & Cernicharo 1987) outflows powered by young stellar objects shape the molecular clouds, can dig cavities, and trigger new star formation. NGC 1333 is an active site of low- and intermediate star formation in Perseus and is a suggested site of self-regulated star formation (Norman & Silk 1980). Therefore it is a suitable target for a study of triggered star formation (e.g. Sandell & Knee 2001, SK1). On the other hand, continuum sub-mm observations of star forming regions can detect dust thermal emission of embedded sources (which drive outflows), and further detailed structures.Within the framework of our wide-field mapping of star formation regions in the Perseus and Orion molecular clouds using SCUBA at 850 and 450 μm, we mapped NCG 1333 with an area of around 14′× 21′. The maps show more structure than the previous maps of the region observed in sub-mm. We have unveiled the known embedded SK 1 source (in the dust shell of the SSV 13 ridge) and detailed structure of the region, among some other young protostars.In agreement with the SK 1 observations, our map of the region shows lumpy filaments and shells/cavities that seem to be created by outflows. The measured mass of SK 1 (~0.07 M) is much less than its virial mass (~0.2-1 M). Our observations support the idea of SK 1 as an event triggered by outflow-driven shells in NGC 1333 (induced by an increase in gas pressure and density due to radiation pressure from the stellar winds that have presumably created the dust shell). This kind of evidences provides a more thorough understanding of the star formation regulation processes.

scholarly journals A timeline for massive star-forming regions via combined observation of o-H2D+ and N2D+

2019 ◽  
Vol 621 ◽  
pp. L7 ◽  
Author(s):  
A. Giannetti ◽  
S. Bovino ◽  
P. Caselli ◽  
S. Leurini ◽  
D. R. G. Schleicher ◽  
...  
Keyword(s):  
Free Fall ◽  
Young Stellar Objects ◽  
High Mass ◽  
Continuum Emission ◽  
State Transitions ◽  
Temperature Sensitive ◽  
Evolutionary Stage ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions

Context. In cold and dense gas prior to the formation of young stellar objects, heavy molecular species (including CO) are accreted onto dust grains. Under these conditions H3+ and its deuterated isotopologues become more abundant, enhancing the deuterium fraction of molecules such as N2H+ that are formed via ion-neutral reactions. Because this process is extremely temperature sensitive, the abundance of these species is likely linked to the evolutionary stage of the source. Aims. We investigate how the abundances of o-H2D+ and N2D+ vary with evolution in high-mass clumps. Methods. We observed with APEX the ground-state transitions of o-H2D+ near 372 GHz, and N2D+(3–2) near 231 GHz for three massive clumps in different evolutionary stages. The sources were selected within the G351.77–0.51 complex to minimise the variation of initial chemical conditions, and to remove distance effects. We modelled their dust continuum emission to estimate their physical properties, and also modelled their spectra under the assumption of local thermodynamic equilibrium to calculate beam-averaged abundances. Results. We find an anticorrelation between the abundance of o-H2D+ and that of N2D+, with the former decreasing and the latter increasing with evolution. With the new observations we are also able to provide a qualitative upper limit to the age of the youngest clump of about 105 yr, comparable to its current free-fall time. Conclusions. We can explain the evolution of the two tracers with simple considerations on the chemical formation paths, depletion of heavy elements, and evaporation from the grains. We therefore propose that the joint observation and the relative abundance of o-H2D+ and N2D+ can act as an efficient tracer of the evolutionary stages of the star-formation process.

Lunar Occultations of Young Stellar Objects in the Taurus and Ophiuchus Star Forming Regions

1994 ◽  
pp. 416-418
Author(s):  
A. Richichi ◽  
M. Haas ◽  
CH. Leinert ◽  
R. Jameson ◽  
D. Adams ◽  
...  
Keyword(s):  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions

scholarly journals NON-THERMAL EMISSION FROM GALACTIC JETS

2012 ◽  
Vol 08 ◽  
pp. 84-95
Author(s):  
VALENTÍ BOSCH-RAMON
Keyword(s):  
Gamma Ray ◽  
Thermal Emission ◽  
Galactic Nuclei ◽  
High Energy ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Thermal Emitters ◽  
Thermal Sources ◽  
High Energy Emission ◽  
The Universe

Jets are ubiquitous in the Universe. They are collimated outflows whose origin is associated to an accretion disc and a central object, and can be very powerful non-thermal emitters. Jets form in active galactic nuclei, gamma-ray bursts, microquasars, and young stellar objects. Galactic jets emitting non-thermal emission are typically associated to microquasars, although the jets of massive young stellar objects are also non-thermal sources. The production of non-thermal radiation, in particular radio synchrotron emission, is a clear indication that particle acceleration is taking place in the source, which hints to the generation of photons even at high energies. In this work, we will discuss the emitting sites in, or related to, microquasar jets, and briefly comment on the possibility of high-energy emission in jets from young stellar objects.

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