Continuum emission from the star-forming regions Cepheus A and B

1990 ◽  
Vol 352 ◽  
pp. 636 ◽  
Author(s):  
M. A. Gordon
Keyword(s):  
Continuum Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Cepheus A

scholarly journals Velocity profiles of [CII], [CI], CO, and [OI] and physical conditions in four star-forming regions in the Large Magellanic Cloud

2019 ◽  
Vol 621 ◽  
pp. A62 ◽  
Author(s):  
Yoko Okada ◽  
Rolf Güsten ◽  
Miguel Angel Requena-Torres ◽  
Markus Röllig ◽  
Jürgen Stutzki ◽  
...  
Keyword(s):  
Physical Properties ◽  
High Redshift ◽  
Line Emission ◽  
Chemical Species ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Continuum Emission ◽  
Line Profiles ◽  
Star Forming ◽  
Star Forming Regions

Aims. The aim of our study is to investigate the physical properties of the star-forming interstellar medium (ISM) in the Large Magellanic Cloud (LMC) by separating the origin of the emission lines spatially and spectrally. The LMC provides a unique local template to bridge studies in the Galaxy and high redshift galaxies because of its low metallicity and proximity, enabling us to study the detailed physics of the ISM in spatially resolved individual star-forming regions. Following Okada et al. (Okada, Y., Requena-Torres, M. A., Güsten, R., et al. 2015, A&A, 580, A54), we investigate different phases of the ISM traced by carbon-bearing species in four star-forming regions in the LMC, and model the physical properties using the KOSMA-τ PDR model. Methods. We mapped 3–13 arcmin2 areas in 30 Dor, N158, N160, and N159 along the molecular ridge of the LMC in [C II] 158 μm with GREAT on board SOFIA. We also observed the same area with CO(2-1) to (6-5), 13CO(2-1) and (3-2), [C I] 3P1–3P0 and 3P2–3P1 with APEX. For selected positions in N159 and 30 Dor, we observed [O I] 145 μm and [O I] 63 μm with upGREAT. All spectra are velocity resolved. Results. In all four star-forming regions, the line profiles of CO, 13CO, and [C I] emission are similar, being reproduced by a combination of Gaussian profiles defined by CO(3-2), whereas [C II] typically shows wider line profiles or an additional velocity component. At several positions in N159 and 30 Dor, we observed the velocity-resolved [O I] 145 and 63 μm lines for the first time. At some positions, the [O I] line profiles match those of CO, at other positions they are more similar to the [C II] profiles. We interpret the different line profiles of CO, [C II] and [O I] as contributions from spatially separated clouds and/or clouds in different physical phases, which give different line ratios depending on their physical properties. We modeled the emission from the CO, [C I], [C II], and [O I] lines and the far-infrared continuum emission using the latest KOSMA-τ PDR model, which treats the dust-related physics consistently and computes the dust continuum SED together with the line emission of the chemical species. We find that the line and continuum emissions are not well-reproduced by a single clump ensemble. Toward the CO peak at N159 W, we propose a scenario that the CO, [C II], and [O I] 63 μm emission are weaker than expected because of mutual shielding among clumps.

scholarly journals Protostellar Outflows at the EarliesT Stages (POETS)

2018 ◽  
Vol 619 ◽  
pp. A107 ◽  
Author(s):  
A. Sanna ◽  
L. Moscadelli ◽  
C. Goddi ◽  
V. Krishnan ◽  
F. Massi
Keyword(s):  
Spectral Index ◽  
Young Stars ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Stellar Winds ◽  
Distance Measurements ◽  
Very Large Array ◽  
Star Forming ◽  
Continuum Source ◽  
Star Forming Regions

Context. Weak and compact radio continuum and H2O masers are preferred tracers of the outflow activity nearby very young stars. Aims. We want to image the centimeter free–free continuum emission in the range 1–7 cm (26–4 GHz), which arises in the inner few 1000 au from those young stars also associated with bright H2O masers. We seek to study the radio continuum properties in combination with the H2O maser kinematics to quantify the outflow energetics powered by single young stars. Methods. We made use of the Karl G. Jansky Very Large Array (VLA) in the B configuration at K band and the A configuration at both Ku and C bands in order to image the radio continuum emission toward 25 H2O maser sites with an angular resolution and thermal rms on the order of 0.′′1 and 10 μJy beam−1, respectively. These targets add to our pilot study of 11 maser sites previously presented. The sample of H2O maser sites was selected among those regions that have accurate distance measurements, obtained through maser trigonometric parallaxes, and H2O maser luminosities in excess of 10−6 L⊙. Results. We present high-resolution radio continuum images of 33 sources belonging to 25 star-forming regions. In each region, we detect radio continuum emission within a few 1000 au of the H2O masers’ position; 50% of the radio continuum sources are associated with bolometric luminosities exceeding 5 × 103 L⊙, including W33A and G240.32 + 0.07. We provide a detailed spectral index analysis for each radio continuum source, based on the integrated fluxes at each frequency, and produce spectral index maps with the multifrequency synthesis deconvolution algorithm of CASA. The radio continuum emission traces thermal bremsstrahlung in (proto)stellar winds and jets that have flux densities at 22 GHz below 3 mJy and spectral index values between − 0.1 and 1.3. We prove a strong correlation (r > 0.8) between the radio continuum luminosity (Lrad) and the H2O maser luminosity (LH2O) of (L8 GHz∕mJy kpc2) = 103.8 × (LH2O L⊙)0.74. This power-law relation is similar to that between the radio continuum and bolometric luminosities, which confirms earlier studies. Since H2O masers are excited through shocks driven by (proto)stellar winds and jets, these results provide support to the idea that the radio continuum emission around young stars is dominated by shock ionization, and this holds over several orders of magnitude of stellar luminosites (1–105 L⊙).

scholarly journals The time evolution of dusty protoplanetary disc radii: observed and physical radii differ

2019 ◽  
Vol 486 (4) ◽  
pp. 4829-4844 ◽  
Author(s):  
Giovanni P Rosotti ◽  
Marco Tazzari ◽  
Richard A Booth ◽  
Leonardo Testi ◽  
Giuseppe Lodato ◽  
...  
Keyword(s):  
Outer Part ◽  
Theoretical Models ◽  
Outer Edge ◽  
Continuum Emission ◽  
Multiple Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dust Distribution ◽  
Dust Grain ◽  
Dust Grain Growth

ABSTRACT Protoplanetary disc surveys conducted with Atacama Large Millimetre Array (ALMA) are measuring disc radii in multiple star-forming regions. The disc radius is a fundamental quantity to diagnose whether discs undergo viscous spreading, discriminating between viscosity or angular momentum removal by winds as drivers of disc evolution. Observationally, however, the sub-mm continuum emission is dominated by the dust, which also drifts inwards, complicating the picture. In this paper we investigate, using theoretical models of dust grain growth and radial drift, how the radii of dusty viscous protoplanetary discs evolve with time. Despite the existence of a sharp outer edge in the dust distribution, we find that the radius enclosing most of the dust mass increases with time, closely following the evolution of the gas radius. This behaviour arises because, although dust initially grows and drifts rapidly on to the star, the residual dust retained on Myr time-scales is relatively well coupled to the gas. Observing the expansion of the dust disc requires using definitions based on high fractions of the disc flux (e.g. 95 per cent) and very long integrations with ALMA, because the dust grains in the outer part of the disc are small and have a low sub-mm opacity. We show that existing surveys lack the sensitivity to detect viscous spreading. The disc radii they measure do not trace the mass radius or the sharp outer edge in the dust distribution, but the outer limit of where the grains have significant sub-mm opacity. We predict that these observed radii should shrink with time.

scholarly journals STATISTICAL ANALYSIS OF WATER MASERS IN STAR-FORMING REGIONS: CEPHEUS A AND W75 N

2010 ◽  
Vol 715 (1) ◽  
pp. 132-142 ◽  
Author(s):  
L. Uscanga ◽  
J. Cantó ◽  
J. F. Gómez ◽  
G. Anglada ◽  
J. M. Torrelles ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Star Forming ◽  
Star Forming Regions ◽  
Water Masers ◽  
Cepheus A

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.

Dust Trapping and Coagulation in Protoplanetary Disks

2018 ◽  
Vol 14 (S345) ◽  
pp. 355-357
Author(s):  
Ya-Ping Li
Keyword(s):  
Protoplanetary Disks ◽  
Large Family ◽  
Continuum Emission ◽  
Nearby Star ◽  
Dust Trapping ◽  
Star Forming ◽  
Star Forming Regions ◽  
Hydrodynamical Simulations ◽  
Two Fluid ◽  
Key Parameter

AbstractIn this work, we carry out two-fluid (gas+dust) hydrodynamical simulations on a large family of models in order to study the dust coagulation and the dust-gas dynamical processes in protoplanetary disks. Our theoretical effort is guided by the observational results of disks in nearby star forming regions at sub-millimeter and millimeter (mm) wavelengths. By a systematic comparison with the continuum emission at several mm bands from ALMA observations, we find that ringed structures are predicated in the unresolved faint disks for those with mm spectral indexes as low as about 2.0. Our parameter exploration can also be used to constrain the fragmentation velocity, one key parameter of the dust coagulation model, and some other disk parameters.

scholarly journals High-mass Star Formation in the Regions IRAS 19217+1651 and 23151+5912

2012 ◽  
Vol 8 (S287) ◽  
pp. 182-183
Author(s):  
V. Migenes ◽  
I. T. Rodríguez ◽  
M. A. Trinidad
Keyword(s):  
Water Vapor ◽  
Star Formation ◽  
Spatial Resolution ◽  
High Sensitivity ◽  
High Mass ◽  
Continuum Emission ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions

AbstractWe present and discuss VLA-EVLA high-sensitivity and spatial resolution observations of Water Vapor MASERs and continuum emission towards two sources that have been proposed in the literature to be high-mass star forming regions: IRAS 19217+1651 and 23151+5912. Our results indicate the presence of disks which can confirm that these regions are high-mass star forming regions.

scholarly journals High-resolution, 3D radiative transfer modeling of M51

2014 ◽  
Vol 10 (S309) ◽  
pp. 310-310
Author(s):  
Ilse De Looze ◽  
Jacopo Fritz ◽  
Maarten Baes ◽  
Keyword(s):  
High Resolution ◽  
Radiative Transfer ◽  
3D Models ◽  
Continuum Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Local Character ◽  
Stellar Radiation ◽  
The Face ◽  
A New Technique

AbstractWe present a new technique developed to model the radiative transfer (RT) effects in nearby face-on galaxies. The face-on perspective provides insight into the star-forming regions and clumpy structure, imposing the need for high-resolution 3D models to recover the asymmetric stellar and dust geometries observed in galaxies. RT modeling of the continuum emission of stars and its interaction with the embedding dust in a galaxy's interstellar medium enables a self-consistent study of the main dust heating mechanisms in galaxies. The main advantage of RT calculations is the non-local character of dust heating that can be addressed by tracing the propagation of stellar radiation through the dusty galaxy medium.

scholarly journals Submillimetre polarimetric observations of magnetic fields in star-forming regions

2007 ◽  
Vol 3 (S243) ◽  
pp. 63-70
Author(s):  
Rachel L. Curran ◽  
Antonio Chrysostomou ◽  
Brenda C. Matthews
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Cumulative Distribution ◽  
High Mass ◽  
Continuum Emission ◽  
Field Pattern ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
The Magnetic Field

AbstractSubmillimetre imaging polarimetry is one of the most powerful tools at present for studying magnetic fields in star-forming regions, and the only way to gain significant information on the structure of these fields. We present analysis of the largest sample (to date) of both high- and low-mass star-forming regions observed using this technique. A variety of magnetic field morphologies are observed, with no single field morphology favoured. Both the continuum emission morphologies and the field morphologies are generally more complex for the high-mass sample than the low-mass sample. The large scale magnetic field (observed with the JCMT; 14″ resolution) of NGC1333 IRAS2 is interpreted to be weak (compared to the energetic contributions due to turbulence) from the random field pattern observed. On smaller scales (observed with the BIMA array; 3″ resolution) the field is observed to be almost radial, consistent with the polarisation nulls in the JCMT data – suggesting that on smaller scales, the field may be more important to the star formation process. An analysis of the magnetic field direction and the jet/outflow axis is also discussed. Cumulative distribution functions of the difference between the mean position angle of the magnetic field vectors and the jet/outflow axis reveal no correlation. However, visual inspection of the maps reveal alignment of the magnetic field and jet/outflow axis in 7 out of 15 high-mass regions and 3 out of 8 low-mass regions.

scholarly journals A Highly-collimated Water Maser Bipolar Outflow in the Cepheus A HW3d Massive Protostellar Object

2012 ◽  
Vol 8 (S287) ◽  
pp. 141-145
Author(s):  
James O. Chibueze ◽  
Hiroshi Imai ◽  
Daniel Tafoya ◽  
Toshihiro Omodaka ◽  
Osamu Kameya ◽  
...  
Keyword(s):  
Strong Support ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Very Large Array ◽  
Star Forming ◽  
Bipolar Outflow ◽  
Long Baseline ◽  
Cepheus A ◽  
Continuum Data ◽  
Water Maser

AbstractWe report the results of multi-epoch very long baseline interferometry (VLBI) water (H2O) maser observations carried out with the VLBI Exploration of Radio Astrometry (VERA) toward the HW3d object within the Cepheus A star-forming region. We measured proper motions of 30 water maser features, tracing a compact bipolar outflow. This outflow is highly collimated, extending through ~400 mas (290 AU), and having a typical proper motion velocity of ~6 mas yr−1 (~21 km s−1). The dynamical timescale of the outflow was estimated to be ~100 years, showing that the outflow is tracing a very early star-formation phase. Our results provide strong support that the HW3d object harbors an internal massive protostar, as previous observations suggested. In addition, we have analyzed Very Large Array (VLA) archive 1.3 cm continuum data of the 1995 and 2006 epochs obtained towards Cepheus A. These results indicate possible different protostars around HW3d and/or strong variability in its radio continuum emission.

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