scholarly journals SiO Masers in the Star Forming Regions W51 IRS2 and Sgr B2 MD5

1987 ◽  
Vol 115 ◽  
pp. 178-178
Author(s):  
N. Ukita ◽  
T. Hasegawa ◽  
N. Kaifu ◽  
K.-I. Morita ◽  
S. Okumura ◽  
...  
Keyword(s):  
Star Formation ◽  
Excited States ◽  
Line Intensity ◽  
Massive Star ◽  
Massive Star Formation ◽  
Vibrationally Excited ◽  
Maser Emission ◽  
Star Forming ◽  
Star Forming Regions ◽  
Upper Limit

The maser emission of the J = 1-0 lines of SiO in vibrationally excited states has been detected in two regions of massive star formation, W51 IRS2 and Sgr B2 MD5. The SiO masers apparently coincide with strong H2O masers in each source within the uncertainties of < 5″. Their velocity ranges fall within those of the nearest H2O masers (Figure 1). In W51 IRS2 the maser emission is observed only in the v = 2 state, and the upper limit of the v = 1 line (3σ) is 1/15th of the v = 2 line intensity. The v = 1 emission found in Sgr B2 MD5 is five times stronger than the marginally detected v = 2 emission (Figure 2). Their luminosities are comparable to those from the corresponding maser in Orion.

scholarly journals OB stars towards NGC 6357 and NGC 6334

2017 ◽  
Vol 12 (S330) ◽  
pp. 341-342
Author(s):  
Delphine Russeil
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Proper Motions ◽  
Massive Star Formation ◽  
Ob Stars ◽  
Stellar Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ngc 6334

AbstractThe star forming regions NGC6334 and NGC6357 are amid the most active star-forming complexes of our Galaxy where massive star formation is occuring. Both complexes gather several HII regions but they exhibit different aspects: NGC6334 is characterised by a dense molecular ridge where recent massive star formation is obvious while NGC6357 is dominated by the action of the stellar cluster Pismis 24 which have shaped a large cavity. To understand and compare the formation of massive stars in these two regions requires to precise the distance and characterise the proper motions of the O to B3 stellar population in these regions.

scholarly journals The 44 GHz methanol maser line in massive star forming regions

2007 ◽  
Vol 3 (S242) ◽  
pp. 160-161
Author(s):  
P. Hofner ◽  
E. Jordan ◽  
E. Araya ◽  
S. Kurtz
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Star Formation ◽  
Present Evidence ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Maser Line

AbstractWe present the results of recent surveys in the 44GHz methanol maser line toward regions of massive star formation using the Haystack 37m telescope and the VLA. We discuss a possible shock origin of this maser line and present evidence for variability from multi-epoch observations of selected sources.

scholarly journals Structure of photodissociation fronts in star-forming regions revealed by Herschel observations of high-J CO emission lines

2018 ◽  
Vol 615 ◽  
pp. A129 ◽  
Author(s):  
C. Joblin ◽  
E. Bron ◽  
C. Pinto ◽  
P. Pilleri ◽  
F. Le Petit ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Massive Star ◽  
Line Emission ◽  
Massive Star Formation ◽  
Star Forming ◽  
Star Forming Regions ◽  
Key Species ◽  
Two Parameters ◽  
Co Emission

Context. In bright photodissociation regions (PDR) associated with massive star formation, the presence of dense “clumps” that are immersed in a less dense interclump medium is often proposed to explain the difficulty of models to account for the observed gas emission in high-excitation lines. Aims. We aim to present a comprehensive view of the modelling of the CO rotational ladder in PDRs, including the high-J lines that trace warm molecular gas at PDR interfaces. Methods. We observed the 12CO and 13CO ladders in two prototypical PDRs, the Orion Bar and NGC 7023 NW using the instruments onboard Herschel. We also considered line emission from key species in the gas cooling of PDRs (C+, O, and H2) and other tracers of PDR edges such as OH and CH+. All the intensities are collected from Herschel observations, the literature and the Spitzer archive and were analysed using the Meudon PDR code. Results. A grid of models was run to explore the parameter space of only two parameters: thermal gas pressure and a global scaling factor that corrects for approximations in the assumed geometry. We conclude that the emission in the high-J CO lines, which were observed up to Jup = 23 in the Orion Bar (Jup = 19 in NGC 7023), can only originate from small structures with typical thicknesses of a few 10−3 pc and at high thermal pressures (Pth ~ 108 K cm−3). Conclusions. Compiling data from the literature, we find that the gas thermal pressure increases with the intensity of the UV radiation field given by G0, following a trend in line with recent simulations of the photoevaporation of illuminated edges of molecular clouds. This relation can help to rationalise the analysis of high-J CO emission in massive star formation and provides an observational constraint for models which study stellar feedback on molecular clouds.

scholarly journals (Sub-)mm Interferometry in Massive Star Forming Regions

2004 ◽  
Vol 221 ◽  
pp. 191-198
Author(s):  
Henrik Beuther
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Massive Star Formation ◽  
Star Forming ◽  
Molecular Outflows ◽  
Star Forming Regions ◽  
New Instrument

(Sub-)mm interferometry is the most favorable technique to investigate the earliest stages of massive star formation. I will outline general applications in that field and discuss results of different sub-topics (hot core chemistry and massive molecular outflows). Furthermore, recent data obtained with the Submillimeter Array will be shown to present the unique capabilities of this new instrument. Finally, I will give a short outlook on the main physical topics of massive star formation to be tackled with (sub-)mm interferometry within the next decade.

scholarly journals Millimetre wavelength methanol masers survey towards massive star forming regions

2007 ◽  
Vol 3 (S242) ◽  
pp. 234-235
Author(s):  
T. Umemoto ◽  
N. Mochizuki ◽  
K. M. Shibata ◽  
D.-G. Roh ◽  
H.-S. Chung
Keyword(s):  
Detection Rate ◽  
Massive Star ◽  
Molecular Line ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Maser Sources

AbstractWe present the results of a mm wavelength methanol maser survey towards massive star forming regions. We have carried out Class II methanol maser observations at 86.6 GHz, 86.9 GHz and 107.0 GHz, simultaneously, using the Nobeyama 45 m telescope. We selected 108 6.7 GHz methanol maser sources with declinations above −25 degrees and fluxes above 20 Jy. The detection limit of maser observations was ~3 Jy. Of the 93 sources surveyed so far, we detected methanol emission in 25 sources (27%) and “maser” emission in nine sources (10%), of which thre “maser” sources are new detections. The detection rate for maser emission is about half that of a survey of the southern sky (Caswell et al. 2000). There is a correlation between the maser flux of 107 GHz and 6.7 GHz/12 GHz emission, but no correlation with the “thermal” (non maser) emission. From results of other molecular line observations, we found that the sources with methanol emission show higher gas temperatures and twice the detection rate of SiO emission. This may suggest that dust evaporation and destruction by shock are responsible for the high abundance of methanol molecules, one of the required physical conditions for maser emission.

scholarly journals Chandra and Spitzer observations of young clusters

2006 ◽  
Vol 2 (S237) ◽  
pp. 496-496
Author(s):  
S. J. Wolk ◽  
B. D. Spitzbart ◽  
T. L. Bourke
Keyword(s):  
Star Formation ◽  
Spectral Resolution ◽  
Massive Star ◽  
Young Star ◽  
Small Cluster ◽  
Massive Star Formation ◽  
X Ray ◽  
Star Forming ◽  
Be Star ◽  
Insight Into

AbstractThe combination of spatial and spectral resolution allow us to use Chandra in the study regions of massive star formation which had been inaccessible even from the ground until the last decade. IRAC and MIPS data from Spitzer can be combined with the X–ray data to provide insight into the presence of a disk and the activity of the star. The total package allows us to better understand the evolution of the clusters. We have an ongoing program to study several young star forming clusters including distant clusters between 1-3 kpc which support O stars, RCW 38, NGC 281 and RCW 108 and well as clusters within a kpc including IRAS 20050+2720 and NGC 1579, which is a small cluster centered on the Be star LkHα101 and is of uncertain distance although the X-ray data help us refine the current distance estimates. Given the space constraints we only discuss RCW 108 below.

scholarly journals ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – I. Survey description and a first look at G9.62+0.19

2020 ◽  
Vol 496 (3) ◽  
pp. 2790-2820 ◽  
Author(s):  
Tie Liu ◽  
Neal J Evans ◽  
Kee-Tae Kim ◽  
Paul F Goldsmith ◽  
Sheng-Yuan Liu ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Star Formation ◽  
Survey Data ◽  
Massive Star ◽  
High Mass ◽  
Dense Gas ◽  
Star Forming ◽  
Star Forming Regions ◽  
Stellar Feedback ◽  
Dense Cores

ABSTRACT The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2−1, HCO+J = 1−0, and HCN J = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ‘dense gas’ star formation scaling relations and massive protocluster formation.

scholarly journals VLBA Imaging of 12.2 GHz Methanol Masers

1998 ◽  
Vol 164 ◽  
pp. 375-376
Author(s):  
S. P. Ellingsen ◽  
P.M. McCulloch ◽  
P. J. Diamond ◽  
R. P. Norris
Keyword(s):  
Star Formation ◽  
Velocity Distribution ◽  
Massive Star ◽  
Star Formation Region ◽  
Formation Region ◽  
Maser Emission ◽  
Methanol Maser ◽  
Upper Limit ◽  
Methanol Masers ◽  
Right Ascension

AbstractWe have used the VLBA to image the 12.2 GHz (20-3−1 E) masing transition of methanol toward the massive star formation region G345.01+1.79. The maser spots are distributed in a curved structure with a near monotonic velocity distribution along the curve. The cluster of maser emission covers an area of approximately 200 milli-arcseconds in right ascension and 70 milli-arcseconds in declination.Comparison of the positions of the 12.2 GHz methanol maser spots in G345.01+1.79 as determined from the 1995 VLBA observations with 1988 Parkes-Tidbinbilla Interferometer observations shows that the relative positions of the maser spots detected in both epochs has changed by less than 5 milli-arcseconds during that interval. Assuming a distance of 2.3 kpc to G345.01+1.79 implies an upper limit on the relative tangential velocities of the maser spots of 7 km s−1.

scholarly journals Magnetic fields and massive star formation

2018 ◽  
Vol 14 (A30) ◽  
pp. 141-141
Author(s):  
Qizhou Zhang
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Dense Core ◽  
Continuum Emission ◽  
Massive Star Formation ◽  
Stellar Objects ◽  
Star Forming ◽  
Dense Cores ◽  
The Mean

AbstractMassive stars ( ${\rm{M}} > \,8{M_ \odot }$ ) often form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. The role of magnetic fields during the formation of massive dense cores is still not clear. The steady improvement in sensitivity of (sub)millimeter interferometers over the past decade enabled observations of dust polarization of large samples of massive star formation regions. We carried out a polarimetric survey with the Submillimeter Array of 14 massive star forming clumps in continuum emission at a wavelength of 0.89 mm. This unprecedentedly large sample of massive star forming regions observed by a submillimeter interferometer before the advent of ALMA revealed compelling evidence of strong magnetic influence on the gas dynamics from 1 pc to 0.1 pc scales. We found that the magnetic fields in dense cores tend to be either parallel or perpendicular to the mean magnetic fields in their parental molecular clumps. Furthermore, the main axis of protostellar outflows does not appear to be aligned with the mean magnetic fields in the dense core where outflows are launched. These findings suggest that from 1 pc to 0.1 pc scales, magnetic fields are dynamically important in the collapse of clumps and the formation of dense cores. From the dense core scale to the accretion disk scale of ∼102 au, however, gravity and angular momentum appear to be more dominant relative to the magnetic field.

scholarly journals Massive Star Formation in the Ultraviolet Observed with the Hubble Space Telescope

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 13 ◽  
Author(s):  
Claus Leitherer
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Hubble Space Telescope ◽  
Spectral Synthesis ◽  
Star Clusters ◽  
Large Magellanic Cloud ◽  
H Ii Regions ◽  
Massive Star Formation ◽  
Space Telescope ◽  
Star Forming

Spectroscopic observations of a massive star formation in the ultraviolet and their interpretation are reviewed. After a brief historical retrospective, two well-studied resolved star clusters and the surrounding H II regions are introduced: NGC 2070 in the Large Magellanic Cloud and NGC 604 in M33. These regions serve as a training set for studies of more distant clusters, which can no longer be resolved into individual stars. Observations of recently formed star clusters and extended regions in star-forming galaxies in the nearby universe beyond the Local Group are presented. Their interpretation relies on spectral synthesis models. The successes and failures of such models are discussed, and future directions are highlighted. I present a case study of the extraordinary star cluster and giant H II region in the blue compact galaxy II Zw 40. The review concludes with a preview of two upcoming Hubble Space Telescope programs: ULLYSES, a survey of massive stars in nearby galaxies, and CLASSY, a study of massive star clusters in star-forming galaxies.

Sign in / Sign up

Export Citation Format

Share Document