scholarly journals 325 GHz Water Masers in Orion Source I

2012 ◽  
Vol 8 (S287) ◽  
pp. 184-185
Author(s):  
Florian Niederhofer ◽  
Elizabeth Humphreys ◽  
Ciriaco Goddi ◽  
Lincoln J. Greenhill
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Compact Disk ◽  
Volume Source ◽  
Star Forming ◽  
Star Forming Regions ◽  
Water Masers ◽  
Excitation Conditions

AbstractRadio Source I in the Orion BN/KL region provides the closest example of high mass star formation. It powers a rich ensemble of SiO and H2O masers, and is one of only three star-forming regions known to display SiO maser emission. Previous monitoring of different SiO masers with the VLBA and VLA has enabled the resolution of a compact disk and a protostellar wind at radii <100 AU from Source I, which collimates into a bipolar outflow at radii of 100-1000 AU (see contribution by Greenhill et al., this volume). Source I may provide the best case of disk-mediated accretion and outflow recollimation in massive star formation. Here, we report preliminary results of sub-arcsecond resolution 325 GHz H2O maser observations made with the SMA. We find that 325 GHz H2O masers trace a more collimated portion of the Source I outflow than masers at 22 GHz, but occur at similar radii suggesting similar excitation conditions. A velocity gradient perpendicular to the outflow axis, indicating rotation, supports magneto-centrifugal driving of the flow.

scholarly journals Methanol masers: Evolutionary and kinematic tracers of massive star formation

2002 ◽  
Vol 206 ◽  
pp. 147-150
Author(s):  
Vincent Minier ◽  
Roy Booth ◽  
John Conway ◽  
Michele Pestalozzi
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Methanol Masers ◽  
Maser Sources

We summarise our recent VLBI observations of a large sample of methanol maser sources associated with high-mass star-forming regions.

Probing Early Phases of High Mass Stars with 6.7 GHz Methanol Masers

2017 ◽  
Vol 13 (S336) ◽  
pp. 323-324
Author(s):  
Sonu Tabitha Paulson ◽  
Jagadheep D. Pandian
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Dust Emission ◽  
Black Body ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Early Phases

AbstractMethanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here the SED studies of 284 methanol masers chosen from the MMB catalogue, which falls in the Hi-GAL range (|l| ≤ 60°, |b| ≤ 1°). The masers are studied using the ATLASGAL, MIPSGAL and Hi-GAL data at wavelengths ranging from 24−870 micrometers. A single grey body component fit was used to model the cold dust emission whereas the emission from the warm dust is modelled by a black body. The clump properties such as isothermal mass, FIR luminosity and MIR luminosity were obtained using the best fit parameters of the SED fits. We discuss the physical properties of the sources and explore the evolutionary stages of the sources having 6.7 GHz maser emission in the timeline of high mass star formation.

scholarly journals Newly detected H2O Masers in Seyfert and Starburst Galaxies

2005 ◽  
Vol 13 ◽  
pp. 851-853 ◽  
Author(s):  
A. B. Peck ◽  
A. Tarchi ◽  
C. Henkel ◽  
N. M. Nagar ◽  
J. Braatz ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Massive Star ◽  
Chemical Properties ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Nearby Galaxies ◽  
Maser Sources

AbstractWe report new detections of three H2O megamasers and one kilomaser using the Effelsberg 100-m telescope. Isotropic luminosities are ~50, 300, 1, and 230 L⊙ for Mrk 1066, Mrk 34, NGC 3556, and Arp 299, respectively. Mrk 34 contains the most distant H2O megamaser ever detected in a Seyfert. Our targets in this survey were chosen to fit one of the following criteria: 1) to have a high probability of interaction between the radio jet and the ISM within the central few parsecs of the radio galaxy, yielding masers which arise in local molecular clouds; or 2) to have very bright IRAS sources in which massive star forming regions might yield powerful masers. The ‘jet maser’ sources can provide detailed information about the conditions in the ISM in the central 1-10 pc of AGN. The extra-galactic ‘star formation masers’ can be used to pinpoint and characterize locations of high mass star formation in nearby galaxies. In addition, these sources will help to provide a better understanding of the chemical properties of molecular clouds in extra-galactic systems.

scholarly journals Different Evolutionary Stages in the Massive Star-forming Complex W3 Main

2012 ◽  
Vol 8 (S292) ◽  
pp. 116-116
Author(s):  
Yuan Wang ◽  
Henrik Beuther ◽  
Qizhou Zhang ◽  
Arjan Bik ◽  
Javier A. Rodón ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Massive Star ◽  
Chemical Properties ◽  
Hii Regions ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
And Chemical Properties

AbstractWe observed with the Submillimeter Array and IRAM 30 m telescope three high-mass star-forming regions in different evolutionary stages in the W3 high-mass star formation complex. These regions, i.e. W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple mm continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicates that they are in different evolutionary stages. Even within each sub-region, massive cores of different ages are found, e.g. in SMS2, sub-sources from the most evolved UCHii region to potential starless cores exist within 30 000 AU (left panel, Fig. 1). Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the HII regions is found in the 13CO channel maps (right panel, Fig. 1), which may indicate triggered star formation.

scholarly journals Survey of ortho-H2D+ in high-mass star-forming regions

2020 ◽  
Vol 644 ◽  
pp. A34
Author(s):  
G. Sabatini ◽  
S. Bovino ◽  
A. Giannetti ◽  
F. Wyrowski ◽  
M. A. Órdenes ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Strong Dependence ◽  
Cosmic Ray ◽  
High Mass ◽  
Clear Correlation ◽  
Mass Star ◽  
Large Sample ◽  
Star Forming ◽  
Star Forming Regions

Context. Deuteration has been suggested to be a reliable chemical clock of star-forming regions due to its strong dependence on density and temperature changes during cloud contraction. In particular, the H3+ isotopologues (e.g. ortho-H2D+) seem to act as good proxies of the evolutionary stages of the star formation process. While this has been widely explored in low-mass star-forming regions, in the high-mass counterparts only a few studies have been pursued, and the reliability of deuteration as a chemical clock remains inconclusive. Aims. We present a large sample of o-H2D+ observations in high-mass star-forming regions and discuss possible empirical correlations with relevant physical quantities to assess its role as a chronometer of star-forming regions through different evolutionary stages. Methods. APEX observations of the ground-state transition of o-H2D+ were analysed in a large sample of high-mass clumps selected from the ATLASGAL survey at different evolutionary stages. Column densities and beam-averaged abundances of o-H2D+ with respect to H2, X(o-H2D+), were obtained by modelling the spectra under the assumption of local thermodynamic equilibrium. Results. We detect 16 sources in o-H2D+ and find clear correlations between X(o-H2D+) and the clump bolometric luminosity and the dust temperature, while only a mild correlation is found with the CO-depletion factor. In addition, we see a clear correlation with the luminosity-to-mass ratio, which is known to trace the evolution of the star formation process. This would indicate that the deuterated forms of H3+ are more abundant in the very early stages of the star formation process and that deuteration is influenced by the time evolution of the clumps. In this respect, our findings would suggest that the X(o-H2D+) abundance is mainly affected by the thermal changes rather than density changes in the gas. We have employed these findings together with observations of H13CO+, DCO+, and C17O to provide an estimate of the cosmic-ray ionisation rate in a sub-sample of eight clumps based on recent analytical work. Conclusions. Our study presents the largest sample of o-H2D+ in star-forming regions to date. The results confirm that the deuteration process is strongly affected by temperature and suggests that o-H2D+ can be considered a reliable chemical clock during the star formation processes, as proved by its strong temporal dependence.

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 22 GHz Water Maser Survey of the Xinjiang Astronomical Observatory

2012 ◽  
Vol 8 (S287) ◽  
pp. 296-297
Author(s):  
Jian-jun Zhou ◽  
Jarken Esimbek ◽  
Gang Wu
Keyword(s):  
Galactic Plane ◽  
Astronomical Observatory ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Gas Kinematics ◽  
Star Forming Regions ◽  
Water Masers ◽  
Maser Sources ◽  
Water Maser

AbstractWater masers are good tracers of high-mass star-forming regions. Water maser VLBI observations provide a good probe for studying high-mass star formation and galactic structure. We plan to make a blind survey toward the northern Galactic plane in future years using the 25 m radio telescope of the Xinjiang Astronomical Observatory. We will select some water maser sources discovered in the survey and perform high resolution observations to study the gas kinematics close to high-mass protostars.

scholarly journals 44 GHz Methanol Maser Surveys

2012 ◽  
Vol 8 (S287) ◽  
pp. 133-140
Author(s):  
S. E. Kurtz
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Class Ii ◽  
Class I ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Methanol Masers

AbstractClass I 44 GHz methanol masers are not as well-known, as common, or as bright as their more famous Class II cousins at 6.7 and 12.2 GHz. Nevertheless, the 44 GHz masers are commonly found in high-mass star forming regions. At times they appear to trace dynamically important phenomena; at other times they show no obvious link to the star formation process. Here, we summarize the major observational efforts to date, including both dedicated surveys and collateral observations. The principal results are presented, some that were expected, and others that were unexpected.

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.

Sign in / Sign up

Export Citation Format

Share Document