scholarly journals The environs of the ultracompact HII region G45.45+0.06

2009 ◽  
Vol 506 (2) ◽  
pp. 789-796 ◽  
Author(s):  
S. Paron ◽  
S. Cichowolski ◽  
M. E. Ortega
Keyword(s):  
Hii Region ◽  
Ultracompact Hii

scholarly journals Deuteration around the ultracompact HII region Monoceros R2

2014 ◽  
Vol 569 ◽  
pp. A19 ◽  
Author(s):  
S. P. Treviño-Morales ◽  
P. Pilleri ◽  
A. Fuente ◽  
C. Kramer ◽  
E. Roueff ◽  
...  
Keyword(s):  
Hii Region ◽  
Ultracompact Hii

scholarly journals The Classification of M 1-78

1995 ◽  
Vol 12 (1) ◽  
pp. 31-36 ◽  
Author(s):  
G. T. Gussie
Keyword(s):  
Planetary Nebula ◽  
Main Sequence ◽  
Central Star ◽  
Expansion Velocity ◽  
Sequence Evolution ◽  
High Luminosity ◽  
Hii Region ◽  
Transient Phenomena ◽  
Ultracompact Hii

AbstractThe published properties of M1-78 are discussed with the purpose of resolving the object’s classification as either a planetary nebula or an ultracompact HII region. A classification as a planetary nebula is rejected primarily because of the high luminosity of the object, but because of the chemical composition and expansion velocity of the nebula, a novel classification is proposed instead: that of an ultracompact HII region with a post-main sequence central star (possibly a WN star). It must therefore follow that observable ultracompact HII regions persist beyond the main sequence lifetimes of at least some massive stars, and so cannot be transient phenomena that are seen only during pre-main sequence or early main sequence evolution.

scholarly journals Herschelobservations in the ultracompact HII region Mon R2

2010 ◽  
Vol 521 ◽  
pp. L23 ◽  
Author(s):  
A. Fuente ◽  
O. Berné ◽  
J. Cernicharo ◽  
J. R. Rizzo ◽  
M. González-García ◽  
...  
Keyword(s):  
Hii Region ◽  
Ultracompact Hii

scholarly journals Microwave observations of spinning dust emission in NGC6946⋆

2010 ◽  
Vol 406 (1) ◽  
pp. L45-L49 ◽  
Author(s):  
Anna M. M. Scaife ◽  
Bojan Nikolic ◽  
David A. Green ◽  
Rainer Beck ◽  
Matthew L. Davies ◽  
...  
Keyword(s):  
Dust Emission ◽  
Continuum Emission ◽  
Published Data ◽  
Nearby Galaxy ◽  
Hii Region ◽  
Wave Measurements ◽  
Dust Component ◽  
Emission Models ◽  
Analysis Package ◽  
Ultracompact Hii

ABSTRACT We report new cm-wave measurements at five frequencies between 15 and 18GHz of the continuum emission from the reportedly anomalous ‘region 4’ of the nearby galaxy NGC6946. We find that the emission in this frequency range is significantly in excess of that measured at 8.5GHz, but has a spectrum from 15 to 18GHz consistent with optically thin free–free emission from an ultracompact Hii region. In combination with previously published data, we fit four emission models containing different continuum components using the Bayesian spectrum analysis package radiospec. These fits show that, in combination with data at other frequencies, a model with a spinning dust component is slightly preferred to those that possess better-established emission mechanisms.

The Hot Molecular Core of G12.21–0.10: NH3(4, 4) Observations

2009 ◽  
Vol 5 (S262) ◽  
pp. 319-320
Author(s):  
Eduardo de la Fuente ◽  
Stanley E. Kurtz ◽  
Carlos A. Rodriguez-Rico ◽  
Miguel A. Trinidad ◽  
Esteban Araya ◽  
...  
Keyword(s):  
Spatial Location ◽  
Forthcoming Paper ◽  
Radio Continuum ◽  
Ionized Gas ◽  
Compact Structure ◽  
Hii Region ◽  
Molecular Core ◽  
Molecular Lines ◽  
First Time ◽  
Ultracompact Hii

AbstractIn de la Fuente (2007; Ph. D. Thesis), the molecular clump associated with the ultracompact HII region G12.21–0.10 was confirmed as a large, hot, dense Hot Molecular Core nearby to the ionized gas. The density was confirmed by comparing low resolution NH3(2, 2) and (4, 4) VLA observations, with other molecular lines and radio–continuum observations. These results will be presented in detail in a forthcoming paper (de la Fuente et al. in preparation). In these works, for the first time, the spatial location of the Hot Molecular Core is presented. Here we present the NH3(4,4) observations from de la Fuente (2007; Ph. D. Thesis), confirming that the hotter and denser gas in the molecular core lies in a compact structure, of smaller scale than the NH3(2, 2) emission.

Thermal Dust Imaging of the Ultracompact HII Region G29.96-0.02

1996 ◽  
Vol 112 ◽  
pp. 1645 ◽  
Author(s):  
Roger Ball ◽  
Margaret M. Meixner ◽  
Eric Keto ◽  
John F. Arens ◽  
J. Garrett Jernigan
Keyword(s):  
Hii Region ◽  
Ultracompact Hii

scholarly journals G305.20+0.21: A very young class II methanol maser source

2002 ◽  
Vol 206 ◽  
pp. 155-158
Author(s):  
Andrew J. Walsh
Keyword(s):  
Detection Limit ◽  
Class Ii ◽  
Radio Continuum ◽  
Radio Flux ◽  
Infrared Source ◽  
Hii Region ◽  
Methanol Maser ◽  
Upper Limits ◽  
Ultracompact Hii

Sensitive radio continuum observations of G305.20+0.21 are performed to look for evidence of an ultracompact HII region. None is found at either 8.64 or 4.8GHz above a 5σ detection limit of about 0.25mJy in both cases. Since G305.20+0.21 is such a bright infrared source, there is a large discrepancy between the expected radio flux and the observed upper limits. This is interpreted as evidence that G305.20+0.21 is a massive protostar traced by a methanol maser site.

scholarly journals A Spectral Line Survey of IRAS 17470-2853 from 86.1 to 92.1 GHz

2002 ◽  
Vol 19 (4) ◽  
pp. 505-514 ◽  
Author(s):  
Hun-Dae Kim ◽  
Ramesh Balasubramanyam ◽  
Michael G. Burton
Keyword(s):  
Spectral Line ◽  
Line Width ◽  
Thermal Emission ◽  
Frequency Range ◽  
Hii Region ◽  
Significant Difference ◽  
Molecular Lines ◽  
Line Survey ◽  
Simple Molecules ◽  
Ultracompact Hii

AbstractWe present results from a spectral line survey of the young stellar object IRAS 17470-2853, undertaken to examine chemical changes during the evolution from hot molecular cores to ultracompact HII regions. Observations were carried out with the Mopra 22 m radio telescope in the frequency range from 86.1 to 92.1 GHz. A total of 21 lines from 9 molecules were detected. Except for CH3CN they are all simple molecules. We compare the results to the ultracompact HII region G34.3+0.15, where spectral line surveys in the frequency range 80–115 GHz and 330–360 GHz have been performed. While the molecular lines detected are similar, their widths and intensities are somewhat narrower and lower, respectively, in IRAS 17470-2853. The typical line width of ˜5 km s−1 indicates relatively quiet or quasi-thermal emission. On the other hand, a significant difference in TA* (HNC)/TA*(HCN) has been found: 0.8 for IRAS 17470-2853 compared to 2.6 for G34.3+0.15. The broad line width of SiO (υ=0, J=2–1), ˜9 km s−1, suggests that IRAS 17470-2853 is experiencing a shock generated by the embedded object. Column densities, or lower limits to them, are derived for observed molecules.

scholarly journals Masers in GLIMPSE Extended Green Objects (EGOs)

2012 ◽  
Vol 8 (S287) ◽  
pp. 127-132
Author(s):  
Claudia J. Cyganowski ◽  
Crystal L. Brogan ◽  
Todd R. Hunter ◽  
Ed Churchwell ◽  
Jin Koda ◽  
...  
Keyword(s):  
Large Scale ◽  
Galactic Plane ◽  
Young Stellar Objects ◽  
Stellar Objects ◽  
Detection Rates ◽  
Hii Region ◽  
Star Forming ◽  
Common Coding ◽  
The Common ◽  
Ultracompact Hii

AbstractLarge-scale Spitzer surveys of the Galactic plane have yielded a new diagnostic for massive young stellar objects (MYSOs) that are actively accreting and driving outflows: extended emission in the IRAC 4.5 μm band, believed to trace shocked molecular gas. Maser studies of these extended 4.5 μm sources (called EGOs, Extended Green Objects, for the common coding of 3-color IRAC images) have been and remain crucial for understanding the nature of EGOs. High detection rates in VLA CH3OH maser surveys provided the first proof that EGOs were indeed MYSOs driving outflows; our recent Nobeyama 45-m survey of northern EGOs shows that the majority are associated with H2O masers. Maser studies of EGOs also provide important constraints for the longstanding goal of a maser evolutionary sequence for MYSOs, particularly in combination with high resolution (sub)mm data. New SMA results show that Class I methanol masers can be excited by both young (hot core) and evolved (ultracompact HII region) sources within the same massive star-forming region.

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