scholarly journals An evolutionary sequence for high-mass star formation

2012 ◽  
Vol 8 (S292) ◽  
pp. 39-39
Author(s):  
S. L. Breen ◽  
S. P. Ellingsen
Keyword(s):  
Star Formation ◽  
Strong Evidence ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Evolutionary Sequence ◽  
Subsequent Work ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers

AbstractDetermining an evolutionary clock for high-mass star formation is an important step towards realizing a unified theory of star formation, as it will enable qualitative studies of the associated high-mass stars to be executed. Our recent studies have shown that masers have great potential to accurately trace the evolution of these regions. We have investigated the relative evolutionary phases associated with the presence of combinations of water, methanol and hydroxyl masers. Comparison between the characteristics of coincident sources has revealed strong evidence for an evolutionary sequence for the different maser species, a result that we now aim to corroborate through comparisons with chemical clocks.Using our new, large samples of methanol masers at 6.7 GHz (MMB survey; Green et al. (2009)) and 12.2 GHz (Breen et al. 2012), 22 GHz water masers (Breen & Ellingsen 2012), OH masers together with complementary data, we find strong evidence that it is not only the presence or absence of the different maser species that indicates the evolutionary stage of the associated high-mass star formation region (see e.g. Breen et al. (2010)), but that the properties of those masers can give even finer evolutionary details. Most notably, the intensity and velocity range of detected maser emission increases as the star forming region evolves (Breen et al. 2011).Subsequent work we have undertaken (Ellingsen et al. 2011) has shown that the presence of rare 37.7 GHz methanol masers may signal the end of the methanol maser phase. They show that 37.7 GHz methanol masers are associated only with the most luminous 6.7 and 12.2 GHz methanol masers, which combined with the rarity of these objects is consistent with them being a short lived phase towards the end of the 6.7 GHz methanol maser lifetime.An independent confirmation of our maser evolutionary timeline can be gained through comparisons with chemical clocks. MALT90 is a legacy survey of 1000s of dense star forming cores at 90GHz, simultaneously observing 16 molecular lines with the Mopra radio telescope (see e.g. Foster et al. 2011). It provides the perfect dataset to test the maser evolutionary timeline due to the targeted lines and the fact that at least one-quarter of the MALT90 sources correspond to maser sites, providing a large enough sample for meaningful analysis. From our preliminary analysis, we find that star formation regions showing similar maser properties also show similar thermal line properties; as would be expected if our evolutionary scenario were accurate.

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 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.

scholarly journals GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

2021 ◽  
Author(s):  
A J Rigby ◽  
N Peretto ◽  
R Adam ◽  
P Ade ◽  
M Anderson ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Sensitivity ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Mass Growth ◽  
Star Forming ◽  
Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

scholarly journals A Sensitive Search for Predicted Methanol Maser Transitions with the Australia Telescope Compact Array

2016 ◽  
Vol 33 ◽  
Author(s):  
A. Chipman ◽  
S. P. Ellingsen ◽  
A. M. Sobolev ◽  
D. M. Cragg
Keyword(s):  
Star Formation ◽  
Class Ii ◽  
High Mass ◽  
Mass Star ◽  
Radio Telescopes ◽  
Methanol Maser ◽  
Upper Limit ◽  
Methanol Masers ◽  
Star Formation Regions ◽  
Compact Array

AbstractWe have used the Australia Telescope Compact Array to search for a number of centimetre wavelength methanol transitions which are predicted to show weak maser emission towards star formation regions. Sensitive, high spatial, and spectral resolution observations towards four high-mass star formation regions which show emission in a large number of class II methanol maser transitions did not result in any detections. From these observations, we are able to place an upper limit of ≲ 1300 K on the brightness temperature of any emission from the 31A+–31A−, 17−2–18−3 E (vt = 1), 124–133 A−, 124–133 A+, and 41A+–41A− transitions of methanol in these sources on angular scales of 2 arcsec. This upper limit is consistent with current models for class II methanol masers in high-mass star formation regions and better constraints than those provided here will likely require observations with next-generation radio telescopes.

scholarly journals The radial velocity acceleration of the 6.7 GHz methanol maser in Mon R2 IRS3

2012 ◽  
Vol 8 (S287) ◽  
pp. 190-191
Author(s):  
K. Sugiyama ◽  
K. Fujisawa ◽  
N. Shino ◽  
A. Doi
Keyword(s):  
Radial Velocity ◽  
High Mass ◽  
Mass Star ◽  
Spectral Features ◽  
Proper Motions ◽  
Infrared Source ◽  
Young Stellar Object ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers

AbstractWe present the radial velocity acceleration of the 6.7 GHz methanol maser in a high-mass star-forming region Monoceros R2 (Mon R2). The methanol maser is associated with an infrared source IRS3. The methanol maser of Mon R2 shows at least three spectral features having radial velocities (Vlsr) of 10.8, 12.7, and 13.2 km s−1. The radial velocity of a feature at Vlsr = 12.7 km s−1 has changed during ten years from Aug. 1999 to Oct. 2009, corresponding to an acceleration of 0.08 km s−1 yr−1. We observed the 6.7 GHz methanol masers of Mon R2 in Oct. 2008 using the Japanese VLBI Network (JVN). Compared with the previous VLBI image obtained in Nov. 1998 using the European VLBI Network (EVN), the maser feature at Vlsr = 12.7 km s−1 showed relative proper motions of ~2.5 mas yr−1 (about 10 km s−1 at 0.83 kpc) toward the intensity peak of IRS3. The radial velocity acceleration could be caused by an inflow from a disk or envelope around a high-mass young stellar object (YSO) at IRS3.

scholarly journals New class I methanol masers

2012 ◽  
Vol 8 (S287) ◽  
pp. 433-440 ◽  
Author(s):  
M. A. Voronkov ◽  
J. L. Caswell ◽  
S. P. Ellingsen ◽  
S. L. Breen ◽  
T. R. Britton ◽  
...  
Keyword(s):  
Class I ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
New Class ◽  
Star Forming Regions ◽  
Rare Class ◽  
New Type ◽  
Methanol Masers

AbstractWe review properties of all known collisionally pumped (class I) methanol maser series based on observations with the Australia Telescope Compact Array (ATCA) and the Mopra radio telescope. Masers at 36, 84, 44 and 95 GHz are most widespread, while 9.9, 25, 23.4 and 104 GHz masers are much rarer, tracing the most energetic shocks. A survey of many southern masers at 36 and 44 GHz suggests that these two transitions are highly complementary. The 23.4 GHz maser is a new type of rare class I methanol maser, detected only in two high-mass star-forming regions, G357.97-0.16 and G343.12-0.06, and showing a behaviour similar to 9.9, 25 and 104 GHz masers. Interferometric positions suggest that shocks responsible for class I masers could arise from a range of phenomena, not merely an outflow scenario. For example, some masers might be caused by interaction of an expanding Hii region with its surrounding molecular cloud. This has implications for evolutionary sequences incorporating class I methanol masers if they appear more than once during the evolution of the star-forming region. We also make predictions for candidate maser transitions in the ALMA frequency range.

scholarly journals Investigating high-mass star formation through maser surveys

2007 ◽  
Vol 3 (S242) ◽  
pp. 213-217 ◽  
Author(s):  
S. P. Ellingsen ◽  
M. A. Voronkov ◽  
D. M. Cragg ◽  
A. M. Sobolev ◽  
S. L. Breen ◽  
...  
Keyword(s):  
Star Formation ◽  
The Other ◽  
High Mass ◽  
Mass Star ◽  
Evolutionary Sequence ◽  
Physical Conditions ◽  
Other Information ◽  
Evolutionary Phase ◽  
The Common ◽  
Methanol Masers

AbstractInterstellar masers are unique probes of the environments in which they arise. In studies of high-mass star formation their primary function has been as signposts of these regions and they have been used as probes of the kinematics and physical conditions in only a few sources. With a few notable exceptions, we know relatively little about the evolutionary phase the different maser species trace, nor their location with respect to other star formation tracers. While detailed studies of a small number of maser regions can reveal much about them, other information can only be obtained through large, systematic searches. In particular, such surveys are vital in efforts to determine an evolutionary sequence for the common maser species, and there is growing evidence that methanol masers may trace an earlier phase than the other common maser species of OH and water.

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 Where methanol masers spring

2007 ◽  
Vol 3 (S242) ◽  
pp. 178-179
Author(s):  
Karl J. E. Torstensson ◽  
Huib Jan van Langevelde ◽  
Stephen Bourke
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Surrounding Environment ◽  
First Results ◽  
Vlbi Data ◽  
Methanol Masers ◽  
Cepheus A

AbstractWe are carrying out a program to observe the 6.7 GHz methanol maser emission in high-mass star-forming regions using large FOV (~2'), astrometric, VLBI data. Here we report on the first results of the inner few arc seconds in Cepheus A East. We find a maser filament extending over ~1.7” (1200 AU), straddling the waist of Cep A HW2. The region in which the CH3OH masers are found contains several YSO's and it is not clear whether the CH3OH masers are associated with several different objects or rather the larger scale surrounding environment.

scholarly journals Masers: High Resolution Probes of Massive Star Formation

2004 ◽  
Vol 221 ◽  
pp. 133-140 ◽  
Author(s):  
S P Ellingsen
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Jigsaw Puzzle ◽  
Methanol Maser ◽  
Physical Conditions ◽  
Evolutionary Phase ◽  
Methanol Masers

Astrophysical masers are one of the most readily detected signposts of high-mass star formation. Their presence indicates special conditions, probably indicative of a specific evolutionary phase. Masers also represent the ultimate high-resolution probe of star formation with the potential to reveal information on the kinematics and physical conditions within the region at milli-arcsecond resolution. To date this potential has largely remained unfulfilled, however, recent advances suggest that this will soon change.The key to unlocking the potential of masers lies in identifying where they fit within the star formation jigsaw puzzle. I will review recent high resolution observations of OH, water and methanol maser transitions and what they reveal. I also briefly discuss how multi-transition observations of OH and methanol masers are being used to constrain maser pumping models and through this estimate the physical conditions in the masing region.

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