Class II 6.7 GHz Methanol Maser Association with Young Massive Cores Revealed by ALMA

2017 ◽  
Vol 13 (S336) ◽  
pp. 247-250
Author(s):  
James O. Chibueze ◽  
Timea Csengeri ◽  
Ken’ichi Tatematsu ◽  
Tetsuo Hasegawa ◽  
Satoru Iguchi ◽  
...  
Keyword(s):  
Class Ii ◽  
High Mass ◽  
Evolutionary Sequence ◽  
Maser Emission ◽  
Methanol Maser ◽  
Promising Tool ◽  
Dense Cores ◽  
Show Evidence ◽  
Statistical Viewpoint ◽  
Compact Array

AbstractThe association of 6.7 GHz class II methanol (CH3OH) masers with ATLASGAL/ ALMA 0.9 mm massive dense cores is presented in this work from a statistical viewpoint. 42 of the 112 cores (37.5%) detected with the Atacama Compact Array (ACA) excite 6.7 GHz CH3OH masers. ACA cores have offsets 0\rlap.″17 to 4\rlap.″79 from the methanol multibeam survey (MMB), with a median of 2.″19. Approximately 90% of the MMB-associated cores are of masses > 40 M⊙. Because all the cores show evidence of outflow activity, and only a fraction of the cores excited CH3OH masers, we suggest that outflows precede the emergence of maser emission. This first ALMA survey of massive dense cores combined with the MMB survey along with other maser specie surveys is a promising tool to trace the evolutionary sequence of high-mass stars.

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 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 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 Unusual properties of the methanol maser emission in W48

2002 ◽  
Vol 206 ◽  
pp. 167-170
Author(s):  
Irina E. Val'tts ◽  
Stella Yu. Lyubchenko
Keyword(s):  
Class Ii ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser

In the star forming region W48 the spectrum of methanol lines is studied. It is found that the intensity of the 20 − 3−1E (12.2 GHz) line anti-correlates with the intensity of the 51-60A+ (6.7 GHz). All other class II methanol lines in the spectrum of W48 (21 − 30A+ (157 GHz), 31 − 40A+ (107 GHz) (possibly) and J0 - J−1E (157 GHz)) demonstrate the same behaviour as 20 − 3−1E (12.2 GHz) line. This fact contradicts to the current models of the class II methanol maser emission. The effect is confirmed in the sample of 67 sources. For the explanation of this fact some possibilities are considered.

scholarly journals Giant burst of methanol maser in S255IR-NIRS3

2018 ◽  
Vol 617 ◽  
pp. A80 ◽  
Author(s):  
M. Szymczak ◽  
M. Olech ◽  
P. Wolak ◽  
E. Gérard ◽  
A. Bartkiewicz
Keyword(s):  
Sampling Interval ◽  
Young Stellar Objects ◽  
High Mass ◽  
Stellar Objects ◽  
Maser Emission ◽  
Methanol Maser ◽  
Star Evolution ◽  
Average Sampling ◽  
Methanol Masers ◽  
Observational Signature

Context. High-mass young stellar objects (HMYSOs) can undergo accretion episodes that strongly affect the star evolution, the dynamics of the disk, and its chemical evolution. Recently reported extraordinary bursts in the methanol maser emission may be the observational signature of accretion events in deeply embedded HMYSOs. Aims. We analyze the light curve of 6.7 GHz methanol masers in S255IR-NIRS3 during the 2015–2016 burst. Methods. 8.5-yr monitoring data with an average sampling interval of 5 days were obtained with the Torun 32 m radio telescope. Archival data were added, extending the time series to ~27 yr. Results. The maser emission showed moderate (25–30%) variability on timescales of months to years over ~23 yr since its discovery. The main burst was preceded by a 1 yr increase of the total flux density by a factor of 2.5, then it grew by a factor of 10 over ~0.4 yr and declined by a factor of 8 during the consecutive 2.4 yr. The peak maser luminosity was a factor of 24.5 higher than the pre-burst quiescent value. The light curves of individual features showed considerable diversity but indicated a general trend of suppression of the maser emission at blueshifted (<4.7 km s−1) velocities when the redshifted emission rapidly grew and new emission features appeared at velocities >5.8 km s−1. This new emission provided a contribution of about 80% to the maser luminosity around the peak of the burst. The duration of the burst at the extreme redshifted velocities of 7.1–8.7 km s−1 was from 0.9 to 1.9 yr, and its lower limit for the other features was ~3.9 yr. Conclusions. The onset of the maser burst exactly coincides with that of the infrared burst estimated from the motion of the light echo. This strongly supports the radiative pumping scheme of the maser transition. The growth of the maser luminosity is the result of an increasing volume of gas where the maser inversion is achieved.

scholarly journals The W51 Main/South SFR complex seen through 6-GHz OH and methanol masers

2012 ◽  
Vol 8 (S287) ◽  
pp. 171-175 ◽  
Author(s):  
Sandra Etoka ◽  
Malcolm D. Gray ◽  
Gary A. Fuller
Keyword(s):  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Relationship Of ◽  
The Relationship

AbstractW51 Main/South is one of the brightest and richest high-mass star-forming regions (SFR) in the complex W51. It is known to host many ultra-compact HII (UCHII) regions thought to be the site of massive young stellar objects. Maser emission from various species is also found in the region. We have performed MERLIN astrometric observations of excited-OH maser emission at 6.035 GHz and Class II methanol maser emission at 6.668 GHz towards W51 to investigate the relationship between the maser emission and the compact continuum sources in this SFR complex. Here we present the astrometric distributions of both 6.668-GHz methanol and 6.035-GHz excited-OH maser emission in the W51 Main/South region. The location of maser emission in the two lines is compared with that of previously published OH groundstate emission. The interesting coherent velocity and spatial structure observed in the methanol maser distribution as well as the relationship of the masers to infall or outflow in the region are discussed. It appears that the masers are excited by multiple objects potentially at different stages of evolution.

scholarly journals The molecular environment of massive star forming cores associated with Class II methanol maser emission

2007 ◽  
Vol 3 (S242) ◽  
pp. 125-129
Author(s):  
S. N. Longmore ◽  
M. G. Burton ◽  
P. J. Barnes ◽  
T. Wong ◽  
C. R. Purcell ◽  
...  
Keyword(s):  
Massive Star ◽  
Class Ii ◽  
Dynamic State ◽  
Continuum Emission ◽  
Molecular Gas ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers

AbstractMethanol maser emission has proven to be an excellent signpost of regions undergoing massive star formation (MSF). To investigate their role as an evolutionary tracer, we have recently completed a large observing program with the ATCA to derive the dynamical and physical properties of molecular/ionised gas towards a sample of MSF regions traced by 6.7GHz methanol maser emission. We find that the molecular gas in many of these regions breaks up into multiple sub-clumps which we separate into groups based on their association with/without methanol maser and cm continuum emission. The temperature and dynamic state of the molecular gas is markedly different between the groups. Based on these differences, we attempt to assess the evolutionary state of the cores in the groups and thus investigate the role of class II methanol masers as a tracer of MSF.

scholarly journals KVN Single-dish Water and Methanol Maser Line Surveys of Galactic YSOs

2012 ◽  
Vol 8 (S287) ◽  
pp. 488-491
Author(s):  
Kee-Tae Kim ◽  
Do-Young Byun ◽  
Jae-Han Bae ◽  
Won-Ju Kim ◽  
Hyun-Woo Kang ◽  
...  
Keyword(s):  
Class I ◽  
High Mass ◽  
Evolutionary Stage ◽  
Intermediate Mass ◽  
Detection Rates ◽  
Methanol Maser ◽  
Dense Cores ◽  
The Galaxy ◽  
Maser Line ◽  
Circumstellar Environments

AbstractWe have carried out simultaneous 22 GHz H2O and 44 GHz Class I CH3OH maser line surveys of more than 1500 intermediate- and high-mass YSOs in the Galaxy using newly-constructed KVN 21-m telescopes. As the central (proto)stars evolve, the detection rates of the two masers rapidly decrease for intermediate-mass YSOs while the rates increase for high-mass YSOs. These results suggest that the occurrence of the two masers is closely related both to the evolutionary stage of the central objects and to the circumstellar environments. CH3OH masers always have very similar velocities (<10 km s−1) to the natal dense cores, whereas H2O masers often have significantly different velocities. The isotropic luminosities of both masers are well correlated with the bolometric luminosities of the central (proto)stars.

scholarly journals Ring shaped 6.7 GHz methanol maser emission around a young high-mass star

2005 ◽  
Vol 442 (3) ◽  
pp. L61-L64 ◽  
Author(s):  
A. Bartkiewicz ◽  
M. Szymczak ◽  
H. J. van Langevelde
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Maser Emission ◽  
Methanol Maser
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