Monitoring a methanol maser flare associated with the massive star-forming region G358.93–0.03

2020 ◽  
Vol 494 (1) ◽  
pp. L59-L63
Author(s):  
A E Volvach ◽  
L N Volvach ◽  
M G Larionov ◽  
G C MacLeod ◽  
S P van den Heever ◽  
...  
Keyword(s):  
Massive Star ◽  
Star Forming ◽  
Methanol Maser ◽  
The Galaxy ◽  
History Of ◽  
Entire History ◽  
Methanol Masers

ABSTRACT We report the earliest detection of the 19.967-GHz [transition 21–30E (t = 0)] methanol maser associated with the massive star-forming region G358.93–0.03. The flare was detectable from 2019 January 23 to March 5, for only 44 d. It turned out to be the most powerful 19.967-GHz maser in the Galaxy in the entire history of observations, taking into account the 104-Jy flux from it on the Earth’s surface and the distance to the source, 6.75 kpc. The 19.967-GHz maser flared contemporaneously with the first of two flares detected in associated 20.971-GHz methanol masers. We estimated that the ratio of flux densities between these two transitions is F20.971/F19.967 = 14 ± 4, increasing to >520 in the second flare. We discuss the differences between the two flares in the 20.971-GHz methanol masers and the consequence thereof.

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 Japanese VLBI network observations of 6.7-GHz methanol masers I. Array

2007 ◽  
Vol 3 (S242) ◽  
pp. 148-149
Author(s):  
Akihiro Doi ◽  
Kenta Fujisawa ◽  
Mareki Honma ◽  
Koichiro Sugiyama ◽  
Yasuhiro Murata ◽  
...  
Keyword(s):  
Massive Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Japanese Islands

AbstractThe Japanese VLBI network (JVN) has begun observations of 6.7-GHz methanol masers associated with massive star-forming regions. The JVN is a newly-established VLBI array with baselines ranging from 50 to 2560 km spread across the Japanese islands. Three observing bands of 6.7, 8.4, and 22 GHz are now available. The array consists of ten antennas: VERA Mizusawa 20 m, VERA Ishigaki 20 m, VERA Iriki 20 m, Usuda 64 m, Yamaguchi 32 m, Tomakomai 11 m, Tsukuba 32 m, Kashima 34 m, VERA Ogasawara 20 m, and Gifu 11 m, the first five of which have 6.7-GHz receiving systems. In summer 2005, we obtained the first fringes at 6.7 GHz, and VLBI images of 12 methanol maser sites including seven that had not previously been imaged with VLBI at this band. In 2006 summer, we obtained phase-reference observations toward several methanol maser sites.

Linear polarisation of Class I methanol masers in massive star formation regions

2017 ◽  
Vol 13 (S336) ◽  
pp. 243-246
Author(s):  
Ji-hyun Kang ◽  
Do-Young Byun ◽  
Kee-Tae Kim ◽  
Aran Lyo ◽  
Jongsoo Kim ◽  
...  
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Follow Up Study ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Star Formation Regions ◽  
Linear Polarisation

AbstractWe present the results of the linear polarisation observations of methanol masers at 44 and 95 GHz towards 39 massive star forming regions (Kanget al.2016). These two lines are observed simultaneously with the 21-m Korean VLBI Network (KVN) telescope in single dish mode. About 60% of the observed showed fractional polarisation of a few percents at least at one of the two transition lines. We note that the linear polarisation of the 44 GHz methanol maser is first detected in this study including single dish and interferometer observations. We find the polarisation properties of these two lines are similar as expected, since they trace similar regions. As a follow-up study, we have carried out the VLBI polarisation observations toward some 44 GHz maser targets using the KVN telescope. We present preliminary VLBI polarisation results of G10.34-0.14, which show consistent polarisation properties in multiple epoch observations.

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.

Exploring the Nature of MMB sources: A Search for Class I Methanol Masers and their Outflows

2017 ◽  
Vol 13 (S336) ◽  
pp. 317-318
Author(s):  
Nichol Cunningham ◽  
Gary Fuller ◽  
Adam Avison ◽  
Shari Breen
Keyword(s):  
Massive Star ◽  
Class Ii ◽  
Class I ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Initial Results ◽  
Maser Sources

AbstractWe present the initial results from a class I 44-GHz methanol maser follow-up survey, observed with the MOPRA telescope, towards 272 sources from the Methanol Multi-beam survey (MMB). Over half (∼60%) of the 6.7 GHz class II MMB maser sources are associated with a class I 44-GHz methanol maser at a greater than 5σ detection level. We find that class II MMB masers sources with an associated class I methanol maser have stronger peak fluxes compared to regions without an associated class I maser. Furthermore, as part of the MOPRA follow-up observations we simultaneously observed SiO emission which is a known tracer of shocks and outflows in massive star forming regions. The presence of SiO emission, and potentially outflows, is found to be strongly associated with the detection of class I maser emission in these regions.

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 Detection of new methanol maser transitions associated with G358.93−0.03

2019 ◽  
Vol 489 (3) ◽  
pp. 3981-3989 ◽  
Author(s):  
G C MacLeod ◽  
K Sugiyama ◽  
T R Hunter ◽  
J Quick ◽  
W Baan ◽  
...  
Keyword(s):  
Energy Source ◽  
Flux Density ◽  
Time Scales ◽  
Massive Star ◽  
Near Infrared ◽  
Maser Emission ◽  
Star Forming ◽  
Methanol Maser ◽  
Methanol Masers ◽  
Short Time

ABSTRACT We report the detection of new 12.178, 12.229, 20.347, and 23.121 GHz methanol masers in the massive star-forming region G358.93−0.03, which are flaring on similarly short time-scales (days) as the 6.668 GHz methanol masers also associated with this source. The brightest 12.178 GHz channel increased by a factor of over 700 in just 50 d. The masers found in the 12.229 and 20.347 GHz methanol transitions are the first ever reported and this is only the fourth object to exhibit associated 23.121 GHz methanol masers. The 12.178 GHz methanol maser emission appears to have a higher flux density than that of the 6.668 GHz emission, which is unusual. No associated near-infrared flare counterpart was found, suggesting that the energy source of the flare is deeply embedded.

scholarly journals Isotopic fractionation study towards massive star-forming regions across the Galaxy

2021 ◽  
Author(s):  
Laura Colzi
Keyword(s):  
Massive Star ◽  
Chemical Elements ◽  
Isotopic Fractionation ◽  
Galactocentric Distance ◽  
Star Forming ◽  
Star Forming Regions ◽  
Stellar Nucleosynthesis ◽  
The Galaxy ◽  
History Of ◽  
Chemical History

One of the most important tools to investigate the chemical history of our Galaxy and our own Solar System is to measure the isotopic fractionation of chemical elements. In the present study new astronomical observations devoted to the study of hydrogen and nitrogen fractionation (D/H and 14N/15N ratios) of molecules, towards massive star-forming regions in different evolutionary phases, have been presented. Moreover, a new detailed theoretical study of carbon fractionation, 12C/13C ratios, has been done. One of the main results was the confirmation that the 14N/15N ratio increases with the galactocentric distance, as predicted by stellar nucleosynthesis Galactic chemical evolution models. This work gives new important inputs on the understanding of local chemical processes that favor the production of molecules with different isotopes in star-forming regions.

scholarly journals Searching for Mg ii absorbers in and around galaxy clusters

2021 ◽  
Vol 503 (3) ◽  
pp. 4309-4319
Author(s):  
Jong Chul Lee ◽  
Ho Seong Hwang ◽  
Hyunmi Song
Keyword(s):  
Galaxy Clusters ◽  
Detection Rate ◽  
Massive Star ◽  
Sloan Digital Sky Survey ◽  
Number Density ◽  
Cluster Galaxies ◽  
Star Forming ◽  
Quasar Spectra ◽  
Sky Survey ◽  
The Galaxy

ABSTRACT To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars, and cluster galaxies from the Sloan Digital Sky Survey (SDSS). With ∼82 000 quasar spectra, we detect 197 Mg ii absorbers in and around the clusters. The detection rate per quasar is 2.7 ± 0.7 times higher inside the clusters than outside the clusters, indicating that Mg ii absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that Mg ii absorbers are mainly contributed by the CGM of massive star-forming galaxies, a typical halo size of cluster galaxies is smaller than that of field galaxies by 30 ± 10 per cent. This finding supports that galaxy haloes can be truncated by interaction with the host cluster.

scholarly journals The origin of the galaxy color bimodality

2014 ◽  
Vol 11 (S308) ◽  
pp. 383-389
Author(s):  
M. A. Aragón-Calvo ◽  
Mark C. Neyrinck ◽  
Joseph Silk
Keyword(s):  
Spatial Configuration ◽  
Star Formation History ◽  
Star Forming ◽  
Complex Processes ◽  
Complex Process ◽  
Formation History ◽  
Density Relation ◽  
The Galaxy ◽  
Color Density ◽  
History Of

AbstractThe star formation history of galaxies is a complex process usually considered to be stochastic in nature, for which we can only give average descriptions such as the color-density relation. In this work we follow star-forming gas particles in a hydrodynamical N-body simulation back in time in order to study their initial spatial configuration. By keeping record of the time when a gas particle started forming stars we can produce Lagrangian gas-star isochrone surfaces delineating the surfaces of accreting gas that begin producing stars at different times. These surfaces form a complex a network of filaments in Eulerian space from which galaxies accrete cold gas. Lagrangian accretion surfaces are closely packed inside dense regions, intersecting each other, and as a result galaxies inside proto-clusters stop accreting gas early, naturally explaining the color dependence on density. The process described here has a purely gravitational / geometrical origin, arguably operating at a more fundamental level than complex processes such as AGN and supernovae, and providing a conceptual origin for the color-density relation.

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