ON THE RELATIONSHIP OF UC H ii REGIONS AND CLASS II METHANOL MASERS. I. SOURCE CATALOGS

Hu, Bo; Menten, K. M.; Wu, Y. W.; Bartkiewicz, A.; Rygl, K. L. J.; Reid, M. J.; Urquhart, J. S.; Zheng, Xingwu

doi:10.3847/0004-637x/833/1/18

Cited by 81 publications

(144 citation statements)

References 46 publications

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“…Weak water masers were detected by Titmarsh et al (2016) where S 22 GHz ∼ 0.7 Jy at v LSR = −21.6 km s −1 . Hu et al (2016) mapped the 6.668 GHz methanol masers of the high mass young stellar object (HMYSO) in 2012; it was only 5 Jy and had the same velocity extent as originally reported. The masers were also mapped by Rickert et al (2019) on 2015 September 09, who identified three 6.668 GHz methanol maser features at v LSR = −18, −17, and −16 km s −1 (F 6.668 = 1 − 3 Jy) in a single position.…”

mentioning

confidence: 71%

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

MacLeod

Sugiyama

Hunter

et al. 2019

Monthly Notices of the Royal Astronomical Society

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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 timescales (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 days. 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.

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mentioning

confidence: 71%

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

MacLeod

Sugiyama

Hunter

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The light curve of the velocity-integrated flux density is presented in Figure 2 where the new and archival observations are complemented with the discovery detection (Szymczak et al 2000) and a single VLA observation (Hu et al 2016). The emission peaked around MJD 55296 and 56340 and the second outburst has a FHWM of ∼256 d and the rising phase a factor of two shorter than the declining phase.…”

Section: Resultsmentioning

confidence: 99%

“…The black squares and magenta circles denote the archival Torun 32 m data and fromSzymczak et al (2018), respectively. The blue triangle refers to the first detection(Szymczak et al 2000) and the black star marks the VLA observation at MJD 55990(Hu et al 2016).…”

mentioning

confidence: 99%

A highly variable methanol maser in G111.256–0.770

Durjasz

Szymczak

Олеч

2019

Monthly Notices of the Royal Astronomical Society

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G111.256−0.770 is a high-mass young stellar object associated with a weak 6.7 GHz methanol maser showing strong variability. We present results of a multi-epoch monitoring program of the target, conducted with the Torun 32 m telescope for more than a decade. We found that the isotropic maser luminosity varied by a factor 16 on a timescale of 5−6 yr and individual features showed small amplitude short-lived (∼0.2 yr) bursts superimposed on higher amplitude slow (>5 yr) variations. The maser integrated flux density appears to be correlated with the near-infrared flux observed with the (NEO)WISE, supporting radiative pumping of the maser line.

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“…Due to such regions' compactness, their radio emission is very weak. However, an increasing number of such objects is now being detected with the JVLA (Rosero et al 2016;Hu et al 2016). van der Walt (2005) estimated the lifetime of class II methanol masers between 2.5 × 10 4 and 4.5 × 10 4 yr (depending on the assumed IMF).…”

Section: Discovery Of Three New Hot Cores In Sgr B2(n)mentioning

confidence: 99%

Exploring molecular complexity with ALMA (EMoCA): Detection of three new hot cores in Sagittarius B2(N)

Bonfand

Беллоче

Menten

et al. 2017

A&A

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102

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Context. The Sagittarius B2 molecular cloud contains several sites forming high-mass stars. Sgr B2(N) is one of its main centers of activity. It hosts several compact and ultra-compact HII regions, as well as two known hot molecular cores (Sgr B2(N1) and Sgr B2(N2)) in the early stage of the high-mass star formation process, where complex organic molecules (COMs) are detected in the gas phase. Aims. Our goal is to use the high sensitivity of the Atacama Large Millimeter/submillimeter Array (ALMA) to characterize the hot core population in Sgr B2(N) and thereby shed a new light on the star formation process in this star-forming region. Methods. We use a complete 3 mm spectral line survey conducted with ALMA to search for faint hot cores in the Sgr B2(N) region. The chemical composition of the detected sources and the column densities are derived by modelling the whole spectra under the assumption of local thermodynamic equilibrium. Population diagrams are constructed to fit rotational temperatures. Integrated intensity maps are produced to derive the peak position and fit the size of each molecule's emission distribution. The kinematic structure of the hot cores is investigated by analyzing the line wing emission of typical outflow tracers. The H 2 column densities are computed from ALMA and SMA continuum emission maps. Results. We report the discovery of three new hot cores in Sgr B2(N) that we call Sgr B2(N3), Sgr B2(N4), and Sgr B2(N5). The three sources are associated with class II methanol masers, well known tracers of high-mass star formation, and Sgr B2(N5) also with a UCHII region. Their H 2 column densities are found to be ∼16 up to 36 times lower than the one of the main hot core Sgr B2(N1). The spectra of these new hot cores have spectral line densities of 11 up to 31 emission lines per GHz above the 7σ level, assigned to 22-25 molecules plus 13-20 less abundant isotopologs. We derive rotational temperatures around 140-180 K for the three new hot cores and mean source sizes of 0.4 for Sgr B2(N3) and 1.0 for Sgr B2(N4) and Sgr B2(N5). The chemical composition of Sgr B2(N3), Sgr B2(N4), and Sgr B2(N5) is very similar, but it differs from that of Sgr B2(N2). Finally, Sgr B2(N3) and Sgr B2(N5) show high velocity wing emission in typical outflow tracers, with a bipolar morphology in their integrated intensity maps suggesting the presence of an outflow, like in Sgr B2(N1). No sign of an outflow is found around Sgr B2(N2) and Sgr B2(N4). We derive statistical lifetimes of 4 × 10 4 yr for the class II methanol maser phase and 6 ×10 4 yr for the hot core phase in Sgr B2(N). Conclusions. The associations of the hot cores with class II methanol masers, outflows, and/or UCHII regions tentatively suggest the following age sequence: Sgr B2(N4), Sgr B2(N3), SgrB2(N5), Sgr B2(N1). The status of Sgr B2(N2) is unclear. It may contain two distinct sources, a UCHII region and a very young hot core.

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ON THE RELATIONSHIP OF UC H ii REGIONS AND CLASS II METHANOL MASERS. I. SOURCE CATALOGS

Cited by 81 publications

References 46 publications

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

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

A highly variable methanol maser in G111.256–0.770

Exploring molecular complexity with ALMA (EMoCA): Detection of three new hot cores in Sagittarius B2(N)

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