The Spatial-Kinematic Structure of the Region of Massive Star Formation S255N on Various Scales

The results of a detailed analysis of SMA, VLA, and IRAM observations of the region of massive star formation S255N in CO(2---1), \nh, \nhh, \co and some other lines is presented. Combining interferometer and single-dish data has enabled a more detailed investigation of the gas kinematics in the moleclar core on various spatial scales. There are no signs of rotation or isotropic compression on the scale of the region as whole. The largest fragments of gas ($\approx$0.3 pc) are located near the boundary of the regions of ionized hydrogen S255 and S257. Some smaller-scale fragments are associated with protostellar clumps. The kinetic temperatures of these fragments lie in the range 10---80 K. A circumstellar torus with inner radius R$_{in}$ $\approx$ 8000 AU and outer radius R$_{out}$ 12 000 AU has been detected around the clump SMA1. The rotation profile indicates the existence of a central object with mass $\approx$ 8.5/ sin 2 (i) M$_\odot$ . SMA1 is resolved into two clumps, SMA1---NE and SMA1---SE, whose temperatures are $\approx$150 K and $\approx$25 K, respectively. To all appearances, the torus is involved in the accretion of surrounding gas onto the two protostellar clumps

Molecular gas in high-mass filament WB673

We studied the distribution of dense gas in a filamentary molecular cloud containing several dense clumps. The center of the filament is given by the dense clump WB673. The clumps are high-mass and intermediate-mass star-forming regions. We observed CS(2-1), 13CO(1-0), C18O(1-0) and methanol lines at 96GHz toward WB673 with the Onsala Space Observatory 20-m telescope. We found CS(2-1) emission in the inter-clump medium so the clumps are physically connected and the whole cloud is indeed a filament. Its total mass is $10^4$ M$_{\odot}$ and mass-to-length ratio is 360 M$_{\odot}$pc$^{-1}$ from 13CO(1-0) data. Mass-to-length ratio for the dense gas is $3.4-34$ M$_{\odot}$pc$^{-1}$ from CS(2-1) data. The PV-diagram of the filament is V-shaped. We estimated physical conditions in the molecular gas using methanol lines. Location of the filament on the sky between extended shells suggests that it could be a good example to test theoretical models of formation of the filaments via multiple compression of interstellar gas by supersonic waves

Estimation of physical conditions in star formation region S255IR-SMA1

По радиолиниям метанола, наблюдавшимся на IRAM30m на 0.8 мм в области звездообразования S255IR-SMA1, проведена оценка физических условий. В приближении большого градиента скорости (LVG) оценены значения кинетической температуры газа (170 К), плотности молекулярного водорода (3 × 106 см−3), удельной лучевой концентрации метанола (2 × 1012 см−3с), относительного обилия метанола (10−7) и фактора заполнения диаграммы (10%). Значения параметров характерны для горячих плотных ядер. Показано, что объект S255IRR-SMA1 в рамках диаграммы направленности (7.5 ) существенно неоднороден.The physical conditions were estimated from the methanol radio lines observed at 0.8 mm with IRAM30m in the star-forming region S255IR-SMA1. In the approximation of a large velocity gradient (LVG), the values of the gas kinetic temperature (170 K), the number density of molecular hydrogen (3×106 cm−3), the specific column density of methanol (2×1012 cm−3s), the relative abundance of methanol (10−7) and the filling factor (10 %). The parameter values are typical for hot dense cores. It is shown that the S255IR-SMA1 object is significantly inhomogeneous within the diagram (7.5 ).Оценки физических параметров выполнены при поддержке гранта РФФИ № 18-02-00917

Multi-transition study and new detections of class II methanol masers

We have used the ATNF Mopra antenna and the SEST antenna to search in the directions of several class II methanol maser sources for emission from six methanol transitions in the frequency range 85-115 GHz. The transitions were selected from excitation studies as potential maser candidates. Methanol emission at one or more frequencies was detected from five of the maser sources, as well as from Orion KL. Although the lines are weak, we find evidence of maser origin for three new lines in G345.01+1.79, and possibly one new line in G9.62+0.20. The observations, together with published maser observations at other frequencies, are compared with methanol maser modelling for G345.01+1.79 and NGC6334F. We find that the majority of observations in both sources are consistent with a warm dust (175 K) pumping model at hydrogen density ~10^6 cm^-3 and methanol column density ~5 x 10^17 cm^-2. The substantial differences between the maser spectra in the two sources can be attributed to the geometry of the maser region.Comment: 13 pages, 6 figures, Accepted for publication in MNRA

The disk-outflow system in the S255IR area of high mass star formation

We report the results of our observations of the S255IR area with the SMA at 1.3 mm in the very extended configuration and at 0.8 mm in the compact configuration as well as with the IRAM-30m at 0.8 mm. The best achieved angular resolution is about 0.4 arcsec. The dust continuum emission and several tens of molecular spectral lines are observed. The majority of the lines is detected only towards the S255IR-SMA1 clump, which represents a rotating structure (probably disk) around the young massive star. The achieved angular resolution is still insufficient for conclusions about Keplerian or non-Keplerian character of the rotation. The temperature of the molecular gas reaches 130-180 K. The size of the clump is about 500 AU. The clump is strongly fragmented as follows from the low beam filling factor. The mass of the hot gas is significantly lower than the mass of the central star. A strong DCN emission near the center of the hot core most probably indicates a presence of a relatively cold ($\lesssim 80$ K) and rather massive clump there. High velocity emission is observed in the CO line as well as in lines of high density tracers HCN, HCO+, CS and other molecules. The outflow morphology obtained from combination of the SMA and IRAM-30m data is significantly different from that derived from the SMA data alone. The CO emission detected with the SMA traces only one boundary of the outflow. The outflow is most probably driven by jet bow shocks created by episodic ejections from the center. We detected a dense high velocity clump associated apparently with one of the bow shocks. The outflow strongly affects the chemical composition of the surrounding medium.Comment: 19 pages, 23 figures, accepted by The Astrophysical Journa

Bayesian approach to estimations of star-formation regions physical parameters by few methanol lines

Показано, что использование Байесовского подхода позволяет оценить температуру газа и удельную лучевую концентрацию метанола в областях звездообразования по двум радиолиниям метанола, плотность газа по четырем. Полученные значения физических параметров хорошо согласуются с независимыми оценками.We show that Bayesian approach is useful for estimating kinetic temperatures and methanol specific column densities of starformation regions by only two methanol lines and hydrogen number densities by four lines. Calculated physical parameters’ values are in good agreement with values that were estimated in other ways.Работа выполнена при поддержке Правительства Российской Федерации (постановление № 211, контракт №02.A03.21.0006) и Министерства образования и науки Российской Федерации (базовая часть государственного задания, РК №AAAA-A17-117030310283-7)

Methanol observation of IRAS 19312+1950: A possible new type of class I methanol maser

We report the result of a systematic methanol observation toward IRAS 19312+1950. The properties of the SiO, H2O, and OH masers of this object are consistent with those of mass-losing evolved stars, but some other properties are difficult to explain in the standard scheme of stellar evolution in its late stage. Interestingly, a tentative detection of radio methanol lines was suggested toward this object by a previous observation. To date, there are no confirmed detections of methanol emission towards evolved stars, so investigation of this possible detection is important to better understand the circumstellar physical/chemical environment of IRAS 19312+1950. In this study, we systematically observed multiple methanol lines of IRAS 19312+1950 in the λ = 3 mm, 7 mm, and 13 mm bands, and detected six lines including four thermal lines and two class I maser lines. We derived basic physical parameters, including kinetic temperature and relative abundances, by fitting a radiative transfer model. According to the derived excitation temperature and line profiles, a spherically expanding outflow lying at the center of the nebulosity is excluded from the possibilities for methanol emission regions. The detection of class I methanol maser emission suggests that a shock region is involved in the system of IRAS 19312+1950. If the central star of IRAS 19312+1950 is an evolved star as suggested in the past, the class I maser detected in the present observation is the first case detected in an interaction region between an evolved star outflow and ambient molecular gas. © The Author 2015. Published by Oxford University Press on behalf of the Astronomical Society of Japan

Anniversary of Conferences ”Physics of Space”

В статье раскрывается феномен «Коуровских астрономических школ» и вклад их руководителей Клавдии Александровны Бархатовой (1917—1990), Наталии Борисовны Фроловой (1936—2017) и Полины Евгеньевны Захаровой (1940—2020) в формирование уникальной студенческой астрономической школы-конференции. Начало положил астрономический семинар, проходивший с 4 по 7 февраля 1970 г. в Коуровской астрономической обсерватории. За минувшие десятилетия этот небольшой семинар трудами поколений астрономов вырос во Всероссийские с международным участием студенческие научные конференции «Физика Космоса». В 2023 г. состоялась юбилейная, 50-я, конференция.The article reveals the phenomenon of the ”Kourovka astronomical schools” and the contribution of their leaders: Claudia Alexandrovna Barkhatova (1917—1990), Natalia Borisovna Frolova (1936—2017) and Polina Evgenievna Zakharova (1940—2020) to the formation of a unique student astronomical conference-schools. The beginning was laid by an astronomical seminar that took place from February 4 to 7, 1970 at the Kourovka Astronomical Observatory. Over the past decades, this small seminar, through the work of generations of astronomers, has grown into Russian student scientific conferences with international participation ”Physics of Space”. In 2023, the 50th anniversary conference took place.Работа поддержана грантом РНФ 21-12-00373

Methanol in W3(H2O) and Surrounding Regions

We present the results of an interferometric study of 38 millimeter-wave lines of CH3OH in the region around the water maser source W3(H2O) and a region extending about 30" to the south and west of the hydroxyl maser source W3(OH). The methanol emitting region around W3(H2O) has an extent of 2.0" x 1.2" (4400 x 2600 AU). The density is of order 1.e7 cm-3, sufficient to thermalize most of the methanol lines. The kinetic temperature is approximately 140 K and the methanol fractional abundance greater than 1.e-6, indicative of a high degree of grain mantle evaporation. The W3(H2O) source contains sub-structure, with peaks corresponding to the TW source and Wyrowski's B/C, separated by 2500 AU in projection. The kinematics are consistent with these being distinct protostellar cores in a wide binary orbit and a dynamical mass for the region of a few tens of Mo. The extended methanol emission to the southwest of W3(OH) is seen strongly only from the lowest excitation lines and from lines known elsewhere to be class I methanol masers, namely the 84.5 GHz 5(-1)-4(0)E and 95.2 GHz 8(0)-7(1)A+ lines. Within this region there are two compact clumps, which we denote as swA and swB, each about 15" (0.16 pc projected distance) away from W3(OH). Excitation analysis of these clumps indicates the presence of lines with inverted populations but only weak amplification. The sources swA and swB appear to have kinetic temperatures of order 50-100 K and densities of order 1.e5 - 1.e6 cm-3. The methanol fractional abundance for the warmer clump is of order 1.e-7, suggestive of partial grain mantle evaporation. The clumping occurs on mass scales of order 1 Mo.Comment: 28 pages including 6 figures and 4 tables, accepted by Ap

The Warm-Up Phase in Massive Star-Forming Cores Around RCW 120

We study molecular emission in a massive condensation at the border of the H ii region RCW 120, paying particular attention to the Core 1 and 2 objects, the most massive fragments of the condensation found previously by ALMA. The latter fragment was previously suggested to host a high-mass analogue of Class 0 young stellar object. We present spectra of molecular emission in the 1 mm range made with the APEX telescope. We detect CH3OH and C34S lines in Cores 1 and 2. The CH3CN series and the SO2 lines are only found in Core 2. We estimate gas physical parameters using methanol lines and obtain gas temperature less than 100 K in both regions. Molecular hydrogen number density in Core 2 is in the range of 105-107 cm-3 and is more uncertain in Core 1. However, the detection of the CH3CN lines corresponding to highly excited transitions (Eu > 400 K) in Core 2 indicates that the region contains hot gas, while the abundances of CH3OH, CS, SO2, and CH3CN are quite low for a hot core stage. We propose that Core 2 is in the warm-up phase prior to the establishing of the hot gas chemistry. We suggest that Core 2 is in the beginning of the hot core stage. There are no detected CH3CN lines in Core 1; therefore, it might be on an even less evolved evolutionary stage. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society