We give a review of both our own original scientific results of the development of superconductin... more We give a review of both our own original scientific results of the development of superconducting receivers for sub-terahertz astronomy and the main leading concepts of the global instrumentation. The analysis of current astronomical problems, the results of microwave astroclimate research, and the development of equipment for sub-terahertz radio astronomy studies justify the need and feasibility of a major infrastructure project in Russia to create a sub-terahertz telescope, as well as to enhance the implementation of the ongoing Millimetron and Suffa projects. The following results are discussed: i) superconducting coherent receivers and broadband subterahertz detectors for space, balloon, and ground-based radio telescopes have been developed and tested; ii) ultrasensitive receiving systems based on tunnel structures such as superconductorinsulator-superconductor (SIS) and superconductor-insulator-normal metal-insulatorsuperconductor (SINIS) have been created, fabricated, and examined; iii) a receiving array based on SINIS detectors and microwave readout system for such structures has been implemented; iv) methods for manufacturing high-quality tunnel structures Nb/AlO x /Nb and Nb/AlN/NbN based on niobium films with a current density of up to 30 kA/cm 2 have been developed. Receivers operated at 200 to 950 GHz and having a noise temperature only a factor of 2 to 5 higher than the quantum limit have been created and tested.
Fourth International Conference on Terahertz and Microwave Radiation: Generation, Detection, and Applications, 2020
We are presenting the results of astroclimatic studies in the North Caucasus started on our Febru... more We are presenting the results of astroclimatic studies in the North Caucasus started on our February 2020 expedition. The main objective of the studies is to compare millimeter-wave optical depth characteristics of four North Caucasus sites: BTA-6, RATAN-600, CMO of GAISh, and the Terskol Observatory. The opacity was studied by the atmospheric dip method in the 3 mm and 2 mm atmospheric windows. The astroclimate conditions of these four sites are compared through statistically processed data. This astroclimatic analysis has been performed with the view to selecting a site for radio astronomical observations in the millimeter bandwidth.
Monthly Notices of the Royal Astronomical Society, 2021
We report a discovery of a new X-ray-selected supernova remnant (SNR) candidate SRGe J0023+3625 =... more We report a discovery of a new X-ray-selected supernova remnant (SNR) candidate SRGe J0023+3625 = G116.6−26.1 found in the SRG/eROSITA all-sky survey. The source features a large angular extent (∼4° in diameter), nearly circular shape, and X-ray spectrum dominated by emission lines of helium- and hydrogen-like oxygen. It lacks bright counterparts of similar extent at other wavelengths which could be unequivocally associated with it. Given the relatively high Galactic latitude of the source, b ≈ −26°, we interpret these observational properties as an indication of the off-disc location of this SNR candidate. Namely, we propose that this object originated from a Type Ia supernotva which exploded some 40 000 yr ago in the low density ($\sim 10^{-3}\, {\rm cm^{-3}}$) and hot ($\sim (1{-}2)\times 10^6\, {\rm K}$) gas of the Milky Way halo at a distance of ∼3 kpc from the Sun. The low density of the halo gas implies that the cooling and collisional ionization equilibrium (CEI) time-scales...
A survey of massive star forming regions in the lines of the lowest transitions of deuterated mol... more A survey of massive star forming regions in the lines of the lowest transitions of deuterated molecules DCN, DNC, DCO + , N 2 D + in the 4 mm wavelength range was performed using the 20 m radio telescope of the Onsala Space Observatory. A total of about 60 sources was observed. Lines of the DCN, DNC, and DCO + molecules are registered in about a third of them, lines of the N 2 D + molecule only in two. Estimates of the relative abundances of the molecules and deuteration degree are derived. The dependencies of these parameters and also ratios of the abundances of different deuterated molecules on temperature and velocity dispersion are analyzed. We found that the relative abundances of DCN and DNC and the DCN/HCN ratio are approximately constant in the temperature range from ~15 K to ~55 K, while relative abundance of DCO + decreases with increasing temperature. Average ratio DCN/HCN is ~10-2 for detected sources. A correlation was found between the ratios of abundances of some molecules and velocity dispersion. At the same time there are correlation between line width and temperature.
Приведены основные характеристики радиотелескопа РТ-22 КрАО на частоте 87.7 ГГц. По наблюдениям п... more Приведены основные характеристики радиотелескопа РТ-22 КрАО на частоте 87.7 ГГц. По наблюдениям планеты Венера найдены эффективная площадь и коэффициент использования диаграммы направленности. Определены форма и ширина главного лепестка диаграммы направленности. Проведено сравнение характеристик с данными 1979 г. Установлено, что эффективная площадь за годы эксплуатации РТ-22 практически не изменилась.
Results of systematic studies of high mass star forming cores and associated high velocity outflo... more Results of systematic studies of high mass star forming cores and associated high velocity outflows are reviewed. They are based on the surveys of these objects in CS, C 18 O, HNCO, SO and other molecular lines. Statistical distributions of the core parameters (mass, size, mean density, temperature, IR luminosity to mass ratio and velocity dispersion) are presented. The dependences of these parameters on galactocentric radius are analyzed. The frequency of occurrence and the basic properties of associated outflows (mass, momentum, kinetic energy) are derived. Their correlations with the bolometric luminosity of embedded IR sources are discussed.
We searched for the CS o r = 2-1 emission towards 29 southern H20 and H20/OH masers and 1 OH mase... more We searched for the CS o r = 2-1 emission towards 29 southern H20 and H20/OH masers and 1 OH maser with the SEST radio telescope. We detected and mapped 24 CS emitting regions probably associated with 27 H20 masers. The C~4S J = 2-1 and CO or = 1-0 lines were also observed at the grid positions closest to the CS peaks. Four cores were mapped in the CS or = 5-4 and Cz~S d = 2-1 lines.
ABSTRACT We present SEST observations of G345.01+1.79 in maser and `quasi-thermal' lines ... more ABSTRACT We present SEST observations of G345.01+1.79 in maser and `quasi-thermal' lines of CH3OH, lines of SiO, CS and some other shock tracing molecules. For the first time weak methanol maser emission was detected at frequencies 165.05 and 165.06 GHz. The observed `quasi-thermal' CH3OH and SiO (2-1) lines display pronounced blue wings confined to the G345.01+1.79(S) position. Velocities of CH3OH and OH maser features lie well within the wing. So, there is a high probability that interaction of the wind from the young star with ambient material is responsible for the creation of masers and production of the blue non-gaussian wing. Comparison of velocities for `quasi-thermal' and maser lines shows that the bow shock velocity relative to the bulk of cloud material is about 10 kms-1. So, most probably we are dealing with the first clear example of an ultracompact HII region moving through a molecular cloud. Modelling of CH3OH `quasi-thermal' emission and consideration of maser profiles shows that the cloud material is greatly inhomogeneous.
We present observational data for two main components (S255IR and S255N) of the S255 high mass st... more We present observational data for two main components (S255IR and S255N) of the S255 high mass star forming region in continuum and molecular lines obtained at 1.3 mm and 1.1 mm with the SMA, at 1.3 cm with the VLA and at 23 and 50 cm with the GMRT. The angular resolution was from ∼ 2 to ∼ 5 for all instruments. With the SMA we detected a total of about 50 spectral lines of 20 different molecules (including isotopologues). About half of the lines and half of the species (in particular N 2 H + , SiO, C 34 S, DCN, DNC, DCO + , HC 3 N, H 2 CO, H 2 CS, SO 2) have not been previously reported in S255IR and partly in S255N at high angular resolution. Our data reveal several new clumps in the S255IR and S255N areas by their millimeter wave continuum emission. Masses of these clumps are estimated at a few solar masses. The line widths greatly exceed expected thermal widths. These clumps have practically no association with NIR or radio continuum sources, implying a very early stage of evolution. At the same time, our SiO data indicate the presence of high-velocity outflows related to some of these clumps. In some cases, strong molecular emission at velocities of the quiescent gas has no detectable counterpart in the continuum. We discuss the main features of the distribution of NH 3 , N 2 H + , and deuterated molecules. We estimate properties of decimeter wave radio continuum sources and their relationship with the molecular material.
New challenges in submillimeter wave astronomy require instruments with a combination of high sen... more New challenges in submillimeter wave astronomy require instruments with a combination of high sensitivity andangular resolution, wide field of view and multiwave (multicolor)spectral range. New large single mm/submm telescopes are in high demand, as well as their inclusion in the global Event Horizon Telescope (EHT) VLBI network. At the same time, there are no large mm/submm telescopes in Asia at allwhile appropriate sites exist and their appearance in Asia or Eurasia is long overdue.Kinetic inductance detectors (KID) are ideal for large-format array implementation, which will be necessary for future telescope development. Concept of multicolor subTHzKID-array MUSICAM demo camera and its instrumental testing is given. It allows us to perform some necessary steps toward the creation of the Eurasian SubMillimeter Telescopes (ESMT), which concept and scientific tasks are presented as well.
We present line and continuum observations (resolution ∼0.″3–3.″5) made with the Atacama Large Mi... more We present line and continuum observations (resolution ∼0.″3–3.″5) made with the Atacama Large Millimeter/submillimeter Array (ALMA), Submillimeter Array, and Very Large Array of a young O-type protostar W42-MME (mass: 19 ± 4 M ⊙). The ALMA 1.35 mm continuum map (resolution ∼1″) shows that W42-MME is embedded in one of the cores (i.e., MM1) located within a thermally supercritical filament-like feature (extent ∼0.15 pc) containing three cores (mass ∼1–4.4 M ⊙). Several dense/hot gas tracers are detected toward MM1, suggesting the presence of a hot molecular core with a gas temperature of ∼38–220 K. The ALMA 865 μm continuum map (resolution ∼0.″3) reveals at least five continuum sources/peaks (A–E) within a dusty envelope (extent ∼9000 au) toward MM1, where shocks are traced in the SiO (8–7) emission. Source A associated with W42-MME is seen almost at the center of the dusty envelope and is surrounded by other continuum peaks. The ALMA CO (3–2) and SiO (8–7) line observations show th...
Monthly Notices of the Royal Astronomical Society: Letters
A supernova remnant (SNR) candidate SRGe J0023+3625 = G116.6-26.1 was recently discovered in the ... more A supernova remnant (SNR) candidate SRGe J0023+3625 = G116.6-26.1 was recently discovered in the SRG/eROSITA all-sky X-ray survey. This large (∼4 deg in diameter) SNR candidate lacks prominent counterparts in other bands. Here we report detection of radio emission from G116.6-26.1 in the LOFAR Two-metre Sky Survey (LoTTS-DR2). Radio images show a shell-like structure coincident with the X-ray boundary of the SNR. The measured surface brightness of radio emission from this SNR is very low. Extrapolation of the observed surface brightness to 1 GHz places G116.6-26.1 well below other objects in the Σ − D diagram. We argue that the detected radio flux might be consistent with the minimal level expected in the van der Laan adiabatic compression model, provided that the volume emissivity of the halo gas in the LOFAR band is ∼10−42 Wm−3Hz−1sr−1. If true, this SNR can be considered as a prototypical example of an evolved SNR in the Milky Way halo. In the X-ray and radio bands, such SNRs can...
We are presenting results of the observations our research group has been conducting for about 7 ... more We are presenting results of the observations our research group has been conducting for about 7 years. Over this time, we have gathered statistical data from a number of sites which can be used for radio astronomical observations in the millimetre and sub-millimetre bandwidths. We have just finished a year-long cycle of tests in Svalbard and are now able to compare its atmospheric transparency with other sites. The astroclimatic analysis is a prerequisite for selecting a site for radio astronomical observations in the millimetre bandwidth.
We report the discovery of a very dense jet-like fast molecular outflow surrounded by a wide-angl... more We report the discovery of a very dense jet-like fast molecular outflow surrounded by a wide-angle wind in a massive young stellar object (MYSO) G18.88MME (stellar mass∼8 M⊙) powering an Extended Green Object G18.89−0.47.Four cores MM1–4 are identified in the Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum map (resolution ∼0.8) toward G18.88MME, and are seen at the center of the emission structure (extent ∼0.3 pc × 0.2 pc) detected in the ALMA map. G18.88MME is embedded in the core MM1 (mass ∼13–18 M⊙), where no radio continuum emission is detected. The molecular outflow centered at MM1 is investigated in the SiO(5–4), HC3N(24–23) and CO(2–1) lines. The detection of HC3N in the outflow is rare in MYSOs and indicates its very high density. The position-velocity diagrams display a fast narrow outflow (extent ∼28000 AU) and a slower wide-angle more extended outflow toward MM1, and both of these components show a transverse velocity gradient indicative of a possible...
We investigate at a high angular resolution the spatial and kinematic structure of the S255IR hig... more We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high-mass starforming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 7 at an angular resolution of ∼ 0 1, which corresponds to ∼180au. The 0.9mm continuum, C 34 S(7-6) and CCH N=4−3 data show a presence of very narrow (∼1000 au), very dense (n ∼ 10 7 cm −3), and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low-or intermediate-mass protostars. The C 34 S emission shows evidence of rotation of the parent core. Finally, we detected two new low-mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.
We present new CO (13 CO(1-0) and C 18 O(1-0)) and CS(2-1) line observations of an elongated fila... more We present new CO (13 CO(1-0) and C 18 O(1-0)) and CS(2-1) line observations of an elongated filamentary structure (length ∼30 pc) in the star-forming site S242, which were taken with the OSO-20 m telescope. One filament's end hosts the S242 H II region, while the other end contains Planck cold clumps. Several subregions are identified in the filament, and are supersonic with Mach number of 2.7-4.0. The study of the dynamical states shows supercritical nature of the subregions (except the central part), which could not be supported by a combination of thermal and turbulent motions. Young stellar objects are seen toward the entire filament, but are more concentrated toward its ends. Dense molecular cores are observed mainly toward the filament ends, and are close to virial equilibrium. Position-velocity plots trace velocity gradients (∼1 km s −1 pc −1) toward both ends. An oscillatory pattern in velocity is also observed toward the filament, indicating its fragmentation. The collapse timescale of the filament is computed to be ∼3.5 Myr. Using the 13 CO data, the structure function in velocity of the filament is found to be very similar as that seen in the Musca cloud for lags ∼1-3pc, and deviates from the Larson's velocity-size relationship. The observed oscillatory pattern in the structure function at higher lags suggests the existence of large-scale and ordered velocity gradients, as well as the fragmentation process through accretion along the filament. Considering all the observed results along with their uncertainties, the S242 filament is a very good example of the end-dominated collapse.
We give a review of both our own original scientific results of the development of superconductin... more We give a review of both our own original scientific results of the development of superconducting receivers for sub-terahertz astronomy and the main leading concepts of the global instrumentation. The analysis of current astronomical problems, the results of microwave astroclimate research, and the development of equipment for sub-terahertz radio astronomy studies justify the need and feasibility of a major infrastructure project in Russia to create a sub-terahertz telescope, as well as to enhance the implementation of the ongoing Millimetron and Suffa projects. The following results are discussed: i) superconducting coherent receivers and broadband subterahertz detectors for space, balloon, and ground-based radio telescopes have been developed and tested; ii) ultrasensitive receiving systems based on tunnel structures such as superconductorinsulator-superconductor (SIS) and superconductor-insulator-normal metal-insulatorsuperconductor (SINIS) have been created, fabricated, and examined; iii) a receiving array based on SINIS detectors and microwave readout system for such structures has been implemented; iv) methods for manufacturing high-quality tunnel structures Nb/AlO x /Nb and Nb/AlN/NbN based on niobium films with a current density of up to 30 kA/cm 2 have been developed. Receivers operated at 200 to 950 GHz and having a noise temperature only a factor of 2 to 5 higher than the quantum limit have been created and tested.
Fourth International Conference on Terahertz and Microwave Radiation: Generation, Detection, and Applications, 2020
We are presenting the results of astroclimatic studies in the North Caucasus started on our Febru... more We are presenting the results of astroclimatic studies in the North Caucasus started on our February 2020 expedition. The main objective of the studies is to compare millimeter-wave optical depth characteristics of four North Caucasus sites: BTA-6, RATAN-600, CMO of GAISh, and the Terskol Observatory. The opacity was studied by the atmospheric dip method in the 3 mm and 2 mm atmospheric windows. The astroclimate conditions of these four sites are compared through statistically processed data. This astroclimatic analysis has been performed with the view to selecting a site for radio astronomical observations in the millimeter bandwidth.
Monthly Notices of the Royal Astronomical Society, 2021
We report a discovery of a new X-ray-selected supernova remnant (SNR) candidate SRGe J0023+3625 =... more We report a discovery of a new X-ray-selected supernova remnant (SNR) candidate SRGe J0023+3625 = G116.6−26.1 found in the SRG/eROSITA all-sky survey. The source features a large angular extent (∼4° in diameter), nearly circular shape, and X-ray spectrum dominated by emission lines of helium- and hydrogen-like oxygen. It lacks bright counterparts of similar extent at other wavelengths which could be unequivocally associated with it. Given the relatively high Galactic latitude of the source, b ≈ −26°, we interpret these observational properties as an indication of the off-disc location of this SNR candidate. Namely, we propose that this object originated from a Type Ia supernotva which exploded some 40 000 yr ago in the low density ($\sim 10^{-3}\, {\rm cm^{-3}}$) and hot ($\sim (1{-}2)\times 10^6\, {\rm K}$) gas of the Milky Way halo at a distance of ∼3 kpc from the Sun. The low density of the halo gas implies that the cooling and collisional ionization equilibrium (CEI) time-scales...
A survey of massive star forming regions in the lines of the lowest transitions of deuterated mol... more A survey of massive star forming regions in the lines of the lowest transitions of deuterated molecules DCN, DNC, DCO + , N 2 D + in the 4 mm wavelength range was performed using the 20 m radio telescope of the Onsala Space Observatory. A total of about 60 sources was observed. Lines of the DCN, DNC, and DCO + molecules are registered in about a third of them, lines of the N 2 D + molecule only in two. Estimates of the relative abundances of the molecules and deuteration degree are derived. The dependencies of these parameters and also ratios of the abundances of different deuterated molecules on temperature and velocity dispersion are analyzed. We found that the relative abundances of DCN and DNC and the DCN/HCN ratio are approximately constant in the temperature range from ~15 K to ~55 K, while relative abundance of DCO + decreases with increasing temperature. Average ratio DCN/HCN is ~10-2 for detected sources. A correlation was found between the ratios of abundances of some molecules and velocity dispersion. At the same time there are correlation between line width and temperature.
Приведены основные характеристики радиотелескопа РТ-22 КрАО на частоте 87.7 ГГц. По наблюдениям п... more Приведены основные характеристики радиотелескопа РТ-22 КрАО на частоте 87.7 ГГц. По наблюдениям планеты Венера найдены эффективная площадь и коэффициент использования диаграммы направленности. Определены форма и ширина главного лепестка диаграммы направленности. Проведено сравнение характеристик с данными 1979 г. Установлено, что эффективная площадь за годы эксплуатации РТ-22 практически не изменилась.
Results of systematic studies of high mass star forming cores and associated high velocity outflo... more Results of systematic studies of high mass star forming cores and associated high velocity outflows are reviewed. They are based on the surveys of these objects in CS, C 18 O, HNCO, SO and other molecular lines. Statistical distributions of the core parameters (mass, size, mean density, temperature, IR luminosity to mass ratio and velocity dispersion) are presented. The dependences of these parameters on galactocentric radius are analyzed. The frequency of occurrence and the basic properties of associated outflows (mass, momentum, kinetic energy) are derived. Their correlations with the bolometric luminosity of embedded IR sources are discussed.
We searched for the CS o r = 2-1 emission towards 29 southern H20 and H20/OH masers and 1 OH mase... more We searched for the CS o r = 2-1 emission towards 29 southern H20 and H20/OH masers and 1 OH maser with the SEST radio telescope. We detected and mapped 24 CS emitting regions probably associated with 27 H20 masers. The C~4S J = 2-1 and CO or = 1-0 lines were also observed at the grid positions closest to the CS peaks. Four cores were mapped in the CS or = 5-4 and Cz~S d = 2-1 lines.
ABSTRACT We present SEST observations of G345.01+1.79 in maser and `quasi-thermal' lines ... more ABSTRACT We present SEST observations of G345.01+1.79 in maser and `quasi-thermal' lines of CH3OH, lines of SiO, CS and some other shock tracing molecules. For the first time weak methanol maser emission was detected at frequencies 165.05 and 165.06 GHz. The observed `quasi-thermal' CH3OH and SiO (2-1) lines display pronounced blue wings confined to the G345.01+1.79(S) position. Velocities of CH3OH and OH maser features lie well within the wing. So, there is a high probability that interaction of the wind from the young star with ambient material is responsible for the creation of masers and production of the blue non-gaussian wing. Comparison of velocities for `quasi-thermal' and maser lines shows that the bow shock velocity relative to the bulk of cloud material is about 10 kms-1. So, most probably we are dealing with the first clear example of an ultracompact HII region moving through a molecular cloud. Modelling of CH3OH `quasi-thermal' emission and consideration of maser profiles shows that the cloud material is greatly inhomogeneous.
We present observational data for two main components (S255IR and S255N) of the S255 high mass st... more We present observational data for two main components (S255IR and S255N) of the S255 high mass star forming region in continuum and molecular lines obtained at 1.3 mm and 1.1 mm with the SMA, at 1.3 cm with the VLA and at 23 and 50 cm with the GMRT. The angular resolution was from ∼ 2 to ∼ 5 for all instruments. With the SMA we detected a total of about 50 spectral lines of 20 different molecules (including isotopologues). About half of the lines and half of the species (in particular N 2 H + , SiO, C 34 S, DCN, DNC, DCO + , HC 3 N, H 2 CO, H 2 CS, SO 2) have not been previously reported in S255IR and partly in S255N at high angular resolution. Our data reveal several new clumps in the S255IR and S255N areas by their millimeter wave continuum emission. Masses of these clumps are estimated at a few solar masses. The line widths greatly exceed expected thermal widths. These clumps have practically no association with NIR or radio continuum sources, implying a very early stage of evolution. At the same time, our SiO data indicate the presence of high-velocity outflows related to some of these clumps. In some cases, strong molecular emission at velocities of the quiescent gas has no detectable counterpart in the continuum. We discuss the main features of the distribution of NH 3 , N 2 H + , and deuterated molecules. We estimate properties of decimeter wave radio continuum sources and their relationship with the molecular material.
New challenges in submillimeter wave astronomy require instruments with a combination of high sen... more New challenges in submillimeter wave astronomy require instruments with a combination of high sensitivity andangular resolution, wide field of view and multiwave (multicolor)spectral range. New large single mm/submm telescopes are in high demand, as well as their inclusion in the global Event Horizon Telescope (EHT) VLBI network. At the same time, there are no large mm/submm telescopes in Asia at allwhile appropriate sites exist and their appearance in Asia or Eurasia is long overdue.Kinetic inductance detectors (KID) are ideal for large-format array implementation, which will be necessary for future telescope development. Concept of multicolor subTHzKID-array MUSICAM demo camera and its instrumental testing is given. It allows us to perform some necessary steps toward the creation of the Eurasian SubMillimeter Telescopes (ESMT), which concept and scientific tasks are presented as well.
We present line and continuum observations (resolution ∼0.″3–3.″5) made with the Atacama Large Mi... more We present line and continuum observations (resolution ∼0.″3–3.″5) made with the Atacama Large Millimeter/submillimeter Array (ALMA), Submillimeter Array, and Very Large Array of a young O-type protostar W42-MME (mass: 19 ± 4 M ⊙). The ALMA 1.35 mm continuum map (resolution ∼1″) shows that W42-MME is embedded in one of the cores (i.e., MM1) located within a thermally supercritical filament-like feature (extent ∼0.15 pc) containing three cores (mass ∼1–4.4 M ⊙). Several dense/hot gas tracers are detected toward MM1, suggesting the presence of a hot molecular core with a gas temperature of ∼38–220 K. The ALMA 865 μm continuum map (resolution ∼0.″3) reveals at least five continuum sources/peaks (A–E) within a dusty envelope (extent ∼9000 au) toward MM1, where shocks are traced in the SiO (8–7) emission. Source A associated with W42-MME is seen almost at the center of the dusty envelope and is surrounded by other continuum peaks. The ALMA CO (3–2) and SiO (8–7) line observations show th...
Monthly Notices of the Royal Astronomical Society: Letters
A supernova remnant (SNR) candidate SRGe J0023+3625 = G116.6-26.1 was recently discovered in the ... more A supernova remnant (SNR) candidate SRGe J0023+3625 = G116.6-26.1 was recently discovered in the SRG/eROSITA all-sky X-ray survey. This large (∼4 deg in diameter) SNR candidate lacks prominent counterparts in other bands. Here we report detection of radio emission from G116.6-26.1 in the LOFAR Two-metre Sky Survey (LoTTS-DR2). Radio images show a shell-like structure coincident with the X-ray boundary of the SNR. The measured surface brightness of radio emission from this SNR is very low. Extrapolation of the observed surface brightness to 1 GHz places G116.6-26.1 well below other objects in the Σ − D diagram. We argue that the detected radio flux might be consistent with the minimal level expected in the van der Laan adiabatic compression model, provided that the volume emissivity of the halo gas in the LOFAR band is ∼10−42 Wm−3Hz−1sr−1. If true, this SNR can be considered as a prototypical example of an evolved SNR in the Milky Way halo. In the X-ray and radio bands, such SNRs can...
We are presenting results of the observations our research group has been conducting for about 7 ... more We are presenting results of the observations our research group has been conducting for about 7 years. Over this time, we have gathered statistical data from a number of sites which can be used for radio astronomical observations in the millimetre and sub-millimetre bandwidths. We have just finished a year-long cycle of tests in Svalbard and are now able to compare its atmospheric transparency with other sites. The astroclimatic analysis is a prerequisite for selecting a site for radio astronomical observations in the millimetre bandwidth.
We report the discovery of a very dense jet-like fast molecular outflow surrounded by a wide-angl... more We report the discovery of a very dense jet-like fast molecular outflow surrounded by a wide-angle wind in a massive young stellar object (MYSO) G18.88MME (stellar mass∼8 M⊙) powering an Extended Green Object G18.89−0.47.Four cores MM1–4 are identified in the Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum map (resolution ∼0.8) toward G18.88MME, and are seen at the center of the emission structure (extent ∼0.3 pc × 0.2 pc) detected in the ALMA map. G18.88MME is embedded in the core MM1 (mass ∼13–18 M⊙), where no radio continuum emission is detected. The molecular outflow centered at MM1 is investigated in the SiO(5–4), HC3N(24–23) and CO(2–1) lines. The detection of HC3N in the outflow is rare in MYSOs and indicates its very high density. The position-velocity diagrams display a fast narrow outflow (extent ∼28000 AU) and a slower wide-angle more extended outflow toward MM1, and both of these components show a transverse velocity gradient indicative of a possible...
We investigate at a high angular resolution the spatial and kinematic structure of the S255IR hig... more We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high-mass starforming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 7 at an angular resolution of ∼ 0 1, which corresponds to ∼180au. The 0.9mm continuum, C 34 S(7-6) and CCH N=4−3 data show a presence of very narrow (∼1000 au), very dense (n ∼ 10 7 cm −3), and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low-or intermediate-mass protostars. The C 34 S emission shows evidence of rotation of the parent core. Finally, we detected two new low-mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.
We present new CO (13 CO(1-0) and C 18 O(1-0)) and CS(2-1) line observations of an elongated fila... more We present new CO (13 CO(1-0) and C 18 O(1-0)) and CS(2-1) line observations of an elongated filamentary structure (length ∼30 pc) in the star-forming site S242, which were taken with the OSO-20 m telescope. One filament's end hosts the S242 H II region, while the other end contains Planck cold clumps. Several subregions are identified in the filament, and are supersonic with Mach number of 2.7-4.0. The study of the dynamical states shows supercritical nature of the subregions (except the central part), which could not be supported by a combination of thermal and turbulent motions. Young stellar objects are seen toward the entire filament, but are more concentrated toward its ends. Dense molecular cores are observed mainly toward the filament ends, and are close to virial equilibrium. Position-velocity plots trace velocity gradients (∼1 km s −1 pc −1) toward both ends. An oscillatory pattern in velocity is also observed toward the filament, indicating its fragmentation. The collapse timescale of the filament is computed to be ∼3.5 Myr. Using the 13 CO data, the structure function in velocity of the filament is found to be very similar as that seen in the Musca cloud for lags ∼1-3pc, and deviates from the Larson's velocity-size relationship. The observed oscillatory pattern in the structure function at higher lags suggests the existence of large-scale and ordered velocity gradients, as well as the fragmentation process through accretion along the filament. Considering all the observed results along with their uncertainties, the S242 filament is a very good example of the end-dominated collapse.
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Papers by Igor Zinchenko