Database of Molecular Masers and Variable Stars

We present the database of maser sources in H2O, OH and SiO lines that can be used to identify and study variable stars at evolved stages. Detecting the maser emission in H2O, OH and SiO molecules toward infrared-excess objects is one of the methods of identification long-period variables (LPVs, including Miras and Semi-Regular), because these stars exhibit maser activity in their circumstellar shells. Our sample contains 1803 known LPV objects. 46% of these stars (832 objects) manifest maser emission in the line of at least one molecule: H2O, OH or SiO. We use the database of circumstellar masers in order to search for long-periodic variables which are not included in the General Catalogue of Variable Stars (GCVS). Our database contains 4806 objects (3866 objects without associations in GCVS catalog) with maser detection in at least one molecule. Therefore it is possible to use the database in order to locate and study the large sample of long-period variable stars. Entry to the database at http://maserdb.netComment: Accepted for publication in RA

Molecular Emission in Dense Massive Clumps from the Star-Forming Regions S231-S235

The article deals with observations of star-forming regions S231-S235 in 'quasi-thermal' lines of ammonia (NH$_3$), cyanoacetylene (HC$_3$N) and maser lines of methanol (CH$_3$OH) and water vapor (H$_2$O). S231-S235 regions is situated in the giant molecular cloud G174+2.5. We selected all massive molecular clumps in G174+2.5 using archive CO data. For the each clump we determined mass, size and CO column density. After that we performed observations of these clumps. We report about first detections of NH$_3$ and HC$_3$N lines toward the molecular clumps WB89 673 and WB89 668. This means that high-density gas is present there. Physical parameters of molecular gas in the clumps were estimated using the data on ammonia emission. We found that the gas temperature and the hydrogen number density are in the ranges 16-30 K and 2.8-7.2$\times10^3$ cm$^{-3}$, respectively. The shock-tracing line of CH$_3$OH molecule at 36.2 GHz is newly detected toward WB89 673.Comment: 16 pages, 4 figure

Star formation in the S233 region

The main objective of this paper is to study the possibility of triggered star formation on the border of the HII region S233, which is formed by a B-star. Using high-resolution spectra we determine the spectral class of the ionizing star as B0.5 V and the radial velocity of the star to be -17.5(1.4) km/s. This value is consistent with the velocity of gas in a wide field across the S233 region, suggesting that the ionizing star was formed from a parent cloud belonging to the S233 region. By studying spatial-kinematic structure of the molecular cloud in the S233 region, we detected an isolated clump of gas producing CO emission red-shifted relative to the parent cloud. In the UKIDSS and WISE images, the clump of gas coincides with the infrared source containing a compact object and bright-rimmed structure. The bright-rimmed structure is perpendicular to the direction of the ionizing star. The compact source coincides in position with IRAS source 05351+3549. All these features indicate a possibility of triggering formation of a next-generation star in the S233 region. Within the framework of a theoretical one-dimensional model we conclude that the "collect-and-collapse" process is not likely to take place in the S233 region. The presence of the bright-rimmed structure and the compact infrared source suggest that the "collapse of the pre-existing clump" process is taking place.Comment: 12 pages, 10 figure

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

A technique for describing line profiles of the CO molecule using a multi-component radiation transfer model

В настоящей работе исследованы особенности анализа профилей линий молекулы CO в гигантских молекулярных облаках (ГМО). С помощью различных инструментов анализа разработана методика, позволяющая в рамках локального термодинамического равновесия использовать несколько линий излучения молекулы CO для построения и оптимизации модели и определения физических параметров ГМО. Методика включает выделение сгустков с помощью алгоритма GAUSSCLUMP, а также автоматизированное построение многослойной модели переноса излучения для сгустков с использованием методов оптимизации и Монте-Карло. Методика применена на практике для анализа крупномасштабного картографирования комплекса звездообразования S231-S235 в четырех различных линиях CO.In this work, we investigated the features of the analysis of complex CO line profiles in giant molecular clouds (GMCs). A technique has been developed to use several emission lines of the CO molecule to build a model and determine GMCs physical parameters within the local thermodynamic equilibrium framework. The technique includes clumps extraction using the GAUSSCLUMP algorithm and constructing a multilayer radiation transfer model for clumps using optimization and Monte Carlo methods. The technique was applied to analyze largescale mapping of the S231-S235 star formation complex in four different CO lines.Работа выполнена при поддержке гранта РФФИ № 18-02-00917

Online database of water masers in the star-forming regions: the first results

Представлены первые результаты разработки базы данных водяных мазеров в областях звездообразования. База данных в настоящий момент доступна в режиме онлайн по адресу: http://maserdb.net. Степень покрытия базы данных на момент публикации составляет 84 % от всех регистраций водяных мазеров в областях звездообразования из доступной литературы. Выполнена первичная статистическая обработка данных и проведено совместное исследование водяных мазеров и источников излучения в континууме на 870 мкм по данным обзора ATLASGAL. При помощи обобщенной линейной модели получено соотношение, позволяющее оценить вероятность обнаружения водяного мазера в зависимости от физических параметров сгустков из каталога ATLASGAL. По оценке, в настоящий момент зарегистрировано лишь ∼25 % от общего числа водяных мазеров в направлении на источники ATLASGAL.The first results of developing a database of water masers in star-forming regions are presented. The database is stored online at the address http://maserdb.net. The coverage of the database at the time of publication is 84 % of all positive detections of water masers in star-forming regions from the available literature. Preliminary statistical analysis of the data and study of the association between water masers and ATLASGAL 870 μm sources was carried out. A relation was obtained from the generalized linear model to estimate water maser detection probability depending on the physical parameters of clumps from the ATLASGAL catalogue. According to estimates, only ∼25 % of the total number of water masers towards ATLASGAL sources has been detected at the moment.Работа выполнена при поддержке гранта РНФ № 20-72-00137

Study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex

We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide (CO), ammonia (NH$_3$), carbon monosulfide (CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, its fragmentation and physical parameters. The gas temperature is derived from the NH$_3$ $(J,K) = (1,1), (2,2)$ and $^{12}$CO(2--1) lines and the $^{13}$CO(1--0), $^{13}$CO(2--1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2--1) data. Values of the gas temperature lie in the ranges $10-35$ K, column density $N(\mathrm{H}_2)$ reaches the value 5.1 10$^{22}$ cm$^{-2}$. The width of the filament is of order 1 pc. The masses of the dense clumps range from $\sim 30$ M$_\odot$ to $\sim 160$ M$_\odot$. They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse.Comment: 10 pages, 9 figures, accepted for publication in Research in Astronomy and Astrophysic

Giant molecular cloud scaling relations: The role of the cloud definition

We investigate the physical properties of molecular clouds in disc galaxies with different morphologies: a galaxy without prominent structure, a spiral barred galaxy and a galaxy with flocculent structure. Our N-body/hydrodynamical simulations take into account nonequilibrium H2 and CO chemical kinetics, self-gravity, star formation and feedback processes. For the simulated galaxies, the scaling relations of giant molecular clouds, or so-called Larson's relations, are studied for two types of cloud definition (or extraction method): the first is based on total column density position-position (PP) data sets and the second is indicated by the CO (1-0) line emission used in position-position-velocity (PPV) data. We find that the cloud populations obtained using both cloud extraction methods generally have similar physical parameters, except that for the CO data the mass spectrum of clouds has a tail with low-mass objects M∼103-104 M⊙. Owing toa varying column density threshold, the power-law indices in the scaling relations are significantly changed. In contrast, the relations are invariant to the CO brightness temperature threshold. Finally, we find that the mass spectra of clouds for PPV data are almost insensitive to the galactic morphology, whereas the spectra for PP data demonstrate significant variation. © 2015 The Authors.Bauman Moscow State Technical University, Bauman MSTURussian Science Foundation, RSF: 14-22-00041Russian Foundation for Basic Research, RFBR: MK-4536.2015.2, 15-32-21062, 14-02-00604, 15-02-06204Russian Academy of Sciences, RASMinistero dellâ Istruzione, dellâ Università e della Ricerca, MIUR14-50-00043Ministry of Education and Science of the Russian Federation, Minobrnauka: 3.1781.2014/K, 15-52-45114, 15-02-08293, 2663We thank our referee, Erik Rosolwski, kindly for thoughtful suggestions that greatly improved the quality of the article. We also thank Marco Lombardi for several stimulating discussions and for reading the early versions of the manuscript. The numerical simulations have been performed at the Research Computing Center (Moscow State University) under a Russian Science Foundation grant (14-22-00041) and Joint Supercomputer Center (Russian Academy of Sciences). This work was supported by RFBR grants (14-02-00604, 15-02-06204, 15-32-21062) and by a President of the RF grant (MK-4536.2015.2). SAK has been supported by a postdoctoral fellowship sponsored by the Italian MIUR. AMS has been supported by the Ministry of Education and Science of the Russian Federation within the framework of the research activities (project no. 3.1781.2014/K). This work was also supported by Act 211 Government of the Russian Federation, contract no 02.A03.21.0006. EOV is thankful to the Ministry of Education and Science of the Russian Federation (project 2663) and RFBR (projects 15-02-08293 and 15-52-45114). The thermochemical part was developed under support from the Russian Scientific Foundation (grant 14-50-00043)

Study of the high-density gas in star-formation region S255-S258

Для исследования плотного газа в области звездообразования S255-S258 были получены карты трассеров различной плотности газа, в том числе карта излучения молекулы HCO+ по собственным данным, карта поглощения в цвете V, карта лучевой концентрации молекулы CO, а также карта излучения в континууме на длине волны 1.1 мм. Была исследована корреляция между распределением молодых зведных объектов и плотным газом на разных пространственных масштабах. В результате получено, что наибольшая (> 50 %) корреляция наблюдается на масштабах более 1.5 угловые минуты между молодыми звездными объектами I класса и трассерами плотного газа картой поглощения, излучения HCO+ и излучения в континууме на длине волны 1.1 мм. Высокая корреляция между молодыми звездными объектами I класса и трассерами плотного газа показывает эволюционную связь между плотным газом и наиболее молодыми звездными объектами I класса.To study the dense gas in the star formation region S255-S258 we use tracers of different gas density, including HCO+ line emission, extinction map, CO column density map and Bolocam continuum emission at 1.1 mm. The correlation between the distribution of young stellar objects and dense gas at different spatial scales was studied. As a result, it was found that the closest (> 50 %) correlation is observed at the scales greater than 1.5 arcmin between the young stellar objects of Class I and tracers of dense gas — extinction maps, HCO+ emissions and continuum emission at a wavelength of 1.1 mm. A high correlation between the young stellar objects of Class I and the tracers of dense gas reveal the evolutionary connection between dense gas and the youngest stellar objects of Class I

Creation of the web-based database of maser sources

Для решения проблемы поиска и систематизации данных по астрономическим мазерным источникам был создан программный код, работающий в режиме онлайн, предназначенный для хранения, анализа и визуализации данных о мазерных источниках. Система предназначена для хранения больших объемов данных по мазерному излучению в различных линиях межзвездной среды, в том числе с учетом отрицательных регистраций. Имеется возможность отождествления мазерных источников с данными из популярных астрономических каталогов. В настоящий момент система успешно применена для проекта eDAMS extensive Database of Astrophysical Maser Sources, целью которого является сбор наиболее полных сведений об околозвездных мазерных источниках в линиях H2O, OH и SiO. Для этой цели уже собрано более 25 тыс. наблюдений из различных источников в 10 тыс. объектах. Адрес сайта для ознакомления с возможностями системы http://maserdb.ins.urfu.ru.To solve the problem of searching and collecting the data of astronomical maser sources, the Web-based code was developed in order to store, analyze and visualize the data of astronomical masers. The system is designed to store large amounts of data on maser emission in various lines of the interstellar medium, including negative results. Cross-checking of maser sources with popular astronomical catalogs is implemented. At the moment, the system has been successfully applied for the eDAMS project — the Extensive Database of Astrophysical Maser Sources, whose goal is to collect the complete information about circumstellar maser sources in the H2O, OH and SiO lines. For this purpose, more than 25 000 observations from various sources in 10 thousand objects have already been collected. Current internet-address of the system is http://maserdb.ins.urfu.ru