H13^{13}CN-HN13^{13}C intensity ratio as a temperature indicator of interstellar clouds

With the 30-m IRAM radio telescope, we observed several massive star forming regions at wavelengths of 3-4 and 2 mm. The temperature of the gas in the sources was estimated from the lines of CH$_{3}$CCH and from the transitions of the NH$_3$ molecule obtained during observations at the 100-m radio telescope in Effelsberg. As a result, a correlation between the integrated intensity ratios of the $J=1-0$ transitions of H$^{13}$CN and HN$^{13}$C and the kinetic temperature has been obtained. The obtained results allow us to propose the use of the intensity ratio H$^{13}$CN-HN$^{13}$C as a possible temperature indicator of interstellar clouds. We also compared the obtained estimates of the kinetic temperature with the dust temperature $T_{dust}$. As a result, no significant correlation was found.Comment: 16 pages, 7 figures, 2 tables, Accepted for publication in Astronomy Reports (2022

Deuterated molecules in regions of high-mass star formation

We present the results of our studies of deuterated molecules (DCN, DNC, DCO$^+$, N$_2$D$^+$ and NH$_2$D) in regions of high-mass star formation, which include a survey of such regions with the 20-m Onsala radio telescope and mapping of several objects in various lines with the 30-m IRAM and 100-m MPIfR radio telescopes. The deuteration degree reaches $\sim$10$^{-2}$ in these objects. We discuss its dependencies on the gas temperature and velocity dispersion, as well as spatial distributions of deuterated molecules. We show that the H$^{13}$CN/HN$^{13}$C intensity ratio may be a good indicator of the gas kinetic temperature and estimate densities of the investigated objects.Comment: 8 pages, 4 figures, to be published in Proceedings of Science (Proceedings of the conference "The Multifaceted Universe: Theory and Observations - 2022", 23-27 May 2022, SAO RAS, Nizhny Arkhyz, Russia

Fragmentation and dynamics of dense gas structures in the proximity of massive young stellar object W42-MME

We present an analysis of the dense gas structures in the immediate surroundings of the massive young stellar object (MYSO) W42-MME, using the high-resolution (0$''$.31$\times$0$''$.25) ALMA dust continuum and molecular line data. We performed a dendrogram analysis of H$^{13}$CO$^{+}$ (4-3) line data to study multi-scale structures and their spatio-kinematic properties, and analyzed the fragmentation and dynamics of dense structures down to $\sim$2000 AU scale. Our results reveal 19 dense gas structures, out of which 12 are leaves and 7 are branches in dendrogram terminology. These structures exhibit transonic-supersonic gas motions (1$<\mathcal{M}<5$) with overvirial states ($\alpha_{\rm vir}\geq2$). The non-thermal velocity dispersion-size relation ($\sigma_{\rm nt}-L$) of dendrogram structures shows a weak negative correlation, while the velocity dispersion across the sky ($\delta\mathit{V_{\rm lsr}}$) correlates positively with structure size ($L$). Velocity structure function ($S_{2}(l)^{1/2}$) analysis of H$^{13}$CO$^{+}$ data reveals strong power-law dependencies with lag ($l$) up to a scale length of $\lesssim$ 6000 AU. The mass-size ($M-R$) relation of dendrogram structures shows a positive correlation with power-law index of 1.73$\pm$0.23, and the leaf L17 hosting W42-MME meets the mass-size conditions for massive star formation. Blue asymmetry is observed in the H$^{12}$CO$^{+}$ (4-3) line profiles of most of the leaves, indicating infall. Overall, our results observationally support the hierarchical and chaotic collapse scenario in the proximity of the MYSO W42-MME.Comment: 16 pages, 13 figures, 1 Table, Accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) Journa

Deuterated Molecules and Temperature in Interstellar Clouds

В работе используются спектры и карты DCO+, DCN, DNC и NH2D, полученные на 30-м телескопе IRAM, для изучения процессов обогащения молекулярного газа дейтерием в пяти областях образования массивных звезд. Температура оценивалась по линиям CH3CCH и NH3, полученным при наблюдениях на 100-м радиотелескопе в Эффельсберге, а также по отношению интегральных интенсивностей переходов J = 1 − 0 H13CN и HN13C. Лучевые концентрации молекул были получены в предположении условий отличных от ЛТР. В результате мы обнаружили, что отношения D/H DCO+, DCN и DNC уменьшаются с температурой. Однако мы не обнаружили корреляций отношения D/H для NH2D.We use spectra and maps of DCO+, DCN, DNC and NH2D, obtained with the IRAM 30-m telescope, to study deuteration processes in five massive star forming regions. The temperature was estimated from the lines of CH3CCH and NH3 obtained during observations at the 100-m radio telescope in Effelsberg, as well as using the integrated intensity ratio of the J = 1−0 transitions of H13CN and HN13C. The column densities of molecules were obtained under the assumption of non-LTE conditions. As a result, we found the D/H ratios of DCO+, DCN and DNC decrease with the temperature. However, we found no correlations of the D/H ratio for NH2D.Работа выполнена при поддержке РНФ (грант 22-22-00809)

Analisis of kinematics and stability in high-mass star forming regions

Анализ устойчивости молекулярных облаков имеет первостепенное значение в изучении процессов звездообразования. Параметр вириала, который сравнивает массу вириала с фактической массой, обеспечивает один из способов оценить устойчивость к коллапсу. Малые значения параметра наблюдаются для областей образования звезд большой массы, что может свидетельствовать о более быстрой эволюции во время коллапса. В работе используются данные наблюдений в диапазоне 3 мм, полученные с помощью 30-м телескопа IRAM для пяти областей образования массивных звезд (L1287, S187, S231, DR21(OH), NGC7538). Для оценки кинетической температуры использовались отношения интегральных интенсивностей переходов j = 1-0 молекул HCN и HNC и их 13с изотопологов. Для оценки лучевой концентрации N(H2) и массы объектов использовались данные излучения пыли на 850 мкм JCMT-SCUBA. Дисперсия скоростей оценивалась по спектрам H13CO+(1-0). В результате массы облаков составляют ~ 65-5 635 Mq, размер объектов ~ 0.08-0.27 пк, полная дисперсия скоростей H13CO+ ~ 0.25-3.44 км/с. Все источники имеют вириальный параметр avir < 2, что указывает на гравитационную связанность источников и возможность их коллапса (энергия гравитационной связи выше кинетической энергии) при отсутствии дополнительной поддержки, например, со стороны магнитного поля.The analysis of molecular cloud stability is crucial in the study of star formation. One way to estimate the stability to collapse is through the virial parameter, which compares the virial mass with the actual mass. High-mass star forming regions often exhibit small values of the parameter, which may indicate faster evolution during collapse. In this work, we use observational data in the 3 mm wavelength obtained with the IRAM 30 m telescope towards five high-mass star forming regions (L1287, S187, S231, DR21(OH), NGC7538). The integral intensity ratios of transition j = 1-0 of the HCN and HNC molecules and their 13C isotopologues is used to estimate the kinetic temperature. Dust emission data at 850 pm JCMT-SCUBA is used to found the N(H2) column density and source masses. The velocity dispersion is estimated from the H13CO+(lh) spectra. In the results masses are ~ 65- 5 635 Mq, source sizes are ~ 0.08-0.27 pc, total velocity dispersions of H13CO+ ~ 0.25- 3.44 kms-1. Virial parameters of sources are avir < 2, which indicates gravitationally bound of sources and might be collapsing (the gravitational binding energy is higher than the kinetic energy) if no additional support, such as from magnetic field.Работа выполнена при поддержке гранта РНФ 22-22-00809

Deuterated molecules in regions of high-mass star formation

We present the results of our studies of deuterated molecules (DCN, DNC, DCO+, N2D+ and NH2D) in regions of high-mass star formation, which include a survey of such regions with the 20-m Onsala radio telescope and mapping of several objects in various lines with the 30-m IRAM and 100-m MPIfR radio telescopes. The deuteration degree reaches ∼10−2 in these objects. We discuss its dependencies on the gas temperature and velocity dispersion, as well as spatial distributions of deuterated molecules. We show that the H13CN/HN13C intensity ratio may be a good indicator of the gas kinetic temperature and estimate densities of the investigated objects

Deuterium fraction in massive star forming regions

With the IRAM-30m telescope, we observed several massive star forming regions in the lines of the transitions of deuterated molecules DCO+, DCN, DNC in the 2 and 3—4 mm wavelength range. The obtained data allow us to estimate the kinetic temperature of the gas in the sources by the observed lines of molecules CH3CCH. Estimates of the column density in the non-LTE approximation are obtained. As a result, a correlation was found between the relative abundances molecules and the deuterium fractionation degree with temperature.При помощи 30-м радиотелескопа IRAM были проведены наблюдения нескольких областей образования массивных звезд на длинах волн 2 и 3—4 мм, включающие переходы дейтерированных молекул DCN, DCO+, DNC. Полученные данные позволяют оценить кинетическую температуру газа в источниках по наблюдавшимся линиям молекул CH3CCH. Оценены лучевые концентрации молекул в не-ЛТР приближении. В результате были получены корреляции относительного содержания молекул и степени фракционирования дейтерия от температуры