Gas and stellar kinematic misalignment in MaNGA galaxies: what is the origin of counter-rotating gas?

Kinematic misalignment between gas and stellar components observed in a certain fraction of galaxies. It believed to be caused by acquisition of gas from the external reservoir by major or minor mergers, accretion from cosmological filaments or circumgalactic medium, etc. We aim to constrain possible sources of the gas that forms counter-rotating component. We derived the gas-phase oxygen abundance in 69 galaxies with kinematic misalignment between gas and stellar components from MaNGA DR17 survey and compared it with the metallicity expected according to the mass-metallicity relation. We found that the oxygen abundance of the counter-rotating gas in our sample is higher than 8.2 dex that excludes significant role of inflow of pristine gas. Meanwhile, there is a significant difference in the oxygen abundance of the counter-rotating gas between red and blue galaxies. In general, the oxygen abundance is lower than expected for their stellar mass in red galaxies, but is compatible with or even higher than typical values for their stellar mass in blue galaxies. We showed that the exchange of enriched gas between galaxies is the most plausible mechanism for explaining the metallicity of counter-rotating gas components in galaxies of all masses and colors. Meanwhile, minor mergers may play a significant role in the formation of counter-rotating gas components in red and quenched galaxies.Comment: 5 pages, 3 figures, accepted for publication in A&A Letter

Millimeter and submillimeter wave astronomy today and tomorrow

В данном обзоре обсуждаются недавние достижения и актуальные задачи миллиметровой и субмиллиметровой астрономии. Приводятся сведения о действующих, строящихся и проектируемых инструментах этого диапазона, как наземных, так и космических.In this review, recent achievements and actual problems of millimeter and submillimeter astronomy are discussed. The article provides information on existing, under construction and projected instruments of this band, both ground-based and space ones.Работа выполнена при поддержке Российского фонда научных исследований (проект 17-12-01256, раздел «Основные задачи миллиметровой и субмиллиметровой астрономии») и Российского фонда фундаментальных исследований (грант 15-02-06098, раздел «Существующие и перспективные инструменты»)

A Search for Small-Scale Clumpiness in Dense Cores of Molecular Clouds

We have analyzed HCN(1-0) and CS(2-1) line profiles obtained with high signal-to-noise ratios toward distinct positions in three selected objects in order to search for small-scale structure in molecular cloud cores associated with regions of high-mass star formation. In some cases, ripples were detected in the line profiles, which could be due to the presence of a large number of unresolved small clumps in the telescope beam. The number of clumps for regions with linear scales of ~0.2-0.5 pc is determined using an analytical model and detailed calculations for a clumpy cloud model; this number varies in the range: ~2 10^4-3 10^5, depending on the source. The clump densities range from ~3 10^5-10^6 cm^{-3}, and the sizes and volume filling factors of the clumps are ~(1-3) 10^{-3} pc and ~0.03-0.12. The clumps are surrounded by inter-clump gas with densities not lower than ~(2-7) 10^4 cm^{-3}. The internal thermal energy of the gas in the model clumps is much higher than their gravitational energy. Their mean lifetimes can depend on the inter-clump collisional rates, and vary in the range ~10^4-10^5 yr. These structures are probably connected with density fluctuations due to turbulence in high-mass star-forming regions.Comment: 23 pages including 4 figures and 4 table

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