Nazgul Sh. Alimgazinova

The study of young stellar objects is one of the priority areas in modern astrophysics, since these objects serve as key indicators of the processes accompanying the formation of stars and planetary systems. In the process of evolution, especially in the conditions of massive star clusters, they generate intense ultraviolet radiation and stellar winds that are capable to scatter the surrounding matter and forming expanding cavities that are infrared bubble structures in molecular clouds. The study of these structures allows us to obtain valuable information about the mechanisms of interaction of stars with their surrounding environment at various stages of evolutionary development. The aim of this work is to study the region of the dust bubble N22 in order to identify and classify young stellar objects. The main observational material was data obtained by the Wide-Field Infrared Survey Explorer space telescope in the near and mid-infrared range: W1 (3.4 μm), W2 (4.6 μm), W3 (12 μm), and W4 (22 μm). As a result of the analysis, new candidates for young stellar objects were identified within the studied region: 15 objects belonging to class I, 7 objects - class II, and 13 objects demonstrating the characteristics of transition disks. For all selected candidates for young stellar objects, color diagrams were constructed displaying their position relative to the characteristic regions of the evolutionary stages of young stars. In addition, spectral indices were calculated and the energy distribution in the spectrum was modeled, which confirmed the classification of objects by evolutionary stages.

We present the results of a search and identification of young stellar objects (YSOs) in the Serpens South star-forming region, which is part of the Aquila Rift complex. Using AllWISE catalog data within a radius of 7′ from the center of the region, a multi-stage filtering procedure was applied to remove contaminating sources, including galaxies, active galactic nuclei, shock emission sources and PAH emission. Photometric criteria were then used to classify the sources according to their evolutionary stages. As a result, a sample of 145 YSO candidates was identified, including 1 protostar, 37 Class I objects, 48 Class II objects, 47 Class III objects and 12 transition disks. A quantitative analysis of the spatial distribution of the sources was performed using cumulative distribution functions, the Kolmogorov Smirnov test and bootstrap resampling. The results show that early-stage objects (Class I) exhibit pronounced clustering in the central region (R₅₀ = 0.26 pc) and are associated with dense filamentary structures, whereas Class II and III objects display a more extended distribution. A Jeans analysis combined with Monte Carlo simulations yielded a median gas density of n ≈ 1.6 × 105 cm-3, consistent with dense prestellar cores. Multiwavelength verification using infrared, X-ray, optical and radio catalogs showed that 78.6% of the objects possess independent infrared confirmation, while 70.3% have X-ray detections. In addition, 11 new YSO candidates not previously reported in published catalogs were identified. The obtained results demonstrate the high efficiency of WISE data for detecting heavily obscured sources and provide new insights into the early stages of star formation in dense filamentary environments. Keywords: Young stellar objects, Serpens South, Aquila Rift, WISE, star formation.

Observations of the massive star-forming region G335.79+0.17 reveal dense, hot molecular gas toward two cores, P1 and P2, traced by methyl cyanide, its isotopologue, methyl acetylene, formaldehyde and dust continuum emission. Only these two hot cores are detected, highlighting a chemically rich environment typical of early massive star formation. Velocity gradients in opposite directions provide strong evidence of molecular gas rotation. Rotational diagram analysis shows that core P1 is hotter than P2, with methyl cyanide and its isotopologue tracing gas near the protostar, while methyl acetylene traces cooler outer layers.

We present high–angular resolution 1.3 mm continuum and molecular line observations toward the highmass star-forming region G350.29+0.12, using CH₃CN and CH₃¹³CN rotational transitions. The continuum emission resolves two main cores: a bright, compact northern core G350.29+0.12 A and a weaker southern core G350.29+0.12 B. Core A exhibits six compact substructures embedded within more extended emission. M K-components of the CH3CN J = 14→13 and CH3 13CN J = 14→13 transitions are detected, with the emission arising primarily from core A. The CH3CN moment 0 maps show that the integrated intensities peak at the main continuum position, indicating that the molecular emission traces warm and dense gas. The moment 1 maps reveal a pronounced velocity gradient of ∼2 km s-1 across core A, oriented from northwest to southeast, while the moment 2 maps show K-dependent variations in velocity dispersion. Position–velocity diagrams further indicate organized rotational motions, exhibiting a compact velocity structure with a central peak and systematic gradients. Rotational temperature analysis yields = 360.6 ± 34.8 K for CH3CN, tracing the hottest and densest gas and Trot = 138 ± 45 K for CH3 13CN, consistent with cooler and more extended material. Together, these results demonstrate that G350.29+0.12 A is a rotating hot molecular core undergoing active high-mass star formation.

The study of the mechanisms of star formation and evolution is based on comprehensive research into interstellar regions, including the analysis and identification of young stellar objects (YSOs). The identification of young stellar objects by their radiation at various wavelengths in the infrared range is a relatively recent development - the first studies in this field appeared only at the end of the 20th century. The development of this field has been made possible by improvements in observation techniques and data processing methods, the acquisition of more reliable characteristics of stellar sources, and the creation of catalogs containing extensive arrays of information about cosmic objects. In this study, the star-forming region W40 of the Aquilla molecular cloud was investigated in the infrared wavelength range to detect previously unidentified young stellar objects at various stages of evolution. Identification was carried out using two approaches: photometric criteria and spectral indices. This made it possible to more reliably identify the evolutionary stages of 37 newly discovered and previously unexplored YSO candidates (5 objects of class I, 2 objects of class II, 4 objects – class “transitional disks” and 26 objects — class III), which indicates an active and ongoing process of star formation in W40.

Objects with the B[e] phenomenon, whose defining features are the presence of forbidden emission lines and infrared excess coming from circumstellar dust, represent a broad range of evolutionary stages from pre-main-sequence to planetary nebulae. They are important for understanding mechanisms of the circumstellar matter formation and evolution. However, it is not easy to discover them, especially among faint stars, as forbidden emission lines are usually weak and hardly noticeable in low-resolution spectra. We developed photometric criteria to search for candidate objects with this phenomenon based on a combination of optical and near-infrared color indices and found nearly 40 objects that satisfy these criteria. Spectroscopy of the candidates allows us to make more confident conclusions on their classification. We present the results of our photometric and spectroscopic observations of six objects, which are part of a large list of ∼40 objects that satisfy our photometric selection criteria for candidate objects with the B[e] phenomenon. Forbidden lines of neutral oxygen were clearly detected in the optical spectrum of one object (VES 683) and suspected in three others. One object, AS 415, is most likely a binary system with components that exhibit partial eclipses but without the B[e] phenomenon, while IRAS 20402 + 4638 may be a luminous member of the FS CMa objects group.

The study of young stellar objects is one of the key studies in astrophysics, as these objects provide a unique window into the processes that occur during the formation of stars and planets. Young stars are often found in clouds of gas and dust, which serve as a kind of "cradle" for their birth. Young stars, especially in massive star clusters, create powerful streams of wind and radiation that knock out dust and gas, creating ring structures, those as bubbles in molecular clouds. Analysis of such structures can provide additional clues about the strength of the interactions between stars and their environment at different stages of their evolution. The main objective of this study was to study the N1 dust bubble region and search for and identify young stellar objects. Searching for young stellar objects (YSOs) using infrared data from astronomical catalogs is an important and effective method for studying star formation. Young stars and their surroundings are often hidden from visible-light observations by dense clouds of gas and dust, but infrared radiation can penetrate these clouds, allowing astronomers to find objects that would otherwise be invisible. The identification of young stellar objects in this study was performed according to the algorithm of Koenig & Leisawitz (2014). The observational data of the WISE spacecraft in the near and mid-infrared bands W1 (3.4 μm), W2 (4.6 μm), W3 (12 μm) and W4 (22 μm) were used. Reliable non-zero fluxes of infrared radiation sources from the 2MASS and AllWISE catalogs were selected for the study. For the studied dust bubble, 7 objects of class I and 11 objects of class II were identified, 32 objects were assigned to the transition disk stage. For all identified young stellar objects, color diagrams were constructed showing the locations of the found objects with the corresponding evolutionary regions. Spectral indexes were calculated and energy distributions in the spectra were constructed for young stellar objects, which also confirmed their evolutionary status. The distribution maps of early-stage YSOs within the dust bubble are analyzed, which indicate the patterns of their distribution along filamentary structures in the dust bubble N1.

The relationships between the relative abundances of chemical elements and their second ionization potentials, as well as their condensation temperatures, were analyzed using four published homogeneous abundance surveys of halo and thin disk stars. We selected 932 stars with effective temperatures ranging from 4900 K to 5900 K and used the abundances of 10 chemical elements common across all surveys: Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, and Ni. The correlation coefficients between the relative abundances of these elements and their second ionization potentials and condensation temperatures were investigated in relation to metallicity and the stars' location in the Galaxy. The observed correlations may result from certain physical processes, such as the accretion of interstellar gas onto stellar atmospheres. We also analyzed the dependencies of relative abundances on second ionization potentials based on published abundance patterns in five halo stars. Evidence of charge-exchange reactions in the atmospheres of these stars was found. For more accurate determination of stellar ages from the abundance ratios of radioactive and stable chemical elements in stellar atmospheres, processes such as charge-exchange reactions and dust-gas separation should be considered in future detailed investigations. Additionally, changes in the chemical abundances in the atmospheres of halo stars after crossing the Galactic plane were found to be possible.