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Off-centered spots of the enhanced gas velocity dispersion, s, are revealed in some galaxies from the MaNGA survey. Aiming to clarify the origin of the spots of enhanced s, we examine the distributions of the surface brightness, the line-of-sight velocity, the oxygen abundance, the gas velocity dispersion, and the BPT spaxel classification in seven galaxies. We find that the enhanced s spots in six galaxies can be attributed to a (minor) interaction with a satellite. Three galaxies in our sample have a very close satellite. The spots of enhanced s in those galaxies are located at the edge of the galaxy close to the satellite. The spots of enhanced s in three other galaxies are related to bright spots in the photometric B band within the galaxy, which can be due to the projection of a satellite in the line of sight of the galaxy. The oxygen abundances in the spots in these three galaxies are reduced. This suggests that the low-metallicity gas from the satellite is mixed with the interstellar medium of the disk. The spectra of the spaxels within a spot are usually HII-region-like, suggesting that the interaction in those galaxies does not result in appreciable shocks. In contrast, the spot of the enhanced s in the galaxy M-8716-12703 is associated with an off-centered AGN-like radiation distribution. One can suggest that the spot of the enhanced s in the M-8716-12703 galaxy is different in origin, or that the characteristics of gas infall in this case differs from that in other galaxies., Comment: 25 pages, 22 figures, accepted to AA

The distribution of the gas velocity dispersion sigma across the images of 1146 MaNGA galaxies is analyzed. We find that there are two types of distribution of the gas velocity dispersion across the images of galaxies: (i) the distributions of 909 galaxies show a radial symmetry with or without the sigma enhancement at the center (R distribution) and (ii) distributions with a band of enhanced sigma along the minor axis in the images of 159 galaxies with or without the sigma enhancement at the center (B distribution) The sigma distribution across the images of 78 galaxies cannot be reliable classified. We select 806 galaxies with the best defined characteristics (this sample includes 687 galaxies with R distribution and 119 galaxies with B distribution) and compare the properties of galaxies with R and B distributions. We find that the median value of the gas velocity dispersion sigma_m in galaxies with B distribution is higher by around 5 km/s, on average, than that of galaxies with R distribution. The optical radius R_25 of galaxies with B distribution is lower by around 0.1 dex, on average, than that of galaxies with similar masses with R distribution. Thus the properties of a galaxy are related to the type of distribution of the gas velocity dispersion across its image. This suggests that the presence of the band of the enhanced gas velocity dispersion can be an indicator of a specific evolution (or a specific stage in the evolution) of a galaxy., Comment: 5 pages, 4 figures, accepted to Astron.Astrophys. arXiv admin note: text overlap with arXiv:2005.12744

We consider the circumnuclear regions of MaNGA galaxies. The spectra are classified as AGN-like, HII-region-like (or SF-like), and intermediate (INT) spectra according to their positions on the BPT diagram. There are the following four configurations of the radiation distributions in the circumnuclear regions: 1) AGN+INT, the innermost region of the AGN-like radiation is surrounded by a ring of radiation of the intermediate type; 2) INT, the central area of radiation of the intermediate type; 3) SF+INT, the inner region of the HII-region-like radiation is surrounded by a ring of radiation of the intermediate type; and 4) SF, the HII-region-like radiation only. The LINERS of configurations 1 and 2 are examined. The spaxel spectra of the LINERs form a sequences on the BPT diagram. The line ratios change smoothly with radius, from AGN-like at the center to HII-region-like at larger distances. This is in agreement with the paradigm that the LINERs are excited by AGN activity. The AGN and INT radiation in the circumnuclear region is accompanied by an enhanced gas velocity dispersion, s_g. The radius of the area of the AGN and INT radiation is similar to the radius of the area with enhanced s_g, and the central s_g,c correlates with the luminosity of the AGN+INT area. We assume that the gas velocity dispersion can serve as an indicator of the AGN activity. The values of s_g,c for the SF-type centers partly overlap with those of the AGN-type centers. We find that there is a demarcation line between the positions of the AGN-type and SF-type objects on the s_g,c - central Halpha surface brightness diagram., Comment: 17 pages, 14 figures, accepted for publication in the A&A

We derive the photometric, kinematic, and abundance characteristics of 18 star-forming MaNGA galaxies with fairly regular velocity fields and surface brightness distributions and with a large offset between the measured position angles of the major kinematic and photometric axes, dPA > 20 degree. The aim is to examine if there is any other distinctive characteristic common to these galaxies. We found morphological signs of interaction in some (in 11 out of 18) but not in all galaxies. The observed velocity fields show a large variety; the maps of the isovelocities vary from an hourglass-like appearance to a set of straight lines. The position angles of the major kinematic axes of the stellar and gas rotations are close to each other. The values of the central oxygen abundance, radial abundance gradient, and star formation rate are distributed within the intervals defined by galaxies with small (no) dPA of similar mass. Thus, we do not find any specific characteristic common to all galaxies with large dPA. Instead, the properties of these galaxies are similar to those of galaxies with small (no) dPA. This suggests that either the reason responsible for the large dPA does not influence other characteristics or the galaxies with large dPA do not share a common origin, they can, instead, originate through different channels., Comment: accepted for publication in Astronomy and Astrophysics

We derive the circular velocity curves of the gaseous and stellar discs of UGC 4056, a giant barred galaxy with an active galactic nucleus (AGN). We analyse UGC 4056 using the 2D spectroscopy obtained within the framework of the Mapping Nearby Galaxies at APO (MaNGA) survey. Using images and the colour index g-r from the Sloan Digital Sky Survey (SDSS), we determined the tilt of the galaxy, which allows us to conclude that the galaxy rotates clockwise with trailing spiral arms. We found that the gas motion at the central part of the UGC 4056 shows peculiar features. The rotation velocity of the gaseous disc shows a bump within around three kiloparsecs while the rotation velocity of the stellar disc falls smoothly to zero with decreasing galactocentric distance. We demonstrate that the peculiar radial velocities in the central part of the galaxy may be caused by the inflow of the gas towards the nucleus of the galaxy. The unusual motion of the gas takes place at the region with the AGN-like radiation and can be explained by the gas response to the bar potential., Comment: 11 pages, 10 figures, 1 table, accepted for publication in A&A

We derive rotation curves, surface brightness profiles, and oxygen abundance distributions for 147 late-type galaxies using the publicly available spectroscopy obtained by the MaNGA survey. Changes of the central oxygen abundance (O/H)_0, the abundance at the optical radius (O/H)_R25, and the abundance gradient with rotation velocity V_rot are examined for galaxies with rotation velocities from 90 km/s to 350 km/s. We found that each relation shows a break at V_rot^* ~200 km/s. The central (O/H)_0 abundance increases with rising V_rot and the slope of the (O/H)_0 - V_rot relation is steeper for galaxies with V_rot < V_rot^*. The mean scatter of the central abundances around this relation is 0.053 dex. The relation between the abundance at the optical radius of a galaxy and its rotation velocity is similar; the mean scatter in abundances around this relation is 0.081 dex. The radial abundance gradient expressed in dex/kpc flattens with the increase of the rotation velocity. The slope of the relation is very low for galaxies with V_rot > V_rot^*. The abundance gradient expressed in dex/R25 is rougly constant for galaxies with V_rot < V_rot^*, flattens towards V_rot^*, and then again is roughly constant for galaxies with V_rot > V_rot^*. The change of the gradient expressed in terms of dex/h_d (where h_d is the disc scale length) with rotation velocity is similar to that for gradient in dex/R25. The relations between abundance characteristics and other basic parameters (stellar mass, luminosity, and radius) are also considered., Comment: Accepted for publication in the Astronomy and Astrophysics

We measured the emission lines in the spaxel spectra of MaNGA galaxies in order to determine the abundance distributions therein. It has been suggested that the strength of the low-ionization lines, R_2, N_2, and S_2 may be increased (relative to Balmer lines) in (some) spaxel spectra of the MaNGA survey due to a contribution of the radiation of the diffuse ionized gas. Consequently, the abundances derived from the spaxel spectra through strong-line methods may suffer from large errors. We examined this expectation by comparing the behaviour of the line intensities and the abundances estimated through different calibrations for slit spectra of HII regions in nearby galaxies, for fibre spectra from the SDSS, and for spaxel spectra of the MaNGA survey. We found that the S_2 strength is increased significantly in the fibre and spaxel spectra. The mean enhancement changes with metallicity and can be as large as a factor of 2. The mean distortion of R_2 and N_2 is less than a factor of 1.3. This suggests that Kaufmann et al.'s demarcation line between AGNs and HII regions in the BPT diagram is a useful criterion to reject spectra with significantly distorted strengths of the N_2 and R_2 lines. We find that the three-dimensional R calibration, which uses the N_2 and R_2 lines, produces reliable abundances in the MaNGA galaxies. The one-dimensional N2 calibration produces either reliable or wrong abundances depending on whether excitation and N/O abundance ratio in the target region (spaxel) are close to or differ from those parameters in the calibrating points located close to the calibration relation. We then determined abundance distributions within the optical radii in the discs of 47 MaNGA galaxies. The optical radii of the galaxies were estimated from the surface brightness profiles constructed based on the MaNGA observations., Comment: 19 pages, 15 figures, accepted for publication in A&A

We examine the relation between breaks in the surface brightness profiles and radial abundance gradients within the optical radius in the discs of 134 spiral galaxies from the CALIFA survey. The distribution of the radial abundance (in logarithmic scale) in each galaxy was fitted by simple and broken linear relations. The surface brightness profile was fitted assuming pure and broken exponents for the disc. We find that the maximum absolute difference between the abundances in a disc given by broken and pure linear relations is less than 0.05 dex in the majority of our galaxies and exceeds the scatter in abundances for 26 out of 134 galaxies considered. The scatter in abundances around the broken linear relation is close (within a few percent) to that around the pure linear relation. The breaks in the surface brightness profiles are more prominent. The scatter around the broken exponent in a number of galaxies is lower by a factor of two or more than that around the pure exponent. The shapes of the abundance gradients and surface brightness profiles within the optical radius in a galaxy may be different. A pure exponential surface brightness profile may be accompanied by a broken abundance gradient and vise versa. There is no correlation between the break radii of the abundance gradients and surface brightness profiles. Thus, a break in the surface brightness profile does not need to be accompanied by a break in the abundance gradient., Comment: 18 pages, 17 figures, accepted for publication in A&A

We examine the influence of the environment on the chemical abundances of late-type galaxies with masses of 10^9.1 M_sun - 10^11 M_sun using data from the Sloan Digital Sky Survey(SDSS). We find that the environmental influence on galactic chemical abundances is strongest for galaxies with masses of 10^9.1 M_sun to 10^9.6 Msun. The galaxies in the densest environments may exceed the average oxygen abundances by about 0.05 dex (the median value of the overabundances for 101 galaxies in the densest environments) and show higher abundances in nitrogen by about 0.1. The abundance excess decreases with increasing galaxy mass and with decreasing environmental density. Since only a small fraction of late-type galaxies is located in high-density environments these galaxies do not have a significant influence on the general X/H - M relation. The metallicity - mass relations for isolated galaxies and for galaxies with neighbors are very similar. The mean shift of non-isolated galaxies around the metallicity - mass relation traced by the isolated galaxies is less than 0.01 dex for oxygen and less than 0.02 dex for nitrogen. The scatter in the galactic chemical abundances is large for any number of neighbor galaxies (at any environmental density), i.e., galaxies with both enhanced and reduced abundances can be found at any environmental density. This suggests that environmental effects do not play a key role in evolution of late-type galaxies as was also concluded in some of the previous studies., Comment: 17 pages, 12 figures, accepted to MNRAS