Navegando por Autor "Zinchenko, Igor"

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    Calibration-based abundances in the interstellar gas of galaxies from slit and IFU spectra
    (EDP Sciences) Pilyugin, Leonid; Lara-López, Maritza A.; Vílchez, Jose M.; Duarte Puertas, Salvador; Zinchenko, Igor; Dors Junior, Oli Luiz
    In this work, we make use of available integral field unit (IFU) spectroscopy and slit spectra of several nearby galaxies. The pre- existing empirical R and S calibrations for abundance determinations are constructed using a sample of H ii regions with high- quality slit spectra. In this paper, we test the applicability of those calibrations to the IFU spectra. We estimate the calibration-based abundances obtained using both the IFU and the slit spectroscopy for eight nearby galaxies. The median values of the slit and IFU spectra-based abundances in bins of 0.1 in fractional radius Rg (normalised to the optical radius R25) of a galaxy are determined and compared. We find that the IFU and the slit spectra-based abundances obtained through the R calibration are close to each other; the mean value of the differences of abundances is 0.005 dex, and the scatter in the differences is 0.037 dex for 38 datapoints. The S calibration can produce systematically underestimated values of the IFU spectra-based abundances at high metallicities (12 + log(O/H) 􏰅8.55); the mean value of the differences is −0.059 dex for 21 datapoints, while at lower metallicities the mean value of the differences is −0.018 dex and the scatter is 0.045 dex for 36 data points. This provides evidence that the R calibration produces more consistent abundance estimations between the slit and the IFU spectra than the S calibration. We find that the same calibration can produce close estimations of the abundances using IFU spectra obtained with different spatial resolution and different spatial samplings. This is in line with the recent finding that the contribution of the diffuse ionised gas to the large-aperture spectra of H ii regions has a secondary effect.
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    Chemical abundance of LINER galaxies – metallicity calibrations based on SDSS-IV MaNGA
    (Royal Astronomical Society) Oliveira Junior, Celso Benedito de; Krabbe, Angela Cristina; Hernandez-Jimenez, Jose Andres; Dors Junior, Oli Luiz; Zinchenko, Igor; Hägele, Guilhermo Frederico; Cardaci, Mónica Viviana; Monteiro, Adriano Francisco
    The ionizing source of low-ionization nuclear emission-line regions (LINERs) is uncertain. Because of this, an empirical relation to determine the chemical abundances of these objects has not been proposed. In this work, for the first time, we derived two semi-empirical calibrations based on photoionization models to estimate the oxygen abundance of LINERS as a function of the N2 and O3N2 emission-line intensity ratios. These relations were calibrated using oxygen abundance estimations obtained by comparing the observational emission-line ratios of 43 LINER galaxies (taken from the MaNGA survey) and grids of photoionization models built with the cloudy code assuming post-asymptotic giant branch stars with different temperatures. We found that the oxygen abundance of LINERs in our sample is in the range, with a mean value of . We recommend the use of the N2 index to estimate the oxygen abundances of LINERs, since the calibration with this index presented a much smaller dispersion than the O3N2 index. In addition, the estimated metallicities are in good agreement with those derived by extrapolating the disc oxygen abundance gradients to the centre of the galaxies showing that the assumptions of the models are suitable for LINERs. We also obtained a calibration between the logarithm of the ionization parameter and the [O iii]/[O ii] emission-line ratio.
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    Chemical abundances of LINER galaxies – nitrogen abundance estimations
    (Royal Astronomical Society) Oliveira Junior, Celso Benedito de ; Krabbe, Angela Cristina; Dors Junior, Oli Luiz; Zinchenko, Igor; Hernandez-Jimenez, José Andrés; Cardaci, Mónica Viviana; Hägele, Guilhermo Frederico; Ilha, Gabriele da Silva
    In this work, we investigated the nitrogen and oxygen abundances in a sample of galaxies with Low Ionization Nuclear Emission Regions (LINERs) in their nucleus. Optical spectroscopic data (3600 – 10 000 Å) of 40 LINERs from the Mapping Nearby Galaxies (MaNGAs) survey were considered. Only objects classified as retired galaxies, that is, whose main ionization sources are post-Asymptotic Giant Branch (pAGB) stars, were selected. The abundance estimates were obtained through detailed photoionization models built with the CLOUDY code to reproduce a set of observational emission line intensities ratios of the sample. Our results show that LINERs have oxygen and nitrogen abundances in the ranges of 8.0 􏰀 12 + log(O/H) 􏰀 9.0 (mean value 8.74 ± 0.27) and 7.6 􏰀 12 + log(N/H) 􏰀 8.5 (mean value 8.05 ± 0.25), respectively. About 70 per cent of the sample have oversolar O/H and N/H abundances. Our abundance estimates are in consonance with those for Seyfert 2 nuclei and H II regions with the highest metallicity, indicating that these distinct object classes show similar enrichment of the interstellar medium (ISM). The LINERs in our sample are located in the higher N/O region of the N/O versus O/H diagram, showing an unexpected negative correlation between these two parameters. These results suggest that these LINERs mainly exhibit a secondary nitrogen production and could be acting some other mechanisms that deviate them from the usual theoretical secondary nitrogen production curve and the H II regions observations. However, we did not find any evidence in our data able to support the literature suggested mechanisms. Alternatively, our results show that LINERs do not present any correlation between the N/O abundances and the stellar masses of the hosting galaxies.