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Keywords:

  • methods: data analysis;
  • methods: observational;
  • techniques: spectroscopic;
  • galaxies: fundamental parameters;
  • galaxies: peculiar

ABSTRACT

We present the first optical long-slit spectroscopy for the galaxy HRG 10103, an Sa(r)-type peculiar galaxy seen face-on with an asymmetrical elliptical structure. The main goal of this work is to provide the spectral classification of the current object using ‘standard’ diagnostic diagrams. We also include empirical boundaries and a recent analysis involving the known emission-line ratio R23, usually used to estimate the O/H abundance ratio. The idea is to make a better distinction between the narrow-line AGNs [i.e. the Seyfert 2 galaxies and the low-ionization nuclear emission-line regions (LINERs)] and the H ii galaxies (i.e. the Starburst galaxies). The spectra were obtained in two observatories (OPD-LNA/MCT and Gemini-South) and includes some of the most important emission lines for ionization diagnostic. Based on the observed spectra, HRG 10103 is a Seyfert 2 galaxy with typical line-ratio values in the optical range. We have estimated nuclear redshift of z= 0.040, corresponding to a heliocentric velocity of ∼11 800 km s−1. The resulting reddening-corrected fluxes as a function of distance from the nucleus are presented too. The errors in the fluxes were mostly caused by uncertainties in the placement of the continuum level. To map the gas kinematics, we averaged the central wavelengths of Gaussians which we had fitted to the most prominent emission lines observed in each spectrum. For each position angle on the sky, it was observed that the velocity fields of the ionized gas are smooth and similar at an orientation not far from the major axis [position angle (PA) = 0° and 9° (OPD-LNA/MCT), and PA = 6° (Gemini-South)]. Some other physical and geometrical parameters were derived whenever possible. The spectroscopic data reduction was carried out using the gemini.gmos package as well as the standard iraf procedures.