Ionized Gas in the NGC 3077 Galaxy

Abstract—The nearby dwarf galaxy NGC 3077 is known for its peculiar morphology, which includes numerous dust lanes and emission-line regions. The interstellar medium in this galaxy is subject to several perturbing factors. These are primarily the central starburst and tidal structures in the M81 group. We present a comprehensive study of the state of ionization, kinematics, and chemical composition of ionized gas in NGC 3077, including both star-forming regions and diffuse ionized gas (DIG) at the periphery. We study gas motions in the Hα line via high-resolution (R ≈ 15 000) 3D spectroscopy with the scanning Fabry–Perot interferometer installed into SCORPIO-2 instrument attached to the 6-m telescope of the Special Astrophysical Observatory of the Russian academy of Science. Images in the main optical emission lines were acquired with MaNGaL photometer with a tunable filter at the 2.5-m telescope of the Caucasian Mountain Observatory of Sternberg Astronomical Institute of Lomonosov Moscow State University. We also used SCORPIO-2 to perform long-slit spectroscopy of the galaxy with a resolution of R ≈1000. Our estimate of the gas metallicity, Z = 0.6Z⊙, is significantly lower than the earlier determination, but agrees with the “luminosity–metallicity” dependence. Spatially resolved diagnostic diagrams of the emission-line ratios do not show correlations between the gas ionization state and its velocity dispersion, and this is most likely due to strong ionization by young stars, whereas the contribution of shocks to the excitation of emission lines is less important. We also studied the locations of multicomponent Hα profiles and provide arguments suggesting that they are mostly associated with individual kinematic components along the line of sight and not with expanding shells as it was believed earlier. We also observe there a combination of wind outflow from star-forming regions and accretion from interstellar gas clouds in the M81 group.