Ionized gas and stars in the central kiloparsec of the type 2 Seyfert galaxy NGC 2110 - I. The data

In this paper, we present new results from an extensive set of Hubble Space Telescope (HST) and ground-based observations of the Seyfert galaxy NGC 2110. The HST data sets include Wide Field Planetary Camera 2 (WFPC2) observations as well as the first high-spatial resolution spectroscopy ([OI], [NII], Hα and [SII] lines) of this galaxy obtained using the Space Telescope Imaging Spectrograph (STIS). The ground-based data are three-dimensional (x, y, λ) spectrographic observations obtained using the integral field spectrograph OASIS on the Canada-France-Hawaii Telescope, complemented by near-infrared long-slit spectroscopy obtained using NIRSPEC on the Keck-II telescope. The OASIS observations cover regions containing both stellar absorption lines and major optical emission lines. The NIRSPEC observations cover the H and K bands. Combined with archival HST observations, the WFPC2 data provide us with a high-spatial resolution extinction map. The OASIS data allowed bidimensional mapping of the stellar and gaseous kinematics, as well as of the spectral properties of the ionized gas. These results are compared to those obtained in the near-infrared with NIRSPEC/Keck. Last, we used the STIS data to probe the ionized gas kinematics and properties in the inner 4 arcsec along PA = 156° at unprecedented spatial resolution. Our two-dimensional (2D) map of the stellar velocity field and the near-infrared stellar velocity profile are symmetric about the nucleus, confirming the results of previous long-slit observations. The asymmetry of the velocity field of the ionized gas is present at the same level for visible and near-infrared lines, indicating this is not a reddening effect. Multiple Gaussian fitting of the emission-line profile allowed the contributions of the broad and a narrow components to be disentangled. The intensity peak of the [O III] narrow component is located north of the nucleus, indicating that the bulk of the narrow [O III] emission comes from the jet-like structure (Mulchaey et al.) and not from the nucleus itself. We suggest that the northern arm is the anomalous one, contrary to what has been claimed earlier. Last, we also show that the elongated region of high gas velocity dispersion located close to the nucleus and discovered by GonzÀlez Delgado et al. is intrinsic to the narrow component.