NGC 5506: Kinematics and Physics of the Extended NLR (Poster paper)

Summary

The galaxy NGC 5506 shows features intermediate between Sy 1 and Sy 2. We observed NGC 5506 with ISIS, at the 4.2m William Herschel Telescope. We obtained spectra at three slit inclinations (0° P.A., parallel to the disk minor axis, 68° and 93° P.A.), in the spectral ranges 4,675–5,475Å and 6,300–7,125Å. The relative proximity of this galaxy (z=0.006) allowed us to resolve the Narrow Line Region along the slit.

The Hα, [NII]6,584 and [0 III]5,007 lines show double peaks at distances larger than 300 pc from the center along 0° P.A. The velocity shift vs. position of the two peaks is plotted in Figure 1. We fitted the velocity curve of these peaks with a model similar to that by Wilson, Baldwin, and Ulvestad (1985) where the double peaked lines are emitted by gas flowing through two aligned and opposite cones; we obtain a flow velocity of 400 km s^-1, a cone aperture angle of 80° and an inclination angle of the cone axis with respect to the perpendicular to the line of sight of 13°, very close to galaxy inclination.

The relative intensity of the Hα double peaks and their [NII]/Hα ratio (Fig. 2) can be well explained assuming that the emitting clouds within the cones are outflowing and optically thick to Hα, so that the redshifted clouds (NR and SR), presenting us the illuminated side, show line ratios typical of the high ionization region, while the blueshifted clouds (NB and SB), presenting us the dark side, show line ratios typical of the transition (partially ionized) zone.