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Up: Mixed early and late-type sequence?

1 Introduction

NGC 6221 is a nearby spiral classified as Sbc(s) by Sandage & Tammann (1981) and as SBc(s) by de Vaucouleurs et al. (1991). In The Carnegie Atlas of Galaxies (Panel 189) Sandage & Bedke (1994) describe its morphology as semichaotic with two symmetric heavy dust lanes starting from the nucleus and threading through the middle of the opposite thick arms, which begin at the centre. They also stated that although the galaxy is not strongly barred its dust pattern is similar to that of prototype SBb galaxies, characterized by two straight dust lanes. An overview of the optical properties of the galaxy is given in Table 1.

NGC 6221 forms an apparent physical pair with the late-type spiral NGC 6215. They have a systemic velocity of $1465\pm 10$ $\rm km\;s^{-1}$ (this paper) and $1521\pm $ 43 $\rm km\;s^{-1}$ (RC3) respectively. Their angular distance is about 26' (RC3) corresponding to a projected linear separation of about 227 kpc at a mean distance of 30 Mpc ($H_0 = 50\;\rm km\;s^{-1}\;Mpc^{-1}$). The galaxy is also possibly interacting with two newly discovered low-surface brightness galaxies nearby (Koribalski 1996a).

The dynamics of the ionized gas component in this galaxy has been studied by Pence & Blackman in 1984 (hereafter P&B). They measured a conspicuous S-shaped pattern in the ionized gas velocity field, showing that large velocity gradients occur at the position of the dust lanes in the bar. They have been interpreted as the signature of shock fronts of the gas which reverses its motion from outward to inward as it passes through them.

Philipps (1979) reported that the nuclear spectrum of NGC 6221 exhibits signatures of emission originating from $\rm H \;{\scriptsize II}$ regions and also a weak Seyfert 2 component. He concluded however that the emission line spectrum can be interpreted as gas being ionized by hot young stars without the need to introduce a non-thermal component in the galaxy nucleus. The analysis of the spatial distribution of the ionized gas (Durret & Bergeron 1987) confirmed this picture. Some dozens of $\rm H \;{\scriptsize II}$ regions were identified in the disk region extending as far as 9 kpc from the galaxy nucleus. Although the emission in the nucleus appears to be extended ($\sim\! 1 \; {\rm kpc}^2$), the authors conclude that the main ionizing sources are OB stars and that UV and X-ray radiation from the nuclear source might not penetrate the heavily obscured nuclear region. Dottori et al. (1996) also recently suggested that the nucleus of NGC 6221 may harbour sources of type $\rm H \;{\scriptsize II}$ and also a Seyfert 2 source.

Table 1: Optical properties of NGC 6221

parameter & value \\ \noalign{...
 ...^{\rm b}$\space & $10.66$\space mag \\ \noalign{\smallskip} 

In this paper we study the kinematics of the ionized gas and the stellar components in NGC 6221. We present the velocity curves and the velocity dispersion profiles of gas and stars obtained along five different position angles by means of long-slit spectroscopy.

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