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Astron. Astrophys. 317, 36-42 (1997)

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1. Introduction

NGC 1300 is often referred to as the prototype SBb(s) system (Sandage 1961). Its distance has been estimated to 17.1 Mpc (de Vaucouleurs & Peters 1981), which we adopt in this paper. The classification is SB(rs)bc, given in the Second Reference Catalog of Bright Galaxies (de Vaucouleurs et al. 1976) or SBb I, as classified by van den Bergh (1976).

NGC 1300 features a strong bar with prominent straight dust lanes and ensembles of H II regions at the end points of the bar, common characteristics of many late type barred spirals. The dust lanes are displaced towards the leading edge of the bar (assuming trailing spiral arms), extending from the nucleus to the end of the bar, then turning almost [FORMULA] to trace the spiral arms. Across the bar there is a complex pattern of weaker dust lanes. Bright star forming regions outline the optical arms. Some general information concerning NGC 1300 is listed in Table 1.

An investigation of the optical velocity field of NGC 1300 is presented by Peterson & Huntley (1980, hereafter PH), using 13 slit observations covering the nuclear and inner arm regions. However, the bar region kinematics are severely undersampled due to a lack of ionized gas.

In the previous analysis of the H I data used here, England (1989), fitting data in a restricted angular interval (a wedge), finds the position angle of the line of nodes to be [FORMULA] and the inclination angle [FORMULA], while a preliminary analysis by Jörsäter & van Moorsel (1995, hereafter JvM) finds the inclination to be [FORMULA].

In the present investigation we analyze the velocity field of NGC 1300 using both H I and optical slit velocity data. From the H I analysis we deduce the orientation parameters of the system and the corresponding rotation curve. Furthermore, we join the H I and optical velocity data to form a combined velocity field using techniques described in Lindblad P.O. et al. (1996). The results presented here were used in the hydrodynamical modeling of NGC 1300 presented by Lindblad & Kristen (1996).

The images presented here are oriented so to have North up and East to the left. The units on the axes are arcseconds offset from the optical nucleus, if nothing else is stated.

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© European Southern Observatory (ESO) 1997