2. Observations and data reduction
The spectroscopic observations of UGC 10205 were carried out on March 19-21, 1996 at the Isaac Newton Telescope (INT) in La Palma using the Intermediate Dispersion Spectrograph (IDS).
The H1800V grating with 1800 grooves was used in the first order in combination with a slit, the 500 mm camera and the AgRed collimator. It yielded a wavelength coverage of Å between 6650 Å and 6890 Å with a reciprocal dispersion of 9.92 . We checked that the measured FWHMs do not depend on wavelength and we found a mean value of FWHM = 0.86 Å (i.e. Å) that, in the range of the observed gas emission lines, corresponds to . No on-chip binning was done on the adopted 1024 1024 TK1024A CCD. Each 24 µm 24 µm image pixel corresponds to 0.24 Å .
We took two separate major axis spectra (P.A. = ) for a total exposure time of 100 minutes (Fig. 1). The slit was centered visually on the galaxy nucleus. A comparison copper-argon lamp exposure was obtained between the two object integrations. All the images were reduced using standard MIDAS routines. Considering a sample of 8 bright OH night-sky emission lines, we found a mean deviation from the theorical predicted wavelength (Osterbrock & Martel, 1992) corresponding to .
The gas velocities and velocity dispersions for , where the ionized gas emission lines have a Gaussian profile shape, were derived by means of the MIDAS package ALICE. We measured the H and the [N II] ( Å) lines, where they were clearly detected. The position, the FWHM and the uncalibrated flux of each emission line were individually determined by interactively fitting one Gaussian plus a polynomial to each emission and to its surrounding continuum. The wavelength of the Gaussian center was converted to the velocity , and then an heliocentric correction of was applied. The Gaussian FWHM was corrected for the instrumental FWHM and then converted to the velocity dispersion . The ionized gas emission lines are double-peaked for and even triple-peaked for . They have been fitted using the above package with two or three Gaussians respectively and a polynomial continuum. At each radius this multiple-Gaussian fit has been done separately for each emission line.
The gas velocity curves and the velocity dispersion profiles independently derived from the H (Fig. 2) and the [N II] (Fig. 3) lines are in good agreement at all radii. The kinematical data from H and [N II] lines are given in Table 1 and in Table 2 respectively. Each table provides the radial distance from the galaxy center r in arcsec (col. 1), the observed heliocentric velocity v (col. 2) and the velocity dispersion (col. 3) in , the number n of spectrum rows binned along the spatial direction to improve the signal-to-noise ratio of the emission lines (col. 4) and the identification i of the kinematically distinct gas components (col. 5).
Table 1. UGC 10205 major axis H kinematics
Table 2. UGC 10205 major axis [N II] kinematics
© European Southern Observatory (ESO) 1997
Online publication: May 26, 1998