2 Sample selection, observations and data reduction

All the observed galaxies are bright ( $B_{\rm T}\leq13.5$) and nearby objects ( $V_\odot < 5800$ $\rm km\;s^{-1}$) with an intermediate-to-high inclination ( $45^\circ\leq i \leq 80^\circ$) and their Hubble morphological type ranges from S0 to Sc. An overview of their basic properties is given in Table 1. Figure 1 shows the absolute magnitude distribution for the galaxies of our sample. It nicely brackets the $M^\ast$ value for spiral galaxies taken from Marzke et al. (1998) assuming H₀ = 75  $\rm km\;s^{-1}$ Mpc^-1.

Figure 1: Absolute magnitude distribution for the sample galaxies. A line marks $M_{B_{\rm T}}^0 = -20.05$, which corresponds to $M^\ast$ for spiral galaxies as derived by Marzke et al. (1998) and assuming H0 = 75 $\rm km\;s^{-1}$ Mpc-1.

   
2.1 Spectroscopic observations

The long-slit spectroscopic observations of our sample galaxies were carried out at the 4.5-m Multi Mirror Telescope (MMT) in Arizona (USA), at the ESO 1.52-m Spectroscopic Telescope at La Silla (Chile), and at the 2.5-m Isaac Newton Telescope (INT) on La Palma (Spain). The instrumental setup of each observing run is summarized in Table 2.

   

Table 2: Instrumental setup of spectroscopic observations.

Parameter	MMT		ESO 1.52-m	INT
Date	21-23 Oct. 1990	17-18 Dec. 90	30 Apr. - 02 May 1992	20-21 Mar. 1996
Spectrograph	Red Channel		B&C	IDS
Grating ( $\rm grooves\;mm^{-1}$)	1200		1200 (ESO No. 26)	1800
Detector	Loral 12$\times$8mmt		FA2048L (ESO No. 24)	TK1024A
Pixel size ( $\rm\mu m^{2}$)	$15\times15$		$15\times15$	$24\times24$
Pixel binning	$1\times1$		$1\times1$	$1\times1$
Scale ( $\rm ''\;pixel^{-1}$)	0.30		0.81	0.33
Reciprocal dispersion ( $\rm\AA\;pixel^{-1}$)	0.82		0.98	0.24
Slit width ('')	1.25		2.1	1.9
Slit length (')	3.0		4.2	4.0
Spectral range (Å)	4850-5500		4900-6900	6650-6890
Comparison lamp	He-Ne-Ar-Fe		He-Ar	Cu-Ar
Instrumental FWHM (Å)	$2.24\pm0.26$	$2.57\pm0.11$	$2.34\pm0.09$	$0.869\pm0.040$
Instrumental $\sigma$ ( $\rm km\;s^{-1}$)	57	65	45	17
Seeing FWHM ('')	1.2-1.5		1.0-1.5	1.0-1.8

Notes - The instrumental $\sigma$ was measured at [O  III] $\,\lambda5006.8$ for the MMT spectra and at H$\alpha$ for the ESO 1.52-m and INT spectra.

At the beginning of each exposure, the slit was centred on the galaxy nucleus using the guiding TV camera and aligned along the galaxy major axis. The details of the slit position and spectra exposure times are given in Table 3. In all the observing runs comparison lamp exposures were obtained before and after each object integration to allow an accurate wavelength calibration. Quartz-lamp and twilight-sky flat fields were used to map pixel-to-pixel sensitivity variations and large-scale illumination patterns. At the MMT and ESO 1.52-m telescopes a number of late-G and early-K stars were observed with the same set up to serve as templates in measuring the stellar kinematics (see Table 4). The seeing range during the different spectroscopic runs is given in Table 2.

 

 

Table 3: Log of spectroscopic observations of the galaxies.

Object	Date	Telescope	$t_{\rm exp}$	PA
			[s]	[$^\circ$]
NGC 224	18 Dec. 90	MMT	2$\times$3600	55
NGC 470	22 Oct. 90	MMT	3600	155
NGC 772	22 Oct. 90	MMT	3600	130
NGC 949	21 Oct. 90	MMT	3600	145
NGC 980	22 Oct. 90	MMT	3600	110
NGC 1160	21 Oct. 90	MMT	3600	50
NGC 2541	21 Oct. 90	MMT	3600	165
NGC 2683	18 Dec. 90	MMT	3600	44
NGC 2841	22 Oct. 90	MMT	3600	147
NGC 3031	17 Dec. 90	MMT	3600	157
NGC 3200	02 May 92	ESO 1.52-m	3600	79
NGC 3368	17 Dec. 90	MMT	3600	5
NGC 3705	17 Dec. 90	MMT	3600	122
NGC 3810	18 Dec. 90	MMT	3600	15
NGC 3898	18 Dec. 90	MMT	3600	107
	19 Mar. 96	INT	3$\times$3600	107
NGC 4419	20 Mar. 96	INT	2$\times$3300	133
	02 May 92	ESO 1.52-m	3600	133
NGC 5064	30 Apr. 92	ESO 1.52-m	3600	138
NGC 5854	30 Apr. 92	ESO 1.52-m	3600	145
	30 Apr. 92	ESO 1.52-m	3600	25
	30 Apr. 92	ESO 1.52-m	3600	55
NGC 7331	22 Oct. 90	MMT	3600	171
NGC 7782	22 Oct. 90	MMT	3600	30

   

Table 4: Log of spectroscopic observations of the template stars.

Object	Date	Telescope	$t_{\rm exp}$	Type
			[s]	[BSC]
HR 2649	21 Oct. 90	MMT	180	K3III
HR 7778	23 Oct. 90	MMT	200	G8III
HR 7854	23 Oct. 90	MMT	200	K0III
HR 941	18 Dec. 90	MMT	99	K0III
HR 3360	17 Dec. 90	MMT	195	K2III
HR 3905	17 Dec. 90	MMT	126	K2III
HR 4246	18 Dec. 90	MMT	100	K3III
HR 4924	17 Dec. 90	MMT	139	G9III
HR 8694	18 Dec. 90	MMT	89	K0III
HR 3431	30 Apr. 92	ESO 1.52-m	5$\times$20	K4III
HR 5601	30 Apr. 92	ESO 1.52-m	5$\times$15	K0.5III
HR 6318	30 Apr. 92	ESO 1.52-m	5$\times$20	K4III
HR 7595	30 Apr. 92	ESO 1.52-m	5$\times$20	K0III

Note - The spectral class of the template star is taken from
The Bright Star Catalogue (Hoffleit & Jaschek 1982).

   
2.2 Routine data reduction

The spectra were bias subtracted, flat-field corrected, cleaned for cosmic rays and wavelength calibrated using standard MIDAS routines. Cosmic rays were identified by comparing the counts in each pixel with the local mean and standard deviation (as obtained from the Poisson statistics of the photons knowing the gain and readout noise of the detector), and then corrected by interpolating a suitable value.

The instrumental resolution was derived as the mean of the Gaussian FWHM's measured for a dozen unblended arc-lamp lines distributed over the whole spectral range of a wavelength-calibrated comparison spectrum. The mean FWHM of the arc-lamp lines as well as the corresponding instrumental velocity dispersion are given in Table 2. Finally, the individual spectra of the same object were aligned and coadded using their stellar-continuum centres as reference. For each spectrum the centre of the galaxy was defined by the centre of a Gaussian fit to the radial profile of the stellar continuum. The contribution of the sky was determined from the edges of the resulting spectrum and then subtracted.

   
2.3 Measuring stellar and ionized gas kinematics

The stellar kinematic parameters were measured from the absorption lines present on each spectrum using the Fourier Correlation Quotient Method (Bender 1990) as applied by Bender et al. (1994). The spectra of the stars G8III HR 7778, K2III HR 6415 and K4III HR 6318 provided the best match to the galaxy spectra obtained in October 1990, December 1990 and May 1992, respectively. They were used as templates to measure the stellar kinematic parameters of the sample galaxies in the three runs. For each spectrum we measured the radial profiles of the heliocentric stellar velocity ($v_\star$), velocity dispersion (σ_*), and the Gauss-Hermite coefficients h₃ and h₄, in the case of sufficiently high S/N. The stellar kinematics of all the sample galaxies are tabulated in Table 5. The table provides the galaxy name, the position angle of the slit in degrees, the radial distance from the galaxy centre in arcsec, the observed heliocentric velocity and the velocity dispersion in  $\rm km\;s^{-1}$, and the Gauss-Hermite coefficients h₃ and h₄.

The ionized gas kinematic parameters were derived by measuring the position and the width of [O  III] $\,\lambda5006.8$ emission line in the MMT spectra and the H$\alpha$ emission line in the ESO 1.52-m and INT spectra. The position, the FWHM and the uncalibrated flux of the emission lines were individually determined by fitting interactively a single Gaussian to each emission line, and a polynomial to its surrounding continuum using the MIDAS package ALICE. The wavelength of the Gaussian peak was converted to velocity via the optical convention v=cz, and then the standard heliocentric correction was applied to obtain the ionized gas heliocentric velocity ($v_{\rm g}$). The Gaussian FWHM was corrected for the instrumental FWHM, and then converted to velocity dispersion ( $\sigma _{\rm g}$). At some radii where the intensity of the emission lines was low, we averaged adjacent spectral rows to improve the signal-to-noise ratio of the lines. The ionized-gas kinematic parameters of all the sample galaxies are tabulated in Table 6. The table provides the galaxy name, the position angle of the slit in degrees, the radial distance from the galaxy centre in arcsec, the observed heliocentric velocity and the velocity dispersion in  $\rm km\;s^{-1}$, and the relevant emission line. For each galaxy we derive the heliocentric system velocity as the velocity of the centre of symmetry of the rotation curve of the gas.