2 Sample selection, spectroscopic observations and data reduction

All the observed galaxies are bright ( $B_{\rm T}\leq13.5$) and nearby ( $V_\odot < 5800$  $\rm km~s^{-1}$) with an intermediate-to-high inclination ( $45^\circ\leq i \leq 80^\circ$). The Hubble morphological types of the sample galaxies range from S0 to Sd and 5 objects are barred or weakly barred (RC3). The galaxies have been chosen to have strong emission lines. An overview of their basic properties is given in Table 1. In Fig. 1 we show the absolute magnitude distribution for the galaxies in our sample. The distribution brackets the $M^\ast$ value for spiral galaxies taken from Marzke et al. (1998) for H₀ = 75  $\rm km~s^{-1}~Mpc^{-1}$.

 

 

Table 1: Parameters of the sample galaxies.

Object	Morp. Type		$B_{\rm T}$	PA	i	$V_{\odot}$	D	Scale	$M_{B_{\rm T}}^0$	$\sigma_\star$	$M_\bullet$	$\theta_\bullet$	Nuc. Type
[name]	[RSA]	[RC3]	[mag]	[$^\circ$]	[$^\circ$]	[ $\rm km~s^{-1}$]	[Mpc]	[pc/'']	[mag]	[ $\rm km~s^{-1}$]	[$M_{\odot }$]	['']
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)
NGC 470	Sbc(s)II.3	.SAT3..	12.53	155	52	2370	33.8	163.9	-20.66	56	3.2 e+05	0.003	...
NGC 772	Sb(rs)I	.SAS3..	11.09	130	54	2470	35.6	172.7	-22.21	124	1.4 e+07	0.02	...
NGC 949	Sc(s)III	.SAT3*$	12.40	145	58	620	11.4	55.2	-18.50	32	2.3 e+04	0.002	...
NGC 980	...	.L.....	13.16	110	58	5765	80.1	388.2	-22.95	226	2.3 e+08	0.06	...
NGC 1160	...	.S..6*.	13.50	50	62	2510	36.6	177.4	-21.01	24	5.9 e+04	0.0003	...
NGC 2179	Sa	.SAS0..	13.22	170	47	2885	36.5	177.0	-19.98	166	5.4 e+07	0.05	...
NGC 2541	Sc(s)III	.SAS6..	12.26	165	61	565	8.7	42.2	-18.13	53	2.5 e+05	0.01	T2/H:
NGC 2683	Sb(on edge)	.SAT3..	10.64	44	78	400	5.3	25.6	-18.99	83	2.0 e+06	0.06	L2/S2
NGC 2768	S01/2(6)	.E.6.*.	10.84	95	59	1331	19.4	94.1	-20.74	205	1.5 e+08	0.2	L2
NGC 2815	Sb(s)I-II	.SBR3*.	12.81	10	72	2541	30.5	147.7	-21.00	168	5.7 e+07	0.07	L/S2
NGC 2841	Sb	.SAR3*.	10.09	147	65	640	9.6	46.4	-20.33	197	1.2 e+08	0.3	L2
NGC 3031	Sb(r)I-II	.SAS2..	7.89	157	59	-50	1.5	7.2	-18.46	173	6.6 e+07	1.5	S1.5
NGC 3281	Sa	.SAS2P*	12.70	140	61	3380	41.1	199.5	-21.25	172	6.4 e+07	0.05	S2
NGC 3368	Sab(s)II	.SXT2..	10.11	5	47	865	9.7	47.1	-20.14	129	1.6 e+07	0.1	L2
NGC 3521	Sb(s)II-III	.SXT4..	9.04	163	63	825	8.5	41.1	-20.35	145	2.8 e+07	0.2	H/L2:
NGC 3705	Sab(r)I-II	.SXR2..	11.86	122	66	1000	11.4	55.2	-19.03	109	7.4 e+06	0.05	T2
NGC 3898	SaI	.SAS2..	11.60	107	54	1184	17.1	82.9	-19.85	223	2.2 e+08	0.3	T2
NGC 4419	SBab:	.SBS1./	12.08	133	71	-210	17.0	82.4	-19.55	98	4.5 e+06	0.03	H
NGC 4698	Sa	.SAS2..	11.46	170	52	992	17.0	82.4	-19.91	174	6.7 e+07	0.1	S2
NGC 5064	Sa	PSA.2*.	13.04	38	63	2980	36.0	174.4	-21.11	202	1.4 e+08	0.09	L
NGC 7320	...	.SAS7..	13.23	132	60	862	15.4	74.7	-18.39	...	...	...	...
NGC 7331	Sb(rs)I-II	.SAS3..	10.35	171	70	820	14.7	72.0	-21.48	141	2.5 e+07	0.09	T2
NGC 7782	Sb(s)I-II	.SAS3..	13.08	175	58	5430	75.3	364.9	-21.95	193	1.1 e+08	0.04	...

Notes - Column 2: morphological classification from RSA. Column 3: morphological classification from RC3. Column 4: total observed blue magnitude from RC3 except for NGC 980 and NGC 5064 (LEDA). Column 4: major-axis position angle taken from RC3. Column 6: inclination derived from $\cos^{2}{i}~=~(q^2-q_0^2)/(1-q_0^2)$. The observed axial ratio q is taken from RC3 and the intrinsic flattening q₀=0.11 has been assumed following Guthrie (1992). Column 7: heliocentric velocity of the galaxy derived from the center of symmetry of the rotation curve of the gas. They are taken from Vega Beltrán et al. (2001) except for NGC 2179, NGC 3281 and NGC 4698 (Corsini et al. 1999). Column 8: distance obtained as V₀/H₀ with H₀=75 $\rm km~s^{-1}~Mpc^{-1}$ and V₀ the systemic velocity derived from $V_{\odot}$ corrected for the motion of the Sun with respect of the Local Group according to the RSA. For NGC 4419 and NGC 4698, which belong to the Virgo cluster, we assume a distance of 17 Mpc (Freedman et al. 1994). Column 10: absolute total blue magnitude corrected for inclination and extinction from RC3. Column 11: central velocity dispersion of the stellar component. Data are from Vega Beltrán et al. (2001) except for NGC 2179, NGC 3281 (Corsini et al. 1999), NGC 2768 (Bertola et al. 1995), NGC 2815 (LEDA), NGC 3521 (Zeilinger et al. 2001), and NGC 4698 (Bertola et al. 1999). Column 12: expected mass of the central SMBH derived from $\sigma_\star$ following Merritt & Ferrarese (2001a). Column 13: angular size of the radius of influence of the central SMBH derived from $\theta_\bullet \approx M_\bullet\;\sigma_{\star}^{-2}\;D^{-1}$ (de Zeeuw 2001), where $M_\bullet$ is the mass of the SMBH in units of 10⁶ $M_{\odot }$, $\sigma_\star$ is the central velocity dispersion in units of 100  $\rm km~s^{-1}$, and D is the galaxy distance in Mpc. Column 14: classification of the nuclear spectrum from Ho et al. (1997) except NGC 2815 (Véron-Cetty & Véron 1986). H = H  II nucleus. L = LINER. S = Seyfert nucleus. T = transition object. ... = uncertain.

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  $\rm km~s^{-1}~Mpc^{-1}$. The dashed region identifies galaxies classified barred or weakly barred in RC3.

The long-slit spectroscopic observations of our sample galaxies were carried out at the 4.5-m Multiple Mirror Telescope (MMT) in Arizona (USA), at the 3.6-m ESO Telescope at La Silla (Chile), and at the 2.5-m Isaac Newton Telescope (INT) at La Palma (Spain). Details about the instrumental setup and the seeing of each observing run are summarized in Table 2.

 

 

Table 2: Instrumental setup for spectroscopic observations.

Parameter	MMT		INT	3.6-m ESO
Date	21-23 Oct. 1990	17-18 Dec. 1990	19-20 Mar. 1996	03-04 Feb. 1997
Spectrograph	Red Channel$\rm ^a$		IDS$\rm ^a$	CASPEC$\rm ^b$
Grating ( $\rm grooves\;mm^{-1}$)	1200		1800	31.6
Detector	Loral $12\times8$mmt		TK1024A	TK1024AB
Pixel size ( $\rm\mu m^{2}$)	$15\times15$		$24\times24$	$24\times24$
Pixel binning	$1\times1$		$1\times1$	$1\times1$
Scale ( $\rm ''\;pixel^{-1}$)	0.30		0.33	0.33
Reciprocal dispersion ( $\rm\AA\;pixel^{-1}$)	0.82		0.24	0.076
Slit width ('')	1.25		1.9	1.3
Slit length (')	3.0		4.0	2.4
Spectral range (Å)	4850-5500		6650-6890	6630-6651
Comparison lamp	He-Ne-Ar-Fe		Cu-Ar	Th-Ar
Instrumental FWHM (Å)	$2.24\pm0.26$	$2.57\pm0.11$	$0.869\pm0.040$	$0.233\pm0.017$
Instrumental $\sigma$$\rm ^c$ ( $\rm km~s^{-1}$)	57	65	5	17
Seeing FWHM ('')	1.2-1.5		1.0-1.4	0.8-1.2

$\rm ^a$ Grating used at the first order.
$\rm ^b$ CASPEC mounting of the Long Camera in long-slit configuration without crossdisperser. The spectral order #86 ( $\lambda_{\rm c} = 6617$ Å)
corresponding to the redshifted H$\alpha$ region was isolated by means of the narrow-band 6630/51 Å filter.
$\rm ^c$ The instrumental dispersion has been measured at [O  III] $~\lambda5007$, [N  II] $~\lambda6583$ and H$\alpha$ for the MMT, INT and 3.6-m ESO spectra, respectively.

At the beginning of each exposure, the slit was centered on the galaxy nucleus and aligned along the galaxy major axis using the guide TV camera. The slit orientation and the exposure times are given in Table 3. A comparison-lamp spectrum was obtained before and after each object integration to allow an accurate wavelength calibration. Quartz-lamp and twilight-sky flatfields were taken to map pixel-to-pixel sensitivity variations and large-scale illumination patterns.

Using standard MIDAS routines, the spectra were bias subtracted, flatfield corrected, cleaned for cosmic rays, and wavelength calibrated. Cosmic rays were identified by comparing the counts in each pixel with the local mean and standard deviation (based on the Poisson statistics of the photons are using the gain and readout noise of the detector). We corrected the data by interpolating a suitable value.

The instrumental resolution was derived as the mean of the Gaussian FWHMs measured for a number of unblended arc-lamp lines (12 in the MMT and INT spectra and 30 in the ESO spectra), which were 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 spectra were aligned and coadded using the centers of their stellar continua as reference. In the resulting spectra, the contribution from the sky was determined by interpolating along the outermost 10''-20'' at the edges of the slit, where galaxy light was negligible. The sky level was then subtracted.

 

 

Table 3: Log of spectroscopic observations.

Object	Date	Telescope	$t_{\rm exp}$	PA
[name]			[s]	[$^\circ$]
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 2179	03 Feb. 97	3.6-m ESO	$4\times3600$	170
	04 Feb. 97	3.6-m ESO	$2\times3600$	170
NGC 2541	21 Oct. 90	MMT	3600	165
NGC 2683	18 Dec. 90	MMT	3600	44
NGC 2768	19 Mar. 96	INT	$2\times3600$	95
NGC 2815	04 Feb. 97	3.6-m ESO	$3\times3600$	10
NGC 2841	22 Oct. 90	MMT	3600	147
NGC 3031	17 Dec. 90	MMT	3600	157
NGC 3281	04 Feb. 97	3.6-m ESO	3600	140
NGC 3368	17 Dec. 90	MMT	3600	5
NGC 3521	17 Dec. 90	MMT	3600	342
NGC 3705	17 Dec. 90	MMT	3600	122
NGC 3898	19 Mar. 96	INT	$3\times3600$	107
NGC 4419	20 Mar. 96	INT	$2\times3300$	133
	20 Mar. 96	INT	3600	133
NGC 4698	20 Mar. 96	INT	3600	170
NGC 5064	03 Feb. 97	3.6-m ESO	$3\times3600$	38
	04 Feb. 97	3.6-m ESO	3600	38
NGC 7320	22 Oct. 90	MMT	3600	132
NGC 7331	22 Oct. 90	MMT	3600	171
NGC 7782	22 Oct. 90	MMT	3600	30