2 Spectroscopic observations

The spectroscopic data were collected during six runs of observations, between 1992 and 1996, using the ESO NTT in La Silla (the first run in visitor mode and the other three in remote observing mode from Garching) and the 3.5 m telescope in Calar Alto. Table 1 summarizes the instruments and detectors used and their setups. Table 2 gives the log of the observations. To maximize the signal at large radii, large slit widths were used. These rather than seeing set the spatial resolution of the observations in all cases except run #1.

   

Table 2: Log of the spectroscopic observations. Column 1 gives the galaxy name, Col. 2 the run number (see Table 1), Col. 3 the slit position angle in degrees, Col. 4 the position across the galaxy (see notes), Col. 5 the shift from the center (see text), Col. 6 the exposure time, Col. 7 the number of collected frames

Galaxy	Run	PA	Position1	Shift	Exp.Time	Number
		[$^{\rm o}$]		['']	[hours]	of Frames
NGC 315	2	44	MJ	-	0.71	1
	5	135	pMN	58	6.72	5
NGC 3379	6	80	MJ	-	1.5	1
	6	170	pMN	35	12	8
NGC 4374	6	126	MJ	-	1.5	1
	6	36	pMN	17	1.8	2
	6	36	pMN	55	3.3	2
NGC 5846	2	70	MJ	-	2.5	2
	2	160	pMN	80	7.5	5
NGC 7145	2	160	MJ	-	1.5	1
	2	270	pMN	38	14.3	12
NGC 7192	4	10	MJ	-	1.5	1
NGC 7507	1	72	D	-	1.75	2
	12	18	pMN	48	5	5
NGC 7626	3	15	MJ	-	1.5	1
	5	105	pMN	57	9.4	7
(1) MJ: major axis; pMN: parallel to the minor axis; D: diagonal.
(2) Slit width 1.5''.

The standard reduction steps (bias subtraction, flat fielding, cosmic ray removal, logarithmic wavelength calibration, sky subtraction) were performed under MIDAS. A sky subtraction better than 1 per cent was achieved. The analysis of the data was carried out using the FCQ method (Bender [1990]) following BSG94, G+98 and S+2000. The spectra were rebinned along the spatial direction to obtain a nearly constant signal-to-noise ratio larger than 50 per resolution element. The effects of the continuum fitting and instrumental resolution were extensively tested by Monte Carlo simulations. The residual systematic effects on the values of the h₃ and h₄ profiles are less than 0.01, and less than 1.5% in $\sigma$. In general, in the inner parts of the galaxies the errorbars (which reflect the random errors and do not take into account systematic effects such as template mismatching or the presence of dust and faint emission, see below) are small, in the range 3 - 7 km s^-1 for the recessional velocities and velocity dispersion, and 0.006-0.02 for the h₃ and h₄ coefficients. The errors are larger in the outer parts, where the signal-to-noise ratio can be lower. They are calibrated with simulations and are determined to better than 20%. Figures 1 and 2 present the results. Figures 3-8 compare the data to the literature. We discuss individual galaxies here below. Note that NGC 315, NGC 7507 and NGC 7145 appear to have noisier data than the rest, despite the long integration times (see Table 2). NGC 315 is the most distant galaxy of the sample, NGC 7507 has been observed with a tighter slit and NGC 7145 is the intrinsically faintest galaxy of the sample (see Table 3).

Figure 1: The kinematics of NGC 315, NGC 3379, NGC 4374, NGC 5846. From bottom to top: the folded mean velocity, velocity dispersion, h3 and h4profiles. Stars and filled circles refer to the two sides of the galaxy and the major axis spectrum. Crosses and open squares refer to the two sides of the galaxy and the spectra taken parallel to the minor axis and shifted 58 (NGC 315), 35 (NGC 3379), 55 (NGC 4374) and 80 (NGC 5846) arcsec from the center. Open and filled triangles refer to the two sides of NGC 4374 and the spectra taken parallel to the minor axis and shifted 17 arcsec from the center

Figure 2: The kinematics of NGC 7145, NGC 7192, NGC 7507, NGC 7626. From bottom to top: the folded mean velocity, velocity dispersion, h3 and h4profiles. Stars and filled circles refer to the two sides of the galaxy and the major axis spectrum. Crosses and open squares refer to the two sides of the galaxy and the spectra taken parallel to the minor axis and shifted 38 (NGC 7145), 48 (NGC 7507) and 57 (NGC 7626) arcsec from the center

2.1 NGC 315

The spectra in the inner 2 arcsec show variable H$\beta$ emission, which is probably responsible for the jumps observed in the v and $\sigma$values. The two most distant datapoints have rather poor signal-to-noise ratio. The related values of h₃ and h₄ are very uncertain; only the values of $\sigma$ and v are given. The comparison with the old data of Schechter & Gunn (1979) and the velocity profile of Davies & Birkinschaw ([1988]) (Fig. 3) is good within the rather large errors of the literature data.

Figure 3: Left: comparison with the velocity dispersion (top) and rotation velocities (bottom) of Schechter & Gunn ([1979], crosses) and Davies & Birkinshaw ([1988], only velocities, open triangles) for NGC 315. Right: comparison with the velocity dispersion (top) and rotation velocities (bottom) of Davies & Birkinshaw ([1988], crosses) for NGC 4374. The data of Carollo et al. ([1993]) have large error bars, within which they agree with our profiles

2.2 NGC 3379

The data taken along the major axis of the galaxy follow closely the results of Statler & Smecker-Hane ([1999]) (Fig. 4). The data along the shifted direction reach 100 arcsec from the center and show a declining (cylindrical) velocity, with negative values at 100 arcsec confirmed in the 8 separate frames.

The velocity dispersions and h₄ values along the major axis given in BSG94 (not shown here) appear slightly larger. The h₃ values and velocities agree well.

Figure 4: The kinematics of NGC 3379 compared to the results of Statler & Smecker-Hane ([1999]). From bottom to top: the folded mean velocity, velocity dispersion, h3 and h4profiles. Stars and filled circles refer to the two sides of the galaxy and the major axis spectrum obtained here. Open and filled squares refer to the major axis data of Statler & Smecker-Hane ([1999]). Note the changes of scales between the left and the right rows

2.3 NGC 4374

The galaxy shows OIII emission in the inner 3 arcsec, where some differences between the two sides of the galaxy in the (folded) velocity, h₃ and $\sigma$ appear larger than the errorbars. No rotation is detected along the major axis; there is a hint of a 10 km s^-1 (cylindrical) rotation as measured parallel to the minor axis (the 17 arcsec shift). Apart from the inner 3 arcsec (where emission is seen) there is no template mismatching. The last datapoint has low S/N and h₄ might not be reliable. The antisymmetric term h₃ is approximately zero everywhere; the h₄ is small and slightly positive.

The comparison with the v and $\sigma$ profile of Davies and Birkinshaw ([1988]) is satisfactory (Fig. 3). Their $\sigma$ data tend to be systematically higher than ours (at most 20 km s^-1 at R=10 arcsec). This might be due to their bad spectral resolution and/or differences in the slit aperture. Carollo et al. ([1993]) compare their data (affected by rather large errors) with Davies & Birkinshaw ([1988]), finding agreement.

2.4 NGC 5846

The galaxy shows a slowly declining velocity dispersion, with no rotation and small h₃ and h₄ values.

Comparisons are given for the v and $\sigma$ profiles to the data of Franx et al. ([1989]) and BSG94, where reasonable agreement is obtained (Fig. 5). The same is achieved for the data of Carollo et al. ([1993]), which have large errors and are not shown here. Sembach & Tonry ([1996]) obtained a radially extended major axis kinematic profile with a pioneering (hardware) method to perform sky subtraction. The authors themselves note that their values are 6-7% higher than previous observations. Somewhat higher bias is observed here. The h₃ and h₄ data given by BSG94 are compatible with the present dataset, within their large errors.

Figure 5: Comparison with the velocity dispersion (top) and rotation velocities (bottom) of Franx et al. ([1989], crosses), BSG94 (open squares), Sembach & Tonry ([1996], open triangles). The data of Carollo et al. ([1993]) have large error bars, within which they agree with our profiles. Note the change of scale at 19 arcsec

Figure 6: Left: comparison with the velocity dispersion (top) and rotation velocities (bottom) of Franx et al. ([1989], crosses) for NGC 7145. Right: comparison with the velocity dispersion (top) and rotation velocities (bottom) of Carollo & Danziger ([1994], major axis: crosses, minor axis: open squares, diagonal axis: open squares) for NGC 7192

Figure 7: Comparison with the velocity dispersion (top) and rotation velocities (bottom) of Franx et al. ([1989], crosses), Bertin et al. ([1994], open squares). Note the change of scale at 10 arcsec

Figure 8: Comparison with the velocity dispersion (top) and rotation velocities (bottom) of Balcells & Carter ([1993], crosses), Jedrzejewski & Schechter ([1989], open squares). Note the change of scale at 10 arcsec

2.5 NGC 7145

The galaxy has a rather low velocity dispersion, at the limit of the instrumental resolution ( $\sigma\approx 120$ km s^-1, $\sigma_{\rm inst}=85$ km s^-1). Simulations show that there might be still some systematic effects at the 3% level in $\sigma$ and 0.01-0.02 in h₄. The velocity data parallel to the minor axis are mirrored antisymmetrically with respect to the major axis. The velocity dispersions measured by Franx et al. ([1989]) are consistent within the errors. Their velocity measured along $\rm PA=132^0$ matches our value detected parallel to the minor axis (Fig. 6).

2.6 NGC 7192

The galaxy has some OIII emission and is detected in H$\alpha$(Macchetto et al. [1996]). The scatter in the velocities is probably due to this component. The velocity dispersion profile agrees with the central value (185 km s^-1) of Faber et al. ([1989]). The kinematic data of Carollo & Danziger ([1994]) are however completely off, being 50 to 70 km s^-1 larger (Fig. 6). The fact that their major and minor axis data do not agree suggests that this dataset is not reliable.

2.7 NGC 7507

The galaxy shows a slowly declining velocity dispersion profile, with low rotation, small h₃ and slightly positive h₄ values. The systematic differences with the velocity dispersion profiles of Franx et al. ([1989]) and Bertin et al. ([1994], Fig. 7) might be partly due to the 1 arcsec slit used here.

2.8 NGC 7626

As discussed in Balcells & Carter ([1993]), the inner region of this galaxy is not relaxed. The differences between its two sides are real and reflect the complex kinematics. Some template mismatching is still present at $R\approx 10-$ 30 arcsec.

The comparison with the velocity and velocity dispersion profiles of Balcells & Carter ([1993]) is good within the errors; the $\sigma$data of Jedrzejewski & Schechter ([1989]) are systematically on the lower side.