2 Observations and data reductions

2.1 Observations

The observations were carried out at the 42-inch (1.06 m) telescope of the Lowell Observatory located on the Anderson Mesa dark side during several nights in December 1988 (run identification: L1) and January 1989 (L2) and at the 2.2 m telescope at ESO/La Silla during three runs in June 1985 (E1), March (E2) and June (E3) 1987. At the 42-inch telescope we used a 2:1 focal reducer with the f/8 secondary, equipped with a CCD camera which is based on a thinned TI $800\times 800$ WFPC 1 CCD with 15 $\mu$m pixelsize resulting in a field of approximately 9 $\hbox{$^\prime$ }$ with a scale of 0.7 $\hbox{$^{\prime\prime}$ }$ pixel^-1. Images were taken with a standard Johnson R filter. Observations at the 2.2 m telescope were carried out with the ESO CCD adapter using a $512\times 320$ RCA chip, giving an effective field size of $\approx 3\hbox{$^\prime$ }\times 2\hbox{$^\prime$ }$ and a scale of 0.36 $\hbox{$^{\prime\prime}$ }$ pixel^-1. For the ESO observing runs we used the g, r, and i filters of the Thuan & Gunn ([1976]) system. Exposures were mainly taken in the g or r band, and only seven galaxies were observed in all three filters.

2.2 Sample selection

The northern sample observed at Lowell was selected automatically in an electronic version of the UGC-catalog (Nilson [1973]) searching for galaxies with an inclination class 7 matching the field size. After visual inspection to check the inclination and remove interacting and disturbed galaxies, the observed sample was chosen out of the remaining galaxies according to the allocated observing time.

For the southern sky there is no comparable catalog providing information of inclinations directly. Using the axial ratios given e.g. in the ESO-Lauberts & Valentijn catalog ([1989]) will introduce a selection bias preferring late type galaxies with lower B/D ratio (Guthrie [1992]; Bottinelli et al. [1983]). One way to avoid this is extending the first selection to much lower axis ratios, comparable to $i \approx 65\hbox{$^\circ$ }$, and then checking the inclination by eye. Therefore we selected the galaxies according to the field size of about $2\hbox{$^\prime$ }$ from a visual inspection of film copies of the southern sky survey (see Paper I).

Table 1 gives a list of the resulting sample used during our fitting process, with a serial number (1), the principal galaxy name (2), the used filter (3), the integration time in minutes (4), and the run identification label (5), whereas the "$\star$'' marks images already published in Paper I. Further parameters are taken from the RC3 catalogue (de Vaucouleurs et al. [1991]): the right ascension (6) and declination (7), the RC3 coded Hubble-type (8), the Hubble parameter T (9), and the D₂₅ diameter in arcminutes (10). In the case of ESO 578-025 parameters are taken from the ESO-Uppsala catalogue (Lauberts [1982]).

 

 

Table 1: Global parameters of sample galaxies with models

No.	name	filter	$t_{{\rm int.}}$	run	RA	DEC	RC3	T	D25	$v_{\hbox{$\odot$ }}$	D
			[min]	ID	(2000.0)		type		[ $\;\hbox{$^\prime$ }\;$]	km s-1	Mpc
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)
1	ESO 112-004	r	40	E3$\star$	002804.2	-580611	.S.R6*.	5.6	1.32	--	--
2	ESO 150-014	r	20	E3$\star$	003637.9	-565424	.L..+*/	-0.7	1.91	8257	107.05
3	NGC 585	R	20	L1	013142.5	-005555	.S..1*/	1.0	2.14	5430	72.15
4	ESO 244-048	r	15	E3	013908.8	-470742	.S..3./	3.0	1.38	6745	87.09
5	NGC 973	R	10	L1	023420.2	+323020	.S..3..	3.0	3.72	4853	66.28
6	UGC 3326	R	30	L1	053936.0	+771800	.S..6*.	6.0	3.55	4085	57.82
7	UGC 3425	R	30	L1	061442.0	+663400	.S..3..	3.0	2.51	4057	57.04
8	NGC 2424	R	15	L1	074039.8	+391359	.SBR3*/	3.0	3.80	3113	43.10
9	IC 2207	R	10	L2	074950.8	+335743	.S..6*.	6.0	2.04	4793	65.10
10	ESO 564-027	r	30	E2	091154.4	-200703	.S..6*/	6.3	4.07	2177	26.93
11	ESO 436-034	g	60	E3$\star$	103244.2	-283646	.S..3./	3.0	2.09	3624	46.02
12	ESO 319-026	g	30	E3$\star$	113020.0	-410357	.S..5./	5.3	1.48	3601	45.32
12	ESO 319-026	i	30	E3
12	ESO 319-026	r	30	E2
12	ESO 319-026	r	30	E3$\star$
13	ESO 321-010	g	30	E3$\star$	121142.2	-383253	.S..0*/	0.0	1.86	3147	39.53
13	ESO 321-010	r	30	E3$\star$
14	NGC 4835A	r	40	E3$\star$	125713.6	-462243	.S..6*/	6.0	2.57	3389	42.54
15	ESO 575-059	r	15	E2	130744.5	-192348	.LA.+?/	-0.8	1.86	4570	59.78
16	ESO 578-025	g	30	E2	140815.5	-200019	--	1.0	1.60	6364	83.93
16	ESO 578-025	g	30	E3$\star$
16	ESO 578-025	i	30	E2
16	ESO 578-025	r	30	E2
17	ESO 446-018	r	30	E2	140838.7	-293412	.S..3./	3.0	2.34	4774	62.15
18	IC 4393	r	30	E2	141749.5	-312056	.S..6?/	6.0	2.40	2754	35.15
19	ESO 581-006	r	30	E3$\star$	145803.1	-192329	.SBS7P/	7.0	1.70	3119	40.91
20	ESO 583-008	r	30	E3	155750.5	-222947	.S?....	6.0	1.51	7399	97.98
21	UGC 10535	r	25	E2	164600.0	+062800	.S..2..	2.0	1.10	7586	102.48
22	NGC 6722	r	10	E3$\star$	190339.6	-645341	.S..3./	3.0	2.88	5749	73.79
23	ESO 461-006	r	60	E3$\star$	195155.9	-315852	.S..5./	5.0	1.62	5949	78.26
24	IC 4937	g	20	E1	200518.0	-561520	.S..3./	3.0	1.95	2337	28.68
24	IC 4937	i	20	E1
24	IC 4937	r	30	E3$\star$
25	ESO 528-017	g	30	E3$\star$	203320.8	-270549	.SB.6?/	5.7	1.59	6115	80.73
25	ESO 528-017	i	30	E3
25	ESO 528-017	r	60	E3$\star$
26	ESO 187-008	r	30	E3$\star$	204325.2	-561217	.S..6./	6.0	1.51	4412	56.31
27	ESO 466-001	i	40	E3	214232.3	-292210	.S..2./	2.0	1.38	7068	93.13
28	ESO 189-012	g	60	E3$\star$	215538.7	-545233	.SA.5*/	5.0	1.66	8398	109.04
28	ESO 189-012	i	20	E3
28	ESO 189-012	r	30	E3$\star$
29	ESO 533-004	r	20	E1	221403.2	-265618	.S..5*/	4.8	2.34	2594	33.54
30	IC 5199	g	30	E3$\star$	221933.0	-373201	.SA.3*/	3.0	1.55	5061	65.78
30	IC 5199	i	30	E3
31	ESO 604-006	r	30	E3$\star$	231454.0	-205944	.S..4./	4.0	1.86	7636	100.92
$\star$ Marks images already published in Paper I.

2.3 Data reduction

We applied standard reduction techniques for bias subtraction, bad pixel correction and flatfielding. Following the procedure described in Paper I the sky background was fitted for each image using the edges of the individual frames to reduce any large scale inhomogeneity in the field of view. For part of the data we tried to remove the foreground stars from the image, but even with sophisticated PSF fitting using IRAF-DAOphot routines we were not able to remove stars without any confusion. The remaining residuals were always of the order of the discussed signal. This technique could only be used to mask out the regions affected by stars. In order to increase the signal-to-noise ratio near the level of the sky background part of the data was filtered using a weighted smoothing algorithm (see Paper I). Thereby the noise was reduced by about one magnitude measured with a three sigma deviation on the background, whereas the interpretation of the faint structure is hampered by this process.

We therefore conclude that the best way is to omit any additional image modifications, besides a rotation of the image to the major axis of the disk.

   
2.4 Photometric calibration

Most of the images were taken during non-photometric nights, therefore we tried a different way to perform photometric calibration. Comparing simulated aperture measurements with published integrated aperture data led to the best possible homogeneous calibration of the whole sample. Most of the southern galaxies were calibrated using the catalogue of Lauberts & Valentijn ([1989]), whereas NED was used for all northern galaxies. We used Eq. (1) derived in Paper I for the colour transformation of R and B literature values and the g measurements, and no correction between the R and r, and I and i band, respectively. Due to the fact that the photometric errors, of the input catalogues from Lauberts & Valentijn ([1989]) as well as within the RC3 catalogue (de Vaucouleurs et al. [1991]) are of the order of 0.1 mag, we do not apply any further corrections. Galaxies calibrated in this way are marked with l in column (5) of Table 2, whereas for galaxies which did not have published values for their magnitude in the observed filter, we interpolated from calibrated images of the same night, by comparing the count rates for the sky value. These galaxies are marked with an i. For a few nights no galaxy with published photometry was observed and in these cases we used interpolated night sky values from the same observing run. Images calibrated in this way are marked with e in Table 2. The resulting zero points and central surface brightness values in these cases should be interpreted carefully, although the derived structural parameters, like scalelength and scaleheight, are not influenced by any uncertainty in the flux calibration. Appendix A shows the contour plots and selected radial profiles for the 14 objects (25 images) not already published in Paper I.

2.5 Distance estimates

In order to derive the intrinsic values of the scale parameters and to compare physical dimensions we tried to estimate distances for our galaxies. Therefore we took published radial velocities corrected for the Virgo centric infall from the LEDA database, and estimated the distance following the Hubble relation with a Hubble constant of $H_{0}\!=\!75$ km s^-1 Mpc^-1. Table 1 gives the heliocentric radial velocities (11) according to LEDA, and our estimated distances (12).