4. Presentation of the work

From Fig. 1 (click here) to Fig. 44 (click here), we present results of observations. For each galaxy we give a DSS image, a continuum image, a monochromatic map, a velocity field, a diagram of possible viewing angles, a graph of derived ellipsoid axis ratios and a line of sight velocity curve.
For NGC 404, we have 3 monochromatic maps (H, [NII] 6584 Å and [OIII] 5007 Å). A H/[NII] map is also available.
For NGC 5866 H and [NII] 6584 Å maps are given. H/[NII] map was also derived.
Table 3 (click here) shows main properties of galaxy sample.

  
Figure 1: NGC 404: First is red image from Digitalized Sky Survey with North on the top and East on the left. Image total size is 3 arcmin. Second is continuum image of NGC 404 from our observations, SA represents the stellar axis

  
Figure 2: NGC 404: a) H monochromatic map, contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest is 6.6 and step 16.6. b) [NII] 6584 Å map, contours are in same units with lowest level of 7.5 and step 6.6. c) [OIII] 5007 Å map (not calibrated). d) Velocity map derived from [OIII] 5007 Å observation. SA represents the stellar axis

  
Figure 3: NGC 404: a) Possible viewing angles in the plane. Case A: gas short axis. Case B gas long axis. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 4: NGC 404: a) Line of sight velocity diagram for the gas with respect of a . b) H/[NII] map, relative lowest level is 80 and step is 30

  
Figure 5: NGC 708: Same as NGC 404

  
Figure 6: NGC 708: Line of sight velocity diagram of the two gaseous components

  
Figure 7: NGC 708 Component #1: a) [NII] 6584 Å Monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 4 and step 2.7. b) Velocity map. SA is the stellar axis and GA the gas axis (which is different for velocity and monochromatic maps)

  
Figure 8: NGC 708 Component #2: a) [NII] 6584 Å Monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 1.5 and step 1.35 b) Velocity map. SA is the stellar axis and GA the gas axis (which is different for velocity and monochromatic maps)

  
Figure 9: NGC 708 Component #1: Possible viewing angles a) and axis ratios b)

  
Figure 10: NGC 708 Component #2: Possible viewing angles a) and axis ratios b)

  
Figure 11: NGC 1052: Same as NGC 404

  
Figure 12: NGC 1052: Line of sight velocity diagram of the two gaseous components. A: Major component. B: Second component

  
Figure 13: NGC 1052 Component #1: a) [NII] 6584 Å Monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 3 and step 7. b) Velocity map. SA is the stellar axis and GA the gas axis (which is different for velocity and monochromatic maps)

  
Figure 14: NGC 1052 Component #2: a) [NII] 6584 Å Monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 3 and step 7. b) Velocity map. SA is the stellar axis and GA the gas axis (which is different for velocity and monochromatic maps)

  
Figure 15: NGC 1052: Possible viewing angles for component #1 a) and component #2 b). Case A: gas short axis. Case B gas long axis

  
Figure 16: NGC 1052: Possible axis ratios for component #1 a) and for the hypothesis of b)

  
Figure 17: NGC 2974: Field image from Digitalized Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) [NII] 6584 Å\ monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 4.1 and step 22.5. c) Velocity field. SA represents the stellar axis

  
Figure 18: NGC 2974: Line of sight velocity diagram

  
Figure 19: NGC 2974: a) Possible viewing angles in the plane. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 20: NGC 4546: Field image from Digitalized Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) [NII] 6584 Å\ monochromatic map. Contours are in units of 10^-17 ergs^-1 cm^-2 arcsec^-2. Lowest 15.6 and step 16.4. c) Velocity field. SA represents the stellar axis, GA represents the gas axis

  
Figure 21: NGC 4546: Line of sight velocity diagram

  
Figure 22: NGC 4546: a) Possible viewing angles in the plane. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 23: NGC 5846: Field image from ESO Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) [NII] 6584 Å monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 7.2 and step 9.64. c) Velocity field. SA represents the stellar axis, GA represents the gas axis

  
Figure 24: NGC 5846: Line of sight velocity diagram

  
Figure 25: NGC 5846: a) Possible viewing angles in the plane. Case A: gas short axis. Case B gas long axis. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 26: NGC 5866: Field image from ESO Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) H monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 7.3 and step 7.3. (c) [NII] 6584 Å monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 19.5 and step 19.5. SA represents stellar axis

  
Figure 27: NGC 5866: a) H/[NII] map, relative lowest level is 25 and the step 40. b) Velocity map of H+[NII] emission. SA is the stellar axis

  
Figure 28: NGC 5866: a) Possible viewing angles in the plane. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 29: NGC 5866: Line of sight velocity diagram

  
Figure 30: NGC 5898: Field image from Digitalized Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) H monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2 Lowest 9.4 and step 16.4. c) Velocity field. SA represents the stellar axis, GA represents the gas axis

  
Figure 31: NGC 5898: Line of sight velocity diagram

  
Figure 32: NGC 5898: a) Possible viewing angles in the plane. Case A: gas short axis. Case B gas long axis. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 33: NGC 6868: Field image from Digitalized Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) [NII] 6584 Å\ monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 10.0 and step 5. c) Velocity field. SA represents the stellar axis, GA represents the gas axis

  
Figure 34: NGC 6868: Line of sight velocity diagram

  
Figure 35: NGC 6868: a) Possible viewing angles in the plane. Case A: gas short axis. Case B gas long axis. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 36: NGC 7014: Field image from Digitalized Sky Survey, total size is 3 arcmin. a) Continuum image from our observations. b) [NII] 6584 Å\ monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 7.5 and step 15. c) Velocity field. SA represents the stellar axis, GA represents the gas axis

  
Figure 37: NGC 7014: Line of sight velocity diagram

  
Figure 38: NGC 7014: a) Possible viewing angles in the plane. Case A: gas short axis. Case B gas long axis. b) Possible axis ratios for the ellipsoid (S = short, I = intermediate, L = long) in accordance of values of showed in a)

  
Figure 39: NGC 7332: Same as NGC 404

  
Figure 40: NGC 7332: Line of sight velocity diagram of the two gaseous components. A: Major component. B: Second component

  
Figure 41: NGC 7332 Component #1: a) H Monochromatic map. Contours are in units of 10^-17 erg s^-1cm^-2 arcsec^-2. Lowest 3 and step 7. b) Velocity map. SA is the stellar axis and GA the gas axis (which is different for velocity and monochromatic maps)

  
Figure 42: NGC 7332 Component #2: a) [NII] 6584 Å Monochromatic map. Contours are in units of 10^-17 erg s^-1 cm^-2 arcsec^-2. Lowest 3 and step 7. b) Velocity map. SA is the stellar axis and GA the gas axis (which is different for velocity and monochromatic maps)

  
Figure 43: NGC 7332: Possible viewing angles for component #1 a) and component #2 b). Case A: gas short axis. Case B gas long axis

  
Figure 44: NGC 7332: Possible axis ratios for component #1 hypothesis of

4.1. Geometrical and dynamical aspects

The two dimensional velocity field allows us to derive the true shape of the ellipsoid. Gas disks can be located in 2 preferred planes XY and YZ (Heiligman & Scharzschild 1979; Tholine et al. 1982). Using De Zeeuw & Franx (1989) model it has been possible to derive viewing angles and and possible axis ratios I/L and S/L with S for Short axis, I for Intermediate axis and L for Long axis (Bertola et al. 1991; Plana & Boulesteix 1996). Possible viewing angles and axis ratios are presented on plane and I/L - S/L plane with hatched regions. To summarize, angle represents the inclination angle of the gas disk with respect to the plane of the sky. It is derived from velocity map, fitting a circular motion model to deduce the angle. And angle is the orientation of the gas disk in the triaxial galaxy referential. Inclination value and uncertainties are visualized by a vertical hatched band on diagrams.

Table 4 (click here) summarizes geometrical informations coming from monochromatic and velocity map. Inclination and MA angles can be different for monochromatic and velocity maps. Gas ellipticities were estimated from isophotes where signal to noise ratio is at least 10 and distance to the center is sufficent to avoid any seeing effect. More precisely:
NGC 404 4'' to 10'' i.e. 0.14 to 0.36 effective radius ();
NGC 708 7'' to 14'' i.e. 0.1 to 0.2
NGC 1052 10'' to 20'' i.e. 0.28 to 0.56
NGC 2974 16'' to 20'' i.e. 0.66 to 0.8
NGC 4546 7'' to 12'' i.e. 0.26 to 0.44
NGC 5846 7'' to 12'' i.e. 0.26 to 0.44
NGC 5898 14'' to 18'' i.e. 0.7 to 0.9
NGC 6868 12'' to 17'' i.e. 0.5 to 0.51
NGC 7014 18'' to 22'' i.e. 1.2 to 1.46
NGC 7332 17'' to 22'' i.e. 1.13 to 1.46 .

   

Kinematical Morphological Kinematical Morphological

Major Axis of gas Major Axis of gas Inclination Inclination (km s^-1) NGC 404 Stars Gas [OIII] 5007Å Gas [NII] 6584Å NGC 708 Stars Gas #1 [NII] 6584 Å Gas #2 [NII] 6584 Å NGC 1052 Stars Gas #1 [NII] 6584 Å Gas #2 [NII] 6584 Å NGC 2974 Stars Gas [NII] 6584Å NGC 4546

Stars 1050¹ Gas [NII] 6584Å NGC 5846 Stars Gas [NII] 6584Å NGC 5866 Stars Gas [NII] 6584Å NGC 5898 Stars NGC 6868 Stars Gas [NII] 6584Å NGC 7014 Stars Gas [NII] 6584Å NGC 7332 Stars

Col 1: Name.
Col 2: Gas Major Axis (MA) from velocity map.
Col 3: Gas MA from monochromatic map.
Col 4: Inclination with respect of the plane of sky calculated from velocity map.
Col 5: Inclination with respect of the plane of sky calculated from monochromatic map.
Col 6: Stellar and gas ellipticities. .
Col 7: Heliocentric velocity.
¹Heliocentric Velocity from Faber et al. (1989).

4.2. Gas masses

Monochromatic maps were calibrated using the literature. We also take H/[NII] ratios from articles in order to deduce H luminosity when we have [NII] 6584 Å observations. To calculate gas masses we use Case B recombination in Osterbrock 1974.

where is expressed in , ) in 10^-14 erg cm^-2 s^-1, D in Mpc and in .

It only has been possible to have electron density for a few objects, for the majority of the object we took the value .

Table 5 (click here) gives the different gas masses for hot, warm and cool components. X and radio data are from Roberts et al. (1991) except for NGC 708 for which radio luminosity is from Fanti et al. (1977). Gas masses for HI cold gas and X-ray hot gas are also from Roberts et al. (1991). Far InfraRed (FIR) luminosity has been calculated using IRAS flux at 60 and 100 and with the formula given in the "Cataloged galaxies and QSO observed in the IRAS survey" from Londsdale et al. (1989).

where F(60)=2.58.10^-14 and F(100)=10^-14 . and are IRAS flux density in Jansky.

In Table 5 (click here) we give the total mass of the galaxy deduced from the maximum velocity of the line of sight velocity curve (Lequeux 1983). The last column gives the ratio of the ionized gas with respect to the total mass. As we can see ionized gas represents less than for most of the galaxy sample. Exception of NGC 5898 where ionized gas represents more than .

   

D (Mpc) log L(FIR) log L(X) log L(radio) Dust Hot Gas HI

( H₀ = 75) erg s^-1 erg s^-1 erg s^-1 hz^-1 Mass Mass Mass

N 404 10.0 -19.8 42.20 - - 0.89 - 1.20

N 708 63.1 -21.2 - - 37.15 - - -

N 1052 18.6 -20.9 42.27 40.36 37.53 18.62 - 11.48

N 2974 25.7 -20.1 42.44 40.35 < 36.30 148.00 9.54 15.85

N 4546 12.6 -19.2 41.55 - 35.39 10.90 - 2.57

N 5846 22.3 -20.9 < 41.34 41.33 35.90 < 102.30 66.06 < 0.5

N 5866 12.2 -19.6 42.83 39.60 35.45 145.47 < 22.38 0.37

N 5898 30.9 -19.9 41.78 39.30 < 36.41 < 17.49 < 11.75 < 4.78

N 6868 38.3 -21.2 42.77 - - 229.08 - 14.12

N 7014 67.0 -20.7 42.84 - - - - -

N 7332 19.5 -19.8 41.72 39.18 < 35.65 < 5.12 < 6.45 < 2.88

HII Gas Total Ionized gas/

10^-14 erg s^-1 mass mass total mass

erg cm² s^-1 10^-6

NGC 404 15.0 39.25 0.4 0.60 0.67

NGC 708 2.90 40.14 3.2 14.69 0.22

NGC 1052 57.0 40.37 5.5 1.61 3.40

NGC 2974 17.0 40.13 3.1 1.79 1.73

NGC 4546 9.50 39.26 0.4 0.21 1.90

NGC 5846 21.0 40.10 2.9 1.07 2.71

NGC 5866 110.00 40.29 4.6 2.57 1.79

NGC 5898 32.70 40.57 8.7 1.57 5.54

NGC 6868 14.00 40.39 5.8 4.23 1.37

NGC 7014 7.00 40.58 8.8 7.80 1.13

NGC 7332 54.00 40.39 5.7 3.75 1.52

4.3. Comments on individual objects

4.3.1. NGC 404

This SO galaxy is characterized by a strong and skewed dust lane (Barbon et al. 1982). HI was detected by Baars et al. (1976), molecular gas was observed by Wiklind & Henkel (1990). The velocity amplitude of the gas is low, km s^-1 and kinematical Major Axis (MA) of the gas is almost aligned with stellar MA. Figure 2 (click here) shows monochromatic images in H, [NII] 6584 Å and [OIII] 5007 Å emission lines. H and [NII] 6584 Å extensions are comparable but the [OIII] 5007 Å map shows a larger extension (about 30'') with two distinct lobes.
The weak difference between stellar MA and gas MA explains that the region of possible viewing angles is very wide. The case with gas perpendicular to the short axis is not constrained and the other case with gas perpendicular to the long axis is marginal. It is very hard to conclude in what plane the gas disk is situated.
Figure 4 (click here)b shows H/[NII] map. It's clear that this ratio is not constant for the total galaxy. The map shows a strong gradient between East and West. The mean value is 2.13 which is consistent with the literature (Kim 1989).

4.3.2. NGC 708

This E2 galaxy belongs to the Abell 262 cluster and it is usually qualified as a Cooling Flow. Baars et al. 1976 have discovered HI in emission but no gas mass has been derived. Molecular gas was also detected by Braine et al. (1994) he gives a superior limit for the mass but this limit is very low for an object who has to accrete 300 /year in the hypothesis of a cooling flow (Heckman et al. 1989). Observations show a double gaseous component. A monochromatic image and a velocity field have been derived for each of them. Both components are not counter rotating with respect to one another but Position Angles (PA) of the MA of both components are strongly different. The first one has a PA of the MA equal to and the second component has a PA of . So the second component is almost aligned with the stellar component and the first is decoupled with it. The viewing angle is quite well defined for the first component but for the second one there is no constraint at all.

4.3.3. NGC 1052

This galaxy is a well known E2 elliptical with gaseous disk (Davies et al. 1986). A detailed description of that object has been done by Plana & Boulesteix (1996). It has also been discovered a double gaseous component in that object.

4.3.4. NGC 2974

This isolated galaxy is one of the brightest objects of the sample. HI emission was discovered and an atomic gas disk has been put in evidence by Kim (1988). Ionized gas has been shown by Demoulin et al. (1984), Kim (1989) and Goudfrooij et al. (1994). Ionized gas kinematics has been studied by Bettoni (1992). This object also shows an X-ray emission (Forman et al. 1985). Contrary to most of elliptical galaxies, ionized gas and HI gas components MA of NGC 2974 are aligned with respect to stars. The viewing angle is not constrained at all because of the small difference between MA of gas and stars. This object is a good candidate for an internal origin of ionized gas.

4.3.5. NGC 4546

This galaxy is classified as an SB0 object. Galletta (1987) and Bettoni et al. (1991) put in evidence ionized gas in this object counter rotating with respect to the stars. We confirm this counter rotation and put constraints on the shape of this object. Viewing angles show that gaseous disks can lie in the ZY plane.

4.3.6. NGC 5846

This is an E0 galaxy in the G50 group with a companion NGC 5846A 1' to the south. The presence of atomic gas in that galaxy is not obvious, Roberts et al. (1991) only give a superior limit of HI gas mass ( ). A strong X-ray emission was detected with Einstein satellite (Forman et al. 1985). Demoulin et al. (1984) have studied the ionized gas component using numerical subtraction technique and results obtained with FP observation are in agreement with this study. The line of sight velocity diagram shows a non axisymetric rotation, the North West ) part has a velocity amplitude greater than the South East part ). Viewing angles diagram shows that both Prolate and Oblate possibilities are possible.

4.3.7. NGC 5866

The main characteristic of this SO galaxy is his strong dust lane along the major axis. There are two companions, NGC 5907 and NGC 5879. This object presents a multiphase ISM: HI was detected by Haynes et al. (1990) but only a superior limit was given for HI mass. X-ray emission has been observed (Roberts et al. 1991; Pellegrini 1994) with an extension of 7.7' along the major axis. Ionized gas has been found in that galaxy and the monochromatic map shows an extension of about 40'' with a major axis almost aligned with respect to the stars. The line of sight velocity diagram shows a non axisymetric motion. The NW part has a velocity of lower than the systemic velocity. viewing angle is not constrained. For this object too we have an H/[NII] map. The mean value on the ratio is 0.6. In that case too the ratio is not constant but the gradient is lower than in NGC 404.

4.3.8. NGC 5898

This galaxy is an E0 object with a companion (NGC 5903) 5' to the East. Only superior limits are given for HI and X-ray gas masses. Stars are in counter rotation with respect to the ionized gas as shown by Bertola & Bettoni (1988). In that case too, possible values region is wide ), and it is difficult to determine the global shape of the galaxy.

4.3.9. NGC 6868

This galaxy is classified as an E3 galaxy in the RC3 catalog and as an E2 in the RSA catalog. It belongs to the GR28 group with four other galaxies (Maia et al. 1989). Cold ISM is present with HI gas, but Roberts et al. (1991) give only a superior limit for the HI gas mass. NGC 6868 is the host galaxy of a radio source PKS 2005-489 (Savage et al. 1977). It was also detected with IRAS satellite in 60 m and 100 m. Ionized gas has been put in evidence in spectroscopy by Phillips et al. (1986) and with CCD imaging by Hansen et al. (1991), Buson et al. (1993) and Macchetto et al. (1996). The line of sight velocity diagram shows a flat curve with a velocity amplitude of . Possible viewing angles diagram show us that the more probable location plane of the gaseous disk is the XY plane (perpendicular to the short axis). The angle is more constrained with this possibility (). Possible axis ratios are also shown.

4.3.10. NGC 7014

It is classified as an SO object in the RC3 catalog. A companion is present 7' to the west. No informations are available in radio or X-rays domain, only dust has been put in evidence (Sparks et al. 1985), ionized gas has been observed by spectroscopically by Phillips et al. (1986). The monochromatic map shows a complex structure with a strong gradient. The line of sight velocity diagram shows a non axisymetric motion, the NE branch has a velocity amplitude higher than the SW branch. We also notice that in the SW direction beyond 10'', velocities are much spread out. On the geometry point of view, it seems that the Oblate possibility is the more probable with and .

4.3.11. NGC 7332

This object is classified as an SO galaxy in the RC3 catalog. We have observed a complex system of two gaseous components. A detailed study is presented by Plana & Boulesteix (1996).