6. Conclusion

We have obtained optical and near-infrared images, as well as low and high resolution optical spectra of a complete sample of Infrared Ultraluminous Galaxies in the Southern hemisphere (SULIRG). This database can be used for statistical studies and/or detailed works on individual objects. The general characteristics of the SULIRGs, briefly discussed in this paper, confirm the trends already noted from studies of other samples of ultraluminous IR galaxies: 1) most of these are interacting or merging systems and no instance of isolated normal objects has been found; 2) they have a high proportion of active nuclei. However there are exceptions to these general properties, since we found in our sample ultraluminous systems that consist of distant pairs, as well as complete mergers with no signs of nuclear activity.

Acknowledgements

We are grateful to Cecile Loup who obtained the spectrum of IRAS 00199-7426. We wish to thank Dave Sanders and Dave Clements for helpful discussions, and our referee, N. Bergvall, for critical comments. This program has made use of the NASA/IPAC Extragalactic Database which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

 

IRAS name Morphology Components Spectral type Ref

Class Features Main gal. Comp.

(1) (2) (3) (4) (5) (6) (7)

00199-7426 multiple interacting system one tail 7.7? (12.2?) - ? a

05189-2524 merging system two nuclei (HST) 0.3 (0.2) - SII b

06035-7102 close interacting system two disks, two tails 5.6 (7.5) -32 LI a SB = LI

06206-6315 merging system two nuclei, one tail 2.3 (3.5) - SII a

09061-1248 close interacting system two disks, two tails 4.7 (5.9) -136 SB a LI

09111-1007 ambiguous: normal galaxy ? spiral like <1.2 (1.1) SII > (SB?LI) a

bright companion to the East [40 (42)] [425] [SII = LI]

11095-0238 merger single nucleus, two tails <1.2 (2.1) - LI a,c

14348-1447 merging system two nuclei, two tails 3.5 (4.9) - LI b

14378-3651 complete merger one nucleus, distorted <1.2 (1.4) - SII a

15462-0450 ambiguous: interacting with bright nucleus, tail <1.2 (2) SI a,e

companion to the South ? [35 (67)] [180] [SB]

16090-0139 complete merger eccentric nucleus <1.4 (2.9) - - a,j

17208-0014 merger one nucleus, two tails <1.2 (0.9) - LI a,d

19254-7245 close interacting system two disks, two tails 7.8 (8.4) 149 SII a,f SII?LI

20046-0623 close interacting system "L'' shape, no clear nucleus 5 (7.1) - - a,j

20087-0308 merger elongated nucleus, two tails <0.9 (1.5) - SII?LI a {2.6 (4.5)}

20100-4156 close interacting system two disks 2.7 (5.4) - SB > LI -

20414-1651 ambiguous: complete merger ? one nucleus <1.5 (2.2) - LI > SB a

apparent companion to the East [24 (41)] -

20551-4250 merger one nucleus, one tail <1.2 (0.9) - LI = SB a,g

21130-4446 merging system two nuclei, one tail 2.8 (4.3) - SB a -

21504-0628 merger one nucleus, one tail <1.7 (2.3) - a

22491-1808 merging system two nuclei (in K), two tails 1.6 (2.1) - SB b,h -

23128-5919 merging system two nuclei, two tails 4.9 (3.9) 42 SB = SII = LI a,i SB

23230-6926 complete merger elongated nucleus <0.8 (1.4) LI = SB a {2.4 (4.1)}

23389-6139 close interacting system bright nucleus, two tails 5.8 (8.9) - SII a

 

  
Figure 3: R band images of the Southern Ultraluminous Infrared Galaxies. To the left: greyscale image of the field around the system. The tickmarks are separated by 15. The vertical bar corresponds to 50 kpc. To the right: contour map of the central region. The tickmarks are separated by 5. The vertical bar corresponds to 5 kpc. In all images, North is up and East left

             
Figure 3: continued

  
Figure 4: Calibrated K band contour maps of the Southern Ultraluminous Infrared Galaxies. North is up and East left. The tickmarks are separated by 5. The vertical bar corresponds to 5 kpc. The lower contour is 18.5 mag/ . The step is 0.5 mag/

  
Figure 5: Optical spectra of the Southern Ultraluminous Infrared Galaxies. To the left: low resolution spectra, to the right: high resolution red spectra. For IRAS 00199-7426, IRAS 09061-1248, IRAS 09111-1007 and IRAS 15462-0450, a close up of the LR spectrum in the blue, near the line or in the red, near the line, is presented instead of the HR spectrum. The units are

 >    
Figure 5: continued

  
Figure 6: Diagnostic diagrams for spectral classification (Veilleux & Osterbrock 1987). The line ratios have been corrected for galactic and interstellar absorption