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The detection of star formation driven gaseous outflows using the Halpha narrow band line imaging techniques is a viable method to trace the distribution of the warm ionized medium in external galaxies on a global scale. Many of the actively star-forming galaxies show similar, yet different, morphologies as the starburst galaxies.

We have presented the individual results for the Halpha survey galaxies. From the 74 investigated edge-on spirals we have detected eDIG in 30 galaxies, that is 40.5%. We can therefore conclude, that the presence of eDIG in halos of galaxies is not a unique case for only a few galaxies, rather it is found to be ubiquitous in galaxies, which exceed a certain level of SFR per unit area, or even at a fainter threshold in combination with enhanced dust temperatures Rossa & Dettmar (2003). However, it can thus also be concluded that eDIG is not a common feature among all late-type spiral galaxies, as many of them do not show eDIG (at the level of the observed sensitivities). The presence of eDIG is depending on the SF activity on both local and global scales.

The morphology of eDIG shows a wide variety ranging from individual plumes, and filaments in galaxies with mediocre SF activity, to pervasive layers in the actively SF galaxies. A few of our eDIG detected targets bear a more or less intense layer of extended emission with typical extraplanar distances of 1.5-2 kpc. Individual filaments of some galaxies (e.g., NGC4388, NGC5775) even reach distances of up to ~ 6 kpc. In the case of NGC4700 a good correlation between extended Halpha emission and radio continuum (radio halo) is found, which further strengthens the disk-halo interaction scenario.

Table 5. DIG morphology of the survey galaxies

Galaxy DIG morph. a vertical extent radial extent Notes
    | z|[kpc] RSF[kpc]  

NGC24 d, n 0.68 3.09 not perfectly inclined
NGC100 n 0.63 5.82 HII regions in the disk
UGC260 eh2, f, hf, pec 2.00 7.14 pec = tidal debris?, galaxy?
ESO540-16 d 0.73 7.88 strong asymmetry of planar DIG
MCG-2-3-16 a, n 0.43 2.67 disturbed disk
NGC360 d 0.59 11.71  
NGC669 n   28.33  
UGC1281 n 0.42 3.34 HII regions not aligned
NGC891 ee, eh2, f, hb 2.15 9.85 eDIG asymmetry (north-south)
UGC2082 d, n 0.44 4.68  
IC1862 d, n   47.17 slightly warped disk
NGC1247 d, pa   36.10  
ESO117-19 d   27.89  
IC2058 n 0.48 7.66  
ESO362-11 hf 2.47 7.80  
ESO121-6 hf 1.42 7.88  
NGC2188 ee, eh2, f, pl 1.35 6.18  
ESO209-9 hb, pa, pl 1.57 12.60 + galactic emission
UGC4559 n 1.00 6.29 disk em. restr. near nucleus
NGC2654 d, n 1.18 7.18 clustered HII regions
NGC2683 d, n 0.87 2.63 strong disk emission
NGC3003 d, n   9.35 galaxy not perfectly edge-on
NGC3221 ee, hf 3.82 35.27  
NGC3365 d, n 1.00 2.23 strong local disk emission
NGC3501 n 0.85 7.19 disk HII regions not aligned
NGC3600 ee 1.24 4.20 nuclear outflow?, warped disk
NGC3628 ee, eh2, f 3.13   prominent nuclear outflow
NGC3877 ee, f, pl 1.38 12.00 clustered DIG emission
NGC3936 n   11.46  
ESO379-6 ee, pl 2.08 25.23  
NGC4206 d, pa 1.22 8.02  
NGC4216 d, n   11.48 strong Halpha bulge emission
NGC4235 ee, hf 2.50 4.58 dust obscur. near nucleus
NGC4256 d, n   13.17 planar DIG asymmetry
NGC4388 f, hf, pa 5.92 15.50 prominent halo patch
NGC4700 hb, f, pa 2.18 12.50 one filament z approx 3kpc
NGC4945 f, hb, pl 5.28 geq22.42 outflow cone
NGC5290 ee, f, hb 4.00 13.00 nucl. outflow, starburst?
NGC5297 d, n   16.00 not perfectly edge-on
NGC5775 hb, f, pl 5.38 21.44 prominent filaments
ESO274-1 ee, f 0.75   strong local eDIG
NGC5965 d, n   19.78  
NGC6722 n   42.86 warped disk
IC4837A d   13.57 strong local DIG
ESO142-19 n     prominent dust lane
IC4872 n 0.71 3.33  
NGC6875A ee?, pa 2.75 12.00 not perfectly edge-on
MCG-1-53-12 n 1.40 10.80  
IC5052 a, ee, hb, pl 1.24 9.90 DIG distr. asymmetrically
IC5071 d   20.85 clustered DIG emission
IC5096 n 1.00 19.61 strong bulge emission
NGC7064 ee, hf, pl 0.92 7.20 disk bi-sected
NGC7090 a, ee, f, hf 1.78 8.39 strong local emission
UGC11841 n     gal. barely vis. in Halpha
NGC7184 d, n   20.44 strong emission in annulus
IC5171 d   10.19 strong planar DIG
IC5176 ee, hf 2.35 10.22  
NGC7339 n 0.36 2.32 disk HII regions not aligned
NGC7361 d, n   9.49 strong disk emission
NGC7412A a, n 0.47 4.77 bright disk HII regions
UGC12281 n 1.36 20.00  
NGC7462 f, hf, pl 1.76 10.81 slight asymmetry
UGC12423 n     gal. barely vis. in Halpha
NGC7640 d, n   7.11 strong planar DIG
ESO240-11 n   29.93 slight disk asymmetry

a a=arc(s), d=disk emission (only planar DIG), ee=extended emission (locally), eh2=extraplanar HII region(s), f=filament(s), hb=bright halo, hf=faint halo, n=no (e)DIG, pa=patch(es), pec=peculiar, pl=plume(s)

Figure 21

Figure 21. Distribution of the observed 74 galaxies of the Halpha survey on the celestial sphere in Aitoff projection. The center position is 0,0 in R.A., Dec.

Acknowledgements. It is our sincere pleasure to express our thanks to Dr. Francisco Prada for carrying out some of the observations at Calar Alto in an emergency case. We owe special thanks to Dr. Michael Dahlem for providing us with the data on NGC 3936, kindly observed by Dr. Eva Grebel. We would also like to thank the anonymous referee for his/her helpful comments. The authors would like to thank Deutsches Zentrum für Luft - und Raumfahrt (DLR) for financial support of this research project through grant 50 OR 9707. Additional travel support for the Calar Alto observing runs is acknowledged from the DFG through various grants. This research has made extensive use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The Southern Halpha Sky Survey Atlas (SHASSA) is supported by the National Science Foundation.

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