analysis of these data will be presented In the context of further optical obser- Lund, G., 1986, OPTOPUS - ESO Operating elsewhere (Bardelli et d., in prepara- vations, our next run at the 3.6-m €SO Manual No. 6. tion). On a qualitative basis, we can here telescope will be In February 1993, In Lynch-Bell D., FW, S.M., Buweln, D., conclude that Figures 1 and 3 suggest this run we will extend the coverage of Oavles, R.L, Wler, A., Terlevlch, RJ., 926, that the massive cluster A3558 could be the core of the SSC and we will observe and Wegner, G., 1988, &.J. 19. Mathewson, D.S., Ford, V.L, and Buchhorn, the A352gA3530-A3532 structure, in accreting from its nearby clus- M., 1992, &J. fi&t.) B89, L5. m; probably, this is the beginning of a addition to the observation of the field Lynden-Bell., D., Lahav, O., and Burstein, O., merging process. Further data #I(A3562). These data will allow an 1989, M.N.R.A.S. 241,325 abut these clusters will enable us to estimate of the mass of these clusters. Raychaudhury, S., 1989, #at. 542,251. calculate th~masses d A3558 and In order to study the mass distribution Raychaudhury, S, Fabian, A.C., Edge, AC., A3562, in order to estimate the time of the whole complex and to estimate Jones, C., and Fman, W., 1R1, scale of this merging. the overdensity of galaxies outside clus- M.N.R.A.S. 248, 101. ters, we are also planning to map the Scaramella, R., BaiesI-PllfasMni, G., Chlnca- whole SSC with a regular grid of MEFOS mi, G., Vettdanl, Q., and Zamoranl, G., 4. Future Mbrk 1989, lVat 538, 562. fietds, observing all galaxies wlth Scaramella, R., Bleak-Pllhsasttlni, G., &Inca- A3558 is the richest AOO cluster (the 17< bj48. only one with richness class 4) and Is rini, G., Wolani, G., and Bmorani, G., placed in the core of the SSC; more- 1991, in Wge-Scate Molls (Rio %rk- shop 1989), Lathem, D.W. e da Gosta, L over, it is probably attracting Its References (eds.), A.S.P. &I. &t 15,13. surrounding clusters. For this reason it Allen, LA., Nods, R.P. StdepSrnith, t, hpley, H., 1430, Hamrd Obs. Bull. 874,9. is important to determine Its mass and Meadows, MS., and Roche, P.E, 1990, Tully, B.R,, Scamnella, R., Vettdanl, G., and Rs dynamical state. For this purpose. we Nat* 343,45. Zamoranl, G., 1992, Ap.J. SBB, 9. have observed It in the X-ray wavelength Dresslet, A,, 1988, Ap. J. 529, 519. Vettolanl, G., Chincarlni, G., Scarawlla, R, with the ROSAT satellite. flgure 4 Is the Edge, A.C., Stewart, Q.C., fabjan, AC., and and Zarnorani, G., 1000, RJ. 99, 1709. image of this cluster obtained with the Amaud, K.A., 1990, M.N.R.A.S. 245, 5%. Willick, J.K., 1990, &.J. (Letletl)351,L5. PSPC camera, in the range 0.1-2.4 Faber, S.M., and Burstein, D., f 988, In Large- Yentis, DJ., Cruddam, R.G., Gmky, H., Key with an exposure time of - 30,000 Sad6 Motlons In the Universe, proc. of the Stuart, B.V., Wlin, J.F., MacGilllvray, He%, ds. PontKlcal Academic of Science Study and ColUns, C.A., 1W2,in Digtiz&Optrm/ Similar observations for the Week r21, V.C. Rubin and G.U Coyne Sky Surveys, H.T. MacGllllvray and EB. cluster A3528 (the cenbal cluster of the eds., Princeton UnImlty, Rlnceton, p. Thomaan eds., Kluwer Academic Pub- concentration A3528-14353GA3532, 115. Ilshers, The Netherlands, p. 87. see Zucca et al., 1893) are scheduled for Lahav, O., Edge, kc., Fabian, kc.,and Put- Zuaa, E., Zamwani, G., Scaramella, R., and the next ROSAT observing period ney, A., 1889, M.N.RA.S. 238,881. Vetiolani, G., 1993, &.J. In press.

HIGH-RESOLUTION IMAGING WITH THE NTT: The Starburst NGC 1808 B. KORIBALSKI, Max- Pianck-lnstitu t fur Radioastronomie, Bonn, Germany R. -J. DE~TMAR', Radioastronomisches Institut der Universitat Bonn, Germany

An additional peculiarity of this com- gas very near to the centre which has plex central region was noted in 1968 by been revealed using HI absorption me&- NGC 1808 is a beautiful Burbidge & Burbidge. They found that surements against the extended radio located in the southern sky at a distance NGC 1808 "contains an unuSwl amount continuum emission (Koribalski et al. of more than 10 Mpc. The peculiarity of of dust [in the disk] and some curious 1992b). its nudear region has first been men- dust lanes which look almost radial h 7116 far-infrared (FIR) luminosity of tioned by Morgan (1958) who identified form". These prominent dust filaments NGC 1808 is with .= 2 101° Lg quite numerous, extremely brilliant, smaIl which seem to emerge from the nuclear high, similar to NGC 253 and M 82. nuclei in the central region which he region are best seen on optical short Here, we want to present high-resolu- called "hot spots". A real-colwr image exposures of NGC 1808, e.g., those giv- tion Ha observations of NGC 1808 of this most interesting and unusual en by Laustsen et al. (1987) or Tarenghi which have hen klndly made available central region has been presented in (1990) In a previous issue of fhe by Sandro D'Odorico from ESO (thanks The Messenger by VBron-Cetty & Vbron Messenger. Whereas in 1970 Arp & Ber- a lotl). These new data may very well (1983). This image nicely demonstrates tola already speculated 'Yhat these help answering the question how the the presence of several very blue 'hot lanes represent the passage of compact various phenomena observed in NGC spots", corresponding to bright H I1 re- bodies outwards from the nucleus", we 1808 are related to each other, gions, and of 3 reddish nucleus which now have observational evidence that shows spectroscopic evidence for the tbey are indeed connected with the out- presence of Seyfert activity (Vdron-Cet- flow of neutral and ionized gas into the ty & VBmn 1985). halo of NGC 1808 (Koribalski et at. Over the last couple of years the - ' Fresent addrem Space T&@wpe Sclence Insti- 1992a, Phillips 1992). Also new is the burst galaxy NGC 1808 has been ob- lute', Baltrrnwe, MD. USA ('afflllatd with ESA). dlsmvery of a fast rotating torus of cold served in detail with the Vev Large F~guis1. DWayd /lee d& Ule rlu~hwiwwd a1 Ule sldihsl g&xy NGC ,-. ,,Jot# rs to the top and easl fo the /&J (4 The Hu+N/lJ emission at A 6670 A Numerous 'hot spots" (= WbtHI1 WmsI sem to be dWWalong a rlw of dhRs8". 'fhe nuclew at pcasItion @,OJ, whAch Is 8iightly offsei from ttre rlng centre, shows sbm of nudear W'uity! 0 7M I-Brmd mtinwm ernlssbn at 1.9137 4. Dus to the erlM rd~ffveintens& of the Wbtcodtam~thm, Uleir distribution apw8m quite ~~t compand with the &ow Image. wtypeculk Is the "hot spot" 5* SE of ttm nuetws, which Is not very pmminenl in the continuum irn- bul hm about the s8m brlgMm as the nucleus h the Ha+flIIJ Urn mission.

Array (VIA) in the radio continuum and with a ridge of neutral hydrogen (HI) gas tion angle of PA = 145" (roughly along HI X 21-em mission line (Koribalski et and continuum emission In the disk. the major axis) we are able to get some al. 1992a, b) In order to study the overall insight into the central gas kinematics. gas dynamics in the disk and a possible 3.1. The 'Rot spot" region figure 2a displays the "hot spot" region large-scale flow of matter from the disk as in Figure la but now the x-axis Is Into the halo, as suggested by the struc- In Ftgure 1 we show the colour coded oriented along the slit (y .= 0). The other ture of tb dust filaments in the nuclear intensity distribution in the central re- plots of Figure 2 show the fit parameters region of this galaxy. A vety valuable gion for emission lines and stellar con- of the Ha tine along the slit: (b) the addition to these data sets were the tinuum. Rgure la displays the llght dL- relative intensity profile, (c) the positlon- abovementioned optical obsmations tribution of the Ha+[MIIl emission lines. velocity diagram, and (d) the Ine width obtained whh the 3.5-m NlT during The pure line emission has been ob- FWHM, not corrected for instrumental commissioning time for EMMI, the ESO tahed by subtracting the scald I-band broadening. The dotted line in Figure 2b Multi Mode Instrument, in October 1991 continuum image (Flg. lb) from the is just for comparison and shows the (for a description of EMMl see Th narrow-band Ha-image. One can distin- I-band emission on an enhanced scale. M8ssenp 6l, p. 51). Both long-slit guish a number of bright components, The rotation curve obtained from this spectroscopy In the red near Ha and the so-called "hot spots", which are dls- spectrum (Fig. 2c; not mctedfor the direct imaging (Ha- and I-filter) were tributed over an area of about 1 kpc inclination) reveals a systemic velocity carried out. The observing parametets (20"). They seem to lie along a "mlni- of about u, = 985 km s-' at the location are summarized in Table 1. The data spiral" or nuclear ring of radius 400 pc of the nucleus. tt is very symmetric in the reduction was carried out with the and inclination Mu(== the disk Inclina- inner f4"6" where radial velocities of M1W software package. tion). Its centre is slightly offset from the u,k 115 km s-' are measured. Further nucleus (= posltlon 0,O). The contlnuum out we derive extrema of +130 km s-' image (Fig. I b) reveals a sllghtly differ- and -180 km s-' at about 10 NW and ent structure, with the nucleus being 12" SE from the nucleus, respectively. In this prellminaty re* we wlll con- much more prominent (see also Fig. 2b, The two "hot spots" on the SE side of centrate on two peculiar features In t he dotted line) than in the Ha Image. the continuum On Fig. 2b the two peaks distribution of Ha emission which might The most accurate position of the to the left) cause an additional compo- be of interest for understandingthe rela- nucleus, which Is identical wlth the nent which is responsible for the tion between sta&urst nuclel and the brightest component at several asymmetry of the rotation curve at this kinematics of the host galaxy on larger wavelengths, has been determined at slit position. The rotation curves ob- scales. The Ha-image obtained with h 6 cm with a, 8 (1950) = 05%Om58f56, tahed by Burbjdge & Burbidge (1968) EMMl shows -37'36'36Y3 (Salkia et al. 1990). The and VBron-Cetty & Vhn(1985) do not (I) a 'mini-spiral" or nuclear ring de- other compact radio components ob- resolve this inner region. scribing the distrlbutim of 'hot spots" in served at h 6 cm do not correlate wlth The width of the Hu line (Fig. 2d) has the central region of NGC 1808 and any of the "hot spots" and are probably an interesting radial dependence which (2) a linear structure of bright Hlt re- remnants. is directly related to the rotation curve gions on kpe scales. This is correlated With the Ha spectrum taken at a posl- and the nuclear environment. In the W

-10 -6 0 b LO of-nct I-I FIgure 2: (4 the 'hot spat" wion of NGC 1808 8s In Fgm fa but with the x-axis wlented along the SIN (FA = I@) whem the Ha spestrwn was obtatmd. Further diwlayed am 16) the wlatlve Intensity plik of the Ha line misalon (sdid curve) and continuum emissbn (dotted cum), (c) the pwrrpwrrtion-wkdtydiesgresm, and (4the width (WM)of the Ha line.

same range where the rotation cuwe is The alignment of the HI1 reglons from = 6 kpc at a posltlon angle of PA = symmetric, the width of the Ha line -60" SE to +60" NW of the-nucleus and 155' which Is about 20" offset from starts to increase from 100 km s-I to the correspondence of this linear struc- the PA of the dbk. The ratio of bar to unusually large values, reaching about ture with a ridge in the HI distribution as disk length ts roughly = 0.3. 180 krn s-I near the nucleus, and slightly wet1 as the dongatition of the radio con- Beyond f3 kpc the H It regions bend h lass at the nucleus -If. The enormous tinuum distribution in the sams direction opposite dlmctions fdlowing the galac- llne width at the positlon of the nucleus strongly suggests the presence of a tic rotation, whlch Is also observed In as well as Uw obmed asymmetric line ba~The linear dimension of the bar is the distribution of neutral hydrogen gas. profiies and increasing [NII]Ma ratios (which will be discussed elsewhem) are hinting at nuclear actkrily as had already been suggested by Vdron-Cetty & V&on fable 1. Chwing PamW (1985). T@kmpe 3.5411 New Technology Telescope Omrver S. D'Worico (BO) Date 1880, Octokr 23/24 Instrument ESO MUM Mode Instrument 3.2. 7he bar 'CLpe of CCD chip 1024' THX Thompson We wlll now concentrate on the disk Obsewlng mode: of NGC 1808 which has an optical ex- lw LWitmscopy Sllt-length, sllt-wldth, PA B', 12,146" tent of 7!224!1 dong PA - 133" h5, Grating, dispersion a%. 28AImm de VWCOUIM~ et el. ~78).me direct ~eso~ution iaA a 55 km s-I image of NGC 1808 obtained in Ute red Integration tlme Ha-swm: 30 mtn channd of EMMI Is already displayed h IB) Dkthwhhg the ESO Annual Report 1990 (p. 56-57). Field dlmenslons 7:5x7:5 (- 1 OT44pix Our Figure 3 shows the Ha+[NII] line Rlters (number, centre, width) #598 (Ha), 6570 A 721 mission from the dislc of NGC 1808 #%%(I), 0137 A, 194 A which is mainly confined to a thin 11na of Intmtlon time Ha-Image: 5 and iO mln numerous bright H ll regions and meals I-Image: 10 min Reso1utlon = 3 pktels only a small amwnt of diffuse emission.