staff astronomers and skillful night 2 4 6 8 10 assistants on La Silla. 1.4 I I II I- References 1.2 I- Greenstein, J. L., 1974, Astron. J. 79, 964. C> I • Kennicutt, R.C., 1984, Astrophys. J. 277, I- 361. Koester, D., 1982, The Messenger28, 25. 1.0 I- / Koester, D., Reimers, 0.,1981, Astron. Astro­ / . phys. 99, L8 (I). Koester, 0., Reimers, 0., 1985, Astron. Astro­ /P phys. 153, 260 (111). 0.8 I- Koester, 0., Reimers, 0., 1989, Astron. Astro­ / phys. LeIters, in prep. (VI). I- 8 Reimers, 0.,1975, Mem. Soc. Roy. Sci. Liege + x+ o 8,369. 0.6 I- Reimers, 0., 1987, in Circumstellar Matter, I- lAU Symp. 122,307. Reimers, D., Koester, 0., 1982, Astron. Astro­ 0.4 I- - phys. 116, 341 (11). Reimers, 0., Koester, D., 1988, Astron. Astro­ - phys. 202, 77 (IV). Reimers, 0., Koester, 0., 1989, Astron. Astro­ 0.2 I- - phys. M. - Romanishin, W., Angel, J. R. P., 1980, Astro­ 0.1 I- phys. J. 235, 992. I I I I III II I II Tammann, G.A., 1974, in Supernovae and 2 4 6 8 Supernova Remnants (C. B. Cosmovici, M ed.) D. Reidel, p. 155. I v.d. Heuvel, E.P.J., 1975, Astrophys. J. 196, Figure 3: Initial-final mass relation for intermediate-mass stars according to cluster white L 121. dwarfs identified in the course of this programme. Symbols: 0 NGC 2516, + NGC 2287, Weidemann, V., 1987, Astron. Astrophys. x NGC 3532, 0 NGC 2168, 0 NGC 2451, L'I NGC 6405, P Pleiades. The broken line is the 188,74. relation adopted by Weidemann (1987). New Results About SBO Galaxies o. BEITONI, Osservatorio Astronomico di Padova, Italy, and G. GALLEITA, Oipartimento di Astronomia, Universita di Padova, Italy We discuss here the preliminary re­ tics, stellar motions were in the past with good hope of progressing toward sults of a long term project on kinema­ very little studied. A systematic attempt its complete understanding. In recent tics and photometry of SBO galaxies to analyse the kinematics of SBOs (Kor­ years, therefore, new data on stellar begun at ESO in 1983 and not yet fully mendy 1982, 1983) was never com­ kinematics have become available for completed. Beginning this study, we pleted and practically only one galaxy, eight more SBOs (Galletta 1987, Bettoni were particularly interested in analysing NGC 936 (Kormendy 1983, 1984), was and Galletta 1988, Bettoni et al. 1988, the mark of triaxiality that the bar in­ studied in detail (photometry, stellar ve­ Jarvis et al. 1988, Bettoni 1988). The duces in otherwise symmetrical galax­ locity field and velocity dispersion field) observational techniques used in our ies, by perturbing and stretching out the before 1987. Similar projects at other observations reflect the improvement of stellar orbits. But we did not imagine observatories followed the same ESO instrumentation in these years: that, progressing in this almost unex­ course, with observations never com­ starting with the 3.6-m telescope with plored land, so many new and not yet pleted or results never published. Prob­ the Boiler & Chivens spectrograph and fully explained features would be dis­ able reasons for this were the difficulty the 3-stage EMI image tube, the obser­ covered. Now, we feel it would be inter­ of supporting for many years a project vations continued at the ESO-MPI esting to resume here before the com­ requiring many observing nights against 2.2-m telescope with RCA CCDs when pletion of the search the main results so the idea that in the melting pot of billions these detectors became available. Par­ far obtained. of stars moving within the bar it should allel to this study, the inner photometry be impossible to distinguish between of the selected galaxies has been per­ "families" of orbits and, last but not formed using the ESO-Danish 1.52-m 1. A Bit of History least, against the occasional misunder­ telescope. SBO galaxies are good candidates for standing of some (too human) time this study because of the low, but not commissions. But with some vi­ 2. Observations and negligible, quantity of gas and dust pre­ cissitudes and a little bit of luck, obser­ Data Reduction sent in them. But despite the large vations of SB Os continued at ESO tele­ number of theoretical models of bars, scopes, demonstrating that we can look Our sampie includes 15 SB 0 galaxies and the several works on gas kinema- inside the stellar and gas kinematics brighter than the 12 th magnitude and 51 .' produce the stellar velocity and velocity plane. The second case is represented dispersion curves. The emission lines by NGC 2217, a galaxy with almost eventually present have been interpo­ ,[ 0 111 ] Mg round disk isophotes where gas and lated by fitting gaussian profiles, obtain­ stars again exhibit opposite motions, { t 11 ing the gas velocity curve and the equi­ circulating around the bar major axis valent velocity dispersion agas = FWHMI with velocities lower than in the case of 2.53. NGC 4546, but not negligible (Fig. 1). Li The photometric analysis has been In these galaxies the presence of re­ performed on frames recorded in band trograde motions should be interpreted V, land at wavelengths around Ha on as arecent acquisition from outside, bar minor axis. the 1.5-m Danish telescope, with expo­ lacking reasonable mechanisms which sure times ranging from 10 to 30 allow such a clear decoupling between ... .. minutes. They have been reduced with angular momenta of gas and stars hav­ the standard ESO-IHAP procedures. ing the same origin. They fit in the wider The photometric zero point of V band frame of SOs with recent interaction, like ~.'" has been obtained using the mag­ the polar ring galaxies (Schweizer et al. \: nitudes reported by Longo and de Vau­ 1983) and confirm the idea that the gas couleurs (1983), while the isophote in­ in SO galaxies has an external origin, as bar~. terpolation has been performed using suggested for the HI by Wardie and the INMP programmes (Barbon et al. Knapp (1986). .\: 1975). Oifferences between gas and star .. kinematics could enhance particular " NGC?~17 3, Results types of orbits. For instance, in the case of NGC 2217 the peculiarities observed Figura 1: The almost face-on SBO NGC 2217 The main properties of the SB 0 galax­ could be explained if the gas moved on (bottom), and its spectrum along the bar's ies observed until now are resumed in orbits belonging to the families of minor axis (top) showing the opposite tift of Table I, where in addition to the galaxies anomalous orbits (X-tube, see Van Alba­ emission and absorption lines. This is the present in our sampie we added NGC da et al. 1982), which appear retrograde second case of counterrotation between gas and stars found in SB0, after NGC 4546 936 (Kormendy 1983, 1984) and the four when seen from the galaxy pole. This is (Gal/etta 1986). galaxies studied by Jarvis et al. (1988). actually the orientation at wh ich, in an We could resume the more interesting almost face-on galaxy such as NGC findings: 2217, we observe the triaxial ellipsoid represented by its bar. These orbits visible for a whole night in the allotted were originally invoked (Van Albada et 3.1 Velocity fjelds observing period. We selected these al. 1982) to explain the motions ob­ galaxies in an effort to have systems Two galaxies were found where gas served in the class of elliptical galaxies with all possible orientations of the bar, and stars rotate with similar but oppo­ with minor axis dust lanes (Bertola and from side-on to end-on, and with all site streams. This is one of the more Galletta 1978) and represent a typical possible inclinations of the galaxy remarkable features found, and fully un­ case where a single family of orbits disk, from edge-on (i = 90°) to face-on expected, which induces some interest­ should be discriminated from the heap (i = 0°). Among these, 10 systems have ing reflections on the nature of the gas in of galactic orbits, as discussed in the al ready been observed in the previous SO galaxies. Observing NGC 4546, an introduction. runs at La Silla and 7 of these have been apparently normal edge-on SBO, we de­ Another family of orbits that should be fully reduced. tected the presence in the same spec­ disentangled from the mass of the A number (from 4 to 7) of long slit trum of emission and absorption lines others, in the very special case of NGC spectra at different P. A. were taken for tilted because of the rotation but in 4546, is that of the retrograde Z-tube each galaxy, with exposure times rang­ opposite way (Galletta 1986, 1987). The (Contopoulos and Papayannopoulos ing from 60 to 120 minutes, in order to amplitude of the observed motions be­ 1980, Heisler et al. 1982, Teuben and map as much as possible the velocity tween gas and stars is of the order of Sanders 1985). These orbits within the field. The spectral region observed at 400 km S-1 along the apparent major bar are elongated parallel to the bar the 3.6-m telescope ranged from 3500 axis. This gas lies in a - 5 kpc wide disk intermediate axis, a direction perpen­ to 4500 A, including Ca 11 Hand K, not yet relaxed on the main galaxy dicular to the most part of the innermost G-band and the eventually present )..)., 3727-29 [Oll] doublet. The spectral region selected at the 2.2-m ranged from 4800 to 5800 A, due to the different 200 spectral response of the RCA CCDs 150 adopted, and includes Mg I, Fe and 0 ~ bar major axis many other bands.