Photographic UBV photometry of NGC 2976, a low-luminosity member of the central M81 group of galaxies, is presented. Young stars in the central disk determine the optical view and the classification of this Sc(pec) galaxy. It is surrounded by a halo of an old pspulation which contains nearly all the mass and half the luminosity of the system. This halo has some properties typical of spheroidal dwarf galaxies: an exponential brightness profile, an ellipticity trend of the isophotes typical of low-mass systems, and mass and luminosity near the upper limit of typical dwarfs. In the central population I disk, star formation proceeds in dense associations scattered irregularly in a broad ringlike region of 1.2 kpc radius just inside the turnover of the rotation curve. This star formation episode may last since some 108a; it is possibly triggered by gas infall from the interstellar cloud generated during encounters between other group members in the central M81 group. A direct triggering by recent encounters is excluded since NGC 2976 is undisturbed in its outer parts. K e y words: galaxies: NGC 2976 --stellar populations -dust A A A subject classification: 157 IntroductionThe population content of galaxies and its development with time has since long attracted considerable attention. T h e distribution (and kinematics) of stars of different age and of different metal content bears valuable information about the history of galaxy evolution. Observed intensity profiles of the old population, trends in the ellipticity of the isophotes, systematic variations of metallicity and colours can be compared with predictions from evolutionary models t o get insight into the past history of the systems (for instance Larson 1975, Larson and Tinsley 1978, Arimoto and Yoshii 1986, 1987, Katz and Gunn 1991. The occurence and the distribution of young stars and their relation to the interstellar gas and dust are indicative of the processes which trigger star formation. Irregularities in the distribution of stars and interstellar matter may be signatures of recent interactions with neighbouring systems. Since every galaxy has its special history determined by environmental and initial conditions, discussion of individual galaxies is of its own value and is supplementary to the observation of selected parameters of a great number of objects for statistical discussion. Our interest in NGC 2976 is twofold. First, this Sc(pec) galaxy (de Vaucouleurs et al. 1976) is a member of the M81/M82 group of galaxies. It contains a large number of young concentrated star forming regions in its inner disk; many of them are conspicuous Ha-regions (Hodge and Kennicut 1983). T w o other members of this group, NGC 3077 and M82, suffered close encounters with M81 during the last 109a (for instance Cottrell 1977, Kilian 1980, Brouillet et al. 1991a. A huge cloud of interstellar matter, now enshrouding these galaxies, was probably generated by these events. A faint extension of the cloud links NGC 2976 t o the central group (Appleton et al. 1981(Appleton e...

Photographic photometric measurements of z arcsec resolution of the central regions of M82 are presented in the three colours U , B, V. The observed light is decomposed into two parts: stellar light and light from the central source scattered by dust. The tariation of the reddening of both components is derived.The dust distribution pattern is different near the spatial centre of M82 and farther out. The equator of the dust complex obscuring the central source is inclined to the overall symmetry plane of M82. The outer dust clouds responsible for the obscuration of the visible stellar light are probably arranged in a spiral-like fashion; the "plane" containing these clouds is strongly warped and disturbed.The light of the bright knots A and C consists to a considerable part of scattered light from the central source nearly behind them. Ha light and scattered continuum light is strongly correlated in M82, pointing to an ionisation of the gas by the source of this continuum in addition to the presence of scattered Ha.Photographische Helligkeitsmessungen des Zentralgebietes von M82 in U , B und V mit einer Auflosung von 2 " werden mitgeteilt. Die gemessene Lichtintensitat wird in die Anteile ,,Sternlicht" und ,,Streulicht der zentralen Quelle" zerlegt. Fiir beide Komponenten wird die Verfarbung abgeleitet.Die Verteilung des Staubes in M82 ist verschieden in den inneren und den PuBeren Gebieten. Der Aquator des mit der zentralen Quelle verbundenen Staubkomplexes ist gegen die auBere Symmetrieebene von M82 geneigt. Die auL3en-liegenden Staubwolken, die fur die Extinktion des sichtbaren Sternlichtes verantwortlich sind, sind vermutlich spiralahnlich angeordnet; die durch diese Wolken definierte ,,Ebene" ist stark verbogen und gestort.Das Licht der hellen zentralen Knoten A und C ist zu einem wesentlichen Teil Streulicht der zentralen Quelle, die versteckt fast hinter ihnen steht. Die Verteilung von Ha-Licht und kontinuierlichem Streulicht ist iiberall in M82 eng korelliert; der Anteil an Ha, der nzcht Streulicht ist, muD deshalb aus Gas stammen, das von der zentralen Quelle ionisiert wurde.

Lichtelektrische und photographische Messungen der Nova Herculis werden mitgeteilt. Die Lichtkurve und der Verlauf der Farbenindizes werden diskutiert, zum Teil unter Einbeziehung fremder MeOreihen. Der durch interstellare Extinktion hervorgerufene Farbexzess der Nova wird zu E B -v = + o"45 f OTIO abgeschatzt.

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