[en] Supernova-driven gas loss during the early evolution of elliptical galaxies is considered as a possible explanation for the correlations among the observed chemical and structural properties of these systems. Mass loss from systems with a chemically homogeneous interstellar medium does not work. It is pointed out that supernova-driven winds are in fact metal-enhanced with respect to the star-forming gas because the metal production of any supernova that drives the wind is directly flushed out of the galaxy. The fraction of the total metal production lost in the wind is thus at least as large as the fraction epsilon(z) of supernovae that power the wind, independent of the total mass loss. As a corollary, the yield of heavy elements that are recycled in the galaxy is reduced by a factor 1 - epsilon(z). Metal-enhanced galactic winds, which can carry away a large fraction of the metal production in spite of a moderate total mass loss, offer a promising explanation for the low metallicities of dwarf elliptical galaxies. 62 references

[en] The generation of galactic winds from star-forming galaxies is investigated. It is shown that the large supernova rates believed to have occurred during the early evolution of elliptical galaxies result in a chemically inhomogeneous two-phase interstellar medium consisting of cool clouds embedded in a hot low-density matrix that occupies most of space. The energy and heavy-element production of supernovae exploding directly in the hot matrix can generate a metal-enhanced galactic wind. Supernova-driven mass loss is found to depend critically on the supernova rate in dwarf galaxies and, in the case of giant ellipticals, on the depth of the potential well. The latter fact suggests the possibility that the transition from giant to dwarf ellipticals is due to the transition from partial to total winds. 46 references

[en] The dynamical evolution of the solar neighbourhood is described by an accretion model in which the gas accretion rate decays exponentially with time. Stars form at a rate proportional to the local gas volume density and their velocity dispersion is increased after birth by star-cloud collisions. The present mass density distribution of stars and of gas perpendicular to the galactic plane and the observed increase of stellar velocity dispersion with age are reproduced for an e-folding time of 3x10⁹ y of the gas accretion rate and a characteristic star formation time scale of 2.8x10⁹ y. (Auth.)

[en] The optical and infrared luminosity functions are determined for a 60 micron flux-limited sample of 68 IRAS galaxies covering a total area of 150 deg sq. The IR function is in good agreement with that obtained by other authors. The shape of the optical luminosity function is similar to that of optically selected galaxy samples. The integrated light of most objects in the sample have (NII) to H alpha line flux ratios characteristic of HII-region galaxies. In the absolute magnitude range M sub J = -18, -22 about 14% of late-type galaxies are IRAS galaxies. The apparent companionship frequency is about twice as large as that for a comparable sample of non-IRAS late-type galaxies

[en] Optical and radio data that reveal the peculiar morphologies of four IRAS galaxies are discussed. NGC 1620 is shown to have an off-center arclike structure of 3 kpc radius that may be the largest supernova-blown bubble known. UGC 2982 is an ongoing merger of two gas-rich galaxies. It is shown that the UGC 3004/3005 pair is not interacting despite the proximity of its components. UGC 3004 is a regular barred spiral galaxy. A second nucleus in the edge-on system UGC 3005 suggests a recent merger. Finally, IRAS 23385 + 0300 is one of the most infrared-luminous galaxies known. 23 refs

[en] The authors present charge coupled device (CCD) imaging results of their sample of Infrared Astronomy Satellite (IRAS) galaxies with spectral energy distributions peaking at 60 microns (Vader et al 1988). The results support the author's suggestion that the activity in 60 micron peaking galaxies is centrally concentrated, and represents an early stage of dust-embedded nuclear activity. This activity is probably triggered by a recent interaction/merger event as indicated by their peculiar optical morphologies. The authors propose that 60 micron peakers are the precursors of SO's in the case of amorphous systems, and ellipticals in the case of interacting galaxies

[en] We have obtained B and R CCD and H I observations of the Virgo dwarf galaxy IC 3475. The galaxy is remarkable for its very large diameter (approx.10 kpc for a Virgo distance modulus of 31) and is comparable in size to the large dwarfs discussed by Sandage and Binggeli. Its light profile is best fitted by an exponential law, characteristic of a dwarf Magellanic irregular galaxy. It possesses a central bar with many knots and inclusions concentrated toward the center of the galaxy. These knots and inclusions have the same color (B-Rapprox.1.5) as the rest of the galaxy and are best explained as intermediate-age (1--7 x 10⁹ yr) star clusters such as those found in the Magellanic Clouds. Despite possessing the photometric structure of a dwarf Magellanic irregular galaxy, IC 3475 contains less than 5.3 x 10⁶ M/sub sun/ of neutral hydrogen. Its hydrogen mass to blue light ratio is less than 0.01, approx.60 times less than the mean value observed for dwarf Magellanic irregulars. It is most likely that IC 3475, which is located near the core of the Virgo cluster, is a stripped dwarf galaxy. The very large size of the galaxy (its diameter is approx.1.8 times larger than that of ''normal'' dwarfs) appears to rule out evolution of IC 3475 from a normal dwarf irregular or to a normal dwarf elliptical

[en] The distribution of point X-ray sources in the bulge of M31 is compared to that in the bulge of our galaxy, and to the distributions of novae and of the surface brightness in M31. The bulge of M31 seems to contain about four times as many luminous X-ray sources (Lsub(x) > 10³⁷ erg/s) per unit mass as the bulge of our galaxy, independently of whether these sources are located in globular clusters or not. The field bulge X-ray sources (i.e. those apparently not located in globular clusters) and novae closely follow the light distribution in M31, except for a central 'nova hole' with radius approx. equal to2'. The existence of this nova hole excludes capture of neutron stars by field stars in the bulge as a formation mechanism for the field bulge X-ray sources. The distinction between field bulge X-ray sources and globular cluster X-ray sources in M31 is meaningful and appropriate because (i) it is very unlikely that some of the field bulge X-ray sources in M31 are located in optically unidentified globular clusters; (ii) the density of field bulge X-ray sources in M31 is too high to allow their formation in globular clusters which evaporated or were destroyed by dynamical friction during the past 10⁹ years. We show that of the 42 field bulge X-ray sources in M31 located within an ellipse with semi-major and semi-minor axes of 11.5 and 5.5, respectively, at most seven may have originated in evaporated clusters and no more than two in tidally disrupted clusters. We suggest that the field bulge X-ray sources may be the products of the long-term evolution of novae or nova-like binaries. The 'nova hole' in M31 can then be explained as an age effect: the central region of M31 is so old that its novae have evolved beyond the nova stage. (orig.)

[en] During a redshift survey of an infrared complete sample of galaxies recorded by the Infra-Red Astronomical Satellite (IRAS) the authors have identified the IRAS source 00275-2859 as a quasar with a redshift of z=0.28. The object looks stellar on both blue and red photographic plates, with an apparent optical magnitude J=17.1 mag. It is a radio source. Its far infrared luminosity is 1.5 x 10¹² L solar mass, which exceeds both its optical and radio luminosity. (author)

[en] The IRAS Point Source Catalog contains only 60 sources identified as galaxies whose energy distributions peak at 60 μm instead of raising from 60 to 100 μm. The scarcity of these 60 μm peakers prompted a systematic study. The authors' most promising results are that 22% of the 60-μm peakers with available radio data have 6-cm continuum luminosities in the range of 10^6-7 L₀, which places them in between radio-quiet and radio-loud objects, and have relatively warm far-infrared (FIR) colors, which the authors interpret as a sign of youth: the obscuring material responsible for the onset of nuclear activity is still close to the nucleus and therefore fairly warm; whether these presumably young radio sources can be expected to develop into a classical double radio source, like Cen A, is presently being investigated; the authors' sample is roughly evenly divided in early-type (E-S0) and double-nucleus/interacting systems, all of which have strong emission-line spectra and some of which have shells