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  • 1
    Electronic Resource
    Electronic Resource
    Type Ia supernovae observed at La Palma Observatory: Looking for differences within a recent sample (1990)
    Springer
    Astrophysics and space science 169 (1990), S. 275-280 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A sample of recent type Ia supernovae has been observed from La Palma. Spectra of there supernovae were taken at two different phases: around maximum and between one and two months after maximum. We present here our observations and discuss the existence of intrinsic differences within the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00640733
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  • 2
    Electronic Resource
    Electronic Resource
    Efficiency of massive star formation in grand design spirals (1990)
    Springer
    Astrophysics and space science 170 (1990), S. 209-214 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The present study estimates the efficiency ratio for massive star formation between the arms and the interarm discs of three grand design spirals. The estimate is based on Hα mapping observations of theHii regions in the galaxies. We find that this efficiency ratio is ≥10 in the zones between the Lindbalad resonances and the radius which we infer to be co-rotation, dropping to values close to unity at these three resonance raddii. these results point to a dominant influence of resonance structure in stimulating star formation in grand design spirals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652669
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  • 3
    Electronic Resource
    Electronic Resource
    Photometric separation of the bulge and disc components of spirals using CCD imaging (1990)
    Springer
    Astrophysics and space science 170 (1990), S. 225-229 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present high-resolution CCD images of a sample of spiral galaxies, in infrared photometric bands, obtained at the Cassegrain focus of the 1 m Jacobus Kapteyn Telescope, La Palma. A decisive advantage of the linearity in these images is that we can effect a reliable separation of the light from bulge and disc. We describe possible applications of the results to determine the structure of the bulges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652672
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  • 4
    Electronic Resource
    Electronic Resource
    An improved evolutionary model for stellar population applied to NGC 2903 (1990)
    Springer
    Astrophysics and space science 170 (1990), S. 275-282 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We outline the revised physical assumption which have been incorporated into our previously published evolutionary model for stellar population synthesis in galaxies. Applying the present version of the model to well-defined zones on the nucleus and along a spiral arm of NGC 2903 we show that the star formation rate has increased during the lifetime of the galaxy, steadily but only slightly in the arm, and spectacularly in the nucleus, where there is current starburst activity. We also infer that considerable gaseous inflow has occurred in the arm during the lifetime of the disc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652680
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  • 5
    Electronic Resource
    Electronic Resource
    Hii region statistics in spirals (1990)
    Springer
    Astrophysics and space science 170 (1990), S. 297-303 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract From high-resolution maps of the spiral galaxies NGC 3992 and NGC 4321, obtained with the TAURUS camera at the 4.2 m William Herschel Telescope, we have inferred: (a) The total number of separately identifiableHii regions in their discs classified according to their membership of a spiral arm or the interarm disc, (b) the radial distribution ofHii regions, (c) the frequency distribution of diameters ofHii regions, (d) the luminosity function; each parameter rpesented separately for theHii regions in the arms and in the interarm region, showing the differences between them. From these observations we have also derived the radial dependence of the product of the filling factor, the electron density, and the ionized hydrogen density, which does not appear to change between arm and interarm disc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652683
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  • 6
    Electronic Resource
    Electronic Resource
    Departures from axial symmetry, and starburst activity, in the bulge of NGC 4736 (1990)
    Springer
    Astrophysics and space science 170 (1990), S. 305-310 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Evidence for circumnuclear starbursts in spiral galaxies can take the form of a blue excess near the nucleus, but more frequently (because of dust extinction)Hi or radio continuum emission. Such bursts are quite common, even in objects with no interacting companions. One consequence of a burst is to sweep gas outwards from the inner zone, so further bursts (and perhaps the initial one) need to be re-supplied with gas. This can be effectedvia a non-axisymmetric gravitational potential, not necessarily a bar, in the nuclear bulge. Searching for these non-axisymmetric features, we have performed two-dimensional photometry on CCD maps inB, V, R, I, andZ bands, for a set of galaxies which have undergone starburst activity, and we present here a set of results from that photometric programme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652684
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  • 7
    Electronic Resource
    Electronic Resource
    Satellite galaxies as probes of the gravitational potentials of large spirals (1990)
    Springer
    Astrophysics and space science 170 (1990), S. 327-335 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An aspect of the missing mass problem in galaxies, not easy to address, is whether the dynamical mass distribution is spherical or greatly flattened, following the light. Rotation curves of spirals out of the plane of the disc cannot, by definition, be measured. A way around this problem might be to use satellite glaxies orbiting within a few Holmberg radii of their parents. We address here the difficulties implied in using a satellite in this way: to what extent can one solve uniquely for its orbital parameters? A practical set of solutions which can constrain an orbit is derived here using the tidal radius of the satellite to scale the gravitational pull of the parent. Although data of the quality needed exist as yet for very few systems, we show using M31, NGC 128, and NGC 1023 and their respective satellites, how the dynamics of the interactions can be explored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652688
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  • 8
    Electronic Resource
    Electronic Resource
    Spanish Participation in the Millimeter Array (1998)
    Springer
    Astrophysics and space science 263 (1998), S. 381-388 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Spanish participation as an Associate Member in the Millimeter Array (MMA) project - led by the U.S. National Radio Astronomy Observatory (NRAO) - has been recently proposed to the Spanish Science and Technology Bureau (OCYT). This request to the Spanish Government is based on two key factors: (1) The high scientific interest and support of the Spanish scientific community, for whom major new fields of research--inaccessible with other instruments--will become available. (2) An industrial return that will clearly benefit Spanish companies developing cutting-edge technology and providing them with a high international profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002109418430
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for leading spiral arm formation in NGC 7479 (1989)
    Springer
    Astrophysics and space science 156 (1989), S. 199-204 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Azimuthal profiles of the spiral NGC 7479 in theB andI passbands have been analyzed using a subset of the azimuthal parameters proposed by Beckman and Cepa (1989), to look for the presence of shock fronts in the arms, as predicted by the density wave theory. The sign of the skewness parameter, showing that beyond the corotation radius the concave side of the southern arm shows steeper profiles in both colours, is an indicator that the arm studied is a ‘leading’ structure. We also measure a colour gradient in the arm, with theB intensity peak of the profile nearer to the shock front than theI peak. The measured angular shift, when converted to time drift assuming that the bar ends near the corotation radius, is consistent with the drift expected for an ‘ageing’ stellar population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646366
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  • 10
    Electronic Resource
    Electronic Resource
    Differential efficiency of massive star formation in NGC 628 (1989)
    Springer
    Astrophysics and space science 156 (1989), S. 289-293 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The efficiency ratio of massive star formation in the arms of the spiral NGC 628 to that in the interarm region has been determined from the sizes and positions of itsHii regions following the method described in Cepa and Beckman (1989a, b). The variation of this relative star formation efficiency with radius shows a very similar behaviour for each of the three arms of this galaxy with a minimum at 100 arc sec from the centre, which can be identified with the corotation radius distances at which the arms show bifurcations or sudden changes in their pitch angles. This result, together with the higher star formation efficiency in the arms than that in the interarm zones, is evidence supporting the hypothesis that the spiral arms of NGC 628 are driven by a density wave which triggers the star formation according to the spiral density wave theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646380
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