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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    A photometric study of the double ring structure of NGC 4736 (1989)
    Springer
    Astrophysics and space science 156 (1989), S. 301-313 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this study we present photometric results for the galaxy NGC 4736: infrared and visible profiles. After a careful correction for the extinction within the galaxy based on measured neutral gas surface densities, we interpret the profiles in the individual bands and in colour indices, in terms of the radial distribution of stellar populations. We pick out the behaviour of the two rings, an inner ring some 40–50 arc sec from the nucleus, and an outer ring some 300 arc sec away. We show how the photometry allows us to make tentative physical inferences about the nature of these two structures, showing that the inner ring is connected with an outflow of gas observed via itsHii regions, and is probably the result of an axisymmetric starburst, while the outer ring is a site of star formation which appears to be further from the centre than the typical resonant structures associated with a density wave.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646382
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  • 3
    Electronic Resource
    Electronic Resource
    Application of a new evolutionary model for stellar populations to photometric maps of M32 (1989)
    Springer
    Astrophysics and space science 157 (1989), S. 89-101 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have developed a new model of evolutionary synthesis of stellar population, from a working cyclical approximation to a general solution for the mass and time dependence of the ‘birth function’ of stars. The general solution enables us to introduce a functionG(t): the ratio of gas injected into a defined region to that which forms stars in the same time interval, at timet. This function, by relating directly the output of dying stars with the formation of the next generation, allows us to make analytical approximations (in the absence of more accurate numerical information) to the macroscopic evolution of stellar populations in a well-defined zone of a galaxy. The model has been initially applied to 4 zones of the dwarf elliptical M32 (NGC 221) where, usingU, B, V from the literature, and our own photometric maps inJ andK, we obtained the following results: (a) Star formation in the most recent 108 years is lower by a factor 3–4 in a zone 68 arc sec (200 pc) from the nucleus than in the nuclear zone. (b) The metallicity appears to be a little lower in a zone diametrically away from the parent galaxy M31 than in a zone towards M31 at the same galactocentric distance (c) TheM/L ratio is a factor 2 higher at 200 pc from the nucleus towards M31, than in the nuclear zone. (d) A high concentration of mass is evident in the nuclear zone. (e) The estimated age of all the zones is of the same order,≲1.5×1010 yr.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637315
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  • 4
    Electronic Resource
    Electronic Resource
    Taurus observations of the velocity field in the inner zone of NGC 6946 (1989)
    Springer
    Astrophysics and space science 157 (1989), S. 157-163 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have obtained a two-dimensional velocity map in Hα of the inner 4 arc min zone of the Scd starburst galaxy NGC 6946 using the TAURUS interferometric spectrometer on the 2.5 m Isaac Newton Telescope. The major axis rotation curve is a cleen kinematic superposition of a central 1 kpc sphere with solid body rotation and a disc with density falling inversely with radius. We show clear evidence of symmetrical radial motions in the plane of the galaxy with velocity up to 100 km s−1 along axes offset from the major axis by up to ±30°. Along the bar at position angle 160° we see outflow out to −2 kpc and significant inflow beyond this radius. These velocity fields give clues to the nature of the starburst process within the central 1 kpc zone of the galaxy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637323
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    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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  • 9
    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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  • 10
    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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