Piet van der Kruit | University of Groningen (original) (raw)
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Papers by Piet van der Kruit
Astrophysics and Space Science Library, 1988
ABSTRACT
Toward a New Millennium in Galaxy Morphology, 2000
Astrophysics and Space Science Library, 1992
In this review I discuss various aspects of the large scale structure and dynamics of spiral gala... more In this review I discuss various aspects of the large scale structure and dynamics of spiral galaxies. It is first pointed out that spirals basically exist of two discrete components, which may indicate that there have been two epochs of star formation. In spite of the different light distributions the two galaxies NGC 891 and 7418 have very similar rotation curves, which argues against maximum disk models and revised gravity.
Astronomy and Astrophysics
Astronomy and Astrophysics
ABSTRACT
We report our latest findings on the volume densities of molecular hydrogen in Giant Molecular Cl... more We report our latest findings on the volume densities of molecular hydrogen in Giant Molecular Clouds (GMCs) associated with photodissociation regions (PDRs) in the nearby galaxy M33, using HI continuum, FUVand metallicity data. The morphology of the atomic hydrogen distribution is similar to what is expected for PDRs, since the HI is seen surrounding bright FUV sources. Potential PDRs that we detect, in which dissociating photons dominate the radiation field, have sizes in the order of 100 parsec. Complexes of young, hot stars are responsible for these PDRs. They create a 'blanket' of photodissociated HI. The balance equation governing the photodissociation process needs the ultraviolet luminosity incident on the surface of the GMC and the local dust-to-gas ratio together with the HI column density in order to calculate the volume density of molecular hydrogen. Verification of the PDR scheme that we are testing depends ciritically on the spatial resolution of the M33 data. ...
We have obtained surface photometry for a sample of 86 face-on spiral galaxies in the near-infrar... more We have obtained surface photometry for a sample of 86 face-on spiral galaxies in the near-infrared (H and/or K-passbands) and the optical (B,V,R and I-passbands). This statistically complete diameter limited sample can be used to represent a volume limited sample. Therefore we can examine the number frequency per volume of these galaxies with respect to their parameters. An important parameter that has been studied is the central surface brightness of the disk. As the radial light profile of spiral galaxies can be described by an exponential disk, they are characterized by two parameters, the central surface brightness (mu_0 ) and the scalelength (h). Since the classical paper of Freeman (1970) it is assumed that the value for mu_0 is constant among the galaxies, at least in the B-passband. We will show that mu_0 has no constant value but depends on galaxy type and that this dependence is even stronger going to longer wavelengths. Furthermore we find that almost all the disks of th...
Galaxies and their Masks, 2010
Nature Physical Science, 1973
Astrophysics and Space Science Library, 1988
ABSTRACT
Toward a New Millennium in Galaxy Morphology, 2000
Astrophysics and Space Science Library, 1992
In this review I discuss various aspects of the large scale structure and dynamics of spiral gala... more In this review I discuss various aspects of the large scale structure and dynamics of spiral galaxies. It is first pointed out that spirals basically exist of two discrete components, which may indicate that there have been two epochs of star formation. In spite of the different light distributions the two galaxies NGC 891 and 7418 have very similar rotation curves, which argues against maximum disk models and revised gravity.
Astronomy and Astrophysics
Astronomy and Astrophysics
ABSTRACT
We report our latest findings on the volume densities of molecular hydrogen in Giant Molecular Cl... more We report our latest findings on the volume densities of molecular hydrogen in Giant Molecular Clouds (GMCs) associated with photodissociation regions (PDRs) in the nearby galaxy M33, using HI continuum, FUVand metallicity data. The morphology of the atomic hydrogen distribution is similar to what is expected for PDRs, since the HI is seen surrounding bright FUV sources. Potential PDRs that we detect, in which dissociating photons dominate the radiation field, have sizes in the order of 100 parsec. Complexes of young, hot stars are responsible for these PDRs. They create a 'blanket' of photodissociated HI. The balance equation governing the photodissociation process needs the ultraviolet luminosity incident on the surface of the GMC and the local dust-to-gas ratio together with the HI column density in order to calculate the volume density of molecular hydrogen. Verification of the PDR scheme that we are testing depends ciritically on the spatial resolution of the M33 data. ...
We have obtained surface photometry for a sample of 86 face-on spiral galaxies in the near-infrar... more We have obtained surface photometry for a sample of 86 face-on spiral galaxies in the near-infrared (H and/or K-passbands) and the optical (B,V,R and I-passbands). This statistically complete diameter limited sample can be used to represent a volume limited sample. Therefore we can examine the number frequency per volume of these galaxies with respect to their parameters. An important parameter that has been studied is the central surface brightness of the disk. As the radial light profile of spiral galaxies can be described by an exponential disk, they are characterized by two parameters, the central surface brightness (mu_0 ) and the scalelength (h). Since the classical paper of Freeman (1970) it is assumed that the value for mu_0 is constant among the galaxies, at least in the B-passband. We will show that mu_0 has no constant value but depends on galaxy type and that this dependence is even stronger going to longer wavelengths. Furthermore we find that almost all the disks of th...
Galaxies and their Masks, 2010
Nature Physical Science, 1973