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We have used photometric images of ten barred galaxies in the B and I bands to infer the geometrical and dynamical parameters of their bars: Their length, (R
bar), their strengths, (S
b), and their corotation radii, (R
CR).These parameters have been obtained studying azimuthal profiles from the B and I band images of the galaxies. We find that R
CR is in all cases slightly larger than R
bar, with mean values close to 1.2 R
bar. We have also found a dependence of the ratio R
CR/R
bar on S
bar.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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J.A.L. Aguerri M. Prieto A.M. Varela C. Muñoz-Tuñón 《Astrophysics and Space Science》2001,276(2-4):611-618
The isophotal profiles and colour maps of a sample of 12 spiral galaxies allowed us to analyse the different structural components
that compose them. These components were parameterized by performing a decomposition of the galaxy brightness profiles. Inferring
the geometry for each component, we have obtained the spatial mass distribution and the gravitational potential for each object.
Here we present the detailed analysis for one of the galaxies in the sample, the barred galaxy NGC 1300.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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I. Trujillo A. Asensio Ramos J. A. Rubiño-Martín Alister W. Graham J. A. L. Aguerri J. Cepa C. M. Gutiérrez 《Monthly notices of the Royal Astronomical Society》2002,333(3):510-516
We have investigated the structural and dynamical properties of triaxial stellar systems whose surface brightness profiles follow the r 1/ n luminosity law – extending the analysis by Ciotti, who explored the properties of spherical r 1/ n systems. A new analytical expression that accurately reproduces the spatial (i.e., deprojected) luminosity density profiles (error less than 0.1 per cent) is presented for detailed modelling of the Sérsic family of luminosity profiles. We evaluate both the symmetric and the non-axisymmetric components of the gravitational potential and force, and compute the torques as a function of position. For a given triaxiality, stellar systems with smaller values of n have a greater non-axisymmetric gravitational field component . We also explore the strength of the non-axisymmetric forces produced by bulges with differing n and triaxiality on systems having a range of bulge-to-disc ratios. The increasing disc-to-bulge ratio with increasing galaxy type (decreasing n ) is found to greatly reduce the amplitude of the non-axisymmetric terms, and therefore reduce the possibility that triaxial bulges in late-type systems may be the mechanism or perturbation for non-symmetric structures in the disc.
Using seeing-convolved r1/ n -bulge plus exponential-disc fits to the K -band data from a sample of 80 nearby disc galaxies, we probe the relations between galaxy type, Sérsic index n and the bulge-to-disc luminosity ratio. These relations are shown to be primarily a consequence of the relation between n and the total bulge luminosity. In the K band, the trend of decreasing bulge-to-disc luminosity ratio along the spiral Hubble sequence is predominantly, though not entirely, a consequence of the change in the total bulge luminosity; the trend between the total disc luminosity and Hubble type is much weaker. 相似文献
Using seeing-convolved r
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Quantitative structural analysis of the galaxies present in the Hawaiian Deep Fields SSA13 and SSA22 is reported. The structural parameters of the galaxies have been obtained automatically by fitting a two-component model (Sérsic r 1/ n bulge and exponential disc) to the surface brightness of the galaxies. The galaxies were classified on the basis of the bulge-to-total luminosity ratio ( B / T ) . The magnitude selection criteria and the reliability of our method have been checked by using Monte Carlo simulations. A complete sample of objects up to redshift 0.8 has been achieved. Spheroidal objects (E/S0) represent ≈33 per cent and spirals ≈41 per cent of the total number of galaxies, while mergers and unclassified objects represent ≈26 per cent. We have computed the comoving space density of the different kinds of object. In an Einstein–de Sitter universe, a decrease in the comoving density of E/S0 galaxies is observed as redshift increases (≈30 per cent less at z =0.8) , while for spiral galaxies a relatively quiet evolution is reported. The framework of hierarchical clustering evolution models of galaxies seems to be the most appropriate to explain our results. 相似文献
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S. Lourenso J.A.L. Aguerri A. Vazdekis J.E. Beckman R.F. Peletier 《Astrophysics and Space Science》2003,284(2):925-928
High spatial resolution visible and NIR observations of the bar of NGC 5850, a prototype of double barred spirals, together
with visible intermediate and high dispersion spectra along the primary bar, are being used, with the aid of simple stellar
population synthesis models, to investigate the mean age and metallicity of the different stellar components of the central
part of the galaxy. The determination of stellar ages and metallicities would constrain theoretical scenarios for secondary
bar formation and the evolution of barred spirals. Unfortunately, we cannot obtain a good fit with simple stellar populations
(SSPs) to the spectral indices, so it can not give us, by now, insight into the mean stellar age and metallicity of the real
populations in the central region of the galaxy. These preliminary results show a relatively old primary bar with metallicity
about solar, although absolute values must be taken with care. The nucleus has a young stellar component, and is very dusty.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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