34,152 research outputs found
Stellar archeology of the nearby LINER galaxies NGC 4579 and NGC 4736
Stellar archeology of nearby LINER galaxies may reveal if there is a stellar
young population that may be responsible for the LINER phenomenon. We show
results for the classical LINER galaxies NGC 4579 and NGC 4736 and find no
evidence of such populations.Comment: 2 pages, 2 figures, to be published in the Proceedings of the IAU
Symposium no. 26
Mapping low and high density clouds in astrophysical nebulae by imaging forbidden line emission
Emission line ratios have been essential for determining physical parameters
such as gas temperature and density in astrophysical gaseous nebulae. With the
advent of panoramic spectroscopic devices, images of regions with emission
lines related to these physical parameters can, in principle, also be produced.
We show that, with observations from modern instruments, it is possible to
transform images taken from density sensitive forbidden lines into images of
emission from high and low-density clouds by applying a transformation matrix.
In order to achieve this, images of the pairs of density sensitive lines as
well as the adjacent continuum have to be observed and combined. We have
computed the critical densities for a series of pairs of lines in the infrared,
optical, ultraviolet and X-rays bands, and calculated the pair line intensity
ratios in the high and low-density limit using a 4 and 5 level atom
approximation. In order to illustrate the method we applied it to GMOS-IFU data
of two galactic nuclei. We conclude that this method provides new information
of astrophysical interest, especially for mapping low and high-density clouds;
for this reason we call it "the ld/hd imaging method".Comment: 7 pages, 4 figures, accepted for publication on MNRA
Towards the infrared limit in SU(3) Landau gauge lattice gluodynamics
We study the behavior of the gluon and ghost dressing functions in SU(3)
Landau gauge at low momenta available on lattice sizes 12^4-32^4 at
=5.8, 6.0 and 6.2. We demonstrate the ghost dressing function to be
systematically dependent on the choice of Gribov copies, while the influence on
the gluon dressing function is not resolvable. The running coupling given in
terms of these functions is found to be decreasing for momenta q<0.6 GeV. We
study also effects of the finite volume and of the lattice discretization.Comment: 10 pages, 6 figures. Revised version to appear in Phys.Rev.D. Title
modified; a new subsection discusses finite volume and finite lattice spacing
effects; few references adde
PCA Tomography and its application to nearby galactic nuclei
With the development of modern technologies such as IFUs, it is possible to
obtain data cubes in which one produces images with spectral resolution. To
extract information from them can be quite complex, and hence the development
of new methods of data analysis is desirable. We briefly describe a method of
analysis of data cubes (data from single field observations, containing two
spatial and one spectral dimension) that uses Principal Component Analysis
(PCA) to express the data in the form of reduced dimensionality, facilitating
efficient information extraction from very large data sets. We applied the
method, for illustration purpose, to the central region of the low ionization
nuclear emission region (LINER) galaxy NGC 4736, and demonstrate that it has a
type 1 active nucleus, not known before. Furthermore, we show that it is
displaced from the centre of its stellar bulge.Comment: 4 pages, 1 figure, 1 table, to be published in the Proceedings of the
IAU Symposium no. 26
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