31,906 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
The nature of the LINER in the galaxy NGC 404
NGC 404, at a distance of 3.4 Mpc, is the nearest S0 galaxy. This galaxy
harbors a LINER; however, since the spectrum does not show a broad H{\alpha}
emission, it is not certain that this LINER is a low luminosity AGN and its
nature is still an open question. HST observations show the existence of
stellar populations with an age of 3 x 10^8 years years in the galactic bulge
and with an age of 6-15 x 10^9 years in the galactic disk. In this work, we
present an analysis of the data cube of NGC 404 obtained with the IFU (Integral
Field Unity) of the GMOS (Gemini Multi-Object Spectrograph) on the Gemini North
telescope.Comment: 2 pages, 2 figure
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
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