206 research outputs found
Dynamical processes in galaxy centers
How does the gas get in nuclear regions to fuel black holes? How efficient is
the feedback? The different processes to cause rapid gas inflow (or outflow) in
galaxy centers are reviewed. Non axisymmetries can be created or maintained by
internal disk instabilities, or galaxy interactions. Simulations and
observations tell us that the fueling is a chaotic and intermittent process,
with different scenarios and time-scales, according to the various radial
scales across a galaxy.Comment: 6 pages, 3 figures, to appear in "The Central Kiloparsec in Galactic
Nuclei: Astronomy at High Angular Resolution 2011", open access Journal of
Physics: Conference Series (JPCS), published by IOP Publishin
The Square Kilometer Array: cosmology, pulsars and other physics with the SKA
SKA is a new technology radio-telescope array, about two orders of magnitude
more sensitive and rapid in sky surveys than present instruments. It will probe
the dark age of the universe, just afer recombination, and during the epoch of
reionisation (z=6-15); it will be the unique instrument to map the atomic gas
in high redshift galaxies, and determine the amount and distribution of dark
matter in the early universe. Not only it will detect and measure the redshifts
of billions of galaxies up to z=2, but also it will discover and monitor around
20 000 pulsars in our Milky Way. The timing of pulsars will trace the
stretching of space, able to detect gravitational waves. Binary pulsars will
help to test gravity in strong fields, and probe general relativity. These
exciting perspectives will become real beyond 2020.Comment: 16 pages, 5 figures, Proceedings of INFIERI-2014, Summer School on
"Intelligent Signal Processing for Frontier Research and Industry", JINS
Cosmic evolution of gas content and accretion
In the present universe, the gas is a minor component of giant galaxies, and
its dominant phase is atomic (HI). During galaxy evolution in cosmic times,
models predict that gas fractions were much higher in galaxies, and gas phases
could be more balanced between molecular (H2) and atomic (HI). This gaseous
evolution is certainly a key factor to explain the cosmic evolution of the star
formation rate density. Star formation efficiency might also vary with
redshift, and the relative importance of these factors is not yet well known.
Our current knowledge of cosmic evolution of gas from molecular observations at
high-z is reviewed and confronted to simulations.Comment: 8 pages, 3 figures, to be published in Seychelles conference on
galaxy evolution, "Lessons from the Local Group", ed. K. C. Freeman, B. G.
Elmegreen, D. L. Block, and M. Woolway (Dordrecht: Springer), in press, 201
CO(2-1) large scale mapping of the Perseus cluster core with HERA
Cold molecular gas has recently been found is several cooling flow clusters
cores with single dish telescopes. High spatial resolution imaging of some of
these clusters then revealed the peculiar morphology and dynamics of the CO
emission lines, pointing out a perturbed very cold component in the cluster
centers. We report here the observations of NGC 1275, in the Perseus cluster of
galaxies. This object is the strongest cooling flow emitter in the millimeter.
The 9 dual polarization pixels of the HERA focal plane array, installed on the
30m telescope, enabled to image the large scale emission of the cold molecular
gas which is found to follow the very peculiar Halpha filamentary structure
around the central galaxy. We discuss here this association and the
non-rotating dynamics of the cold gas that argue for a cooling flow origin of
the molecular component.Comment: 2 pages, 1 figure, to be published in SF2A-2005, to be published by
EdP-Sciences, F. Casoli, T. Contini, J-M. Hameury & L. Pagani (eds
- …