Stars and Distant Universe

Stars and Galaxies

The stars and galaxies portal gives access to all the databases on stars and galaxies developped at Paris Observatory.

Some databases result from surveys:

• Large images: multidimensional imagery and tools for virtual observatory
• DENIS

or contains data obtained with specific instruments:

• HIG (Nançay radiotelescope)
• GIRAFFE archive (FLAMES at ESO)

Some of these databases contain both stars and galaxies (Large images, DENIS, GIRAFFE) others are only dedicated to stars (BeSS) or galaxies (HIG).

High Energy Physics

The active cores of galaxies (AGN) are extreme structures in our universe, in the interface of many disciplinary fields: astrophysics of accretion and ejection phenomena, astronomy of very high energies (VHE) gamma-ray, particle physics, very high angular resolution imaging technics, environment of the massive black holes, seek for gravitational waves, cosmology.

Remarkable headways are presently taking place in this domain thanks to the advent of networks of powerful Čerenkov telescopes which sound the sky in gamma-rays at the tera-electronvolt (TeV) domain. It is mainly to the H.E.S.S. (High Energy Stereoscopic System) experiment that we owe this breakthrough. In addition to the numerous results showing the richness of the emission of our own galaxy in gamma rays of very high energies, H.E.S.S. observed in the extragalactic space many new TeV sources, active galactic nuclei: detection of high redshift blazars, discovery of a variable radio-galaxy (M87), new type of TeV emitters, recording of spectra and very detailed light-curves of AGN allowing a fine analysis of the variability and particle acceleration mechanisms. These data allow a direct exploration of the physic close to the black hole horizon and provide experimental data to the theoretical studies on cosmos and matter at extreme energies.

The on-going construction of H.E.S.S.2 will increase the sensitivity and will extend the accessible spectral range towards lower energies, down to 20 GeV, so insuring the connection with the data of the satellite GLAST. Design studies started for the next generation CTA, Čerenkov Telescopes Array, whose construction should start on the horizon 2012. It will open in particular the possibility of analysis of statistical samples of AGN.

In front of the quantity and quality of available data, and of the promising perspectives, our team mobilizes to insure an optimum exploitation of the data collected for the AGN in the very high energies by making available to the astronomical community the high level data.

Description of H.E.S.S.

The High Energy Stereoscopic System (H.E.S.S.) project is the most sensitive detector world-wide for cosmic sources of very high energy gamma rays. It consists of an array of imaging atmospheric Čerenkov telescopes (IACTs) located in Namibia. It is the fruit of a European-African collaboration, regrouping the expertise of several groups who had worked independently on the previous generation of ACTs. The combination of the techniques used by these groups has led to the construction of a detector which is an order of magnitude more sensitive than previous instruments. This leap in sensitivity, together with the location in the Southern hemisphere which gives access to the rich region at the centre of our Galaxy and in the inner Galactic plane, has led HESS to more than double the catalogue of known sources of VHE gamma rays.

The High Energy Stereoscopic System (H.E.S.S.) brings together about 100 scientists from Germany, France, the UK, Ireland, Poland, the Czech Republic, Armenia, South Africa and Namibia.

Our goal is to give a VO compatible output of HESS database. The project is not opened yet.