Bucharest, ROMANIA, October 15, 2009 Very High Energy Gamma Ray Astrophysics. Future Developments in Romania Aurelian Radu Institute for Space Sciences

Gamma rays? What’s this? Particles and waves and regions of the electromagnetic spectrum. Gamma ray quanta, gamma ray photons (these particle-like packets of light are called photons ), and waves – electromagnetic waves. L’idée fondamentale de [ma thèse de 1924] était la suivante : « Le fait que, depuis l’introduction par Einstein des photons dans l’onde lumineuse, l’on savait que la lumière contient des particules qui sont des concentrations d’énergie incorporée dans l’onde, suggère que toute particule, comme l’électron, doit être transportée par une onde dans laquelle elle est incorporée »… Mon idée essentielle était d’étendre à toutes les particules la coexistence des ondes et des corpuscules découverte par Einstein en 1905 dans le cas de la lumière et des photons. » Louis de Broglie

Like the Radio Waves, albeit something is different. What is different? Let’s check out the electromagnetic spectrum.

Why do we study the very high energy gamma rays? "Astri e particelle. Le parole dell’ Universo” Words or messengers of distant worlds?

Messengers which provide us with information about: - the cosmic objects where they are generated - the physical mechanisms by whom they are generated - the interactions they undergo on their way to Earth - the interactions with the terrestrial atmosphere Besides, they come from very far away undeflected in the magnetic fields.

The cosmic objects where they are generated: A.Galactic: - supernovae remnants – SNR - pulsars & pulsar wind nebulae – PWN - X – ray binary systems - the Milky Way Center B. Extragalactic: - active galactic nuclei – AGN - gamma ray bursts – GRBs - satellite galaxies of Milky Way

How do we detect the very high energy gamma rays? - detectors aboard of satellites (~ 30 MeV - ~ 50 GeV) - for energies higher than 50 GeV the flux goes down, the detectors area would be too large; - for energies higher than 50 GeV only indirect detection with ground systems: - nonimaging - Extensive Air Shower arrays (EAS) - Imaging Atmospheric Cherenkov Telescopes (IACTs)

IACT (Imaging Atmospheric Cherenkov Telescopes) Small duty cycle, small FoV, high sensitivity, low energy threshold. How does it work?

Size:

Showers: high energy gamma rays generate e+e- pairs the atmosphere; these pairs slow down by bremsstrahlung -> new gamma rays -> new pairs; at some point the energy is so low that only ionizing energy loss is possible. The Cherenkov radiation: a bluish radiation emitted when a charged particle crosses a certain environment at a speed higher than the speed of light through that environment.

Major IACT experiments in operation around the world

ASPERA recommendations:

The efforts made at the Institute of Space Sciences in Bucharest to open the VHE gamma ray window in Romania: - build a ground based Cherenkov telescope for the study of the VHE gamma rays - already have two ongoing projects financed by national programs, that are thought to open the way for building this telescope

Studies concerning the installation of a High Energy Gamma Ray Cherenkov telescope in Romania – GAMMATEL Project No / Sept. 18, 2007, PNCDI2, 21 Months web site: venus.nipne.ro/projects/gammatel Partners at the Project: - Institute of the Space Sciences (ISS) (the leading Institution) - National Meteorological Administration (METEO) - The Technical University of Civil Engineering Bucharest (TUCEB)

General Objectives (GAMMATEL – project) a)Gain the necessary knowledge to build a first Gamma Ray Observatory in Romania. b)Realistic estimation of the necessary technical effort for building the observatory. c)Identification of a group of companies (designing, building, etc.) with whom to create a consortium for building the observatory. d)A preliminary analysis of the environmental impact as well as a of the impact on the local community. e)Strengthen the connection with the ApPEC and ASPERA members, in order to submit a proposal for a large European gamma ray astronomy infrastructure, in the frame of FP7.

Optomecatronic measuring system for the light of night sky background that affect the ground based experiments to detect galactic and extragalactic gamma rays - OPTOGATRON Project No / Oct. 01, 2008, PNCDI2, 36 Months Partners at the Project: - Institute of the Space Sciences (ISS) (the leading Institution) - National Meteorological Administration (METEO) - The National Institute for Research & Development in Fine Mechanics (INCDMF) - Romanian Space Agency (ROSA)

The general objective: to design, build and test a complex system for the measurement of the LONS ( light of night sky ) background that affects the ground based Cherenkov telescopes. This system may be used in the selection procedure of an optimum location for the operation of a Cherenkov telescope and may represent a significant instrumental contribution for Romania and the European CTA project.

Conclusions The Very High Energy Gamma Ray Astrophysics is a major branch of the Astroparticle Physics. Huge European and International efforts are being made to develop the field. Major experiments are under way. We make strides to join them.

Thank you!