arXiv subjects

A. Falvard

Publications and source records attributed to A. Falvard.

6 recordsLinked to original sources

arXiv2020

A parameterisation of the longitudinal Cherenkov emission profiles of gamma induced electromagnetic showers in the atmosphere in the GeV-TeV energy range

In gamma-ray astronomy through Imaging Atmospheric Cherenkov Telescopes (IACT), the atmosphere is used as a calorimeter. Incident gamma-rays in the GeV-TeV energy range are observed through the electromagnetic showers they produce in the atmosphere and the Cherenkov light emitted by them. We aim to obtain a parameterisation of the longitudinal profiles of electromagnetic showers in the atmosphere. The longitudinal Cherenkov emission profiles of these showers can be used for the reconstruction of the parameters of the gamma-photon as well gamma-hadron discrimination. Obtaining an accurate parameterisation of these profiles can therefore be used in the analysis of IACT images as well as fast simulation of the Cherenkov emission from gamma-induced showers in the atmosphere. Such parameterisations are not known to have been systematically carried out prior to this. We carry out Monte Carlo simulations of gamma-induced showers in the atmosphere. The parameterisation of their Cherenkov emission longitudinal profiles is based on the well-known gamma-function used in particle detector physics. We evaluate the dependence of the depth of the maximum and the average depth of the longitudinal Cherenkov emission profile, as well as the parameter $1/\beta$ on the energy of the initial shower. We also study the distributions of various parameters associated with the gamma-function and find that $\beta/\alpha$ and $1/\alpha$ have Gaussian distributions and are not correlated with each other which makes them appropriate variables for evaluating the fluctuations of the Cherenkov emission profiles. We finally present parameterisations of the fluctuations of these two variables.

astro-ph.HE↗

arXiv2008

Future imaging atmospheric telescopes: performance of possible array configurations for gamma photons in the GeV-TeV range

The future of ground based gamma ray astronomy lies in large arrays of Imaging Atmospheric Cherenkov Telescopes (IACT) with better capabilities: lower energy threshold, higher sensitivity, better resolution and background rejection. Currently, designs for the next generation of IACT arrays are being explored by various groups. We have studied possible configurations with a large number of telescopes of various sizes. Here, we present the precision of source, shower core and energy reconstruction for gamma rays in the GeV-TeV range for different altitudes of observation. These results were obtained through tools that we have developed in order to simulate any type of IACT configuration and evaluate its performance.

astro-ph↗

arXiv2006

An indirect dark matter search with diffuse gamma rays from the Galactic Centre with the Alpha Magnetic Spectrometer

The detection of non-baryonic dark matter through its gamma-ray annihilation in the centre of our galaxy has been studied. The gamma fluxes according to different models have been simulated and compared to those expected to be observed with the Alpha Magnetic Spectrometer (AMS), during a long-term mission on board of the International Space Station. Under the assumption that the dark matter halo is composed of the lightest, stable supersymmetric particle, the neutralino, the results of the simulations in the framework of mSUGRA models, show that with a cuspy dark matter halo or a clumpy halo, the annihilation gamma-ray signal would be detected by AMS. More optimistic perspectives are obtained with the Anomaly Mediated Supersymmetry Breaking (AMSB) model. The latter leads also to a cosmologically important 6Li abundance. Finally, the discovery potential for the massive Kaluza-Klein dark matter candidates has been evaluated and their detection looks feasible.

astro-ph↗

arXiv2002

Detecting supersymmetric dark matter in M31 with CELESTE ?

astro-ph↗

arXiv2002

Supersymmetric dark matter in M31: can one see neutralino annihilation with CELESTE?

It is widely believed that dark matter exists within galaxies and clusters of galaxies. Under the assumption that this dark matter is composed of the lightest, stable supersymmetric particle, assumed to be the neutralino, the feasibility of its indirect detection via observations of a diffuse gamma-ray signal due to neutralino annihilations within M31 is examined. To this end, first the dark matter halo of the close spiral galaxy M31 is modeled from observations, then the resultant gamma-ray flux is estimated within supersymmetric model configurations. We conclude that under favorable conditions such as the rapid accretion of neutralinos on the central black hole in M31 and/or the presence of many clumps inside its halo with $r^{-3/2}$ inner profiles, a neutralino annihilation gamma-ray signal is marginally detectable by the ongoing collaboration CELESTE.

astro-ph↗

arXiv2002

High energy photon flux prediction from neutralino annihilation in the globular cluster Palomar 13

The distant globular cluster Palomar 13 has been found to have a very high mass-to-light ratio and its profile can be well fitted either by a King model with a tail, or with a NFW model. This cluster may be the first case of the many clumps predicted by CDM simulations that would not be disrupted by the galactic halo potential. We make the hypothesis that Pal 13 is made of neutralinos and run the DarkSuspect code to estimate the high-energy photon flux due to the annihilation of neutralinos through various channels in some benchmark scenarios. These low fluxes may be used as targets to be reached in proposals for future ground-based high altitude Cerenkov telescopes.

astro-ph↗