Observations with the Extreme UltraViolet Explorer (EUVE) satellite have shown that the inner region of the Virgo cluster (up to 13' from its center) has a strong Extreme UltraViolet (EUV) emission in excess to the low-energy tail expected from the hot, diffuse Intra-Cluster -Medium (ICM). Here we show that this excess emission can be interpreted as due to IC scattering by a population of relativistic electrons on CBR and starlight photons. It is remarkable that the core radius of the electron population (r_e=5 +-1 kpc) obtained by fitting the EUV data is in agreement with that obtained from the analysis of the radio data towards M87 galaxy, thus indicating that an unique population of relativistic electrons may be at the origin of both radio and EUV excess emission. A prediction of a hard X-ray excess (above 5 keV) towards M87 galaxy is made, which, if confirmed by future observations, would give a further evidence of the presence of the population of relativistic electrons.
EUV excess in the inner Virgo cluster
DE PAOLIS, Francesco;INGROSSO, Gabriele;NUCITA, Achille;ORLANDO, Daniela
2002-01-01
Abstract
Observations with the Extreme UltraViolet Explorer (EUVE) satellite have shown that the inner region of the Virgo cluster (up to 13' from its center) has a strong Extreme UltraViolet (EUV) emission in excess to the low-energy tail expected from the hot, diffuse Intra-Cluster -Medium (ICM). Here we show that this excess emission can be interpreted as due to IC scattering by a population of relativistic electrons on CBR and starlight photons. It is remarkable that the core radius of the electron population (r_e=5 +-1 kpc) obtained by fitting the EUV data is in agreement with that obtained from the analysis of the radio data towards M87 galaxy, thus indicating that an unique population of relativistic electrons may be at the origin of both radio and EUV excess emission. A prediction of a hard X-ray excess (above 5 keV) towards M87 galaxy is made, which, if confirmed by future observations, would give a further evidence of the presence of the population of relativistic electrons.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
