Cosmic rays from the nearby starburst galaxy NGC 253 : the effect of a low luminosity active galactic nucleus

Eduardo M. Gutiérrez, Gustavo E. Romero, Florencia L. Vieyro.

Serie: Trabajos publicados del IAR ; no. 1534

Resumen: NGC 253 is a nearby starburst galaxy in the Sculptor group located at adistance of ∼3.5 Mpc that has been suggested by some authors as apotential site for cosmic-ray acceleration up to ultra-high energies.Its nuclear region is heavily obscured by gas and dust, which preventsestablishing whether or not the galaxy harbours a supermassive blackhole coexisting with the starburst. Some sources have been proposed inthe literature as candidates for an active nucleus. In this work, we aimat determining the implications that the presence of a supermassiveblack hole at the nucleus of NGC 253 might have on cosmic rayacceleration. With this aim, we model the accretion flow on to theputative active nucleus, and we evaluate the feasibility of particleacceleration by the black hole dynamo mechanism. As a by-product, weexplore the potential contribution from non-thermal particles in theaccretion flow to the high-energy emission of the galaxy. We found thatin the three most plausible nucleus candidates, the emission of theaccretion flow would inhibit the black hole dynamo mechanism. To ruleout completely the influence that a putative nucleus in NGC 253 mighthave in cosmic-ray acceleration, a better clarification concerning thetrue nature of the nucleus is needed