Evidence of AGN activity and a nuclear starburst in the central regions of IC 2497

We present high- and intermediate resolution radio observations of the central region in the spiral galaxy IC 2497, performed using the European VLBI Network (EVN) at 18 cm, and the Multi-Element Radio Linked Interferometer Network (MERLIN) at 18 cm and 6 cm. We detect two compact radio sources, with brightness temperatures above 10 5 K, suggesting that they are related to AGN activity. We show that the total 18 cm radio emission from the galaxy is dominated neither by these compact sources nor large-scale emission, but extended emission confined within a sub-kpc central region. IC 2497 therefore appears as a typical luminous infrared galaxy that exhibits a nuclear starburst with a massive star formation rate (M > 5 M� )o f 12.4M� /yr. These results are in line with the hypothesis that the ionisation nebula “Hanny’s Voorwerp” at a distance of ∼15−25 kpc from the galaxy is ionised by the radiation cone of the AGN.