The most recent burst of star formation in the massive elliptical galaxy NGC 1052

Abstract

High spatial resolution near-infrared (NIR) images of the central 24 × 24 arcsec2 (~2 × 2kpc2) of the elliptical galaxy NGC 1052 reveal a total of 25 compact sources randomly distributed in the region. 15 of them exhibit Hα luminosities an order of magnitude above the estimate for an evolved population of extreme horizontal branch stars. Their Hα equivalent widths and optical-to-NIR spectral energy distributions are consistent with them being young stellar clusters aged <7Myr. We consider this to be the first direct observation of spatially resolved star-forming regions in the central kiloparsecs of an elliptical galaxy. The sizes of these regions are ≲ 11pc and their median reddening is E(B - V) ~ 1 mag. According to previous works, NGC 1052 may have experienced a merger event about 1 Gyr ago. On the assumption that these clusters are spread with a similar density over the whole galaxy, the fraction of galaxy mass (5 × 10-5) and rate of star formation (0.01 M⊙ yr-1) involved suggest the merger event as the possible cause for the star formation we see today. © 2010 The Authors Monthly Notices of the Royal Astronomical Society © 2010 RAS.