The most recent burst of star formation in the massive elliptical galaxy NGC 1052
Résumé
High spatial resolution near-infrared (NIR) images of the central 24 x 24 arcsec(2) (similar to 2 x 2 kpc(2)) of the elliptical galaxy NGC 1052 reveal a total of 25 compact sources randomly distributed in the region. 15 of them exhibit H alpha luminosities an order of magnitude above the estimate for an evolved population of extreme horizontal branch stars. Their H alpha equivalent widths and optical-to-NIR spectral energy distributions are consistent with them being young stellar clusters aged \textless7 Myr. 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 less than or similar to 11 pc and their median reddening is E(B - V) similar to 1 mag. According to previous works, NGC 1052 may have experienced a merger event about 1Gyr ago. On the assumption that these clusters are spread with a similar density over the whole galaxy, the fraction of galaxy mass (5 x 10(-5)) and rate of star formation (0.01M(circle dot) yr(-1)) involved suggest the merger event as the possible cause for the star formation we see today.
Domaines
Astrophysique [astro-ph]
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