The most recent burst of Star Formation in the Massive Elliptical Galaxy NGC 1052

TL;DR

High-resolution NIR imaging of NGC 1052 reveals young stellar clusters within its central region, indicating recent star formation likely triggered by a past merger event, marking the first direct observation of such activity in an elliptical galaxy's core.

Contribution

This study provides the first direct spatially resolved evidence of recent star formation in the central kiloparsecs of an elliptical galaxy, linked to a historical merger event.

Findings

Identification of 25 compact sources with young stellar populations

Detection of star-forming regions <11 pc in size with significant reddening

Estimated star formation rate of 0.01 Msun/yr linked to merger history

Abstract

High-spatial resolution near-infrared (NIR) images of the central 24 x 24 arcsec^2 (~ 2 x 2 kpc^2) of the elliptical galaxy NGC 1052 reveal a total of 25 compact sources randomly distributed in the region. Fifteen of them exhibit Halpha luminosities an order of magnitude above the estimate for an evolved population of extreme horizontal branch stars. Their Halpha equivalent widths and optical-to-NIR spectral energy distributions are consistent with them being young stellar clusters aged < 7 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 ~< 11 pc 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 spreaded with similar density over the whole galaxy, the fraction of galaxy mass (5 x 10^{-5}) and rate of star formation (0.01 Msun/yr) involved, suggest the merger event as the possible cause for the star formation we see today.