High-resolution Observations of Cen A: Yellow and Red Supergiants in a Region of Jet-induced Star Formation?

We present the analysis of near-infrared (NIR), adaptive optics Subaru and archived HST imaging data of a region near the northern middle lobe of the Centaurus A (Cen A) jet, at a distance of ∼15 kpc northeast from the center of NGC5128. Low-pass filtering of the NIR images reveals a strong— above the background mean—signal at the expected position of the brightest star in the equivalent HST field. Statistical analysis of the NIR background noise suggests that the probability to observe a signal at the same position, in three independent measurements due to stochastic background fluctuations alone is negligible ( ) and, therefore, that this signal should reflect the detection of the NIR counterparts of the brightest HST star. An extensive photometric analysis of this star yields V − I, visual–NIR, and NIR colors expected from a yellow supergiant with an estimated age Myr. Furthermore, the second and third brighter HST stars are, likely, also supergiants in Cen A, with estimated ages Myr and Myr, respectively. The ages of these three supergiants are in good agreement with the ages of the young massive stars that were previously found in the vicinity and are thought to have formed during the later phases of the jet-H i cloud interaction that appears to drive the star formation in the region for the past ∼100 Myr.