High resolution observations of Cen A: Yellow and red supergiants in a region of jet-induced star formation?

TL;DR

This study identifies yellow and red supergiants in a star-forming region of Centaurus A, linking their ages to jet-induced star formation and providing insights into recent stellar evolution in the galaxy.

Contribution

First detection and analysis of supergiants in Cen A's jet-affected region, connecting stellar ages with jet-driven star formation history.

Findings

Supergiants with ages 10-25 Myr identified near Cen A jet.

Strong statistical evidence for genuine stellar counterparts in NIR imaging.

Star formation likely driven by jet-HI cloud interactions over the past 100 Myr.

Abstract

We present the analysis of near infrared (NIR), adaptive optics (AO) Subaru and archived HST imaging data of a region near the northern middle lobe (NML) of the Centaurus A (Cen A) jet, at a distance of $\sim15$ kpc north-east (NE) from the center of NGC5128. Low-pass filtering of the NIR images reveals strong -- $>3\sigma$ 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 $>3\sigma$ signal at the same position, in three independent measurements due to stochastic background fluctuations alone is negligible ($\leq10^{-7}\%$) 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 (YSG) with an estimated age $\sim10^{+4}_{-3}$ Myr. Furthermore, the second and third brighter HST stars are, likely, also supergiants in Cen A, with estimated ages $\sim16^{+6}_{-3}$ Myr and $\sim25^{+15}_{-9}$ 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-HI cloud interaction that appears to drive the star formation (SF) in the region for the past $\sim100$ Myr.