Red giants in the outer halo of the elliptical galaxy NGC 5128/Centaurus A

We used VIMOS on VLT to perform V and I band imaging of the outermost halo of NGC 5128/Centaurus A ((m − M)0 = 27.91±0.08), 65 kpc from the galaxy’s center and along the major axis. The stellar population has been resolved to I0 ≈ 27 with a 50% completeness limit of I0 = 24.7, well below the tip of the red-giant branch (TRGB), which is seen at I0 ≈ 23.9. The surface density of NGC 5128 halo stars in our fields was sufficiently low that dim, …