Uncovering the kiloparsec-scale stellar ring of NGC5128

Abstract

We reveal the stellar light emerging from the kiloparsec-scale, ring-like structure of the NGC5128 (Centaurus A) galaxy in unprecedented detail. We use arcsecond-scale resolution near infrared images to create a "dust-free" view of the central region of the galaxy, which we then use to quantify the shape of the revealed structure. At the resolution of the data, the structure contains several hundreds of discreet, point-like or slightly elongated sources. Typical extinction corrected surface brightness of the structure is K_S = 16.5 mag/arcsec^2, and we estimate the total near infrared luminosity of the structure to be M = -21 mag. We use diffraction limited (FWHM resolution of ~ 0.1", or 1.6 pc) near infrared data taken with the NACO instrument on VLT to show that the structure decomposes into thousands of separate, mostly point-like sources. According to the tentative photometry, the most luminous sources have M_K = -12 mag, naming them red supergiants or relatively low-mass star clusters. We also discuss the large-scale geometry implied by the reddening signatures of dust in our near infrared images.Comment: 5 pages, 4 figures, accepted for publication in A&A Letters. A version with high resolution images can be downloaded from http://www.helsinki.fi/~jtkainul/CenALette