Letter to the Editor

Uncovering the kiloparsec-scale stellar ring of NGC 5128 ^*,**

¹ Observatory, PO Box 14, 00014 Univ. of Helsinki, Finland e-mail: jtkainul@mpia-hd.mpg.de
² TKK/Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
³ Calar Alto Observatory, Centro Astronómico Hispano, Alemán, C/q Jesús Durbán Remón 2-2, 04004 Almeria, Spain
⁴ European Southern Observatory (ESO), Alonso de Cordova 3107, Santiago, Chile
⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁶ TKK/Department of Radio Science and Engineering, PO Box 3000, 02015 TKK, Finland
⁷ SIM-IDL, Faculdade de Ciências da Universidade de Lisboa, Ed. C8. Campo Grande 1749-016 Lisbon, Portugal
⁸ LIP-Coimbra, Department of Physics, University of Coimbra, 3004-516 Coimbra, Portugal
⁹ INETI, Estrada da Portela, Zambujal-Alfragide, Apartado 7586, 2720-866 Amadora, Portugal

Received: 3 June 2009
Accepted: 13 June 2009

Abstract

We reveal the stellar light emerging from the kiloparsec-scale, ring-like structure of the NGC 5128 (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. The typical extinction-corrected surface brightness of the structure is  mag/arcsec², and we estimate the total near infrared luminosity of the structure to be  mag. We use diffraction limited ( resolution of , or 1.6 pc) near infrared data taken with the NACO instrument on the 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  mag, making 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.