Composite image of Centaurus A - Herschel, XMM-Newton and ground-based telescope
The iconic Centaurus A galaxy, also known as NGC 5128, is the closest giant elliptical galaxy containing a radio-loud Active Galactic Nucleus (AGN).
This image of Centaurus A is a composite, using data in four different wavebands: X-rays (shown in cyan, blue and purple, in order of increasing energy), far-infrared (shown in yellow), sub-millimetre (shown in red), and the visible waveband. The X-ray data was obtained with the EPIC camera on board ESA's XMM-Newton X-ray Observatory; the far-infrared and sub-millimetre data were obtained with the PACS instrument and SPIRE instrument, respectively, on board ESA's Herschel Space Observatory; the visible waveband image was obtained with the MPG/ESO 2.2-metre Telescope at La Silla Observatory, Chile.
At optical wavelengths, Centaurus A exhibits the morphology of an elliptical galaxy with a spheroidal halo of stars; in addition, a prominent dark lane appears to cross the halo at these wavelengths, as evident in the ground-based data. Observations in the infrared portion of the electromagnetic spectrum allow astronomers to peer through this obscuring lane and to reveal the structure of the galaxy's disc by detecting the glow of cold dust within it, as highlighted in the Herschel/PACS data.
Moreover, due to the AGN activity of Centaurus A, powerful jets of highly energetic particles stream from the core of the galaxy, where a supermassive black hole accretes matter at a tremendous rate. As electrons in the jets emit synchrotron radiation, the jets shine brightly in X-rays as well as at sub-millimetre and radio wavelengths. The jets and their interaction with the diffuse interstellar medium of the galaxy are evident in both the Herschel/SPIRE and the XMM-Newton data.
Multi-wavelength observations of Centaurus A allow astronomers to develop a comprehensive view of how the various components of this fascinating galaxy interact with one another on different scales. At a distance of only about 12 million light years, Centaurus A is an ideal test bed for investigating the physical processes taking place in active galaxies, allowing astronomers to spatially resolve details that are much harder to detect in more distant sources.
In X-rays, a number of foreground point-like sources are also visible, scattered across the image: these are X-ray binaries belonging to our Galaxy, the Milky Way.