I am pleased to share this deep image of Centaurus A which I believe is the first image to reveal the full extent of it’s jet in both Ha and OIII emission. The image also shows the galaxies multiple faint outer shells and stellar streams that extend up to 40 arc minutes from the nucleus.

Cen A Jet
Cen A is well known for having a narrow relativistic jet emanating from its central supermassive black hole. This outflow results in an ionised hydrogen jet to the north of the galaxy. The AGN does have a weaker counter-jet which flows to the south of the galaxy, and some faint Ha emission has also been detected in this direction.

The northern Ha jet is characterised by brighter inner and outer filaments and the more recently recognised c filament. On my image you can also see faint Ha emission extending between the inner and outer filaments, and some diffuse Ha emission extending from the centre of Cen A towards the inner filament (labelled with arrows in figure below). This additional Ha emission appears to join the galaxy nucleus, and the inner and outer filaments into one continuous jet. A similar continuous jet is present on NUV images from the GALEX satellite (Neff et al, APJ 2015), however I have not seen a Ha continuous jet previously reported. The central Ha emission remains faintly visible on the RGBHO image through the stellar halo of the galaxy.


Continuum subtracted Ha & NUV ©Mathew Ludgate & NASA/Neff et al

To the east of the nucleus there is a faint Ha cloud (circled red in figure above) located at the same location as a satellite dwarf galaxy candidate that was detected on deep images taken with the 6.5m Magellan telescope  (Crnojevic et al, APJ 2016). This previously unreported Ha emission is likely to be the result of active star formation occurring within this dwarf galaxy.

My image also reveals Ha emission to the south which is likely caused by the counter jet in this direction, and this is only one of a few images to detect this southern jet feature. 

OIII Jet
In addition to Ha emission, the jet also results in a smaller amount of OIII emission (see Morganti et al, MNRAS 2011). Prior OIII images have only focused on the inner filament and the first part of the outer filament. This image is the first to show the full extent of the OIII emission jet, including two faint ionised OIII clouds located in the outer segment (circled in figure below). There is diffuse OIII emission radiating from the nucleus which is likely related to starburst within the disc, and this creates a subtle violet halo on the RGBHO image.


Continuum subtracted OIII image ©Mathew Ludgate

Background Ha clouds
On the wider view some extremely faint Ha clouds are visible scattered throughout the galactic cirrus. As the Ha has been processed using continuum subtraction these clouds represent true Ha emission rather than contamination from extended red emission, and in many areas are in different locations and morphology than the cirrus. These clouds likely represent Ha emission from the Milky Way that lie in our line of sight to Cen A.