Fake? AGN Galaxies!
Hidden deep inside the center of most massive galaxies is a central super-massive black hole. However, a in a few percent of galaxies, the black hole is growing in size by accretion of matter. These galaxies are called Active Galactic Nuclei (AGN) . By studying these galaxies we can piece together the picture of how galaxies assemble themselves, growing as stars form and their central super-massive black holes accrete matter. In the local universe , we used Galaxy Zoo’s classifications of AGN host galaxies for a study that revealed “The fundamentally different co-evolution of super-massive black holes and their early- and late-type host galaxies”.
But to really understand how most galaxies were built up, we need to look farther back in time, out to where most galaxies in the present day universe were growing most of their mass. Because the light from distant galaxies takes so long to reach us, in Hubble Zoo we are able to see galaxies as they were in the distant past. (In Hubble Zoo most of the galaxies we see are images from ~ 5-7 billion years in the past !). However, as you may have noticed, the Hubble Zoo galaxies appear much smaller. Because the light emitted near an actively growing black hole can be comparable to the light that we see in from an entire galaxy, in Hubble Zoo we have to be careful when classifying galaxies with these luminous centers. To understand what we’re seeing, a team of Galaxy Zoo Scientists have created images, artificially adding the luminous centers of AGN to some of the Hubble Zoo galaxies. These Fake AGN will allow us to determine if how accurately we can classify the host galaxies of the actual AGN in the Hubble Images.