Galaxy clusters provide a high density environment where galaxies undergo high-speed collisions, ram pressure stripping and tidal interactions. The resulting debris can sometimes be detected in the form of neutral or ionised intergalactic filaments (eg., Oosterloo & van Gorkom 2005; Sun et al. 2006). Abell 3627, also known as the Norma cluster resides at a distance of ∼ 66 Mpc in the heart of the Great Attractor region (Dressler et al. 1987) and is the central cluster in a web of connected filaments (Woudt 1998). At the centre of Abell 3627 lie two key dominant radio galaxies: (1) ESO 137-G006 is host to the wide-angle tailed galaxy (WAT) PKS 1610-608 that is >400 kpc wide; and (2) ESO 132-G007 lies at 290 kpc from the cluster centre and is host to the head-tailed galaxy (HT) PKS 1610-605 with a tail that extends to ∼ 500 kpc, (Jones & McAdam 1996). In 2013-2014, an area of ~1 deg^2 around the central Wide-Angle Tail radio galaxy (WAT) in Abell 3627 was mapped using the ATCA in 5 antenna configurations. This map also includes ESO 137-001, a jellyfish galaxy that is caught-in-the-act of experiencing very strong ram pressure (see figure) as it falls into this cluster. However, galaxy evolution in Norma is poorly-understood and these new observations will help constrain the impact of the cluster processes at play on the gaseous interstellar medium of the individual cluster galaxies.
The specific aims for this project are:
1. To investigate the radio continuum and HI ATCA observations (examine the HI properties both in emission and absorption) in order to study the atomic Hydrogen content of galaxies within this cluster that is host to multiple large radio galaxies that are actively growing their central supermassive black holes.
2. Find and locate HI streams that have been stripped-off of the galaxies since this cluster is a very extreme environment and is highly dynamic. An example is the Virgo Cluster, where a large HI cloud is found by Oosterloo & van Gorkom. The HI plume is both spatially and kinematically connected smoothly with NGC4388, which suggests that the HI is removed from the galaxy NGC 4388 by ram-pressure stripping (Oosterloo & van Gorkom 2005).
3. Constrain the HI column density and estimate the age of the cluster. The HI column density can tell us if it’s possible that star formation could be happening. The extension and velocity of the HI cloud could help us estimate the age of the HI and the cluster.
4. Study the effects of the cluster environment, in particular the proximity to the large radio galaxies and star formation of galaxies near the WAT. This study will further our understanding of how AGN feedback in the radio mode (often invoked in simulations e.g. Croton et al 2006), affect or quench star formation in galaxies (eg. Shabala et al 2011). In Shabala et al 2011, the result indicates that feedback from powerful radio sources plays an important role in driving galaxy evolution.
5. Study the especially strong ram pressure effects in this cluster. One of the galaxies in the vicinity of the WAT is the “poster-child” for extraplanar star formation due to ram pressure stripping, ESO 137-001.
The jellyfish galaxy, ESO 137-001, that is experiencing strong ram pressure during infall into the Norma Cluster.
Professor Lister Staveley-Smith
Director, Science (UWA)Read More