Galaxy Clusters

The MultiDark simulation MDR1 has been used by Zandanel, Pfrommer & Prada (2014a, hereafter ZPP14a) to build galaxy cluster mock catalogues (available in table BDMWMfreq of the MDR1 simulation).
The catalogue was created at different redshifts (corresponding to some of the simulation snapshots), matching the observed Sunyaev-Zel’dovich (SZ) and X-ray scaling relations and luminosity function. The mocks also contain information on the radio and gamma-ray emission (Zandanel, Pfrommer & Prada 2014b). We summarise the main steps of the catalogue creation below. If you are using the galaxy cluster mock catalogues in your work, please, cite ZPP14a, and ZPP14b for the radio and gamma-ray content, additionally to this database (Riebe et al. 2013).

Galaxy clusters were selected using only distinct halos from the BDMW catalogue with a total mass (Mtot) above 10¹⁴ M_sun/h. The snapshots corresponding to the following redshifts were used: z = 0, 0.05, 0.1, 0.16, 0.18, 0.2, 0.27, 0.32, 0.37, 0.4, 0.47, 0.53, 0.61, 0.69, 0.78, 0.89 and 1. The total number of galaxy clusters for each snapshot is shown in the table at the end of this page. ZPP13a constructed a phenomenological model for the cluster-gas distribution. This is characterised by X-ray-inferred (cool-core cluster, CCC, and non-cool core cluster, NCCC) gas profiles taken from the REXCESS sample (Croston et al. 2008) and a cluster-mass-dependent gas fraction from Sun et al. (2009). Such a cluster-mass-dependent gas density profile is assigned to each dark matter halo of the sample and is sorted into the NCCC/CCC populations according to the dynamical disturbance parameter Xoff (see MDR1 BDM table description). Additionally, an X-ray temperature is assigned to each halo using the mass-temperature relation of Mantz et al. (2010). This procedure results in a cosmologically complete mock catalogue of galaxy clusters that matches the observed SZ and X-ray scaling relations and luminosity function.

In the companion paper ZPP14b, the main focus is the underlying physics of giant radio halos and mini halos in galaxy clusters. They explore the possibility that radio-emitting electrons are generated in hadronic cosmic ray (CR) proton interactions with ambient thermal protons of the intra-cluster medium. They build a new extended hadronic CR model from cosmological hydrodynamical simulations of cluster formation (Pinzke & Pfrommer 2010) additionally accounting for CR transport in the form of CR streaming and diffusion (Ensslin et al. 2011). This opens the possibility of changing the radio halo luminosity by more than an order of magnitude on a dynamical time scale. Thanks to the CR transport parameterisation and the different scalings of the X-ray luminosity and the SZ flux with respect to gas density, the ZPP13b model is able to simultaneously reproduce the observed bimodality of radio-loud and radio-quiet clusters at the same X-ray luminosity (Burnetti et al. 2009; Ensslin et al. 2011), as well as the unimodal distribution of radio-halo luminosity versus SZ flux (Basu 2012; Sommer & Basu 2013).

ZPP14b also built the hadronic radio halo luminosity function at 1.4 GHz showing that, for a plausible fraction of 10% radio-loud clusters, their model matches the NVSS survey result (Giovannini et al. 1999). Therefore, they provide predictions for the low-frequencies constructing an analytical radio-halo luminosity function at 120 MHz and demonstrate the unique prospects for low-frequency radio surveys (such as the LOFAR Tier 1 survey) to detect about 600 radio halos back to redshift two and to probe the underlying physics of radio halos.

For each galaxy cluster, the mock multi-frequency catalogue stores, among many other properties, its gas density, X-ray bolometric luminosity, SZ flux, hadronic-induced radio halo luminosity at 120 MHz and 1.4 GHz, and the hadronic-induced gamma-ray luminosity above 100 MeV and 100 GeV. We hope that the community can make valuable use of these catalogues in synergy with the future radio (LOFAR), X-ray (eROSITA) and gamma-ray (CTA) data.