Oral Presentation
From the star formation history of the core to the structure of the outskirts: stacking analyses of the MaDCoWS2 clusters between z=0.5 and 2
Presenter: Ariane Trudeau (ASIAA (formerly at the University of Florida))
We present two stacking analyses that exploit the statistical power of the Massive and Distant Clusters of WISE Survey 2 (MaDCoWS2) to investigate the star formation history of cluster galaxies and the assembly history of clusters from z=0.5 to 2. To investigate the star formation history, we combine WISE, GALEX, and Herschel images to study the star formation history of 10k clusters and groups at z=0.5 to 2.5 within the GAMA fields. Our results show that the sSFR increases with projected radius and redshift, with a transition at z=1.6 to a flat sSFR profile suggesting that the onset of the environmental quenching happened at this epoch, with a timescale of about 600 Myr. The sSFR shows a marginal dependence with the SNR at redshift smaller than 1.2, with the more massive clusters displaying less SF activity in their cores. To investigate the assembly history, we next apply the same stacking technique to the 83k clusters at z=0.5 to 2 in the MaDCoWS2 survey. We show that the splashback radius — the apocenter of the first orbit of infalling material and the physical boundary between the cluster and its infalling region — is detectable in stacked WISE 1 and 2 images. We use this new splashback determination technique to show that the fractions of stellar mass within the clusters infalling regions increase with increasing redshift — a proof of concept that highlights the potential of this technique to probe the star formation history of the cluster infalling region.
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