Santos, J. S.Altieri, B.Popesso, P.Strazzullo, V.Valtchanov, I.Berta, S.Böhringer, H.Conversi, L.Demarco, R.Edge, A. C.Lidman, C.Lutz, D.Metcalfe, L.Mullis, C. R.Pintos-Castro, I.Sánchez-Portal, M.Rawle, T. D.Rosati, P.Swinbank, A. M.Tanaka, M.2026-01-012026-01-010035-8711https://hdl.handle.net/1885/733800579Star formation (SF) in the galaxy populations of local massive clusters is reduced with respect to field galaxies, and tends to be suppressed in the core region. Indications of a reversal of the SF-density relation have been observed in a few z > 1.4 clusters. Using deep imaging from 100-500 μm from Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging REceiver (SPIRE) onboard Herschel, we investigate infrared properties of spectroscopic and photo-z cluster members, and of Ha emitters in XMMU J2235.3-2557, one of the most massive, distant, X-ray selected clusters known. Our analysis is based mostly on fitting of the galaxies spectral energy distribution (SED) in the rest-frame 8-1000 μm. We measure total IR luminosity, deriving star formation rates (SFRs) ranging from 89 to 463M yr-1 for 13 galaxies individually detected by Herschel, all located beyond the core region (r>250 kpc).We perform a stacking analysis of nine star-forming members not detected by PACS, yielding a detection with SFR = 48 ± 16Mȯ yr-1. Using a colour criterion based on a star-forming galaxy SED at the cluster redshift, we select 41 PACS sources as candidate star-forming cluster members. We characterize a population of highly obscured SF galaxies in the outskirts of XMMU J2235.3-2557. We do not find evidence for a reversal of the SF-density relation in this massive, distant cluster.13enGalaxies:Star formationGlaxies:Clusters:Individual:XMMU J2235.3-2557-Galaxies:HighInfrared:GalaxiesRedshift201310.1093/mnras/stt81184880975589