Star formation in the massive cluster merger Abell 2744

We present a comprehensive study of star-forming (SF) galaxies in the Hubble Space Telescope (HST) Frontier Field recent clustermerger A2744 (z = 0.308). Wide-field, ultraviolet-infrared (UV-IR) imaging enables a direct constraint of the total star formation rate (SFR) for 53 cluster galaxies, with SFRUV+IR = 343 +/- 10 M-circle dot yr(-1). Within the central 4 arcmin (1.1 Mpc) radius, the integrated SFR is complete, yielding a total SFRUV+IR = 201 +/- 9 M-circle dot yr(-1). Focusing on obscured star formation, this core region exhibits a total SFRIR = 138 +/- 8 M-circle dot yr(-1), a mass-normalized SFRIR of Sigma(SFR) = 11.2 +/- 0.7 M-circle dot yr(-1) per 10(14) M-circle dot and a fraction of IR-detected SF galaxies f(SF) = 0.080(-0.037)(+0.010). Overall, the cluster population at z similar to 0.3 exhibits significant intrinsic scatter in IR properties (total SFRIR, T-dust distribution) apparently unrelated to the dynamical state: A2744 is noticeably different to the merging Bullet cluster, but similar to several relaxed clusters. However, in A2744 we identify a trail of SF sources including jellyfish galaxies with substantial unobscured SF due to extreme stripping (SFRUV/SFRIR up to 3.3). The orientation of the trail, and of material stripped from constituent galaxies, indicates that the passing shock front of the cluster merger was the trigger. Constraints on star formation from both IR and UV are crucial for understanding galaxy evolution within the densest environments.