2021AJ....161..255E

We observe a system of filaments and clusters around Cl0016+1609 and MACSJ1621.4+3810 using the SITELLE Fourier transform spectrograph at the Canada-France-Hawaii Telescope. For Cl0016+1609 (z = 0.546), the observations span an 11.8 Mpc x 4.3 Mpc region along an eastern filament that covers the main cluster core, as well as two 4.3 Mpc x 4.3 Mpc regions that each cover southern subclumps. For MACSJ1621.4+3810 (z = 0.465), 3.9 Mpc x 3.9 Mpc around the main cluster core is covered. We present the frequency and location of the emission-line galaxies and their emission-line images, and calculate the star formation rates, specific star formation rates, and merger statistics. In Cl0016+1609, we find 13 [O II] 3727 Å emitting galaxies with star formation rates between 0.2 and 14.0 M_☉ yr^–1. Of these, 91_–10⁺³% are found in regions with moderate local galaxy density, avoiding the dense cluster cores. These galaxies follow the main filament of the superstructure and are mostly blue and disky, with several showing close companions and merging morphologies. In MACSJ1621.4+3810, we find 10 emission-line sources. All are blue (100_–15⁺⁰%), with 40_–12⁺¹⁶% classified as disky and 60_–16⁺¹²% as merging systems. Eight avoid the cluster core (80_–17⁺⁷%), but two (20_–7⁺¹⁷%) are found near high-density regions, including the brightest cluster galaxy (BCG). These observations push the spectroscopic study of galaxies in filaments beyond z ∼ 0.3 to z ∼ 0.5. Their efficient confirmation is paramount to their usefulness as more galaxy surveys come online.