The study presents a reversal of the star formation-density relation in the universe at redshift z ~ 1. Using deep infrared imaging from Spitzer and Hubble, the researchers determined the contribution of obscured light to the star formation rate (SFR) of galaxies in the redshift range 0.8 ≤ z ≤ 1.2. They found that the average SFR of galaxies increased with local galaxy density at z ~ 1, contrary to the local universe where SFR decreases with density. This reversal is attributed to the influence of large-scale structures, with the 1-2 Mpc scale being critical for star formation in galaxies at z ~ 1. The study also shows that the SFR of galaxies at z ~ 1 correlates with stellar mass, suggesting that mass plays a role in the observed star formation-density trend. However, the specific SFR (SFR/M*) decreases with stellar mass while increasing with galaxy density, indicating that the environment directly affects star formation activity. The study also finds that major mergers are not the primary cause of this effect, as nearly half of the luminous infrared galaxies (LIRGs) at z ~ 1 have spiral morphologies. The results suggest that the growth of large-scale structures significantly influences the star formation history of galaxies, and that models must account for this to accurately reproduce the SFR-density relation at z ~ 1. The study also highlights the importance of considering the role of active galactic nuclei (AGNs) and selection effects due to spectroscopic incompleteness in the analysis. The findings provide new insights into the evolution of galaxy formation and the role of the environment in shaping star formation activity.The study presents a reversal of the star formation-density relation in the universe at redshift z ~ 1. Using deep infrared imaging from Spitzer and Hubble, the researchers determined the contribution of obscured light to the star formation rate (SFR) of galaxies in the redshift range 0.8 ≤ z ≤ 1.2. They found that the average SFR of galaxies increased with local galaxy density at z ~ 1, contrary to the local universe where SFR decreases with density. This reversal is attributed to the influence of large-scale structures, with the 1-2 Mpc scale being critical for star formation in galaxies at z ~ 1. The study also shows that the SFR of galaxies at z ~ 1 correlates with stellar mass, suggesting that mass plays a role in the observed star formation-density trend. However, the specific SFR (SFR/M*) decreases with stellar mass while increasing with galaxy density, indicating that the environment directly affects star formation activity. The study also finds that major mergers are not the primary cause of this effect, as nearly half of the luminous infrared galaxies (LIRGs) at z ~ 1 have spiral morphologies. The results suggest that the growth of large-scale structures significantly influences the star formation history of galaxies, and that models must account for this to accurately reproduce the SFR-density relation at z ~ 1. The study also highlights the importance of considering the role of active galactic nuclei (AGNs) and selection effects due to spectroscopic incompleteness in the analysis. The findings provide new insights into the evolution of galaxy formation and the role of the environment in shaping star formation activity.