The MAGPI Survey: impact of environment on the total internal mass distribution of galaxies in the last 5 Gyr

We investigate the impact of environment on the internal mass distribution of galaxies using the Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey. We use 2D resolved stellar kinematics to construct Jeans dynamical models for galaxies at mean redshift z similar to 0.3, corresponding to a lookback time of 3-4 Gyr. The internal mass distribution for each galaxy is parametrized by the combined mass density slope gamma (baryons + dark matter), which is the logarithmic change of density with radius. We use a MAGPI sample of 28 galaxies from low-to-mid density environments and compare to density slopes derived from galaxies in the high density Frontier Fields clusters in the redshift range 0.29 < z < 0.55, corresponding to a lookback time of similar to 5 Gyr. We find a median density slope of gamma = -2.22 +/- 0.05 for the MAGPI sample, which is significantly steeper than the Frontier Fields median slope (gamma = -2.00 +/- 0.04), implying the cluster galaxies are less centrally concentrated in their mass distribution than MAGPI galaxies. We also compare to the distribution of density slopes from galaxies in ATLAS(3D) at z similar to 0, because the sample probes a similar environmental range as MAGPI. The ATLAS(3D) median total slope is gamma = -2.25 +/- 0.02, consistent with the MAGPI median. Our results indicate environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3-4 Gyr. These results are in agreement with the predictions of cosmological simulations.

Automated summary

We investigate the impact of environment on the internal mass distribution of galaxies using the MAGPI survey. We find that galaxies in high density clusters have less centrally concentrated mass distribution compared to galaxies in low-to-mid density environments. Our results suggest that environment plays a role in the internal mass distribution of galaxies, with no evolution of the slope in the last 3-4 Gyr.