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The properties of galaxies in the local universe have been shown to dependupon their environment. Future large scale photometric surveys such as DES andEuclid will be vital to gain insight into the evolution of galaxy propertiesand the role of environment. Large samples come at the cost of redshiftprecision and this affects the measurement of environment. We study this bymeasuring environments using SDSS spectroscopic and photometric redshifts andalso simulated photometric redshifts with a range of uncertainties. We considerthe Nth nearest neighbour and fixed aperture methods and evaluate the impact ofthe aperture parameters and the redshift uncertainty. We find that photometricenvironments have a smaller dynamic range than spectroscopic measurementsbecause uncertain redshifts scatter galaxies from dense environments into lessdense environments. At the expected redshift uncertainty of DES, 0.1, there isSpearman rank correlation coefficient of 0.4 between the measurements using theoptimal parameters. We examine the galaxy red fraction as a function of massand environment using photometric redshifts and find that the bivariatedependence is still present in the SDSS photometric measurements. We show thatphotometric samples with a redshift uncertainty of 0.1 must be approximately6-16 times larger than spectroscopic samples to detect environment correlationswith equivalent fractional errors.

Measuring galaxy environments in large scale photometric surveys