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Radio halos are diffuse, extended sources of radio emission detectedprimarily in massive, merging galaxy clusters. In smaller and/or relaxedclusters, where no halos are detected, one can instead place upper limits to apossible radio emission. Detections and upper limits are both crucial toconstrain theoretical models for the generation of radio halos. The upperlimits are model dependent for radio interferometers and thus the process ofobtaining these is tedious to perform manually. In this paper, we present aPython based tool to automate this process of estimating the upper limits. Thetool allows users to create radio halos with defined parameters like physicalsize, redshift and brightness model. A family of radio halo models with a rangeof flux densities, decided based on the rms noise of the image, is theninjected into the parent visibility file and imaged. The halo injected imageand the original image are then compared to check for the radio halo detectionusing a threshold on the detected excess flux density. Injections separated byfiner differences in the flux densities are carried out once the coarse rangewhere the upper limit is likely to be located has been identified. The coderecommends an upper limit and provides a range of images for manual inspection.The user may then decide on the upper limit. We discuss the advantages andlimitations of this tool. A wider usage of this tool in the context of theongoing and upcoming all sky surveys with the LOFAR and SKA is proposed withthe aim of constraining the physics of radio halo formation. The tool ispublicly available at https://github.com/lijotgeorge/UL-CALC.

An upper limit calculator (UL-CALC) for undetected extended sources with radio interferometers: radio halo upper limits