MEGA Mass Assembly with JWST: The MIRI EGS Galaxy and Active Galactic Nucleus Survey

Abstract We present the Mid-Infrared Instrument (MIRI) Extended Groth Strip (EGS) Galaxy and Active Galactic Nucleus (MEGA) survey, a four-band MIRI survey with 25 pointings in the EGS extragalactic field. Three pointings utilized only the three reddest bands (F1000W, F1500W, and F2100W), while the remainder also included a blue filter (F770W). MEGA builds upon the existing observations in the EGS field by providing MIRI imaging for 68.9% of CEERS NIRCam imaging, filling a crucial gap in order to understand galaxy evolution by observing the obscured Universe. Here, we present the technical design, data reduction, photometric catalog creation for our first data release, and science drivers of the MEGA survey. Our data reduction starts with the standard James Webb Space Telescope calibration pipeline but adds additional warm pixel masking and custom background subtraction steps to improve the quality of the final science image. We estimate the image depth of the reduced mosaics and present new galaxy number counts in four MIRI bands.