MIGHTEE: the continuum survey Data Release 1

The MeerKAT International GHz Tiered Extragalactic Exploration Surv e y (MIGHTEE) is one of the large surv e y projects using the MeerKAT telescope, co v ering four fields that have a wealth of ancillary data available. We present Data Release 1 of the MIGHTEE continuum surv e y, releasing total intensity images and catalogues o v er ∼20 de g 2 , across three fields at ∼1.2-1.3 GHz. This includes 4.2 de g 2 o v er the Cosmic Evolution Surv e y (COSMOS) field, 14.4 de g 2 o v er the XMM Large-Scale Structure (XMM-LSS) field and deeper imaging o v er 1.5 de g 2 of the Extended Chandra Deep Field South (CDFS). We release images at both a lower resolution (7-9 arcsec) and higher resolution ( ∼5 arcsec). These images have central rms sensitivities of ∼1 . 3 -2.7 μJy beam -1 ( ∼1 . 2 -3.6 μJy beam -1 ) in the lower (higher) resolution images, respectively. We also release catalogues comprised of ∼144 000 ( ∼114 000) sources using the lower (higher) resolution images. We compare the astrometry and flux-density calibration with the Early Science data in the COSMOS and XMM-LSS fields and previous radio observations in the CDFS field, finding broad agreement. Furthermore, we extend the source counts at the ∼10 μJy level to these larger areas ( ∼20 deg 2 ) and, using the areal co v erage of MIGHTEE we measure the sample variance for differing areas of sky. We find a typical sample variance of 10 -20 per cent for 0.3 and 0.5 de g 2 subre gions at S 1 . 4 ≤200 μJy, which increases at brighter flux densities, given the lower source density and expected higher galaxy bias for these sources.