A high-resolution VLA survey of the alpha = 08h52m15s, delta = +17 deg 16 arcmin field

A single primary beam area centered on alpha = 08h52m15s, delta = +17 deg 16 arcmin was mapped with the VLA at 5.8-arcsec resolution to investigate the angular sizes of very faint radio sources at 1465 MHz. Previously, this field (approximately one square degree) was mapped with 19-arcsec resolution to a 6.3 sigma flux density limit of 84 micro Jy. The rms noise in the high resolution map is sigma equal to about 21 micro Jy; hence all previously detected point sources should be present at a confidence level of four sigma. The low resolution map was used to verify that sources were not resolved away by the high resolution observations. The median angular size (theta med) found for the faintest sources (greater than or equal to 84 and less than 400 micro Jy) is less than or equal to 3 arcsec. It is significantly lower than the extrapolation of earlier data and models in which theta med remains constant in the range 7-10 arcsec for sources brighter than about 1 mJy and fainter than 100 mJy. The observed dropoff in angular size is consistent with most stronger sources being produced by elliptical galaxies, while the fainter sources reside in spiral or Seyfert galaxies. Thus a simple model can fit the new data without requiring size evolution of radio sources.