Surveys of Clumps, Cores, and Condensations in the Cygnus X: II. Radio
  Properties of the Massive Dense Cores
  We have carried out a high-sensitivity and high-resolution radio continuum
study towards a sample of 47 massive dense cores (MDCs) in the Cygnus X
star-forming complex using the Karl G. Jansky Very Large Array, aiming to
detect and characterize the radio emission associated with star-forming
activities down to ~0.01 pc scales. We have detected 64 radio sources within or
closely around the full width at half-maximum (FWHM) of the MDCs, of which 37
are reported for the first time. The majority of the detected radio sources are
associated with dust condensations embedded within the MDCs, and they are
mostly weak and compact. We are able to build spectral energy distributions for
8 sources. Two of them indicate non-thermal emission and the other six indicate
thermal free-free emission. We have determined that most of the radio sources
are ionized jets or winds originating from massive young stellar objects,
whereas only a few sources are likely to be ultra-compact HII regions. Further
quantitative analyses indicate that the radio luminosity of the detected radio
sources increases along the evolution path of the MDCs.
