A CLUSTER OF COMPACT RADIO SOURCES IN W40

We present deep 3.6 cm radio continuum observations of the H ii region W40 obtained using the Very Large Array (VLA) in its A and B configurations. We detect a total of 20 compact radio sources in a region of 4′ × 4′, with 11 of them concentrated in a band with 30″ of extent. We also present JHK photometry of the W40 cluster taken with the QUIRC instrument on the University of Hawaii 2.2 m telescope. These data reveal that 15 of the 20 VLA sources have infrared counterparts, and 10 show radio variability with periods less than 20 days. Based on these combined radio and IR data, we propose that eight of the radio sources are candidate ultracompact H ii regions, seven are likely to be young stellar objects, and two may be shocked interstellar gas.