A HIGH-RESOLUTION VLA STUDY OF M17-UC1

Using the Very Large Array, we have observed the H66 alpha radio recom bination line (RRL) emission at 1.3 cm and the H52 alpha RRL emission at 7 mm toward the ultracompact H II region M17-UC1 and the nearby are -shaped structure to the east. The angular resolution of the data is 1 ''-2''. The compact H II region (deconvolved size similar to 0''.6 or 0.006 pc) is one of a number of H II regions with broad (greater than or equal to 35 km s(-1)) RRLs. The line parameters of the nearby are o f ionized emission thereafter the Are), about 1'' or 0.01 pc to the ea st of UC1, are remarkably constant over an area of 16''.5 x 3'' (0.17 pc x 0.03 pc). The derived LTE electron temperature from the H66 alpha line (T-H66 alpha is 6600 K in M17-UC1 and 8200 K in the Are region. H2O maser emission at 1.3 cm from the region of M17-UC1 was observed in the D array with a beam of 4''. Observations of the H2O maser emiss ion toward M17-UC1 reveal four masers within 30'' of M17-UC1; two of t hese sources were previously known. We discuss the region near M17-UC1 as an example of shock-induced star formation consisting of a hot, yo ung, massive star surrounded by ionized material, perhaps resulting fr om a stellar wind outflow. We compare M17-UC1 with the six other known examples of broad-line RRL emission from ultracompact H II regions.