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We have observed a sample of 9 Extended Green Objects (EGOs) at 1.3 and 5 cmwith the VLA with sub-arcsecond resolution and ~7-14 uJy/beam sensitivities inorder to characterize centimeter continuum emission as it first appears inthese massive protoclusters. We find EGO-associated continuum emission - within1 arcsec of the extended 4.5 um emission - in every field, which is typicallyfaint (order 10^1-10^2 uJy) and compact (unresolved at 0.3-0.5 arcsec). Thederived spectral indices of our 36 total detections are consistent with a widearray of physical processes, including both non-thermal (19% of detections) andthermal free-free processes (e.g. ionized jets and compact HII regions, 78% ofsample), and warm dust (1 source). We also find EGO-associated 6.7 GHz CH$_3$OHand 22 GHz H$_2$O maser emission in 100% of the sample, and NH$_3$ (3,3) masersin ~45%; we do not detect any NH$_3$ (6,6) masers at ~5.6 mJy/beam sensitivity.We find statistically-significant correlations between radio-distance andbolometric luminosities at two physical scales and three frequencies,consistent with thermal emission from ionized jets, but no correlation betweenwater-maser and radio-distance luminosities for our sample. From these data, weconclude that EGOs likely host multiple different centimetercontinuum-producing processes simultaneously. Additionally, at our ~1000 auresolution, we find that all EGOs except G18.89$-$0.47 contain 1 to 2 massivesources based on the presence of methanol maser groups, which is consistentwith our previous work suggesting that these are typical massive protoclustersin which only one to a few of the YSOs are massive.

astrophysical journal/the astrophysical journal

VLA Observations of 9 Extended Green Objects in the Milky Way:  Ubiquitous Weak, Compact Continuum Emission, and Multi-Epoch Emission from  CH$_3$OH, H$_2$O, and NH$_3$ Masers