VLA 1.3 & 5cm observations of 9 EGOs in the MW Virtual Observatory Resource

Authors
  1. Towner A.P.M.
  2. Brogan C.L.
  3. Hunter T.R.
  4. Cyganowski C.J.
  5. Published by
    CDS
Abstract

We have observed a sample of nine Extended Green Objects (EGOs) at 1.3 and 5cm with the Very Large Array (VLA) with subarcsecond resolution and ~7-14{mu}Jy/beam-sensitivities in order to characterize centimeter continuum emission as it first appears in these massive protoclusters. We find an EGO-associated continu um emission --within 1" of the extended 4.5{mu}m emission-- in every field, which is typically faint (order 10^1^-10^2^{mu}Jy) and compact (unresolved at 0.3"-0.5"). The derived spectral indices of our 36 total detections are consistent with a wide array of physical processes, including both non-thermal (19% of detections) and thermal free-free processes (e.g., ionized jets and compact HII regions, 78% of sample) and warm dust (1 source). We also find an EGO-associated 6.7GHz CH_3_OH and 22GHz H_2_O maser emission in 100% of the sample and a NH_3_(3,3) masers in ~45%; we do not detect any NH_3_(6,6) masers at ~5.6mJy/beam sensitivity. We find statistically-significant correlations between Lradio and Lbol at two physical scales and three frequencies, consistent with thermal emission from ionized jets, but no correlation between L_H2O_ and L_radio_ for our sample. From these data, we conclude that EGOs likely host multiple different centimeter continuum-producing processes simultaneously. Additionally, at our ~1000au resolution, we find that all EGOs except G18.89-0.47 contain 1~2 massive sources based on the presence of CH_3_OH maser groups, which is consistent with our previous work suggesting that these are typical massive protoclusters, in which only one to a few of the young stellar objects are massive.

Keywords
  1. radio-continuum-emission
  2. star-forming-regions
  3. astrophysical-masers
  4. radio-astronomy
Bibliographic source Bibcode
2021ApJ...923..263T
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ivo://CDS.VizieR/J/ApJ/923/263
Document Object Identifer DOI
doi:10.26093/cds/vizier.19230263

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History

2023-08-01T09:28:34Z
Resource record created
2023-08-01T09:28:34Z
Created
2023-10-06T10:38:33Z
Updated

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