Spectral Line Survey of Ionized Jet Candidates from Broadband VLA Observations
Abstract
Given the versatility of the Karl G. Jansky Very Large Array correlator, radio continuum surveys with the VLA are inherently broadband spectral line scans. We present results of an algorithm developed to search for both bright and narrow and also weak and broad spectral lines in continuum observations conducted with the VLA. We focus on the search for high-excitation ammonia transitions and radio recombination lines in the high sensitivity continuum survey for ionized jets toward young high-mass star-forming regions from Rosero et al. (2016, 2019). We report the detection of twenty high excitation ammonia lines toward four sources, in a range of transitions from (J, K) = (4,1) to (9,7), which corresponds to energy levels between 279 K and 1021 K. In the case of radio recombination lines (RRLs), the script was designed to stack multiple transitions to increase sensitivity. At 6 cm, we stacked an average of five hydrogen RRL transitions per source, resulting in 130 uJy/b RMS (133 km/s channel width); while at 1.3 cm, an average of two hydrogen RRLs were stacked resulting in a 55 uJy/b RMS (38 km/s channel width). To obtain the best possible statistical detection limit of RRLs in the sample, we stacked all spectral windows at RRL frequencies from all sources, resulting in 7.0 uJy/b RMS (6 cm; 133 km/s channel width) and 17 uJy/b RMS (1.3 cm; 38 km/s channel width). We found that the RMS in the stacked data follows the radiometer equation, which highlights the potential of statistical studies of weak spectral lines from stacking broadband spectral windows from VLA continuum-mode observations. This work is partially supported by NSF grants AST-1814063 and AST-1814011, and computational resources donated by WIU Distinguished Alumnus Frank Rodeffer.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23521605S