| 20th of February 2020 |
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| ATCA OH Maser observations for the SPLASH Survey |
| by Qiao et al. |
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Ground-state hydroxyl (OH) transitions arise from four hyperfine
sub-levels within the lowest rotational state, with "main line"
frequencies of 1665.402 and 1667.359 MHz and "satellite line"
frequencies of 1612.231 and 1720.530 MHz.
Qiao et al. present high spatial resolution observations of
ground-state OH masers achieved with the Australia Telescope Compact
Array (ATCA). These observations targeted 253 pointing centres
containing OH maser candidates at all four ground-state OH transitions
identified in the Southern Parkes Large-Area Survey in Hydroxyl
(SPLASH) across 96 square degrees of the Southern Galactic plane.
Maser emission was detected towards 236 fields: 7 of 17 ATCA
non-detections of Parkes sources are thought to be due to the slightly
lower sensitivity of the ATCA observations, combined with some
temporal variability. The superior angular resolution provided by the
ATCA data allowed the identification of 362 OH maser sites in the 236
target fields. Almost half (160 of 362) of these masers were detected
for the first time.
The image above shows the full survey region of SPLASH (blue outline): the red shaded region is the pilot and the cyan shaded region is the Galactic Center region -- these were presented in earlier papers. The unshaded area shows the Galactic ranges presented in the current paper. The black crosses, yellow circles, blue squares and carmine rhombuses mark the locations of evolved star, star formation, SNR and unknown OH maser sites detected in the ATCA observations, respectively. More details are given in the paper to be published in Monthly Notices of the Royal Astronomical Society. |