科研之友
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摘要
We present new maser emission from (14)NH(3) (9,6) in NGC 7538. Our observations include the known spectral features near v(LSR) = -60 km s(-1) and -57 km s(-1) and several more features extending to -46 km s(-1). In three epochs of observation spanning two months we do not detect any variability in the ammonia masers, in contrast to the >10-fold variability observed in other (14)NH(3) (9,6) masers in the Galaxy over comparable timescales. We also present observations of water masers in all three epochs for which emission is observed over the velocity range -105 km s(-1) < v(LSR) < -4 km s(-1), including the highest velocity water emission yet observed from NGC 7538. Of the remarkable number of maser species in IRS 1, H(2)O and, now, (14)NH(3) are the only masers known to exhibit emission outside of the velocity range -62 km s(-1) < v(LSR) < -51 km s(-1). However, we find no significant intensity or velocity correlations between the water emission and ammonia emission. We also present a non-detection in the most sensitive search to date toward any source for emission from the CC(32)S and CC(34)S molecules, indicating an age greater than approximate to 10(4) yr for IRS 1-3. We discuss these findings in the context of embedded stellar cores and recent models of the region.
- 出版日期2011-12
