A survey for hydroxyl in the THOR pilot region around W43

Andrew J. Walsh*, Henrik Beuther, Simon Bihr, Katharine G. Johnston, Joanne R. Dawson, Jürgen Ott, Steven N. Longmore, Q. Nguyên Luong, Ralf S. Klessen, Sarah Ragan, Naomi McClure-Griffiths, Andreas Brunthaler, James Urquhart, Karl Menten, Frank Bigiel, Friedrich Wyrowski, Michael Rugel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


We report on observations of the hydroxyl radical (OH) within The HI, OH, Recombination line survey (THOR) pilot region. The region is bounded approximately between Galactic coordinates l = 29.°2 to 31.°5 and b = -1.°0 to +1.°0 and includes the high-mass star-forming region W43. We identify 103 maser sites, including 72 with 1612 MHz masers, 42 showing masers in either of the main-line transitions at 1665 and 1667MHzand four showing 1720MHz masers. Most maser sites with either main-line or 1720 MHz emission are associated with star formation, whereas most of the 1612 MHz masers are associated with evolved stars. We find that nearly all of the main-line maser sites are co-spatial with an infrared source, detected by GLIMPSE. We also find diffuse OH emission, as well as OH in absorption towards selected unresolved or partially resolved sites. Extended OH absorption is found towards the wellknown star-forming complex W43 Main.

Original languageEnglish
Pages (from-to)3494-3510
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 1 Feb 2016


  • ISM: molecules
  • Masers
  • Stars: formation


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