MALT-45: A 7mm survey of the southern Galaxy - II. ATCA follow-up
  observations of 44GHz class I methanol masers
  We detail interferometric observations of 44GHz class I methanol masers
detected by MALT-45 (a 7mm unbiased auto-correlated spectral-line
Galactic-plane survey) using the Australia Telescope Compact Array. We detect
238 maser spots across 77 maser sites. Using high-resolution positions, we
compare the class I CH$_3$OH masers to other star formation maser species,
including CS (1-0), SiO $v=0$ and the H53$\alpha$ radio-recombination line.
Comparison between the cross- and auto-correlated data has allowed us to also
identify quasi-thermal emission in the 44GHz class I methanol maser line. We
find that the majority of class I methanol masers have small spatial and
velocity ranges ($<$0.5pc and $<$5 km s$^{-1}$), and closely trace the systemic
velocities of associated clouds. Using 870$\mu$m dust continuum emission from
the ATLASGAL survey, we determine clump masses associated with class I masers,
and find they are generally associated with clumps between 1000 and 3000
$M_\odot$. For each class I methanol maser site, we use the presence of OH
masers and radio recombination lines to identify relatively evolved regions of
high-mass star formation; we find that maser sites without these associations
have lower luminosities and preferentially appear toward dark infrared regions.
