ThrUMMS - The Three-mm Ultimate Mopra Milky Way Survey

ThrUMMS Science Goals

ThrUMMS is designed to provide major legacy science opportunities for many years. Thus, the various ThrUMMS team members are interested in a wide variety of science projects that will make use of the ThrUMMS data. Below is a list of some of these projects, with initials of team members who are working on that topic.

Members of the wider astronomical community can also download and make use of ThrUMMS data for any purpose. Alternatively, since ThrUMMS is an open project, anyone can volunteer to join any of the science teams and contribute to the work of that group.


  • Complete maps of 12CO and 13CO over the 4Q will be at 72" angular resolution, equivalent to a spatial resolution of ~1 pc at typical distances of 2-3 kpc, with ~2 or ~1 K/chan rms sensitivity (resp.). PB,EM,BI,SO,VL,MC,AH,GF
  • Obtain uniform, simultaneous information on ISM properties from large to small scales. The formation of molecular clouds, or more accurately the conversion of atomic to molecular gas, is still a matter of active study (Li & Goldsmith 2003; Goldsmith et al 2007; Vasquez-Semadeni et al 2010), as is the longevity of turbulent energy in the ISM across the various phases (Brunt 2003), and indeed, overall cloud lifetimes (Barnes et al 2010, 2011).
  • Comparison with GASKAP will also allow us to resolve the distance ambiguity for GMCs within the 4Q, a fundamental problem for Galactic structure and astrophysics. Together, ThrUMMS and GASKAP will directly lead to a highly-resolved (~1 pc) calculation of the large-scale surface mass density of the Milky Way’s molecular clouds and atomic gas, and in a more uniform and consistent way across more of the Galaxy than even the GRS (Jackson et al 2006) and VGPS (Stil et al 2006) have allowed
  • Compile the CO-derived properties of the >2000 GMC-clumps (based on GRS & ATLASGAL estimates) we are likely to detect, such as size, mass, density, temperature, velocity field, linewidth/degree of turbulence, etc. Furthermore, maps of excitation temperature and optical depth in particular will be very useful as inputs into modelling the MALT90 data and deriving physical conditions in these IRDCs and dense clumps. This is an elementary calculation using the 12CO/13CO line ratio to solve for both Tex and τ in the radiative transfer equation (Hernandez et al 2011).
  • Identify all dense clouds with measurable magnetic field strengths. The role of magnetic fields in star formation, in particular its strength as a function of density, is still vigorously debated (Crutcher et al 2009; Mouschovias & Tassis 2009). Measuring the CN molecule’s Zeeman effect, and hence magnetic field strength, in dense clouds is critical to this debate, but is feasible only where CN is quite bright and has been done in only ∼12 (mostly northern) objects (Falgarone et al 2008). ThrUMMS will easily find all CN clouds in the 4Q bright enough to have their Zeeman effect measured at ALMA, perhaps 40--60 such clouds.