Early Science with the Large Millimetre Telescope: Fragmentation of
  molecular clumps in the Galaxy
  Sensitive, imaging observations of the 1.1 mm dust continuum emission from a
1 deg^2 area collected with the AzTEC bolometer camera on the Large Millimeter
Telescope are presented. A catalog of 1545 compact sources is constructed based
on a Wiener-optimization filter. These sources are linked to larger clump
structures identified in the Bolocam Galactic Plane Survey. Hydrogen column
densities are calculated for all sources and mass and mean volume densities are
derived for the subset of sources for which kinematic distances can be
assigned. The AzTEC sources are localized, high density peaks within the
massive clumps of molecular clouds and comprise 5-15% of the clump mass. We
examine the role of the gravitational instability in generating these fragments
by comparing the mass of embedded AzTEC sources to the Jeans' mass of the
parent BGPS object. For sources with distances less than 6 kpc the fragment
masses are comparable to the clump Jeans' mass, despite having isothermal Mach
numbers between 1.6 and 7.2. AzTEC sources linked to ultra-compact HII regions
have mass surface densities greater than the critical value implied by the
mass-size relationship of infrared dark clouds with high mass star formation
while AzTEC sources associated with Class II methanol masers have mass surface
densities greater than 0.7 g cm^{-2} that approaches the proposed threshold
required to form massive stars.
