The Central Molecular Zone ( CMZ ) at the center of our Galaxy is the best template to study star formation processes under extreme conditions , similar to those in high-redshift galaxies .
We observed on-the-fly maps of para-H _ { 2 } CO transitions at 218 GHz and 291 GHz towards seven Galactic Center clouds .
From the temperature-sensitive integrated intensity line ratios of H _ { 2 } CO ( 3 _ { 2 , 1 } - 2 _ { 2 , 0 } ) /H _ { 2 } CO ( 3 _ { 0 , 3 } - 2 _ { 0 , 2 } ) and H _ { 2 } CO ( 4 _ { 2 , 2 } - 3 _ { 2 , 1 } ) /H _ { 2 } CO ( 4 _ { 0 , 4 } - 3 _ { 0 , 3 } ) in combination with radiative transfer models , we produce gas temperature maps of our targets .
These transitions are sensitive to gas with densities of \sim 10 ^ { 5 } cm ^ { -3 } and temperatures < 150 K. The measured gas temperatures in our sources are all higher ( > 40 K ) than their dust temperatures ( \sim 25 K ) .
Our targets have a complex velocity structure that requires a careful disentanglement of the different components .
We produce temperature maps for each of the velocity components and show that the temperatures of the components differ , revealing temperature gradients in the clouds .
Combining the temperature measurements with the integrated intensity line ratio of H _ { 2 } CO ( 4 _ { 0 , 4 } - 3 _ { 0 , 3 } ) /H _ { 2 } CO ( 3 _ { 0 , 3 } - 2 _ { 0 , 2 } ) , we constrain the density of this warm gas to 10 ^ { 4 } - 10 ^ { 6 } cm ^ { -3 } .
We find a positive correlation of the line width of the main H _ { 2 } CO lines with the temperature of the gas , direct evidence for gas heating via turbulence .
Our data is consistent with a turbulence heating model with a density of n = 10 ^ { 5 } cm ^ { -3 } .