Line Fitting¶
The line fitting is done using pyspeckit
We use the NH3 model included in pyspeckit
to simultaneously fit NH3 (1,1) and (2,2) to derive the parameters of NH3.
This includes the centroi velocity, velocity dispersion, excitation temperature,
kinetic temperature, and column density.
Although we also observed NH3 (3,3) we do not attempt to fit for the ortho-para ratio of NH3, by default we set the ortho-para ratio to 0, therefore, we only report the para-NH3 column density.
Fitting GAS data¶
We have setup a couple of convenience functions to do the line fitting. For this, it assumes that the files are stored in a directory named ‘region_name’. For example, if we want to fit the data for OrionA, then we do the following:
import GAS.PropertyMaps GAS.PropertyMaps.cubefit(region='OrionA', vmin=5.6, vmax=13.7, do_plot=False, snr_min=3.0, multicore=40, file_extension='base_DR1', mask_function = None)
If you want to make some quick plots showing the fit results, then do the following
import astropy.units as u import GAS.PropertyMaps GAS.PropertyMaps.plot_cubefit(region='OrionA', distance=450*u.pc, dvmin=0.05, dvmax=0.7, vcmin=5.7, vcmax=12.7, file_extension='base_DR1')
The result from this line fitting will most likely include pixels that don’t have a good fit (because of the default value for the minimum snr), however, we only need to do this fit once and now we clean-up the parameter fit to keep only those that are reliable.