Left The scatter plot of column density estimates in units of equivalent V-band extinction, based on the 2MASS/NICER extinction and the Herschel data, with a varying spectral index \(\beta\). Right Regions corresponding to the three “sub-populations” identified on the plot of A\(_V\)-A\(_V\). The regions are overlaid on the 2MASS extinction map in gray scale. The plots are made with Glue (Beaumont et al 2012; see http://glueviz.org for information about Glue).