docs: def Vizier_xmatch(self, viz_cat, cat_name, ra_col='_RAJ2000', dec_col='_DEJ2000', radius='', group=True):
          """
          Use astroquery to pull in and cross match a catalog with sources in self.catalog
          
          Parameters
          ----------
          viz_cat: str
              The catalog string from Vizier (e.g. 'II/246' for 2MASS PSC)
          cat_name: str
              A name for the imported catalog (e.g. '2MASS')
          radius: astropy.units.quantity.Quantity
              The matching radius
          """
          # Make sure sources have been grouped
          if self.catalog.empty:
              print('Please run group_sources() before cross matching.')
              return
              
          if self._catalog_check(cat_name):
              
              # Verify the cat_name
              viz_cat = "vizier:{}".format(viz_cat)
              
              # Prep the current catalog as an astropy.QTable
              tab = at.Table.from_pandas(self.catalog)
              
              # Crossmatch with Vizier
              print("Cross matching {} sources with {} catalog. Please be patient...".format(len(tab), viz_cat))
              data = XMatch.query(cat1=tab, cat2=viz_cat, max_distance=radius or self.xmatch_radius*q.deg, colRA1='ra', colDec1='dec', colRA2=ra_col, colDec2=dec_col)
              
              # Ingest the data
              self.ingest_data(data, cat_name, 'id', ra_col=ra_col, dec_col=dec_col)
              
              # Regroup
              if group:
                  self.group_sources(self.xmatch_radius)