Add simple spectral line look up function. #1

src/modules/functions.py

@@ -343,6 +343,28 @@ def create_pv(source, filename, opt_view=6*u.arcmin, min_axis=False):
     return mask_pv
 
 
+def line_lookup(spec_line):
+    """Return rest frequency and object to convert to optical velocities for requested line.
+
+    :param line:
+    :type line:
+    :return:
+    :rtype:
+    """
+
+    if (spec_line == None) or (spec_line == 'HI'):
+        restfreq_line = 1420405751.77 * u.Hz
+        optical = u.doppler_optical(restfreq_line)
+    elif spec_line == 'CO':
+        restfreq_line = 115.27120180 * u.GHz
+        optical = u.doppler_optical(restfreq_line)
+    else:
+        print("ERROR: Unrecognized spectral line.  Try 'HI' or 'CO'.")
+        exit()
+
+    return {'name': spec_line, 'restfreq': restfreq_line, 'optical':optical}
+
+
 def plot_labels(source, ax, default_beam, x_color='k'):
     """Plot labels on spatial plots depending on the coordinate frame.