从ALMA的data cube导出moment0

#MKmomentmap.py
#!/usr/bin/python
# -*- coding: utf-8 -*-
##  Zhang Chao 2020-11-27   initial version

from spectral_cube import SpectralCube
from astropy.io import fits
import astropy.units as u
import astropy.constants as c
import numpy as np
import os


def make_moment(fitsfile,window_type,window_range,order):
    '''
    input parameters:
    fitsfile: ALMA data cube file, i.e., fitsfile = "member_uid_*.fits" 
    window_type: A string. The window_type is only suported as 'velocity', 'frequency', and 'channel'. 

    output: The output hdu has a unit of 'K km s-1' or 'km s-1' for zero moment map or first moment map, respectively.
    '''

    f = fits.open(fitsfile)
    hdr = f[0].header
    if ('m' in hdr.cards['CUNIT3'][1]):
        cube = SpectralCube.read(fitsfile)
    else:
        hdu = change_xaxis_in_velocity(fitsfile)
        cube = SpectralCube.read(hdu)

    
    if window_type != 'velocity':
        window_range = change_to_velocity_ra