[ ]:
%matplotlib inline
Accessing data stored as a table in a multi-extension FITS (MEF) file¶
The example uses astropy.utils.data
to download multi-extension FITS (MEF) file, astropy.io.fits
to investigate the header, and astropy.table.Table
to explore the data.
By: Lia Corrales, Adrian Price-Whelan, and Kelle Cruz License: BSD¶
Use astropy.utils.data
subpackage to download the FITS file used in this example. Also import ~astropy.table.Table
from the astropy.table
subpackage and astropy.io.fits
[2]:
from astropy.utils.data import get_pkg_data_filename
from astropy.table import Table
from astropy.io import fits
Download a FITS file
[5]:
event_filename = get_pkg_data_filename('tutorials/FITS-tables/chandra_events.fits') # filename('/data/ROSAT.fits')
Display information about the contents of the FITS file.
[6]:
fits.info(event_filename)
Filename: C:\Users\Kurt\.astropy\cache\download\py3\26e9900d731d08997d99ada3973f4592
No. Name Ver Type Cards Dimensions Format
0 PRIMARY 1 PrimaryHDU 30 ()
1 EVENTS 1 BinTableHDU 890 483964R x 19C [1D, 1I, 1I, 1J, 1I, 1I, 1I, 1I, 1E, 1E, 1E, 1E, 1J, 1J, 1E, 1J, 1I, 1I, 32X]
2 GTI 3 BinTableHDU 28 1R x 2C [1D, 1D]
3 GTI 2 BinTableHDU 28 1R x 2C [1D, 1D]
4 GTI 1 BinTableHDU 28 1R x 2C [1D, 1D]
5 GTI 0 BinTableHDU 28 1R x 2C [1D, 1D]
6 GTI 6 BinTableHDU 28 1R x 2C [1D, 1D]
Extension 1, EVENTS, is a Table that contains information about each X-ray photon that hit Chandra’s HETG-S detector.
Use ~astropy.table.Table
to read the table
[7]:
events = Table.read(event_filename, hdu=1)
Print the column names of the Events Table.
[8]:
print(events.columns)
<TableColumns names=('time','ccd_id','node_id','expno','chipx','chipy','tdetx','tdety','detx','dety','x','y','pha','pha_ro','energy','pi','fltgrade','grade','status')>
If a column contains unit information, it will have an associated astropy.units
object.
[9]:
print(events['energy'].unit)
eV
Print the data stored in the Energy column.
[10]:
print(events['energy'])
energy
eV
---------
13874.715
2621.1938
12119.018
3253.0364
14214.382
1952.7239
3267.5334
3817.0366
2252.7295
6154.1094
...
4819.8286
12536.866
2599.5652
15535.768
6653.0815
14362.482
14653.954
6652.827
9672.882
1875.9359
Length = 483964 rows
[ ]: