FITS source list formats

There are three supported fits file formats:

LoBES: used in LoBES catalogue https://doi.org/10.1017/pasa.2021.50
Jack: extended LoBES format for Jack Line's sourcelist repository, https://github.com/JLBLine/srclists/.
Gleam: used in GLEAM-X pipeline https://github.com/GLEAM-X/GLEAM-X-pipeline/tree/master/models

These formats differ mostly in the names of columns, and component and flux types supported. LoBES fits files support point, and Gaussian components with list, power law and curved power law flux density models. Jack fits files extend the LoBES format with an additional table for shapelet coefficients. Gleam fits are similar to LoBES fits, but with different column names, and combine power law and curved power law flux density models into a just two columns.

More info from woden docs

Source posititons

Coordinates are right ascension (RA) and declination, both with units of degrees in the J2000 epoch. All frequencies are in Hz and all flux densities are in Jy.

Jack and LoBES fits formats use the columns RA and DEC for source positions, while Gleam fits files use RAJ2000 and DEJ2000.

Component types

Jack and LoBES fits formats use the column COMP_TYPE for component types:

P for point
G for Gaussian
S for shapelet (Jack only)

Jack and LoBES fits formats use the columns MAJOR_DC, MINOR_DC and PA_DC for Gaussian component sizes and position angles (in degrees), while Gleam fits files use a, b (arcseconds) and pa (degrees).

In an image space where RA increases from right to left (i.e. bigger RA values are on the left), position angles rotate counter clockwise. A position angle of 0 has the major axis aligned with the declination axis.

Flux density models

Jack and LoBES fits formats use the column MOD_TYPE for flux density types:

pl for power law
cpl for curved power law
nan for lists

Jack and LoBES fits formats use the columns NORM_COMP_PL and ALPHA_PL for power law flux density normalisation and spectral index; and NORM_COMP_CPL, ALPHA_CPL and CURVE_CPL for curved power law flux density normalisation, while Gleam fits files use S_200, alpha and beta.

A reference frequency of 200MHz is assumed in all fits files.

Jack and LoBES fits formats use the columns INT_FLXnnn for integrated flux densities in Jy at frequencies nnn MHz, while Gleam fits files use only s_200. These columns are used to construct flux lists if power law information is missing, or MOD_TYPE is nan.

Only Stokes I can be specified in fits sourcelists, Stokes Q, U and V are assumed to have values of 0.

Examples

Example Python code to display these files is in the examples directory.

e.g. python examples/read_fits_srclist.py test_files/jack.fits

UNQ_SOURCE_ID	NAME	RA	DEC	INT_FLX100	INT_FLX150	INT_FLX200	MAJOR_DC	MINOR_DC	PA_DC	MOD_TYPE	COMP_TYPE	NORM_COMP_PL	ALPHA_PL	NORM_COMP_CPL	ALPHA_CPL	CURVE_CPL
point-list	point-list_C0	0	1	3	2	1	0	0	0	nan	P	1	0	0	0	0
point-pl	point-pl_C0	1	2	3.5	2.5	2	0	0	0	pl	P	2	-0.8	0	0	0
point-cpl	point-cpl_C0	3	4	5.6	3.8	3	0	0	0	cpl	P	0	0	3	-0.9	0.2
gauss-list	gauss-list_C0	0	1	3	2	1	20	10	75	nan	G	1	0	0	0	0
gauss-pl	gauss-pl_C0	1	2	3.5	2.5	2	20	10	75	pl	G	2	-0.8	0	0	0
gauss-cpl	gauss-cpl_C0	3	4	5.6	3.8	3	20	10	75	cpl	G	0	0	3	-0.9	0.2
shape-pl	shape-pl_C0	1	2	3.5	2.5	2	20	10	75	pl	S	2	-0.8	0	0	0
shape-pl	shape-pl_C1	1	2	3.5	2.5	2	20	10	75	pl	S	2	-0.8	0	0	0

NAME	N1	N2	COEFF
shape-pl_C0	0	0	0.9
shape-pl_C0	0	1	0.2
shape-pl_C0	1	0	-0.2
shape-pl_C1	0	0	0.8

e.g. python examples/read_fits_srclist.py test_files/gleam.fits

Name	RAJ2000	DEJ2000	S_200	alpha	beta	a	b	pa
point-pl	1	2	2	-0.8	0	0	0	0
point-cpl	3	4	3	-0.9	0.2	0	0	0
gauss-pl	1	2	2	-0.8	0	72000	36000	75
gauss-cpl	3	4	3	-0.9	0.2	72000	36000	75

these are both equivalent to the following YAML file (ignoring shapelets and lists for the gleam example):

point-list:
- ra: 0.0
  dec: 1.0
  comp_type: point
  flux_type:
    list:
    - freq: 100000000.0
      i: 3.0
    - freq: 150000000.0
      i: 2.0
    - freq: 200000000.0
      i: 1.0
point-pl:
- ra: 1.0
  dec: 2.0
  comp_type: point
  flux_type:
    power_law:
      si: -0.8
      fd:
        freq: 200000000.0
        i: 2.0
point-cpl:
- ra: 3.0000000000000004
  dec: 4.0
  comp_type: point
  flux_type:
    curved_power_law:
      si: -0.9
      fd:
        freq: 200000000.0
        i: 3.0
      q: 0.2
gauss-list:
- ra: 0.0
  dec: 1.0
  comp_type:
    gaussian:
      maj: 72000.0
      min: 36000.0
      pa: 75.0
  flux_type:
    list:
    - freq: 100000000.0
      i: 3.0
    - freq: 150000000.0
      i: 2.0
    - freq: 200000000.0
      i: 1.0
gauss-pl:
- ra: 1.0
  dec: 2.0
  comp_type:
    gaussian:
      maj: 72000.0
      min: 36000.0
      pa: 75.0
  flux_type:
    power_law:
      si: -0.8
      fd:
        freq: 200000000.0
        i: 2.0
gauss-cpl:
- ra: 3.0000000000000004
  dec: 4.0
  comp_type:
    gaussian:
      maj: 72000.0
      min: 36000.0
      pa: 75.0
  flux_type:
    curved_power_law:
      si: -0.9
      fd:
        freq: 200000000.0
        i: 3.0
      q: 0.2
shape-pl:
- ra: 1.0
  dec: 2.0
  comp_type:
    shapelet:
      maj: 72000.0
      min: 36000.0
      pa: 75.0
      coeffs:
      - n1: 0
        n2: 0
        value: 0.9
      - n1: 0
        n2: 1
        value: 0.2
      - n1: 1
        n2: 0
        value: -0.2
  flux_type:
    power_law:
      si: -0.8
      fd:
        freq: 200000000.0
        i: 2.0
- ra: 1.0
  dec: 2.0
  comp_type:
    shapelet:
      maj: 72000.0
      min: 36000.0
      pa: 75.0
      coeffs:
      - n1: 0
        n2: 0
        value: 0.8
  flux_type:
    power_law:
      si: -0.8
      fd:
        freq: 200000000.0
        i: 2.0

mwa_hyperdrive documentation

FITS source list formats

Source posititons

Component types

Flux density models

Examples