SkyModel Parameters¶
These are the standard attributes of SkyModel objects.
Under the hood they are actually properties based on UVParameter objects.
Angle type attributes also have convenience properties named the same thing with ‘_degrees’ appended through which you can get or set the value in degrees.
Similarly location type attributes (which are given in topocentric xyz coordinates) have convenience properties named the same thing with ‘_lat_lon_alt’ and ‘_lat_lon_alt_degrees’ appended through which you can get or set the values using latitude, longitude and altitude values in radians or degrees and meters.
Required¶
These parameters are required to have a sensible SkyModel object and are required for most kinds of catalog files.
- Ncomponents
Number of components
- Nfreqs
Number of frequencies if spectral_type is ‘full’ or ‘subband’, 1 otherwise.
- coherency_radec
Ra/Dec coherency per component. shape (2, 2, Nfreqs, Ncomponents,)
- component_type
Type of component, options are: ‘healpix’, ‘point’. If component_type is ‘healpix’, the components are the pixels in a HEALPix map in units compatible with K or Jy/sr. If the component_type is ‘point’, the components are point-like sources in units compatible with Jy or K sr. Determines which parameters are required.
- dec
Declination of components in ICRS coordinates. shape (Ncomponents,)
- history
String of history.
- name
Component name, not required for HEALPix maps. shape (Ncomponents,)
- ra
Right ascension of components in ICRS coordinates. shape (Ncomponents,)
- spectral_type
Type of spectral flux specification, options are: ‘full’,’flat’, ‘subband’, ‘spectral_index’.
- stokes
Component flux per frequency and Stokes parameter. Units compatible with one of: [‘Jy’, ‘K sr’, ‘Jy/sr’, ‘K’]. Shape: (4, Nfreqs, Ncomponents).
Optional¶
These parameters are defined by one or more file standard but are not always required. Some of them are required depending on the spectral_type or component_type (as noted below).
- above_horizon
Boolean indicator of whether this source is above the horizon at the current time and location. True indicates the source is above the horizon. shape (Ncomponents,)
- alt_az
Altitude and Azimuth of components in local coordinates. shape (2, Ncomponents)
- beam_amp
Beam amplitude at the source position as a function of instrument polarization and frequency. shape (4, Nfreqs, Ncomponents)
- extended_model_group
Identifier that groups components of an extended source model. Set to an empty string for point sources. shape (Ncomponents,)
- freq_array
Frequency array in Hz, only required if spectral_type is ‘full’ or ‘subband’.
- hpx_inds
Healpix indices, only required for HEALPix maps.
- hpx_order
Healpix pixel ordering (ring or nested). Only required for HEALPix maps.
- nside
Healpix nside, only required for HEALPix maps.
- pos_lmn
Position cosines of components in local coordinates. shape (3, Ncomponents)
- reference_frequency
Reference frequency in Hz, only required if spectral_type is ‘spectral_index’. shape (Ncomponents,)
- spectral_index
Spectral index only required if spectral_type is ‘spectral_index’. shape (Ncomponents,)
- stokes_error
Error on the component flux per frequency and Stokes parameter. The details of how this is calculated depends on the catalog. Units should be equivalent to the units of the stokes parameter. Shape: (4, Nfreqs, Ncomponents).
- telescope_location
Telescope Location for local position calculations.
- time
Time for local position calculations.
last updated: 2021-07-07