# job_params.cfg - Job Parameters Configuration¶

The job parameters file provides the detailed, scientifically-motivated settings for each pipeline step. Providing the appropriate configuration here is essential for achieving scientifically valid results.

The default job_params.cfg file is as follows:

[persistence]
description = "TRAP dataset"
dataset_id = -1
#Sigma value used for iterative clipping in RMS estimation:
rms_est_sigma = 4
#Determines size of image subsection used for RMS estimation:
rms_est_fraction = 8

[quality_lofar]
low_bound = 1           ; multiplied with noise to define lower threshold
high_bound = 80         ; multiplied with noise to define upper threshold
oversampled_x = 30      ; threshold for oversampled check
elliptical_x = 2.0      ; threshold for elliptical check
min_separation = 10     ; minimum distance to a bright source (in degrees)

[source_extraction]
# extraction threshold (S/N)
detection_threshold = 8
analysis_threshold = 3
back_size_x = 50
back_size_y = 50
margin = 10
deblend_nthresh = 0 ; Number of subthresholds for deblending; 0 disables
force_beam = False
box_in_beampix = 10
# ew/ns_sys_err: Systematic errors on ra & decl (units in arcsec)
# See Dario Carbone's presentation at TKP Meeting 2012/12/04
ew_sys_err = 10
ns_sys_err = 10

[association]
beamwidths_limit =  1.0

[transient_search]
new_source_sigma_margin = 3


The file follows the standard ConfigParser syntax.

The parameters in this file are defined as follows:

## persistence Section¶

dataset_id
Integer. Specifies the unique ID of a dataset to which the current pipeline run should be appended. If -1, a new dataset is created. If you specify a specific data set ID the configuration of your job is retrieved from the database. This will override your job configuration.
description
String. The name under which the database will be stored in the database. This value is only used if a new dataset is constructed (see dataset_id, below).
rms_est_sigma
Float. Sigma value used for iterative clipping.
rms_est_fraction
Integer. Determines the size of the subsection used for RMS measurement: the central 1/f of the image will be used (where f=rms_est_fraction).

## quality_lofar Section¶

These are the quality-checking parameters applied if the ingested data is from LOFAR. See also Quality check stage.

low_bound
Float. Reject the image if the measured RMS is less than low_bound times the theoretical noise.
high_bound
Float. Reject the image if the measured RMS is greater than high_bound times the theoretical noise.
oversampled_x
The maximum length of a beam axis.
elliptical_x
The maximum ratio of major to minor axis length.
min_separation
The minimum allowed distance from the image centre to a bright radio source in degrees.

## source_extraction Section¶

Parameters used in source extraction. See also “Blind” source extraction stage and Forced source-fitting stage.

detection_threshold
Float. The detection threshold as a multiple of the RMS noise.
analysis_threshold
Float. The analysis threshold as a multiple of the RMS noise.
back_size_x, back_size_y
Integers. The size of the background grid parallel to the X and Y axes of the pixel grid.
margin
Integer. Pixel data within margin pixels of the edge of the image will be excluded from the analysis.
extraction_radius_pix
Integer. Pixel data more than extraction_radius_pix pixels from the centre of the image will be excluded from the analysis.
deblend_nthresh
Integer. The number of subthresholds to use for deblending. Set to 0 to disable deblending.
force_beam
Boolean. If True, all detected sources are assumed to have the size and shape of the restoring beam (ie, to be unresolved point sources), and these parameters are held constant during fitting. If False, all parameters are allowed to vary freely.
box_in_beampix
The size of the masking aperture which determines which pixels are used for forced fitting, as a multiple of the beam major axis length. See tkp.sourcefinder.image.ImageData.fit_to_point() for details.
ew_sys_err, ns_sys_err
Floats. Systematic errors in units of arcseconds which augment the sourcefinder-measured errors on source positions when performing source association. These variables refer to an absolute angular error along an east-west and north-south axis respectively. (NB Although these values are stored during the source-extraction process, they affect the source-association process.)

## association Section¶

Parameters used in source-association. See Source association stage for details. NB the ew_sys_err, ns_sys_err parameters detailed above also affect source-association.

deruiter_radius
Float. Maximum DeRuiter radius for two sources to be considered candidates for association.
beamwidths_limit
Float. Maximum separation for two sources to be considered candidates for association, as a multiple of the restoring-beam semimajor-axis length. Default is 1.0, which was the fixed default prior to TraP release 2.1. It may be necessary to use a larger number if your data has large systematic position errors, i.e. if the sources ‘jitter’ between images, but note that using a large value can cause slowdown of database operations.

## transient_search Section¶

Parameters used in transient-detection. See also the Variability and new-source detection stage.

new_source_sigma_margin
Float. A newly detected source is considered transient if it is significantly above the best (lowest) previous detection limit for that point on-sky. ‘Significantly above’ is defined by a ‘margin of error,’ intended to screen out steady sources that just happen to be fluctuating around the detection threshold due to measurement noise. This value sets that margin as a multiple of the RMS of the previous-best image.