It is possible to run source-finding with Selavy on the created spectral-line cubes. Through the pipeline, it is possible to specify either flux or SNR thresholds, apply a variable SNR threshold, and pre-process the cube with smoothing or multi-resolution wavelet reconstruction (to enhance the signal-to-noise of real sources).
| Variable | Default | Parset equivalent | Description |
|---|---|---|---|
| DO_SOURCE_FINDING_SPEC | "" | none | Whether to do the source-finding with Selavy on the final mosaic images. If not given in the config file, it takes on the value of DO_SPECTRAL_IMAGING. |
| DO_SOURCE_FINDING_BEAMWISE | false | none | If true, the source-finding will be run on the individual beam images as well. |
| DO_SOURCE_FINDING_FIELD_MOSAICS | false | none | If true, the source-finding will be run on the individual field mosaics. Will be set to false if the number of fields is one. |
| JOB_TIME_SOURCEFINDING_SPEC | JOB_TIME_DEFAULT (24:00:00) | none | Time request for source-finding jobs |
| CPUS_PER_CORE_SELAVY_SPEC | "" | none | Number of cores used on each node. If not provided, it will be the lower of the number of cores requested or the maximum number of cores available per node. |
| SELAVY_SPEC_NSUBX | 6 | nsubx (Selavy Basics) | Number of divisions in the x-direction that divide the image up, allowing parallel processing in the source-detection. |
| SELAVY_SPEC_NSUBY | 9 | nsuby (Selavy Basics) | Number of divisions in the y-direction that divide the image up, allowing parallel processing in the source-detection. |
| SELAVY_SPEC_NSUBZ | 18 | nsubz (Selavy Basics) | Number of divisions in the z-direction that divide the image up, allowing parallel processing in the source-detection. |
| SELAVY_OVERLAPX | 0 | overlapx (Selavy Basics) | The overlap (in pixels) between neighbouring divisions in the x-direction. |
| SELAVY_OVERLAPY | 0 | overlapy (Selavy Basics) | The overlap (in pixels) between neighbouring divisions in the y-direction. |
| SELAVY_OVERLAPZ | 20 | overlapz (Selavy Basics) | The overlap (in pixels) between neighbouring divisions in the z-direction. |
| Searching | |||
| SELAVY_SPEC_SNR_CUT | 8.0 | snrcut (Selavy Basics) | The signal-to-noise ratio threshold to use in the source-detection. |
| SELAVY_SPEC_FLAG_GROWTH | true | flagGrowth (Selavy Basics) | A flag indicating whether to grow detections down to a lower threshold. |
| SELAVY_SPEC_GROWTH_CUT | 3.0 | growthCut (Selavy Basics) | The secondary signal-to-noise threshold to which detections should be grown. |
| SELAVY_SPEC_FLUX_THRESHOLD | "" | threshold (Selavy Basics) | The flux threshold to use in the source-detection. If left blank, we use the SNR threshold SELAVY_SNR_CUT. |
| SELAVY_SPEC_GROWTH_THRESHOLD | "" | growthCut (Selavy Basics) | The secondary signal-to-noise threshold to which detections should be grown. Only used if SELAVY_FLUX_THRESHOLD is given. |
| SELAVY_SPEC_WEIGHTS_CUTOFF | "" | Weights.weightsCutoff (Thresholds in Selavy) | The cutoff level, as a fraction of the peak in the weights image, used in the source-finding. Only applies if the image being searched has a corresponding weights image. If not given, the value used is the square of LINMOS_CUTOFF from User Parameters - Mosaicking. |
| SELAVY_SPEC_SEARCH_TYPE | spatial | searchType (Selavy Basics) | Type of searching to be performed: either ‘spectral’ (searches are done in each 1D spectrum) or ‘spatial’ (searches are done in each 2D channel image). Anything else defaults to spectral. |
| SELAVY_SPEC_VARIABLE_THRESHOLD | true | VariableThreshold (Thresholds in Selavy) | A flag indicating whether to determine the signal-to-noise threshold on a pixel-by-pixel basis based on local statistics (that is, the statistics within a relatively small box centred on the pixel in question). The dimensions of the box are governed by the search type - if ‘spectral’ then it will be a one-dimensional box slid along each spectrum, else if ‘spatial’ it will be a 2D box done on each channel image. |
| SELAVY_SPEC_BOX_SIZE | 35 | VariableThreshold.boxSize (Thresholds in Selavy) | The half-width of the sliding box used to determine the local statistics. |
| SELAVY_SPEC_MIN_PIX | 5 | minPix (Selavy Basics) | Minimum number of (spatial) pixels allowed in a detection |
| SELAVY_SPEC_MIN_CHAN | 5 | minChan (Selavy Basics) | Minimum number of channels allowed in a detection |
| SELAVY_SPEC_MAX_CHAN | 2592 | maxChan (Selavy Basics) | Maximum number of channels allowed in a detection |
| Pre-processing | |||
| SELAVY_SPEC_FLAG_SMOOTH | true | flagSmooth (Preprocessing for Selavy) | Whether to smooth the input cube prior to searching. |
| SELAVY_SPEC_SMOOTH_TYPE | spectral | smoothType (Preprocessing for Selavy) | Type of smoothing to perform - either ‘spectral’ or ‘spatial’. Anything else defaults to spectral. |
| SELAVY_SPEC_HANN_WIDTH | 5 | hanningWidth (Preprocessing for Selavy) | The width of the Hanning spectral smoothing kernel. |
| SELAVY_SPEC_SPATIAL_KERNEL | 3 | kernMaj, kernMin, kernPA (Preprocessing for Selavy) | The specs for the spatial Gaussian smoothing kernel. Either a single number, which is interpreted as a circular Gaussian (kernMaj=kernMin, kernPA=0), or a string with three values enclosed by square brackets (eg. "[4,3,45]"), interpreted as “[kernMaj,kernMin,kernPA]”. |
| SELAVY_SPEC_FLAG_WAVELET | false | flagAtrous (Preprocessing for Selavy) | Whether to use the multi-resolution wavelet reconstruction. |
| SELAVY_SPEC_RECON_DIM | 1 | reconDim (Preprocessing for Selavy) | The number of dimensions in which to perform the reconstruction. 1 means reconstruct each spectrum separately, 2 means each channel map is done separately, and 3 means do the whole cube in one go. |
| SELAVY_SPEC_RECON_SNR | 4 | snrRecon (Preprocessing for Selavy) | Signal-to-noise threshold applied to wavelet arrays prior to reconstruction. |
| SELAVY_SPEC_RECON_SCALE_MIN | 1 | scaleMin (Preprocessing for Selavy) | Minimum wavelet scale to include in reconstruction. A value of 1 means “use all scales”. |
| SELAVY_SPEC_RECON_SCALE_MAX | 0 | scaleMax (Preprocessing for Selavy) | Maximum wavelet scale to use in the reconstruction. If 0 or negative, then the maximum scale is calculated from the size of the array. |
| Pre-processing | |||
| SELAVY_SPEC_OPTIMISE_MASK | false | optimiseMask (Post-processing of detections) | Whether to improve the mask of detected sources prior to parameterisation via the mask optimisation technique. |