Kron photometry is determined from the observed (smoothed) profile of each Detection. A Kron radius is determined for all objects, irrespective of whether they are point sources or not, and the total magnitude is inferred from the growth curve (enclosed flux vs. radius).
The starting point for the PS1 data archive is at The Pan-STARRS1 data archive home page.
Look up the formal definition (Kron 1980, ApJS 43, 305). The paper shows how to define a nominal magnitude for an extended object on the basis of the shape of the light profile.
In the PanSTARRS implementation, the definition of the Kron radius and Kron magnitude is carried out as follows (from the PS1 guide (Kron Parameters) [PS1 wiki login required]:
Please note that no attempt has been made to correct the reported Kron fluxes/magnitudes to total fluxes/magnitudes. A profile dependent correction is required for this (see the original Kron (1980) definition).
Kron parameters are listed in several different tables, depending on their origin (warp images, stack images, mean values, etc.) The PS1: MeanObject table fields table includes:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
gMeanKronMag | AB magnitudes | REAL | 4 | -999 | Mean Kron (1980) magnitude from g filter detections. |
gMeanKronMagErr | AB magnitudes | REAL | 4 | -999 | Error in mean Kron (1980) magnitude from g filter detections. |
gMeanKronMagStd | AB magnitudes | REAL | 4 | -999 | Standard deviation of Kron (1980) magnitudes from g filter detections. |
gMeanKronMagNpt | dimensionless | SMALLINT | 2 | -999 | Number of measurements included in mean Kron (1980) magnitude from g filter detections. |
and similar entries in the same row for rizy filters.
StackObjectThin contains:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
gKronMag | AB magnitudes | REAL | 4 | -999 | Kron (1980) magnitude from g filter stack detection |
gKronMagErr | AB magnitudes | REAL | 4 | -999 | Error in Kron (1980) magnitude from g filter stack detection. |
and similar entries in the same row for rizy filters.
StackObjectAttributes contains:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
gKronFlux | Janskys | REAL | 4 | -999 | Kron (1980) flux from g filter stack detection. |
gKronFluxErr | Janskys | REAL | 4 | -999 | Error in Kron (1980) flux from g filter stack detection. |
gKronRad | arcsec | REAL | 4 | -999 | Kron (1980) radius from g filter stack detection. |
and similar entries in the same row for rizy filters.
ForcedMeanObject contains:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
gFKronFlux | Janskys | REAL | 4 | -999 | Mean Kron (1980) flux from forced single epoch g filter detections. |
gFKronFluxErr | Janskys | REAL | 4 | -999 | Error in mean Kron (1980) flux from forced single epoch g filter detections. |
gFKronFluxStd | Janskys | REAL | 4 | -999 | Standard deviation of Kron (198) fluxes from forced single epoch g filter detections. |
gFKronMag | AB magnitudes | REAL | 4 | -999 | Magnitude from mean Kron (1980) flux from forced single epoch g filter detections. |
gFKronMagErr | AB magnitudes | REAL | 4 | -999 | Error in magnitude from mean Kron (1980) flux from forced single epoch g filter detections. |
and similar entries in the same row for rizy filters.
The tables below with multi-epoch measurements are not included in the DR1 database but are included here for completeness.
PS1: Detection table fields contains:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
kronFlux | Janskys | REAL | 4 | -999 | Kron (1980) flux. |
kronFluxErr | Janskys | REAL | 4 | -999 | Error on Kron (1980) flux. |
kronRad | arcsec | REAL | 4 | -999 | Kron (1980) radius. |
ForcedWarpMeasurement contains:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
FkronFlux | Janskys | REAL | 4 | -999 | Kron (1980) flux. |
FkronFluxErr | Janskys | REAL | 4 | -999 | Error in Kron (1980) flux. |
FkronRad | arcsec | REAL | 4 | -999 | Kron (1980) radius. |
DiffDetection contains:
Name | Unit | Data Type | Size | Default Value | Description |
---|---|---|---|---|---|
DkronFlux | Janskys | REAL | 4 | -999 | Kron (1980) flux. |
DkronFluxErr | Janskys | REAL | 4 | -999 | Error in Kron (1980) flux. |
DkronRad | arcsec | REAL | 4 | -999 | Kron (1980) radius. |
Most of the information contained here is based on the PS1 Guide http://ps1sc.ifa.hawaii.edu/PS1wiki/index.php/PS1Guide#Kron_parameters (requires PS1 wiki login). Information on the contents of the Table was obtained from the PSPS Schema Browser.
The original definitions presumably are from Kron (1980): http://adsabs.harvard.edu/abs/1980PhyS...21..652K
A modern implementation is described, e.g., for 2MASS at: http://www.ipac.caltech.edu/2mass/releases/allsky/doc/sec4_5e.html.
Put one or more images or figures at the top of this column. Novices may simply "Insert" an "Image" here. Experts should create first go to the "Media Repository" page and "Create" a new "PS1 image information" page for the new image. The image information page provide a mechanism for capturing metadata and including alternate versions of the figure.
Include an infobox below the picture. Summarize key facts in the infobox. The infobox helps users quickly assess the content of the article.
|