Description
Compare supplied nonnegative source and lens redshifts.
Cosmological quantities depend on scale factor, redshift, distance definition and the dimensionless Hubble parameter h. Proper and comoving distances differ at a specified epoch, and h-scaled units differ from the dimensional Hubble constant. A scalar rescaling or model contribution preserves supplied conventions without fitting a cosmology or inferring an observed distance.
Compare supplied nonnegative source and lens redshifts.
When to use this tool
Use Source Redshift Behind Lens Flag when you already have sourceRedshift, lensRedshift and need to compare supplied nonnegative source and lens redshifts.
How to use the tool and how it works
- Enter sourceRedshift, lensRedshift. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read sourceBehindLensByRedshift, difference. Inspect sourceBehindLensByRedshift before interpreting the associated values.
Require both redshifts>=0; return source>lens and source-lens.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| sourceRedshift | Source Redshift | Required. Finite number; minimum 0. |
| lensRedshift | Lens Redshift | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| sourceBehindLensByRedshift | Source Behind Lens By Redshift | Required. Boolean. |
| difference | Difference | Required. Finite number. |
{
"input": {
"sourceRedshift": 2,
"lensRedshift": 0.5
},
"output": {
"sourceBehindLensByRedshift": true,
"difference": 1.5
}
}Limitations and assumptions
- Equality is not behind by this check. Redshift ordering alone does not verify physical geometry, lensing, association or a usable source sample.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the complete cosmological model and its parameter, epoch and unit definitions for a physical inference. Review redshift, distance, lensing and spectrum conventions before combining these local terms; they do not perform line-of-sight integration, parameter estimation or uncertainty analysis.
References
Similar or alternative tools
- Redshift Observation Vs Model Residual
Calculate a supplied observed-minus-modeled redshift residual.
- Redshift Velocity Small Offset Convention
Calculate a small-redshift-offset velocity approximation under supplied conventions.