CHAR-SURV-001: Depth¶
Parent requirement¶
Cadence¶
Once, during PV phase.
Objective¶
At the end of PV phase, we need to decide whether the survey can start as planned. Crucial in this respect is whether the required survey depths and number counts are met for Euclid’s principal weak lensing and galaxy clustering experiments. While number counts are subject to cosmic variance, a single pass of the full EDF-N and - if visible - the EDF-S will be sufficient.
Observations¶
Methodology / Uplink procedure¶
Targets and pointing constraints¶
Instrument configuration¶
Inter-operability constraints¶
Dependencies¶
Fulfilling¶
Fulfilled by¶
Time-critical¶
No
Validation¶
None.
Recovery¶
None.
In-orbit duration¶
Processing time¶
Processing input¶
Ground Processing Input Data:
Data Description:
Data volume¶
Processing tools¶
Standard wide survey processing
Processing element¶
DataModel: https://gitlab.euclid-sgs.uk/
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Required accuracy, constraints¶
Processing method¶
Processing output¶
The EDF-N is covered by 43 executions of the ROS. Possibly, we can also cover the EDF-S and / or EDF-F. These observations provide sufficient data to test top level requirements for the mission:
Imaging survey depth, using flux limits and number counts:
For VIS, a number counts histogram must be computed for \({\rm SNR}\geq 10\) extended sources (at least 1.25 times the FWHM of the PSF), and compared to the minimum target depth of 24.5 AB mag. This is a direct compliance check against MRD-WS-001. The number density of galaxies with fluxes \(\geq 24.5\) AB mag shall exceed \(30\;{\rm arcmin}^{-2}\) (SciRD R-WL.1-2).
For NISP, number counts histograms must be computed for all three bands for \({\rm SNR}\geq 5\) point sources, and compared to the minimum target depth of 24.0 AB mag. This checks compliance against MRD-WS-002. This requires absolute photometric calibration, or the direct comparison with sources of known magnitudes in the field, such as the JWST PEARLS NEP-TDF field.
Spectroscopic survey depth, using line flux limits and number counts:
Plot the mean SNR of the \({\rm H}\alpha\) line for sources where this line falls between \(1500-1700\) nm, as a function of line flux. At \(2\times10^{-16}{\rm \;erg\;cm^{-2}\;s^{-1}}\), we should have \({\rm SNR}\geq 3.5\) (MRD-GC-001).
Determine the number density of \({\rm H}\alpha\) emitters with fluxes \(\geq 2\times10^{-16}{\rm \;erg\;cm^{-2}\;s^{-1}}\), in the redshift range \(z=0.9-1.8\). Ideally, it should exceed \(1700\;{\rm deg}^{-2}\) (SciRD R-GC.1-2; note that the SciRD is not binding).
Given the number of NISP-S blue and red grism spectra taken in PV in the EDF-N, can we expect to reach 120,000 galaxies with at least 99% purity (R-CAL-A-NS-4000)? This would require a model of the line-emitter density as a function of depth.
Contact person¶
Calibration Lead
Status¶
2026/09/18 - In progress.
Comments¶