---
title: "From distant light to a galaxy census"
description: "Follow UV light through filters, pixels and selected counts, replay a conditional JADES volume, then examine stellar and AGN interpretations."
canonical_url: "https://sandboxphysics.com/stories/high-redshift-galaxies/"
language: "en"
page_type: "story"
alternate_languages:
  zh-CN: "https://sandboxphysics.com/zh/stories/high-redshift-galaxies/"
last_modified: "2026-11-12"
---

AC47 · Light, images and selection

# From distant light to a galaxy census

Sandbox Physics · 2026-11-12

A missing blue band can point to a distant galaxy. Follow its light into noisy pixels and a selected count, recompute a bounded real JADES example, then ask what more is needed to infer stars and their formation.

[01 · L1 How distant light becomes a galaxy count Follow early colour-selected galaxies through Keck spectroscopy, then see how infrared filters and finite noisy pixels shape a census.](https://sandboxphysics.com/stories/high-redshift-galaxies/far-light-to-a-count/) [02 · L2 How redshift turns UV luminosity into received flux Derive the frequency-density redshift factor, define the AB reference and work a checkable high-redshift flux example.](https://sandboxphysics.com/stories/high-redshift-galaxies/redshift-ab-and-spectral-density/) [03 · L1 Why a galaxy drops out of one filter Move an absorption boundary through four actual passbands to understand intergalactic gas, photon weighting and dropout selection.](https://sandboxphysics.com/stories/high-redshift-galaxies/why-a-filter-drops-out/) [04 · L2 Why spreading the same galaxy light makes it harder to measure Derive finite pixels and a known-profile flux estimate, then distinguish source-size losses from blind-search completeness.](https://sandboxphysics.com/stories/high-redshift-galaxies/size-pixels-and-known-source-recovery/) [05 · L2 What can twenty-six selected sources tell us about a population? Build the response for missed and migrating sources, then derive a selected-count Poisson fit and its full slope profile.](https://sandboxphysics.com/stories/high-redshift-galaxies/selection-response-and-selected-counts/) [06 · L3 Replay a conditional JADES volume for three real sources Extract twelve original-class facts and recompute one bright redshift slice, retaining its selection conditions and actual mismatches.](https://sandboxphysics.com/stories/high-redshift-galaxies/replay-a-conditional-jades-volume/) [07 · L4 Does bright UV light imply efficient star formation? Read how stellar populations, AGN spectra and galaxy–halo modelling turn light into a rate, a mass and an efficiency.](https://sandboxphysics.com/stories/high-redshift-galaxies/from-uv-light-to-stars-and-black-holes/)

## Primary sources and calculation notes

1. [Steidel et al. (1996), Spectroscopic confirmation of a population of normal star-forming galaxies at redshifts above three](https://arxiv.org/pdf/astro-ph/9602024v1)

   Sections 2–3 and Figure 1: October 1995 Keck/LRIS spectra, colour-selected candidates and the listed spectroscopic galaxy redshifts. No new reconciliation of the paper’s candidate denominators or LF estimate.

2. [Hogg (1999), Distance measures in cosmology](https://ned.ipac.caltech.edu/level5/Hogg/Hogg7.html)

   Luminosity-distance section: bolometric flux, angular/luminosity distance and spectral-density transformations. The numerical examples use the explicitly adopted radiation-free model.

3. [Hogg, Baldry, Blanton & Eisenstein (2002), The K correction](https://arxiv.org/pdf/astro-ph/0210394v1)

   Equations 1–7 and the AB-reference definition. Keep emitted and observed frequency arguments distinct; the tutorial fixes its reference to 3631 Jy.

4. [STScI, NIRCam filters and mean system throughput](https://jwst-docs.stsci.edu/jwst-near-infrared-camera/nircam-instrumentation/nircam-filters)

   Four frozen v7 detector-averaged total-system tables: F115W, F150W, F200W and F277W. Original table URLs and SHA256 identities accompany the numerical examples. Throughput is distinct from a PSF or an exposure/noise calibration.

5. [STScI synphot, Photometric properties](https://synphot.readthedocs.io/en/latest/synphot/formulae.html)

   Bandpass weighting and the pivot-wavelength definition; a pivot is a property of the bandpass and does not replace a weighted source integral.

6. [Inoue et al. (2014), An updated analytic model for attenuation by the intergalactic medium](https://arxiv.org/pdf/1402.0677v4)

   Introduction and Section 3.1/Figure 5: intergalactic hydrogen and mean Lyman-alpha transmission. The controlled example uses a separate sharp 1216-Angstrom cutoff, not this paper’s full attenuation calculation.

7. [Photutils, PSF photometry](https://docs.astropy.org/projects/photutils/en/stable/user_guide/psf.html)

   Finding sources, fixing supplied positions, fitting pixel-integrated profiles and grouping blends. Used to explain why source finding and a known-position flux estimate are different operations.

8. [Sandbox Physics, finite physical-model checks](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/model-commission-summary.json)

   Actual 58 finite checks: matched Astropy cosmology, scalar/adaptive photon integrals, finite Gaussian pixels and four 1024-acquisition white-noise tests. Those statistical tests use 0.05 nJy per pixel; the saved five imaging examples use 0.15 nJy.

9. [Sandbox Physics, specified synthetic imaging examples](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/model-numerical-examples.json)

   Original synthetic examples with exact parameters, distances, native-band totals and saved noisy measurements. No observed galaxy catalog, foreign source ZIP, executable Engine or measured cosmic LF is included.

10. [Sandbox Physics, frozen synthetic response checks](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/statistical-model-checks.json#response)

    Original 25-gate response record, including response refinement, finite Gaussian recovery and separate public-catalog count-identity checks. Its fixed source conditions do not calibrate a real survey.

11. [Sandbox Physics, selected-only inference checks](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/statistical-model-checks.json#inference)

    Accepted 18-gate inference result: independent likelihood, optimum and scores. The first failed original attempt remains historical evidence; the public package uses only the accepted source and selected observations.

12. [Sandbox Physics, selected-count cold replay](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/selected-counts-replay.zip)

    Complete nine-row/six-column calibration at two orders, eight selected counts, six unequal intrinsic bins, original numerical functions and all 401 profile points. Actual cold replay: 39 checks. No hidden parent truth or new draws.

13. [SciPy, Poisson probability and logpmf](https://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.poisson.html)

    Probability mass function, nonnegative integer support and zero-mean case. The actual independent cold runs fix SciPy 1.17.1; documentation access does not update the execution environment.

14. [Curtis-Lake et al., JADES DR4 Paper I, v2](https://arxiv.org/html/2510.01033v2)

    Version dated 7 May 2026. Target-read Sections 2.4/3.3/4.5/5, Tables 2/4/10 and equations 1–3. Retain original classes, optimized pointings and the distinction between original selection and updated gold samples.

15. [JADES DR4, twelve original-class fact rows](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/original-jades-class-facts.csv)

    Small attributed numerical extract from the exact Combined\_DR4\_external\_v1.2.1.fits Obs\_info audit. Original catalog URL/SHA, table conditions and source terms are inside the conditional replay package. No full FITS redistribution.

16. [Sandbox Physics, conditional JADES volume cold replay](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/conditional-jades-volume-replay.zip)

    Twelve fact rows, attributed Table 2/4 conditions, original volume functions, all seven horizon checks and retained model-cut/Table 10 mismatches. Actual cold replay 62 checks; conditional target-class scope, not cosmic-average LF.

17. [Madau & Dickinson (2014), Cosmic Star-Formation History](https://ned.ipac.caltech.edu/level5/March14/Madau/Madau3.html)

    Sections 3/3.1.1, Figures 2–4 and equation 10: ages, stellar initial mass functions and conditional UV conversion. The illustrative coefficient 1.3e−28 uses constant formation, solar metallicity, age at least about 300 Myr and Salpeter 0.1–100 solar masses; it is distinct from their evolving-population 1.15 choice.

18. [Juodžbalis et al. (2025), JADES broad-line AGN census, v2](https://arxiv.org/pdf/2504.03551v2)

    Version 29 April 2025; Figure 1, Section 5.2, Figure 4 and Tables 3–4. Read broad/narrow spectra, nuclear/stellar decomposition, aperture assumptions and compared host-mass routes. No AGN fraction is transferred to the redshift-ten synthetic source; no mass fit is replayed.

19. [Shuntov et al. (2025), COSMOS-Web stellar mass assembly, A&A 695, A20](https://doi.org/10.1051/0004-6361/202452570)

    Publisher version of record read via DTU Orbit: Sections 2.2/3.2–3.3/6.6 and Figures 1/10/11. Follow population modelling, completeness/AGN handling and simple abundance matching. The baryon fraction is an explicit separate assumption in the scalar example, not a reconstruction of these curves.

20. [Sandbox Physics, explicit stellar-reading scalar examples](https://sandboxphysics.com/stories/high-redshift-galaxies/materials/stellar-reading-scalar-examples.json)

    Original AB-normalization, declared UV-to-rate conversion, screen/fraction and assumed-mass efficiency arithmetic only. No SPS, stellar-mass fit or new observations.