AC47 · Light, images and selection
From distant light to a galaxy census
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.
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.
02 · L2How 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.
03 · L1Why a galaxy drops out of one filter
Move an absorption boundary through four actual passbands to understand intergalactic gas, photon weighting and dropout selection.
04 · L2Why 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.
05 · L2What 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.
06 · L3Replay 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.
07 · L4Does 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.
Primary sources and calculation notes
- Steidel et al. (1996), Spectroscopic confirmation of a population of normal star-forming galaxies at redshifts above three
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.
- Hogg (1999), Distance measures in cosmology
Luminosity-distance section: bolometric flux, angular/luminosity distance and spectral-density transformations. The numerical examples use the explicitly adopted radiation-free model.
- Hogg, Baldry, Blanton & Eisenstein (2002), The K correction
Equations 1–7 and the AB-reference definition. Keep emitted and observed frequency arguments distinct; the tutorial fixes its reference to 3631 Jy.
- STScI, NIRCam filters and mean system throughput
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.
- STScI synphot, Photometric properties
Bandpass weighting and the pivot-wavelength definition; a pivot is a property of the bandpass and does not replace a weighted source integral.
- Inoue et al. (2014), An updated analytic model for attenuation by the intergalactic medium
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.
- Photutils, PSF photometry
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.
- Sandbox Physics, finite physical-model checks
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.
- Sandbox Physics, specified synthetic imaging examples
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.
- Sandbox Physics, frozen synthetic response checks
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.
- Sandbox Physics, selected-only inference checks
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.
- Sandbox Physics, selected-count cold replay
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.
- SciPy, Poisson probability and logpmf
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.
- Curtis-Lake et al., JADES DR4 Paper I, v2
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.
- JADES DR4, twelve original-class fact rows
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.
- Sandbox Physics, conditional JADES volume cold replay
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.
- Madau & Dickinson (2014), Cosmic Star-Formation History
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.
- Juodžbalis et al. (2025), JADES broad-line AGN census, v2
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.
- Shuntov et al. (2025), COSMOS-Web stellar mass assembly, A&A 695, A20
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.
- Sandbox Physics, explicit stellar-reading scalar examples
Original AB-normalization, declared UV-to-rate conversion, screen/fraction and assumed-mass efficiency arithmetic only. No SPS, stellar-mass fit or new observations.