Methods
Methods
How a number gets into sim-highline, and what it is allowed to mean. The long form is docs/METHODS.md.
How values enter
Evidence enters through four routes, and every record carries the tier that says which. Counts per tier are on the Data, evidence tiers page.
- Official tables
- Tables released by a collaboration (for example THESAN-1 relation files, Magneticum Box4/uhr tables, the COSMOS-Web mass function). Tier
official-table; the SHA-256 of the file is stored. - Papers
- Fits and tables transcribed from the papers. Tiers
published-table(spot-checked against numbers the paper quotes) andpublished-fit(a fitting function evaluated, not refitted). Transcribed values are never labelledofficial-table. - Compilations
- Machine-readable compilations, pinned to a commit: the SWIFT/VELOCIraptor observational comparison collection and the Sharda et al. 2026 COLIBRE mass–metallicity data release.
- Catalogues
- sim-highline-derived binning of individual-galaxy tables by script, with fixed cuts, bootstrap errors and a fixed seed. Tier
catalog-derived.
Where none of these exists, a curve is read from a published figure (§2): tier digitized-figure, never rankable.
Exact extraction from vector figures
55% of simulation curves are digitized. No raster tracing is used. Figures are taken from the arXiv source of each paper, which almost always holds the figure as vector PDF, EPS or PS. The curves, markers and fill polygons are read from the drawing commands, so values are exact to the coordinate precision of the file.
- Axes are calibrated from the labelled ticks of the same figure: a robust fit over numeric labels snapped to ticks for linear axes; decade labels matched to major ticks and validated against the minor-tick pattern for log axes; calibration translated between shared-axis panels.
- Assertions. Every digitizer asserts its calibration and, where the paper quotes numbers, spot-checks against them. A record never contains a point the figure does not draw; bands come from fill polygons, and points with no drawn error bar have no band.
- Regeneration. Digitizers are deterministic: the shipped records are regenerated exactly by
python3 scripts/regress_digitizers.py. The stored checksum is that of the original figure file.
Definitions travel with the data
Mass aperture, halo definition, IMF, cosmology, population, SFR timescale and statistic, quenching criterion, size definition, metallicity tracer and the like are structured fields on every record, so the comparison flags are computed, not asserted. For each relation, compare.js lists the keys that must match (hard) and those that only warrant a caveat (soft). A pair of records is then one of:
- ✓ comparable
- no blocker and no caveat: every hard and soft key documented and equal
- ~ with caveats
- hard keys documented and equal; a soft key differs or is undocumented, or the two epochs are more than 0.5 apart in z
- ✕ not comparable
- a hard key differs or is undocumented, a curve is marked context only, or structured definitions are missing
What must agree depends on the relation. The rules below are the ones the Explorer and the Your run panel apply, for each of the 44 relations that have records (the code is compare.js, and it is exported as sim-highline-rules.json). A hard definition that differs or is not documented makes two curves not comparable; a soft one makes the comparison carry a caveat. Cosmology is compared as numbers and noted rather than blocked: a different Hubble constant moves masses and volumes by a known amount.
| Relation | Must agree (hard) | Should agree (soft, a caveat if not) |
|---|---|---|
| Stellar mass function | Volume for densities; Which galaxies are included | Initial mass function (IMF); Which stars count toward the mass; Cosmology (H0, matter density) |
| Star-forming main sequence | Which galaxies are included | Initial mass function (IMF); Which stars count toward the mass; Star formation rate averaged over; How the star formation rate is measured; Cosmology (H0, matter density) |
| Specific SFR | Which galaxies are included | Initial mass function (IMF); Which stars count toward the mass; Star formation rate averaged over; How the star formation rate is measured; Cosmology (H0, matter density) |
| Quenched fraction | What counts as quenched | Initial mass function (IMF); Which stars count toward the mass |
| Mass–size | Size definition; Which galaxies are included | Initial mass function (IMF); Which stars count toward the mass |
| Gas-phase O/H | What metallicity means | Metallicity calibration (and solar value); Which galaxies are included; Initial mass function (IMF); Which stars count toward the mass |
| Stellar–halo mass | Halo mass definition | Halo mass: current or peak; Which galaxies are included; Initial mass function (IMF); Which stars count toward the mass |
| Cold gas fraction | Which gas (phase and region) | Which galaxies are included; Initial mass function (IMF) |
| HI gas fraction | Which gas (phase and region) | Mean or median of the gas fraction; How the gas phase is computed or measured; Which galaxies are included; Initial mass function (IMF); Which stars count toward the mass |
| H₂ gas fraction | Which gas (phase and region) | Mean or median of the gas fraction; How the gas phase is computed or measured; Which galaxies are included; Initial mass function (IMF); Which stars count toward the mass |
| Angular momentum | How the specific angular momentum is defined | Which stars count toward the mass; Initial mass function (IMF) |
| Baryonic Tully–Fisher | Which velocity (circular, rotation, maximum) | Which stars count toward the mass |
| Cosmic stellar mass density | Volume for densities | Initial mass function (IMF); Which stars count toward the mass; Cosmology (H0, matter density) |
| Cosmic black hole mass density | Volume for densities | How the black hole mass is obtained; Cosmology (H0, matter density) |
| Stellar metallicity | What metallicity means | Metallicity calibration (and solar value); Initial mass function (IMF); Which stars count toward the mass; Which galaxies are included |
| Stellar age | – | How the stellar age is averaged; Initial mass function (IMF); Which stars count toward the mass; Which galaxies are included |
| HI mass function | Which gas (phase and region); Volume for densities | How the gas phase is computed or measured |
| UV luminosity function | Rest-frame UV band; Volume for densities | Dust correction of the luminosities; Cosmology (H0, matter density) |
| Cosmic SFR density | Volume for densities | Initial mass function (IMF); Star formation rate indicator; Region the SFR density is summed over; Dust correction of the luminosities; Cosmology (H0, matter density) |
| SFR function | Volume for densities | Star formation rate indicator; Initial mass function (IMF); Star formation rate averaged over |
| Cluster gas fraction | Region the quantity is measured within; Baryon fraction the gas fraction is divided by | How the mass is obtained; Which galaxies are included |
| Cosmic metal density | Volume for densities; Metals in gas or in stars | – |
| Dust mass function | Volume for densities | How the dust mass is measured |
| Dust-to-gas ratio | Which gas (phase and region) | – |
| Stellar Tully–Fisher | Which velocity (circular, rotation, maximum) | Initial mass function (IMF) |
| Halo mass function | Halo mass definition; Volume for densities | – |
| Black hole–stellar mass | – | How the black hole mass is obtained; Which stars count toward the mass; Initial mass function (IMF); Which galaxies are included |
| Black hole–dispersion | How the velocity dispersion is defined | How the black hole mass is obtained; Which galaxies are included |
| Fundamental metallicity relation | Mixing parameter of the metallicity relation; What metallicity means | Metallicity calibration (and solar value); Star formation rate indicator; Star formation rate averaged over; Initial mass function (IMF); Which stars count toward the mass; Which galaxies are included |
| Kennicutt–Schmidt law | Which gas (phase and region); Scale the surface densities are measured on | Star formation rate indicator; CO-to-H2 conversion factor; Helium in the gas surface density; Initial mass function (IMF); Which galaxies are included |
| Projected clustering | How the sample is selected; Length unit (with or without h) | Line-of-sight integration limit; Cosmology (H0, matter density) |
| Halo occupation | Central, satellite or all galaxies; Halo mass definition | How the sample is selected |
| Galaxy colour | Which colour (bands); Dust treatment of the colours | Which galaxies are included; Which stars count toward the mass; Initial mass function (IMF) |
| Velocity dispersion–mass | Velocity dispersion: dimension and aperture | How the velocity dispersion is defined; Velocity dispersion weighted by light or mass; Which stars count toward the mass; Initial mass function (IMF); Which galaxies are included; Cosmology (H0, matter density) |
| Central surface density | How the inner surface density is defined | Which stars count toward the mass; Initial mass function (IMF); Which galaxies are included; Cosmology (H0, matter density) |
| Cluster X-ray luminosity–mass | X-ray band; Cluster core included or removed; Halo mass definition | – |
| Cluster SZ signal–mass | Halo mass definition; Redshift scaling of the Compton-Y relation | – |
| AGN luminosity function | Luminosity band; Luminosity function convention; Volume for densities | Bolometric correction; Obscured AGN: corrected or not; Which galaxies are included; Cosmology (H0, matter density) |
| Black hole accretion rate density | Volume for densities; How the accretion-rate density is defined | Luminosity band; Radiative efficiency of accretion; Obscured AGN: corrected or not; Cosmology (H0, matter density) |
| Spin parameter λ_R | Statistic of the spin parameter; Projection (3D, 2D or redshift space) | How the spin parameter is defined; Which stars count toward the mass; Initial mass function (IMF); Which galaxies are included |
| Slow-rotator fraction | Slow-rotator cut | How the spin parameter is defined; Projection (3D, 2D or redshift space); Which stars count toward the mass; Initial mass function (IMF); Which galaxies are included |
| Emission-line luminosity function | Emission line; Dust correction of the luminosities | Volume for densities; Region the quantity is measured within; Cosmology (H0, matter density); Which galaxies are included; How the dust correction was made |
| UV continuum slope vs UV magnitude | Wavelength window of the UV slope; Dust treatment of the colours | – |
| UV continuum slope vs stellar mass | Wavelength window of the UV slope; Dust treatment of the colours | Which stars count toward the mass; Initial mass function (IMF); Which galaxies are included |
Some tables and figures do not state a definition that the source paper does. Each such value is recovered with the paper, section, a short quote and the SHA-256 of the arXiv source archive (§8); a definition that cannot be quoted stays unspecified. A fill never overwrites a stated value.
The figures below show what a comparison looks like when definitions are not harmonized: one relation, one epoch, every simulation that reaches the reference mass, and the observational curves in grey. The stellar mass function at z ≈ 6 is Fig. 1 on the front page; the three figures here are numbered after it. Definitions differ between sources (mass aperture, IMF, SFR timescale, metallicity calibration), so part of any offset in them is not physics.
EAGLEIllustrisIllustrisTNGMagneticum PathfinderSIMBAobservations (8)
COLIBREEAGLEFIREboxIllustrisTNGSIMBAobservations (5)
DARWINEAGLEFLAMINGOHorizon-AGNIllustrisIllustrisTNGMagneticum PathfinderSIMBAobservations (3)
What we changed in the data, and what we did not
The simulation curves are stored as their authors published them. Nothing is corrected for the initial mass function (IMF), the stellar-mass aperture, which galaxies are counted, dust or the cosmology. Where two curves differ in those, the difference is recorded and flagged, not removed. What we did change is only the way numbers are written (a, b) and the fixes in (e). The observation curves that came through a compilation carry that compilation’s own conversions (c), except the corrections made after checking them against the papers (c). Every change is also written in the warning of each record it touches, and the counts below are made from the records, not typed in (DATA-CHANGES.md).
a · Same numbers, written in the axis units we use
Where a paper plots an equivalent axis, the record converts it exactly. Nothing is fitted or interpolated.
| what was re-expressed | Records | mainly |
|---|---|---|
| cosmic time on the x axis turned into redshift (flat LCDM age relation) | 1 | SIMBA |
| an x axis of log10(1+z) turned into redshift | 40 | FLAMINGO, COLIBRE, EAGLE, FIREbox |
| a specific star formation rate per Gyr turned into per year | 32 | FLAMINGO, EAGLE, NewHorizon, COLIBRE |
| a stellar-to-halo (or stellar-to-baryon) mass ratio built or rescaled from the plotted quantities | 51 | Magneticum Pathfinder, Illustris, NIHAO zoom suite, IllustrisTNG |
| a density per unit mass ratio turned into per dex | 13 | EAGLE, Baldry et al. 2012 (GAMA) |
| a UV luminosity or density turned into absolute magnitude or per magnitude | 12 | FLARES |
| published linear error bars turned into dex | 23 | Bouwens et al. 2021, FLARES, Donnan et al. 2024, Harikane et al. 2023 |
| a gas fraction f turned into gas-to-stellar mass ratio, log10(f/(1-f)) | 8 | NewHorizon |
| a display offset the figure added to each redshift taken out again | 16 | THESAN-1 |
b · One cosmology conversion we made ourselves
17 curves (Magneticum Pathfinder): the released mass functions are densities in units that carry h. They are converted with h = 0.704, the simulation’s own value, so each curve stays in its run’s own cosmology.
c · What the observation compilation did before we received the numbers
173 observation curves come from the SWIFT/VELOCIraptor comparison-data compilation (calvin-sykes/velociraptor-comparison-data, commit fc740f4), whose scripts re-express each published table in their own conventions. In those scripts, 142 are corrected for h to a Planck15 cosmology. 9 of those also had their stellar masses converted to a Chabrier IMF by the compilation (Kroupa to Chabrier: mass × 0.912, −0.040 dex; Salpeter to Chabrier: × 0.606, −0.218 dex). These are: Andrews2013 (from Kroupa, 1 curve); Gallazzi2005 (from Kroupa, 2 curves); Grazian2015 (from Salpeter, 4 curves); Kirby2013 (from Kroupa, 1 curve); Reyes2011 (from Kroupa, 1 curve). 15 are taken as published and 16 come from a file whose script could not be matched. These counts come from the constants each script defines, which turned out not to be enough (see below).
Checked against the papers. 50 of these curves were compared with the original paper (its printed numbers or figure, after the paper’s own h and IMF): 24 agree, 3 agree with the fit the paper prints, 20 disagree and 3 cannot be checked because the paper does not contain the numbers. Where the compilation was wrong, 8 curves were shifted by a stated amount. The Grazian 2015 mass functions treat h70 units as h-free, so they were 0.31 dex too high in mass and 0.47 dex too low in density; the Gonzalez 2011 masses were never converted from Salpeter. 16 more curves had a label corrected (cosmology, population, velocity definition, whether they can be ranked) and 3 carry a note. Every change is listed with its evidence in COMPILATION-CHECK.md and written into the record’s warning. One reader made these checks from the papers and the compilation’s scripts; no author or outside expert has reviewed them, and the other curves have not been checked.
d · An optional switch on screen
The Explorer can shift the stellar-mass and SFR axes of simulation curves to a Chabrier IMF (Kroupa −0.040 dex, Salpeter −0.217 dex). It is off by default, labelled wherever it is on, never applied to a curve whose IMF is not stated, and downloads and the Python loader always hold the published values. These offsets are population averages and differ slightly from the compilation’s factors in (c).
e · Mistakes we fixed, and definitions we added
14 fixes to data, analyses or claims are listed, release by release, in the corrections log. 469 simulation records carry a definition (for example the stellar-mass aperture) that the table left unstated and the paper states (60 sourced rules, §3 and §8); a stated value is never overwritten.
What the analyses and tools do with this
- The mass-function study applies IMF offsets and aperture maps inside its own calculation to test whether matching definitions closes the gap between simulated mass functions. It changes no stored curve.
- The definitions study measures how large definition differences are. It corrects no curve.
- The dials page uses the CAMELS simulations as measured (every CAMELS code is measured the same way, so none is converted to match another). The published and observed curves drawn on it are not adjusted to the CAMELS definitions, and the page says so.
- Your run does not convert your numbers. It tells you which of your definitions differ from each curve’s.
What the Explorer computes
Only exact operations: unit-preserving transforms the reader asks for (per unit mass, times mass, physical axes), residuals against a chosen reference using the plotted points only, and, in the Over time view, reading a published curve at one chosen x inside its plotted range. A simulation with no epoch near the chosen redshift disappears; nothing is interpolated in redshift and nothing is extrapolated.
A simulation can carry dozens of records for one relation (resolutions, model variations, populations, fits). The default view shows one fiducial run per simulation and relation and keeps the rest one click away. The number beside each simulation in the legend is its median offset from a default observational anchor over the x range they share: a picture of where predictions and data differ, not a ranking.
Audit
The audit script checks every record (epoch order, provenance, plausible ranges, band consistency, duplicate data, cross-source agreement) and currently reports 0 errors and 0 warnings; accepted exceptions are listed with a reason each. That checks consistency, not that every curve is the right one.
Accepted findings are kept with a reason each in data/audit-known.json; anything else fails the build. A stable sample of records for an independent check by people who know each simulation is in expert-audit-sample.md; no reply has been recorded yet.
Limits
- Not reviewed by anyone outside. No record has been checked by an outside expert. A single author confirming a simulation’s definitions would change the status of its curves.
- Web fonts. The pages load their fonts from Google, which sends the reader’s address to Google on every visit. Your own curve, in the Explorer’s “Your run”, stays in your browser and is never sent anywhere.
- 55% digitized. Digitized curves carry the original authors’ plotting choices, are as precise as the plotted line, and are never rankable; 34% of simulation curves are rankable. Where an author or collaboration releases a table, use that.
- Not a leaderboard. Many curves cannot be compared like for like, and sim-highline says so instead of scoring them.
- Thin relations. Relations with three or fewer simulations. With one simulation: Kennicutt–Schmidt relation; Cosmic metal mass density; UV continuum slope against stellar mass; Projected galaxy correlation function; Sunyaev–Zel'dovich signal–mass relation. With two simulations: Emission-line luminosity function; Hot gas fraction within R500; Halo occupation distribution. With three simulations: Black hole–velocity dispersion (M–σ); Galaxy colour–mass distribution; H2 gas fraction; HI gas fraction; Stellar-mass Tully–Fisher relation; UV continuum slope against UV magnitude. UV luminosity functions (7 simulations) and the cosmic SFR density (15) are recent additions.
- Zoom samples (NIHAO, FIRE-2, NewHorizon) are not volume complete.
- Definition labels are coarse. “Unspecified” hides everything, and two labels that read alike may differ in detail. Observational mocks in simulations are labelled by their definitions; intrinsic and mock quantities are not mixed.
- Catalogue-level runs for TNG and EAGLE need user credentials and are provided as scripts, not data.
The measured size of the definition problem is in definitions study.
Evidence ledger
Every recovered definition is applied only where the record states none, and never overwrites a stated value. Each cites the paper section, a short quote and the SHA-256 of the arXiv source archive that was read (60 rules).
| Source | Sets | Records | Where it says so |
|---|---|---|---|
| Chaikin et al. 2026, MNRAS 548, stag740 arXiv:2509.07960 | massDefinition = aperture-50pkpc | 99 | Sec. 2, Halo finding and calculation of galaxy properties “stellar particles bound to the subhalo within 3D spherical apertures of radius 50 pkpc” |
| Dolag et al. 2025, Encyclopedia Magneticum arXiv:2504.01061 | massDefinition = aperture-0.1Rvir | 18 | Sec. The Magorrian Relation “galaxy stellar mass M*_{R0.1}” |
| Dolag et al. 2025, Encyclopedia Magneticum arXiv:2504.01061 | massDefinition = aperture-0.1Rvir | 18 | Sec. Stellar Mass-Metallicity Relation “stellar mass log10(M*_{R0.1}/Msun)” |
| Dolag et al. 2025, Encyclopedia Magneticum arXiv:2504.01061 | sigmaDefinition = sigma-stellar-projected-within-half-mass-radius | 18 | Sec. Black-Hole-Mass-sigma Relation “velocity dispersion determined in projection within 1 stellar half-mass radius” |
| Dolag et al. 2025, Encyclopedia Magneticum arXiv:2504.01061 | sfrTimescaleMyr = instantaneous | 18 | Sec. Post-Processing, local properties “current star formation rates of all gas particles within the respective radius are summed” |
| Sharda et al. 2026, COLIBRE gas-phase MZR arXiv:2606.25995 | massDefinition = aperture-50pkpc | 14 | Sec. Compilation of simulation data “For EAGLE, stellar masses measured within a 50 kpc aperture” |
| Sharda et al. 2026, COLIBRE gas-phase MZR arXiv:2606.25995 | massDefinition = total-bound-subhalo | 20 | Sec. Compilation of simulation data “For TNG, stellar masses from all star particles bound to the subhalo” |
| Dave et al. 2020, MNRAS 497, 146 arXiv:2002.07226 | massDefinition = caesar-6dfof-galaxy-total | 4 | Sec. SIMBA “galaxies identified using a 6DFOF and used to compute properties such as the SFR and M*” |
| Schaye et al. 2026, MNRAS 548, stag375 arXiv:2508.21126 | massDefinition = aperture-50pkpc | 11 | Sec. 2, Structure finding “galaxy properties computed using the bound particles within 3D apertures of radius 50 proper kpc” |
| Schaye et al. 2026, MNRAS 548, stag375 arXiv:2508.21126 | sfrTimescaleMyr = instantaneous | 3 | Sec. 5, The cosmic star formation history “summing the instantaneous SFRs of all gas particles” |
| Schaye et al. 2026, MNRAS 548, stag375 arXiv:2508.21126 | sfrIntegrationLimit = all gas particles in the box; dustCorrection = none | 5 | Sec. 5, The cosmic star formation history “SFR density calculated by summing the instantaneous SFRs of all gas particles” |
| Feldmann et al. 2023, MNRAS 522, 3831 arXiv:2205.15325 | massDefinition = aperture-Rg | 6 | Sec. 2, Halo and galaxy catalogs “stellar masses, SFRs, and other properties of galaxies refer to integrated properties within R_g” |
| Bird et al. 2022, MNRAS 512, 3703 arXiv:2111.01160 | imf = chabrier03 | 11 | Sec. Metal Return “proportion of massive stars set by a Chabrier initial mass function” |
| Blank et al. 2019, MNRAS 487, 5476 arXiv:1906.06955 | massDefinition = sphere-0.2R200 | 16 | Sec. 2, Initial conditions, galaxy properties “combined mass of all stellar particles within a radius of 0.2 R200” |
| Katz et al. 2023, SPHINX-20 data release arXiv:2309.03269 | massDefinition = integral-of-SFH | 7 | Sec. Available Data, table of quantities “total stellar mass formed, the integral of the star formation history, not adjusted for mass loss” |
| Marszewski et al. 2024, ApJL 967, L41 arXiv:2403.08853 | imf = kroupa01; massDefinition = aperture-0.2Rvir | 3 | Sec. Simulations and Analysis “Kroupa IMF; stellar mass as the total mass of all star particles within 0.2 R_vir” |
| Dubois et al. 2016, MNRAS 463, 3948 arXiv:1606.03086 | sfrTimescaleMyr = 100 | 2 | Sec. Impact of AGN feedback on star formation “sSFR with the amount of stars formed over the last 100 Myr at z=0.3” |
| Diemer et al. 2019, MNRAS 487, 1529 arXiv:1902.10714 | massDefinition = aperture-30pkpc | 4 | Sec. 2, Mock-observing masses, Stellar masses and sizes “we define M* as the stellar mass within a fixed aperture of 30 kpc” |
| Dave et al. 2020, MNRAS 497, 146 arXiv:2002.07226 | massDefinition = aperture-30pkpc | 6 | Sec. EAGLE “properties of galaxies by aggregating the particles residing within 30 kpc of their most-bound particle” |
| Dubois et al. 2014, Dancing in the dark (Horizon-AGN), arXiv:1402.1165 arXiv:1402.1165 | imf = salpeter55 | 35 | Sec. Star formation and stellar feedback “Feedback from stars assuming a Salpeter initial mass function” |
| Kannan et al. 2022, MNRAS 511, 4005 arXiv:2110.00584 | sfrIntegrationLimit = total over all halos in the box; dustCorrection = none | 3 | Sec. Stellar properties, SFRD figure “Contribution from low, medium and high mass halos to the total star formation rate” |
| Crain et al. 2017, MNRAS 464, 4204 arXiv:1604.06803 | gasDefinition = HI within a 70 pkpc aperture | 6 | Sec. The HI mass of galaxies “HI mass within the 70 pkpc aperture that we adopt” |
| Diemer et al. 2019, MNRAS 487, 1529 arXiv:1902.10714 | gasDefinition = HI | 2 | Sec. Gas Fractions “gas fractions: the ratio of the mass in HI or H2 divided by stellar mass” |
| Diemer et al. 2019, MNRAS 487, 1529 arXiv:1902.10714 | gasDefinition = H2 | 2 | Sec. Gas Fractions “gas fractions: the ratio of the mass in HI or H2 divided by stellar mass” |
| Sharda et al. 2026, COLIBRE gas-phase MZR arXiv:2606.25995 | massDefinition = aperture-50pkpc | 18 | Sec. 2, Metallicity estimation “stellar mass and SFR from particles bound to the subhalo within a 50 kpc aperture” |
| Sharda et al. 2026, COLIBRE gas-phase MZR arXiv:2606.25995 | massDefinition = aperture-0.2Rvir | 3 | Sec. Compilation of simulation data “FIRE-2: stellar masses and metallicities estimated using all particles within 20 per cent of the virial radius” |
| Sharda et al. 2026, COLIBRE gas-phase MZR arXiv:2606.25995 | massDefinition = bound-within-Rvir | 4 | Sec. Compilation of simulation data “THESAN-Zoom: stellar masses computed from all bound particles within the virial radius” |
| Dave et al. 2020, MNRAS 497, 146 arXiv:2002.07226 | imf = chabrier03 | 6 | Sec. EAGLE “The simulations assume the Chabrier IMF” |
| Dave et al. 2020, MNRAS 497, 146 arXiv:2002.07226 | imf = chabrier03 | 24 | Sec. SIMBA “A Chabrier stellar initial mass function is assumed in order to compute stellar evolution” |
| Schaye et al. 2026, MNRAS 548, stag375 arXiv:2508.21126 | imf = chabrier03 | 6 | Sec. Stellar mass loss and chemical enrichment “ZAMS mass distribution follows the Chabrier IMF in the range 0.1-100 Msun” |
| Chaikin et al. 2026, COLIBRE progenitors of z>10 JWST galaxies arXiv:2608.19007 | haloMassDefinition = bound-all-particles; haloMassHistory = current | 3 | Sec. Subhalo identification and properties “the halo mass includes all gravitationally bound particles of any type and at any distance” |
| Chaikin et al. 2026, COLIBRE progenitors of z>10 JWST galaxies arXiv:2608.19007 | sfrTimescaleMyr = instantaneous; sfrStatistic = median | 3 | Sec. The evolution of star formation rates “The simulated SFRs are instantaneous; black curves indicate the median SFR-M* relation for star-forming galaxies” |
| Bird et al. 2022, MNRAS 512, 3703 arXiv:2111.01160 | sfrIntegrationLimit = whole simulation box; dustCorrection = none | 1 | Sec. UV Luminosity Function, SFRD figure “The solid black line shows the results from the whole ASTRID simulation box” |
| Feldmann et al. 2023, MNRAS 522, 3831 arXiv:2205.15325 | sfrIntegrationLimit = all identified galaxies in the box; dustCorrection = none | 1 | Sec. Cosmic star formation history and stellar mass “CSFH of all identified galaxies in the simulation volume” |
| Feldmann et al. 2023, MNRAS 522, 3831 arXiv:2205.15325 | sfrIntegrationLimit = galaxies with M*>10^9.3 Msun; dustCorrection = none | 1 | Sec. Cosmic star formation history and stellar mass “low mass galaxies with lg M_star/M_sun<9.3 are excluded” |
| Feldmann et al. 2023, MNRAS 522, 3831 arXiv:2205.15325 | massDefinition = stars in all identified galaxies | 1 | Sec. Cosmic star formation history and stellar mass “cosmic stellar growth history of all identified galaxies in the simulation volume” |
| Feldmann et al. 2023, MNRAS 522, 3831 arXiv:2205.15325 | massDefinition = stars in galaxies with M*>10^9.3 Msun | 1 | Sec. Cosmic star formation history and stellar mass “low mass galaxies with lg M_star/M_sun<9.3 are excluded” |
| Dubois et al. 2021, A&A 651, A109 arXiv:2009.10578 | sfrIntegrationLimit = all galaxy (sub)structures in the zoom volume; dustCorrection = none | 1 | Sec. Star formation rates “summing all star particles formed over the last 100 Myr within the entire volume of the simulation, associated with a galaxy (sub)structure” |
| Dubois et al. 2021, A&A 651, A109 arXiv:2009.10578 | metallicityCalibration = total metallicity rescaled by the solar oxygen fraction | 4 | Sec. Stellar and gas metallicities “we rescale the gas metallicity values by a factor corresponding to the fractional abundance of oxygen in the solar atmosphere” |
| Ricarte et al. 2019, MNRAS 489, 802 arXiv:1904.10116 | massDefinition = sum of star particles x 0.6 (Munshi+13 correction) | 5 | Sec. Halo Finding and Data Analysis “Throughout this paper, we multiply all stellar masses by 0.6, and divide all halo masses by 0.8” |
| Lagos et al. 2015, MNRAS 452, 3815 arXiv:1503.04807 | gasDefinition = H2 within 30 pkpc | 3 | Appendix, prescription of Krumholz “total H2 mass within 30 pkpc of the galaxy centre” |
| Vogelsberger et al. 2014, MNRAS 444, 1518 arXiv:1405.2921 | sfrIntegrationLimit = total SFRD of all galaxies in the box; dustCorrection = none | 1 | Sec. Large-scale structure statistics, SFRD figure “The black solid line shows the total SFRD” |
| Vijayan et al. 2021, MNRAS 501, 3289 arXiv:2008.06057 | sfrIntegrationLimit = galaxies with SFR >= 0.1 Msun/yr | 3 | Sec. Star formation rate density “star formation rate density for galaxies with SFR >= 0.1 Msun/yr” |
| Dave et al. 2019, MNRAS 486, 2827 arXiv:1901.10203 | sfrIntegrationLimit = all star formation in the volume; dustCorrection = none | 1 | Sec. Star formation history “The SIMBA SFRD values include all the star formation in the volume at each epoch” |
| Tremmel et al. 2017, MNRAS 470, 1121 arXiv:1607.02151 | sfrIntegrationLimit = total over the simulation volume; dustCorrection = none | 1 | Sec. First Results from Romulus25 “The solid blue line shows the total cosmic star formation history in Romulus25” |
| Furlong et al. 2015, MNRAS 450, 4486 arXiv:1410.3485 | sfrIntegrationLimit = total cosmic SFR density of the box; dustCorrection = none | 1 | Sec. Evolution of star formation rates “Evolution of the cosmic star formation rate density. The EAGLE simulation is plotted as a solid black curve” |
| Vogelsberger et al. 2014, MNRAS 444, 1518 arXiv:1405.2921 | massDefinition = baryonic mass within r_star | 1 | Sec. Characteristics of individual galaxies, Tully-Fisher relations “We measure the total baryonic mass within r_star” |
| Feldmann et al. 2023, MNRAS 522, 3831 arXiv:2205.15325 | massDefinition = aperture-Rg | 6 | Sec. 2, Halo and galaxy catalogs; the quiescent-fraction figure caption states no other aperture “Unless stated otherwise, stellar masses, SFRs, and other properties of galaxies refer to integrated properties within $R_{\rm g}$ computed as in the first method.” |
| Garaldi et al. 2024, MNRAS 530, 3317 (THESAN public data release) arXiv:2309.06475 | sfrTimescaleMyr = instantaneous (gas) | 5 | Sec. 'The galaxy main sequence at z>6', note on the SFR reported in the main-sequence figures “we report the instantaneous SFR, computed internally by the simulation at run time from the gas bulk properties only” |
| Lagos et al. 2017, MNRAS 464, 3850 arXiv:1609.01739 | massDefinition = aperture-30pkpc | 5 | Sec. 2.2 (Calculation of dynamic and kinematic properties of galaxies in EAGLE), paragraph defining M_stars, M_neutral, M_bar “Following S15, all these properties are measured in $3$-dimensional apertures of $30$~pkpc.” |
| Dave et al. 2020, MNRAS 497, 146 arXiv:2002.07226 | massDefinition = bound to a Subfind subhalo, within the variable BaryMP aperture (Stevens+14; 'inherent' definition of Stevens+19) | 4 | Sec. 2.3 (IllustrisTNG), last paragraph before 'Comparison of Models' “TNG100 galaxy properties in this paper follow the `inherent' definition of~\citet{Stevens:2019}. This means isolating particles/cells bound to (sub)structures according to {\sc Subfind}” |
| Dolag et al. 2025, Encyclopedia Magneticum (arXiv:2504.01061) arXiv:2504.01061 | massDefinition = aperture-0.1rvir | 18 | Sec. 'Specific Angular Momentum Relation', caption of Fig. jstar_mstar (fig:jm-relation) “For the simulation we show $J^*_{3R_{1/2}}$ and $M^*_{R_{0.1}}$, which are the two quantities which were determined as the best morphological indicators” |
| Dolag et al. 2025, Encyclopedia Magneticum (arXiv:2504.01061) arXiv:2504.01061 | jDefinition = stars within 3 R_1/2 (3D stellar half-mass radius), j = sum m r x v / sum m (Teklu+15) | 18 | Sec. 'Specific Angular Momentum Relation', caption of Fig. jstar_mstar; definition in Sec. 'Local properties' “For the simulation we show $J^*_{3R_{1/2}}$ and $M^*_{R_{0.1}}$” |
| Dolag et al. 2025, Encyclopedia Magneticum (arXiv:2504.01061) arXiv:2504.01061 | sfrStatistic = median | 18 | Caption of Fig. sfms (fig:sfms); text in Sec. 'Galaxy Star Formation Main Sequence' “Median lines are calculated using active galaxies only, that is galaxies above the threshold by \citet{carnall:2020}” |
| Dubois et al. 2021, A&A 651, A109 arXiv:2009.10578 | massDefinition = all star particles in the simulation that are associated with a galaxy (sub)structure, summed over the box | 1 | Sec. 'Star formation rates', text after Fig. cosmicsfr (cosmic stellar density, bottom panel) “this value is obtained by summing over the individual mass of all the star particles in the simulation, which are again associated with a galaxy (sub)structure, whether pure or not” |
| Katz et al. 2023, SPHINX-20 data release (arXiv:2309.03269) arXiv:2309.03269 | imf = kroupa01 | 44 | Sec. 4 Discussion, subsection 'Caveats' (list of modelling assumptions of SPHINX) “For example, we have chosen a specific stellar IMF (Kroupa-like), a stellar population synthesis library ({\small BPASS}) for the stellar spectra” |
| Diemer et al. 2019, MNRAS 487, 1529 arXiv:1902.10714 | gasStatistic = median of the gas fractions above a threshold (galaxies below it are counted separately) | 4 | Sec. 4.3 'Gas Fractions' (text before Fig. fraction) “we now count the fraction of galaxies that lie below the threshold, $f_{\rm low}$, and compute the median and 68\% scatter of those gas fractions that lie above the threshold.” |
| Diemer et al. 2019, MNRAS 487, 1529 arXiv:1902.10714 | gasMethod = centre of the shaded region spanned by nine HI/H2 partition methods (no single model) | 4 | Sec. 3.2 'Modelling the HI/H2 Fractions' “Thus, the \hi and \htwo masses of each galaxy are estimated by a total of nine different methods. In the forthcoming figures, we shade the region between the models but do not show the individual models to avoid crowding.” |
| Schaye et al. 2026, MNRAS 548, stag375 arXiv:2508.21126 | haloMassDefinition = BN98; haloMassHistory = current | 3 | Sec. 7.1.1 'The galaxy stellar mass function', paragraph after Fig. smhm (stellar-to-halo mass ratio) “we define the halo mass as the mass within the radius for which the mean internal density is equal to the critical overdensity provided by \citet{Bryan1998}” |
| SWIFT/VELOCIraptor comparison-data compilation, conversion script for Kirby et al. 2013 arXiv:convertKirby2013.py | imf = chabrier03 | 0 | comment string written into the converted file “There is also a correction of {kroupa_to_chabrier_mass} on the stellar masses to convert from Kroupa to the Chabrier IMF.” |
Read, and not stated
432 definition values remain open: 343 where the paper was read and does not state it, 80 where it has not yet been read for that key, and 9 where the source is a data release without a paper. The papers below were searched for the listed definitions and do not state them, so the values stay unspecified instead of being inferred. The full list, with the paper to read for each, is UNDOCUMENTED-DEFINITIONS.md.
- Wilkins et al. 2017 (BlueTides) (arXiv:1704.00954): Chabrier IMF is stated for the SPS photometry and for the observations compared with, not for the simulation stellar mass; no aperture stated. The SFR averaging timescale, the epoch of the halo mass and the black hole mass method are not stated for the tables. Read a second time on 2026-10-18. Chabrier is named only for the SED library and for observations converted to it; no stellar-mass, SFR-timescale, halo-mass-epoch or black-hole-mass definition is given for the simulation tables.
- Kaviraj et al. 2017 (Horizon-AGN) (arXiv:1605.09379): The source text has no statement of the stellar-mass definition behind the plotted mass function. The cosmic star formation history is shown without a statement of how it was integrated or of the SFR indicator. Read a second time on 2026-10-18. The stellar mass of a galaxy is not defined; the star formation history figure caption states none of the four SFR-density keys; the paper has no black hole mass versus stellar mass figure.
- Habouzit et al. 2021 (arXiv:2006.10094): Uses total stellar mass of each simulation, and states the computations may differ between simulations; no per-simulation aperture or IMF. Read a second time on 2026-10-18. The paper says the stellar masses are 'total' and may be computed differently in each simulation, and names no IMF; an aperture given in an appendix applies only to eight matched galaxies.
- Sparre et al. 2015 (Illustris) (arXiv:1409.0009): No stellar-mass aperture stated for the main-sequence figures. Read a second time on 2026-10-18. The stellar mass behind the main-sequence figures is not defined.
- Genel et al. 2015 (Illustris) (arXiv:1503.01117): No radius restriction for j; stellar-mass definition not stated. Read a second time on 2026-10-18. The stellar mass is not defined; j is defined for all stellar particles of the subhalo without a radius cut.
- Dubois et al. 2021 (NewHorizon) (arXiv:2009.10578): Stellar-mass definition for sizes and black-hole relations not stated in the sections searched. The zoom volume is given in Mpc without saying comoving or physical. Read a second time on 2026-10-18. Stated only for the stellar mass density and for one selection-corrected mass function curve; not stated for the size and black hole relations or for the density frame (the volume is the initial (16 Mpc)^3).
- Blank et al. 2021 (NIHAO XXVI) (arXiv:2008.13379): SFR is stars formed in the last 200 Myr within 0.2 R_vir; the stellar-mass definition is not restated. Read a second time on 2026-10-18. Only the SFR is defined (star particles within 0.2 R_vir formed in the last 200 Myr).
- Dave et al. 2019 (SIMBA) (arXiv:1901.10203): Comoving versus physical density is not stated for the mass function. Read a second time on 2026-10-18. No statement of comoving or physical for the mass function or the star formation rate density; comoving appears only for box length and softening.
- Katz et al. 2023 (SPHINX-20) (arXiv:2309.03269): IMF of the simulation stellar populations not stated in the data-release paper.
- Lagos et al. 2017 (EAGLE) (arXiv:1609.01739): j measured within r50 or 5 r50; stellar-mass definition not restated.
- Dolag et al. 2025 (Magneticum) (arXiv:2504.01061): The stellar mass function, size, SFMS and angular-momentum sections do not state which of the paper's mass apertures the released tables use. Read a second time on 2026-10-18. The mass function, size and main-sequence figures do not state the stellar-mass aperture; the paper states M*_{R_0.1} for the angular-momentum, mass-metallicity and other figures only, and it is not carried over by inference.
- Diemer et al. 2019 (TNG HI and H2) (arXiv:1902.10714): Searched; the statistic and H2 model for the plotted medians are not stated where the records come from.
- Huang et al. 2018 (BlueTides) (arXiv:1801.04951): No IMF statement found.
- Crain et al. 2015 (EAGLE) (arXiv:1501.01311): No mass-definition statement for the stellar mass density found; the IMF is stated.
- Dave et al. 2020 (arXiv:2002.07226): Not stated for the TNG records and for the EAGLE mass function and sSFR records. The TNG IMF is not stated either. Read a second time on 2026-10-18. No IMF for IllustrisTNG; no density frame for any of the three; no SFR timescale for EAGLE or IllustrisTNG, and for SIMBA only the per-element law is given.
- Schaye et al. 2026 (COLIBRE) (arXiv:2508.21126): The stellar-to-halo mass figure does not state the halo mass definition in the caption or nearby text.
- Sharda et al. 2026 (COLIBRE MZR) (arXiv:2606.25995): Not stated for the SIMBA and FIREbox comparison curves. Read on 2026-10-18. The SIMBA and FIREbox mass-metallicity curves are adopted from Garcia et al. 2025 and Feldmann et al. 2023 and the stellar-mass definition is not restated; the 3 kpc aperture given is for the oxygen abundance.
- Feldmann et al. 2023 (FIREbox) (arXiv:2205.15325): Comoving versus physical density of the mass function is not stated. Read a second time on 2026-10-18. The box volume is given as (15 cMpc/h)^3 and the mass function is built from 1/V weights, but no sentence says the density is per comoving volume; not inferred.
- Bird et al. 2022 (ASTRID) (arXiv:2111.01160): FOF and SUBFIND stellar masses are both shown; which one the digitized relations use is not stated. Read a second time on 2026-10-18. Star particles are attached to the host FOF halo and the stellar mass function text says 'stars within FOF halos', but no sentence ties the stellar-to-halo mass or metallicity figures to a mass definition; not inferred.
- Pillepich et al. 2018 (the IllustrisTNG model) (arXiv:1703.02970): Read again on 2026-10-18. The cosmic star formation rate density panel (Fig. 4, top left) is plotted without saying how it was computed; the only use of 'instantaneous' is for the local star formation rate that drives the wind model, not for the plotted curve.
- Buck et al. 2019 (NIHAO-UHD) (arXiv:1909.05864): Read on 2026-10-18. The paper mentions the initial mass function only in general terms and defers the model to the NIHAO base paper; the base paper (Wang et al. 2015, arXiv:1503.04818) states a Milky Way-type IMF only for the abundance-matching comparison, not for the simulation's stellar particles.
- Kannan et al. 2022 (THESAN overview) (arXiv:2110.00584): Read on 2026-10-18. The stellar-to-halo mass figure and its text do not state which halo mass is used or at what epoch.
- Garaldi et al. 2024 (THESAN data release) (arXiv:2309.06475): Read on 2026-10-18. The data-release paper describes the group catalogues but does not state the halo mass used in the released stellar-to-halo mass table (smhm_Thesan1.dat), whose header gives only the column names.