# Galaxy-scale catalogues (`data/galaxy/`) — sources and terms

`data/galaxy/galaxy_objects.csv` (14,616 objects) and `data/galaxy/young_stars.bin`
(100,000 stars) put real objects across the Milky Way on the holo map
(`scripts/galaxy_objects.gd`). Both are generated by
`tools/build_galaxy_catalogs.py`, which downloads every source below (VizieR
`asu-tsv`, the Baumgardt globular-cluster database, the ATNF web query) and can
be rerun to reproduce them. Downloads: 2026-09-28.

The files are compilations of published measurements. Expanse distributes them
under **Creative Commons Attribution 4.0 (CC BY 4.0)** —
https://creativecommons.org/licenses/by/4.0/ — **except** the parts derived
from Gaia data (the open-cluster rows, `cat` = `HR23`, and all of
`young_stars.bin`), which follow the Gaia terms used for `data/gaia_stars.bin`:
credit **ESA/Gaia/DPAC**, CC BY-NC 3.0 IGO (see `data/GAIA_LICENSE.md`).
Please keep the catalogue citations below, which the catalogues ask for.

**VizieR.** This research has made use of the VizieR catalogue access tool,
CDS, Strasbourg, France (DOI 10.26093/cds/vizier); the original description of
the VizieR service was published in Ochsenbein, Bauer & Marcout 2000, A&AS 143,
23. Terms: https://cds.unistra.fr/vizier-org/licences_vizier.html — use with
acknowledgement of VizieR and of each catalogue's paper, as done here.

## Catalogues

| Class (`cls`) | Rows | Source | Distance (`dist_src`, `dist_method`) |
|---|---|---|---|
| `open` | 6,818 | **Hunt, E. L. & Reffert, S. 2023**, *Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3*, A&A 673, A114 — VizieR J/A+A/673/A114 (`clusters`, type `o`; moving groups and the globulars it also lists are left out) | measured: maximum-likelihood distance from the Gaia DR3 parallaxes of the members (`dist16`–`dist84` kept as the range) |
| `globular` | 167 | **Baumgardt, H. & Vasiliev, E. 2021**, MNRAS 505, 5957; **Vasiliev & Baumgardt 2021**, MNRAS 505, 5978; **Baumgardt & Hilker 2018**, MNRAS 478, 1520 — the Galactic globular cluster database, https://people.smp.uq.edu.au/HolgerBaumgardt/globular/ (`combined_table.txt`) | inferred: mean of Gaia EDR3 / HST parallaxes, kinematic and literature (CMD, RR Lyrae …) distances |
| `cepheid` | 2,214 | **Skowron, D. M. et al. 2019**, *A three-dimensional map of the Milky Way using classical Cepheid variable stars*, Science 365, 478 — VizieR J/other/Sci/365.478 (`tables1`, rows with a distance) | inferred: mid-infrared period–luminosity relation |
| `maser` | 199 | **Reid, M. J. et al. 2019**, *Trigonometric parallaxes of high-mass star-forming regions: our view of the Milky Way*, ApJ 885, 131 — VizieR J/ApJ/885/131 (`table1`), with the paper's arm assignments | measured: VLBI trigonometric parallax |
| `hii` | 1,413 | **Anderson, L. D. et al. 2014**, *The WISE catalog of Galactic H II regions*, ApJS 212, 1 — VizieR J/ApJS/212/1 (`wisecat`, rows with a distance) | inferred (kinematic, the catalogue's method kept) or measured (maser parallax, 127 rows) |
| `snr` | 190 | Positions, sizes, types, fluxes: **Green, D. A. 2025**, *A catalogue of Galactic supernova remnants* — VizieR VII/297 (310 remnants). Distances: **Ranasinghe, S. & Leahy, D. 2023**, ApJS 265, 53 (VizieR J/ApJS/265/53); method names from **Ranasinghe & Leahy 2022**, ApJ 940, 63 (VizieR J/ApJ/940/63) | inferred except parallax-based ones; the 120 remnants with no published distance are **not placed** |
| `pulsar` | 3,615 | **ATNF Pulsar Catalogue** v2.6.1 — Manchester, R. N., Hobbs, G. B., Teoh, A. & Hobbs, M. 2005, AJ 129, 1993 — https://www.atnf.csiro.au/research/pulsar/psrcat/ (web query for every pulsar, parameters in the build tool) | measured (timing / VLBI parallax) or inferred (YMW16 dispersion-measure model, Yao, Manchester & Wang 2017, ApJ 835, 29; or ATNF `DIST_A`). 222 pulsars with no distance, or whose dispersion measure exceeds the YMW16 Galaxy (the model's 25 kpc cap), are left out |
| young stars | 100,000 | **Zari, E., Rix, H.-W., Frankel, N. et al. 2021**, *Mapping luminous hot stars in the Galaxy*, A&A 650, A112 — VizieR J/A+A/650/A112 (`filtered`, 417,540 stars); the 100,000 with the brightest absolute K_s within 5 kpc | inferred: the paper's astro-kinematic distance (`d_max_pdf_kin`, Gaia EDR3 parallax + a rotation prior) |

Values other than the distance carry a fixed provenance tag per class
(`GalaxyObjects.EXTRA_TAGS`): e.g. cluster member counts, Cepheid periods,
maser parallaxes, pulsar periods and dispersion measures are *measured*;
cluster ages (isochrone fits), globular masses (N-body fits), Cepheid ages
(period–age), arm assignments, pulsar characteristic ages and dipole fields
are *inferred*.

## Merged with the other layers (no object twice)

Rows that are already in `data/deep_sky.csv` (71 open clusters such as M45 /
Melotte 22 and M44, 35 globulars such as M4 and 47 Tuc, the Crab Nebula and
Cygnus Loop, the Orion, Carina and North America nebulae) or in
`data/exotic_objects.csv` (87 curated pulsars and magnetars) keep a `link`
and take that layer's position and distance; the catalogue's own distance is in
the `cat_d` extra. The Double Pulsar's B pulsar is folded into its exotic entry.

## Precision / quantisation

`galaxy_objects.csv`: RA / Dec to 1e-5 degrees, distances to 1 ly.
`young_stars.bin`: "EXYOUNG\1", u32 count, u32 stride (8), u32 levels (16),
padding to 32 bytes, then per star x, y, z (light-years, Godot axes = the
StarCatalog frame) and a luminosity level 0–15 (absolute K_s −8 … 0) as IEEE
float16, sorted by distance. float16 spacing is 2 ly at 2,000–4,000 ly, 4 ly to
8,000 ly and 8 ly to 16,000 ly — far below these stars' distance errors.