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Lightcone Mode

Lightcone Mode opens a LightSAGE cli_lightcone HDF5 output — a flat catalogue of galaxies spanning a range of redshifts along an observer's line of sight — in the exact same Explore UI as a SAGE box: same toolbar, navigation panel (every colour-by mode), info panel, and gaussian-splat rendering.

See Launch Mode → LightSAGE steps for how to produce a lightcone file from existing SAGE26 output.

Opening a lightcone

visage --lightcone /path/to/lightcone.h5

Or, from inside the wizard's LightSAGE flow, click Visualize lightcone after a successful run to relaunch straight into it. Or pick it from the Session Models list (see below) if you've opened it before.

What gets loaded

Every SAGE field carried in the flat lightcone file is read into a full galaxy snapshot — so every Structure tab colour-by mode (stellar mass, sSFR, cold gas, B/T, …) works exactly as it does for a SAGE box. Host haloes are built from the galaxies with Type == 0 (centrals).

A lightcone is a single static point cloud (it already spans every redshift at once), not a per-snapshot simulation — so there's no background snapshot preloading and no per-model output-directory scan.

The snapshot slider is a redshift/time cut

Unlike a SAGE box, where the slider selects one snapshot to display, in Lightcone Mode the slider:

  • only spans the snapshots actually present in the cone (not the full 0–63 range of the underlying simulation)
  • removes galaxies nearer than the selected point (lower redshift), keeping everything farther away (higher redshift)
  • shows the full cone when pulled to its maximum (the default on load)

Drag it inward from the maximum to peel away the near side of the cone and see what's left at higher redshift.

Synthetic photometry (SED)

If the lightcone was run through the LightSAGE flow's optional SED stage (see Launch Mode → LightSAGE steps), Lightcone Mode replaces the Box tab (a periodic box has no meaning for a cone) with a Photometry tab — a false-colour image builder.

Photometry is its own independent layer, separate from the galaxies, with its own Visible checkbox and Opacity slider. It's hidden by default; ticking Visible shows it and hides the normal galaxies by default so the image reads cleanly (unticking it brings them back). Because it's a separate layer you can view it however you like — re-enable the galaxies (Structure tab) to overlay both, or keep them off for the photometry image on its own. Galaxies with no flux in the stacked filters are simply not drawn.

When shown, it draws the galaxies as Rvir-sized gaussian splats painted from a stack of the filters you tick in the Filters dropdown. Each filter is tinted a representative colour — UV/u violet, g green, r/i/z and the near-/mid-IR bands (J, H, K, WISE) deepening reds — and scaled by the galaxy's brightness in that band; the ticked filters are summed into an additive false-colour composite. Tick one filter for a single-band image, or several to build a multi-band colour image; mass-to-light (M*/L) entries can be stacked the same way. A colour-swatch legend shows the current stack.

The Photometry tab only appears for lightcones that actually carry SED data (otherwise it shows a short note explaining how to produce it).

Camera

Resetting the camera frames the cone horizontally, centred and zoomed in, showing it end to end (rather than the cubic-box framing used for a SAGE box) — this is also the initial view on load.

The go-to-centre button (▶ centre icon) doesn't use a box centre in Lightcone Mode — instead it stands you at the observer (the coordinate origin) looking outward along the cone, with the sky spread horizontally, as if gazing out into the lightcone.

Session models

The Launch-Mode dropdown (SAGE-logo button, top-left of the toolbar) lists every box and lightcone opened so far this session under Session Models, with a box or telescope icon marking the kind and the currently active one highlighted. Click any entry to jump straight back to it — a quick relaunch on the same port — so loading a SAGE box after a lightcone (or vice versa) never loses track of what you had open.

This list is persisted across relaunches in ~/.visage/session_models.json.

Things that don't apply in Lightcone Mode

A lightcone has no periodic box and isn't tied to a single SAGE parameter file, so a few Explore-mode features that assume a box don't apply:

  • Multi-model overlay / side-by-side comparison (a lightcone is always the sole loaded model)
  • The .par-derived cosmology display (cosmology is read from the lightcone's copied SAGE header instead)