Catalogues, HiPS, and SAMP

VisIVO is not just a viewer for one cube at a time — it’s also a workbench for putting cubes / images in context: overlay source catalogues, browse all-sky HiPS surveys at any zoom level, and exchange data with TOPCAT / Aladin / DS9 via SAMP.

3-D catalogue viewer

A dedicated 3-D scatter viewer (vtkWindowCatalogue3D) renders large catalogues — millions of entries — as glyphs in Cartesian (RA / Dec / distance) space.

Opens from File → Open 3-D Catalogue… (CSV or VOTable on the backend filesystem) or from the Command Palette (⌘K → “open 3d catalogue”).

Coordinate frame & distance

The viewer needs both a sky frame and a distance for each entry:

Frame combo

FK5 / J2000 (default) or Galactic (l, b). Conversion is done with wcscon() from libwcs the moment you switch frame.

Distance source (priority)

  1. entry.distanceMpc override (set by the cosmology selector)

  2. The catalogue’s distance / dist / dMpc field

  3. A redshift field (z, REDSHIFT, ZSPEC, ZMEAN, ZPHOT) integrated through a chosen cosmology

  4. Hard-coded 300 Mpc fallback

Cosmology models

For redshift-derived distances pick one of:

  • Planck18 — local Riemann integration (H₀ = 67.74, Ωm = 0.3089, ΩΛ = 0.6911). No network call.

  • Planck15 / Planck13 / WMAP9 — computed by the backend (POST /v1/cosmology/distance/batch, async). The viewer re-projects the cloud automatically when results arrive.

Tip

For catalogues with explicit redshifts, switching between Planck18 and WMAP9 can shift comoving distances by several %; useful as a sanity check before drawing conclusions about clustering or LSS.

Glyph & size modes

Setting

Options

When to use

Geometry

Ellipsoid, Sphere, Point, Cross

Ellipsoid for axis-aware sources; Point for very dense fields where glyph overhead matters.

Size

Fixed, Major axis, LLS, Flux

“Major axis” scales each glyph by the catalogue’s morphology size; “Flux” by intensity (good for highlighting brightest objects).

Color

Morphology class (deterministic palette) or any scalar field

Click the Color mode card and pick a scalar to drive the colour map; the colour bar updates live.

Filters & paging

For million-row catalogues the backend exposes a paginated query API:

  • Filters are AND-combined, with operators <, ≤, >, ≥, =, ≠, contains, startswith, endswith.

  • The Filter sidebar lets you stack multiple filters and apply them in one click — the query is sent to the backend, the result count is shown, and the cloud rebuilds with only matching entries.

  • Datasets > 50 000 rows are loaded in pages of 50 000; the Load more (N remaining) button appears in the filter card.

Interaction

  • Hover a glyph → yellow wireframe sphere; the info panel shows all catalogue fields for that source.

  • Click → red wireframe outline + the source is highlighted in the Catalogue table dock.

  • Click a table row → camera flies to centre on the source.

Catalogue overlay on cubes / images

In any cube viewer or image viewer you can overlay a catalogue on the 2-D slice / moment / image. The whole feature is driven by four menu entries under Tools → Catalogue (in the cube viewer) — three checkable state toggles plus one one-shot loader:

Tool

Type

What it does

Load Catalogue Overlay

One-shot

Open a file picker (or paste a backend path) for a CSV / VOTable. The backend parses it (/v1/catalogue/open), returns the source list, and the client renders the glyphs immediately on the slice. Each call replaces the currently-loaded overlay.

Show Catalogue Overlay

Toggle

Show / hide the glyph layer without unloading the catalogue. Useful when you want to compare slice features against the catalogue back and forth — much cheaper than re-loading.

Show Catalogue Labels

Toggle

Show / hide the per-source labels (object name from the catalogue’s name column). Labels are crowded on dense fields, so they default to off. The viewer caps the number of visible labels (≈ 200) to keep rendering fluid; when the field has many more sources, only the brightest / most central are labelled.

Clear Catalogue Overlay

One-shot

Drop the catalogue entirely — glyphs, labels, and the table dock. Frees backend memory and resets the Show… toggles. Run a Load again to bring it back.

The overlay also drives a dock-window table:

  • Click a row → centre the view on the source (smooth fly-in animation).

  • Hover a glyph → highlight the matching row in the table.

  • Right-click selection → send via SAMP (see below).

The overlay respects the viewer’s WCS frame (J2000 / Galactic / Ecliptic); each source is projected through wcscon() so you see the same point regardless of the active frame.

Tip

Workflow sequence: Load once to bring sources in → toggle Show Catalogue Overlay off and on as you scrub channels to compare emission against catalogued positions → enable Show Catalogue Labels only when you actually need names (cluttering otherwise) → Clear when you switch to a different catalogue.

Why overlay a catalogue on a cube?

Three common use cases:

  1. Source identification — overlaying a YSO catalogue on a moment-0 map tells you which IR-bright pre-main-sequence sources sit inside the molecular emission you’re integrating, helping disentangle star formation context from diffuse cloud structure.

  2. Cross-survey comparison — overlay a centimetre-continuum source list on a HI cube to see whether neutral-hydrogen self-absorption features coincide with background continuum positions (classic technique for HISA studies).

  3. Pointing / coordinate sanity check — when you receive a new cube from a different observatory, overlaying a well-known catalogue (e.g. 2MASS PSCs, Spitzer point sources) is a quick way to spot coordinate-system or astrometric offsets before any science analysis.

HiPS viewer

Hierarchical Progressive Surveys (HiPS) are pre-tiled multi-resolution all-sky images served as static files. VisIVO ships with a built-in HiPS browser:

Open from File → HiPS Viewer… or the Command Palette.

Workflow:

  1. Paste a HiPS root URL (e.g. http://alasky.u-strasbg.fr/DSS/DSS2Merged). The viewer asks the backend to discover the survey properties (orders, tile format, native frame, FOV).

  2. Pan & zoom with the mouse. The viewer requests only the tiles needed for the current viewport (/v1/hips/{id}/query_tiles); levels of detail load on demand.

  3. Catalogue overlay — the backend can return a Simbad / VizieR / custom catalogue restricted to the visible field (/v1/hips/catalogue_overlay).

  4. Target resolution — type a name (“M87”, “NGC 1068”) in the search bar; the backend resolves it via Sesame (/v1/resolve/target) and centres the view.

Note

HiPS tile fetching is HTTP only and goes through the backend so that firewalled / VPN’d HiPS roots still work for the desktop client; you don’t need direct internet access from the GUI.

SAMP

Send and receive data with TOPCAT, Aladin, DS9, and any other VO-aware tool on your machine. The desktop client talks to the bundled SAMP bridge in the backend (router /v1/samp/*, exposed without auth so the local SAMP hub can reach it).

Capabilities:

  • Send a FITS — share the currently open dataset to all subscribed applications (/v1/samp/send-fits).

  • Send a catalogue — broadcast a VOTable, e.g. a region selection from the catalogue overlay (/v1/samp/send-catalogue).

  • Import URL / Upload file — bring an external resource into your session, e.g. a TOPCAT-prepared catalogue (/v1/samp/import-url, /upload-file).

  • Receive — incoming messages from peers are queued in /v1/samp/inbox; the client surfaces them as notifications and offers to open the payload.

You can monitor the hub state from View → SAMP Status in the main window or via the Command Palette.

See also