Euclid Quick Data Release (Q1): First visual morphology catalogue

Interactive visualiser at euclid.streamlit.app. 

Contents

1. Catalogue (morphology_catalog.csv/parquet)
   1. List of ID columns and morphology columns
   2. List of morphology questions and answers available
   3. List of additional columns copied from MER (flux, ellipticity, area, etc.)
   4. Extra physical measurements (extra_physical_measurements.parquet)
2. Images (cutouts...tar)

Full documentation is available here. Below is a summary.

1. Catalogue (morphology_catalog.csv/parquet)

The morphology catalogue covers galaxies which are either bright or extended. Specifically, it includes galaxies matching one of the following criteria:

• segmentation area > 700 pixels, or...
• VIS < 20.5 AND segmentation area > 200 pixels

The measurements were made by Zoobot foundation models, finetuned on Euclid galaxies using the responses of Galaxy Zoo volunteers.

Our models were trained using galaxies from the selection cuts above but with the first option requiring 1200 pixels. Therefore, galaxies between 700 and 1200 pixels in area are may have less reliable measurements. 

The catalogue file is morphology_catalogue (.parquet or .csv, the contents are identical). It includes the following columns:

The following questions and answers are available. 

For convenience, we have also copied over some useful MER catalogue columns. The schema for the full MER catalogue is here. Additionally, Euclid also makes available many other tables with e.g. photometric redshifts, estimated masses, etc. These are documented here. All fluxes are in micro-janskies (uJy).

1b  Useful Physical Measurements (useful_physical_measurements.parquet)

(added 29th March 2025)

People often want to combine morphology with physical measurements like redshift, stellar mass, etc. This table includes these columns. You can cross-match to the morphology catalog using object_id.

The columns are copied from the Science Archive Service database and are grouped by the origin table. They are:

MER columns (flux, shape)

MER morphology columns (CAS, Gini, Sersic profiles)

PHZ (Photometric redshift)

PP ("p"hysical "p"arameters inc. stellar mass, star formation rate, luminosity, an alternative photometric redshift)

Below is a full schema. The descriptions are summarised from the Q1 Data Product Description Document.

object_id, right_ascension, declination

2. Images

We are sharing the original cutout images as shown to Galaxy Zoo volunteers. The images are named like {tile_index}_{object_id}.jpg, where the negative sign ('-') in object id is replaced with 'NEG' to avoid path issues. You can construct the file paths from the morphology catalogue. For example:

The VIS+Y images are composites with VIS in the blue channel and Y in the red channel (and the median of VIS and Y in the green channel, but this isn't visible). They use an arcinsh stretch, with the stretch designed to balance the contribution from each band.

The VIS only images are black-and-white, and also use an arcsinh stretch.

The VIS LSB images use a more complicated stretch to highlight LSB features. This is not included yet on Zenodo.

Full details of the image processing are in the Q1 visual morphology paper.