Euclid Quick Data Release (Q1): First visual morphology catalogue
Authors/Creators
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1.
University of Toronto
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2.
University of Manchester
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3.
Université Paris Descartes
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4.
Observatoire de Lyon
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5.
Haverford College
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6.
European Space Astronomy Centre
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7.
European Space Agency
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8.
The Open University
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9.
University of Trieste
Contributors
Research group (2):
Description
Image to be added after embargo lifts on 19th
Contents
- Catalogue
- List of ID columns and morphology columns
- List of morphology questions and answers available
- List of additional columns copied from MER (flux, ellipticity, area, etc.)
- Images
Full documentation is available here. Below is a summary.
1. Catalogue
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:
| release_name | Always Q1_R1, for now |
| tile_index | Euclid tile index i.e. which MER tile hosts this galaxy |
| object_id | Euclid object id i.e. the MER catalogue identifier for this galaxy |
| segmentation_map_id | Alternative Euclid identifier. The first 9 digits are the tile index, the other digits match the internal segmentation id of the source. |
| right_ascension | in degrees, from the MER catalogue |
| declination | in degrees, from the MER catalogue |
| {question}_{answer}_fraction | e.g. smooth-or-featured_smooth_fraction. The fraction of volunteers expected to give this answer to this morphology question. Probably the morphology columns you want. |
| {question}_{answer}_dirichlet | e.g. smooth-or-featured_smooth_dirichlet. The concentration for a Dirichlet distribution (useful for uncertainties). See the paper. |
| warning_galaxy_fails_training_cuts | Marks galaxies between 700px and 1200px, where performance may be lower. See above. |
| cutout_width_arcsec | Width (and height) of cutout in arcseconds |
The following questions and answers are available.
| Question | Answer | Notes |
| smooth-or-featured | smooth | May include face-on lenticulars, which are better identified with e.g. Sersic indices |
| how-rounded | round | |
| how-rounded | in-between | |
| how-rounded | cigar-shaped | |
| smooth-or-featured | featured-or-disk | The question branch most commonly used by researchers |
| disk-edge-on | yes | |
| edge-on-bulge | boxy | |
| edge-on-bulge | none | |
| edge-on-bulge | rounded | |
| disk-edge-on | no | |
| has-spiral-arms | yes | |
| spiral-winding | tight | |
| spiral-winding | medium | |
| spiral-winding | loose | |
| spiral-arm-count | 1 | |
| spiral-arm-count | 2 | |
| spiral-arm-count | 3 | |
| spiral-arm-count | 4 | |
| spiral-arm-count | more-than-4 | Often overlaps with cant-tell |
| spiral-arm-count | cant-tell | Often overlaps with more-than-4 |
| has-spiral-arms | no | |
| bar | strong | Bar strength is a mix of length and width |
| bar | weak | |
| bar | no | |
| bulge-size | dominant | |
| bulge-size | large | |
| bulge-size | moderate | |
| bulge-size | small | |
| bulge-size | none | |
| smooth-or-featured | problem | |
| problem | star | |
| problem | zoom | i.e. bad zoom, a cutout which is too wide |
| problem | artifact | |
| artifact | satellite | |
| artifact | scattered | |
| artifact | diffraction | |
| artifact | ray | |
| artifact | saturation | |
| artifact | other | |
| artifact | ghost | Dichrotic ghosts |
| merging | none | |
| merging | minor_disturbance | |
| merging | major_disturbance | Primarily obvious tidal tails and similar features |
| merging | merger | Primarily "dramatic" ongoing mergers |
| clumps | yes | Not recommended; we are building clump-specific models |
| clumps | no | Not recommended; we are building clump-specific models |
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).
| segmentation_area | Number of pixels included in SourceExtractor++ mask of galaxy (0.1 arcsec/pixel). |
| flux_segmentation | Total VIS flux inside the segmentation mask above. |
| mag_segmentation | As above, converted to magnitude. ```mag = -2.5*log10(flux[muJy])+23.9```. Not technically in MER catalogue. |
| flux_detection_total | VIS flux measured within a Kron aperture in the detection image. FLUX_AUTO in SourceExtractor. |
| flux_vis_1fwhm_aper | VIS flux within an aperture of radius 1 FWHM. |
| mumax_minus_mag | A star/galaxy diagnostic. The morphology catalogue uses the recommended filter MUMAX_MINUS_MAG>=-2.6 to reject stars. |
| mu_max | Peak surface brightness above the background in the detection band (directly from SExtractor) |
| ellipticity | A parametrization of how stretched an object is in the detection band (VIS, here), computed from the minor and major axes of the object itself (directly from SExtractor). [I assume this is the major/minor axis ratio] |
| kron_radius | Major semi-axis (in pixels) of the elliptical aperture used for total (Kron) aperture photometry on the detection image |
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.
Files
morphology_catalogue.csv
Additional details
Dates
- Available
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2025-03-19Initial public release
Software
- Programming language
- Python