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Galaxy Zoo: Cosmic Dawn -- morphological classifications for over 41,000 galaxies in the Euclid Deep Field North from the Hawaii Two-0 Cosmic Dawn survey

James Pearson, Hugh Dickinson, Stephen Serjeant, Mike Walmsley, Lucy Fortson, Sandor Kruk, Karen L. Masters, Brooke D. Simmons, R. J. Smethurst, Chris Lintott, Lukas Zalesky, Conor McPartland, John R. Weaver, Sune Toft, Dave Sanders, Nima Chartab, Henry Joy McCracken, Bahram Mobasher, Istvan Szapudi, Noah East, Wynne Turner, Matthew Malkan, William J. Pearson, Tomotsugu Goto, Nagisa Oi

Abstract

We present morphological classifications of over 41,000 galaxies out to $z_{\rm phot}\sim2.5$ across six square degrees of the Euclid Deep Field North (EDFN) from the Hawaii Twenty Square Degree (H20) survey, a part of the wider Cosmic Dawn survey. Galaxy Zoo citizen scientists play a crucial role in the examination of large astronomical data sets through crowdsourced data mining of extragalactic imaging. This iteration, Galaxy Zoo: Cosmic Dawn (GZCD), saw tens of thousands of volunteers and the deep learning foundation model Zoobot collectively classify objects in ultra-deep multiband Hyper Suprime-Cam (HSC) imaging down to a depth of $m_{HSC-i} = 21.5$. Here, we present the details and general analysis of this iteration, including the use of Zoobot in an active learning cycle to improve both model performance and volunteer experience, as well as the discovery of 51 new gravitational lenses in the EDFN. We also announce the public data release of the classifications for over 45,000 subjects, including more than 41,000 galaxies (median $z_{\rm phot}$ of $0.42\pm0.23$), along with their associated image cutouts. This data set provides a valuable opportunity for follow-up imaging of objects in the EDFN as well as acting as a truth set for training deep learning models for application to ground-based surveys like that of the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) collaboration and the newly operational Vera C. Rubin Observatory.

Galaxy Zoo: Cosmic Dawn -- morphological classifications for over 41,000 galaxies in the Euclid Deep Field North from the Hawaii Two-0 Cosmic Dawn survey

Abstract

We present morphological classifications of over 41,000 galaxies out to across six square degrees of the Euclid Deep Field North (EDFN) from the Hawaii Twenty Square Degree (H20) survey, a part of the wider Cosmic Dawn survey. Galaxy Zoo citizen scientists play a crucial role in the examination of large astronomical data sets through crowdsourced data mining of extragalactic imaging. This iteration, Galaxy Zoo: Cosmic Dawn (GZCD), saw tens of thousands of volunteers and the deep learning foundation model Zoobot collectively classify objects in ultra-deep multiband Hyper Suprime-Cam (HSC) imaging down to a depth of . Here, we present the details and general analysis of this iteration, including the use of Zoobot in an active learning cycle to improve both model performance and volunteer experience, as well as the discovery of 51 new gravitational lenses in the EDFN. We also announce the public data release of the classifications for over 45,000 subjects, including more than 41,000 galaxies (median of ), along with their associated image cutouts. This data set provides a valuable opportunity for follow-up imaging of objects in the EDFN as well as acting as a truth set for training deep learning models for application to ground-based surveys like that of the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) collaboration and the newly operational Vera C. Rubin Observatory.

Paper Structure

This paper contains 24 sections, 1 equation, 21 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Imaging Data
  3. Cosmic Dawn and Hawaii Twenty Square Degree surveys
  4. Subject selection
  5. Cutout creation and upload
  6. Metadata
  7. Methods
  8. Decision tree changes
  9. Tagging extremely red objects
  10. Public launch
  11. Zoobot active learning
  12. Data aggregation
  13. Volunteer weightings and redshift debiasing
  14. Galaxy Zoo Mobile gravitational lenses
  15. Results
  16. ...and 9 more sections

Figures (21)

  • Figure 1: Distribution of photometric redshifts for the objects in GZCD as measured by the H20 pipeline. Those for which the pipeline failed to produce suitable photometric redshift estimates are not included. These distributions cover the data set so stars, artifacts and those with 'bad image zoom' have not been excluded.
  • Figure 2: Distribution of HSC-$g$, -$r$, and -$i$ band apparent magnitudes for the objects in GZCD as measured by the H20 pipeline. Those for which the pipeline failed to produce suitable photometric models are not included. These distributions cover the data set so stars, artifacts and those with 'bad image zoom' have not been excluded.
  • Figure 3: Example cutout images shown to volunteers on Zooniverse as part of GZCD. Clockwise from top left, the galaxies have angular effective radii of 1.106, 1.815, 2.483 and 1.441 arcseconds, apparent HSC-$i$ band magnitudes of 19.870, 19.354, 17.356 and 19.150, and photometric redshifts of 0.768, 0.406, 0.301 and 0.398.
  • Figure 4: GZCD decision tree of questions presented to volunteers for classifying the morphology of the central object in each subject image. Questions sharing the same colour are on the same tier of branching in the decision tree.
  • Figure 5: Histogram of the number of volunteer classifications ('votes') made per week across the whole run of GZCD.
  • ...and 16 more figures