The dawn of Galaxy Zoo’s new incarnation – Galaxy Zoo: Cosmic Dawn!

This week, Galaxy Zoo begins its latest incarnation, Galaxy Zoo: Cosmic Dawn, with tens of thousands of new galaxy images now available for you to help classify! These were taken by the Hyper Suprime-Cam (HSC) on board the 8.2m Subaru telescope on the summit of Mauna Kea in Hawaii, as part of the Hawaii Two-0 (H20) survey, a key component to the more ambitious Cosmic Dawn survey.

The Cosmic Dawn Survey is a multi-wavelength survey aiming to understand the co-evolution of galaxies, the dark matter haloes that host them, and their central black holes over cosmic time, all the way from when galaxies first formed in the early Universe. A major part of this is the H20 survey which has obtained ultra-deep Subaru HSC imaging over large and particularly dark areas of the sky. The H20 survey targets two areas of the sky which, as part of the Cosmic Dawn Survey, were observed by the Spitzer Space Telescope in the largest allocation of observing time ever awarded on the spacecraft. When combined with these infrared data, H20 aims to push the boundaries of extragalactic astronomy by studying galaxy evolution out to around 800 million years after the Big Bang. This incarnation of Galaxy Zoo features images from a portion of the sky called the Euclid Deep Field North (EDF-N), from one of the two areas targeted by the H20 survey.

This effort from Galaxy Zoo will therefore also help prepare for the upcoming launch of the Euclid space telescope by the European Space Agency (ESA) in 2023, with the classifications you make now helping to guide what Euclid will observe in more detail with its even higher resolution imaging in visible light and the infrared.

Compared to previous incarnations of Galaxy Zoo such as those using SDSS and DeCALS images, H20 enables us to see fainter and more distant galaxies from earlier in the Universe’s history, thanks to higher angular resolution of HSC and greater depth of the survey. However, deeper imaging also means we can observe many more distant galaxies in the same patch of sky, so the images you will see may often appear redder and blurrier than you might expect.

The Galaxy Zoo decision tree of questions has been modified so that your classifications can help refine the software used by the H20 team, and perhaps that of future Galaxy Zoo incarnations as well. For example, the “Star or Artifact” question now includes a “Bad Image Zoom” option, while selecting “Non-star Artifact” will allow you to classify the type of any image artifact you come across, such as satellite trails. In the future, Galaxy Zoo will also be running a simplified decision tree of questions for some of the fainter distant galaxies, as their lower resolution prevents many features from being identified.

Also, look out for any galaxies containing bright clumps! We’ve added a question about these, as they can help us understand the period of intense star formation that took place in the early Universe.

Finally, we are also asking volunteers to tag any extremely red objects, or those with a lens or arc features, in the Talk board, using the “Done & Talk” option. These are rare objects that we don’t want to miss, especially for such distant galaxies!

We are excited about the new images and looking forward to seeing what you’ll discover. Join the classification now!

James Pearson, Galaxy Zoo and H2O teams

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