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Introducing Your New AI Assistant
Of all the galaxies in the sky, which should you look at first?
You might have noticed that our most recent galaxies, taken by Hyper Suprime-Cam in Hawaii, have often been less detailed than our previous galaxies. This happened because we were very generous when selecting which galaxies to include. We had never classified galaxies from this instrument before and we were curious to see what you would find.
Reviewing the classifications so far, the clear majority of galaxies – as many as 90% – were voted as either “smooth” or “problem”. That suggests we’re showing you too many “blobs” and too few interesting featured galaxies.
To fix this, I’m happy to announce a new Galaxy Zoo feature that will prioritise showing you detailed and unusual galaxies.
We’re doing this with an AI algorithm we affectionately call Zoobot. Zoobot tries to classify galaxies based on what volunteers have said before for similar galaxies. If you’d like to test out Zoobot on some DECaLS galaxies, you can play with it here.
Zoobot is very good at simple classification tasks like recognising a smooth galaxy as smooth. We can therefore avoid showing you galaxies that Zoobot already considers to be very smooth. Specifically, we will now avoid showing galaxies where Zoobot is 90% confident that fewer than 2 out of 10 volunteers would click “featured”.
How will the galaxies you see change? You will see fewer totally smooth galaxies and more of everything else. Below are random examples of galaxies on Galaxy Zoo before (left) and after (right) switching on Zoobot.
Galaxies shown on Galaxy Zoo before activating Zoobot (left) and after (right). There will be fewer totally smooth and “bad zoom” images, and more featured and unusual galaxies.
Zoobot will continue to learn from you as you classify galaxies. It should get better and better at removing extremely smooth galaxies over time. If Zoobot learns that a galaxy might not be smooth after all – that is, if Zoobot changes it’s mind – the galaxy will be shown.
You might remember Zoobot from the “Enhanced” workflow we ran during GZ DECaLS. There, Zoobot tried to prioritise galaxies which, if labelled by you, would most help it learn. This worked well and helped us train the improved version of Zoobot that we’re using now. This new system is similar; we’re showing you the galaxies where volunteer labels are most useful for Zoobot and for science. We’re just using a much more straightforward rule to pick these.
Your time is precious. Galaxy Zoo volunteers can recognise and classify the detailed features of galaxies in ways that Zoobot can’t – and nor can any other algorithm. More than that, humans have a unique ability to spot things that look just a little bit weird. Volunteers talking about strange objects has led to some of our favourite discoveries, including the Voorwerpen. Using Zoobot means you will be much more likely to see more diverse galaxies and come across more weird and wonderful objects. We also have another surprise planned around these – stay tuned…
Mike, on behalf of the Galaxy Zoo team
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
From Galaxy Zoo to JWST – dust and gravitational lensing
My previous post on the Zooniverse blog gave some history of how having Galaxy Zoo participants call attention to backlit galaxies led to the galaxy pair VV191 being on the schedule for observations with the James Webb Space Telescope (JWST), what we expected to learn, and a final note to watch for the outcome in mid-2023. It is not yet mid-2023, and here we are with the outcome. A short-notice schedule reshuffling (which I suspect was enabled by how rapidly the commissioning process went, and the fact that this was a brief series of observations totaling only 30 minutes of exposure) brought these observations up to mid-July of this year.
Short form: we got what we came for, and the Universe provided interesting bonuses. NASA is releasing this nicely processed rendering of our combined Hubble and HST image sets today. The Hubble near-ultraviolet and red-light data are shown in blue, with green and red showing progressively deeper-infrared bands from JWST.
The dust in the spiral arms of the big spiral (VV191b) stands out where it is silhouetted by the bright light of the elliptical galaxy VV191a. In fact, the dusty arms can be traced farther from the spiral’s center than even the JWST data show bright spiral arms, cutting off very sharply at a radius of 20 kiloparsecs (66,000 light-years, about 8 times the distance from us to our own galactic center). This testifies to the past history of star formation in VV191b. Having a map of the light transmitted through the dust at different wavelengths lets us examine the so-called reddening law, the relative amount of light blocked at different wavelengths. This is characteristic of the sizes of interstellar dust grains, and how they are distributed on scales smaller than we can resolve in our data. This RGB display shows the transmitted light at wavelengths 0.6-1.5 microns (plus background galaxies and foreground star-forming regions we masked in numerical analysis). The dust lanes are redder (or, to my eye, browner) than the surroundings, illustrating how blue light is more effectively blocked than red (and red more effectively than deeper red, and both of those compared to near-infrared, until at the 4.4-micron longest-wavelength band of JWST’s NIRCam detectors the absorption is too small to measure)
Analyzing these maps pixel by pixel (after matching the image resolutions; JWST images at 1.5 microns are still sharper than HST data at 0.6 microns, a welcome outcome which was not guaranteed) we can ask more precisely how the dust in VV191b reddens light passing through the galaxy. The answer is – a lot like typical dust grains in our part of the Milky Way. This was a bit unexpected first because while both are large spiral galaxies, VV191b is considerably larger than the Milky Way, and we are examining its outermost spiral features in ways that are very difficult in our own Galaxy. Second, where there are clumps with more dust than their surrounding, so smaller that our data blur them together with their surroundings, we will measure less reddening than we would if we could use single stars as background sources (“greyer extinction”).
There is more to learn, but these data are a great step. The research paper has been submitted to the Astronomical Journal, and is now under review; a preprint version is at https://arxiv.org/abs/2208.14475
In our first looks at the JWST data, something else became obvious. Near the core of the elliptical galaxy VV191a is a very red arc appearing to partly wrap around its nucleus. Opposite the nucleus is a much smaller red spot. Together these fit perfectly for being a gravitational lens, light from a galaxy over 10 billion light-years away, seen as the gravity of the foreground galaxy distorts and magnifies it. While hundreds of such lenses are known from more distant galaxy clusters (eagerly sought to improve our knowledge of very early galaxies), only a handful of single-galaxy lenses have been found so nearby. (There is a bit of irony in finding this – the overall project these data came from, led by Rogier Windhorst at Arizona State University, acquired the name PEARLS, Prime Extragalactic Areas for Reionization and Lensing Science, so now VV191 honestly belongs through that L). Team members Giovanni Ferrami and Stuart Wyithe from the University of Melbourne in Australia were able to get a good match to the lensing distortion using the galaxy’s light distribution and estimating the background galaxy distance from its colors. In fact, because everything is connected if you look closely, this measurement tells how much mass including dim dwarf stars plus dark matter is in that part of the foreground galaxy. A second distant background galaxy has only a single image, but is distorted in a way similar to the arc. These distant galaxies are so red that the lensing was not seen in the Hubble images, even though the arc was obvious in each of the JWST images. This crop shows the arc and its counterimage on either side of the elliptical-galaxy core.
Around the edge of the image above (which comes from only a single one of the eight near-IR detectors in the NIRCam instrument), many other background galaxies appear (they are everywhere with JWST, even showing up the recent Jupiter image). To the upper left of the elliptical galaxy are two patchy spiral galaxies that look almost the same size but have very different colors (one so red that, again, Hubble data did not show it). Without further data they could be at similar distances but one so dusty that dust reddening change sits colors, something we need to know more about to interpret incoming results in the early Universe). Or the red one could be very bright and at a much higher redshift – in an expanding Universe, very distant objects can look large although dim (more or less because they were much closer to us when that light was emitted). This means that galaxies of the same actual size will look nearly the same size to us at any distance beyond about 5 billion light-years (although progressively more redshifted and a great deal dimmer with distance).
Some readers may have followed the public discussion about how JWST calibration uncertainties (since it’s so early in what we hope will be a very long mission) may have affected initial attempts to identify the highest-redshift galaxies. In this light, this was a very good project to do so early – for our dust analysis, all that matters is how the brightness in various parts of each galaxy is compared, using uniformity within a single detector and not at all needing to know its absolute sensitivity. To get the absolute sensitivity for colors of the gravitationally lensed galaxy (which we did not initially know we’d need to do), we were able to combine a Sloan Digital Sky Survey spectrum of the elliptical galaxy with the very well-known near-IR properties of giant ellipticals to reduce calibration uncertainties.
As said above, this all comes from 30 minutes’ worth of data using 1/8 of the field of view of JWST’s NIRCam camera. There are a lot more galaxies out there. Watch this space as we try to work out the best way to do JWST Galaxy Zoo.
Our last night at the telescope
The story so far: on the first night we were able to observe until 02:00 before the weather forced us to close. The following three nights we were confined to the Residencia, the place where they keep all the astronomers when they are not observing. Much to our surprise, this morning we awoke to a sky only sparsely covered by clouds, instead of being in the middle of one. Maybe we have a chance of observing something tonight?
== 19:30 ==
As the weather has cleared somewhat on Roque de Los Muchachos, La Palma, we have received permission to go to the telescope tonight. We’ve just arrived and started taking the first couple of calibration images with much enthusiasm.
A bit about the telescope itself: we’re using a telescope called the Isaac Newton Telescope (INT). It is a Cassegrain reflector telescope with a ~2.5m primary mirror that weighs ~4000kg!
It takes a while for the telescope to take all the calibration images (biases, arcs and flats), so we were able to enjoy the sunset right before -hopefully- a very busy night.
== 22:00 ==
Unfortunately the weather has taken a turn for the worse. We cannot open the dome of the telescope as the humidity is too high. We’ve had our first cups of coffee and are settling in for the night, while keeping an eye on the humidity sensor.
As tonight will be our last night at the telescope and we’ve had bad luck with the weather the last couple of days, we are very hopeful to observe some galaxies tonight. So far we were able to observe only one galaxy before we had to close on the first night. At this point we will be grateful for any data that comes in, even one more galaxy would double our current sample size!
== 00:45 ==
We’re still not able to open, humidity is at 100% and we cannot see any stars. The highlight of the last couple of hours was exploring the library in the INT and listening to an old cassette tape of Joseph and the technicolour dream coat. None of the other tapes work.
== 04:00 ==
We’ve had a popcorn and pizza break, drank multiple cups of coffee and explored most of the telescope building. However, unfortunately we’ve not been able to use the telescope today – the weather gods seem determined to prevent us from getting any data. With any luck we’ll be back next year to try again.
Observing bars in La Palma
As some might remember, in our last paper (which can be found here), we studied differences between weak and strong bars. One of our results was that star forming galaxies with stronger bars have significantly higher star formation in their centres compared to galaxies with weaker bars. This might be due to differences in the gas flows induced by the different types of bars. To investigate this, we selected a sample of 21 galaxies from Galaxy Zoo, which we plan to observe over the next couple days.
The relationship between galactic bars and star formation has long been up for debate. Galactic bars are vast structures of co-orbiting gas, dust and stars that form directly across the galactic nucleus. It is thought that gas flows along the arms of the bar into the centre, increasing the central gas density. As gas density increases, the star formation rate would also. So, that should be the answer then? However, in reality, it is not so simple.
There are many different kinds of bars, with varying characteristics such as strengths and orientations. A galaxy might contain a very strong bar – where it clearly dominates even over the galactic disk – or it could have a very weak bar – where the disk dominates over it. So, we need to ask ourselves further, is the gas flow and resultant star formation higher in galaxies with strong bars? What about weak bars? Does it even change at all if we compare either type of bar to galaxies which have no bars?
These are the questions we are going to answer at the Isaac Newton Telescope, or INT, on the island of Santa Cruz de la Palma. With a sample of 21 galaxies characterised by Galaxy Zoo – 7 strongly barred, 7 weakly barred and 7 with no bars at all – we are investigating if any relation between star formation rate and bar strength exists. An example of each type of galaxy in our sample is shown below. On the left is a galaxy with no bar at all, while on the right is a galaxy with a strong bar. The strong bar clearly dominates over the disk of the galaxy. The middle panel shows a galaxy with a much weaker bar, where the disk dominates over the disk galaxy.
To investigate this, we must turn to spectroscopy. Rather than utilise images, such as the ones above, we align a spectroscopic slit along and perpendicular to the bar direction on the image. The spectroscope will split the incoming light into a spectrum of wavelengths, where we will be able to find any spectral signatures of elements within the bars themselves.
There are two chemical signatures of star formation that we are looking for. The first, an indirect measurement, is looking for Hydrogen Alpha, or Hα. If there is a much higher abundance of Hα at the core of a galaxy with a strong bar, weak bar or not, it is very likely that there is a higher gas density. Ergo, there is a higher star formation. The second signature we are looking for is Oxygen III, or O[III]. O[III] is highly ionised only typically exists in areas where there are high rates of the star formation; the newly born stars being the cause of the ionisation. This would be direct evidence of higher star formation.
So, what do we find? Thus far, due to the adverse weather conditions caused by tropical storm Hermine on La Palma, we have set our spectroscopic observations on a single strongly barred galaxy. We have extracted the spectrum, removed any sources of contamination and reduced to only that of the bar and galactic nucleus. The top image is the spectrum from the slit at ninety degrees perpendicular to the bar direction and the bottom is aligned along it.
The top spectrum (perpendicular to the bar) appears to be almost empty, with only noise present. Along the bar, however, we get a very strong emission line at precisely 6562.801Å. Guess which wavelength Hα happens to rest at? Precisely the same!
This is certainly a promising initial result. If the abundance of Hα is much higher along bars than not, then this is certainly a case for them enhancing star formation! The next steps are to confirm this finding by taking observations for the rest of our sample. Once the weather clears up on La Palma, we will be aiming to finally answer the question, what do galactic bars do for star formation? Enhance, prevent or nothing? Well, it looks like enhancing has won the first point!
We will keep you updated!
David, Tobias and Chris
In the News – Ringed Galaxies from GZ Mobile
Thanks to you, we’ve found 40,000 new ringed galaxies – about six times more than all the ringed galaxies anyone has ever found before! The Royal Astronomical Society were impressed enough to share the news in a press release here.
I launched the Rings Challenge here on this blog ten months ago, asking for your help searching for galaxies with rings around them. I wasn’t sure if anyone would be interested in using the new mobile project we made. Ten months later, you’ve made a million swipes on 100,000 galaxies. I’m so grateful.
Rings are rare. To help you find them, I created an automatic assistant. I used the first half of your swipes to teach an artificial intelligence algorithm what rings look like. Then I set the algorithm searching a million DESI galaxies to find more rings. Finally, I took the galaxies the AI thought might have rings and asked you to check them with the second half of your swipes. This two step approach let us both search many galaxies quickly and have human eyes vet all of our discoveries.
This is the first major science result from the new GZ Mobile project. Making an app wasn’t part of the original plan – the first iPhone launched three weeks after GZ, 15 years ago this month – but it’s now a crucial tool for hunting specific galaxies quickly. I hope you’ll join us for the next search.
You can find more technical details on the machine learning on my personal blog.
Apologies to ChristineM, who many months ago correctly point out that I should technically call them “ringed” galaxies rather than “ring” galaxies.
Happy Birthday (& a belated announcement)
Firstly, happy 15th birthday to Galaxy Zoo and thank you to all those who have made it a success over the last decade-and-a-half. Whether you’re a regular on Talk, and original classifier, a member of the science team or someone who has been inspired by the project to find out a little more about science, thank you!
Looking back at the BBC article that started everything, I notice we ‘hoped’ that 30000 people would take part in our project. We blew past that target early on, and haven’t looked back since. The results of the project have told us much about galaxy history, inspired novel machine learning approaches to science, helped us build the broader Zooniverse and much more. It still stuns me to think that there’s a Hubble Space Telescope program following up on Galaxy Zoo discoveries, and there is still much more science to come. (It’s not ridiculous to think that JWST, the new space telescope which will release its first image tonight, will soon follow up on a Galaxy Zoo discovery, or provide images for a future version of the project). My failure to anticipate this glorious feature came because we simply underestimated the passion, ability and enthusiasm of all of you to help learn a little bit more about the Universe.
I’m also very proud of the PhD students who have worked with the Galaxy Zoo team to make use of our data, and help lead the project. Several generations have now successfully graduated, and there’s much more to come from the current cohort. Since September, the project has been led by the immensely impressive Karen Masters, who has taken over from me as Principal Investigator, with assistance from Brooke Simmons (Deputy PI), Sandor Kruk (Project Scientist), Becky Smethurst (Deputy Project Scientist), and Mike Walmsley (Technical Lead). With them the project is in excellent hands, and I’m looking forward to the next decade-or-so of galaxy science, powered by you, the wonderful denizens of the Zoo.
VV191: from Galaxy Zoo to JWST
Almost 15 years ago, what first attracted me to be involved with Galaxy Zoo was the ability of participants to pick out rare galaxy types, especially silhouetted or overlapping galaxy systems. These highlight the effects of dust in the foreground galaxy on passing light, and offer ways to study the dust which are complementary to, for example, observations in the deep infrared where the dust itself shines, giving off the energy it absorbs from starlight. Visible-light measurements of backlit galaxies show us the dust no matter how cold it might be, where it can hide from IR detection, and at the high resolution available to optical telescopes (including the Hubble Space Telescope) rather than the more modest, wavelength-limited resolution we can achieve at longer wavelength. Better measurements of dust in galaxies affect our understanding of their energy output, stellar content, and even our view of the more distant Universe. Galaxy Zoo volunteers contributed to a catalog of nearly 2000 suitable galaxy pairs from the first iteration of the project, since expanded from Galaxy Zoo 2, GZ Hubble, and the most recent examinations using the Legacy Survey data. We have used this list for number of followup studies – although, truth be told, I have also been distracted by other rare systems found by volunteers (cough, Hanny’s Voorwerp and the Voorwerpjes, for example).
The backlit-galaxy system VV191 was first reported in the Galaxy Zoo forum as a possible galaxy merger, by user Goniners on November 2, 2007. Despite its near-perfect geometry for study of foreground dust, VV191 had eluded our earlier searches because the inner regions, where one can see that this is a superposition of undisturbed galaxies rather a merging galaxy pair, are saturated in prints of the Palomar Sky Survey, which was the best visible-light survey before the Sloan Digital Sky Survey. At the time VV191 was selected for further study, catalogs showed a substantial redshift difference between the two galaxies, which is desirable so the two galaxies are unlikely to be physically interacting with each other, and light from the background galaxy scattered by the dust becomes much fainter. That has been revised by later data which put the redshifts closer; we can’t win them all, though the two galaxies are very symmetric and undisturbed in all our later data.
(Hubble red-light image of VV191, showing silhouetted dust in the foreground spiral arms)
We got a closer look with the STARSMOG project led by colleague Benne Holwerda, which was a Hubble snapshot program – one where short exposures are inserted into gaps in the telescope schedule, much like the Zoo Gems gap-filler project. STARSMOG drew promising overlapping-galaxy pairs from Galaxy Zoo forum posts and the GAMA (Galaxy And Mass Assembly) project. Over several years, it acquired images of 55 galaxy pairs of interest. Among those was VV191, generating a very detailed map of the dust silhouette of the spiral galaxy. This was one of the galaxy pairs analyzed in a project based on the master’s thesis work by Sarah Bradford at the University of Alabama which went into a poster presentation at the January 2017 meeting of the American Astronomical Society in Texas. In fact, I used a low-contrast version of the VV191 image as the poster background. (The poster should still just be legible in this compressed PNG version):
The data quality for VV191 stood out, because the background elliptical galaxy has its brightest region right behind the edge of the dust in the spiral. We then had a 2-dimensional map of how much light gets through the dust in the spiral at the wavelengths included in that single observation. The poster was viewed by my longtime collaborator Rogier Windhorst, who is one of the interdisciplinary scientists with the James Webb Space Telescope (JWST) project. In this capacity, he had an allocation of so-called GTO (guaranteed-time) observations, asked what we could do with JWST. Rogier was struck by these images, and wondered what we could add to the science output with a little bit of JWST observing time.
This led to a plan of tracking the dust signature from ultraviolet to infrared in a single galaxy with a single technique. First Hubble had to do its part with more data, using not only its high resolution but UV sensitivity. We got Hubble images in filters around 2250 and 3360 Angstroms (0.22 and 0.34 microns) , with the short end limited mostly by the elliptical galaxy being so faint in the deeper UV that we couldn’t detect its light well enough in reasonable exposure times. These data have been processed, so we are ready for the next step – JWST. Its near-infrared camera (NIRCAM) will observe this system in four filters from 0.9-4.0 microns wavelength (two at a time since the camera can use short- and long-wavelength channels simultaneously). The wavelengths are chosen to trace the way the dust effects fall off toward longer wavelengths, which is affected both by the sizes of the interstellar dust grains and how strongly they are clumped together. One filter matches one of the wavelengths at which small grains (or indeed large molecules, so-called PAH particles) emit, so we might be able to tell how they correlate with the larger particles blocking most of the light.
Because of the enormous sensitivity of JWST and NIRCAM, each filter is exposed for only 15 minutes to get very high measurement accuracy. (The telescope will probably take longer than that to point to VV191, depending on what it’s doing beforehand). Based on when JWST can view this part of the sky, these observations are most likely to be made between December 2022-March 2023, or May-July of 2023 (we should know more in a couple of weeks when the first year’s observation schedule is released). Watch this space…
Zoo Gems – Hubble does Galaxy Zoo(s)
Since mid-2018, the Hubble Space Telescope has taken occasional short-exposure images, filling what would otherwise be gaps in its schedule, of galaxies in the list from “Gems of the Galaxy Zoos” (otherwise known as Zoo Gems). The Zoo Gems project just passed a milestone, with acceptance of a journal paper describing the project, including how votes from Galaxy Zoo and Radio Galaxy Zoo participants were used to select some of the targeted galaxies, and acting as a sort of theatrical “teaser trailer” for the variety of science results coming from these data. (The preprint of the accepted version is here; once it is in “print”, the Astronomical Journal itself is now open-access as of last month). The journal reviewer really liked the whole project: “The use of the Galaxy Zoo project’s unique ability to spot outliers in galaxy morphology and use this input list for a HST gap filler program is a great use of both the citizen science project and the Hubble Space Telescope” and “I think it is a wonderful program with a clever, useful, and engaging use of both SDSS and Hubble.” (We seldom read statements that glowing in journal reviews).
Zoo Gems got its start in late 2017, when the Space Telescope Science Institute (STScI) asked for potential “gap-filler” projects. Even with what are known as snapshot projects, there remained gaps in Hubble’s schedule long enough to set up and take 10-15 minutes’ worth of high-quality data. We put together a shockingly brief proposal (STScI wanted 2 pages, originally to gauge interest) and were very pleased to find it one of 3 selected (the other two also deal with galaxies. Makes sense to me). We had long thought that the ideal proposal for further observations of some of the rare objects identified in Galaxy Zoo ran along the lines of “Our volunteers have found all these weird galaxies. We need a closer look”. That was essentially what the gap-filler project offered.
We estimated that we could identify 1100 particularly interesting galaxies (where short-exposure Hubble images would teach us something we could foresee) from Galaxy Zoo and Radio Galaxy Zoo. We were allocated 300 by STScI, so some decisions had to be made. A key feature of our project was the wide range of galaxy science goals it could address, so we wanted to keep a broad mix of object types. Some types were rare and had fewer than 10 examples even from Galaxy Zoo, so we started by keeping those. When there were many to choose from, we did what Galaxy Zoo history (and STScI reviewers) suggested – asked for people to vote on which merging galaxies, overlapping galaxies, and so on should go into the final list. This happened in parallel for Galaxy Zoo and Radio Galaxy Zoo objects (the latter largely managed by the late Jean Tate, not the last time we are sadly missing Jean’s contributions as one of the most assiduous volunteers). Even being on that observing list was no guarantee – gap-filler observations are selected more or less at random, taking whichever one (from whichever project’s list) fits in a gap in time and location in the sky. The STScI pilot project suggested that we could eventually expect close to half to be observed; we are now quite close to that, with 146 observations of 299 (one became unworkable due to a change in how guide stars are selected by Hubble). These include a fascinating range of galaxies. From Galaxy Zoo, the list includes Green Pea starburst galaxies, blue elliptical and red spiral galaxies, ongoing mergers, backlit spiral galaxies, galaxies with unusual central bars or rings, galaxy mergers with evidence for the spiral disks surviving the merger or reappearing shortly thereafter, and even a few gravitational lenses. From Radio Galaxy Zoo, we selected sets of emission-line galaxies (“RGZ Green”) and possibly spiral host galaxies of double radio sources (SDRAGNs, in the jargon, and so rare that we’ve more than doubled the known set already). Both kinds of RGZ selection were largely managed by Jean Tate, who we are missing once again. By now, of 300 possible objects, 146 have been successfully observed. One can no longer be observed due to changes in Hubble’s guide-star requirements, and two failed for onboard technical reasons (it was during one of those, a few months ago, that a computer failure sent the telescope into “safe mode”; I have been assured that it was not our fault).
Zoo Gems images show that every blue elliptical galaxy observed shows a tightly wound spiral pattern near the core, so small that it was blurred together in the Sloan Survey images used by Galaxy Zoo, and broadly fitting with the idea that these galaxies result from at least minor mergers bringing gas and dust into a formerly quiet elliptical system.
There is much more to come as harvesting the knowledge from these data continues. Already, a project led by Leonardo Clarke at the University of Minnesota used Zoo Gems images to demonstrate that Green Peas are embedded in redder surroundings, possibly the older stars in the galaxies that host these starbursts. Beyond these, these data can be used to examine the histories of poststarburst galaxies, dynamics and star-formation properties of 3-armed spirals, and nuclear disks and bars – some of these show galaxies-within-galaxies patterns where the central region nearly echoes the structure of the whole galaxy.
While going through some of the Zoo Gems images to see which should go in various montages in this paper, I considered the multilayer overlapping galaxy system including UGC 12281. It didn’t go into the paper, but the visual sense of deep space in this image is so profound that it became the 2nd most-retweeted thing I’ve sent out in more than 10 years.
In presenting these data, we wanted to make the case for the value of wide-ranging, even short, programs such as this. These gap-filler projects are continuing with Hubble, until STScI starts to have trouble filling the gaps and needs to call for more projects. Premature as it seems, I can’t help musing that someone may eventually work out a low-impact way for the James Webb Space Telescope to make brief stopovers as it slews between long-exposure targets – we have suggestions…
Data from the Zoo Gems project (like the other gap-filler programs, Julianne Dalcanton’s program on Arp peculiar galaxies and the one on SWIFT active galaxies led by Aaron Barth) are immediately public, accessible in the MAST archive under HST program number 15445 (the others are 15444 and 15446). Claude Cornen maintains image galleries for the Zoo Gems, Arp and SWIFT projects in Zoo Gems Talk. Our thanks go to everyone who helped draw attention to these galaxies, or voted in the Zoo Gems object selection.
Announcing: Jan 13 press conference on Galaxy Zoo: Clump Scout results
I’m Nico, a PhD student with the Galaxy Zoo team, and I have an exciting announcement. About a year ago I wrote that classifications on the Galaxy Zoo: Clump Scout project had just finished. Now, with the first results nearing publication, the American Astronomical Society (AAS) has chosen Clump Scout to present its findings at an official press conference on Thursday, January 13 from 4:15-5:15pm Eastern Time (or 9:15-10:15pm GMT for our UK visitors). We’re very excited to finally share these results with our volunteers!
The press conference is free and open to all, so if you took part in the project, we encourage you to tune in to learn more about where your efforts have gone. (Or, if you’ve never heard of the Clump Scout project before, now is a great chance to learn!) I’ll spend a few minutes explaining why we created the project, and describe a few clues we’ve found as to the last 10 billion years of galaxy evolution. There will also be 4 other speakers presenting about their own citizen science work, so it will be a thorough tour of what’s going on in people-powered astronomy today.
We hope you can join us!
How to join:
You watch via YouTube live stream on AAS’s YouTube channel: https://www.youtube.com/c/AASPressOffice
PS. For more galaxies at the AAS (although not Galaxy Zoo directly), also see our PI Karen Masters talking about the completion of the MaNGA Galaxy Survey, Tue 11th Jan in the 2.15pm ET Press Conference. MaNGA the survey Galaxy Zoo: 3D was designed to help analyse; and look out for more crowd-sourcing projects to come from this complex data now it’s all publicly available, as well as much more use of the Galaxy Zoo: 3D classifications.