Publications by Chris Lintott

Galaxy Zoo: Morphological classifications for 120 000 galaxies in HST legacy imaging

Monthly Notices of the Royal Astronomical Society 464 (2017) 4176-4203

KW Willett, MA Galloway, SP Bamford, CJ Lintott, KL Masters, C Scarlata, BD Simmons, M Beck, CN Cardamone, E Cheung, EM Edmondson, LF Fortson, RL Griffith, B Häußler, A Han, R Hart, T Melvin, M Parrish, K Schawinski, RJ Smethurst, AM Smith

© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour-composite images. Images in GZH were selected from various publicly released Hubble Space Telescope legacy programmes conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to z ~ 1. The bulk of the sample is selected to have mI814W < 23.5, but goes as faint as mI814W < 26.8 for deep images combined over five epochs. The median redshift of the combined samples is 〈 z 〉 = 0.9 ± 0.6, with a tail extending out to z ≃ 4. The GZH morphological data include measurements of both bulge- and disc-dominated galaxies, details on spiral disc structure that relate to the Hubble type, bar identification, and numerous measurements of clump identification and geometry. This paper also describes a new method for calibrating morphologies for galaxies of different luminosities and at different redshifts by using artificially redshifted galaxy images as a baseline. The GZH catalogue contains both raw and calibrated morphological vote fractions for 119 849 galaxies, providing the largest data set to date suitable for large-scale studies of galaxy evolution out to z ~ 1.

Galaxy Zoo: Quantitative visual morphological classifications for 48 000 galaxies from CANDELS

Monthly Notices of the Royal Astronomical Society 464 (2017) 4420-4447

BD Simmons, C Lintott, KW Willett, KL Masters, JS Kartaltepe, B Häußler, S Kaviraj, C Krawczyk, SJ Kruk, DH McIntosh, RJ Smethurst, RC Nichol, C Scarlata, K Schawinski, CJ Conselice, O Almaini, HC Ferguson, L Fortson, W Hartley, D Kocevski, AM Koekemoer, A Mortlock, JA Newman, SP Bamford, NA Grogin, RA Lucas, NP Hathi, E McGrath, M Peth, J Pforr, Z Rizer, S Wuyts, G Barro, EF Bell, M Castellano, T Dahlen, A Dekel, J Ownsworth, SM Faber, SL Finkelstein, A Fontana, A Galametz, R Grützbauch, D Koo, J Lotz, B Mobasher, M Mozena, M Salvato, T Wiklind

© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We present quantified visual morphologies of approximately 48 000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. 90 per cent of galaxies have z ≤ 3 and are observed in rest-frame optical wavelengths by CANDELS. Each galaxy received an average of 40 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. We apply a consensus-based classifier weighting method that preserves classifier independence while effectively downweighting significantly outlying classifications. After analysing the effect of varying image depth on reported classifications, we also provide depth-corrected classifications which both preserve the information in the deepest observations and also enable the use of classifications at comparable depths across the full survey.Comparing the Galaxy Zoo classifications to previous classifications of the same galaxies shows very good agreement; for some applications, the high number of independent classifications provided by Galaxy Zoo provides an advantage in selecting galaxies with a particular morphological profile, while in others the combination of Galaxy Zoo with other classifications is a more promising approach than using any one method alone.We combine the Galaxy Zoo classifications of 'smooth' galaxies with parametric morphologies to select a sample of featureless discs at 1 ≤ z ≤ 3, which may represent a dynamically warmer progenitor population to the settled disc galaxies seen at later epochs.

Science learning via participation in online citizen science

Journal of Science Communication 15 (2016)

K Masters, EY Oh, J Cox, B Simmons, C Lintott, G Graham, A Greenhill, K Holmes

We investigate the development of scientific content knowledge of volunteers participating in online citizen science projects in the Zooniverse ( We use econometric methods to test how measures of project participation relate to success in a science quiz, controlling for factors known to correlate with scientific knowledge. Citizen scientists believe they are learning about both the content and processes of science through their participation. We don't directly test the latter, but we find evidence to support the former - that more actively engaged participants perform better in a project-specific science knowledge quiz, even after controlling for their general science knowledge. We interpret this as evidence of learning of science content inspired by participation in online citizen science.

Extended X-ray emission in the IC 2497 - Hanny's Voorwerp system: Energy injection in the gas around a fading AGN

Monthly Notices of the Royal Astronomical Society 457 (2016) 3629-3636

LF Sartori, K Schawinski, M Koss, E Treister, W Peter Maksym, WC Keel, C Megan Urry, CJ Lintott, O Ivy Wong

© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN.We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN (Lbol ~ 1042-1044 erg s-1). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN (Ebub ~ 1054-1055 erg). A possible scenario is that this bubble is inflated by the fading AGN, which after changing accretion state is now in a kinetic mode. Other possibilities are that the bubble has been inflated by the past luminous quasar (Lbol ~ 1046 erg s-1), or that the temperature gradient is an indication of a shock front from a superwind driven by the AGN. We discuss the possible scenarios and the implications for the AGN-host galaxy interaction, as well as an analogy between AGN and X-ray binaries lifecycles.We conclude that the AGN could inject mechanical energy into the host galaxy at the end of its lifecycle, and thus provide a source for mechanical feedback, in a similar way as observed for X-ray binaries.

Planet Hunters IX. KIC 8462852-where's the flux?


TS Boyajian, DM LaCourse, SA Rappaport, D Fabrycky, DA Fischer, D Gandolfi, GM Kennedy, H Korhonen, MC Liu, A Moor, K Olah, K Vida, MC Wyatt, WMJ Best, J Brewer, F Ciesla, B Csak, HJ Deeg, TJ Dupuy, G Handler, K Heng, SB Howell, ST Ishikawa, J Kovacs, T Kozakis, L Kriskovics, J Lehtinen, C Lintott, S Lynn, D Nespral, S Nikbakhsh, K Schawinski, JR Schmitt, AM Smith, G Szabo, R Szabo, J Viuho, J Wang, A Weiksnar, M Bosch, JL Connors, S Goodman, G Green, AJ Hoekstra, T Jebson, KJ Jek, MR Omohundro, HM Schwengeler, A Szewczyk

The Moon Zoo citizen science project: Preliminary results for the Apollo 17 landing site

ICARUS 271 (2016) 30-48

R Bugiolacchi, S Bamford, P Tar, N Thacker, IA Crawford, KH Joy, PM Grindrod, C Lintott

A generalized approach for producing, quantifying, and validating citizen science data from wildlife images.

Conservation biology : the journal of the Society for Conservation Biology 30 (2016) 520-531

A Swanson, M Kosmala, C Lintott, C Packer

Citizen science has the potential to expand the scope and scale of research in ecology and conservation, but many professional researchers remain skeptical of data produced by nonexperts. We devised an approach for producing accurate, reliable data from untrained, nonexpert volunteers. On the citizen science website, more than 28,000 volunteers classified 1.51 million images taken in a large-scale camera-trap survey in Serengeti National Park, Tanzania. Each image was circulated to, on average, 27 volunteers, and their classifications were aggregated using a simple plurality algorithm. We validated the aggregated answers against a data set of 3829 images verified by experts and calculated 3 certainty metrics-level of agreement among classifications (evenness), fraction of classifications supporting the aggregated answer (fraction support), and fraction of classifiers who reported "nothing here" for an image that was ultimately classified as containing an animal (fraction blank)-to measure confidence that an aggregated answer was correct. Overall, aggregated volunteer answers agreed with the expert-verified data on 98% of images, but accuracy differed by species commonness such that rare species had higher rates of false positives and false negatives. Easily calculated analysis of variance and post-hoc Tukey tests indicated that the certainty metrics were significant indicators of whether each image was correctly classified or classifiable. Thus, the certainty metrics can be used to identify images for expert review. Bootstrapping analyses further indicated that 90% of images were correctly classified with just 5 volunteers per image. Species classifications based on the plurality vote of multiple citizen scientists can provide a reliable foundation for large-scale monitoring of African wildlife.


Astronomical Journal 151 (2016)

JR Schmitt, A Tokovinin, J Wang, DA Fischer, MH Kristiansen, DM Lacourse, R Gagliano, AJV Tan, HM Schwengeler, MR Omohundro, A Venner, I Terentev, AR Schmitt, TL Jacobs, T Winarski, J Sejpka, KJ Jek, TS Boyajian, JM Brewer, ST Ishikawa, C Lintott, S Lynn, K Schawinski, ME Schwamb, A Weiksnar

© 2016. The American Astronomical Society. All rights reserved..We present high-resolution observations of a sample of 75 K2 targets from Campaigns 1-3 using speckle interferometry on the Southern Astrophysical Research (SOAR) telescope and adaptive optics imaging at the Keck II telescope. The median SOAR I-band and Keck Ks-band detection limits at were mag and mag, respectively. This sample includes 37 stars likely to host planets, 32 targets likely to be eclipsing binaries (EBs), and 6 other targets previously labeled as likely planetary false positives. We find nine likely physically bound companion stars within of three candidate transiting exoplanet host stars and six likely EBs. Six of the nine detected companions are new discoveries. One of these new discoveries, EPIC 206061524, is associated with a planet candidate. Among the EB candidates, companions were only found near the shortest period ones ( days), which is in line with previous results showing high multiplicity near short-period binary stars. This high-resolution data, including both the detected companions and the limits on potential unseen companions, will be useful in future planet vetting and stellar multiplicity rate studies for planets and binaries.

The milky way project and atlasgal: The distribution and physical properties of cold clumps near infrared bubbles

Astrophysical Journal 825 (2016)

S Kendrew, H Beuther, R Simpson, T Csengeri, M Wienen, CJ Lintott, MS Povich, C Beaumont, F Schuller

© 2016. The American Astronomical Society. All rights reserved.We present a statistical study of the distribution and physical properties of cold, dense material in and around the inner Galactic Plane near-infrared bubbles as cataloged by the Milky Way Project citizen scientists. Using data from the Atacama Pathfinder Experiment (APEX) Telescope Large Area Survey of the Galaxy 870 μm survey, we show that 48 ± 2% of all cold clumps in the studied survey region (|l| ≤ 65°, |b| ≤ 1°) are found in close proximity to a bubble, and 25 ± 2% appear directly projected toward a bubble rim. A two-point correlation analysis confirms the strong correlation of massive cold clumps with expanding bubbles. It shows an overdensity of clumps along bubble rims that grows with increasing bubble size, which shows how interstellar medium material is reordered on large scales by bubble expansion around regions of massive star formation. The highest column density clumps appear to be resistent to the expansion, remaining overdense toward the bubbles' interior rather than being swept up by the expanding edge. Spectroscopic observations in ammonia show that cold dust clumps near bubbles appear to be denser, hotter, and more turbulent than those in the field, offering circumstantial evidence that bubble-associated clumps are more likely to be forming stars. These observed differences in physical conditions persist beyond the region of the bubble rims.

Galaxy Zoo: Evidence for rapid, recent quenching within a population of AGN host galaxies

Monthly Notices of the Royal Astronomical Society 463 (2016) 2986-2996

RJ Smethurst, CJ Lintott, BD Simmons, K Schawinski, SP Bamford, CN Cardamone, SJ Kruk, KL Masters, CM Urry, KW Willett, OI Wong

© 2016, The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.We present a population study of the star formation history of 1244 Type 2 active galactic nuclei (AGN) host galaxies, compared to 6107 inactive galaxies. A Bayesian method is used to determine individual galaxy star formation histories, which are then collated to visualize the distribution for quenching and quenched galaxies within each population. We find evidence for some of the Type 2 AGN host galaxies having undergone a rapid drop in their star formation rate within the last 2 Gyr. AGN feedback is therefore important at least for this population of galaxies. This result is not seen for the quenching and quenched inactive galaxies whose star formation histories are dominated by the effects of downsizing at earlier epochs, a secondary effect for the AGN host galaxies. We show that histories of rapid quenching cannot account fully for the quenching of all the star formation in a galaxy's lifetime across the population of quenched AGN host galaxies, and that histories of slower quenching, attributed to secular (non-violent) evolution, are also key in their evolution. This is in agreement with recent results showing that both merger-driven and non-merger processes are contributing to the co-evolution of galaxies and supermassive black holes. The availability of gas in the reservoirs of a galaxy, and its ability to be replenished, appear to be the key drivers behind this co-evolution.

Galaxy zoo: Mergers - Dynamical models of interacting galaxies

Monthly Notices of the Royal Astronomical Society 459 (2016) 720-745

AJ Holincheck, JF Wallin, K Borne, L Fortson, C Lintott, AM Smith, S Bamford, WC Keel, M Parrish

© 2016 The Authors.The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of citizen scientists, we sample 105 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at Though our best-fitting model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from starburst models in interacting systems and suggest that tidally induced star formation is triggered very soon after closest approach.



J Wang, DA Fischer, T Barclay, A Picard, B Ma, BP Bowler, JR Schmitt, TS Boyajian, KJ Jek, D LaCourse, C Baranec, R Riddle, NM Law, C Lintott, K Schawinski, DJ Simister, B Gregoire, SP Babin, T Poile, TL Jacobs, T Jebson, MR Omohundro, HM Schwengeler, J Sejpka, IA Terentev, R Gagliano, J-P Paakkonen, HKO Berge, T Winarski, GR Green, AR Schmitt, MH Kristiansen, A Hoekstra

Ideas for Citizen Science in Astronomy


PJ Marshall, CJ Lintott, LN Fletcher

Galaxy Zoo: Are bars responsible for the feeding of active galactic nuclei at 0.2 < z < 1.0?


E Cheung, JR Trump, E Athanassoula, SP Bamford, EF Bell, A Bosma, CN Cardamone, KRV Casteels, SM Faber, JJ Fang, LF Fortson, DD Kocevski, DC Koo, S Laine, C Lintott, KL Masters, T Melvin, RC Nichol, K Schawinski, B Simmons, R Smethurst, KW Willett



WC Keel, WP Maksym, VN Bennert, CJ Lintott, SD Chojnowski, A Moiseev, A Smirnova, K Schawinski, CM Urry, DA Evans, A Pancoast, B Scott, C Showley, K Flatland



JR Schmitt, E Agol, KM Deck, LA Rogers, JZ Gazak, DA Fischer, J Wang, MJ Holman, KJ Jek, C Margossian, MR Omohundro, T Winarski, JM Brewer, MJ Giguere, C Lintott, S Lynn, M Parrish, K Schawinski, ME Schwamb, R Simpson, AM Smith

Galaxy Zoo: CANDELS barred discs and bar fractions


BD Simmons, T Melvin, C Lintott, KL Masters, KW Willett, WC Keel, RJ Smethurst, E Cheung, RC Nichol, K Schawinski, M Rutkowski, JS Kartaltepe, EF Bell, KRV Casteels, CJ Conselice, O Almaini, HC Ferguson, L Fortson, W Hartley, D Kocevski, AM Koekemoer, DH McIntosh, A Mortlock, JA Newman, J Ownsworth, S Bamford, T Dahlen, SM Faber, SL Finkelstein, A Fontana, A Galametz, NA Grogin, R Gruetzbauch, Y Guo, B Haeussler, KJ Jek, S Kaviraj, RA Lucas, M Peth, M Salvato, T Wiklind, S Wuyts

Crowd-sourced assessment of technical skills: A novel method to evaluate surgical performance

Journal of Surgical Research 187 (2014) 65-71

C Chen, L White, T Kowalewski, R Aggarwal, C Lintott, B Comstock, K Kuksenok, C Aragon, D Holst, T Lendvay

Background Validated methods of objective assessments of surgical skills are resource intensive. We sought to test a web-based grading tool using crowdsourcing called Crowd-Sourced Assessment of Technical Skill. Materials and methods Institutional Review Board approval was granted to test the accuracy of's Mechanical Turk and Facebook crowdworkers compared with experienced surgical faculty grading a recorded dry-laboratory robotic surgical suturing performance using three performance domains from a validated assessment tool. Assessor free-text comments describing their rating rationale were used to explore a relationship between the language used by the crowd and grading accuracy. Results Of a total possible global performance score of 3-15, 10 experienced surgeons graded the suturing video at a mean score of 12.11 (95% confidence interval [CI], 11.11-13.11). Mechanical Turk and Facebook graders rated the video at mean scores of 12.21 (95% CI, 11.98-12.43) and 12.06 (95% CI, 11.57-12.55), respectively. It took 24 h to obtain responses from 501 Mechanical Turk subjects, whereas it took 24 d for 10 faculty surgeons to complete the 3-min survey. Facebook subjects (110) responded within 25 d. Language analysis indicated that crowdworkers who used negation words (i.e., "but," "although," and so forth) scored the performance more equivalently to experienced surgeons than crowdworkers who did not (P < 0.00001). Conclusions For a robotic suturing performance, we have shown that surgery-naive crowdworkers can rapidly assess skill equivalent to experienced faculty surgeons using Crowd-Sourced Assessment of Technical Skill. It remains to be seen whether crowds can discriminate different levels of skill and can accurately assess human surgery performances. © 2014 Elsevier Inc. All rights reserved.

The ultraviolet attenuation law in backlit spiral galaxies Based in part on observations made with the NASA Galaxy Evolution Explorer. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034.

Astronomical Journal 147 (2014)

WC Keel, AM Manning, BW Holwerda, CJ Lintott, K Schawinski

The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly "gray" law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that widespread diffuse dust dominates over dust in star-forming regions deep into the UV. Comparison with published radiative-transfer models indicates that the role of dust clumping dominates over differences in grain populations at this coarse spatial resolution. © 2014. The American Astronomical Society. All rights reserved.

Measuring the conceptual understandings of citizen scientists participating in zooniverse projects: A first approach

Astronomy Education Review 12 (2013)

EE Prather, S Cormier, CS Wallace, C Lintott, M Jordan Raddick, A Smith

The Zooniverse projects turn everyday people into "citizen scientists" who work online with real data to assist scientists in conducting research on a variety of topics related to galaxies, exoplanets, lunar craters, and solar flares, among others. This paper describes our initial study to assess the conceptual knowledge and reasoning abilities of citizen scientists participating in two Zooniverse projects: Galaxy Zoo and Moon Zoo. In order to measure their knowledge and abilities, we developed two new assessment instruments, the Zooniverse Astronomical Concept Survey (ZACS) and the Lunar Cratering Concept Inventory (LCCI). We found that citizen scientists with the highest level of participation in the Galaxy Zoo and Moon Zoo projects also have the highest average correct scores on the items of the ZACS and LCCI. However, the limited nature of the data provided by Zooniverse participants prevents us from being able to evaluate the statistical significance of this finding, and we make no claim about whether there is a causal relationship between one's participation in Galaxy Zoo or Moon Zoo and one's level of conceptual understanding or reasoning ability on the astrophysical topics assessed by the ZACS or the LCCI. Overall, both the ZACS and the LCCI provide Zooniverse's citizen scientists with items that offer a wide range of difficulties. Using the data from the small subset of participants who responded to all items of the ZACS, we found evidence suggesting the ZACS is a reliable instrument (α=0.78), although twenty-one of its forty items appear to have point biserials less than 0.3. The work reported here provides significant insight into the strengths and limitations of various methods for administering assessments to citizen scientists. Researchers who wish to study the knowledge and abilities of citizen scientists in the future should be sure to design their research methods to avoid the pitfalls identified by our initial findings. © 2013 The American Astronomical Society.