# Publications by Chris Lintott

## The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

ArXiv (2014)

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

(Abridged) The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet 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 GALEX, XMM Optical Monitor, and HST data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with candidates provided by Galaxy Zoo participants. 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 close to the Calzetti et al. (1994) form; the UV slope for the overall sample is substantially shallower than found by Wild et al. (2011), 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 accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. This "grey" law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. The extrapolation needed to compare attenution between backlit galaxies at moderate redshifts, and local systems from SDSS data, is mild enough to allow use of galaxy overlaps to trace the cosmic history of dust. For NGC 2207, the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the ultraviolet, which opens the possibility that widespread diffuse dust dominates over dust in star-forming regions deep into the ultraviolet. Comparison with published radiative-transfer models indicates that the role of dust clumping dominates over differences in grain populations, at this spatial resolution.

## Galaxy Zoo: An independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS

ArXiv (2014)

T Melvin, K Masters, C Lintott, RC Nichol, B Simmons, SP Bamford, KRV Casteels, E Cheung, EM Edmondson, L Fortson, K Schawinski, RA Skibba, AM Smith, KW Willett

We measure the redshift evolution of the bar fraction in a sample of 2380 visually selected disc galaxies found in Cosmic Evolution Survey (COSMOS) Hubble Space Telescope (HST) images. The visual classifications used to identify both the disc sample and to indicate the presence of stellar bars were provided by citizen scientists via the Galaxy Zoo: Hubble (GZH) project. We find that the overall bar fraction decreases by a factor of two, from 22+/-5% at z=0.4 (tlb = 4.2 Gyr) to 11+/-2% at z=1.0 (tlb = 7.8 Gyr), consistent with previous analysis. We show that this decrease, of the strong bar fraction in a volume limited sample of massive disc galaxies [stellar mass limit of log(Mstar/Msun) > 10.0], cannot be due to redshift dependent biases hiding either bars or disc galaxies at higher redshifts. Splitting our sample into three bins of mass we find that the decrease in bar fraction is most prominent in the highest mass bin, while the lower mass discs in our sample show a more modest evolution. We also include a sample of 98 red disc galaxies. These galaxies have a high bar fraction (45+/-5%), and are missing from other COSMOS samples which used SED fitting or colours to identify high redshift discs. Our results are consistent with a picture in which the evolution of massive disc galaxies begins to be affected by slow (secular) internal process at z~1. We discuss possible connections of the decrease in bar fraction to the redshift, including the growth of stable disc galaxies, mass evolution of the gas content in disc galaxies, as well as the mass dependent effects of tidal interactions.

## Crowd-Sourced Assessment of Technical Skills: a novel method to evaluate surgical performance

Journal of Surgical Research (2013)

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

## Planet Hunters. V. A Confirmed Jupiter-Size Planet in the Habitable Zone and 42 Planet Candidates from the Kepler Archive Data

ArXiv (2013)

J Wang, DA Fischer, T Barclay, TS Boyajian, JR Crepp, ME Schwamb, C Lintott, KJ Jek, AM Smith, M Parrish, K Schawinski, J Schmitt, MJ Giguere, JM Brewer, S Lynn, R Simpson, AJ Hoekstra, TL Jacobs, D LaCourse, HM Schwengeler, M Chopin

We report the latest Planet Hunter results, including PH2 b, a Jupiter-size (R_PL = 10.12 \pm 0.56 R_E) planet orbiting in the habitable zone of a solar-type star. PH2 b was elevated from candidate status when a series of false positive tests yielded a 99.9% confidence level that transit events detected around the star KIC 12735740 had a planetary origin. Planet Hunter volunteers have also discovered 42 new planet candidates in the Kepler public archive data, of which 33 have at least three transits recorded. Most of these transit candidates have orbital periods longer than 100 days and 20 are potentially located in the habitable zones of their host stars. Nine candidates were detected with only two transit events and the prospective periods are longer than 400 days. The photometric models suggest that these objects have radii that range between Neptune to Jupiter. These detections nearly double the number of gas giant planet candidates orbiting at habitable zone distances. We conducted spectroscopic observations for nine of the brighter targets to improve the stellar parameters and we obtained adaptive optics imaging for four of the stars to search for blended background or foreground stars that could confuse our photometric modeling. We present an iterative analysis method to derive the stellar and planet properties and uncertainties by combining the available spectroscopic parameters, stellar evolution models, and transiting light curve parameters, weighted by the measurement errors. Planet Hunters is a citizen science project that crowd-sources the assessment of NASA Kepler light curves. The discovery of these 43 planet candidates demonstrates the success of citizen scientists at identifying planet candidates, even in longer period orbits with only two or three transit events.

## Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky Survey

ArXiv (2013)

KW Willett, CJ Lintott, SP Bamford, KL Masters, BD Simmons, KRV Casteels, EM Edmondson, LF Fortson, S Kaviraj, WC Keel, T Melvin, RC Nichol, MJ Raddick, K Schawinski, RJ Simpson, RA Skibba, AM Smith, D Thomas

We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304,122 galaxies drawn from the Sloan Digital Sky Survey. Morphology is a powerful probe for quantifying a galaxy's dynamical history; however, automatic classifications of morphology (either by computer analysis of images or by using other physical parameters as proxies) still have drawbacks when compared to visual inspection. The large number of images available in current surveys makes visual inspection of each galaxy impractical for individual astronomers. GZ2 uses classifications from volunteer citizen scientists to measure morphologies for all galaxies in the DR7 Legacy survey with m_r>17, in addition to deeper images from SDSS Stripe 82. While the original Galaxy Zoo project identified galaxies as early-types, late-types, or mergers, GZ2 measures finer morphological features. These include bars, bulges, and the shapes of edge-on disks, as well as quantifying the relative strengths of galactic bulges and spiral arms. This paper presents the full public data release for the project, including measures of accuracy and bias. The majority (>90%) of GZ2 classifications agree with those made by professional astronomers, especially for morphological T-types, strong bars, and arm curvature. Both the raw and reduced data products can be obtained in electronic format at http://data.galaxyzoo.org .

## 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.

## A Herschel-ATLAS study of dusty spheroids: probing the minor-merger process in the local Universe

ArXiv (2013)

S Kaviraj, K Rowlands, M Alpaslan, L Dunne, YS Ting, M Bureau, S Shabala, CJ Lintott, DJB Smith, THATLAS collaboration

We use multi-wavelength (0.12 - 500 micron) photometry from Herschel-ATLAS, WISE, UKIDSS, SDSS and GALEX, to study 23 nearby spheroidal galaxies with prominent dust lanes (DLSGs). DLSGs are considered to be remnants of recent minor mergers, making them ideal laboratories for studying both the interstellar medium (ISM) of spheroids and minor-merger-driven star formation in the nearby Universe. The DLSGs exhibit star formation rates (SFRs) between 0.01 and 10 MSun yr^-1, with a median of 0.26 MSun yr^-1 (a factor of 3.5 greater than the average SG). The median dust mass, dust-to-stellar mass ratio and dust temperature in these galaxies are around 10^7.6 MSun yr^-1, ~0.05% and ~19.5 K respectively. The dust masses are at least a factor of 50 greater than that expected from stellar mass loss and, like the SFRs, show no correlation with galaxy luminosity, suggesting that both the ISM and the star formation have external drivers. Adopting literature gas-to-dust ratios and star formation histories derived from fits to the panchromatic photometry, we estimate that the median current and initial gas-to-stellar mass ratios in these systems are ~4% and ~7% respectively. If, as indicated by recent work, minor mergers that drive star formation in spheroids with (NUV-r)>3.8 (the colour range of our DLSGs) have stellar mass ratios between 1:6 and 1:10, then the satellite gas fractions are likely >50%.

## Erratum: Planet hunters. V. A confirmed jupiter-size planet in the habitable zone and 42 planet candidates from the kepler archive data (ApJ (2013) 776 (10))

Astrophysical Journal 778 (2013)

J Wang, DA Fischer, TS Boyajian, JR Schmitt, MJ Giguere, JM Brewer, T Barclay, JR Crepp, ME Schwamb, C Lintott, R Simpson, AM Smith, M Parrish, S Lynn, AJ Hoekstra, K Schawinski, KJ Jek, TL Jacobs, D Lacourse, HM Schwengeler, M Chopin, R Herszkowicz

## Galaxy Zoo: Observing Secular Evolution Through Bars

ArXiv (2013)

E Cheung, L Athanassoula, KL Masters, RC Nichol, A Bosma, EF Bell, SM Faber, DC Koo, C Lintott, T Melvin, K Schawinski, RA Skibba, KW Willett

Observations have shown that there is a connection between the presence of a bar and the properties of a galaxy. In a parallel effort, simulations have shown that this connection is consistent with the theory of bar-driven secular evolution. But observational evidence of bar-driven secular evolution has been sparse. In this paper, we use the Galaxy Zoo 2 dataset to look for evidence of this secular evolution. Our sample consists of 13,295 disk galaxies, with an overall bar fraction of 23.6 +/- 0.4%, of which 1,154 barred galaxies also have bar length measurements. These samples are the largest ever used to study the role of bars in disk galaxy evolution. We characterize bars by the bar likelihood, the likelihood a bar is present in a given galaxy, and the bar length. These two bar properties show interesting correlations with the specific star formation rate and the inner central structure of galaxies. Comparing these observations to state-of-the-art simulations of bar evolution, which include live halos and the effects of gas and star formation, reveals that these trends are consistent with the predicted effects of gas content and bulges on bar formation and evolution. These results represent empirical evidence for secular evolution driven by bars in disk galaxies. This work suggests that bars are not stagnant structures within disk galaxies, but are a critical evolutionary driver of their host galaxies in the local universe (z < 1).

## Galaxy Zoo: Motivations of Citizen Scientists

ArXiv (2013)

MJ Raddick, G Bracey, PL Gay, CJ Lintott, C Cardamone, P Murray, K Schawinski, AS Szalay, J Vandenberg

Citizen science, in which volunteers work with professional scientists to conduct research, is expanding due to large online datasets. To plan projects, it is important to understand volunteers' motivations for participating. This paper analyzes results from an online survey of nearly 11,000 volunteers in Galaxy Zoo, an astronomy citizen science project. Results show that volunteers' primary motivation is a desire to contribute to scientific research. We encourage other citizen science projects to study the motivations of their volunteers, to see whether and how these results may be generalized to inform the field of citizen science.

## Sir Patrick Moore, 'The Sky at Night' and modern astronomy in the UK

ASTRONOMY & GEOPHYSICS 54 (2013) 37-38

P Abel, C Lintott, M Barstow

## Morphology in the Era of Large Surveys

ArXiv (2013)

C Lintott, K Masters, B Simmons, S Bamford, S Kaviraj

The study of galaxies has changed dramatically over the past few decades with the advent of large-scale astronomical surveys. These large collaborative efforts have made available high-quality imaging and spectroscopy of hundreds of thousands of systems, providing a body of observations which has significantly enhanced our understanding not only of cosmology and large-scale structure in the universe but also of the astrophysics of galaxy formation and evolution. Throughout these changes, one thing that has remained constant is the role of galaxy morphology as a clue to understanding galaxies. But obtaining morphologies for large numbers of galaxies is challenging; this topic, "Morphology in the era of large surveys", was the subject of a recent discussion meeting at the Royal Astronomical Society, and this "Astronomy and Geophysics" article is a report on that meeting.

## Planet Hunters VI: The First Kepler Seven Planet Candidate System and 13 Other Planet Candidates from the Kepler Archival Data

ArXiv (2013)

JR Schmitt, J Wang, DA Fischer, KJ Jek, JC Moriarty, TS Boyajian, ME Schwamb, C Lintott, AM Smith, M Parrish, K Schawinski, S Lynn, R Simpson, M Omohundro, T Winarski, SJ Goodman, T Jebson, D Lacourse

We report the discovery of 14 new transiting planet candidates in the Kepler field from the Planet Hunters citizen science program. None of these candidates overlap with Kepler Objects of Interest (KOIs), and five of the candidates were missed by the Kepler Transit Planet Search (TPS) algorithm. The new candidates have periods ranging from 124-904 days, eight residing in their host star's habitable zone (HZ) and two (now) in multiple planet systems. We report the discovery of one more addition to the six planet candidate system around KOI-351, marking the first seven planet candidate system from Kepler. Additionally, KOI-351 bears some resemblance to our own solar system, with the inner five planets ranging from Earth to mini-Neptune radii and the outer planets being gas giants; however, this system is very compact, with all seven planet candidates orbiting $\lesssim 1$ AU from their host star. We perform a numerical integration of the orbits and show that the system remains stable for over 100 million years. A Hill stability test also confirms the feasibility for the dynamical stability of the KOI-351 system.

## Morphology in the era of large surveys

ASTRONOMY & GEOPHYSICS 54 (2013) 16-19

C Lintott, K Masters, B Simmons, S Bamford, S Kaviraj

## Galaxy Zoo: Bulgeless Galaxies With Growing Black Holes

ArXiv (2012)

BD Simmons, C Lintott, K Schawinski, EC Moran, A Han, S Kaviraj, KL Masters, CM Urry, KW Willett, SP Bamford, RC Nichol

The growth of supermassive black holes appears to be driven by galaxy mergers, violent merger-free processes and/or `secular' processes. In order to quantify the effects of secular evolution on black hole growth, we study a sample of active galactic nuclei (AGN) in galaxies with a calm formation history free of significant mergers, a population that heretofore has been difficult to locate. Here we present an initial sample of 13 AGN in massive (M_* >~ 1e10 M_sun) bulgeless galaxies -- which lack the classical bulges believed inevitably to result from mergers -- selected from the Sloan Digital Sky Survey using visual classifications from Galaxy Zoo. Parametric morphological fitting confirms the host galaxies lack classical bulges; any contributions from pseudobulges are very small (typically < 5%). We compute black hole masses for the two broad-line objects in the sample (4.2e6 and 1.2e7 M_sun) and place lower limits on black hole masses for the remaining sample (typically M_BH >~ 1e6 M_sun), showing that significant black hole growth must be possible in the absence of mergers or violent disk instabilities. The black hole masses are systematically higher than expected from established bulge-black hole relations. However, if the mean Eddington ratio of the systems with measured black hole masses (L/L_Edd = 0.065) is typical, 10 of 13 sources are consistent with the correlation between black hole mass and total stellar mass. That pure disk galaxies and their central black holes may be consistent with a relation derived from elliptical and bulge-dominated galaxies with very different formation histories implies the details of stellar galaxy evolution and dynamics may not be fundamental to the co-evolution of galaxies and black holes.

## Observational Tracking of the 2D Structure of Coronal Mass Ejections Between the Sun and 1 AU

Solar Physics (2012) 1-19

NP Savani, JA Davies, CJ Davis, D Shiota, AP Rouillard, MJ Owens, K Kusano, V Bothmer, SP Bamford, CJ Lintott, A Smith

## Galaxy Zoo: Building the low-mass end of the red sequence with local post-starburst galaxies

Monthly Notices of the Royal Astronomical Society 420 (2012) 1684-1692

OI Wong, K Schawinski, S Kaviraj, C Lintott, D Darg, KL Masters, RC Nichol, D Thomas, WC Keel, SP Bamford, D Andreescu, P Murray, MJ Raddick, A Szalay, J Vandenberg

We present a study of local post-starburst galaxies (PSGs) using the photometric and spectroscopic observations from the Sloan Digital Sky Survey and the results from the Galaxy Zoo project. We find that the majority of our local PSG population have neither early- nor late-type morphologies but occupy a well-defined space within the colour-stellar mass diagram, most notably, the low-mass end of the 'green valley' below the transition mass thought to be the mass division between low-mass star-forming galaxies and high-mass passively evolving bulge-dominated galaxies. Our analysis suggests that it is likely that local PSGs will quickly transform into 'red', low-mass early-type galaxies as the stellar morphologies of the 'green' PSGs largely resemble that of the early-type galaxies within the same mass range. We propose that the current population of PSGs represents a population of galaxies which is rapidly transitioning between the star-forming and the passively evolving phases. Subsequently, these PSGs will contribute towards the build-up of the low-mass end of the 'red sequence' once the current population of young stars fade and stars are no longer being formed. These results are consistent with the idea of 'downsizing' where the build-up of smaller galaxies occurs at later epochs. © 2012 CSIRO Monthly Notices of the Royal Astronomical Society © 2012 RAS.

## Citizen Science: Contributions to Astronomy Research

ArXiv (2012)

C Christian, C Lintott, A Smith, L Fortson, S Bamford

The contributions of everyday individuals to significant research has grown dramatically beyond the early days of classical birdwatching and endeavors of amateurs of the 19th century. Now people who are casually interested in science can participate directly in research covering diverse scientific fields. Regarding astronomy, volunteers, either as individuals or as networks of people, are involved in a variety of types of studies. Citizen Science is intuitive, engaging, yet necessarily robust in its adoption of sci-entific principles and methods. Herein, we discuss Citizen Science, focusing on fully participatory projects such as Zooniverse (by several of the au-thors CL, AS, LF, SB), with mention of other programs. In particular, we make the case that citizen science (CS) can be an important aspect of the scientific data analysis pipelines provided to scientists by observatories.

## The Galaxy Zoo survey for giant AGN-ionized clouds: Past and present black hole accretion events

Monthly Notices of the Royal Astronomical Society 420 (2012) 878-900

WC Keel, SD Chojnowski, VN Bennert, A Pancoast, C Harris, AM Nierenberg, A Sonnenfeld, K Schawinski, CJ Lintott, S Lynn, R Proctor