31247434
Planet Hunters: the first two planet candidates identified by the public using the Kepler public archive data
Planet Hunters is a new citizen science project designed to engage the public in an exoplanet search using NASA Kepler public release data. In the first month after launch, users identified two new planet candidates which survived our checks for false positives. The follow-up effort included analysis of Keck HIRES spectra of the host stars, analysis of pixel centroid offsets in the Kepler data and adaptive optics imaging at Keck using NIRC2. Spectral synthesis modelling coupled with stellar evolutionary models yields a stellar density distribution, which is used to model the transit orbit. The orbital periods of the planet candidates are 9.8844 ± 0.0087 d (KIC 10905746) and 49.7696 ± 0.000 39 d (KIC 6185331), and the modelled planet radii are 2.65 and 8.05 R_⊕. The involvement of citizen scientists as part of Planet Hunters is therefore shown to be a valuable and reliable tool in exoplanet detection.
39846719
Galaxy Zoo: Bar Lengths in Nearby Disk Galaxies
We present an analysis of bar length measurements of 3150 local galaxies in a volume limited sample of low redshift (z =3), and we find that observers were able to reproduce their own bar lengths to 3% and each others' to better than 20%. We find a "color bimodality" in our disk galaxy population with bar length, i.e., longer bars inhabit redder disk galaxies and the bars themselves are redder, and that the bluest galaxies host the smallest galactic bars (< 5 kpc/h). We also find that bar and disk colors are clearly correlated, and for galaxies with small bars, the disk is, on average, redder than the bar colors, while for longer bars the bar then itself is redder, on average, than the disk. We further find that galaxies with a prominent bulge are more likely to host longer bars than those without bulges. We categorise our galaxy populations by how the bar and/or ring are connected to the spiral arms. We find that galaxies whose bars are directly connected to the spiral arms are preferentially bluer and that these galaxies host typically shorter bars. Within the scatter, we find that stronger bars are found in galaxies which host a ring (and only a ring). The bar length and width measurements used herein are made publicly available for others to use (this http URL).
3689707
Galaxy Zoo: dust and molecular gas in early-type galaxies with prominent dust lanes
We explore the properties of dust and associated molecular gas in 352 nearby (0.01 < z < 0.07) early-type galaxies (ETGs) with prominent dust lanes, drawn from the Sloan Digital Sky Survey (SDSS). Two-thirds of these ‘dusty ETGs’ (D-ETGs) are morphologically disturbed, which suggests a merger origin, making these galaxies ideal test beds for studying the merger process at low redshift. The D-ETGs preferentially reside in lower density environments, compared to a control sample drawn from the general ETG population. Around 80 per cent of D-ETGs inhabit the field (compared to 60 per cent of the control ETGs) and less than 2 per cent inhabit clusters (compared to 10 per cent of the control ETGs). Compared to their control-sample counterparts, D-ETGs exhibit bluer ultraviolet–optical colours (indicating enhanced levels of star formation) and an active galactic nucleus fraction that is more than an order of magnitude greater (indicating a strikingly higher incidence of nuclear activity). The mass of clumpy dust residing in large-scale dust features is estimated, using the SDSS r-band images, to be in the range 104.5–106.5 M⊙. A comparison to the total (clumpy + diffuse) dust masses – calculated using the far-infrared fluxes of 15 per cent of the D-ETGs that are detected by the Infrared Astronomical Satellite (IRAS) – indicates that only 20 per cent of the dust is typically contained in these large-scale dust features. The dust masses are several times larger than the maximum value expected from stellar mass loss, ruling out an internal origin. The dust content shows no correlation with the blue luminosity, indicating that it is not related to a galactic scale cooling flow. Furthermore, no correlation is found with the age of the recent starburst, suggesting that the dust is accreted directly in the merger rather than being produced in situ by the triggered star formation. Using molecular gas-to-dust ratios of ETGs in the literature, we estimate that the median current molecular gas fraction in the IRAS-detected ETGs is ∼1.3 per cent. Adopting reasonable values for gas depletion time-scales and starburst ages, the median initial gas fraction in these D-ETGs is ∼4 per cent. Recent work has suggested that the merger activity in nearby ETGs largely involves minor mergers (dry ETG + gas-rich dwarf), with mass ratios between 1:10 and 1:4. If the IRAS-detected D-ETGs have formed via this channel, then the original gas fractions of the accreted satellites are between 20 and 44 per cent.
18148287
Dynamic Bayesian Combination of Multiple Imperfect Classifiers
Classifier combination methods need to make best use of the outputs of multiple, imperfect classifiers to enable higher accuracy classifications. In many situations, such as when human decisions need to be combined, the base decisions can vary enormously in reliability. A Bayesian approach to such uncertain combination allows us to infer the differences in performance between individuals and to incorporate any available prior knowledge about their abilities when training data is sparse. In this chapter we explore Bayesian classifier combination, using the computationally efficient framework of variational Bayesian inference. We apply the approach to real data from a large citizen science project, Galaxy Zoo Supernovae, and show that our method far outperforms other established approaches to imperfect decision combination.We go on to analyse the putative community structure of the decision makers, based on their inferred decision making strategies, and show that natural groupings are formed. Finally we present a dynamic Bayesian classifier combination approach and investigate the changes in base classifier performance over time.
18104149
Galaxy Zoo 2: detailed morphological classifications for 304 122 galaxies from the Sloan Digital Sky Survey
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 (SDSS). 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 mr > 17, in addition to deeper images from SDSS Stripe 82. While the original GZ2 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 per cent) 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.
3675875
Galaxy Zoo: Quantifying Morphological Indicators of Galaxy Interaction
We use Galaxy Zoo 2 visual classifications to study the morphological signatures of interaction between similar-mass galaxy pairs in the Sloan Digital Sky Survey. We find that many observable features correlate with projected pair separation – not only obvious indicators of merging, disturbance and tidal tails, but also more regular features, such as spiral arms and bars. These trends are robustly quantified, using a control sample to account for observational biases, producing measurements of the strength and separation scale of various morphological responses to pair interaction. For example, we find that the presence of spiral features is enhanced at scales ≲ 70 h− 170 kpc, probably due to both increased star formation and the formation of tidal tails. On the other hand, the likelihood of identifying a bar decreases significantly in pairs with separations ≲ 30 h− 170 kpc, suggesting that bars are suppressed by close interactions between galaxies of similar mass. We go on to show how morphological indicators of physical interactions provide a way of significantly refining standard estimates for the frequency of close pair interactions, based on velocity offset and projected separation. The presence of loosely wound spiral arms is found to be a particularly reliable signal of an interaction, for projected pair separations up to ∼100 h− 170 kpc. We use this indicator to demonstrate our method, constraining the fraction of low-redshift galaxies in truly interacting pairs, with M* > 109.5 M⊙ and mass ratio <4, to be between 0.4 and 2.7 per cent.
121223746
Correlations between large transverse momentum π0 mesons and charged particles at the CERN ISR
Abstract A study of the charged particles emitted together with a large transverse momentum π O was made at the CERN ISR at a centre-of-mass energy s = 52.7 GeV . The π O mesons and the charged particles were observed in two detectors, each centred at θ cm = 90° and each covering a laboratory solid angle of 0.59 sr for π o 's and 1.1 sr for charged particles. The multiplicity of charged particles, observed in the same and in the opposite hemisphere as the π O , was found to be larger than the average multiplicity for inelastic interactions. Some rapidity and azimuthal correlations were observed.
26283113
Infrared Eclipses of the Strongly Irradiated Planet Wasp-33b, and Oscillations of Its Host Star
We observe two secondary eclipses of the strongly irradiated transiting planet WASP-33b, in the K_s band at 2.15 μm, and one secondary eclipse each at 3.6 μm and 4.5 μm using Warm Spitzer. This planet orbits an A5V δ-Scuti star that is known to exhibit low-amplitude non-radial p-mode oscillations at about 0.1% semi-amplitude. We detect stellar oscillations in all of our infrared eclipse data, and also in one night of observations at J band (1.25 μm) out of eclipse. The oscillation amplitude, in all infrared bands except K_s , is about the same as in the optical. However, the stellar oscillations in K_s band (2.15 μm) have about twice the amplitude (0.2%) as seen in the optical, possibly because the Brackett-γ line falls in this bandpass. As regards the exoplanetary eclipse, we use our best-fit values for the eclipse depth, as well as the 0.9 μm eclipse observed by Smith et al., to explore possible states of the exoplanetary atmosphere, based on the method of Madhusudhan & Seager. On this basis we find two possible states for the atmospheric structure of WASP-33b. One possibility is a non-inverted temperature structure in spite of the strong irradiance, but this model requires an enhanced carbon abundance (C/O > 1). The alternative model has solar composition, but an inverted temperature structure. Spectroscopy of the planet at secondary eclipse, using a spectral resolution that can resolve the water vapor band structure, should be able to break the degeneracy between these very different possible states of the exoplanetary atmosphere. However, both of those model atmospheres absorb nearly all of the stellar irradiance with minimal longitudinal re-distribution of energy, strengthening the hypothesis of Cowan & Agol that the most strongly irradiated planets circulate energy poorly. Our measurement of the central phase of the eclipse yields e cos ω = 0.0003 ± 0.00013, which we regard as being consistent with a circular orbit.
120919376
The Durham air shower array - III: Evaluation of the array's response to showers
Abstract A Monte Carlo investigation of the Durham air shower array is described in which the systematic biases introduced into air shower data recorded by the experiment are evaluated.
120200157
Unusual production features of isoscalar mesons in proton diffractive dissociation at the CERN-ISR
Abstract D(1285) and E/iota(1422) are observed in the diffractive dissociation process, pp→(pK 0 K +- π ± )p, with √ s =63Gev. The D(1285) is produced with dominant ±1 helicity. Several unusual features of the data suggest that the mesonic states result from gluonic interactions in the collision.
123901120
A Study of Inclusive Spectra and Two Particle Correlations at Large Transverse Momentum
Abstract The inclusive production of π and η mesons at 90° from proton-proton collisions has been measured at the CERN ISR at centre-of-mass energies between 23.5 and 62.4 GeV. The momentum correlation of charged particles emitted together with a large transverse momentum pion has also been studied, using two magnetic spectrometers each centred at 90°.