Galaxy Zoo Supernovae

This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae. This proof of concept project uses members of the public to identify supernova candidates from the latest generation of wide-field imaging transient surveys. We describe the Galaxy Zoo Supernovae operations and scoring model, and demonstrate the effectiveness of this novel method using imaging data and transients from the Palomar Transient Factory (PTF). We examine the results collected over the period April-July 2010, during which nearly 14,000 supernova candidates from PTF were classified by more than 2,500 individuals within a few hours of data collection. We compare the transients selected by the citizen scientists to those identified by experienced PTF scanners, and find the agreement to be remarkable - Galaxy Zoo Supernovae performs comparably to the PTF scanners, and identified as transients 93% of the ~130 spectroscopically confirmed SNe that PTF located during the trial period (with no false positive identifications). Further analysis shows that only a small fraction of the lowest signal-to-noise SN detections (r > 19.5) are given low scores: Galaxy Zoo Supernovae correctly identifies all SNe with > 8{\sigma} detections in the PTF imaging data. The Galaxy Zoo Supernovae project has direct applicability to future transient searches such as the Large Synoptic Survey Telescope, by both rapidly identifying candidate transient events, and via the training and improvement of existing machine classifier algorithms.Comment: 13 pages, 10 figures, accepted MNRA

The visual complexity of coronal mass ejections follows the solar cycle

The Heliospheric Imagers on board National Aeronautics and Space Administration (NASA)'s twin STEREO spacecraft show that coronal mass ejections (CMEs) can be visually complex structures. To explore this complexity, we created a citizen science project with the U.K. Science Museum, in which participants were shown pairs of CME images and asked to decide which image in each pair appeared the most “complicated.” A Bradley‐Terry model was then applied to these data to rank the CMEs by their “complicatedness,” or “visual complexity.” This complexity ranking revealed that the annual average visual complexity values follow the solar activity cycle, with a higher level of complexity being observed at the peak of the cycle. The average complexity of CMEs observed by STEREO‐A was also found to be significantly higher than those observed by STEREO‐B. Visual complexity was found to be associated with CME size and brightness, but our results suggest that complexity may be influenced by the scale‐sizes of structure in the CMEs

Studying the first galaxies with ALMA

We discuss observations of the first galaxies, within cosmic reionization, at centimeter and millimeter wavelengths. We present a summary of current observations of the host galaxies of the most distant QSOs ($z \sim 6$). These observations reveal the gas, dust, and star formation in the host galaxies on kpc-scales. These data imply an enriched ISM in the QSO host galaxies within 1 Gyr of the big bang, and are consistent with models of coeval supermassive black hole and spheroidal galaxy formation in major mergers at high redshift. Current instruments are limited to studying truly pathologic objects at these redshifts, meaning hyper-luminous infrared galaxies ($L_{FIR} \sim 10^{13}$ L$_\odot$). ALMA will provide the one to two orders of magnitude improvement in millimeter astronomy required to study normal star forming galaxies (ie. Ly-$\alpha$ emitters) at $z \sim 6$. ALMA will reveal, at sub-kpc spatial resolution, the thermal gas and dust -- the fundamental fuel for star formation -- in galaxies into cosmic reionization.Comment: to appear in Science with ALMA: a new era for Astrophysics}, ed. R. Bachiller (Springer: Berlin); 5 pages, 7 figure

Selection of radio pulsar candidates using artificial neural networks

Radio pulsar surveys are producing many more pulsar candidates than can be inspected by human experts in a practical length of time. Here we present a technique to automatically identify credible pulsar candidates from pulsar surveys using an artificial neural network. The technique has been applied to candidates from a recent re-analysis of the Parkes multi-beam pulsar survey resulting in the discovery of a previously unidentified pulsar.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society. 9 pages, 7 figures, and 1 tabl

Massive elliptical galaxies : From cores to haloes

In the context of recent observational results that show massive ellipticals were in place at high redshifts, we reassess the status of monolithic collapse in a LCDM universe. Using a sample of over 2000 galaxies from the Sloan Digital Sky Survey, by comparing the dynamical mass and stellar mass (estimated from colours) we find that ellipticals have `cores' which are baryon-dominated within their half-light radius. These galaxies correspond to 3-sigma peaks in the spherical collapse model if the total mass in the halo is assumed to be 20 times the dynamical mass within the half-light radius. This value yields stellar mass to total mass ratios of 8%, compared to a cosmological baryon fraction of 18% derived from WMAP3 alone. We further develop a method for reconstructing the concentration halo parameter c of the progenitors of these galaxies by utilizing adiabatic contraction. Although the analysis is done within the framework of monolithic collapse, the resulting distribution of c is log-normal with a peak value of c~3-10 and a distribution width similar to the results of N-body simulations. We also derive scaling relations between stellar and dynamical mass and the velocity dispersion, and find that these are sufficient to recover the tilt of the fundamental plane.Comment: 9 pages, 9 figures. Updated to correspond to version accepted by Ap

Ecological impact assessments fail to reduce risk of bat casualties at wind farms

Demand for renewable energy is rising exponentially. While this has benefits in reducing greenhouse gas emissions, there may be costs to biodiversity [1]. Environmental Impact Assessments (EIAs) are the main tool used across the world to predict the overall positive and negative effects of renewable energy developments before planning consent is given, and the Ecological Impact Assessments (EcIAs) within them assess their species-specific effects. Given that EIAs are undertaken globally, are extremely expensive, and are enshrined in legislation, their place in evidence-based decision making deserves evaluation. Here we assess how well EIAs of wind-farm developments protect bats. We found they do not predict the risks to bats accurately, and even in those cases where high risk was correctly identified, the mitigation deployed did not avert the risk. Given that the primary purpose of an EIA is to make planning decisions evidence-based, our results indicate that EIA mitigation strategies used to date have been ineffective in protecting bats. In the future, greater emphasis should be placed on assessing the actual impacts post-construction and on developing effective mitigation strategies

Planet Hunters VII. Discovery of a New Low-Mass, Low-Density Planet (PH3 c) Orbiting Kepler-289 with Mass Measurements of Two Additional Planets (PH3 b and d)

We report the discovery of one newly confirmed planet ($P=66.06$ days, $R_{\rm{P}}=2.68\pm0.17R_\oplus$) and mass determinations of two previously validated Kepler planets, Kepler-289 b ($P=34.55$ days, $R_{\rm{P}}=2.15\pm0.10R_\oplus$) and Kepler-289-c ($P=125.85$ days, $R_{\rm{P}}=11.59\pm0.10R_\oplus$), through their transit timing variations (TTVs). We also exclude the possibility that these three planets reside in a $1:2:4$ Laplace resonance. The outer planet has very deep ($\sim1.3$), high signal-to-noise transits, which puts extremely tight constraints on its host star's stellar properties via Kepler's Third Law. The star PH3 is a young ($\sim1$ Gyr as determined by isochrones and gyrochronology), Sun-like star with $M_*=1.08\pm0.02M_\odot$, $R_*=1.00\pm0.02R_\odot$, and $T_{\rm{eff}}=5990\pm38$ K. The middle planet's large TTV amplitude ($\sim5$ hours) resulted either in non-detections or inaccurate detections in previous searches. A strong chopping signal, a shorter period sinusoid in the TTVs, allows us to break the mass-eccentricity degeneracy and uniquely determine the masses of the inner, middle, and outer planets to be $M=7.3\pm6.8M_\oplus$, $4.0\pm0.9M_\oplus$, and $M=132\pm17M_\oplus$, which we designate PH3 b, c, and d, respectively. Furthermore, the middle planet, PH3 c, has a relatively low density, $\rho=1.2\pm0.3$ g/cm$^3$ for a planet of its mass, requiring a substantial H/He atmosphere of $2.1^{+0.8}_{-0.3}$ by mass, and joins a growing population of low-mass, low-density planets.Comment: 21 pages, 10 figures, 5 tables, accepted into Ap

Supermassive black holes in merger-free galaxies have higher spins which are preferentially aligned with their host galaxy

Here we use the Horizon-AGN simulation to test whether the spins of SMBHs in merger-free galaxies are higher. We select samples using an observationally motivated bulge-to-total mass ratio of < 0.1, along with two simulation motivated thresholds selecting galaxies which have not undergone a galaxy merger since z = 2, and those SMBHs with < 10% of their mass due to SMBH mergers. We find higher spins (> 5{\sigma} ) in all three samples compared to the rest of the population. In addition, we find that SMBHs with their growth dominated by BH mergers following galaxy mergers, are less likely to be aligned with their galaxy spin than those that have grown through accretion in the absence of galaxy mergers (3.4{\sigma} ). We discuss the implications this has for the impact of active galactic nuclei (AGN) feedback, finding that merger-free SMBHs spend on average 91% of their lifetimes since z = 2 in a radio mode of feedback (88% for merger-dominated galaxies). Given that previous observational and theoretical works have concluded that merger-free processes dominate SMBH-galaxy co-evolution, our results suggest that this co-evolution could be regulated by radio mode AGN feedback.Comment: RSB and RJS are joint first authors. Submitted to MNRAS, 10 page

Evidence for non-merger co-evolution of galaxies and their supermassive black holes

Recent observational and theoretical studies have suggested that supermassive black holes (SMBHs) grow mostly through non-merger (`secular') processes. Since galaxy mergers lead to dynamical bulge growth, the only way to observationally isolate non-merger growth is to study galaxies with low bulge-to-total mass ratio (e.g. B/T < 10%). However, bulge growth can also occur due to secular processes, such as disk instabilities, making disk-dominated selections a somewhat incomplete way to select merger-free systems. Here we use the Horizon-AGN simulation to select simulated galaxies which have not undergone a merger since z = 2, regardless of bulge mass, and investigate their location on typical black hole-galaxy scaling relations in comparison to galaxies with merger dominated histories. While the existence of these correlations has long been interpreted as co-evolution of galaxies and their SMBHs driven by galaxy mergers, we show here that they persist even in the absence of mergers. We find that the correlations between SMBH mass and both total mass and stellar velocity dispersion are independent of B/T ratio for both merger-free and merger-dominated galaxies. In addition, the bulge mass and SMBH mass correlation is still apparent for merger-free galaxies, the intercept for which is dependent on B/T. Galaxy mergers reduce the scatter around the scaling relations, with merger-free systems showing broader scatter. We show that for merger-free galaxies, the co-evolution is dominated by radio-mode feedback, and suggest that the long periods of time between galaxy mergers make an important contribution to the co-evolution between galaxies and SMBHs in all galaxies.Comment: RJS and RSB are joint first authors. 12 pages, 7 figures, submitted to MNRA