The development of the size–weight illusion in children coincides with the development of nonverbal cognition rather than motor skills

This is the final version. Available on open access from Elsevier via the DOI in this recordWe examined how the strength of the size–weight illusion develops with age in typically developing children. To this end, we recruited children aged 5–12 years and quantified the degree to which they experienced the illusion. We hypothesized that the strength of the illusion would increase with age. The results supported this hypothesis. We also measured abilities in manual dexterity, receptive language, and abstract reasoning to determine whether changes in illusion strength were associated with these factors. Manual dexterity and receptive language did not correlate with illusion strength. Conversely, illusion strength and abstract reasoning were tightly coupled with each other. Multiple regression further revealed that age, manual dexterity, and receptive language did not contribute more to the variance in illusion strength beyond children's abilities in abstract reasoning. Taken together, the effects of age on the size–weight illusion appear to be explained by the development of nonverbal cognition. These findings not only inform the literature on child development but also have implications for theoretical explanations on the size–weight illusion. We suggest that the illusion has a strong acquired component to it and that it is strengthened by children's reasoning skills and perhaps an understanding of the world that develops with age.Australian Research Counci

Stereotyping starlings are more 'pessimistic'.

Negative affect in humans and animals is known to cause individuals to interpret ambiguous stimuli pessimistically, a phenomenon termed 'cognitive bias'. Here, we used captive European starlings (Sturnus vulgaris) to test the hypothesis that a reduction in environmental conditions, from enriched to non-enriched cages, would engender negative affect, and hence 'pessimistic' biases. We also explored whether individual differences in stereotypic behaviour (repetitive somersaulting) predicted 'pessimism'. Eight birds were trained on a novel conditional discrimination task with differential rewards, in which background shade (light or dark) determined which of two covered dishes contained a food reward. The reward was small when the background was light, but large when the background was dark. We then presented background shades intermediate between those trained to assess the birds' bias to choose the dish associated with the smaller food reward (a 'pessimistic' judgement) when the discriminative stimulus was ambiguous. Contrary to predictions, changes in the level of cage enrichment had no effect on 'pessimism'. However, changes in the latency to choose and probability of expressing a choice suggested that birds learnt rapidly that trials with ambiguous stimuli were unreinforced. Individual differences in performance of stereotypies did predict 'pessimism'. Specifically, birds that somersaulted were more likely to choose the dish associated with the smaller food reward in the presence of the most ambiguous discriminative stimulus. We propose that somersaulting is part of a wider suite of behavioural traits indicative of a stress response to captive conditions that is symptomatic of a negative affective state

Spatial Resolution of Double-Sided Silicon Microstrip Detectors for the PAMELA Apparatus

The PAMELA apparatus has been assembled and it is ready to be launched in a satellite mission to study mainly the antiparticle component of cosmic rays. In this paper the performances obtained for the silicon microstrip detectors used in the magnetic spectrometer are presented. This subdetector reconstructs the curvature of a charged particle in the magnetic field produced by a permanent magnet and consequently determines momentum and charge sign, thanks to a very good accuracy in the position measurements (better than 3 um in the bending coordinate). A complete simulation of the silicon microstrip detectors has been developed in order to investigate in great detail the sensor's characteristics. Simulated events have been then compared with data gathered from minimum ionizing particle (MIP) beams during the last years in order to tune free parameters of the simulation. Finally some either widely used or original position finding algorithms, designed for such kind of detectors, have been applied to events with different incidence angles. As a result of the analysis, a method of impact point reconstruction can be chosen, depending on both the particle's incidence angle and the cluster multiplicity, so as to maximize the capability of the spectrometer in antiparticle tagging.Comment: 28 pages, 18 figures, submitted to Nuclear Instruments and Methods in Physics Research

Pushing the Boundaries of Conventional Core-Collapse Supernovae: The Extremely Energetic Supernova SN 2003ma

We report the discovery of a supernova (SN) with the highest apparent energy output to date and conclude that it represents an extreme example of the Type IIn subclass. The SN, which was discovered behind the Large Magellanic Cloud at z = 0.289 by the SuperMACHO microlensing survey, peaked at M_R = -21.5 mag and only declined by 2.9 mag over 4.7 years after the peak. Over this period, SN 2003ma had an integrated bolometric luminosity of 4 x 10^51 ergs, more than any other SN to date. The radiated energy is close to the limit allowed by conventional core-collapse explosions. Optical spectra reveal that SN 2003ma has persistent single-peaked intermediate-width hydrogen lines, a signature of interaction between the SN and a dense circumstellar medium. The light curves show further evidence for circumstellar interaction, including a long plateau with a shape very similar to the classic SN IIn 1988Z -- however, SN 2003ma is ten times more luminous at all epochs. The fast velocity measured for the intermediate-width H_alpha component (~6000 km/s) points towards an extremely energetic explosion (> 10^52 ergs), which imparts a faster blast-wave speed to the post-shock material and a higher luminosity from the interaction than is observed in typical SNe IIn. Mid-infrared observations of SN 2003ma suggest an infrared light echo is produced by normal interstellar dust at a distance ~0.5 pc from the SN.Comment: 21 pages, 15 figures, accepted for publication in Ap

Optical Spectroscopy of Supernova 1993J During Its First 2500 Days

We present 42 low-resolution spectra of Supernova (SN) 1993J, our complete collection from the Lick and Keck Observatories, from day 3 after explosion to day 2454, as well as one Keck high-dispersion spectrum from day 383. SN 1993J began as an apparent SN II, albeit an unusual one. After a few weeks, a dramatic transition took place, as prominent helium lines emerged in the spectrum. SN 1993J had metamorphosed from a SN II to a SN IIb. Nebular spectra of SN 1993J closely resemble those of SNe Ib and Ic, but with a persistent H_alpha line. At very late times, the H_alpha emission line dominated the spectrum, but with an unusual, box-like profile. This is interpreted as an indication of circumstellar interaction.Comment: 19 pages plus 13 figures, AASTeX V5.0. One external table in AASTeX V4.0, in landscape format. Accepted for publication in A

Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A Thirteen-Year Study of Spectral Variability in NGC 5548

We present the final installment of an intensive 13-year study of variations of the optical continuum and broad H-beta emission line in the Seyfert 1 galaxy NGC 5548. The data base consists of 1530 optical continuum measurements and 1248 H-beta measurements. The H-beta variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction that the size of the broad-line region is proportional to the square root of the ionizing luminosity. Moreover, the apparently linear nature of the correlation between the H-beta response time and the nonstellar optical continuum arises as a consequence of the changing shape of the continuum as it varies, specifically with the optical (5100 A) continuum luminosity proportional to the ultraviolet (1350 A) continuum luminosity to the 0.56 power.Comment: 20 pages plus 4 figures. Accepted for publication in The Astrophysical Journa

Three Gravitationally Lensed Supernovae Behind CLASH Galaxy Clusters

We report observations of three gravitationally lensed supernovae (SNe) in the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z = 0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters, MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and Abell 383 (z = 0.187), respectively. Each SN was detected in Hubble Space Telescope (HST) optical and infrared images. Based on photometric classification, we find that SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while the classification of SN CLA11Tib is inconclusive. Using multi-color light-curve fits to determine a standardized SN Ia luminosity distance, we infer that SN CLO12Car was approximately 1.0 +/- 0.2 mag brighter than field SNe Ia at a similar redshift and ascribe this to gravitational lens magnification. Similarly, SN CLN12Did is approximately 0.2 +/- 0.2 mag brighter than field SNe Ia. We derive independent estimates of the predicted magnification from CLASH strong+weak lensing maps of the clusters: 0.83 +/- 0.16 mag for SN CLO12Car, 0.28 +/- 0.08 mag for SN CLN12Did, and 0.43 +/- 0.11 mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens model predictions: we find that the magnifications based on the SN Ia brightness and those predicted by the lens maps are consistent. Our results herald the promise of future observations of samples of cluster-lensed SNe Ia (from the ground or space) to help illuminate the dark-matter distribution in clusters of galaxies, through the direct determination of absolute magnifications.Comment: ApJ in pres

Type Ia Supernova Rate Measurements To Redshift 2.5 From CANDELS: Searching For Prompt Explosions In The Early Universe

dThe Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) was a multi-cycle treasury program on the Hubble Space Telescope (HST) that surveyed a total area of -0.25 deg2 with -900 HST orbits spread across five fields over three years. Within these survey images we discovered 65 supernovae (SNe) of all types, out to z 2.5. We classify -24 of these as Type Ia SNe (SNe Ia) based on host galaxy redshifts and SN photometry (supplemented by grism spectroscopy of six SNe). Here we present a measurement of the volumetric SN Ia rate as a function of redshift, reaching for the first time beyond z =- 2 and putting new constraints on SN Ia progenitor models. Our highest redshift bin includes detections of SNe that exploded when the universe was only -3 Gyr old and near the peak of the cosmic star formation history. This gives the CANDELS high redshift sample unique leverage for evaluating the fraction of SNe Ia that explode promptly after formation ( 40 Myr. However, mild tension is apparent between ground-based low-z surveys and space-based high-z surveys. In both CANDELS and the sister HST program CLASH (Cluster Lensing And Supernova Survey with Hubble), we find a low rate of SNe Ia at z > 1. This could be a hint that prompt progenitors are in fact relatively rare, accounting for only 20% of all SN Ia explosions-though further analysis and larger samples will be needed to examine that suggestion. Key words: infrared: general - supernovae:Astronom

Deja Vu All Over Again: The Reappearance of Supernova Refsdal

In Hubble Space Telescope (HST) imaging taken on 2014 November 10, four images of supernova (SN) "Refsdal" (redshift z = 1.49) appeared in an Einstein-cross-like configuration (images S1–S4) around an early-type galaxy in the cluster MACS J1149.5+2223 (z = 0.54). Almost all lens models of the cluster have predicted that the SN should reappear within a year in a second host-galaxy image created by the cluster's potential. In HST observations taken on 2015 December 11, we find a new source at the predicted position of the new image of SN Refsdal approximately $8^{\prime\prime}$ from the previous images S1–S4. This marks the first time the appearance of a SN at a particular time and location in the sky was successfully predicted in advance! We use these data and the light curve from the first four observed images of SN Refsdal to place constraints on the relative time delay and magnification of the new image (SX) compared to images S1–S4. This enables us, for the first time, to test "blind" lens model predictions of both magnifications and time delays for a lensed SN. We find that the timing and brightness of the new image are consistent with the blind predictions of a fraction of the models. The reappearance illustrates the discriminatory power of this blind test and its utility to uncover sources of systematic uncertainty. From planned HST photometry, we expect to reach a precision of 1%–2% on the time delay between S1–S4 and SX

PTF11eon/SN2011dh: Discovery of a Type IIb Supernova From a Compact Progenitor in the Nearby Galaxy M51

On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and rapidly confirmed it to be a Type II supernova. Our early light curve and spectroscopy indicates that PTF11eon resulted from the explosion of a relatively compact progenitor star as evidenced by the rapid shock-breakout cooling seen in the light curve, the relatively low temperature in early-time spectra and the prompt appearance of low-ionization spectral features. The spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but initial signs of He appear to be present. Assuming that He lines continue to develop in the near future, this SN is likely a member of the cIIb (compact IIb; Chevalier and Soderberg 2010) class, with progenitor radius larger than that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor. Our data imply that the object identified in pre-explosion Hubble Space Telescope images at the SN location is possibly a companion to the progenitor or a blended source, and not the progenitor star itself, as its radius (~10^13 cm) would be highly inconsistent with constraints from our post-explosion photometric and spectroscopic data