Confronting cold dark matter predictions with observed galaxy rotations

The rich statistics of galaxy rotations as captured by the velocity function (VF) provide invaluable constraints on galactic baryon physics and the nature of dark matter (DM). However, the comparison of observed galaxy rotations against cosmological models is prone to subtle caveats that can easily lead to misinterpretations. Our analysis reveals full statistical consistency between similar to 5000 galaxy rotations, observed in line-of-sight projection, and predictions based on the standard cosmological model (Lambda CDM) at the mass-resolution of the Millennium simulation (H I line-based circular velocities above similar to 50 km s(-1)). Explicitly, the H I linewidths in the H I Parkes All Sky Survey (HIPASS) are found to be consistent with those in S-3-SAX, a post-processed semi-analytic model for the Millennium simulation. Previously found anomalies in the VF can be plausibly attributed to (1) the mass-limit of the Millennium simulation, (2) confused sources in HIPASS, (3) inaccurate inclination measurements for optically faint sources, and (4) the non-detectability of gas-poor early-type galaxies. These issues can be bypassed by comparing observations and models using linewidth source counts rather than VFs. We investigate if and how well such source counts can constrain the temperature of DM

The General Hopelessness Scale: development of a measure of hopelessness for non-clinical samples

Noting concerns about the non-clinical efficacy of the Beck Hopelessness Scale (BHS), specifically the instrument’s ability to discriminate between lower levels of hopelessness, this paper describes the development of the General Hopelessness Scale (GHS) for use with general samples. Following a literature review an item pool assessing the breadth of the hopelessness construct domain was created. This was then placed in survey form and assessed within two independent studies. Study 1 (N = 305, 172 women, 133 men, Mage = 28.68) explored factorial structure, item performance, and convergent validity of the GHS in relation to standardised measures of self-esteem and trait hopelessness. In Study 2 (N = 326, 224 women, 102 men, Mage = 26.52), scrutiny of the GHS occurred using confirmatory factor analysis and invariance tests, alongside item performance and convergent validity analyses relative to measures of affect, optimism, and hope. Factor analysis (using minimum average partial correlations and exploratory factor analysis) within Study 1 revealed the existence of four dimensions (Negative Expectations, Hope, Social Comparison, and Futility), which met Rasch model assumptions (i.e., good item/person fit and item/person reliability). Further psychometric assessment within Study 2 found satisfactory model fit and gender invariance. Convergent validity testing revealed moderate to large associations between the GHS and theoretically relevant variables (self-esteem, trait hopelessness, affect, optimism, and hope) across Study 1 and 2. Further examination of performance (reliability and ceiling and floor effects) within Study 1 and 2 demonstrated that the GHS was a satisfactory measure in non-clinical settings. Additionally, unlike the BHS, the GHS does not assume that administrators are trained professionals capable of advising on appropriate interventions

Thinking Style and Paranormal Belief: The Role of Cognitive Biases

This study investigated the degree to which cognitive bias mediated the relationship between thinking style and belief in the paranormal. A sample of 496 participants completed the Revised Paranormal Belief Scale (RPBS), the Belief in Science Scale (BISS), the Cognitive Biases Questionnaire for Psychosis, and the reality testing subscale of the Inventory of Personality Organization (IPO-RT). The BISS and IPO-RT served as proxy indices of preferred thinking style; the BISS assessed rational-analytical (objective) processing, and the IPO-RT intuitive-experiential (subjective) processing. Cognitive biases (Jumping to Conclusions, Intentionalising, Catastrophising, Emotional Reasoning, and dichotomous thinking) correlated positively with belief in the paranormal. Mediation using path analysis indicated that Emotional Reasoning and Catastrophising exerted indirect effects in relation to BISS, IPO-RT and RPBS. Direct relationships existed between IPO-RT and RPBS, and BISS and RPBS. Of the biases, only Emotional Reasoning and Catastrophising predicted RPBS. The contribution of Emotional Reasoning and Catastrophising to belief in the paranormal were consistent with previous research and the cognitive model of psychosis, which asserts that there are strong relationships between defective reality testing, emotional reasoning and delusional beliefs

The WiggleZ dark energy survey

The accelerating expansion of the universe, attributed to "dark energy", has no accepted theoretical explanation. The origin of this phenomenon unambiguously implicates new physics via a novel form of matter exerting negative pressure or an alteration to Einstein's general relativity. These profound consequences have inspired a new generation of cosmological surveys that will measure the influence of dark energy using various techniques. One of the forerunners is the WiggleZ Survey at the Anglo-Australian Telescope, a new large-scale high-redshift galaxy survey that is now 50% complete and scheduled to finish in 2010. The WiggleZ project is aiming to map the cosmic expansion history using delicate features in the galaxy clustering pattern imprinted 13.7 billion years ago. In this article we outline the survey design and context, and predict the science highlights

Making sense of social prescribing

This booklet provides advice and guidance on all things social prescribing

The WiggleZ Dark Energy Survey: the selection function and z=0.6 galaxy power spectrum

We report one of the most accurate measurements of the three-dimensional large-scale galaxy power spectrum achieved to date, using 56,159 redshifts of bright emission-line galaxies at effective redshift z=0.6 from the WiggleZ Dark Energy Survey at the Anglo-Australian Telescope. We describe in detail how we construct the survey selection function allowing for the varying target completeness and redshift completeness. We measure the total power with an accuracy of approximately 5% in wavenumber bands of dk=0.01 h/Mpc. A model power spectrum including non-linear corrections, combined with a linear galaxy bias factor and a simple model for redshift-space distortions, provides a good fit to our data for scales k < 0.4 h/Mpc. The large-scale shape of the power spectrum is consistent with the best-fitting matter and baryon densities determined by observations of the Cosmic Microwave Background radiation. By splitting the power spectrum measurement as a function of tangential and radial wavenumbers we delineate the characteristic imprint of peculiar velocities. We use these to determine the growth rate of structure as a function of redshift in the range 0.4 < z < 0.8, including a data point at z=0.78 with an accuracy of 20%. Our growth rate measurements are a close match to the self-consistent prediction of the LCDM model. The WiggleZ Survey data will allow a wide range of investigations into the cosmological model, cosmic expansion and growth history, topology of cosmic structure, and Gaussianity of the initial conditions. Our calculation of the survey selection function will be released at a future date via our website wigglez.swin.edu.au.Comment: 21 pages, 22 figures, accepted for publication in MNRA

The WiggleZ project: AAOmega and Dark Energy

We describe the `WiggleZ' spectroscopic survey of 280,000 star-forming galaxies selected from a combination of GALEX ultra-violet and SDSS + RCS2 optical imaging. The fundamental goal is a detection of the baryonic acoustic oscillations in galaxy clustering at high-redshift (0.5 < z < 1) and a precise measurement of the equation of state of dark energy from this purely geometric and robust method. The survey has already started on the 3.9m Anglo-Australian Telescope using the AAOmega spectrograph, and planned to complete during 2009. The WWW page for the survey can be found at http://astronomy.swin.edu.au/wigglezComment: To appear in the Proceedings of the Durham "Cosmic Frontiers" ASP conference eds. Metcalfe & Shanks, 8 pages, 5 figures, (Version 2: updated May 2007 with final analysis of data through to Nov 2006.

The WiggleZ Dark Energy Survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant supernovae

Astronomical observations suggest that today's Universe is dominated by a dark energy of unknown physical origin. One of the most notable results obtained from many models is that dark energy should cause the expansion of the Universe to accelerate: but the expansion rate as a function of time has proved very difficult to measure directly. We present a new determination of the cosmic expansion history by combining distant supernovae observations with a geometrical analysis of large-scale galaxy clustering within the WiggleZ Dark Energy Survey, using the Alcock-Paczynski test to measure the distortion of standard spheres. Our result constitutes a robust and non-parametric measurement of the Hubble expansion rate as a function of time, which we measure with 10-15 per cent precision in four bins within the redshift range 0.1 < z < 0.9. We demonstrate, in a manner insensitive to the assumed cosmological model, that the cosmic expansion is accelerating. Furthermore, we find that this expansion history is consistent with a cosmological-constant dark energy

The WiggleZ Dark Energy Survey: small-scale clustering of Lyman-break galaxies at z < 1

The WiggleZ Dark Energy Survey is a large-scale structure survey of intermediate-redshift ultraviolet-selected (UV-selected) emission-line galaxies scheduled to cover 1000 deg^2, spanning a broad redshift range 0.2 < z < 1.0 . The main scientific goal of the survey is the measurement of baryon acoustic oscillations (BAO) in the galaxy clustering pattern at a significantly higher redshift than previous studies. The BAO may be applied as a standard cosmological ruler to constrain dark energy models. Based on the first 20 per cent of the data set, we present initial results concerning the small-scale clustering of the WiggleZ targets, together with survey forecasts. The WiggleZ galaxy population possesses a clustering length r_0 = 4.40 ± 0.12 h^(−1) Mpc, which is significantly larger than z = 0 UV-selected samples, with a slope γ = 1.92 ± 0.08 . This clustering length is comparable to z = 3 Lyman-break galaxies with similar UV luminosities. The clustering strength of the sample increases with optical luminosity, UV luminosity and reddening rest-frame colour. The full survey, scheduled for completion in 2010, will map an effective volume V_eff ≈ 1 Gpc^3 (evaluated at a scale k = 0.15 h Mpc^(−1)) and will measure the angular diameter distance and Hubble expansion rates in three redshift bins with accuracies of ≈5 per cent. We will determine the value of a constant dark energy equation-of-state parameter, wcons, with a higher precision than existing supernovae observations using an entirely independent technique. The WiggleZ and supernova measurements lie in highly complementary directions in the plane of w_(cons) and the matter density Ω_m. The forecast using the full combination of WiggleZ, supernova and cosmic microwave background (CMB) data sets is a marginalized error Δw_(cons) = 0.07 , providing a robust and precise measurement of the properties of dark energy including cross-checking of systematic errors