Measuring the Radiative Histories of QSOs with the Transverse Proximity Effect

Since the photons that stream from QSOs alter the ionization state of the gas they traverse, any changes to a QSO's luminosity will produce outward-propagating ionization gradients in the surrounding intergalactic gas. This paper shows that at redshift z~3 the gradients will alter the gas's Lyman-alpha absorption opacity enough to produce a detectable signature in the spectra of faint background galaxies. By obtaining noisy (S:N~4) low-resolution (~7A) spectra of a several dozen background galaxies in an R~20' field surrounding an isotropically radiating 18th magnitude QSO at z=3, it should be possible to detect any order-of-magnitude changes to the QSO's luminosity over the previous 50--100 Myr and to measure the time t_Q since the onset of the QSO's current luminous outburst with an accuracy of ~5 Myr for t_Q<~50 Myr. Smaller fields-of-view are acceptable for shorter QSO lifetimes. The major uncertainty, aside from cosmic variance, will be the shape and orientation of the QSO's ionization cone. This can be determined from the data if the number of background sources is increased by a factor of a few. The method will then provide a direct test of unification models for AGN.Comment: Accepted for publication in the ApJ. 16 page

A population and harvest intensity estimate for Sooty Shearwater, Puflinus griseus, on Taukihepa (Big South Cape), New Zealand

We estimated the total number of burrow entrances, chicks and total population size of the Sooty Shearwater, Puffinusgriseus, colony on Taukihepa (Big South Cape), the largest of the 36 Titi Islands where Titi (Sooty Shcarwater chicks) are harvested. Between 1999 and 2005 we surveyed six manu (family birded areas) as well as a colony in the interior forested region on the island, measuring entrance density and burrow occupancy and habitat variables, as well as recording birders' harvest intensity. We found little support for any relationship between habitat variables and entrance density on the surveyed manu. Therefore we used a detailed aerial image to map areas and extrapolate these estimates to island totals and a simple population model, incorporating known demographic parameters to calculate the total population size. We estimated that the island contains 1.67 million (95% CI: 1.47-1.88) burrow entrances and 1.12 million (0.959-1.28) breeding pairs, equating to a total of 5.31 million (95% CI: 3.98-6.77) juveniles, pre-breeders and adults associated with the island. Assuming the harvest intensity on the surveyed manu 0.18% (0.16-0.21) was similar elsewhere on the unsurveyed but harvested region of the island, we estimated that ofthe 807000 (712000-901 000) fledging chicks on the island, 137000 (105000-173000) are harvested each year. These findings highlight the importance of the island both in terms of total Sooty Shearwater population in New Zealand and to the Rakiura Maori who harvest the Titi

The Eastwood-Singer gauge in Einstein spaces

Electrodynamics in curved spacetime can be studied in the Eastwood--Singer gauge, which has the advantage of respecting the invariance under conformal rescalings of the Maxwell equations. Such a construction is here studied in Einstein spaces, for which the Ricci tensor is proportional to the metric. The classical field equations for the potential are then equivalent to first solving a scalar wave equation with cosmological constant, and then solving a vector wave equation where the inhomogeneous term is obtained from the gradient of the solution of the scalar wave equation. The Eastwood--Singer condition leads to a field equation on the potential which is preserved under gauge transformations provided that the scalar function therein obeys a fourth-order equation where the highest-order term is the wave operator composed with itself. The second-order scalar equation is here solved in de Sitter spacetime, and also the fourth-order equation in a particular case, and these solutions are found to admit an exponential decay at large time provided that square-integrability for positive time is required. Last, the vector wave equation in the Eastwood-Singer gauge is solved explicitly when the potential is taken to depend only on the time variable.Comment: 13 pages. Section 6, with new original calculations, has been added, and the presentation has been improve

Deliberate self-harm, substance use and negative affect in nonclinical samples: A systematic review

BACKGROUND AND METHOD: A systematic literature review was conducted to examine associations between self-harm, substance use, and negative affect in nonclinical samples. RESULTS: Forty-two articles describing 36 studies were identified that met the inclusion criteria. Findings indicated that individuals who engage in substance use are significantly more likely to engage in self-harm. It was also found that negative affective states such as depression and anxiety are consistently associated with self-harm. CONCLUSIONS: These findings provide some guidance in identifying those who are at increased risk of self-harm. Reducing these risk factors could be an important strategy in preventing self-harm behavior in the general population

Heating in the Accreted Neutron Star Ocean: Implications for Superburst Ignition

We perform a self-consistent calculation of the thermal structure in the crust of a superbursting neutron star. In particular, we follow the nucleosynthetic evolution of an accreted fluid element from its deposition into the atmosphere down to a depth where the electron Fermi energy is 20 MeV. We include temperature-dependent continuum electron capture rates and realistic sources of heat loss by thermal neutrino emission from the crust and core. We show that, in contrast to previous calculations, electron captures to excited states and subsequent gamma-emission significantly reduce the local heat loss due to weak-interaction neutrinos. Depending on the initial composition these reactions release up to a factor of 10 times more heat at densities < 10^{11} g/cc than obtained previously. This heating reduces the ignition depth of superbursts. In particular, it reduces the discrepancy noted by Cumming et al. between the temperatures needed for unstable 12C ignition on timescales consistent with observations and the reduction in crust temperature from Cooper pair neutrino emission.Comment: 10 pages, 11 figures, the Astrophysical Journal, in press (scheduled for v. 662). Revised from v1 in response to referee's comment

First Results from the Large Area Lyman Alpha Survey

We report on a new survey for z=4.5 Lyman alpha sources, the Large Area Lyman Alpha (LALA) survey. Our survey achieves an unprecedented combination of volume and sensitivity by using narrow-band filters on the new 8192x8192 pixel CCD Mosaic Camera at the 4 meter Mayall telescope of Kitt Peak National Observatory. Well-detected sources with flux and equivalent width matching known high redshift Lyman alpha galaxies (i.e., observed equivalent width above 80 Angstroms and line+continuum flux between 2.6e-17 and 5.2e-17 erg/cm^2/sec in an 80 Angstrom filter) have an observed surface density corresponding to 11000 +- 700 per square degree per unit redshift at z=4.5. Spatial variation in this surface density is apparent on comparison between counts in 6561 and 6730 Angstrom filters. Early spectroscopic followup results from the Keck telescope included three sources meeting our criteria for good Lyman alpha candidates. Of these, one is confirmed as a z=4.52 source, while another remains consistent with either z=4.55 or z=0.81. We infer that 30 to 50% of our good candidates are bona fide Lyman alpha emitters, implying a net density of about 4000 Lyman alpha galaxies per square degree per unit redshift.Comment: 10 pages, 2 figures (3 .ps files), uses AASTeX 4. Submitted to The Astrophysical Journal Letter

Aging predicts decline in explicit and implicit memory: a life-span study

Explicit memory declines with age, but age effects on implicit memory are debated. This issue is important because if implicit memory is age-invariant, it may support effective interventions in individuals experiencing memory decline. This study overcame several methodological issues in past research to clarify age effects on implicit memory (priming) and their relationship to explicit memory (recognition, source memory). It aimed to (1) recruit a large lifespan sample of participants (N=1072) during a residency at the Science Museum, London, (2) employ an implicit task that is unaffected by explicit contamination, and (3) systematically manipulate depth-of-processing and attention to assess their contribution to age effects. Participants witnessed a succession of overlapping colored objects, attending to one colour stream and ignoring the other, and at test identified masked objects before judging whether they were previously attended, unattended, or new. Age significantly predicted decline in both explicit and implicit memory for attended objects