On Pulsar Distance Measurements and their Uncertainties

Accurate distances to pulsars can be used for a variety of studies of the Galaxy and its electron content. However, most distance measures to pulsars have been derived from the absorption (or lack thereof) of pulsar emission by Galactic HI gas, which typically implies that only upper or lower limits on the pulsar distance are available. We present a critical analysis of all measured HI distance limits to pulsars and other neutron stars, and translate these limits into actual distance estimates through a likelihood analysis that simultaneously corrects for statistical biases. We also apply this analysis to parallax measurements of pulsars in order to obtain accurate distance estimates and find that the parallax and HI distance measurements are biased in different ways, because of differences in the sampled populations. Parallax measurements typically underestimate a pulsar's distance because of the limited distance to which this technique works and the consequential strong effect of the Galactic pulsar distribution (i.e. the original Lutz-Kelker bias), in HI distance limits, however, the luminosity bias dominates the Lutz-Kelker effect, leading to overestimated distances because the bright pulsars on which this technique is applicable are more likely to be nearby given their brightness.Comment: 32 pages, 1 figure, 2 tables; Accepted for publication in the Astrophysical Journa

The coastal Robinson

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Dynamics of Atmospheres and Oceans 52 (2011): 4-7, doi:10.1016/j.dynatmoce.2011.01.004.Allan Robinson made important contributions to coastal oceanography in at least two major ways. First, in 1964, he introduced continental shelf waves to the nascent coastal oceanography community, and so initiated a very profitable line of research that remained active for two decades. Second, he had the drive and vision to conceive of, and then direct, the first global synthesis of coastal oceanography.This contribution was written under the support of the National Science Foundation, Physical Oceanography grant OCE-0849498

Distance Determination to the Crab-like PWN G54.1+0.3 and Search for its Supernova Remnant Shell

We discover a large-scale shell G53.9+0.2 around the Crab-like pulsar wind nebula (PWN) G54.1+0.3 with 1420 MHz continuum VLA observations. This is confirmed by a new infrared image at 8 \mu m from the GLIMPSE Legacy Project, which reveals an intriguing infrared shell just surrounding the large radio shell. We analyze the 21 cm HI absorption spectra and 13CO emission spectra towards PWN G54.1+0.3 and bright sources on both radio and IR shells. Continuous HI absorption up to the tangent point and absence of negative HI absorption features imply that PWN G54.1+0.3 has a distance beyond the tangent point but within the Solar circle, i.e. 4.5 to 9 kpc. G54.1+0.3 is likely at distance of \simeq 6.2 kpc due to the morphological association between the PWN and a CO molecular cloud at velocity of \simeq 53 km/s, as revealed by high-resolution 13CO images. Based on the HI absorption spectrum and recombination line velocity (\simeq 40 km/s) of the bright HII region G54.09-0.06, which is on the IR shell, the IR shell is likely located at a distance of \simeq 7.3 kpc, which is also the distance of the associated large-scale radio shell. At this distance, the radio shell has a radius of ~ 30 pc. The radio shell may be thermal and lack IR emission due to dust destruction, or it may be nonthermal and part of a newly found old SNR. In either case it is located at a different distance than PWN G54.1+0.3.Comment: 11 page, 3 figures, accepted by A

Similarities between the tropical Atlantic seasonal cycle and ENSO: An energetics perspective

The tropical Pacific and Atlantic Oceans have similar mean states - easterly winds and a zonally sloping thermocline which shoals in the east - but strikingly different sea surface temperature..

On mean and seasonal currents and transports at the western boundary of the equatorial Atlantic

Current measurements from two consecutive yearlong deployments of three moored stations at the western end of the equator in the Atlantic, along 44°W, are used to determine the northwestward flow of warm water in the upper several 100 m and of the southeastward counterflow of North Atlantic Deep Water (NADW). Measurements from three acoustic Doppler current profilers (ADCPs) looking upward from 300 m toward the surface allowed calculation of a time series of upper layer transports over 1 year. Mean transport through the array for the upper 300 m is 23.8 Sv with an annual cycle of only ±3 Sv that has its maximum in June-August and minimum in northern spring. Estimated additional mean northwestward transport in the range 300–600 m is 6.7 Sv, based on moored data and shipboard Pegasus and lowered ADCP profiling. In the depth range 1400–3100 m a current core with maximum annual mean southeastward speed of 30 cm s−1 is found along the continental slope that carries an estimated upper NADW transport of 14.2–17.3 Sv, depending on the extrapolation used between the mooring in the core and the continental slope. This transport is higher than off-equatorial estimates and suggests near-equatorial recirculation at the upper NADW level, in agreement with northwestward mean flow found about 140 km offshore. Below 3100 m and above the 1.8°C isotherm, only a small core of lower NADW flow with speeds of 10–15 cm s−1 is found over the flat part of the basin near 1.5°N, clearly separated from the continental slope by a zone of near-zero mean speeds. Estimated transport of that small current core is about 4.5 Sv, which is significantly below other estimates of near-equatorial transport of lower NADW and suggests that a major fraction of lower NADW may cross the 44°W meridian north of the Ceara Rise. Intraseasonal variability is large, although smaller than observed at 8°N near the western boundary. It occurs at a period of about 1 month when it is dominant in the near-surface records and corresponds to earlier observations in the equatorial zones of all oceans and at a period of about 2 months when it is dominant at the NADW level and could be imported either from the north along the boundary or from the east along the equator. The existence of an annual cycle in the deep currents of a few centimeters per second amplitude, as suggested by high-resolution numerical model results, could neither be proven nor disproven because of the high amount of shorter-period variability

Comparing Wild 2 Particles to Chondrites and IDPS

We compare the observed composition ranges of olivine, pyroxene and Fe-Ni sulfides in Wild 2 grains, comparing these with chondritic IDPs and chondrite classes to explore whether these data suggest affinities to known hydrous materials in particular. Wild 2 olivine has an extremely wide composition range, from Fo4-100 with a pronounced frequency peak at Fo99. The composition range displayed by the low-calcium pyroxene is also very extensive, from En52 to En100, with a significant frequency peak centered at En95. These ranges are as broad or broader than those reported for any other extraterrestrial material. Wild 2 Fe-Ni sulfides mainly have compositions close to that of FeS, with less than 2 atom % Ni - to date, only two pentlandite grains have been found among the Wild-grains suggesting that this mineral is not abundant. The complete lack of compositions between FeS and pentlandite (with intermediate solid solution compositions) suggests (but does not require) that FeS and pentlandite condensed as crystalline species, i.e. did not form as amorphous phases, which later became annealed. While we have not yet observed any direct evidence of water-bearing minerals, the presence of Ni-bearing sulfides, and magnesium-dominated olivine and low-Ca pyroxene does not rule out their presence at low abundance. We do conclude that modern major and minor element compositions of chondrite matrix and IDPs are needed

Portrait of an artist as collaborator: an interpretative phenomenological analysis of an artist

The subjective experience of being an artist was examined using interpretative phenomenological analysis (IPA), focusing on the perspective of the artist but interpreted by me, a psychologist, from my perspective as an artistic collaborator. Building upon a literature that has hitherto focused on clinical, elderly, or vulnerable participants, I interpreted superordinate themes of Process (Constraint, Playfulness, Movement) and Identity (The Ill-Defined Artist, Becoming, Mixing Identities, Choosing an Identity, Calling, Collaboration, and Outsider). These themes are broadly similar to the existing literature, but emphasise identity while de-emphasising self reflection and the need to become an “insider.

Anticipating and Adapting to the Future Impacts of Climate Change on the Health, Security and Welfare of Low Elevation Coastal Zone (LECZ) Communities in Southeastern USA

Low elevation coastal zones (LECZ) are extensive throughout the southeastern United States. LECZ communities are threatened by inundation from sea level rise, storm surge, wetland degradation, land subsidence, and hydrological flooding. Communication among scientists, stakeholders, policy makers and minority and poor residents must improve. We must predict processes spanning the ecological, physical, social, and health sciences. Communities need to address linkages of (1) human and socioeconomic vulnerabilities; (2) public health and safety; (3) economic concerns; (4) land loss; (5) wetland threats; and (6) coastal inundation. Essential capabilities must include a network to assemble and distribute data and model code to assess risk and its causes, support adaptive management, and improve the resiliency of communities. Better communication of information and understanding among residents and officials is essential. Here we review recent background literature on these matters and offer recommendations for integrating natural and social sciences. We advocate for a cyber-network of scientists, modelers, engineers, educators, and stakeholders from academia, federal state and local agencies, non-governmental organizations, residents, and the private sector. Our vision is to enhance future resilience of LECZ communities by offering approaches to mitigate hazards to human health, safety and welfare and reduce impacts to coastal residents and industries

Modified Gravity and Cosmology

In this review we present a thoroughly comprehensive survey of recent work on modified theories of gravity and their cosmological consequences. Amongst other things, we cover General Relativity, Scalar-Tensor, Einstein-Aether, and Bimetric theories, as well as TeVeS, f(R), general higher-order theories, Horava-Lifschitz gravity, Galileons, Ghost Condensates, and models of extra dimensions including Kaluza-Klein, Randall-Sundrum, DGP, and higher co-dimension braneworlds. We also review attempts to construct a Parameterised Post-Friedmannian formalism, that can be used to constrain deviations from General Relativity in cosmology, and that is suitable for comparison with data on the largest scales. These subjects have been intensively studied over the past decade, largely motivated by rapid progress in the field of observational cosmology that now allows, for the first time, precision tests of fundamental physics on the scale of the observable Universe. The purpose of this review is to provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a self-contained, comprehensive and up-to-date introduction to the subject as a whole.Comment: 312 pages, 15 figure