Multidimensional Simulations of Rotating Pair Instability Supernovae

We study the effects of rotation on the dynamics, energetics and Ni-56 production of Pair Instability Supernova explosions by performing rotating two-dimensional ("2.5-D") hydrodynamics simulations. We calculate the evolution of eight low metallicity (Z = 10^-3, 10^-4 Zsun) massive (135-245 Msun) PISN progenitors with initial surface rotational velocities 50% that of the critical Keplerian value using the stellar evolution code MESA. We allow for both the inclusion and the omission of the effects of magnetic fields in the angular momentum transport and in chemical mixing, resulting in slowly-rotating and rapidly-rotating final carbon-oxygen cores, respectively. Increased rotation for carbon-oxygen cores of the same mass and chemical stratification leads to less energetic PISN explosions that produce smaller amounts of Ni-56 due to the effect of the angular momentum barrier that develops and slows the dynamical collapse. We find a non-monotonic dependence of Ni-56 production on rotational velocity in situations when smoother composition gradients form at the outer edge of the rotating cores. In these cases, the PISN energetics are determined by the competition of two factors: the extent of chemical mixing in the outer layers of the core due to the effects of rotation in the progenitor evolution and the development of angular momentum support against collapse. Our 2.5-D PISN simulations with rotation are the first presented in the literature. They reveal hydrodynamic instabilities in several regions of the exploding star and increased explosion asymmetries with higher core rotational velocity.Comment: 31 pages, 23 figures, accepted for publication in the Ap

Core-Collapse Supernova Simulations including Neutrino Interactions from the Virial EOS

Core-collapse supernova explosions are driven by a central engine that converts a small fraction of the gravitational binding energy released during core collapse to outgoing kinetic energy. The suspected mode for this energy conversion is the neutrino mechanism, where a fraction of the neutrinos emitted from the newly formed protoneutron star are absorbed by and heat the matter behind the supernova shock. Accurate neutrino-matter interaction terms are crucial for simulating these explosions. In this proceedings for IAUS 331, SN 1987A, 30 years later, we explore several corrections to the neutrino-nucleon scattering opacity and demonstrate the effect on the dynamics of the core-collapse supernova central engine via two dimensional neutrino-radiation-hydrodynamics simulations. Our results reveal that the explosion properties are sensitive to corrections to the neutral-current scattering cross section at the 10-20% level, but only for densities at or above $\sim 10^{12}$ g cm$^{-3}$Comment: 6 pages, 3 figures, appears in Proc. IAU Symposium 331, SN 1987A, 30 years later - Cosmic Rays and Nuclei from Supernovae and Their Aftermath

Discovery of a Large-scale Wall in the Direction of Abell 22

We report on the discovery of a large-scale wall in the direction of Abell 22. Using photometric and spectroscopic data from the Las Campanas Observatory and Anglo-Australian Telescope Rich Cluster Survey, Abell 22 is found to exhibit a highly unusual and striking redshift distribution. We show that Abell 22 exhibits a foreground wall-like structure by examining the galaxy distributions in both redshift space and on the colour-magnitude plane. A search for other galaxies and clusters in the nearby region using the 2dF Galaxy Redshift Survey database suggests that the wall-like structure is a significant large-scale, non-virialized filament which runs between two other Abell clusters either side of Abell 22. The filament stretches over at least >40 Mpc in length and 10 Mpc in width at the redshift of Abell 22.Comment: 6 pages, 4 figures, accepted for publication in MNRAS letter

Spatially Resolved Spectroscopy of the E+A Galaxies in the z=0.32 Cluster AC114

We present spatially resolved intermediate resolution spectroscopy of a sample of twelve E+A galaxies in the z=0.32 rich galaxy cluster AC 114, obtained with the FLAMES multi-integral field unit system on the European Southern Observatory's VLT. Previous integrated spectroscopy of all these galaxies by Couch & Sharples (1987) had shown them to have strong Balmer line absorption and an absence of [OII 3727] emission -- the defining characteristics of the``E+A'' spectral signature, indicative of an abrupt halt to a recent episode of quite vigorous star formation. We have used our spectral data to determine the radial variation in the strength of Hdelta absorption in these galaxies and hence map out the distribution of this recently formed stellar population. Such information provides important clues as to what physical event might have been responsible for this quite dramatic change in star formation activity in these galaxies' recent past. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: Four galaxies show little Hdelta absorption across their entire extent; it would appear they were misidentified as E+A galaxies in the earlier integrated spectroscopic studies. The remainder show strong Hdelta absorption, with a gradient that is either negative (Hdelta equivalent width decreasing with radius), flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies. It would seem therefore that more than one physical mechanism is responsible for E+A formation in the same environment.Comment: 15 pages, 10 figures, accepted MNRA

Hepatic acute phase response protects the brain from focal inflammation during postnatal window of susceptibility

Perinatal inflammation is known to contribute to neurodevelopmental diseases. Animal models of perinatal inflammation have revealed that the inflammatory response within the brain is age dependent, but the regulators of this variation remain unclear. In the adult, the peripheral acute phase response (APR) is known to be pivotal in the downstream recruitment of leukocytes to the injured brain. The relationship between perinatal brain injury and the APR has not been established. Here, we generated focal inflammation in the brain using interleukin (IL)-1β at postnatal day (P)7, P14, P21 and P56 and studied both the central nervous system (CNS) and hepatic inflammatory responses at 4 h. We found that there is a significant window of susceptibility in mice at P14, when compared to mice at P7, P21 and P56. This was reflected in increased neutrophil recruitment to the CNS, as well as an increase in blood–brain barrier permeability. To investigate phenomena underlying this window of susceptibility, we performed a dose response of IL-1β. Whilst induction of endogenous IL-1β or intercellular adhesion molecule (ICAM)-1 in the brain and induction of a hepatic APR were dose dependent, the recruitment of neutrophils and associated blood–brain barrier breakdown was inversely proportional. Furthermore, in contrast to adult animals, an additional peripheral challenge (intravenous IL-1β) reduced the degree of CNS inflammation, rather than exacerbating it. Together these results suggest a unique window of susceptibility to CNS injury, meaning that suppressing systemic inflammation after brain injury may exacerbate the damage caused, in an age-dependent manner

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Research and evidence based environmental health

Environmental health (EH) professionals have often spoken of the need to become more research active (Burke et al., 2002; McCarthy, 1996) and make their work more evidence based, but to date little has been written about how to achieve this in practice. This chapter is therefore written as an introductory guide to research for EH professionals, students, and policy makers. By developing your knowledge it is hoped you will feel more confident navigating the world of research; motivated towards making your own work more evidence based; and enthused about contributing to the evidence base from which others can learn. This chapter is not a research methods textbook, a step by step guide to research or evidence based environmental health, nor does it seek to make definitive statements about these complex areas. However it highlights the most important issues regarding research in environmental health, considers the importance of research to the environmental health profession and provides useful signposts towards further resources. The chapter is divided into three sections. The first defines evidence based environmental health and why it remains a priority for EH professionals. The second section explores the key stages of environmental health research and provides guidance on the development of your reading skills. The final section suggests ways to become more research active and evidence based, acknowledging the many challenges EH professionals face and concluding with a vision for evidence based environmental health. The chapter ends with an annex including a glossary of environmental health research terms, a list of references and suggested further reading

Northeast IPM Center Participation by the NYS IPM Program, 2006

NYS IPM Program staff were involved with several key activities of theNortheast IPM Center in 2006. Included were participation and leadership in the Center’s Working Groups and meeting with Natural Resource Conservation Service representatives

Lopsided Galaxies, Weak Interactions and Boosting the Star Formation Rate

To investigate the link between weak tidal interactions in disk galaxies and the boosting of their recent star formation, we obtain images and spatially integrated spectra (3615A < lambda < 5315A) for 40 late-type spiral galaxies (Sab-Sbc) with varying degrees of lopsidedness (a dynamical indicator of weak interactions). We quantify lopsidedness as the amplitude of the m=1 Fourier component of the azimuthal surface brightness distribution, averaged over a range of radii. We compare the young stellar content, quantified by EW(H\delta_abs) and the strength of the 4000 Angstrom break (D_4000), with lopsidedness and find a 3-4 sigma correlation between the two. We also find a 3.2 sigma correlation between EW(H\beta_emission) and lopsidedness. Using the evolutionary population synthesis code of Bruzual & Charlot we model the spectra as an ``underlying population'' and a superimposed ``boost population'' with the aim of constraining the fractional boost in the SFR averaged over the past 0.5 Gyr (the characteristic lifetime of lopsidedness). From the difference in both EW(H\delta_abs) and D_4000 between the most and least symmetric thirds of our sample, we infer that ~ 1x10^9 M_solar of stars are formed over the duration of a lopsided event in addition to the ``underlying'' SFH (assuming a final galactic stellar mass of 10^10 M_solar). This corresponds to a factor of 8 increase in the SFR over the past 5x10^8 years. For the nuclear spectra, all of the above correlations except D_4000 vs. are weaker than for the disk, indicating that in lopsided galaxies, the SF boost is not dominated by the nucleus.Comment: 35 pages, including 10 figures, to appear in the Astrophysical Journal, abridged abstrac