Cometary airbursts and atmospheric chemistry: Tunguska and a candidate Younger Dryas event (2009)
Melott, Adrian L., Thomas, Brian C., Dreschhoff, Gisela, Johnson, Carey K.
We estimate atmospheric chemistry changes from ionization for the 1908 Tunguska airburst event, finding agreement with nitrate enhancement in GISP2H and GISP2 ice cores, noting an unexplained...
Testing the link between terrestrial climate change and Galactic spiral arm transit (2009)
Overholt, Andrew C., Melott, Adrian L., Pohl, Martin K.
We re-examine past suggestions of a close link between terrestrial climate change and the Sun's transit of spiral arms in its path through the Milky Way galaxy. These links produced concrete fits,...
Melott, Adrian L., Thomas, Brian C.
Based on the intensity and rates of various kinds of intense ionizing radiation events such as supernovae and gamma-ray bursts, it is likely that the Earth has been subjected to one or extinction...
Long-term cycles in the history of life: Periodic biodiversity in the Paleobiology Database (2008)
Time series analysis of fossil biodiversity of marine invertebrates in the Paleobiology Database (PBDB) shows a significant periodicity at approximately 63 My, in agreement with previous analyses...
A Lookup Table to Compute High Energy Cosmic Ray Effects on Terrestrial Atmospheric Chemistry (2008)
Melott, Adrian L., Atri, Dimitra, Thomas, Brian C., Krejci, Alex J., U), Washburn
A variety of events such as gamma-ray bursts and supernovae may expose the Earth to an increased flux of high-energy cosmic rays, with potentially important effects on the biosphere. Existing...
Essential equivalence of the conclusions of Romeo et al. (arXiv:0804.0294v1) with earlier work is pointed out. A possible general explanation for these conclusions is suggested.
Wang and White (2007) have discussed some problems with N-body simulation methods. These problems are a special case of a more general problem which has been largely unacknowledged for approximately...
Superluminous supernovae: No threat from Eta Carinae (2007)
Thomas, Brian C., Melott, Adrian L., Fields, Brian D., Anthony-Twarog, Barbara J.
Recently Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of ~10^44 Joules. It was proposed that the progenitor may have been a massive evolved star similar...
Lieberman, Bruce S., Melott, Adrian L.
Medvedev and Melott (2007) have suggested that periodicity in fossil biodiversity may be induced by cosmic rays which vary as the Solar System oscillates normal to the galactic disk. We re-examine...
Fossil Biodiversity: Red Noise Plus Signal (2006)
Melott, Adrian L., Lieberman, Bruce S.
We have examined the Fourier power spectrum as well as the Hurst exponent of extinction, origination, and total biodiversity in the marine fossil record, using a recently improved geologic timescale....
Terrestrial Consequences of Spectral and Temporal Variability in Ionizing Photon Events (2006)
Ejzak, Larissa M., Melott, Adrian L., Medvedev, Mikhail V., Thomas, Brian C.
Gamma-Ray Bursts (GRBs) directed at Earth from within a few kpc may have damaged the biosphere, primarily though changes in atmospheric chemistry which admit greatly increased Solar UV. However, GRBs...
Comment on: Protecting Life in the Milky Way: Metals Keep the GRBs Away by Stanek et al (2006)
Stanek et al. (astro-ph/0604113) have noted that the four low-redshift long-duration gamma-ray bursts (LSB) observed to date all occurred in faint, metal-poor galaxies. Given this selection, they...
Do extragalactic cosmic rays induce cycles in fossil diversity? (2006)
Medvedev, Mikhail V., Melott, Adrian L.
Recent work has revealed a 62 (+/-) 3-million-year cycle in the fossil diversity in the past 542 My, however no plausible mechanism has been found. We propose that the cycle may be caused by...
Gamma-ray bursts and terrestrial planetary atmospheres (2006)
Thomas, Brian C., Melott, Adrian L.
We describe results of modeling the effects on Earth-like planets of long-duration gamma-ray bursts (GRBs) within a few kiloparsecs. A primary effect is generation of nitrogen oxide compounds which...
Thomas, Brian C., Melott, Adrian L., Jackman, Charles H., Laird, Claude M., Medvedev, Mikhail V., Stolarski, Richard S., ...
Gamma-Ray Bursts (GRBs) are likely to have made a number of significant impacts on the Earth during the last billion years. We have used a two-dimensional atmospheric model to investigate the effects...
Climatic and Biogeochemical Effects of a Galactic Gamma-Ray Burst (2005)
Melott, Adrian L., Thomas, Brian C., Hogan, Daniel P., Ejzak, Larissa M., Jackman, Charles H.
It is likely that one or more gamma-ray bursts within our galaxy have strongly irradiated the Earth in the last Gy. This produces significant atmospheric ionization and dissociation, resulting in...
Terrestrial Ozone Depletion Due to a Milky Way Gamma-Ray Burst (2004)
Thomas, Brian C., Jackman, Charles H., Melott, Adrian L., Laird, Claude M., Stolarski, Richard S., Gehrels, Neil, ...
Based on cosmological rates, it is probable that at least once in the last Gy the Earth has been irradiated by a gamma-ray burst in our Galaxy from within 2 kpc. Using a two-dimensional atmospheric...
Rahman, Nurur, Shandarin, Sergei F., Motl, Patrick M., Melott, Adrian L.
We have studied morphological evolution in clusters simulated in the adiabatic limit and with radiative cooling. Cluster morphology in the redshift range, $0 < z < 0.5$, is quantified by multiplicity...
Numerical study of the cosmological velocity field as a function of density (2003)
Dominguez, Alvaro, Melott, Adrian L.
We report on a new study of the velocity distribution in N-body simulations. We investigate the center-of-mass and internal kinetic energies of coarsening cells as a function of time, cell size and...
Quantifying the Bull's Eye Effect (2003)
Thomas, Brian C., Melott, Adrian L., Feldman, Hume A., Shandarin, Sergei F.
We have used N-body simulations to develop two independent methods to quantify redshift distortions known as the Bull's Eye effect (large scale infall plus small scale virial motion). This effect...
Optimal Moments for the Analysis of Peculiar Velocity Surveys II: Testing (2003)
Feldman, Hume A., Watkins, Richard, Melott, Adrian L., Chambers, Scott W.
Analyses of peculiar velocity surveys face several challenges, including low signal--to--noise in individual velocity measurements and the presence of small--scale, nonlinear flows. This is the...
Limits on thermal conduction in galaxy clusters (2003)
Medvedev, Mikhail V., Melott, Adrian L., Miller, Chris, Horner, Donald
We have calculated lower limits for the global effective thermal conductivity in a sample of 165 Abell clusters. We assumed that cluster X-ray luminosity is compensated by a conductive heat flux...
Optimal Moments for the Analysis of Peculiar Velocity Surveys (2001)
Watkins, Richard, Feldman, Hume A., Chambers, Scott W., Gorman, Patrick, Melott, Adrian L.
We present a new method for the analysis of peculiar velocity surveys which removes contributions to velocities from small scale, nonlinear velocity modes while retaining information about large...
Recent Dynamical Relaxation of Galaxy Clusters: Evidence for a Low-$\Omega_m$ Universe (2001)
Melott, Adrian L., Chambers, Scott W., Miller, Christopher J.
We argue that there has been substantial evolution in the ellipticity of rich galaxy clusters between 0 < z < 0.1, and suggest that this is additional evidence for a low matter-density Universe.
The Nearest Neighbor Alignment of Cluster X-ray Isophotes (2001)
Chambers, Scott W., Melott, Adrian L., Miller, Christopher J.
We examine the orientations of rich galaxy cluster X-ray isophotes with respect to their rich nearest neighbors using existing samples of Abell cluster position angles measured from {\it Einstein}...
The Size and Shape of Voids in Three-Dimensional Galaxy Surveys (2000)
Schmidt, Jason D., Ryden, Barbara S., Melott, Adrian L.
The sizes and shapes of voids in a galaxy survey depend not only on the physics of structure formation, but also on the sampling density of the survey and on the algorithm used to define voids. Using...
Einstein Cluster Alignments Revisited (2000)
Chambers, Scott W., Melott, Adrian L., Miller, Christopher J.
We have examined whether the major axes of rich galaxy clusters tend to point toward their nearest neighboring cluster. We have used the data of Ulmer, McMillan, and Kowalski, who used position...
Wavelength Doesn't Matter: Optical vs. X-ray Luminosities of Galaxy Clusters (1999)
Miller, Christopher J., Melott, Adrian L., Nichol, Robert C.
We examine the relationship between the total X-ray and optical luminosities of groups and clusters of galaxies taken from various samples in the literature. The clusters and groups were drawn from...
Redshift Surveys and the Value of Omega (1999)
Feldman, Hume A., Melott, Adrian L.
We compare the statistical properties of structures normal and transverse to the line of sight which appear in observational data from redshift surveys. We present a statistic which can quantify this...
Massive Cooling Flow Clusters Inhabit Crowded Environments (1999)
Loken, Chris, Melott, Adrian L., Miller, Christopher J.
With the availability of large-scale redshift survey data, it is now becoming possible to explore correlations between large-scale structure and the properties and morphologies of galaxy clusters. We...
Disentangling the Cosmic Web I: Morphology of Isodensity Contours (1999)
Schmalzing, Jens, Buchert, Thomas, Melott, Adrian L., Sahni, Varun, Sathyaprakash, B. S., Shandarin, Sergei F.
We apply Minkowski functionals and various derived measures to decipher the morphological properties of large-scale structure seen in simulations of gravitational evolution. Minkowski functionals of...
Munshi, Dipak, Coles, Peter, Melott, Adrian L.
We develop a diagrammatic technique to represent the multi-point cumulative probability density function (CPDF) of mass fluctuations in terms of the statistical properties of individual collapsed...
Munshi, Dipak, Coles, Peter, Melott, Adrian L.
The highly nonlinear regime of gravitational clustering is characterized by the presence of scale-invariant form of many-body correlation functions. Useful insights can be obtained by investigating...
Munshi, Dipak, Coles, Peter, Melott, Adrian L.
The highly nonlinear regime of gravitational clustering is characterized by the presence of scale-invariant form of many-body correlation functions. Useful insights can be obtained by investigating...
Generalised Cumulant Correlators and Hierarchical Clustering (1998)
Munshi, Dipak, Melott, Adrian L., Coles, Peter
The cumulant correlators, $C_{pq}$, are statistical quantities that generalise the better-known $S_p$ parameters; the former are obtained from the two-point probability distribution function of the...
The Bull's-Eye Effect as a Probe of $\Omega$ (1998)
Melott, Adrian L., Coles, Peter, Feldman, Hume A., Wilhite, Brian
We compare the statistical properties of structures normal and transverse to the line of sight which appear in theoretical N-body simulations of structure formation, and seem also to be present in...
Cumulant Correlators in 2D and 3D Scale Free Simulations (1998)
Munshi, Dipak, Melott, Adrian L.
Shape dependence of higher order correlations introduces complication in direct determination of these quantities. For this reason theoretical and observational progress has been restricted in...
Dark Matter, Discreteness and Collision Error in Cosmological N-Body Simulations (1997)
Splinter, Randall J., Melott, Adrian L., Shandarin, Sergei F.
We report on a series of tests of agreement between three types of N-body simulations: PM, P$^3$M, and Tree codes. We find good agreement in both the individual and the statistical properties only on...
Fundamental Discreteness Limitations of Cosmological N-Body Clustering Simulations (1997)
Splinter, Randall J., Melott, Adrian L., Shandarin, Sergei F., Suto, Yasushi
We explore some of the effects that discreteness and two-body scattering may have on N-body simulations with ``realistic'' cosmological initial conditions. We use an identical subset of particles...
Protogeros, Zacharias A. M., Melott, Adrian L., Scherrer, Robert J.
We test tree-level perturbation theory for Gaussian initial conditions with power spectra $P(k)\propto k^n$ by comparing the probability distribution function (PDF) for the density predicted by the...
The Bull's-Eye Effect: Are Galaxy Walls Observationally Enhanced? (1996)
Praton, Elizabeth. A., Melott, Adrian L., McKee, Margaret Q.
We investigate a distortion in redshift-space which causes galaxies to appear to lie in walls concentric about the observer, forming a rough bull's-eye pattern. We simulate what an observer would see...
The Ellipticity and Orientation of Clusters of Galaxies from N-Body Experiments (1996)
Splinter, Randall J., Melott, Adrian L., Linn, Angela, Buck, Charles, Tinker, Jeremy
In this study we use simulations of 128$^3$ particles to study the ellipticity and orientation of clusters of galaxies in N-body simulations of differing power-law initial spectra (P(k) \propto k^n...
EVOLUTION OF THE POTENTIAL IN COSMOLOGICAL GRAVITATIONAL CLUSTERING (1995)
Melott, Adrian L., Sathyaprakash, B. S., Sahni, Varun
The potential is a constant to linear order in cosmological gravitational clustering. In this Letter we present results of testing the conjecture, proposed by Pauls and Melott (1995), that the effect...
Pauls, Jennifer L., Melott, Adrian L.
To explain the rich structure of voids, clusters, sheets, and filaments apparent in the Universe, we present evidence for the convergence of the two classic approaches to gravitational clustering,...
Evolution of the Potential in Cosmological Gravitational Clustering (1994)
Melott, Adrian L., Pauls, Jennifer L.
In recent years there has been a developing realization that the interesting large--scale structure of voids, ``pancakes", and filaments in the Universe is a consequence of the efficacy of an...
Fry, J. N., Melott, Adrian L., Shandarin, Sergei F.
We examine the effect of a threshold bias on the power spectrum and the bispectrum in an ensemble of numerical simulations (Gaussian initial perturbations with power law spectra P(k) \sim k^n, n=+1,...
Comparison of Dynamical Approximation Schemes for Non-Linear Gravitational Clustering (1994)
I report on controlled comparison of gravitational approximation schemes linear/lognormal/adhesion/frozen-flow/Zel'dovich(ZA) and ZA's second--order generalization. In the last two cases we also...
Decaying Neutrinos in Galaxy Clusters (1993)
Melott, Adrian L., Splinter, Randall J., Persic, Massimo, Salucci, Paolo
Davidsen et al. (1991) have argued that the failure to detect uv photons from the dark matter DM) in cluster A665 excludes the decaying neutrino hypothesis. Sciama et al. (1993) argued that because...
Testing the Frozen-Flow Approximation (1993)
Melott, Adrian L., Lucchin, Francesco, Matarrese, Sabino, Moscardini, Lauro
We investigate the accuracy of the frozen--flow approximation (FFA), recently proposed by Matarrese \etal (1992), for following the nonlinear evolution of cosmological density fluctuations under...
Lieberman, Bruce S., Melott, Adrian L.
We re-examine the evidence for a 62 million year (Myr) periodicity in biodiversity throughout the Phanerozoic history of animal life reported by [1], as well as related questions of periodicity in...
Long-Term Cycles in the History of Life: Periodic Biodiversity in the Paleobiology Database
Time series analysis of fossil biodiversity of marine invertebrates in the Paleobiology Database (PBDB) shows a significant periodicity at approximately 63 My, in agreement with previous analyses...