A bias in optical observations of high redshift luminous infrared galaxies

We present evidence for the dramatically different morphology between the rest frame UV and 7micron mid-IR emission of VV114 and Arp299, two nearby (z~0) violently interacting infrared luminous galaxies (LIRGs). Nearly all LIRGs are interacting systems and it is currently accepted that they dominate the IR emission at z>1. Luminous IR galaxies located at z=1-2 could easily be detected as unresolved sources in deep optical/near-IR ground based surveys, as well as in upcoming 24micron surveys with the Space Infrared Telescope Facility. We demonstrate that the spatial resolution of these surveys will result in blending of the emission from unresolved interacting components. An increased scatter will thus be introduced in the observed optical to mid-IR colors of these galaxies, leading to a systematic underestimation of their dust content.Comment: To appear in the Astrophysical Journal Letters (4 pages 1 figure

The Distribution of Redshifts in New Samples of Quasi-stellar Objects

Two new samples of QSOs have been constructed from recent surveys to test the hypothesis that the redshift distribution of bright QSOs is periodic in $\log(1+z)$. The first of these comprises 57 different redshifts among all known close pairs or multiple QSOs, with image separations $\leq$ 10\arcsec, and the second consists of 39 QSOs selected through their X-ray emission and their proximity to bright comparatively nearby active galaxies. The redshift distributions of the samples are found to exhibit distinct peaks with a periodic separation of $\sim 0.089$ in $\log(1+z)$ identical to that claimed in earlier samples but now extended out to higher redshift peaks $z = 2.63, 3.45$ and 4.47, predicted by the formula but never seen before. The periodicity is also seen in a third sample, the 78 QSOs of the 3C and 3CR catalogues. It is present in these three datasets at an overall significance level $10^{-5}$ - $10^{-6}$, and appears not to be explicable by spectroscopic or similar selection effects. Possible interpretations are briefly discussed.Comment: submitted for publication in the Astronomical Journal, 15 figure

Blue Straggler Stars: Early Observations that Failed to Solve the Problem

In this chapter, I describe early ideas on blue stragglers, and various observations (some published, some not) that promised but failed to resolve the question of their origin. I review the data and ideas that were circulating from Allan Sandage's original discovery in 1953 of "anomalous blue stars" in the globular cluster M3, up until about 1992, when what seems to have been the only previous meeting devoted to Blue Straggler Stars (BSSs) was held at the Space Telescope Science Institute.Comment: Chapter 2, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe

Intrinsic spin Hall torque in a moire Chern magnet

In spin torque magnetic memories, electrically actuated spin currents are used to switch a magnetic bit. Typically, these require a multilayer geometry including both a free ferromagnetic layer and a second layer providing spin injection. For example, spin may be injected by a nonmagnetic layer exhibiting a large spin Hall effect, a phenomenon known as spin-orbit torque. Here, we demonstrate a spin-orbit torque magnetic bit in a single two-dimensional system with intrinsic magnetism and strong Berry curvature. We study AB-stacked MoTe2/WSe2, which hosts a magnetic Chern insulator at a carrier density of one hole per moire superlattice site. We observe hysteretic switching of the resistivity as a function of applied current. Magnetic imaging using a superconducting quantum interference device reveals that current switches correspond to reversals of individual magnetic domains. The real space pattern of domain reversals aligns precisely with spin accumulation measured near the high-Berry curvature Hubbard band edges. This suggests that intrinsic spin- or valley-Hall torques drive the observed current-driven magnetic switching in both MoTe2/WSe2 and other moire materials. The switching current density of 10^3 Amps per square centimeter is significantly less than reported in other platforms paving the way for efficient control of magnetic order

Inner Polar Rings and Disks: Observed Properties

A list of galaxies with inner regions revealing polar (or strongly inclined to the main galactic plane) disks and rings is compiled from the literature data. The list contains 47 galaxies of all morphological types, from E to Irr. We consider the statistics of the parameters of polar structures known from observations. The radii of the majority of them do not exceed 1.5 kpc. The polar structures are equally common in barred and unbarred galaxies. At the same time, if a galaxy has a bar (or a triaxial bulge), this leads to the polar disk stabilization - its axis of rotation usually coincides with the major axis of the bar. More than two thirds of all considered galaxies reveal one or another sign of recent interaction or merging. This fact indicates a direct relation between the external environment and the presence of an inner polar structure.Comment: 12 pages, 3 figures, accepted to Astrophysical Bulletin. Minor changes and corrections are still possibl

Did VV~29 collide with a dark Dark-Matter halo?

Westerbork Radio Synthesis Telescope observation of the galaxy VV29=Arp188=UGC10214 shows that there are at least three distinct dynamical components whose kinematics can be traced in 21cm line emission. The system appears to be the result of a galaxy-galaxy interaction. We identify a sufficient number of dynamical elements containing baryons (stars and neutral gas) that there is no compelling reason to postulate the presence of an additional dark matter halo that is devoid of detectable baryons. The central galaxy VV29a is massive (V_rot = 330 km/s) and gas rich (M_HI} = 6x10^9 Msolar). The distinctive optical plume (VV29b), which extends eastward from the main galaxy, is also gas rich (M_HI = 3x10^9 Msolar) and has a very low gradient in line of sight velocity (<30 km/s) over 70kpc. On the western side, there is an HI feature of M_HI = 4x10^8 Msolar that participates strongly in orbital motion about the host in the same sense of rotation as the VV29a itself. A blue, less massive, gas-rich galaxy "VV29c" (M_HI = 9x10^8 Msolar) appears clearly in the HI maps as an 170 km/s wide spectral feature, seen in projection against or, more likely, behind the west side of the host disk. Its high recessional velocity is counter to the host rotation direction. The optical images of Trentham et al (2001) show signs of this blue dwarf against the redder VV29a disk. The companion galaxy CGCG27-021=MGC09-26-54 (at projected distance 115 kpc) is not detected in 21cm line emission (M_HI<10^9Msolar).Comment: 7 pages, 13 figures, accepted for publication in Astronomy and Astrophysic

Analytic Metaphysics versus Naturalized Metaphysics: The Relevance of Applied Ontology

The relevance of analytic metaphysics has come under criticism: Ladyman & Ross, for instance, have suggested do discontinue the field. French & McKenzie have argued in defense of analytic metaphysics that it develops tools that could turn out to be useful for philosophy of physics. In this article, we show first that this heuristic defense of metaphysics can be extended to the scientific field of applied ontology, which uses constructs from analytic metaphysics. Second, we elaborate on a parallel by French & McKenzie between mathematics and metaphysics to show that the whole field of analytic metaphysics, being useful not only for philosophy but also for science, should continue to exist as a largely autonomous field

Neutrino physics and the mirror world: how exact parity symmetry explains the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiment

Evidence for $\bar \nu_{\mu} \rightarrow \bar \nu_e$ oscillations has been reported at LAMPF using the LSND detector. Further evidence for neutrino mixing comes from the solar neutrino deficit and the atmospheric neutrino anomaly. All of these anomalies require new physics. We show that all of these anomalies can be explained if the standard model is enlarged so that an unbroken parity symmetry can be defined. This explanation holds independently of the actual model for neutrino masses. Thus, we argue that parity symmetry is not only a beautiful candidate for a symmetry beyond the standard model, but it can also explain the known neutrino physics anomalies.Comment: 27 pages, LaTeX, no figures, additional discussion on big bang nucleosynthesis, some additional references, to appear in Phys. Rev.

The Beginning and Evolution of the Universe

We review the current standard model for the evolution of the Universe from an early inflationary epoch to the complex hierarchy of structure seen today. We summarize and provide key references for the following topics: observations of the expanding Universe; the hot early Universe and nucleosynthesis; theory and observations of the cosmic microwave background; Big Bang cosmology; inflation; dark matter and dark energy; theory of structure formation; the cold dark matter model; galaxy formation; cosmological simulations; observations of galaxies, clusters, and quasars; statistical measures of large-scale structure; and measurement of cosmological parameters. We conclude with discussion of some open questions in cosmology. This review is designed to provide a graduate student or other new worker in the field an introduction to the cosmological literature.Comment: 69 pages. Invited review article for Publications of the Astronomical Society of the Pacific. Supplementary references, tables, and more concise PDF file at http://www.physics.drexel.edu/univers

Galaxy Collisions - Dawn of a New Era

The study of colliding galaxies has progressed rapidly in the last few years, driven by observations with powerful new ground and space-based instruments. These instruments have used for detailed studies of specific nearby systems, statistical studies of large samples of relatively nearby systems, and increasingly large samples of high redshift systems. Following a brief summary of the historical context, this review attempts to integrate these studies to address the following key issues. What role do collisions play in galaxy evolution, and how can recently discovered processes like downsizing resolve some apparently contradictory results of high redshift studies? What is the role of environment in galaxy collisions? How is star formation and nuclear activity orchestrated by the large scale dynamics, before and during merger? Are novel modes of star formation involved? What are we to make of the association of ultraluminous X-ray sources with colliding galaxies? To what do degree do mergers and feedback trigger long-term secular effects? How far can we push the archaeology of individual systems to determine the nature of precursor systems and the precise effect of the interaction? Tentative answers to many of these questions have been suggested, and the prospects for answering most of them in the next few decades are good.Comment: 44 pages, 9 figures, review article in press for Astrophysics Update Vol.