https://users.monash.edu.au/~dprice/ndspmhd/price-spmhd.pdf

Smoothed particle hydrodynamics and magnetohydrodynamics

We review several current aspects of dark matter theory and experiment. We overview the present experimental status, which includes current bounds and recent claims and hints of a possible signal in a wide range of experiments: direct detection in underground laboratories, gamma-ray, cosmic ray, x-ray, neutrino telescopes, and the LHC. We briefly review several possible particle candidates for a weakly interactive massive particle (WIMP) and dark matter that have recently been considered in the literature. We pay particular attention to the lightest neutralino of supersymmetry as it remains the best motivated candidate for dark matter and also shows excellent detection prospects. Finally we briefly review some alternative scenarios that can considerably alter properties and prospects for the detection of dark matter obtained within the standard thermal WIMP paradigm.

WIMP dark matter candidates and searches—current status and future prospects

Numerical simulations have become a major tool for understanding galaxy formation and evolution. Over the decades the field has made significant progress. It is now possible to simulate the formation of individual galaxies and galaxy populations from well-defined initial conditions with realistic abundances and global properties. An essential component of the calculation is to correctly estimate the inflow to and outflow from forming galaxies because observations indicating low formation efficiency and strong circumgalactic presence of gas are persuasive. Energetic “feedback” from massive stars and accreting supermassive black holes—generally unresolved in cosmological simulations—plays a major role in driving galactic outflows, which have been shown to regulate many aspects of galaxy evolution. A surprisingly large variety of plausible subresolution models succeeds in this exercise. They capture the essential characteristics of the problem, i.e., outflows regulating galactic gas flows, but their predicti...

Theoretical Challenges in Galaxy Formation

Adaptive Optics is a prime example of how progress in observational astronomy can be driven by technological developments. At many observatories it is now considered to be part of a standard instrumentation suite, enabling ground-based telescopes to reach the diffraction limit and thus providing spatial resolution superior to that achievable from space with current or planned satellites. In this review we consider adaptive optics from the astrophysical perspective. We show that adaptive optics has led to important advances in our understanding of a multitude of astrophysical processes, and describe how the requirements from science applications are now driving the development of the next generation of novel adaptive optics techniques.

Adaptive Optics for Astronomy

This work was supported by ASI/INAF contract I/009/10/0 and INAF PRIN 2011, 2012 and 2014. MB acknowledges support from the FP7 Career Integration Grant “eEASy” (CIG 321913). LZ acknowledges support from ASI/INAF grant I/037/12/0. CF acknowledges funding from the European Union Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement No 664931. CC acknowledges funding from the European Union Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement No 664931 and support from Swiss National Science Foundation Grants PP00P2 138979 and PP00P2 166159. RM acknowledges the ERC Advanced Grant 695671 QUENCH and support from the Science and Technology Facilities Council (STFC).

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AGN wind scaling relations and the co-evolution of black holes and galaxies

We present a new high-resolution N-body/smoothed particle hydrodynamics simulation of an encounter of two gas-rich disk galaxies that closely matches the morphology and kinematics of the interacting Antennae galaxies (NGC 4038/39). The simulation includes radiative cooling, star formation, and feedback from Type II supernovae. The large-scale morphology and kinematics are determined by the internal structure and the orbit of the progenitor disks. The properties of the central region, in particular the starburst in the overlap region, only match the observations for a very short time interval (Δt ≈ 20 Myr) after the second encounter. This indicates that the Antennae galaxies are in a special phase only about 40 Myr after the second encounter and 50 Myr before their final collision. This is the only phase in the simulation when a gas-rich overlap region between the nuclei is forming accompanied by enhanced star formation. The star formation rate as well as the recent star formation history in the central region agree well with observational estimates. For the first time, this new model explains the distributed extra-nuclear star formation in the Antennae galaxies as a consequence of the recent second encounter. The proposed model predicts that the Antennae are in a later merger stage than the Mice (NGC 4676) and would therefore lose their first place in the classical Toomre sequence. (Less)

https://iopscience.iop.org/article/10.1088/2041-8205/715/2/L88/pdf

One moment in time—modeling star formation in the antennae

We present spatially resolved integral field spectroscopic K-band data at a resolution of 0.13 �� (60 pc) and interferometric CO(2–1) line observations of the prototypical merging system NGC 6240. Despite the clear rotational signature, the stellar kinematics in the two nuclei are dominated by dispersion. We use Jeans modelling to derive the masses and the mass-to-light ratios of the nuclei. Combining the luminosities with the spatially resolved Brγ equivalent width shows that only 1/ 3o f theK-band continuum from the nuclei is associated with the most recent star forming episode; and that less than 30% of the system’s bolometric luminosity and only 9% of its stellar mass is due to this starburst. The star formation properties, calculated from typical merger star formation histories, demonstrate the impact of different assumptions about the star formation history. The properties of the nuclei, and the existence of a prominent old stellar population, indicate that the nuclei are remnants of the progenitor galaxies’ bulges.

/pdf/ngc-6240-merger-induced-star-formation-and-gas-dynamics-4yxs4pxcri.pdf

NGC 6240: merger-induced star formation and gas dynamics

We present spatially resolved integral field spectroscopic K-band data at a resolution of 0.13 00 (60 pc) and interferometric CO(2-1) line observations of the prototypical merging system NGC 6240. Despite the clear rotational signature, the stellar kin ematics in the two nuclei are dominated by dispersion. We use Jeans modelling to derive the masses and the mass-to-light ratios of the nuclei. Combining the luminosities with the spatially resolved Brequivalent width shows that only 1/3 of the K-band continuum from the nuclei is associated with the most recent star forming episode; and that less than 30% of the system’s bolometric luminos ity and only 9% of its stellar mass is due to this starburst. The star forma tion properties, calculated from typical merger star forma tion histories, demonstrate the impact of different assumptions about the star formation history. The properties of the nuclei, and the existence of a prominent old stellar population, indicate that the nuclei are remnants of the progenitor galaxies’ bulges.

/pdf/ngc6240-merger-induced-star-formation-gas-dynamics-2t8qgvgpd7.pdf

NGC6240: Merger-Induced Star Formation & Gas Dynamics

We present self-consistent high-resolution simulations of NGC 4038/4039 (the "Antennae galaxies") including star formation, supernova feedback, and magnetic fields performed with the N-body/smoothed particle hydrodynamic (SPH) code , in which magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 10–9 to 10–4 G. At the time of the best match with the central region of the Antennae system, the magnetic field has been amplified by compression and shear flows to an equilibrium field value of ≈10 μG, independent of the initial seed field. These simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of regular magnetic fields between the cores and at the root of the southern tidal arm develop naturally in our simulations. This indicates that the simulations are capable of realistically following the evolution of the magnetic fields in a highly nonlinear environment. We also discuss the relevance of the amplification effect for present-day magnetic fields in the context of hierarchical structure formation.

http://iopscience.iop.org/article/10.1088/0004-637X/716/2/1438/pdf

Simulating magnetic fields in the Antennae galaxies

We re-examine the age distribution of star clusters in the Antennae in the context of N-body+hydrodynamical simulations of these interacting galaxies. All of the simulations that account for the observed morphology and other properties of the Antennae have star formation rates that vary relatively slowly with time, by factors of only 1.3-2.5 in the past 108 yr. In contrast, the observed age distribution of the clusters declines approximately as a power law, dN/d??? with ? = ?1.0, for ages 106 yr ? 109 yr. These two facts can only be reconciled if the clusters are disrupted progressively for at least ~108 yr and possibly ~109 yr. When we combine the simulated formation rates with a power-law model, f surv??, for the fraction of clusters that survive to each age ?, we match the observed age distribution with exponents in the range ?0.9 ? ?0.6 (with a slightly different ? for each simulation). The similarity between ? and ? indicates that dN/d? is shaped mainly by the disruption of clusters rather than variations in their formation rate. Thus, the situation in the interacting Antennae resembles that in relatively quiescent galaxies such as the Milky Way and the Magellanic Clouds.

http://iopscience.iop.org/article/10.1088/0004-637X/734/1/11/pdf

Simon J. Karl

Papers

One moment in time—modeling star formation in the antennae

NGC 6240: merger-induced star formation and gas dynamics

NGC6240: Merger-Induced Star Formation & Gas Dynamics

Simulating magnetic fields in the Antennae galaxies

Disruption of Star Clusters in the Interacting Antennae Galaxies