Maxwell--Chern-Simons gauged non-relativistic O(3) model with self-dual vortices

A non-relativistic version of the 2+1 dimensional gauged Chern-Simons O(3) sigma model, augmented by a Maxwell term, is presented and shown to support topologically stable static self-dual vortices. Exactly like their counterparts of the ungauged model, these vortices are shown to exhibit Hall behaviour in their dynamics.Comment: 12 pages, LateX, to appear in Mod. Phys. Lett. 199

Exact Self-dual Soliton Solutions in a Gauged O(3) Sigma Model with Anomalous Magnetic Moment Interaction

It is shown that a gauged nonlinear $O(3)$ sigma model with anomalous magnetic moment interaction in $2+1$ dimensions is exactly integrable for static, self-dual field configurations. The matter fields are exactly equivalent to those of the usual ungauged nonlinear $O(3)$ sigma model. These static soliton solutions can be mapped into an Abelian purely magnetic vortex solutions through a suitable reduction of the non-Abelian gauge group. A relativistic Abelian model in $2+1$ dimensions is also presented where these purely magnetic vortices can be realized.Comment: A discussion on $CP^N$ case has been made. New references have been added. To appear in Physics Letters B. RevTeX, 13 pages, no figur

The energy and dynamics of trapped radiative feedback with stellar winds

In this paper, we explore the significant, non-linear impact that stellar winds have on H II regions. We perform a parameter study using three-dimensional radiative magnetohydrodynamic simulations of wind and ultraviolet radiation feedback from a 35 M⊙ star formed self-consistently in a turbulent, self-gravitating cloud, similar to the Orion Nebula (M42) and its main ionizing source θ1 Ori C. Stellar winds suppress early radiative feedback by trapping ionizing radiation in the shell around the wind bubble. Rapid breakouts of warm photoionized gas (‘champagne flows’) still occur if the star forms close to the edge of the cloud. The impact of wind bubbles can be enhanced if we detect and remove numerical overcooling caused by shocks crossing grid cells. However, the majority of the energy in the wind bubble is still lost to turbulent mixing between the wind bubble and the gas around it. These results begin to converge if the spatial resolution at the wind bubble interface is increased by refining the grid on pressure gradients. Wind bubbles form a thin chimney close to the star, which then expands outwards as an extended plume once the wind bubble breaks out of the dense core the star formed in, allowing them to expand faster than a spherical wind bubble. We also find wind bubbles mixing completely with the photoionized gas when the H II region breaks out of the cloud as a champagne flow, a process we term ‘hot champagne’

Understanding the escape of LyC and Lyα photons from turbulent clouds

Understanding the escape of Lyman continuum (LyC) and Lyman alpha (Lya) photons from molecular clouds is one of the keys to constraining the reionization history of the Universe and the evolution of galaxies at high redshift. Using a set of radiation-hydrodynamic simulations with adaptive mesh refinement, we investigate how photons propagate and escape from turbulent clouds with different masses, star formation efficiencies (SFEs), and metallicities, as well as with different models of stellar spectra and supernova feedback. We find that the escape fractions in both LyC and Lya are generally increasing with time if the cloud is efficiently dispersed by radiation and supernova feedback. When the total SFE is low (1% of the cloud mass), 0.1-5% of LyC photons leave the metal-poor cloud, whereas the fractions increase to 20-70% in clouds with a 10% SFE. LyC photons escape more efficiently if gas metallicity is lower, if the upper mass limit in the stellar initial mass function is higher, if binary interactions are allowed in the evolution of stars, or if additional strong radiation pressure, such as Lya pressure, is present. As a result, the number of escaping LyC photons can easily vary by a factor of $\sim4$ on cloud scales. The escape fractions of Lya photons are systemically higher (60-80%) than those of LyC photons despite large optical depths at line centre ($\tau_0\sim10^6-10^9$). Scattering of Lya photons is already significant on cloud scales, leading to double-peaked profiles with peak separations of $v_{\rm sep}\sim400\,{\rm km\,s^{-1}}$ during the initial stage of the cloud evolution, while it becomes narrower than $v_{\rm sep} \le 150 \, {\rm km\,s^{-1}}$ in the LyC bright phase. Comparisons with observations of low-redshift galaxies suggest that Lya photons require further interactions with neutral hydrogen to reproduce their velocity offset for a given LyC escape fraction

The SPHINX cosmological simulations of the first billion years: The impact of binary stars on reionization

We present the SPHINX suite of cosmological adaptive mesh refinement simulations, the first radiation-hydrodynamical simulations to simultaneously capture large-scale reionization and the escape of ionizing radiation from thousands of resolved galaxies. Our $5$ and $10$ co-moving Mpc volumes resolve haloes down to the atomic cooling limit and model the inter-stellar medium with better than $\approx10$ pc resolution. The project has numerous goals in improving our understanding of reionization and making predictions for future observations. In this first paper we study how the inclusion of binary stars in computing stellar luminosities impacts reionization, compared to a model that includes only single stars. Owing to the suppression of galaxy growth via strong feedback, our galaxies are in good agreement with observational estimates of the galaxy luminosity function. We find that binaries have a significant impact on the timing of reionization: with binaries, our boxes are $99.9$ percent ionized by volume at $z\approx 7$, while without them our volumes fail to reionize by $z=6$. These results are robust to changes in volume size, resolution, and feedback efficiency. The escape of ionizing radiation from individual galaxies varies strongly and frequently. On average, binaries lead to escape fractions of $\approx 7-10$ percent, about $3.5$ times higher than with single stars only. The higher escape fraction is a result of a shallower decline in ionizing luminosity with age, and is the primary reason for earlier reionization, although the higher integrated luminosity with binaries also plays a sub-dominant role

Interpreting ALMA Observations of the ISM During the Epoch of Reionisation

We present cosmological, radiation-hydrodynamics simulations of galaxy formation during the epoch of reionization in an effort towards modelling the interstellar medium (ISM) and interpreting Atacama Large Millimeter Array (ALMA) observations. Simulations with and without stellar radiation are compared at large (Mpc), intermediate (tens of kpc) and small (sub-kpc) scales. At large scales, the dense regions around galaxies reionize first before ultraviolet (UV) photons penetrate the voids; however, considerable amounts of neutral gas remain present within the haloes. The spatial distribution of neutral gas is highly dynamic and is anticorrelated with the presence of stars older than a few Myr. For our specific feedback implementation, most of the metals remain inside the virial radii of haloes, and they are proportionally distributed over the ionized and neutral media by mass. For our most massive galaxy with Mh ∼ 10$^{11}$ M⊙, the majority of the C ii and O i masses are associated with cold neutral clumps. N ii is more diffuse and arises in warmer gas, while O iii arises in hotter gas with a higher ionization parameter, produced by photoheating and supernovae. If smaller pockets of high-metallicity gas exist in the ISM, the emission from these ions may be observable by ALMA, while the low metallicity of the galaxy may cause these systems to fall below the local [C ii]–star formation rate relation. The presence of dust can cause spatial offsets between UV/Lyman α and [C ii] emissions, as suggested by the recent observations of Maiolino et al. [O iii] may be spatially offset from both of these components since it arises from a different part of density–temperature phase space.This work made considerable use of the open source analysis software PYNBODY (Pontzen et al. 2013). HK thanks Foundation Boustany, the Cambridge Overseas Trust and an Isaac Newton Studentship. Support by ERC Advanced Grant 320596 ‘The Emergence of Structure during the Epoch of reionization’ is gratefully acknowledged. DS acknowledges support by STFC and ERC Starting Grant 638707 ‘Black holes and their host galaxies: coevolution across cosmic time’. This work was performed using the DiRAC/Darwin Supercomputer hosted by the University of Cambridge High Performance Computing Service (http://www.hpc.cam.ac.uk/), provided by Dell Inc. using the Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council. This work used the DiRAC Complexity system, operated by the University of Leicester IT Services, which forms part of the STFC DiRAC HPC Facility (www.dirac.ac.uk). This equipment is funded by BIS National E-Infrastructure capital grant ST/K000373/1 and STFC DiRAC Operations grant ST/K0003259/1. DiRAC is part of the National E-Infrastructure. Furthermore, this work used the DiRAC Data Centric system at Durham University, operated by the Institute for Computational Cosmology on behalf of the STFR DiRAC HPC Facility (www.dirac.ac.uk). This equipment was funded by the BIS National E-infrastructure capital grant ST/K00042X/1, STFC capital grant ST/K00087X/1, DiRAC operations grant ST/K003267/1 and Durham University. Dirac is part of the National E-Infrastructure

Anyonic Bogomol'nyi Solitons in a Gauged O(3) Sigma Model

We introduce the self-dual abelian gauged $O(3)$ sigma models where the Maxwell and Chern-Simons terms constitute the kinetic terms for the gauge field. These models have quite rich structures and various limits. Our models are found to exhibit both symmetric and broken phases of the gauge group. We discuss the pure Chern-Simons limit in some detail and study rotationally symmetric solitons.Comment: 14 pages, 6 Postscript figures uuencoded, written in REVTe

Constraining stellar assembly and AGN feedback at the peak epoch of star formation

We study stellar assembly and feedback from active galactic nuclei (AGN) around the epoch of peak star formation (1<z<2), by comparing hydrodynamic simulations to rest-frame UV-optical galaxy colours from the Wide Field Camera 3 (WFC3) Early-Release Science (ERS) Programme. Our Adaptive Mesh Refinement simulations include metal-dependent radiative cooling, star formation, kinetic outflows due to supernova explosions, and feedback from supermassive black holes. Our model assumes that when gas accretes onto black holes, a fraction of the energy is used to form either thermal winds or sub-relativistic momentum-imparting collimated jets, depending on the accretion rate. We find that the predicted rest-frame UV-optical colours of galaxies in the model that includes AGN feedback is in broad agreement with the observed colours of the WFC3 ERS sample at 1<z<2. The predicted number of massive galaxies also matches well with observations in this redshift range. However, the massive galaxies are predicted to show higher levels of residual star formation activity than the observational estimates, suggesting the need for further suppression of star formation without significantly altering the stellar mass function. We discuss possible improvements, involving faster stellar assembly through enhanced star formation during galaxy mergers while star formation at the peak epoch is still modulated by the AGN feedback.Comment: 6 pages, 4 figures, accepted for publication in MNRAS Letter

Probing cosmic dawn with emission lines: predicting infrared and nebular line emission for ALMA and JWST

Infrared and nebular lines provide some of our best probes of the physics regulating the properties of the interstellar medium (ISM) at high-redshift. However, interpreting the physical conditions of high-redshift galaxies directly from emission lines remains complicated due to inhomogeneities in temperature, density, metallicity, ionisation parameter, and spectral hardness. We present a new suite of cosmological, radiation-hydrodynamics simulations, each centred on a massive Lyman-break galaxy that resolves such properties in an inhomogeneous ISM. Many of the simulated systems exhibit transient but well defined gaseous disks that appear as velocity gradients in [CII]~158.6$\mu$m emission. Spatial and spectral offsets between [CII]~158.6$\mu$m and [OIII]~88.33$\mu$m are common, but not ubiquitous, as each line probes a different phase of the ISM. These systems fall on the local [CII]-SFR relation, consistent with newer observations that question previously observed [CII]~158.6$\mu$m deficits. Our galaxies are consistent with the nebular line properties of observed $z\sim2-3$ galaxies and reproduce offsets on the BPT and mass-excitation diagrams compared to local galaxies due to higher star formation rate (SFR), excitation, and specific-SFR, as well as harder spectra from young, metal-poor binaries. We predict that local calibrations between H$\alpha$ and [OII]~3727$\AA$ luminosity and galaxy SFR apply up to $z>10$, as do the local relations between certain strong line diagnostics (R23 and [OIII]~5007$\AA$/H$\beta$) and galaxy metallicity. Our new simulations are well suited to interpret the observations of line emission from current (ALMA and HST) and upcoming facilities (JWST and ngVLA)

New Methods for Identifying Lyman Continuum Leakers and Reionization-Epoch Analogues

Identifying low-redshift galaxies that emit Lyman continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly ‘analogues’ of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at z ∼ 3 and z ∼ 0. We find that the simulated galaxies with high LyC escape fractions (fesc) often exhibit high O32 and populate the same regions of the R23–O32 plane as z ∼ 3 LyC leakers. However, we show that viewing angle, metallicity, and ionization parameter can all impact where a galaxy resides on the O32–fesc plane. Based on emission line diagnostics and how they correlate with fesc, lower metallicity LyC leakers at z ∼ 3 appear to be good analogues of reionization-era galaxies. In contrast, local [S II]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the S II Baldwin–Phillips–Terlevich (BPT) diagram; however, this diagnostic may still be useful for identifying leakers. We use our simulated galaxies to develop multiple new diagnostics to identify LyC leakers using infrared and nebular emission lines. We show that our model using only [C II]158 μm and [O III]88 μm can identify potential leakers from non-leakers from the local Dwarf Galaxy Survey. Finally, we apply this diagnostic to known high-redshift galaxies and find that MACS 1149_JD1 at z = 9.1 is the most likely galaxy to be actively contributing to the reionization of the Universe