367 research outputs found
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 sigma model with anomalous
magnetic moment interaction in dimensions is exactly integrable for
static, self-dual field configurations. The matter fields are exactly
equivalent to those of the usual ungauged nonlinear 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 dimensions is also presented where these
purely magnetic vortices can be realized.Comment: A discussion on case has been made. New references have been
added. To appear in Physics Letters B. RevTeX, 13 pages, no figur
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 and co-moving Mpc volumes resolve
haloes down to the atomic cooling limit and model the inter-stellar medium with
better than 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
percent ionized by volume at , while without them our
volumes fail to reionize by . 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 percent, about 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
Anyonic Bogomol'nyi Solitons in a Gauged O(3) Sigma Model
We introduce the self-dual abelian gauged 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]~158.6m
emission. Spatial and spectral offsets between [CII]~158.6m and
[OIII]~88.33m 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]~158.6m deficits. Our galaxies are consistent with the nebular line
properties of observed 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 and [OII]~3727 luminosity and galaxy SFR apply up to , as
do the local relations between certain strong line diagnostics (R23 and
[OIII]~5007/H) 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 âanaloguesâ 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 R23âO32 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 O32âfesc 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 [SâII]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the SâII BaldwinâPhillipsâTerlevich (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 [CâII]158 ÎŒm and [OâIII]88 ÎŒm 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
Population statistics of intermediate mass black holes in dwarf galaxies using the NewHorizon simulation
While it is well established that supermassive black holes (SMBHs) co-evolve
with their host galaxy, it is currently less clear how lower mass black holes,
so-called intermediate mass black holes (IMBHs), evolve within their dwarf
galaxy hosts. In this paper, we present results on the evolution of a large
sample of IMBHs from the NewHorizon simulation. We show that occupation
fractions of IMBHs in dwarf galaxies are at least 50 percent for galaxies with
stellar masses down to 1E6 Msun, but BH growth is very limited in dwarf
galaxies. In NewHorizon, IMBH growth is somewhat more efficient at high
redshift z = 3 but in general IMBH do not grow significantly until their host
galaxy leaves the dwarf regime. As a result, NewHorizon under-predicts observed
AGN luminosity function and AGN fractions. We show that the difficulties of
IMBH to remain attached to the centres of their host galaxies plays an
important role in limiting their mass growth, and that this dynamic evolution
away from galactic centres becomes stronger at lower redshift.Comment: 15 pages, submitted to MNRA
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 and . We
find that the simulated galaxies with high LyC escape fractions ()
often exhibit high O32 and populate the same regions of the R23-O32 plane as
LyC leakers. However, we show that viewing angle, metallicity, and
ionisation parameter can all impact where a galaxy resides on the O32- plane. Based on emission line diagnostics and how they correlate with
, lower-metallicity LyC leakers at appear to be good
analogues of reionization-era galaxies. In contrast, local [SII]-deficient
galaxies do not overlap with the simulated high-redshift LyC leakers on the
SII-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 IR and nebular emission lines. We show that our
model using only [CII] and [OIII] 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
MACS1149_JD1 at is the most likely galaxy to be actively contributing
to the reionization of the Universe
Tracing the sources of reionization in cosmological radiation hydrodynamics simulations
We use the photon flux and absorption tracer algorithm presented in Katz et
al.~2018, to characterise the contribution of haloes of different mass and
stars of different age and metallicity to the reionization of the Universe. We
employ a suite of cosmological multifrequency radiation hydrodynamics AMR
simulations that are carefully calibrated to reproduce a realistic reionization
history and galaxy properties at . In our simulations, haloes with
mass , stars with
metallicity , and stars with age
dominate reionization by both mass and
volume. We show that the sources that reionize most of the volume of the
Universe by are not necessarily the same sources that dominate the
meta-galactic UV background at the same redshift. We further show that in our
simulations, the contribution of each type of source to reionization is not
uniform across different gas phases. The IGM, CGM, filaments, ISM, and rarefied
supernova heated gas have all been photoionized by different classes of
sources. Collisional ionisation contributes at both the lowest and highest
densities. In the early stages of the formation of individual HII bubbles,
reionization proceeds with the formation of concentric shells of gas ionised by
different classes of sources, leading to large temperature variations as a
function of galacto-centric radius. The temperature structure of individual HII
bubbles may thus give insight into the star formation history of the galaxies
acting as the first ionising sources. Our explorative simulations highlight how
the complex nature of reionization can be better understood by using our photon
tracer algorithm
- âŠ