ABSTRACT The kinetic Sunyaev-Zel'dovich (kSZ) effect results from Thomson scattering by coherent flows in the reionized intergalactic medium. We present new results based on ray-tracing an 8 Gpc/h ...realization of reionization with resolution elements 2 Mpc/h (subtending ′ at z = 6) on a side to create a full-sky kSZ map. The realization includes, self-consistently, the effects of reionization on scales corresponding to multipoles . We separate the kSZ map into Doppler ( ), Ostriker-Vishniac ( ), patchy ( ), and third-order ( ) components, and compute explicitly all the auto- and cross-correlations (e.g., , , etc.) that contribute to the total power. We find a complex and nonmonotonic dependence on the duration of reionization at and evidence for a non-negligible (10%-30%) contribution from connected four-point correlations, , usually neglected in analytical models. We also investigate the cross-correlation of linear matter and large-scale kSZ temperature fluctuations, focusing on (1) cross-power spectra with biased tracers of the matter density and (2) cold spots from infall onto large, rare H ii regions centered on peaks in the matter distribution at redshifts that are a generic non-Gaussian feature of patchy reionization. Finally, we show that the reionization history can be reconstructed at 5 -10 significance by correlating full-sky 21 cm maps stacked in bins with with existing cosmic microwave background (CMB) temperature maps at , raising the prospects for probing reionization by correlating CMB and LSS measurements. The resulting kSZ maps have been made publicly available at www.cita.utoronto.ca/~malvarez/research/ksz-data/.
ABSTRACT We have investigated the evaporation of close-in exoplanets irradiated by ionizing photons. We find that the properties of the flow are controlled by the ratio of the recombination time to ...the flow timescale. When the recombination timescale is short compared to the flow timescale, the flow is in approximate local ionization equilibrium with a thin ionization front where the photon mean free path is short compared to the flow scale. In this "recombination-limited" flow the mass-loss scales roughly with the square root of the incident flux. When the recombination time is long compared to the flow timescale the ionization front becomes thick and encompasses the entire flow with the mass-loss rate scaling linearly with flux. If the planet's potential is deep, then the flow is approximately "energy-limited"; however, if the planet's potential is shallow, then we identify a new limiting mass-loss regime, which we term "photon-limited." In this scenario, the mass-loss rate is purely limited by the incoming flux of ionizing photons. We have developed a new numerical approach that takes into account the frequency dependence of the incoming ionizing spectrum and performed a large suite of 1D simulations to characterize UV driven mass-loss around low-mass planets. We find that the flow is "recombination-limited" at high fluxes but becomes "energy-limited" at low fluxes; however, the transition is broad occurring over several orders of magnitude in flux. Finally, we point out that the transitions between the different flow types do not occur at a single flux value but depend on the planet's properties, with higher-mass planets becoming "energy-limited" at lower fluxes.
One of the most important biological processes at the molecular level is the formation of protein-ligand complexes. Therefore, determining their structure and underlying key interactions is of ...paramount relevance and has direct applications in drug development. Because of its low cost relative to its experimental sibling, molecular dynamics (MD) simulations in the presence of different solvent probes mimicking specific types of interactions have been increasingly used to analyze protein binding sites and reveal protein-ligand interaction hot spots. However, a systematic comparison of different probes and their real predictive power from a quantitative and thermodynamic point of view is still missing. In the present work, we have performed MD simulations of 18 different proteins in pure water as well as water mixtures of ethanol, acetamide, acetonitrile and methylammonium acetate, leading to a total of 5.4 μs simulation time. For each system, we determined the corresponding solvent sites, defined as space regions adjacent to the protein surface where the probability of finding a probe atom is higher than that in the bulk solvent. Finally, we compared the identified solvent sites with 121 different protein-ligand complexes and used them to perform molecular docking and ligand binding free energy estimates. Our results show that combining solely water and ethanol sites allows sampling over 70% of all possible protein-ligand interactions, especially those that coincide with ligand-based pharmacophoric points. Most important, we also show how the solvent sites can be used to significantly improve ligand docking in terms of both accuracy and precision, and that accurate predictions of ligand binding free energies, along with relative ranking of ligand affinity, can be performed.
Abstract
The Abundance Matching Box for the Epoch of Reionization (AMBER) is a semi-numerical code for modeling the cosmic dawn. The new algorithm is not based on the excursion set formalism for ...reionization, but takes the novel approach of calculating the reionization-redshift field
z
re
(
x
)
assuming that hydrogen gas encountering higher radiation intensity are photoionized earlier. Redshift values are assigned while matching the abundance of ionized mass according to a given mass-weighted ionization fraction
x
¯
i
(
z
)
. The code has the unique advantage of allowing users to directly specify the reionization history through the redshift midpoint
z
mid
, duration Δ
z
, and asymmetry
A
z
input parameters. The reionization process is further controlled through the minimum halo mass
M
min
for galaxy formation and the radiation mean free path
l
mfp
for radiative transfer. We implement improved methods for constructing density, velocity, halo, and radiation fields, which are essential components for modeling reionization observables. We compare AMBER with two other semi-numerical methods and find that our code more accurately reproduces the results from radiation-hydrodynamic simulations. The parallelized code is over four orders of magnitude faster than radiative transfer simulations and will efficiently enable large-volume models, full-sky mock observations, and parameter-space studies. AMBER will be made publicly available to facilitate and transform studies of the Epoch of Reionization.
Abstract
As the signal-to-noise of Sunyaev–Zeldovich (SZ) cross-correlation measurements of galaxies improves our ability to infer properties about the circumgalactic medium (CGM), we will transition ...from being limited by statistical uncertainties to systematic uncertainties. Using thermodynamic profiles of the CGM created from the IllustrisTNG (The Next Generation) simulations we investigate the importance of specific choices in modeling the galaxy sample. These choices include different sample selections in the simulation (stellar versus halo mass, color selections) and different fitting models (matching by the shape of the mass distribution, inclusion of a two-halo term). We forward model a mock galaxy sample into projected SZ observable profiles and fit these profiles to a generalized Navarro–Frenk–White profile using forecasted errors of the upcoming Simons Observatory experiment. We test the number of free parameters in the fits and show that this is another modeling choice that yields different results. Finally, we show how different fitting models can reproduce parameters of a fiducial profile, and show that the addition of a two-halo term and matching by the mass distribution of the sample are extremely important modeling choices to consider.
Observations of the Ly alpha forest and of high-redshift galaxies at z ~ 6-10 imply that there were just enough photons to maintain the universe in an ionized state at z ~ 5-6, indicating a ..."photon-starved" end to reionization. The ionizing emissivity must have been larger at earlier times in order to yield the extended reionization history implied by the electron scattering optical depth constraint from Wilkinson Microwave Anisotropy Probe (WMAP). Here we address the possibility that a faint population of galaxies with host halo masses of ~10 super(8-9) M sub(middot in circle) dominated the ionizing photon budget at redshifts z > ~ 9, due to their much higher escape fractions. Such faint, early galaxies, would not have formed in ionized regions due to suppression by heating from the UV background, and would therefore not contribute to the ionizing background at z <, ~ 6, after reionization is complete. Our model matches: (1) the low escape fractions observed for high-redshift galaxies, (2) the WMAP constraint of tau sub(es) ~ 0.09, (3) the low values for the UVB at z < 6, and (4) the observed star formation rate density inferred from Lyman break galaxies. A top-heavy initial mass function from Pop III stars is not required in this scenario. We compare our model to recent ones in the literature that were forced to introduce an escape fraction that increases strongly toward high redshift and show that a similar evolution occurs naturally if low-mass galaxies possess high escape fractions.
Abstract
We forecast the number of galaxy clusters that can be detected via the thermal Sunyaev–Zel’dovich (tSZ) signals by future cosmic microwave background (CMB) experiments, primarily the wide ...area survey of the CMB-S4 experiment but also CMB-S4's smaller de-lensing survey and the proposed CMB-HD experiment. We predict that CMB-S4 will detect 75,000 clusters with its wide survey of
f
sky
= 50% and 14,000 clusters with its deep survey of
f
sky
= 3%. Of these, approximately 1350 clusters will be at
z
≥ 2, a regime that is difficult to probe by optical or X-ray surveys. We assume CMB-HD will survey the same sky as the S4-Wide, and find that CMB-HD will detect three times more overall and an order of magnitude more
z
≥ 2 clusters than CMB-S4. These results include galactic and extragalactic foregrounds along with atmospheric and instrumental noise. Using CMB-cluster lensing to calibrate the cluster tSZ–mass scaling relation, we combine cluster counts with primary CMB to obtain cosmological constraints for a two-parameter extension of the standard model (ΛCDM + ∑
m
ν
+
w
0
). In addition to constraining
σ
(
w
0
) to ≲1%, we find that both surveys can enable a ∼2.5–4.5
σ
detection of ∑
m
ν
, substantially strengthening CMB-only constraints. We also study the evolution of the intracluster medium by modeling the cluster virialization v(
z
) and find tight constraints from CMB-S4, with further factors of three to four improvement for CMB-HD.
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