scholarly journals The escape fraction of ionizing photons during the Epoch of Reionization: observability with the Square Kilometre Array

2019 ◽  
Vol 487 (4) ◽  
pp. 5739-5752 ◽  
Author(s):  
Jacob Seiler ◽  
Anne Hutter ◽  
Manodeep Sinha ◽  
Darren Croton
Keyword(s):  
Power Spectrum ◽  
Galaxy Evolution ◽  
Optical Depth ◽  
Large Scale ◽  
Low Frequency ◽  
Integration Time ◽  
Square Kilometre Array ◽  
Exciting Opportunity ◽  
Functional Forms ◽  
The Impact

Abstract One of the most important parameters in characterizing the Epoch of Reionization, the escape fraction of ionizing photons, fesc, remains unconstrained both observationally and theoretically. With recent work highlighting the impact of galaxy-scale feedback on the instantaneous value of fesc, it is important to develop a model in which reionization is self-consistently coupled to galaxy evolution. In this work, we present such a model and explore how physically motivated functional forms of fesc affect the evolution of ionized hydrogen within the intergalactic medium. Using the 21 cm power spectrum evolution, we investigate the likelihood of observationally distinguishing between a constant fesc and other models that depend upon different forms of galaxy feedback. We find that changing the underlying connection between fesc and galaxy feedback drastically alters the large-scale 21 cm power. The upcoming Square Kilometre Array Low Frequency instrument possesses the sensitivity to differentiate between our models at a fixed optical depth, requiring only 200 h of integration time focused on redshifts z = 7.5–8.5. Generalizing these results to account for a varying optical depth will require multiple 800 h observations spanning redshifts z = 7–10. This presents an exciting opportunity to observationally constrain one of the most elusive parameters during the Epoch of Reionization.

scholarly journals Reaching small scales with low-frequency imaging: applications to the Dark Ages

2020 ◽  
Vol 379 (2188) ◽  
pp. 20190571 ◽  
Author(s):  
L. K. Morabito ◽  
J. Silk
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Initial Conditions ◽  
Low Frequency ◽  
Integration Time ◽  
Observational Constraints ◽  
The Moon ◽  
Microwave Background ◽  
Matter Power Spectrum ◽  
Density Perturbations

The initial conditions for the density perturbations in the early Universe, which dictate the large-scale structure and distribution of galaxies we see today, are set during inflation. Measurements of primordial non-Gaussianity are crucial for distinguishing between different inflationary models. Current measurements of the matter power spectrum from the cosmic microwave background only constrain this on scales up to k  ∼ 0.1 Mpc −1 . Reaching smaller angular scales (higher values of k ) can provide new constraints on non-Gaussianity. A powerful way to do this is by measuring the HI matter power spectrum at z ≳ 30 . In this paper, we investigate what values of k can be reached for the Low-Frequency Array (LOFAR), which can achieve ≲ 1″ resolution at approximately 50 MHz. Combining this with a technique to isolate the spectrally smooth foregrounds to a wedge in k ∥ – k ⊥ space, we demonstrate what values of k we can feasibly reach within observational constraints. We find that LOFAR is approximately five orders of magnitude away from the desired sensitivity, for 10 years of integration time. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.

scholarly journals The impact of AGN feedback on galaxy intrinsic alignments in the Horizon simulations

2020 ◽  
Vol 492 (3) ◽  
pp. 4268-4282 ◽  
Author(s):  
Adam Soussana ◽  
Nora Elisa Chisari ◽  
Sandrine Codis ◽  
Ricarda S Beckmann ◽  
Yohan Dubois ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Gravitational Lensing ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Three Dimensions ◽  
High Mass ◽  
Angular Momenta ◽  
The Galaxy ◽  
The Impact ◽  
The Universe

ABSTRACT The intrinsic correlations of galaxy shapes and orientations across the large-scale structure of the Universe are a known contaminant to weak gravitational lensing. They are known to be dependent on galaxy properties, such as their mass and morphologies. The complex interplay between alignments and the physical processes that drive galaxy evolution remains vastly unexplored. We assess the sensitivity of intrinsic alignments (shapes and angular momenta) to active galactic nuclei (AGN) feedback by comparing galaxy alignment in twin runs of the cosmological hydrodynamical Horizon simulation, which do and do not include AGN feedback, respectively. We measure intrinsic alignments in three dimensions and in projection at $z$ = 0 and $z$ = 1. We find that the projected alignment signal of all galaxies with resolved shapes with respect to the density field in the simulation is robust to AGN feedback, thus giving similar predictions for contamination to weak lensing. The relative alignment of galaxy shapes around galaxy positions is however significantly impacted, especially when considering high-mass ellipsoids. Using a sample of galaxy ‘twins’ across simulations, we determine that AGN changes both the galaxy selection and their actual alignments. Finally, we measure the alignments of angular momenta of galaxies with their nearest filament. Overall, these are more significant in the presence of AGN as a result of the higher abundance of massive pressure-supported galaxies.

scholarly journals Impact of relativistic effects on the primordial non-Gaussianity signature in the large-scale clustering of quasars

2020 ◽  
Vol 499 (2) ◽  
pp. 2598-2607
Author(s):  
Mike (Shengbo) Wang ◽  
Florian Beutler ◽  
David Bacon
Keyword(s):  
Dark Energy ◽  
Power Spectrum ◽  
Luminosity Function ◽  
Large Scale ◽  
Relativistic Effects ◽  
Redshift Range ◽  
Cosmological Background ◽  
Relativistic Corrections ◽  
The Galaxy ◽  
The Impact

ABSTRACT Relativistic effects in clustering observations have been shown to introduce scale-dependent corrections to the galaxy overdensity field on large scales, which may hamper the detection of primordial non-Gaussianity fNL through the scale-dependent halo bias. The amplitude of relativistic corrections depends not only on the cosmological background expansion, but also on the redshift evolution and sensitivity to the luminosity threshold of the tracer population being examined, as parametrized by the evolution bias be and magnification bias s. In this work, we propagate luminosity function measurements from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to be and s for the quasar (QSO) sample, and thereby derive constraints on relativistic corrections to its power spectrum multipoles. Although one could mitigate the impact on the fNL signature by adjusting the redshift range or the luminosity threshold of the tracer sample being considered, we suggest that, for future surveys probing large cosmic volumes, relativistic corrections should be forward modelled from the tracer luminosity function including its uncertainties. This will be important to quasar clustering measurements on scales $k \sim 10^{-3}\, h\, {\rm Mpc}^{-1}$ in upcoming surveys such as the Dark Energy Spectroscopic Instrument (DESI), where relativistic corrections can overwhelm the expected fNL signature at low redshifts z ≲ 1 and become comparable to fNL ≃ 1 in the power spectrum quadrupole at redshifts z ≳ 2.5.

scholarly journals Estimates for the impact of ultraviolet background fluctuations on galaxy clustering measurements

2019 ◽  
Vol 485 (4) ◽  
pp. 5059-5072 ◽  
Author(s):  
Phoebe Upton Sanderbeck ◽  
Vid Iršič ◽  
Matthew McQuinn ◽  
Avery Meiksin
Keyword(s):  
Power Spectrum ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Galaxy Surveys ◽  
Intensity Mapping ◽  
Redshift Galaxy ◽  
Halo Gas ◽  
The Cost ◽  
The Impact

ABSTRACT Spatial fluctuations in ultraviolet backgrounds can subtly modulate the distribution of extragalactic sources, a potential signal and systematic for large-scale structure surveys. While this modulation has been shown to be significant for 3D Ly α forest surveys, its relevance for other large-scale structure probes has been hardly explored, despite being the only astrophysical process that likely can affect clustering measurements on the scales of ≳Mpc. We estimate that the background fluctuations, modulating the amount of H i, have a fractional effect of (0.03–0.3) × (k/[10−2 Mpc−1])−1 on the power spectrum of 21 cm intensity maps at z = 1–3. We find a smaller effect for H α and Ly α intensity mapping surveys of (0.001–0.1) × (k/[10−2 Mpc−1])−1 and even smaller effect for more traditional surveys that correlate the positions of individual H α or Ly α emitters. We also estimate the effect of backgrounds on low-redshift galaxy surveys in general based on a simple model in which background fluctuations modulate the rate halo gas cools, modulating star formation: We estimate a maximum fractional effect on the power of ∼0.01 (k/[10−2 Mpc−1])−1 at z = 1. We compare sizes of these imprints to cosmological parameter benchmarks for the next generation of redshift surveys: We find that ionizing backgrounds could result in a bias on the squeezed triangle non-Gaussianity parameter fNL that can be larger than unity for power spectrum measurements with a SPHEREx-like galaxy survey, and typical values of intensity bias. Marginalizing over a shape of the form k−1PL, where PL is the linear matter power spectrum, removes much of this bias at the cost of ${\approx } 40{{\ \rm per\ cent}}$ larger statistical errors.

scholarly journals Magnetism Science with the Square Kilometre Array

Galaxies ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 53
Author(s):  
George Heald ◽  
Sui Mao ◽  
Valentina Vacca ◽  
Takuya Akahori ◽  
Ancor Damas-Segovia ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Dark Matter Annihilation ◽  
New Techniques ◽  
Square Kilometre Array ◽  
New Radio ◽  
Recent Developments ◽  
Using Data ◽  
The Impact

The Square Kilometre Array (SKA) will answer fundamental questions about the origin, evolution, properties, and influence of magnetic fields throughout the Universe. Magnetic fields can illuminate and influence phenomena as diverse as star formation, galactic dynamics, fast radio bursts, active galactic nuclei, large-scale structure, and dark matter annihilation. Preparations for the SKA are swiftly continuing worldwide, and the community is making tremendous observational progress in the field of cosmic magnetism using data from a powerful international suite of SKA pathfinder and precursor telescopes. In this contribution, we revisit community plans for magnetism research using the SKA, in light of these recent rapid developments. We focus in particular on the impact that new radio telescope instrumentation is generating, thus advancing our understanding of key SKA magnetism science areas, as well as the new techniques that are required for processing and interpreting the data. We discuss these recent developments in the context of the ultimate scientific goals for the SKA era.

scholarly journals Understanding diaschisis models of attention dysfunction with rTMS

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Javier O. Garcia ◽  
Lorella Battelli ◽  
Ela Plow ◽  
Zaira Cattaneo ◽  
Jean Vettel ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Brain Stimulation ◽  
Large Scale ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Low Frequency ◽  
Preliminary Evidence ◽  
Noninvasive Brain Stimulation ◽  
Induced Changes ◽  
Attention Dysfunction ◽  
The Impact

Abstract Visual attentive tracking requires a balance of excitation and inhibition across large-scale frontoparietal cortical networks. Using methods borrowed from network science, we characterize the induced changes in network dynamics following low frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) as an inhibitory noninvasive brain stimulation protocol delivered over the intraparietal sulcus. When participants engaged in visual tracking, we observed a highly stable network configuration of six distinct communities, each with characteristic properties in node dynamics. Stimulation to parietal cortex had no significant impact on the dynamics of the parietal community, which already exhibited increased flexibility and promiscuity relative to the other communities. The impact of rTMS, however, was apparent distal from the stimulation site in lateral prefrontal cortex. rTMS temporarily induced stronger allegiance within and between nodal motifs (increased recruitment and integration) in dorsolateral and ventrolateral prefrontal cortex, which returned to baseline levels within 15 min. These findings illustrate the distributed nature by which inhibitory rTMS perturbs network communities and is preliminary evidence for downstream cortical interactions when using noninvasive brain stimulation for behavioral augmentations.

scholarly journals Mixed dark matter: matter power spectrum and halo mass function

2021 ◽  
Vol 2021 (12) ◽  
pp. 044
Author(s):  
G. Parimbelli ◽  
G. Scelfo ◽  
S.K. Giri ◽  
A. Schneider ◽  
M. Archidiacono ◽  
...  
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Mass Function ◽  
Large Set ◽  
Cluster Number ◽  
Matter Power Spectrum ◽  
Wide Range ◽  
The Impact

Abstract We investigate and quantify the impact of mixed (cold and warm) dark matter models on large-scale structure observables. In this scenario, dark matter comes in two phases, a cold one (CDM) and a warm one (WDM): the presence of the latter causes a suppression in the matter power spectrum which is allowed by current constraints and may be detected in present-day and upcoming surveys. We run a large set of N-body simulations in order to build an efficient and accurate emulator to predict the aforementioned suppression with percent precision over a wide range of values for the WDM mass, Mwdm, and its fraction with respect to the totality of dark matter, fwdm. The suppression in the matter power spectrum is found to be independent of changes in the cosmological parameters at the 2% level for k≲ 10 h/Mpc and z≤ 3.5. In the same ranges, by applying a baryonification procedure on both ΛCDM and CWDM simulations to account for the effect of feedback, we find a similar level of agreement between the two scenarios. We examine the impact that such suppression has on weak lensing and angular galaxy clustering power spectra. Finally, we discuss the impact of mixed dark matter on the shape of the halo mass function and which analytical prescription yields the best agreement with simulations. We provide the reader with an application to galaxy cluster number counts.

scholarly journals BUDHiES IV: Deep 21-cm neutral Hydrogen, optical, and UV imaging data of Abell 963 and Abell 2192 at z ≃ 0.2

2020 ◽  
Vol 496 (3) ◽  
pp. 3531-3552 ◽  
Author(s):  
A R Gogate ◽  
M A W Verheijen ◽  
B Z Deshev ◽  
J H van Gorkom ◽  
M Montero-Castaño ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Integration Time ◽  
Wide Field ◽  
Imaging Data ◽  
Isaac Newton ◽  
Detection Techniques ◽  
Density Maps ◽  
Line Imaging

ABSTRACT In this paper, we present data from the Blind Ultra-Deep H i Environmental Survey (BUDHiES), which is a blind 21-cm H i spectral line imaging survey undertaken with the Westerbork Synthesis Radio Telescope. Two volumes were surveyed, each with a single pointing and covering a redshift range of 0.164 < z < 0.224. Within these two volumes, this survey targeted the clusters Abell 963 and Abell 2192, which are dynamically different and offer unique environments to study the process of galaxy evolution within clusters. With an integration time of 117 × 12 h on Abell 963 and 72 × 12 h on Abell 2192, a total of 166 galaxies were detected and imaged in H i. While the clusters themselves occupy only 4 per cent of the 73 400 Mpc3 surveyed by BUDHiES, most of the volume consists of large-scale structures in which the clusters are embedded, including foreground and background overdensities and voids. We present the data processing and source detection techniques and counterpart identification based on a wide-field optical imaging survey using the Isaac Newton Telescope and deep ultraviolet (UV) Galaxy Evolution Explorer (GALEX) imaging. Finally, we present H i and optical catalogues of the detected sources as well as atlases of their global H i properties, which include integrated column density maps, position–velocity diagrams, global H i profiles, and optical and UV images of the H i sources.

scholarly journals The impact of Pacific Decadal Oscillation on springtime dust activity in Syria

2016 ◽  
Author(s):  
Bing Pu ◽  
Paul Ginoux
Keyword(s):  
Middle East ◽  
Optical Depth ◽  
North Africa ◽  
Pacific Decadal Oscillation ◽  
Large Scale ◽  
Arabian Peninsula ◽  
Dust Storms ◽  
Near Surface ◽  
Deep Blue ◽  
The Impact

Abstract. The increasing trend of aerosol optical depth in the Middle East and a recent severe dust storm in Syria have raised questions as whether dust storms will increase and promoted investigations on the dust activities driven by the natural climate variability underlying the ongoing human perturbations such as the Syrian civil war. This study examined the influences of the Pacific decadal oscillation (PDO) on dust activities in Syria using an innovative dust optical depth (DOD) dataset derived from Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue aerosol products. A significantly negative correlation is found between the Syrian DOD and the PDO in spring from 2003–2015. High DOD in spring is associated with lower geopotential height over the Middle East, Europe, and North Africa, accompanied by near surface anomalous westerly winds over the Mediterranean basin and southerly winds over the eastern Arabian Peninsula. These large-scale patterns promote the formation of the cyclones over the Middle East to trigger dust storms and also facilitate the transport of dust from North Africa, Iraq, and Saudi Arabian to Syria, where the transported dust dominates the seasonal mean DOD in spring. A negative PDO not only creates circulation anomalies favorable to high DOD in Syria but also suppresses precipitation in dust source regions over the eastern and southern Arabian Peninsula and northeastern Africa. On the daily scale, in addition to the favorable large-scale condition associated with a negative PDO, enhanced atmospheric instability in Syria associated with increased precipitation in Turkey and northern Syria is also critical for the development of strong springtime dust storms in Syria.

scholarly journals Multiscale Interactions in an Idealized Walker Circulation: Mean Circulation and Intraseasonal Variability

2014 ◽  
Vol 71 (3) ◽  
pp. 953-971 ◽  
Author(s):  
Joanna Slawinska ◽  
Olivier Pauluis ◽  
Andrew J. Majda ◽  
Wojciech W. Grabowski
Keyword(s):  
Large Scale ◽  
Intraseasonal Variability ◽  
Low Frequency ◽  
Walker Circulation ◽  
Extended Period ◽  
Active Phase ◽  
Low Frequency Oscillation ◽  
Convective Systems ◽  
Cloud Resolving Model ◽  
The Impact

Abstract A high-resolution cloud-resolving model (CRM) simulation is developed here for a two-dimensional Walker circulation over a planetary-scale domain of 40 000 km for an extended period of several hundred days. The Walker cell emerges as the time-averaged statistical steady state with a prescribed sinusoidal sea surface temperature (SST) pattern with a mean temperature of 301.15 K and a horizontal variation of 4 K. The circulation exhibits intraseasonal variability on a time scale of about 20 days with quasi-periodic intensification of the circulation and broadening of the convective regime. This variability is closely tied to synoptic-scale systems associated with expansion and contraction of the Walker circulation. An index for the low-frequency variability is developed using an empirical orthogonal function (EOF) analysis and by regressing various dynamic fields on this index. The low-frequency oscillation has four main stages: a suppressed stage with strengthened midlevel circulation, an intensification phase, an active phase with strong upper-level circulation, and a weakening phase. Various physical processes occurring at these stages are discussed as well as the impact of organized convective systems on the large-scale flow.

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