scholarly journals Inferring the properties of the sources of reionization using the morphological spectra of the ionized regions

2021 ◽  
Vol 502 (2) ◽  
pp. 1816-1842
Author(s):  
Simon Gazagnes ◽  
Léon V E Koopmans ◽  
Michael H F Wilkinson
Keyword(s):  
Power Spectrum ◽  
High Redshift ◽  
Monte Carlo Analysis ◽  
Analysis Tool ◽  
Physical Processes ◽  
Morphological Pattern ◽  
Number Count ◽  
Independent Information ◽  
Square Kilometer Array ◽  
Do So

ABSTRACT High-redshift 21-cm observations will provide crucial insights into the physical processes of the Epoch of Reionization. Next-generation interferometers such as the Square Kilometer Array will have enough sensitivity to directly image the 21-cm fluctuations and trace the evolution of the ionizing fronts. In this work, we develop an inferential approach to recover the sources and IGM properties of the process of reionization using the number and, in particular, the morphological pattern spectra of the ionized regions extracted from realistic mock observations. To do so, we extend the Markov Chain Monte Carlo analysis tool 21cmmc by including these 21-cm tomographic statistics and compare this method to only using the power spectrum. We demonstrate that the evolution of the number-count and morphology of the ionized regions as a function of redshift provides independent information to disentangle multiple reionization scenarios because it probes the average ionizing budget per baryon. Although less precise, we find that constraints inferred using 21-cm tomographic statistics are more robust to the presence of contaminants such as foreground residuals. This work highlights that combining power spectrum and tomographic analyses more accurately recovers the astrophysics of reionization.

scholarly journals Modeling dust in a universe of galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 44-54
Author(s):  
Desika Narayanan ◽  
Qi Li ◽  
Romeel Davé ◽  
Charlie Conroy ◽  
Benjamin D. Johnson ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
State Of The Art ◽  
High Redshift ◽  
Mass Function ◽  
Physical Processes ◽  
Dust Mass

AbstractIn this invited talk, we discuss the physics of the lifecycle of dust in the context of galaxy formation simulations. After outlining the basic physical processes, we apply algorithms for the formation, growth, and destruction of dust in the ISM to a state-of-the-art cosmological simulation to develop a model for the evolution of the dust to gas and dust to metals ratios in galaxies. We show that while modern simulations are able to match the observed dust mass function at redshift z = 0, most models underpredict the observed mass function at high-redshift (z = 2). We then show the power of these techniques by expanding our model to include a spectrum of dust sizes, and make initial predictions for extinction laws in local galaxies.

scholarly journals ETHOS – an effective parametrization and classification for structure formation: the non-linear regime at z ≳ 5

2020 ◽  
Vol 498 (3) ◽  
pp. 3403-3419
Author(s):  
Sebastian Bohr ◽  
Jesús Zavala ◽  
Francis-Yan Cyr-Racine ◽  
Mark Vogelsberger ◽  
Torsten Bringmann ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Structure Formation ◽  
Parameter Space ◽  
Broad Class ◽  
High Redshift ◽  
Acoustic Oscillations ◽  
Effective Parameters ◽  
Matter Power Spectrum ◽  
Wide Range ◽  
Non Linear

ABSTRACT We propose two effective parameters that fully characterize galactic-scale structure formation at high redshifts (z ≳ 5) for a variety of dark matter (DM) models that have a primordial cutoff in the matter power spectrum. Our description is within the recently proposed ETHOS framework and includes standard thermal warm DM (WDM) and models with dark acoustic oscillations (DAOs). To define and explore this parameter space, we use high-redshift zoom-in simulations that cover a wide range of non-linear scales from those where DM should behave as CDM (k ∼ 10 h Mpc−1), down to those characterized by the onset of galaxy formation (k ∼ 500 h Mpc−1). We show that the two physically motivated parameters hpeak and kpeak, the amplitude and scale of the first DAO peak, respectively, are sufficient to parametrize the linear matter power spectrum and classify the DM models as belonging to effective non-linear structure formation regions. These are defined by their relative departure from cold DM (kpeak → ∞) and WDM (hpeak = 0) according to the non-linear matter power spectrum and halo mass function. We identify a region where the DAOs still leave a distinct signature from WDM down to z = 5, while a large part of the DAO parameter space is shown to be degenerate with WDM. Our framework can then be used to seamlessly connect a broad class of particle DM models to their structure formation properties at high redshift without the need of additional N-body simulations.

INVESTIGATING THE TEMPORAL FLUCTUATIONS IN PARTICULATE MATTER DATA

2008 ◽  
Vol 08 (03n04) ◽  
pp. L401-L407
Author(s):  
LUCIANO TELESCA ◽  
ROSA CAGGIANO ◽  
VINCENZO LAPENNA ◽  
MICHELE LOVALLO ◽  
SERENA TRIPPETTA ◽  
...  
Keyword(s):  
Time Series ◽  
Particulate Matter ◽  
Power Spectrum ◽  
Spectrum Analysis ◽  
Aerosol Particles ◽  
Power Spectrum Analysis ◽  
Physical Processes ◽  
Temporal Fluctuations ◽  
Scaling Behaviour

The temporal fluctuations of particulate matter time series of three reference European stations have been investigated, by using the power spectrum analysis. Our results point out to the presence in particulate matter of annual periodicities superimposed on a scaling behaviour with exponent ranging between ~1.4 and ~1.6, indicating quite high persistent correlations. Furthermore, a crossover timescale at about 1 month, evidenced in all the signals analysed, could be linked with chemical-physical processes in which aerosol particles are involved during their atmospheric lifetimes.

scholarly journals Small-scale Substructure in Dark Matter Haloes: Where Does Galaxy Formation Come to an End?

2004 ◽  
Vol 220 ◽  
pp. 91-98 ◽  
Author(s):  
J. E. Taylor ◽  
J. Silk ◽  
A. Babul
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Structure Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Small Scale ◽  
Analytic Model ◽  
Model Predictions ◽  
Low Mass

Models of structure formation based on cold dark matter predict that most of the small dark matter haloes that first formed at high redshift would have merged into larger systems by the present epoch. Substructure in present-day haloes preserves the remains of these ancient systems, providing the only direct information we may ever have about the low-mass end of the power spectrum. We describe some recent attempts to model halo substructure down to very small masses, using a semi-analytic model of halo formation. We make a preliminary comparison between the model predictions, observations of substructure in lensed systems, and the properties of local satellite galaxies.

Analysis on Interference Impact of Wi-Fi on Digital Terrestrial Television Broadcasting

2016 ◽  
Vol 8 (1) ◽  
pp. 35-44 ◽  
Author(s):  
Guntis Ancans ◽  
Vjaceslavs Bobrovs ◽  
Arnis Ancans ◽  
Evaldas Stankevicius
Keyword(s):  
Communication Systems ◽  
Monte Carlo Analysis ◽  
Mobile Service ◽  
Analysis Tool ◽  
Television Broadcasting ◽  
Digital Terrestrial Television ◽  
Broadcasting Service ◽  
5 Ghz ◽  
Digital Dividend ◽  
Exact Amount

Transition from Analogue Terrestrial Television Broadcasting to Digital Terrestrial Television Broadcasting (DTTB) in the 470-862 MHz band made available amount of spectrum so-called digital dividend for other services i.e. 790-862 MHz band (800 MHz) to mobile service. Recently the 694-790 MHz band (700 MHz) was also allocated to mobile service in ITU Region 1. Spectrum allocated to a broadcasting service but not used locally is called as TV white spaces (TVWS). It is possible to introduce TVWS services in 470-790 MHz band under the condition that other services in this band already operating, or planned in the country and in neighboring countries, are adequately protected and this use does not violate the current ITU Radio Regulations. TVWS under some conditions locally could be used for mobile communication systems e.g. unlicensed Wireless Fidelity (Wi-Fi) using cognitive radio. As TVWS are located in the UHF band, the use of TVWS can provide significantly better coverage and wall penetration inside buildings than 2.4 GHz and 5 GHz range Wi-Fi frequencies. The exact amount of available spectrum for TVWS at any location will be dependent upon each country national situation e.g. DTTB planning configuration, other services use in the band. In case of deploying Wi-Fi in the TVWS the interference impact of Wi-Fi on DTTB has to be taken into account. The aim of this paper is to analyze the interference impact of Wi-Fi on DTTB. In this paper the interference occurring probability in DTTB receiver was evaluated by using Spectrum Engineering Advanced Monte-Carlo Analysis Tool (SEAMCAT).

scholarly journals Constraining high-redshift X-ray sources with next generation 21-cm power spectrum measurements

2016 ◽  
Vol 458 (3) ◽  
pp. 2710-2724 ◽  
Author(s):  
Aaron Ewall-Wice ◽  
Jacqueline Hewitt ◽  
Andrei Mesinger ◽  
Joshua S. Dillon ◽  
Adrian Liu ◽  
...  
Keyword(s):  
Power Spectrum ◽  
High Redshift ◽  
Next Generation ◽  
X Ray ◽  
Spectrum Measurements

Time and Invariance

Conceptus ◽  
2008 ◽  
Vol 37 (92) ◽  
Author(s):  
Friedel Weinert
Keyword(s):  
Quantum Mechanics ◽  
Special Theory ◽  
Physical World ◽  
Theory Of Relativity ◽  
Special Theory Of Relativity ◽  
Physical Processes ◽  
Classical Physics ◽  
Physical Laws ◽  
Do So

SummaryThe aim of this paper is to infer conclusions about the temporality of the physical world from central features of the measurement of time. In order to do so it makes a distinction between the passage of time and the measurement of the passage of time. Whilst the passage of time can be experienced on the basis of, say, chaotic processes, the measurement of the passage of time requires certain physical regularities. But regularity is not sufficient and it is important to highlight the connection between time, regularity and invariance in the measurement of time, especially with respect to classical physics, the Special theory of relativity and quantum mechanics. It is only after this connection has been clarified that the paper considers the dispute on whether the physical world is static or dynamic. As there are clearly both time-symmetric physical laws and time-asymmetric physical processes, the question is empirically underdetermined because the evidence is at present compatible with two incompatible views about the temporality of the physical world.

scholarly journals High-redshift cosmography: auxiliary variables versus Padé polynomials

2020 ◽  
Vol 494 (2) ◽  
pp. 2576-2590 ◽  
Author(s):  
S Capozziello ◽  
R D’Agostino ◽  
O Luongo
Keyword(s):  
High Redshift ◽  
Padé Approximation ◽  
Monte Carlo Analysis ◽  
Pade Approximation ◽  
Shift Parameter ◽  
Padé Approximations ◽  
Pade Approximations ◽  
Optimal Approach ◽  
Fifth Order ◽  
The Universe

ABSTRACT Cosmography becomes non-predictive when cosmic data span beyond the redshift limit z ≃ 1. This leads to a strong convergence issue that jeopardizes its viability. In this work, we critically compare the two main solutions of the convergence problem, i.e. the y-parametrizations of the redshift and the alternatives to Taylor expansions based on Padé series. In particular, among several possibilities, we consider two widely adopted parametrizations, namely y1 = 1−a and $y_2=\arctan (a^{-1}-1)$, being a the scale factor of the Universe. We find that the y2-parametrization performs relatively better than the y1-parametrization over the whole redshift domain. Even though y2 overcomes the issues of y1, we get that the most viable approximations of the luminosity distance dL(z) are given in terms of Padé approximations. In order to check this result by means of cosmic data, we analyse the Padé approximations up to the fifth order, and compare these series with the corresponding y-variables of the same orders. We investigate two distinct domains involving Monte Carlo analysis on the Pantheon Superovae Ia data, H(z) and shift parameter measurements. We conclude that the (2,1) Padé approximation is statistically the optimal approach to explain low- and high-redshift data, together with the fifth-order y2-parametrization. At high redshifts, the (3,2) Padé approximation cannot be fully excluded, while the (2,2) Padé one is essentially ruled out.

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