We alleviate the circularity problem, whereby gamma-ray bursts are not perfect distance indicators, by means of a new model-independent technique based on B'ezier polynomials. To do so, we use the well consolidate textit{Amati} and textit{Combo} correlations. We consider improved calibrated catalogs of mock data from differential Hubble rate points. To get our mock data, we use those machine learning scenarios that well adapt to gamma ray bursts, discussing in detail how we handle small amounts of data from our machine learning techniques. In particular, we explore only three machine learning treatments, i.e. emph{linear regression}, emph{neural network} and emph{random forest}, emphasizing quantitative statistical motivations behind these choices. Our calibration strategy consists in taking Hubble's data, creating the mock compilation using machine learning and calibrating the aforementioned correlations through B'ezier polynomials with a standard chi-square analysis first and then by means of a hierarchical Bayesian regression procedure. The corresponding catalogs, built up from the two correlations, have been used to constrain dark energy scenarios. We thus employ Markov Chain Monte Carlo numerical analyses based on the most recent Pantheon supernova data, baryonic acoustic oscillations and our gamma ray burst data. We test the standard $Lambda$CDM model and the Chevallier-Polarski-Linder parametrization. We discuss the recent $H_0$ tension in view of our results. Moreover, we highlight a further severe tension over $Omega_m$ and we conclude that a slight evolving dark energy model is possible.
{"title":"Model-independent calibrations of gamma-ray bursts using machine learning","authors":"O. Luongo, M. Muccino","doi":"10.1093/MNRAS/STAB795","DOIUrl":"https://doi.org/10.1093/MNRAS/STAB795","url":null,"abstract":"We alleviate the circularity problem, whereby gamma-ray bursts are not perfect distance indicators, by means of a new model-independent technique based on B'ezier polynomials. To do so, we use the well consolidate textit{Amati} and textit{Combo} correlations. We consider improved calibrated catalogs of mock data from differential Hubble rate points. To get our mock data, we use those machine learning scenarios that well adapt to gamma ray bursts, discussing in detail how we handle small amounts of data from our machine learning techniques. In particular, we explore only three machine learning treatments, i.e. emph{linear regression}, emph{neural network} and emph{random forest}, emphasizing quantitative statistical motivations behind these choices. Our calibration strategy consists in taking Hubble's data, creating the mock compilation using machine learning and calibrating the aforementioned correlations through B'ezier polynomials with a standard chi-square analysis first and then by means of a hierarchical Bayesian regression procedure. The corresponding catalogs, built up from the two correlations, have been used to constrain dark energy scenarios. We thus employ Markov Chain Monte Carlo numerical analyses based on the most recent Pantheon supernova data, baryonic acoustic oscillations and our gamma ray burst data. We test the standard $Lambda$CDM model and the Chevallier-Polarski-Linder parametrization. We discuss the recent $H_0$ tension in view of our results. Moreover, we highlight a further severe tension over $Omega_m$ and we conclude that a slight evolving dark energy model is possible.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75467846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-27DOI: 10.1103/PHYSREVD.103.063530
L. F. Guimarães, F. Falciano
We show how to build a curvaton inflationary model motivated by scale-dependent non-Gaussianities of cosmological perturbations. In particular, we study the change of sign in the $f_{NL}$ parameter as a function of the curvaton field value at horizon crossing and identify it with the cosmic microwave background pivot scale. We devise a procedure to recover the curvaton model that provides the desired $f_{NL}$ parameter. We then present a concrete example of $f_{NL}$ and construct its parent model. We study the constraints applied to this model based on considerations taken on $f_{NL}$. We show that the hemispherical asymmetry can also be used to constrain the scale-dependence of $f_{NL}$ and the model parameters.
{"title":"Viable curvaton models from the \u0000fNL\u0000 parameter","authors":"L. F. Guimarães, F. Falciano","doi":"10.1103/PHYSREVD.103.063530","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.063530","url":null,"abstract":"We show how to build a curvaton inflationary model motivated by scale-dependent non-Gaussianities of cosmological perturbations. In particular, we study the change of sign in the $f_{NL}$ parameter as a function of the curvaton field value at horizon crossing and identify it with the cosmic microwave background pivot scale. We devise a procedure to recover the curvaton model that provides the desired $f_{NL}$ parameter. We then present a concrete example of $f_{NL}$ and construct its parent model. We study the constraints applied to this model based on considerations taken on $f_{NL}$. We show that the hemispherical asymmetry can also be used to constrain the scale-dependence of $f_{NL}$ and the model parameters.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87462200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-26DOI: 10.1103/PHYSREVD.103.063525
Benedikt Eggemeier, J. Niemeyer, R. Easther
The early Universe may have passed through an extended period of matter-dominated expansion following inflation and prior to the onset of radiation domination. Sub-horizon density perturbations grow gravitationally during such an epoch, collapsing into bound structures if it lasts long enough. The strong analogy between this phase and structure formation in the present-day universe allows the use of N-body simulations and approximate methods for halo formation to model the fragmentation of the inflaton condensate into inflaton halos. For a simple model we find these halos have masses of up to $20,mathrm{kg}$ and radii of the order of $10^{-20},mathrm{m}$, roughly $10^{-24}$ seconds after the Big Bang. We find that the N-body halo mass function matches predictions of the mass-Peak Patch method and the Press-Schechter formalism within the expected range of scales. A long matter-dominated phase would imply that reheating and thermalization occurs in a universe with large variations in density, potentially modifying the dynamics of this process. In addition, large overdensities can source gravitational waves and may lead to the formation of primordial black holes.
{"title":"Formation of inflaton halos after inflation","authors":"Benedikt Eggemeier, J. Niemeyer, R. Easther","doi":"10.1103/PHYSREVD.103.063525","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.063525","url":null,"abstract":"The early Universe may have passed through an extended period of matter-dominated expansion following inflation and prior to the onset of radiation domination. Sub-horizon density perturbations grow gravitationally during such an epoch, collapsing into bound structures if it lasts long enough. The strong analogy between this phase and structure formation in the present-day universe allows the use of N-body simulations and approximate methods for halo formation to model the fragmentation of the inflaton condensate into inflaton halos. For a simple model we find these halos have masses of up to $20,mathrm{kg}$ and radii of the order of $10^{-20},mathrm{m}$, roughly $10^{-24}$ seconds after the Big Bang. We find that the N-body halo mass function matches predictions of the mass-Peak Patch method and the Press-Schechter formalism within the expected range of scales. A long matter-dominated phase would imply that reheating and thermalization occurs in a universe with large variations in density, potentially modifying the dynamics of this process. In addition, large overdensities can source gravitational waves and may lead to the formation of primordial black holes.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"153 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84821664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-26DOI: 10.1051/0004-6361/202039999
J. Einasto, A. Klypin, G. Hütsi, L. Liivamägi, M. Einasto
We perform numerical simulations of the evolution of the cosmic web for the conventional $Lambda$CDM model in box sizes $L_0=256,~512,~1024$~Mpc. We calculate models, corresponding to the present epoch $z=0$, and to redshifts $z=1,~3,~5,~10,~30$. We calculate density fields with various smoothing levels to find the dependence of the density field on smoothing. We calculate PDF and its moments -- variance, skewness and kurtosis. The dimensionless skewness $S$ and the dimensionless kurtosis $K$ characterise symmetry and flatness properties of the 1-point PDF of the cosmic web. Relations $S =S_3 sigma$, and $K=S_4 sigma^2$ are now tested in standard deviation $sigma$ range, $0.015 le sigma le 10$, and in redshift $z$ range $0 le z le 30$. Reduced skewness $S_3$ and reduced kurtosis $S_4$ described in log-log format. Data show that these relations can be extrapolated to earlier redshifts $z$, and to smaller $sigma$, as. well as to smaller and larger smoothing lengths $R$. Reduced parameters depend on basic parameters of models. The reduced skewness: $S_3 = f_3(R) +g_3(z),sigma^2$, and the reduced kurtosis: $S_4 = f_4(R) +g_4(z),sigma^2$, where $f_3(R)$ and $f_4(R)$ are parameters, depending on the smoothing length, $R$, and $g_3(z)$ and $g_4(z)$ are parameters, depending on the evolutionary epoch $z$. The lower bound of the amplitude parameters are, $f_3(R) approx 3.5$ for reduced skewness, and $f_4(R) approx 16$ for reduced kurtosis, for large smoothing lengths, $Rapprox 32$~Mpc. With decreasing smoothing length $R$ the skewness and kurtosis values for given redshift $z$ turn upwards.
我们对传统的$Lambda$ CDM模型在盒子尺寸$L_0=256,~512,~1024$Mpc中进行了宇宙网演化的数值模拟。我们计算模型，对应于现在的时代$z=0$和红移$z=1,~3,~5,~10,~30$。我们计算了不同平滑程度的密度场，以找出密度场对平滑的依赖关系。我们计算PDF和它的矩——方差、偏度和峰度。无量纲偏度$S$和无量纲峰度$K$表征了宇宙网1点PDF的对称性和平整性。关系$S =S_3 sigma$和$K=S_4 sigma^2$现在在标准偏差$sigma$范围、$0.015 le sigma le 10$范围和红移$z$范围$0 le z le 30$中进行测试。降低偏度$S_3$和降低峰度$S_4$以对数-对数格式描述。数据显示，这些关系可以外推到更早的红移$z$和更小的$sigma$，如。以及更小和更大的平滑长度$R$。约简参数依赖于模型的基本参数。偏度的简化:$S_3 = f_3(R) +g_3(z),sigma^2$，峰度的简化:$S_4 = f_4(R) +g_4(z),sigma^2$，其中$f_3(R)$和$f_4(R)$是参数，取决于平滑长度，$R$, $g_3(z)$和$g_4(z)$是参数，取决于进化时代$z$。振幅参数的下界为:$f_3(R) approx 3.5$表示减少偏度，$f_4(R) approx 16$表示减少峰度，对于较大的平滑长度，$Rapprox 32$Mpc。随着平滑长度$R$的减小，给定红移的偏度和峰度值$z$呈上升趋势。
{"title":"Evolution of skewness and kurtosis of cosmic density fields","authors":"J. Einasto, A. Klypin, G. Hütsi, L. Liivamägi, M. Einasto","doi":"10.1051/0004-6361/202039999","DOIUrl":"https://doi.org/10.1051/0004-6361/202039999","url":null,"abstract":"We perform numerical simulations of the evolution of the cosmic web for the conventional $Lambda$CDM model in box sizes $L_0=256,~512,~1024$~Mpc. We calculate models, corresponding to the present epoch $z=0$, and to redshifts $z=1,~3,~5,~10,~30$. We calculate density fields with various smoothing levels to find the dependence of the density field on smoothing. We calculate PDF and its moments -- variance, skewness and kurtosis. The dimensionless skewness $S$ and the dimensionless kurtosis $K$ characterise symmetry and flatness properties of the 1-point PDF of the cosmic web. Relations $S =S_3 sigma$, and $K=S_4 sigma^2$ are now tested in standard deviation $sigma$ range, $0.015 le sigma le 10$, and in redshift $z$ range $0 le z le 30$. Reduced skewness $S_3$ and reduced kurtosis $S_4$ described in log-log format. Data show that these relations can be extrapolated to earlier redshifts $z$, and to smaller $sigma$, as. well as to smaller and larger smoothing lengths $R$. Reduced parameters depend on basic parameters of models. The reduced skewness: $S_3 = f_3(R) +g_3(z),sigma^2$, and the reduced kurtosis: $S_4 = f_4(R) +g_4(z),sigma^2$, where $f_3(R)$ and $f_4(R)$ are parameters, depending on the smoothing length, $R$, and $g_3(z)$ and $g_4(z)$ are parameters, depending on the evolutionary epoch $z$. The lower bound of the amplitude parameters are, $f_3(R) approx 3.5$ for reduced skewness, and $f_4(R) approx 16$ for reduced kurtosis, for large smoothing lengths, $Rapprox 32$~Mpc. With decreasing smoothing length $R$ the skewness and kurtosis values for given redshift $z$ turn upwards.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"75 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80918616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-24DOI: 10.1103/PHYSREVD.103.083025
A. Schneider, S. Giri, J. Mirocha
Prior to the epoch of reionisation, the 21-cm signal of the cosmic dawn is dominated by the Lyman-$alpha$ coupling and gas temperature fluctuations caused by the first sources of radiation. While early efforts to model this epoch relied on analytical techniques, the community quickly transitioned to more expensive semi-numerical models. Here, we re-assess the viability of simpler approaches that allow for rapid explorations of the vast astrophysical parameter space. We propose a new analytical method to calculate the 21-cm power spectrum based on the framework of the halo model. Both the Lyman-$alpha$ coupling and temperature fluctuations are described by overlapping radiation flux profiles that include spectral red-shifting and source attenuation due to look-back (light-cone) effects. The 21-cm halo model is compared to the semi-numerical code 21cmFAST exhibiting generally good agreement, i.e., the power spectra differ by less than a factor of three over a large range of $k$-modes and redshifts. We show that the remaining differences between the two methods are comparable to the expected variations from modelling uncertainties associated with the abundance, bias, and accretion rates of haloes. While these current uncertainties must be reduced in the future, our work suggests that inference at acceptable accuracy will become feasible with very efficient halo models of the cosmic dawn.
{"title":"Halo model approach for the 21-cm power spectrum at cosmic dawn","authors":"A. Schneider, S. Giri, J. Mirocha","doi":"10.1103/PHYSREVD.103.083025","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.083025","url":null,"abstract":"Prior to the epoch of reionisation, the 21-cm signal of the cosmic dawn is dominated by the Lyman-$alpha$ coupling and gas temperature fluctuations caused by the first sources of radiation. While early efforts to model this epoch relied on analytical techniques, the community quickly transitioned to more expensive semi-numerical models. Here, we re-assess the viability of simpler approaches that allow for rapid explorations of the vast astrophysical parameter space. We propose a new analytical method to calculate the 21-cm power spectrum based on the framework of the halo model. Both the Lyman-$alpha$ coupling and temperature fluctuations are described by overlapping radiation flux profiles that include spectral red-shifting and source attenuation due to look-back (light-cone) effects. The 21-cm halo model is compared to the semi-numerical code 21cmFAST exhibiting generally good agreement, i.e., the power spectra differ by less than a factor of three over a large range of $k$-modes and redshifts. We show that the remaining differences between the two methods are comparable to the expected variations from modelling uncertainties associated with the abundance, bias, and accretion rates of haloes. While these current uncertainties must be reduced in the future, our work suggests that inference at acceptable accuracy will become feasible with very efficient halo models of the cosmic dawn.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"138 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91447028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-24DOI: 10.12693/APhysPolA.139.389
B. Czerny, M. L. Mart'inez-Aldama, G. Wojtkowska, M. Zajavcek, P. Marziani, D. Dultzin, M. Naddaf, S. Panda, R. Prince, R. Przyluski, M. Rałowski, M. Śniegowska
Recent measurements of the parameters of the Concordance Cosmology Model ($Lambda$CDM) done in the low-redshift Universe with Supernovae Ia/Cepheids, and in the distant Universe done with Cosmic Microwave Background (CMB) imply different values for the Hubble constant (67.4 $pm$ 0.5 km s$^{-1}$ Mpc$^{-1}$ from Planck vs 74.03 $pm$ 1.42 km s$^{-1}$ Mpc$^{-1}$, Riess et al. 2019). This Hubble constant tension implies that either the systematic errors are underestimated, or the $Lambda$CDM does not represent well the observed expansion of the Universe. Since quasars - active galactic nuclei - can be observed in the nearby Universe up to redshift z $sim$ 7.5, they are suitable to estimate the cosmological properties in a large redshift range. Our group develops two methods based on the observations of quasars in the late Universe up to redshift z$sim $4.5, with the objective to determine the expansion rate of the Universe. These methods do not yet provide an independent measurement of the Hubble constant since they do not have firm absolute calibration but they allow to test the $Lambda$CDM model, and so far no departures from this model were found.
最近在Ia/造父变星超新星的低红移宇宙中进行的协和宇宙学模型($Lambda$ CDM)参数测量，以及在宇宙微波背景(CMB)完成的遥远宇宙中进行的测量，表明哈勃常数的值不同(普朗克的67.4 $pm$ 0.5 km s $^{-1}$ Mpc $^{-1}$与74.03 $pm$ 1.42 km s $^{-1}$ Mpc $^{-1}$, Riess等人。2019)。哈勃恒定的张力意味着要么系统误差被低估了，要么$Lambda$ CDM不能很好地代表观测到的宇宙膨胀。由于类星体-活动星系核-可以在附近的宇宙中观测到红移z $sim$ 7.5，因此它们适用于估计大红移范围内的宇宙学性质。我们的团队基于对宇宙晚期至红移z $sim $ 4.5的类星体的观测，开发了两种方法，目的是确定宇宙的膨胀率。这些方法还不能提供哈勃常数的独立测量，因为它们没有确定的绝对校准，但它们允许测试$Lambda$ CDM模型，到目前为止还没有发现偏离该模型的情况。
{"title":"Dark energy constraints from quasar observations","authors":"B. Czerny, M. L. Mart'inez-Aldama, G. Wojtkowska, M. Zajavcek, P. Marziani, D. Dultzin, M. Naddaf, S. Panda, R. Prince, R. Przyluski, M. Rałowski, M. Śniegowska","doi":"10.12693/APhysPolA.139.389","DOIUrl":"https://doi.org/10.12693/APhysPolA.139.389","url":null,"abstract":"Recent measurements of the parameters of the Concordance Cosmology Model ($Lambda$CDM) done in the low-redshift Universe with Supernovae Ia/Cepheids, and in the distant Universe done with Cosmic Microwave Background (CMB) imply different values for the Hubble constant (67.4 $pm$ 0.5 km s$^{-1}$ Mpc$^{-1}$ from Planck vs 74.03 $pm$ 1.42 km s$^{-1}$ Mpc$^{-1}$, Riess et al. 2019). This Hubble constant tension implies that either the systematic errors are underestimated, or the $Lambda$CDM does not represent well the observed expansion of the Universe. Since quasars - active galactic nuclei - can be observed in the nearby Universe up to redshift z $sim$ 7.5, they are suitable to estimate the cosmological properties in a large redshift range. Our group develops two methods based on the observations of quasars in the late Universe up to redshift z$sim $4.5, with the objective to determine the expansion rate of the Universe. These methods do not yet provide an independent measurement of the Hubble constant since they do not have firm absolute calibration but they allow to test the $Lambda$CDM model, and so far no departures from this model were found.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91325662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Matshawule, M. Spinelli, Mário G. Santos, Sibonelo Ngobese
Upcoming and future neutral hydrogen Intensity Mapping surveys offer a great opportunity to constrain cosmology in the post-reionization Universe, provided a good accuracy is achieved in the separation between the strong foregrounds and the cosmological signal. Cleaning methods rely on the frequency smoothness of the foregrounds and are often applied under the assumption of a simplistic Gaussian primary beam. In this work, we test the cleaning in the presence of a realistic primary beam model with a non trivial frequency dependence. We focus on the Square Kilometre Array precursor MeerKAT telescope and simulate a single-dish wide area survey. We consider the main foreground components, including an accurate full sky point source catalogue. We find that the coupling between beam sidelobes and the foreground structure can complicate the cleaning. However, when the beam frequency dependence is smooth, we show that the cleaning is only problematic if the far sidelobes are unexpectedly large. Even in that case, a proper reconstruction is possible if the strongest point sources are removed and the cleaning is more aggressive. We then consider a non-trivial frequency dependence: a sinusoidal type feature in the beam width that is present in the MeerKAT beam and is expected in most dishes, including SKA1-MID. Such a feature, coupling with the foreground emission, biases the reconstruction of the signal across frequency, potentially impacting the cosmological analysis. Interestingly, such contamination is present at a lower level even when no point sources are included and the beam is Gaussian, showing that this frequency ripple can be problematic even within the main lobe. We show that this effect is constrained to a narrow region in $k_parallel$ space and can be reduced if the maps are carefully re-smoothed to a common lower resolution.
{"title":"H i intensity mapping with MeerKAT: primary beam effects on foreground cleaning","authors":"S. Matshawule, M. Spinelli, Mário G. Santos, Sibonelo Ngobese","doi":"10.1093/mnras/stab1688","DOIUrl":"https://doi.org/10.1093/mnras/stab1688","url":null,"abstract":"Upcoming and future neutral hydrogen Intensity Mapping surveys offer a great opportunity to constrain cosmology in the post-reionization Universe, provided a good accuracy is achieved in the separation between the strong foregrounds and the cosmological signal. Cleaning methods rely on the frequency smoothness of the foregrounds and are often applied under the assumption of a simplistic Gaussian primary beam. In this work, we test the cleaning in the presence of a realistic primary beam model with a non trivial frequency dependence. We focus on the Square Kilometre Array precursor MeerKAT telescope and simulate a single-dish wide area survey. We consider the main foreground components, including an accurate full sky point source catalogue. We find that the coupling between beam sidelobes and the foreground structure can complicate the cleaning. However, when the beam frequency dependence is smooth, we show that the cleaning is only problematic if the far sidelobes are unexpectedly large. Even in that case, a proper reconstruction is possible if the strongest point sources are removed and the cleaning is more aggressive. We then consider a non-trivial frequency dependence: a sinusoidal type feature in the beam width that is present in the MeerKAT beam and is expected in most dishes, including SKA1-MID. Such a feature, coupling with the foreground emission, biases the reconstruction of the signal across frequency, potentially impacting the cosmological analysis. Interestingly, such contamination is present at a lower level even when no point sources are included and the beam is Gaussian, showing that this frequency ripple can be problematic even within the main lobe. We show that this effect is constrained to a narrow region in $k_parallel$ space and can be reduced if the maps are carefully re-smoothed to a common lower resolution.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87364714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Considering the cosmological redshift $z_c$ , the mass of GW source extracted from GW signal is $1+z_c$ times larger than its intrinsic value, and distance between detector and GW source should be regarded as luminosity distance. However, besides cosmological redshift, there are other kinds of redshifts should be considered, which is actually ignored, in the analysis of GW data, such as Doppler redshift and gravitational redshift, so the parameters extracted from GW may deviate from their intrinsic values. Another factor that may affect GW is the viscous medium in propagation path of GW, which may damp the GW with a damping rate of $16{pi}G{eta}$. Some studies indicate dark matter may interact with each other, thus dark matter may be the origin of viscosity of cosmic medium. Then the GW may be rapidly damped by the viscous medium that is made of dark matter, such as dark matter "mini-spike" around intermediate mass black hole. In this article, we mainly discuss how Doppler and gravitational redshift, together with the damping effect of viscous medium, affect the informations, such as the mass and redshift of GW source, extracted from GW signals.
{"title":"The effect of redshift degeneracy and the damping effect of viscous medium on the information extracted from gravitational wave signals","authors":"Shou-Li Ning, Lixin Xu","doi":"10.1093/mnras/staa3592","DOIUrl":"https://doi.org/10.1093/mnras/staa3592","url":null,"abstract":"Considering the cosmological redshift $z_c$ , the mass of GW source extracted from GW signal is $1+z_c$ times larger than its intrinsic value, and distance between detector and GW source should be regarded as luminosity distance. However, besides cosmological redshift, there are other kinds of redshifts should be considered, which is actually ignored, in the analysis of GW data, such as Doppler redshift and gravitational redshift, so the parameters extracted from GW may deviate from their intrinsic values. Another factor that may affect GW is the viscous medium in propagation path of GW, which may damp the GW with a damping rate of $16{pi}G{eta}$. Some studies indicate dark matter may interact with each other, thus dark matter may be the origin of viscosity of cosmic medium. Then the GW may be rapidly damped by the viscous medium that is made of dark matter, such as dark matter \"mini-spike\" around intermediate mass black hole. In this article, we mainly discuss how Doppler and gravitational redshift, together with the damping effect of viscous medium, affect the informations, such as the mass and redshift of GW source, extracted from GW signals.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81413802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-16DOI: 10.1103/physrevd.103.083523
M. Farhang, N. Khosravi
In this work we investigate whether a certain phenomenological extension to the general relativity (GR), in the form of a gravitational phase transition (GPT) in the Universe, can reduce the external $Planck$ tensions with the local Hubble measurements and the distribution of matter, characterized by $sigma_8$, as well as its internal inconsistencies in the lensing amplitude and the low--high $ell$ parameter estimates. We introduce new degrees of freedom into the background and the two scalar perturbation equations in the Newtonian gauge, with simultaneous transitions from an early gravitational phase equivalent to GR toward a late phase. We model the transition as a "tanh" parametrized by the transition redshift $z_{rm t}$ and width $alpha$, with amplitudes $Lambda(z)$ and $(mu(z),gamma(z))$ for the background and perturbations respectively. We verify the consistency of the datasets used in this work in the GPT framework and confirm that the individual tensions do not require conflicting transitions. We find that the joint datasets prefer a recent transition at $z_{rm t}approx 0.9$ in the background and perturbed Einstein equations, driven mainly by the local Hubble measurement. This transition relaxes all the tensions considered in this work.
{"title":"Phenomenological gravitational phase transition: Reconciliation between the late and early Universe","authors":"M. Farhang, N. Khosravi","doi":"10.1103/physrevd.103.083523","DOIUrl":"https://doi.org/10.1103/physrevd.103.083523","url":null,"abstract":"In this work we investigate whether a certain phenomenological extension to the general relativity (GR), in the form of a gravitational phase transition (GPT) in the Universe, can reduce the external $Planck$ tensions with the local Hubble measurements and the distribution of matter, characterized by $sigma_8$, as well as its internal inconsistencies in the lensing amplitude and the low--high $ell$ parameter estimates. We introduce new degrees of freedom into the background and the two scalar perturbation equations in the Newtonian gauge, with simultaneous transitions from an early gravitational phase equivalent to GR toward a late phase. We model the transition as a \"tanh\" parametrized by the transition redshift $z_{rm t}$ and width $alpha$, with amplitudes $Lambda(z)$ and $(mu(z),gamma(z))$ for the background and perturbations respectively. We verify the consistency of the datasets used in this work in the GPT framework and confirm that the individual tensions do not require conflicting transitions. We find that the joint datasets prefer a recent transition at $z_{rm t}approx 0.9$ in the background and perturbed Einstein equations, driven mainly by the local Hubble measurement. This transition relaxes all the tensions considered in this work.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"204 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80310318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-16DOI: 10.1103/PHYSREVD.103.083519
Gabriela Sato-Polito, J. Bernal, K. Boddy, M. Kamionkowski
The kinetic Sunyaev-Zel'dovich (kSZ) effect is a secondary cosmic microwave background (CMB) anisotropy induced by the scattering of CMB photons off intervening electrons. Through cross-correlations with tracers of large-scale structure, the kSZ effect can be used to reconstruct the 3-dimensional radial-velocity field, a technique known as kSZ tomography. We explore the cross-correlation between the CMB and line-intensity fluctuations to retrieve the late-time kSZ signal across a wide redshift range. We focus on the CII emission line, and predict the signal-to-noise ratio of the kSZ tomography signal between redshifts $z=1-5$ for upcoming experiments. We show that while instruments currently under construction may reach a low-significance detection of kSZ tomography, next-generation experiments will achieve greater sensitivity, with a detection significance of $mathcal{O}(10^2-10^3)$. Due to sample-variance cancellation, the cross-correlation between the reconstructed velocity field from kSZ tomography and intensity fluctuations can improve measurements of %the scale-dependent bias contributions from new physics to the power spectrum at large scales. To illustrate this improvement, we consider models of the early Universe that induce primordial local-type non-gaussianity and correlated compensated isocurvature perturbations. We show that with CMB-S4 and an AtLAST-like survey, the uncertainty on $f_{rm NL}$ and $A_{rm CIP}$ can be reduced by a factor of $sim 3$, achieving $sigma(f_{rm NL}) lesssim 1$. We further show that probing both low and high redshifts is crucial to break the degeneracy between the two parameters.
动力学Sunyaev-Zel'dovich (kSZ)效应是宇宙微波背景(CMB)的二次各向异性，是由介入电子对CMB光子的散射引起的。通过与大尺度结构示踪剂的相互关联，kSZ效应可以用来重建三维径向速度场，这种技术被称为kSZ层析成像。我们探索了CMB与线强度波动之间的相互关系，以检索宽红移范围内的晚时间kSZ信号。我们将重点放在CII发射线上，并预测kSZ层析成像信号在红移之间的信噪比$z=1-5$，为接下来的实验做准备。我们表明，虽然目前正在建设的仪器可能达到kSZ层析成像的低显著性检测，但下一代实验将实现更高的灵敏度，检测显著性为$mathcal{O}(10^2-10^3)$。由于样本方差抵消，kSZ层析成像重建的速度场与强度波动之间的相互关系可以改善测量 %the scale-dependent bias contributions from new physics to the power spectrum at large scales. To illustrate this improvement, we consider models of the early Universe that induce primordial local-type non-gaussianity and correlated compensated isocurvature perturbations. We show that with CMB-S4 and an AtLAST-like survey, the uncertainty on $f_{rm NL}$ and $A_{rm CIP}$ can be reduced by a factor of $sim 3$, achieving $sigma(f_{rm NL}) lesssim 1$. We further show that probing both low and high redshifts is crucial to break the degeneracy between the two parameters.
{"title":"Kinetic Sunyaev-Zel’dovich tomography with line-intensity mapping","authors":"Gabriela Sato-Polito, J. Bernal, K. Boddy, M. Kamionkowski","doi":"10.1103/PHYSREVD.103.083519","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.083519","url":null,"abstract":"The kinetic Sunyaev-Zel'dovich (kSZ) effect is a secondary cosmic microwave background (CMB) anisotropy induced by the scattering of CMB photons off intervening electrons. Through cross-correlations with tracers of large-scale structure, the kSZ effect can be used to reconstruct the 3-dimensional radial-velocity field, a technique known as kSZ tomography. We explore the cross-correlation between the CMB and line-intensity fluctuations to retrieve the late-time kSZ signal across a wide redshift range. We focus on the CII emission line, and predict the signal-to-noise ratio of the kSZ tomography signal between redshifts $z=1-5$ for upcoming experiments. We show that while instruments currently under construction may reach a low-significance detection of kSZ tomography, next-generation experiments will achieve greater sensitivity, with a detection significance of $mathcal{O}(10^2-10^3)$. Due to sample-variance cancellation, the cross-correlation between the reconstructed velocity field from kSZ tomography and intensity fluctuations can improve measurements of %the scale-dependent bias contributions from new physics to the power spectrum at large scales. To illustrate this improvement, we consider models of the early Universe that induce primordial local-type non-gaussianity and correlated compensated isocurvature perturbations. We show that with CMB-S4 and an AtLAST-like survey, the uncertainty on $f_{rm NL}$ and $A_{rm CIP}$ can be reduced by a factor of $sim 3$, achieving $sigma(f_{rm NL}) lesssim 1$. We further show that probing both low and high redshifts is crucial to break the degeneracy between the two parameters.","PeriodicalId":8431,"journal":{"name":"arXiv: Cosmology and Nongalactic Astrophysics","volume":"164 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83871496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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