IA Scholar Query: healpy: equal area pixelization and spherical harmonics transforms for data on the sphere in Python.
https://scholar.archive.org/
Internet Archive Scholar query results feedeninfo@archive.orgThu, 15 Sep 2022 00:00:00 GMTfatcat-scholarhttps://scholar.archive.org/help1440A tomographic spherical mass map emulator of the KiDS-1000 survey using conditional generative adversarial networks
https://scholar.archive.org/work/jwnwfbeu5ncxzjhuoj57sq43oe
Large sets of matter density simulations are becoming increasingly important in large scale structure cosmology. Matter power spectra emulators, such as the Euclid Emulator and CosmicEmu, are trained on simulations to correct the non-linear part of the power spectrum. Map-based analyses retrieve additional non-Gaussian information from the density field, whether through human-designed statistics such as peak counts, or via machine learning methods such as convolutional neural networks (CNNs). The simulations required for these methods are very resource-intensive, both in terms of computing time and storage. Map-level density field emulators, based on deep generative models, have recently been proposed to address these challenges. In this work, we present a novel mass map emulator of the KiDS-1000 survey footprint, which generates noise-free spherical maps in a fraction of a second. It takes a set of cosmological parameters (Ω_M, σ_8) as input and produces a consistent set of 5 maps, corresponding to the KiDS-1000 tomographic redshift bins. To construct the emulator, we use a conditional generative adversarial network architecture and the spherical CNN , and train it on N-body-simulated mass maps. We compare its performance using an array of quantitative comparison metrics: angular power spectra C_ℓ, pixel/peaks distributions, C_ℓ correlation matrices, and Structural Similarity Index. Overall, the agreement on these summary statistics is <10% for the cosmologies at the centre of the simulation grid, and degrades slightly on grid edges. Finally, we perform a mock cosmological parameter estimation using the emulator and the original simulation set. We find good agreement in these constraints, for both likelihood and likelihood-free approaches. The emulator is available at https://tfhub.dev/cosmo-group-ethz/models/kids-cgan/1.Timothy Wing Hei Yiu, Janis Fluri, Tomasz Kacprzakwork_jwnwfbeu5ncxzjhuoj57sq43oeThu, 15 Sep 2022 00:00:00 GMTCosmoGridV1: a simulated wCDM theory prediction for map-level cosmological inference
https://scholar.archive.org/work/jqsf4jku7vgl7abb5rlonzqbyq
We present CosmoGridV1: a large set of lightcone simulations for map-level cosmological inference with probes of large scale structure. It is designed for cosmological parameter measurement based on Stage-III photometric surveys with non-Gaussian statistics and machine learning. CosmoGridV1 spans the wCDM model by varying Ω_m, σ_8, w_0, H_0, n_s, Ω_b, and assumes three degenerate neutrinos with ∑ m_ν = 0.06 eV. This space is covered by 2500 grid points on a Sobol sequence. At each grid point, we run 7 simulations with PkdGrav3 and store 69 particle maps at nside=2048 up to z=3.5, as well as halo catalog snapshots. The fiducial cosmology has 200 independent simulations, along with their stencil derivatives. An important part of CosmoGridV1 is the benchmark set of 28 simulations, which include larger boxes, higher particle counts, and higher redshift resolution of shells. They allow for testing if new types of analyses are sensitive to choices made in CosmoGridV1. We add baryon feedback effects on the map level, using shell-based baryon correction model. The shells are used to create maps of weak gravitational lensing, intrinsic alignment, and galaxy clustering, using the UFalcon code. The main part of CosmoGridV1 are the raw particle count shells that can be used to create full-sky maps for a given n(z). We also release projected maps for a Stage-III forecast, as well as maps used previously in KiDS-1000 deep learning constraints with CosmoGridV1. The data is available at www.cosmogrid.ai.Tomasz Kacprzak, Janis Fluri, Aurel Schneider, Alexandre Refregier, Joachim Stadelwork_jqsf4jku7vgl7abb5rlonzqbyqSat, 10 Sep 2022 00:00:00 GMTAnalysis of NILC performance on B-modes data of sub-orbital experiments
https://scholar.archive.org/work/yvsble7wabhp3pl6bgtigkh7eu
The observation of primordial B-modes in the Cosmic Microwave Background (CMB) represents the main scientific goal of most of the future CMB experiments. Such signal is predicted to be much lower than the polarised Galactic emission (foregrounds) in any region of the sky pointing to the need for complex components separation methods, such as the Needlet-ILC (NILC). In this work we explore the possibility of employing NILC for B-modes maps reconstructed from partial-sky data of sub-orbital experiments, addressing the complications that such an application yields: E-B leakage, needlet filtering and beam convolution. We consider two complementary simulated datasets from future experiments: the balloon-borne SWIPE telescope of the Large Scale Polarization Explorer, which targets the observation of both reionisation and recombination peaks of the primordial B-modes angular power spectrum, and the ground-based Small Aperture Telescope of Simons Observatory, which is designed to observe only the recombination bump. We assess the performance of two alternative techniques for correcting the CMB E-B leakage: the recycling technique (Liu et al. 2019) and the ZB method (Zhao Baskaran 2010). We find that they both reduce the E-B leakage residuals at a negligible level given the sensitivity of the considered experiments, except for the recycling method on the SWIPE patch at ℓ < 20. Thus, we implement two extensions of the pipeline, the iterative B-decomposition and the diffusive inpainting, which permit to recover the input CMB B-modes power for ℓ≥ 5. For the considered experiments, we demonstrate that needlet filtering and beam convolution do not affect the B-modes reconstruction. Finally, with an appropriate masking strategy, we find that NILC foregrounds subtraction allows to recover values of the tensor-to-scalar ratio compatible to the targets of the considered CMB experiments.Alessandro Carones, Marina Migliaccio, Domenico Marinucci, Nicola Vittoriowork_yvsble7wabhp3pl6bgtigkh7euThu, 25 Aug 2022 00:00:00 GMTThe star formation history in the last 10 billion years from CIB cross-correlations
https://scholar.archive.org/work/2y6xrgfluzhqfpnjiwh7u3gzti
The Cosmic Infrared Background (CIB) traces the emission of star-forming galaxies throughout all cosmic epochs. Breaking down the contribution from galaxies at different redshifts to the observed CIB maps would allow us to probe the history of star formation. In this paper, we cross-correlate maps of the CIB with galaxy samples covering the range z≲2 to measure the bias-weighted star-formation rate (SFR) density ⟨ bρ_ SFR⟩ as a function of time in a model independent way. This quantity is complementary to direct measurements of the SFR density ρ_ SFR, giving a higher weight to more massive haloes, and thus provides additional information to constrain the physical properties of star formation. Using cross-correlations of the CIB with galaxies from the DESI Legacy Survey and the extended Baryon Oscillation Spectroscopic Survey, we obtain high signal-to-noise ratio measurements of ⟨ bρ_ SFR⟩, which we then use to place constraints on halo-based models of the star-formation history. We fit halo-based SFR models to our data and compare the recovered ρ_ SFR with direct measurements of this quantity. We find a qualitatively good agreement between both independent datasets, although the details depend on the specific halo model assumed. This constitutes a useful robustness test for the physical interpretation of the CIB, and reinforces the role of CIB maps as valuable astrophysical probes of the large-scale structure. We report our measurements of ⟨ bρ_ SFR⟩ as well as a thorough account of their statistical uncertainties, which can be used to constrain star formation models in combination with other data.Baptiste Jego, Jaime Ruiz-Zapatero, Carlos García-García, Nick Koukoufilippas, David Alonsowork_2y6xrgfluzhqfpnjiwh7u3gztiThu, 30 Jun 2022 00:00:00 GMTLeveraging topology, geometry, and symmetries for efficient Machine Learning
https://scholar.archive.org/work/ei2jbnij4zedhiyq536b7idpda
First and foremost, I want to thank Pierre Vandergheynst for giving me the opportunity to pursue a PhD in his laboratory and for providing me with an environment where my creativity could flourish. Pierre gave me resources, freedom, and trust without asking for anything in return. Next, I want to thank Xavier Bresson for guiding me through both technical and non-technical matters. Xavier was an adviser and mentor until he left for his own lab. I would not be who I am without him. I am grateful to my thesis committee-Martin Jaggi, Pascal Frossard, Max Welling, Yan LeCun-for their interest and enthusiasm: it was an honor to discuss my research with you. Over the years, I had the pleasure to interact with and learn from many people. I thank Nathanaël Perraudin for his patience teaching me: I had so many questions! A unique collaborator and friend. Along with Vassilis Kalofolias and Johan Paratte, I thank this trio for bringing me into this journey at the LTS2 laboratory and getting me started. To them and to all the marvelous companions at the LTS2 and beyond, I thank you for the time we shared turning these years into a memorable experience. It was wonderful to grow together. Special thanks go to my office-mates, Nauman Shahid, Rodrigo Pena, Volodymir Miz, Konstantinos Pitas, and Youngjoo Seo: they made our office a lovely place and the table football a source of much after-lunch excitement. I thank my collaborators, includingMichaël Defferrardwork_ei2jbnij4zedhiyq536b7idpdaTue, 31 May 2022 00:00:00 GMTReconstructing the Sky with CMB Lensing methods
https://scholar.archive.org/work/txvtz6h3znaajgl2tgzifcmyim
Current and future high significance CMB lensing-galaxy cross-correlations will soon precisely probe the growth of structure and provide powerful tests for parameter tensions, non-Gaussianity, neutrino mass, and modifications to Λ−CDM and gravity. However, such cross-correlations are sensitive to CMB foreground contamination, and the resulting biases represent an important challenge for cosmological analyses. In this thesis we describe new CMB lensing cross-correlation measurements and a novel multi-frequency cleaning-based technique to mitigate foreground effects in lensing maps. In particular, we present a tSZ cleaned cross-spectrum between Atacama Cosmology Telescope lensing and BOSS galaxies using a modified version of the standard quadratic estimator that retains most of the signal-to-noise. To minimize lensing foreground biases, geometry-based methods that modify the form of the standard quadratic estimator have been developed as well. We discuss how to optimally combine these with multi-frequency cleaned data to mitigate the impact of foreground contamination while maintaining maximal significance. For a Simons Observatory-like experiment, we find that for the CMB lensing auto-spectrum it is possible to reduce the foreground induced bias by a large factor, compared to the standard quadratic estimator, at a modest noise cost. We find a similar result for a cross-correlation with an LSST-like sample, with a large reduction in bias at small noise cost. Finally, we turn to the three-dimensional large scale structure of the Universe probed by galaxy surveys. We show how we can reconstruct the large-scale density field from galaxy modes using CMB lensing-inspired methods and use this reconstruction to improve constraints on local primordial non-Gaussianity.Omar Darwish, Apollo-University Of Cambridge Repository, Blake Sherwinwork_txvtz6h3znaajgl2tgzifcmyimMon, 30 May 2022 00:00:00 GMTOptimal method for reconstructing polychromatic maps from broadband observations with an aysmmetric antenna pattern
https://scholar.archive.org/work/7i2kyosr7bchpmuen35lvglaz4
Broadband time-ordered data obtained from telescopes with a wavelength-dependent, asymmetric beam pattern can be used to extract maps at multiple wavelengths from a single scan. This technique is especially useful when collecting data on cosmic phenomena such as the Cosmic Microwave Background (CMB) radiation, as it provides the ability to separate the CMB signal from foreground contaminants. We develop a method to determine the optimal linear combinations of wavelengths ("colors") that can be reconstructed for a given telescope design and the number of colors that are measurable with high signal-to-noise ratio. The optimal colors are found as eigenvectors of a matrix derived from the inverse noise covariance matrix. When the telescope is able to scan the sky isotropically, it is useful to transform to a spherical harmonic basis, in which this matrix has a particularly simple form. We propose using the optimal colors determined from the isotropic case even when the actual scanning pattern is not isotropic (e.g., covers only part of the sky). We perform simulations showing that maps in multiple colors can be reconstructed accurately from both full-sky and partial-sky scans. Although the original motivation for this research comes from mapping the CMB, this method of polychromatic map-making will have broader applications throughout astrophysics.Brianna Cantrall, Solomon Quinn, Emory F. Bunnwork_7i2kyosr7bchpmuen35lvglaz4Mon, 16 May 2022 00:00:00 GMTImpact of Point Spread Function Higher Moments Error on Weak Gravitational Lensing II: A Comprehensive Study
https://scholar.archive.org/work/64fyqqdaozdifbfmnj2knyoef4
Weak gravitational lensing, or weak lensing, is one of the most powerful probes for dark matter and dark energy science, although it faces increasing challenges in controlling systematic uncertainties as the statistical errors become smaller. The Point Spread Function (PSF) needs to be precisely modeled to avoid systematic error on the weak lensing measurements. The weak lensing biases induced by errors in the PSF model second moments, i.e., its size and shape, are well-studied. However, Zhang et al. (2021) showed that errors in the higher moments of the PSF may also be a significant source of systematics for upcoming weak lensing surveys. Therefore, the goal of this work is to comprehensively investigate the modeling quality of PSF moments from the 3^rd to 6^th order, and estimate their impact on cosmological parameter inference. We propagate the PSFEx higher moments modeling error in the HSC survey dataset to the weak lensing shear-shear correlation functions and their cosmological analyses. We find that the overall multiplicative shear bias associated with errors in PSF higher moments can cause a ∼ 0.1 σ shift on the cosmological parameters for LSST Y10. PSF higher moment errors also cause additive biases in the weak lensing shear, which, if not accounted for in the cosmological parameter analysis, can induce cosmological parameter biases comparable to their 1σ uncertainties for LSST Y10. We compare the PSFEx model with PSF in Full FOV (Piff), and find similar performance in modeling the PSF higher moments. We conclude that PSF higher moment errors of the future PSF models should be reduced from those in current methods to avoid a need to explicitly model these effects in the weak lensing analysis.Tianqing Zhang, Husni Almoubayyed, Rachel Mandelbaum, Joshua E. Meyers, Mike Jarvis, Arun Kannawadi, Morgan A. Schmitz, Axel Guinot, The LSST Dark Energy Science Collaborationwork_64fyqqdaozdifbfmnj2knyoef4Mon, 16 May 2022 00:00:00 GMTThe C-Band All-Sky Survey (C-BASS): Template Fitting of Diffuse Galactic Microwave Emission in the Northern Sky
https://scholar.archive.org/work/v2zsxdvrffdvfoc35ctvanxqca
The C-Band All-Sky Survey (C-BASS) has observed the Galaxy at 4.76GHz with an angular resolution of 0.73^∘ full-width half-maximum, and detected Galactic synchrotron emission with high signal-to-noise ratio over the entire northern sky (δ > -15^∘). We present the results of a spatial correlation analysis of Galactic foregrounds at mid-to-high (b > 10^∘) Galactic latitudes using a preliminary version of the C-BASS intensity map. We jointly fit for synchrotron, dust, and free-free components between 20 and 1000GHz and look for differences in the Galactic synchrotron spectrum, and the emissivity of anomalous microwave emission (AME) when using either the C-BASS map or the 408MHz all-sky map to trace synchrotron emission. We find marginal evidence for a steepening (<Δβ> = -0.06±0.02) of the Galactic synchrotron spectrum at high frequencies resulting in a mean spectral index of <β> = -3.10±0.02 over 4.76-22.8GHz. Further, we find that the synchrotron emission can be well modelled by a single power-law up to a few tens of GHz. Due to this, we find that the AME emissivity is not sensitive to changing the synchrotron tracer from the 408MHz map to the 4.76GHz map. We interpret this as strong evidence for the origin of AME being spinning dust emission.S.E. Harper, C. Dickinson, A. Barr, R. Cepeda-Arroita, R.D.P. Grumitt, H.M. Heilgendorff, L. Jew, J.L. Jonas, M.E. Jones, J.P. Leahy, J. Leech, T.J. Pearson, M.W. Peel, A.C.S. Readhead, A.C. Taylorwork_v2zsxdvrffdvfoc35ctvanxqcaMon, 25 Apr 2022 00:00:00 GMTPreparing for a cosmological analysis of next generation radio observations
https://scholar.archive.org/work/56kfic3pibgvlnl7ayiceciqx4
In order to prepare for a cosmological analysis of the next generation of radio continuum surveys such as the Evolutionary Map of the Universe (EMU), we here investigate the galaxy properties and cosmological clustering of radio sources in a number of existing large area surveys with high sensitivity. In order to understand the types of galaxy likely to be observed at radio frequencies, we investigate the host galaxy properties of radio sources as a function of redshift and mass out to a redshift of z = 2.25 and use the resulting relations to produce a new simulated radio continuum sky. We compare the measured angular clustering of galaxies in this simulation to both real observations (via two of the largest μJy surveys to date) and more traditional numerical models of angular clustering at 1.4 GHz. Using cross identification of deep Very Large Array observations at 1.4 GHz with two deep Near Infrared (NIR) surveys, the Four Star Galaxy Evolution redshift survey (ZFOURGE)and the Newfirm Medium Band Survey (NMBS), we determine the galactic properties of 424 radio sources at flux densities greater than 50μJy in the COSMOS and CDFS fields. Both of these NIR surveys use medium band infrared filters to increase the accuracy of photometric redshifts at much earlier cosmic times than optical surveys. The wealth of ancillary data in these two fields is substantial, with up to 39 bands of photometry spanning from the ultraviolet to the far-infrared. This allows us to accurately estimate galaxy stellar-masses, star formation rates and dust contents. Using this data we identify radio-loud AGN using their 1.4 GHz and NIR+UV based star-formation rates. Objects whose radio emission is consistent with the star-formation rate are classified as star-forming dominated sources and those whose emission at 1.4 GHz is greater than three times what is expected from the NIR+UV star-formation rate are classified as radio-loud AGN. We compare the host properties of these objects in a mass (M ≥ 1010:5 M) and luminosity (L1:4 > 1024 W Hz [...]Glen Reeswork_56kfic3pibgvlnl7ayiceciqx4Mon, 28 Mar 2022 00:00:00 GMTHEALPix Alchemy: Fast All-Sky Geometry and Image Arithmetic in a Relational Database for Multimessenger Astronomy Brokers
https://scholar.archive.org/work/n3bymxue6ne4zmo56dctg2fdjy
Efficient searches for electromagnetic counterparts to gravitational wave, high-energy neutrino, and gamma-ray burst events demand rapid processing of image arithmetic and geometry set operations in a database to cross-match galaxy catalogs, observation footprints, and all-sky images. Here we introduce HEALPix Alchemy, an open-source, pure Python implementation of a set of methods that enables rapid all-sky geometry calculations. HEALPix Alchemy is built upon HEALPix, a spatial indexing strategy that is widely used in astronomical databases as well as the native format of LIGO-Virgo-KAGRA gravitational-wave sky localization maps. Our approach leverages new multirange types built into the PostgreSQL 14 database engine. This enables fast all-sky queries against probabilistic multimessenger event localizations and telescope survey footprints. Questions such as "What are the galaxies contained within the 90% credible region of an event?" and "What is the rank-ordered list of the fields within an observing footprint with the highest probability of containing the event?" can be performed in less than a few seconds on commodity hardware using off-the-shelf cloud-managed database implementations without server-side database extensions. Common queries scale roughly linearly with the number of telescope pointings. As the number of fields grows into the hundreds or thousands, HEALPix Alchemy is orders of magnitude faster than other implementations. HEALPix Alchemy is now used as the spatial geometry engine within SkyPortal, which forms the basis of the Zwicky Transient Facility transient marshal, called Fritz.Leo P. Singer, B. Parazin, Michael W. Coughlin, Joshua S. Bloom, Arien Crellin-Quick, Daniel A. Goldstein, Stéfan van der Waltwork_n3bymxue6ne4zmo56dctg2fdjyMon, 28 Mar 2022 00:00:00 GMTIn-flight polarization angle calibration for LiteBIRD: blind challenge and cosmological implications
https://scholar.archive.org/work/z2rwnnossraxtbcrwrrfnr2psu
We present a demonstration of the in-flight polarization angle calibration for the JAXA/ISAS second strategic large class mission, LiteBIRD, and estimate its impact on the measurement of the tensor-to-scalar ratio parameter, r, using simulated data. We generate a set of simulated sky maps with CMB and polarized foreground emission, and inject instrumental noise and polarization angle offsets to the 22 (partially overlapping) LiteBIRD frequency channels. Our in-flight angle calibration relies on nulling the EB cross correlation of the polarized signal in each channel. This calibration step has been carried out by two independent groups with a blind analysis, allowing an accuracy of the order of a few arc-minutes to be reached on the estimate of the angle offsets. Both the corrected and uncorrected multi-frequency maps are propagated through the foreground cleaning step, with the goal of computing clean CMB maps. We employ two component separation algorithms, the Bayesian-Separation of Components and Residuals Estimate Tool (B-SeCRET), and the Needlet Internal Linear Combination (NILC). We find that the recovered CMB maps obtained with algorithms that do not make any assumptions about the foreground properties, such as NILC, are only mildly affected by the angle miscalibration. However, polarization angle offsets strongly bias results obtained with the parametric fitting method. Once the miscalibration angles are corrected by EB nulling prior to the component separation, both component separation algorithms result in an unbiased estimation of the r parameter. While this work is motivated by the conceptual design study for LiteBIRD, its framework can be broadly applied to any CMB polarization experiment. In particular, the combination of simulation plus blind analysis provides a robust forecast by taking into account not only detector sensitivity but also systematic effects.Nicoletta Krachmalnicoff, Tomotake Matsumura, Elena de la Hoz, Soumen Basak, Alessandro Gruppuso, Yuto Minami, Carlo Baccigalupi, Eiichiro Komatsu, Enrique Martínez-González, Patricio Vielva, Jonathan Aumont, Ragnhild Aurlien, Susanna Azzoni, Anthony J. Banday, Rita B. Barreiro, Nicola Bartolo, Marco Bersanelli, Erminia Calabrese, Alessandro Carones, Francisco J. Casas, Kolen Cheung, Yuji Chinone, Fabio Columbro, Paolo de Bernardis, Patricia Diego-Palazuelos, Josquin Errard, Fabio Finelli, Unni Fuskeland, Mathew Galloway, Ricardo T. Genova-Santos, Martina Gerbino, Tommaso Ghigna, Serena Giardiello, Eirik Gjerløw, Masashi Hazumi, Sophie Henrot-Versillé, Theodore Kisner, Luca Lamagna, Massimiliano Lattanzi, François Levrier, Gemma Luzzi, Davide Maino, Silvia Masi, Marina Migliaccio, Ludovic Montier, Gianluca Morgante, Baptiste Mot, Ryo Nagata, Federico Nati, Paolo Natoli, Luca Pagano, Alessandro Paiella, Daniela Paoletti, Guillaume Patanchon, Francesco Piacentini, Gianluca Polenta, Davide Poletti, G. Puglisi, Mathieu Remazeilles, Jose Alberto Rubino-Martin, Manami Sasaki, Maresuke Shiraishi, Giovanni Signorelli, Samantha Stever, Andrea Tartari, Matthieu Tristram, Masatoshi Tsuji, Léo Vacher, Ingunn K. Wehus, Mario Zannoniwork_z2rwnnossraxtbcrwrrfnr2psuFri, 21 Jan 2022 00:00:00 GMTImaging the Southern Sky at 159MHz using Spherical Harmonics with the Engineering Development Array 2
https://scholar.archive.org/work/g7nvypxbtrazbjlddnzofm3cii
One of the major priorities of international radio astronomy is to study the early universe through the detection of the 21 cm HI line from the epoch of reionisation (EoR). Due to the weak nature of the 21 cm signal, an important part in the detection of the EoR is removing contaminating foregrounds from our observations as they are multiple orders of magnitude brighter. In order to achieve this, sky maps spanning a wide range of frequencies and angular scales are required for calibration and foreground subtraction. Complementing the existing low-frequency sky maps, we have constructed a Southern Sky map through spherical harmonic transit interferometry utilising the engineering development array 2 (EDA2), a square kilometre array (SKA) low-frequency array prototype system. We use the m-mode formalism to create an all-sky map at 159MHz with an angular resolution of 3 degrees, with data from the (EDA2) providing information over +60 degrees to -90 degrees in declination. We also introduce a new method for visualising and quantifying how the baseline distribution of an interferometer maps to the spherical harmonics, and discuss how prior information can be used to constrain spherical harmonic components that the interferometer is not sensitive to.Michael A. Kriele, Randall B. Wayth, Mark J. Bentum, Budi Juswardy, Cathryn M. Trottwork_g7nvypxbtrazbjlddnzofm3ciiWed, 12 Jan 2022 00:00:00 GMTImaging the southern sky at 159 MHz using spherical harmonics with the engineering development array 2
https://scholar.archive.org/work/vprc6r5jrraophqk4h75c2ffkq
One of the major priorities of international radio astronomy is to study the early universe through the detection of the 21 cm HI line from the epoch of reionisation (EoR). Due to the weak nature of the 21 cm signal, an important part in the detection of the EoR is removing contaminating foregrounds from our observations as they are multiple orders of magnitude brighter. In order to achieve this, sky maps spanning a wide range of frequencies and angular scales are required for calibration and foreground subtraction. Complementing the existing low-frequency sky maps, we have constructed a Southern Sky map through spherical harmonic transit interferometry utilising the Engineering Development Array 2 (EDA2), a Square Kilometre Array (SKA) low-frequency array prototype system. We use the m-mode formalism to create an all-sky map at 159 MHz with an angular resolution of 3 degrees, with data from the EDA2 providing information over +60 degrees to –90 degrees in declination. We also introduce a new method for visualising and quantifying how the baseline distribution of an interferometer maps to the spherical harmonics and discuss how prior information can be used to constrain spherical harmonic components that the interferometer is not sensitive to.Michael A. Kriele, Randall B. Wayth, Mark J. Bentum, Budi Juswardy, Cathryn M. Trottwork_vprc6r5jrraophqk4h75c2ffkqTesting extensions to the standard model of cosmology with the growth of structure
https://scholar.archive.org/work/3cw5xeyakjevjejxd6gij4priu
The past century has seen cosmologists piece together a working theory for the origin and evolution of structure in the Universe which has been hugely successful at describing a wide range of observations. This theoretical paradigm is called the LCDM model, which describes the two main constituents of our Universe: L, representing dark energy which drives the late-time accelerated expansion of space and CDM, representing cold dark matter, the main matter constituent of our Universe. Despite this, this thesis lays out some of the current tensions which have arisen with the current concordance model of cosmology and uses these to motivate exploring extensions to LCDM. The thesis is comprised of three main parts; in the first part I explore one of the predictions of inflation, which is a non-zero running of the scalar spectral index -- usually set to be zero in the LCDM model -- and its effects on the formation and evolution of large-scale structure. In particular I examine its effects on the abundance (through the halo mass function), distribution (through the two point auto-correlation function) and internal properties (through total matter density profiles) of dark matter haloes, finding effects of the order 10% in all of these quantities when comparing to a LCDM simulation. I also show that these effects due to cosmology are separable from the effects present due to galaxy formation physics to typically better than 1% accuracy. In the second part of this thesis, I focus on the effects warm dark matter, self-interacting dark matter and a running scalar spectral index have on galaxy scales, with particular focus on Milky Way mass haloes. In this part of the thesis I explore the degeneracies present between the effects of these different cosmological models on the abundance and distribution of substructure, as well as the distribution of matter inside host haloes in dark matter-only simulation. In general these models all show strong degeneracies in their effects, but in detail differences can be discerned. This pa [...]S Staffordwork_3cw5xeyakjevjejxd6gij4priuNon-standard signatures from Cosmic Microwave Background polarisation
https://scholar.archive.org/work/2e4yhf7gjvhlrbniwh5ievcgx4
Matteo Billiwork_2e4yhf7gjvhlrbniwh5ievcgx4Multiresolution HEALPix Maps for Multiwavelength and Multimessenger Astronomy
https://scholar.archive.org/work/fs67qphn7jeg5od43srcu2hqpq
HEALPix—the Hierarchical Equal Area isoLatitude Pixelization—has become a standard in high-energy and gravitational wave astronomy. Originally developed to improve the efficiency of all-sky Fourier analyses, it is now also utilized to share sky localization information. When used for this purpose the need for a homogeneous all-sky grid represents a limitation that hinders a broader community adoption. This work presents mhealpy, a Python library able to create, handle and analyze multiresolution maps, a solution to this problem. It supports efficient pixel querying, arithmetic operations between maps, adaptive mesh refinement, plotting, and serialization into FITS—Flexible Image Transport System—files. This HEALPix extension makes it suitable to represent highly resolved region, resulting in a convenient common format to share spatial information for joint multiwavelength and multimessenger analyses.I. Martinez-Castellanos, Leo P. Singer, E. Burns, Donggeun Tak, Alyson Joens, Judith L. Racusin, Jeremy S. Perkinswork_fs67qphn7jeg5od43srcu2hqpqE-B decomposition of CMB polarization using deep learning
https://scholar.archive.org/work/63v2vp3tmnhqdbajla6ezcxpe4
The polarization of the cosmic microwave background (CMB) can be split into two coordinate independent components: the gradient-like E-mode, and the curl-like B-mode. Primordial B-modes are of particular interest as they do not arise from scalar density perturbations and serve as a direct probe of primordial gravitational waves theorized to be generated during inflation. A direct detection of these elusive B-modes would help determine the energy scale of inflation and constrain possible inflationary models. However, the E-B decomposition of polarization on a partial or cut sky is non-unique and introduces modes that cannot conclusively be classified as pure E or B. This is a source of ambiguity for all CMB experiments probing polarization as a Galactic cut is required even for purported full-sky missions, such as the European Space Agency's (ESA) Planck mission. We present a map-based technique using machine learning (ML) methods to perform this partial sky decomposition. In particular, we use a deep residual convolutional neural network (CNN) based on the U-Net architecture to perform this decomposition on small patches of the sky 400 square degrees in area, allowing the targeting of regions with low Galactic foreground. Our deep residual U-Net performs exceptionally well at angular scales of a few degrees, corresponding to spherical harmonic Fourier modes l (ell) ≃ 50 to 110, a range of scales ideal for probing the recombination bump of the primordial B-mode power spectrum. Additionally, the map-based nature of our technique allows visual inspection of the E-B separation. This may be especially useful for identifying residual Galactic contamination in polarization data.Puranjay Rohan Gulatiwork_63v2vp3tmnhqdbajla6ezcxpe4Validation Solutions to the Full-Sky Radio Interferometry Measurement Equation for Diffuse Emission
https://scholar.archive.org/work/c253pmpjqvgo7azbie5nf4wc44
Low-frequency radio observatories are reaching unprecedented levels of sensitivity in an effort to detect the 21 cm signal from the Cosmic Dawn. High precision is needed because the expected signal is overwhelmed by foreground contamination, largely from so-called diffuse emission -- a non-localized glow comprising Galactic synchrotron emission and radio galaxies. The impact of this diffuse emission on observations may be better understood through detailed simulations, which evaluate the Radio Interferometry Measurement Equation (RIME) for a given instrument and sky model. Evaluating the RIME involves carrying out an integral over the full sky, which is naturally discretized for point sources but must be approximated for diffuse emission. The choice of integration scheme can introduce errors that must be understood and isolated from the instrumental effects under study. In this paper, we present several analytically-defined patterns of unpolarized diffuse sky emission for which the RIME integral is manageable, yielding closed-form or series visibility functions. We demonstrate the usefulness of these RIME solutions for validation by comparing them to simulated data, and show that the remaining differences behave as expected with varied sky resolution and baseline orientation and length.Adam E. Lanman, Steven G. Murray, Daniel C. Jacobswork_c253pmpjqvgo7azbie5nf4wc44Tue, 21 Dec 2021 00:00:00 GMTMulti-Resolution HEALPix Maps for Multi-Wavelength and Multi-Messenger Astronomy
https://scholar.archive.org/work/mesg7o57p5b53cw5h5siabhfv4
HEALPix -- the Hierarchical Equal Area isoLatitude Pixelization -- has become a standard in high-energy and gravitational wave astronomy. Originally developed to improve the efficiency of all-sky Fourier analyses, it is now also utilized to share sky localization information. When used for this purpose the need for a homogeneous all-sky grid represents a limitation that hinders a broader community adoption. This work presents mhealpy, a Python library able to create, handle and analyze multi-resolution maps, a solution to this problem. It supports efficient pixel querying, arithmetic operations between maps, adaptive mesh refinement, plotting and serialization into FITS -- Flexible Image Transport System -- files. This HEALPix extension makes it suitable to represent highly resolved regions, resulting in a convenient common format to share spatial information for joint multi-wavelength and multi-messenger analyses.I. Martinez-Castellanos, Leo P. Singer, E. Burns, D. Tak, Alyson Joens, Judith L. Racusin, Jeremy S. Perkinswork_mesg7o57p5b53cw5h5siabhfv4Mon, 22 Nov 2021 00:00:00 GMT