arXiv subjects

Anže Slosar

Publications and source records attributed to Anže Slosar.

At least 73 records · Page 4Linked to original sources

arXiv2020

Primordial Features from Linear to Nonlinear Scales

Sharp features in the primordial power spectrum are a powerful window into the inflationary epoch. To date, the cosmic microwave background (CMB) has offered the most sensitive avenue to search for these signatures. In this paper, we demonstrate the power of large-scale structure observations to surpass the CMB as a probe of primordial features. We show that the signatures in galaxy surveys can be separated from the broadband power spectrum and are as robust to the nonlinear evolution of matter as the standard baryon acoustic oscillations. As a result, analyses can exploit a significant range of scales beyond the linear regime available in the datasets. We develop a feature search for large-scale structure, apply it to the final data release of the Baryon Oscillation Spectroscopic Survey and find new bounds on oscillatory features that exceed the sensitivity of Planck for a significant range of frequencies. Moreover, we forecast that the next generation of galaxy surveys, such as DESI and Euclid, will be able to improve current constraints by up to an order of magnitude over an expanded frequency range.

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arXiv2020

Efficient identification of infected sub-population

When testing for infections, the standard method is to test each subject individually. If testing methodology is such that samples from multiple subjects can be efficiently combined and tested at once, yielding a positive results if any one subject in the subgroup is positive, then one can often identify the infected sub-population with a considerably lower number of tests compared to the number of test subjects. We present two such methods that allow an increase in testing efficiency (in terms of total number of test performed) by a factor of $\approx$ 10 if population infection rate is $10^{-2}$ and a factor of $\approx$50 when it is $10^{-3}$. Such methods could be useful when testing large fractions of the total population, as will be perhaps required during the current coronavirus pandemic.

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arXiv2020

Massive neutrinos and degeneracies in Lyman-alpha forest simulations

Using a suite of hydrodynamical simulations with cold dark matter, baryons, and neutrinos, we present a detailed study of the effect of massive neutrinos on the 1-D and 3-D flux power spectra of the Lyman-$α$ (Ly$α$) forest. The presence of massive neutrinos in cosmology induces a scale- and time-dependent suppression of structure formation that is strongest on small scales. Measuring this suppression is a key method for inferring neutrino masses from cosmological data, and is one of the main goals of ongoing and future surveys like eBOSS, DES, LSST, Euclid or DESI. The clustering in the Ly$α$ forest traces the quasi-linear power at late times and on small scales. In combination with observations of the cosmic microwave background, the forest therefore provides some of the tightest constraints on the sum of the neutrino masses. However there is a well-known degeneracy between $Σm_ν$ and the amplitude of perturbations in the linear matter power spectrum. We study the corresponding degeneracy in the 1-D flux power spectrum of the Ly$α$ forest, and for the first time also study this degeneracy in the 3-D flux power spectrum. We show that the non-linear effects of massive neutrinos on the Ly$α$ forest, beyond the effect of linear power amplitude suppression, are negligible, and this degeneracy persists in the Ly$α$ forest observables to a high precision. We discuss the implications of this degeneracy for choosing parametrisations of the Ly$α$ forest for cosmological analysis.

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arXiv2020

CMB-HD: Astro2020 RFI Response

CMB-HD is a proposed ultra-deep (0.5 uk-arcmin), high-resolution (15 arcseconds) millimeter-wave survey over half the sky that would answer many outstanding questions in both fundamental physics of the Universe and astrophysics. This survey would be delivered in 7.5 years of observing 20,000 square degrees, using two new 30-meter-class off-axis cross-Dragone telescopes to be located at Cerro Toco in the Atacama Desert. Each telescope would field 800,000 detectors (200,000 pixels), for a total of 1.6 million detectors.

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arXiv2020

Packed Ultra-wideband Mapping Array (PUMA): Astro2020 RFI Response

The Packed Ultra-wideband Mapping Array (PUMA) is a proposed low-resolution transit interferometric radio telescope operating over the frequency range 200 - 1100MHz. Its rich science portfolio will include measuring structure in the universe from redshift z = 0.3 to 6 using 21cm intensity mapping, detecting one million fast radio bursts, and monitoring thousands of pulsars. It will allow PUMA to advance science in three different areas of physics (the physics of dark energy, the physics of cosmic inflation and time-domain astrophysics). This document is a response to a request for information (RFI) by the Panel on Radio, Millimeter, and Submillimeter Observations from the Ground (RMS) of the Decadal Survey on Astronomy and Astrophysics 2020. We present the science case of PUMA, the development path and major risks to the project.

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arXiv2020

First Constraint on the Neutrino-Induced Phase Shift in the BAO Spectrum

The existence of the cosmic neutrino background is a fascinating prediction of the hot big bang model. These neutrinos were a dominant component of the energy density in the early universe and, therefore, played an important role in the evolution of cosmological perturbations. The energy density of the cosmic neutrino background has been measured using the abundances of light elements and the anisotropies of the cosmic microwave background (CMB). A complementary and more robust probe is a distinct shift in the temporal phase of sound waves in the primordial plasma which is produced by fluctuations in the neutrino density and has recently been detected in the CMB. In this paper, we report on the first constraint on this neutrino-induced phase shift in the spectrum of baryon acoustic oscillations (BAO) of the BOSS DR12 data. Constraining the acoustic scale using Planck data while marginalizing over the effects of neutrinos in the CMB, we find a non-zero phase shift at greater than 95\% confidence. We also demonstrate the robustness of this result in simulations and forecasts. Besides providing a new test of the cosmic neutrino background, our work is the first application of the BAO signal to early universe physics and a non-trivial confirmation of the standard cosmological history.

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arXiv2020

Cosmological constraints from galaxy-lensing cross correlations using BOSS galaxies with SDSS and CMB lensing

We present cosmological parameter constraints based on a joint modeling of galaxy-lensing cross correlations and galaxy clustering measurements in the SDSS, marginalizing over small-scale modeling uncertainties using mock galaxy catalogs, without explicit modeling of galaxy bias. We show that our modeling method is robust to the impact of different choices for how galaxies occupy dark matter halos and to the impact of baryonic physics (at the $\sim2\%$ level in cosmological parameters) and test for the impact of covariance on the likelihood analysis and of the survey window function on the theory computations. Applying our results to the measurements using galaxy samples from BOSS and lensing measurements using shear from SDSS galaxies and CMB lensing from Planck, with conservative scale cuts, we obtain $S_8\equiv\left(\frac{σ_8}{0.8228}\right)^{0.8}\left(\frac{Ω_m}{0.307}\right)^{0.6}=0.85\pm0.05$ (stat.) using LOWZ $\times$ SDSS galaxy lensing, and $S_8=0.91\pm0.1$ (stat.) using combination of LOWZ and CMASS $\times$ Planck CMB lensing. We estimate the systematic uncertainty in the galaxy-galaxy lensing measurements to be $\sim6\%$ (dominated by photometric redshift uncertainties) and in the galaxy-CMB lensing measurements to be $\sim3\%$, from small scale modeling uncertainties including baryonic physics.

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arXiv2019

Tomographic galaxy clustering with the Subaru Hyper Suprime-Cam first year public data release

We analyze the clustering of galaxies in the first public data release of the HSC Subaru Strategic Program. Despite the relatively small footprints of the observed fields, the data are an excellent proxy for the deep photometric datasets that will be acquired by LSST, and are therefore an ideal test bed for the analysis methods being implemented by the LSST DESC. We select a magnitude limited sample with $i<24.5$ and analyze it in four redshift bins covering $0.15\lesssim z \lesssim1.5$. We carry out a Fourier-space analysis of the two-point clustering of this sample, including all auto- and cross-correlations. We demonstrate the use of map-level deprojection methods to account for fluctuations in the galaxy number density caused by observational systematics. Through an HOD analysis, we place constraints on the characteristic halo masses of this sample, finding a good fit up to scales $k_{\rm max}=1\,{\rm Mpc}^{-1}$, including both auto- and cross-correlations. Our results show monotonically decreasing average halo masses, which can be interpreted in terms of the drop-out of red galaxies at high redshifts for a flux-limited sample. In terms of photometric redshift systematics, we show that additional care is needed in order to marginalize over uncertainties in the redshift distribution in galaxy clustering, and that these uncertainties can be constrained by including cross-correlations. We are able to make a $\sim3σ$ detection of lensing magnification in the HSC data. Our results are stable to variations in $σ_8$ and $Ω_c$ and we find constraints that agree well with measurements from Planck and low-redshift probes. Finally, we use our pipeline to study the clustering of galaxies as a function of limiting flux, and provide a simple fitting function for the linear galaxy bias for magnitude limited samples as a function of limiting magnitude and redshift. [abridged]

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arXiv2019

Predicting CMB dust foreground using galactic 21 cm data

Understanding large-angular-scale galactic foregrounds is crucial for future CMB experiments aiming to detect $B$-mode polarization from primordial gravitational waves. Traditionally, the dust component has been separated using its different frequency dependence. However, using non-CMB observations has potential to increase fidelity and decrease the reconstruction noise. In this exploratory paper we investigate the capability of galactic 21 cm observations to predict the dust foreground in intensity. We train a neural network to predict the dust foreground as measured by the Planck Satellite from the full velocity data-cube of galactic 21 cm emission as measured by the HI4PI survey. We demonstrate that information in the velocity structure clearly improves the predictive power over both a simple integrated emission model and a simple linear model. The improvement is significant at arc-minute scales but more modest at degree scales. This proof of principle on temperature data indicates that it might also be possible to improve foreground polarization templates from the same input data.

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arXiv2019

The one-dimensional power spectrum from the SDSS DR14 Ly$α$ forests

We present a measurement of the 1D Ly$α$ forest flux power spectrum, using the complete Baryon Oscillation Spectroscopic Survey (BOSS) and first extended-BOSS (eBOSS) quasars at $z_{\rm qso}>2.1$, corresponding to the fourteenth data release (DR14) of the Sloan Digital Sky Survey (SDSS). Our results cover thirteen bins in redshift from $z_{\rm Lyα}=2.2$ to 4.6, and scales up to $k=0.02\rm \,(km/s)^{-1}$. From a parent sample of 180,413 visually inspected spectra, we selected the 43,751 quasars with the best quality; this data set improves the previous result from the ninth data release (DR9), both in statistical precision (achieving a reduction by a factor of two) and in redshift coverage. We also present a thorough investigation of identified sources of systematic uncertainties that affect the measurement. The resulting 1D power spectrum of this work is in excellent agreement with the one from the BOSS DR9 data.

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arXiv2019

Baryon acoustic oscillations at z = 2.34 from the correlations of Ly$α$ absorption in eBOSS DR14

We measure the imprint of primordial baryon acoustic oscillations (BAO) in the correlation function of Ly$α$ absorption in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) and the extended BOSS (eBOSS) in Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS)-IV. In addition to 179,965 spectra with absorption in the Lyman-$α$ (Ly$α$) region, we use, for the first time, Ly$α$ absorption in the Lyman-$β$ region of 56,154 spectra. We measure the Hubble distance, $D_H$, and the comoving angular diameter distance, $D_M$, relative to the sound horizon at the drag epoch $r_d$ at an effective redshift $z=2.34$. Using a physical model of the correlation function outside the BAO peak, we find $D_H(2.34)/r_d=8.86\pm 0.29$ and $D_M(2.34)/r_d=37.41\pm 1.86$, within 1$σ$ from the flat-$Λ$CDM model consistent with CMB anisotropy measurements. With the addition of polynomial "broadband" terms, the results remain within one standard deviation of the CMB-inspired model. Combined with the quasar-Ly$α$ cross-correlation measurement presented in a companion paper Blomqvist19, the BAO measurements at $z=2.35$ are within 1.7$σ$ of the predictions of this model.

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arXiv2019

Baryon acoustic oscillations from the cross-correlation of Ly$α$ absorption and quasars in eBOSS DR14

We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift $z=2.35$ from the three-dimensional correlation of Lyman-$α$ (Ly$α$) forest absorption and quasars. The study uses 266,590 quasars in the redshift range $1.77<z<3.5$ from the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). The sample includes the first two years of observations by the SDSS-IV extended Baryon Oscillation Spectroscopic Survey (eBOSS), providing new quasars and re-observations of BOSS quasars for improved statistical precision. Statistics are further improved by including Ly$α$ absorption occurring in the Ly$β$ wavelength band of the spectra. From the measured BAO peak position along and across the line of sight, we determined the Hubble distance $D_{H}$ and the comoving angular diameter distance $D_{M}$ relative to the sound horizon at the drag epoch $r_{d}$: $D_{H}(z=2.35)/r_{d}=9.20\pm 0.36$ and $D_{M}(z=2.35)/r_{d}=36.3\pm 1.8$. These results are consistent at $1.5σ$ with the prediction of the best-fit spatially-flat cosmological model with the cosmological constant reported for the Planck (2016) analysis of cosmic microwave background anisotropies. Combined with the Ly$α$ auto-correlation measurement presented in a companion paper, the BAO measurements at $z=2.34$ are within $1.7σ$ of the predictions of this model.

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arXiv2019

Inflation and Early Dark Energy with a Stage II Hydrogen Intensity Mapping Experiment

This white paper envisions a revolutionary post-DESI, post-LSST dark energy program based on intensity mapping of the redshifted 21cm emission line from neutral hydrogen at radio frequencies. The proposed intensity mapping survey has the unique capability to quadruple the volume of the Universe surveyed by optical programs, provide a percent-level measurement of the expansion history to $z \sim 6$, open a window to explore physics beyond the concordance $Λ$CDM model, and to significantly improve the precision on standard cosmological parameters. In addition, characterization of dark energy and new physics will be powerfully enhanced by cross-correlations with optical surveys and cosmic microwave background measurements. The rich dataset obtained by the proposed intensity mapping instrument will be simultaneously useful in exploring the time-domain physics of fast radio transients and pulsars, potentially in live "multi-messenger" coincidence with other observatories. The core dark energy/inflation science advances enabled by this program are the following: (i) Measure the expansion history of the universe over $z=0.3-6$ with a single instrument, extending the range deep into the pre-acceleration era, providing an unexplored window for new physics; (ii) Measure the growth rate of structure in the universe over the same redshift range; (iii) Observe, or constrain, the presence of inflationary relics in the primordial power spectrum, improving existing constraints by an order of magnitude; (iv) Observe, or constrain, primordial non-Gaussianity with unprecedented precision, improving constraints on several key numbers by an order of magnitude. Detailed mapping of the enormous, and still largely unexplored, volume of cosmic space will thus provide unprecedented information on fundamental questions of the vacuum energy and early-universe physics.

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arXiv2019

Packed Ultra-wideband Mapping Array (PUMA): A Radio Telescope for Cosmology and Transients

PUMA is a proposal for an ultra-wideband, low-resolution and transit interferometric radio telescope operating at $200-1100\,\mathrm{MHz}$. Its design is driven by six science goals which span three science themes: the physics of dark energy (measuring the expansion history and growth of the universe up to $z=6$), the physics of inflation (constraining primordial non-Gaussianity and primordial features) and the transient radio sky (detecting one million fast radio bursts and following up SKA-discovered pulsars). We propose two array configurations composed of hexagonally close-packed 6m dish arrangements with 50% fill factor. The initial 5,000 element 'petite array' is scientifically compelling, and can act as a demonstrator and a stepping stone to the full 32,000 element 'full array'. Viewed as a 21cm intensity mapping telescope, the program has the noise equivalent of a traditional spectroscopic galaxy survey comprised of 0.6 and 2.5 billion galaxies at a comoving wavenumber of $k=0.5\,h\mathrm{Mpc}^{-1}$ spanning the redshift range $z = 0.3 - 6$ for the petite and full configurations, respectively. At redshifts beyond $z=2$, the 21cm technique is a uniquely powerful way of mapping the universe, while the low-redshift range will allow for numerous cross-correlations with existing and upcoming surveys. This program is enabled by the development of ultra-wideband radio feeds, cost-effective dish construction methods, commodity radio-frequency electronics driven by the telecommunication industry and the emergence of sufficient computing power to facilitate real-time signal processing that exploits the full potential of massive radio arrays. The project has an estimated construction cost of 55 and 330 million FY19 USD for the petite and full array configurations. Including R&D, design, operations and science analysis, the cost rises to 125 and 600 million FY19 USD, respectively.

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arXiv2019

Research and Development for HI Intensity Mapping

Development of the hardware, data analysis, and simulation techniques for large compact radio arrays dedicated to mapping the 21 cm line of neutral hydrogen gas has proven to be more difficult than imagined twenty years ago when such telescopes were first proposed. Despite tremendous technical and methodological advances, there are several outstanding questions on how to optimally calibrate and analyze such data. On the positive side, it has become clear that the outstanding issues are purely technical in nature and can be solved with sufficient development activity. Such activity will enable science across redshifts, from early galaxy evolution in the pre-reionization era to dark energy evolution at low redshift.

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arXiv2019

SpecTel: A 10-12 meter class Spectroscopic Survey Telescope

We recommend a conceptual design study for a spectroscopic facility in the southern hemisphere comprising a large diameter telescope, fiber system, and spectrographs collectively optimized for massively-multiplexed spectroscopy. As a baseline, we propose an 11.4-meter aperture, optical spectroscopic survey telescope with a five square degree field of view. Using current technologies, the facility could be equipped with 15,000 robotically-controlled fibers feeding spectrographs over 360<lambda<1330 nm with options for fiber-fed spectrographs at high resolution and a panoramic IFU at a separate focus. This would enable transformational progress via its ability to access a larger fraction of objects from Gaia, LSST, Euclid, and WFIRST than any currently funded or planned spectroscopic facility. An ESO-sponsored study (arXiv:1701.01976) discussed the scientific potential in ambitious new spectroscopic surveys in Galactic astronomy, extragalactic astronomy, and cosmology. The US community should establish links with European and other international communities to plan for such a powerful facility and maximize the potential of large aperture multi-object spectroscopy given the considerable investment in deep imaging surveys.

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arXiv2019

The extended Baryon Oscillation Spectroscopic Survey: measuring the cross-correlation between the MgII flux transmission field and quasars and galaxies at $z=0.59$

We present the first attempt at measuring the baryonic acoustic oscillations (BAO) in the large scale cross-correlation between the magnesium-II doublet (MgII) flux transmission field and the position of quasar and galaxy tracers. The MgII flux transmission continuous field at $0.3 < z < 1.6$ is measured from 500,589 quasar spectra obtained in the Baryonic Oscillation Spectroscopic Survey (BOSS) and the extended BOSS (eBOSS). The position of 246,697 quasar tracers and 1,346,776 galaxy tracers are extracted from the Sloan Digital Sky Survey (SDSS) I, II, BOSS and eBOSS catalogs. In addition to measuring the cosmological BAO scale and the biased matter density correlation, this study allows tests and improvements to cosmological Lyman-$α$ analyses. A feature consistent with that of the BAO is detected at a significance of $Δχ^{2} = 7.25$. The measured MgII linear transmission bias parameters are $b_{\mathrm{MgII(2796)}} (z = 0.59) = (-6.82 \pm 0.54) \, \times 10^{-4}$ and $b_{\mathrm{MgII(2804)}} (z = 0.59) = (-5.55 \pm 0.46) \, \times 10^{-4}$, and the MgI bias is $b_{\mathrm{MgI(2853)}} (z = 0.59) = (-1.48 \pm 0.24) \, \times 10^{-4}$. Their redshift evolution is characterized by the power-law index: $γ_{\mathrm{Mg}} = 3.36 \pm 0.46$. These measurements open a new window towards using BAO from flux transmission at $z < 1$ in the final eBOSS sample and in the upcoming sample from the Dark Energy Spectroscopic Instrument.

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arXiv2019

Synergies between radio, optical and microwave observations at high redshift

We study synergies between three promising methods to measure $2 2$ and suffer from interloper problems even for spectroscopic surveys. Intensity mapping of the 21-cm signal can cover large volumes with exquisite fidelity, but is limited both by loss of information to foreground cleaning and by lack of knowledge of the mean signal. Cosmic microwave background (CMB) lensing is theoretically very clean, but ultimately measures just the projected variations in density. We find that cross-correlation between optical and radio can significantly improve the measurement of growth rate. Combining these with the CMB provides a promising avenue to detecting modified gravity at high redshifts, in particular by independently probing the Weyl and Newtonian potentials and by strengthening control of systematics. We find that cross-correlating a Stage {\sc ii} 21-cm survey with DESI quasars with a reasonable brightness temperature prior could enable measurements of the growth rate $fσ_8$ at sub 3\% and sub 8\% levels at $z = 3, 4$, representing a factor of 4 and 8 improvement over constraints obtainable from DESI quasars alone. Similarly, cross-correlating 21-cm data with a futuristic LBG survey to $m_{UV}<24.5$ over 1000 square degrees will make possible $fσ_8$ measurements at close to 1\% at $z = 3$ and 3\% at $z = 4$, and improve similar constraints at $z = 5$ by close to a factor of 3 to sub-10\% precision. Combining the above with CMB lensing from a Stage 4 CMB survey and LSST data can additionally constrain the gravitational slip $γ$ parameter to similar precision at these redshifts, enabling us to test the predictions of general relativity at large scales.

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