Showing papers by "Risa H. Wechsler published in 2022"

Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument

Abstract: The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z > 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii] doublet at 8 × 10−17 erg s−1 cm−2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.

Consistent lensing and clustering in a low-S8 Universe with BOSS, DES Year 3, HSC Year 1 and KiDS-1000

Abstract: We evaluate the consistency between lensing and clustering based on measurements from BOSS combined with galaxy–galaxy lensing from DES-Y3, HSC-Y1, KiDS-1000. We find good agreement between these lensing datasets. We model the observations using the Dark Emulator and fit the data at two fixed cosmologies: Planck (S8 = 0.83), and a Lensing cosmology (S8 = 0.76). For a joint analysis limited to large scales, we find that both cosmologies provide an acceptable fit to the data. Full utilisation of the higher signal–to–noise small-scale measurements is hindered by uncertainty in the impact of baryon feedback and assembly bias, which we account for with a reasoned theoretical error budget. We incorporate a systematic inconsistency parameter for each redshift bin, A, that decouples the lensing and clustering. With a wide range of scales, we find different results for the consistency between the two cosmologies. Limiting the analysis to the bins for which the impact of the lens sample selection is expected to be minimal, for the Lensing cosmology, the measurements are consistent with A=1; A = 0.91 ± 0.04 (A = 0.97 ± 0.06) using DES+KiDS (HSC). For the Planck case, we find a discrepancy: A = 0.79 ± 0.03 (A = 0.84 ± 0.05) using DES+KiDS (HSC). We demonstrate that a kSZ-based estimate for baryonic effects alleviates some of the discrepancy in the Planck cosmology. This analysis demonstrates the statistical power of small-scale measurements, but caution is still warranted given modelling uncertainties and foreground sample selection effects.

Stringent σ8 constraints from small-scale galaxy clustering using a hybrid MCMC+emulator framework

Abstract: We present a novel simulation-based hybrid emulator approach that maximally derives cosmological and Halo Occupation Distribution (HOD) information from non-linear galaxy clustering, with sufficient precision for DESI Year 1 (Y1) analysis. Our hybrid approach first samples the HOD space on a fixed cosmological simulation grid to constrain the high-likelihood region of cosmology+HOD parameter space, and then constructs the emulator within this constrained region. This approach significantly reduces the parameter volume emulated over, thus achieving much smaller emulator errors with fixed number of training points. We demonstrate that this combined with state-of-the-art simulations result in tight emulator errors comparable to expected DESI Y1 LRG sample variance. We leverage the new AbacusSummit simulations and apply our hybrid approach to CMASS non-linear galaxy clustering data. We infer constraints on σ8 = 0.762 ± 0.024 and fσ8(zeff = 0.52) = 0.444 ± 0.016, the tightest among contemporary galaxy clustering studies. We also demonstrate that our fσ8 constraint is robust against secondary biases and other HOD model choices, a critical first step towards showcasing the robust cosmology information accessible in non-linear scales. We speculate that the additional statistical power of DESI Y1 should tighten the growth rate constraints by at least another 50-60$\%$, significantly elucidating any potential tension with Planck. We also address the “lensing is low” tension, which we find to be in the same direction as a potential tension in fσ8. We show that the combined effect of a lower fσ8 and environment-based bias accounts for approximately $50\%$ of the discrepancy.

Target Selection and Validation of DESI Luminous Red Galaxies

Abstract: The Dark Energy Spectroscopic Instrument (DESI) is carrying out a five-year survey that aims to measure the redshifts of tens of millions of galaxies and quasars, including 8 million luminous red galaxies (LRGs) in the redshift range 0.4 < z ≲ 1.0. Here we present the selection of the DESI LRG sample and assess its spectroscopic performance using data from Survey Validation (SV) and the first two months of the Main Survey. The DESI LRG sample, selected using g, r, z, and W1 photometry from the DESI Legacy Imaging Surveys, is highly robust against imaging systematics. The sample has a target density of 605 deg−2 and a comoving number density of 5 × 10−4 h 3 Mpc−3 in 0.4 < z < 0.8; this is a significantly higher density than previous LRG surveys (such as SDSS, BOSS, and eBOSS) while also extending to z ∼ 1. After applying a bright star veto mask developed for the sample, 98.9% of the observed LRG targets yield confident redshifts (with a catastrophic failure rate of 0.2% in the confident redshifts), and only 0.5% of the LRG targets are stellar contamination. The LRG redshift efficiency varies with source brightness and effective exposure time, and we present a simple model that accurately characterizes this dependence. In the appendices, we describe the extended LRG samples observed during SV.

Snowmass2021 Cosmic Frontier White Paper: Dark Matter Physics from Halo Measurements

Abstract: The non-linear process of cosmic structure formation produces gravitationally bound overdensities of dark matter known as halos. The abundances, density profiles, ellipticities, and spins of these halos can be tied to the underlying fundamental particle physics that governs dark matter at microscopic scales. Thus, macroscopic measurements of dark matter halos offer a unique opportunity to determine the underlying properties of dark matter across the vast landscape of dark matter theories. This white paper summarizes the ongoing rapid development of theoretical and experimental methods, as well as new opportunities, to use dark matter halo measurements as a pillar of dark matter physics.

Milky Way Satellite Census. IV. Constraints on Decaying Dark Matter from Observations of Milky Way Satellite Galaxies

Abstract: We use a recent census of the Milky Way (MW) satellite galaxy population to constrain the lifetime of particle dark matter (DM). We consider two-body decaying dark matter (DDM) in which a heavy DM particle decays with lifetime τ comparable to the age of the universe to a lighter DM particle (with mass splitting ϵ) and to a dark radiation species. These decays impart a characteristic “kick velocity,” V kick = ϵ c, on the DM daughter particles, significantly depleting the DM content of low-mass subhalos and making them more susceptible to tidal disruption. We fit the suppression of the present-day DDM subhalo mass function (SHMF) as a function of τ and V kick using a suite of high-resolution zoom-in simulations of MW-mass halos, and we validate this model on new DDM simulations of systems specifically chosen to resemble the MW. We implement our DDM SHMF predictions in a forward model that incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk using an empirical model for the galaxy–halo connection. By comparing to the observed MW satellite population, we conservatively exclude DDM models with τ < 18 Gyr (29 Gyr) for V kick = 20 kms−1 (40 kms−1) at 95% confidence. These constraints are among the most stringent and robust small-scale structure limits on the DM particle lifetime and strongly disfavor DDM models that have been proposed to alleviate the Hubble and S 8 tensions.

Dark energy survey year 3 results: cosmological constraints from the analysis of cosmic shear in harmonic space

Abstract: We present cosmological constraints from the analysis of angular power spectra of cosmic shear maps based on data from the first three years of observations by the Dark Energy Survey (DES Y3). Our measurements are based on the pseudo-Cℓmethod and complement the analysis of the two-point correlation functions in real space, as the two estimators are known to compress and select Gaussian information in different ways, due to scale cuts. They may also be differently affected by systematic effects and theoretical uncertainties, making this analysis an important cross-check. Using the same fiducial ΛCDMmodel as in the DES Y3 real-space analysis, we find ${S_8 \equiv \sigma _8 \sqrt{\Omega _{\rm m}/0.3} = 0.793^{+0.038}_{-0.025}}$, which further improves to S8 = 0.784 ± 0.026 when including shear ratios. This result is within expected statistical fluctuations from the real-space constraint, and in agreement with DES Y3 analyses of non-Gaussian statistics, but favors a slightly higher value of S8, which reduces the tension with the Planck2018 constraints from 2.3 σ in the real space analysis to 1.5 σ here. We explore less conservative intrinsic alignments models than the one adopted in our fiducial analysis, finding no clear preference for a more complex model. We also include small scales, using an increased Fourier mode cut-off up to kmax = 5 h Mpc−1, which allows to constrain baryonic feedback while leaving cosmological constraints essentially unchanged. Finally, we present an approximate reconstruction of the linear matter power spectrum at present time, found to be about 20 per cent lower than predicted by Planck2018, as reflected by the lower S8 value.

The Aemulus Project. V. Cosmological Constraint from Small-scale Clustering of BOSS Galaxies

Abstract: We analyze clustering measurements of BOSS galaxies using a simulation-based emulator of two-point statistics. We focus on the monopole and quadrupole of the redshift-space correlation function, and the projected correlation function, at scales of 0.1 ∼ 60 h −1 Mpc. Although our simulations are based on wCDM with general relativity (GR), we include a scaling parameter of the halo velocity field, γ f , defined as the amplitude of the halo velocity field relative to the GR prediction. We divide the BOSS data into three redshift bins. After marginalizing over other cosmological parameters, galaxy bias parameters, and the velocity scaling parameter, we find f σ 8(z = 0.25) = 0.413 ± 0.031, f σ 8(z = 0.4) = 0.470 ± 0.026, and f σ 8(z = 0.55) = 0.396 ± 0.022. Compared with Planck observations using a flat Lambda cold dark matter model, our results are lower by 1.9σ, 0.3σ, and 3.4σ, respectively. These results are consistent with other recent simulation-based results at nonlinear scales, including weak lensing measurements of BOSS LOWZ galaxies, two-point clustering of eBOSS LRGs, and an independent clustering analysis of BOSS LOWZ. All these results are generally consistent with a combination of γf1/2σ8≈0.75 . We note, however, that the BOSS data is well fit assuming GR, i.e., γ f = 1. We cannot rule out an unknown systematic error in the galaxy bias model at nonlinear scales, but near-future data and modeling will enhance our understanding of the galaxy–halo connection, and provide a strong test of new physics beyond the standard model.

A Spectroscopic Road Map for Cosmic Frontier: DESI, DESI-II, Stage-5

Abstract: In this white paper, we present an experimental road map for spectroscopic experiments beyond DESI. DESI will be a transformative cosmological survey in the 2020s, mapping 40 million galaxies and quasars and capturing a significant fraction of the available linear modes up to z = 1.2. DESI-II will pilot observations of galaxies both at much higher densities and extending to higher redshifts. A Stage-5 experiment would build out those high-density and high-redshift observations, mapping hundreds of millions of stars and galaxies in three dimen-

From Images to Dark Matter: End-to-end Inference of Substructure from Hundreds of Strong Gravitational Lenses

Abstract: Constraining the distribution of small-scale structure in our universe allows us to probe alternatives to the cold dark matter paradigm. Strong gravitational lensing offers a unique window into small dark matter halos (<1010 M ⊙) because these halos impart a gravitational lensing signal even if they do not host luminous galaxies. We create large data sets of strong lensing images with realistic low-mass halos, Hubble Space Telescope (HST) observational effects, and galaxy light from HST’s COSMOS field. Using a simulation-based inference pipeline, we train a neural posterior estimator of the subhalo mass function (SHMF) and place constraints on populations of lenses generated using a separate set of galaxy sources. We find that by combining our network with a hierarchical inference framework, we can both reliably infer the SHMF across a variety of configurations and scale efficiently to populations with hundreds of lenses. By conducting precise inference on large and complex simulated data sets, our method lays a foundation for extracting dark matter constraints from the next generation of wide-field optical imaging surveys.

Dark Energy Survey Year 3 results: Constraints on extensions to ΛCDM with weak lensing and galaxy clustering

Abstract: We constrain extensions to the $\Lambda$CDM model using measurements from the Dark Energy Survey's first three years of observations and external data. The DES data are the two-point correlation functions of weak gravitational lensing, galaxy clustering, and their cross-correlation. We use simulated data and blind analyses of real data to validate the robustness of our results. In many cases, constraining power is limited by the absence of nonlinear predictions that are reliable at our required precision. The models are: dark energy with a time-dependent equation of state, non-zero spatial curvature, sterile neutrinos, modifications of gravitational physics, and a binned $\sigma_8(z)$ model which serves as a probe of structure growth. For the time-varying dark energy equation of state evaluated at the pivot redshift we find $(w_{\rm p}, w_a)= (-0.99^{+0.28}_{-0.17},-0.9\pm 1.2)$ at 68% confidence with $z_{\rm p}=0.24$ from the DES measurements alone, and $(w_{\rm p}, w_a)= (-1.03^{+0.04}_{-0.03},-0.4^{+0.4}_{-0.3})$ with $z_{\rm p}=0.21$ for the combination of all data considered. Curvature constraints of $\Omega_k=0.0009\pm 0.0017$ and effective relativistic species $N_{\rm eff}=3.10^{+0.15}_{-0.16}$ are dominated by external data. For massive sterile neutrinos, we improve the upper bound on the mass $m_{\rm eff}$ by a factor of three compared to previous analyses, giving 95% limits of $(\Delta N_{\rm eff},m_{\rm eff})\leq (0.28, 0.20\, {\rm eV})$. We also constrain changes to the lensing and Poisson equations controlled by functions $\Sigma(k,z) = \Sigma_0 \Omega_{\Lambda}(z)/\Omega_{\Lambda,0}$ and $\mu(k,z)=\mu_0 \Omega_{\Lambda}(z)/\Omega_{\Lambda,0}$ respectively to $\Sigma_0=0.6^{+0.4}_{-0.5}$ from DES alone and $(\Sigma_0,\mu_0)=(0.04\pm 0.05,0.08^{+0.21}_{-0.19})$ for the combination of all data. Overall, we find no significant evidence for physics beyond $\Lambda$CDM.

Joint analysis of Dark Energy Survey Year 3 data and CMB lensing from SPT and Planck . III. Combined cosmological constraints

Abstract: We present cosmological constraints from the analysis of two-point correlation functions between galaxy positions and galaxy lensing measured in Dark Energy Survey (DES) Year 3 data and measurements of cosmic microwave background (CMB) lensing from the South Pole Telescope (SPT) and Planck. When jointly analyzing the DES-only two-point functions and the DES cross-correlations with SPT+Planck CMB lensing, we find $\Omega_{\rm m} = 0.344\pm 0.030$ and $S_8 \equiv \sigma_8 (\Omega_{\rm m}/0.3)^{0.5} = 0.773\pm 0.016$, assuming $\Lambda$CDM. When additionally combining with measurements of the CMB lensing autospectrum, we find $\Omega_{\rm m} = 0.306^{+0.018}_{-0.021}$ and $S_8 = 0.792\pm 0.012$. The high signal-to-noise of the CMB lensing cross-correlations enables several powerful consistency tests of these results, including comparisons with constraints derived from cross-correlations only, and comparisons designed to test the robustness of the galaxy lensing and clustering measurements from DES. Applying these tests to our measurements, we find no evidence of significant biases in the baseline cosmological constraints from the DES-only analyses or from the joint analyses with CMB lensing cross-correlations. However, the CMB lensing cross-correlations suggest possible problems with the correlation function measurements using alternative lens galaxy samples, in particular the redMaGiC galaxies and high-redshift MagLim galaxies, consistent with the findings of previous studies. We use the CMB lensing cross-correlations to identify directions for further investigating these problems.

The DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation

Abstract: Over the next 5 yr, the Dark Energy Spectroscopic Instrument (DESI) will use 10 spectrographs with 5000 fibers on the 4 m Mayall Telescope at Kitt Peak National Observatory to conduct the first Stage IV dark energy galaxy survey. At z < 0.6, the DESI Bright Galaxy Survey (BGS) will produce the most detailed map of the universe during the dark-energy-dominated epoch with redshifts of >10 million galaxies spanning 14,000 deg2. In this work, we present and validate the final BGS target selection and survey design. From the Legacy Surveys, BGS will target an r < 19.5 mag limited sample (BGS Bright), a fainter 19.5 < r < 20.175 color-selected sample (BGS Faint), and a smaller low-z quasar sample. BGS will observe these targets using exposure times scaled to achieve homogeneous completeness and cover the footprint three times. We use observations from the Survey Validation programs conducted prior to the main survey along with simulations to show that BGS can complete its strategy and make optimal use of “bright” time. BGS targets have stellar contamination <1%, and their densities do not depend strongly on imaging properties. BGS Bright will achieve >80% fiber assignment efficiency. Finally, BGS Bright and BGS Faint will achieve >95% redshift success over any observing condition. BGS meets the requirements for an extensive range of scientific applications. BGS will yield the most precise baryon acoustic oscillation and redshift-space distortion measurements at z < 0.4. It presents opportunities for new methods that require highly complete and dense samples (e.g., N-point statistics, multitracers). BGS further provides a powerful tool to study galaxy populations and the relations between galaxies and dark matter.

Optical selection bias and projection effects in stacked galaxy cluster weak lensing

Abstract: Cosmological constraints from current and upcoming galaxy cluster surveys are limited by the accuracy of cluster mass calibration. In particular, optically identified galaxy clusters are prone to selection effects that can bias the weak lensing mass calibration. We investigate the selection bias of the stacked cluster lensing signal associated with optically selected clusters, using clusters identified by the redMaPPer algorithm in the Buzzard simulations as a case study. We find that at a given cluster halo mass, the residuals of redMaPPer richness and weak lensing signal are positively correlated. As a result, for a given richness selection, the stacked lensing signal is biased high compared with what we would expect from the underlying halo mass probability distribution. The cluster lensing selection bias can thus lead to overestimated mean cluster mass and biased cosmology results. We show that the lensing selection bias exhibits a strong scale-dependence and is approximately 20 – 60% for ΔΣ at large scales. This selection bias largely originates from spurious member galaxies within ±20 – 60 $h^{-1} \rm Mpc$ along the line of sight, highlighting the importance of quantifying projection effects associated with the broad redshift distribution of member galaxies in photometric cluster surveys. While our results qualitatively agree with those in the literature, accurate quantitative modelling of the selection bias is needed to achieve the goals of cluster lensing cosmology and will require synthetic catalogues covering a wide range of galaxy–halo connection models.

DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of Our Nearest Neighbor

Abstract: We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the 11,416 sources studied in 3.75 hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars ([Fe/H] > − 0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be log10MNFW(<125kpc)/M⊙=11.80−0.10+0.12 . The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies.

Snowmass2021 Theory Frontier White Paper: Data-Driven Cosmology

Abstract: Over the past few decades, astronomical and cosmological data sets firmly established the existence of physics beyond the Standard Model of particle physics by providing strong evidence for the existence of dark matter, dark energy, and non-zero neutrino mass. In addition, the generation of primordial perturbations most likely also relies on physics beyond the Standard Model of particle physics. Theory work, ranging from models of the early universe in string theory that that led to novel phenomenological predictions to the development of effective field theories to large-scale cosmological simulations that include the physics of galaxy evolution, has played a key role in analyzing and interpreting these data sets and in suggesting novel paths forward to isolate the origins of this new physics. Over the next decade, even more sensitive surveys are beginning to take data and are being planned. In this white paper, we describe key areas of the theory program that will be needed to optimize the physics return on investment from these new observational opportunities.

The MegaMapper: A Stage-5 Spectroscopic Instrument Concept for the Study of Inflation and Dark Energy

Abstract: In this white paper, we present the MegaMapper concept. The MegaMapper is a proposed ground-based experiment to measure Inflation parameters and Dark Energy from galaxy redshifts at 2 < z < 5 . In order to achieve path-breaking results with a mid-scale investment, the MegaMapper combines existing tech-nologies for critical path elements and pushes innovative development in other design areas. To this aim, we envision a 6.5-m Magellan-like telescope, with a newly designed wide field, coupled with DESI spectrographs, and small-pitch robots to achieve multiplexing of 26,100. This will match the expected achiev-able target density in the redshift range of interest and provide a 15x capability over the existing state-of the art, without a 15x increase in project budget.

Snowmass2021: Vera C. Rubin Observatory as a Flagship Dark Matter Experiment

Abstract: Yao-Yuan Mao1, Annika H. G. Peter2, Susmita Adhikari3,4, Keith Bechtol5, Simeon Bird6, Simon Birrer7, Jonathan Blazek8, Jeffrey L. Carlin9, Nushkia Chamba10, Johann Cohen-Tanugi11,12, Francis-Yan Cyr-Racine13, Tansu Daylan14,15, Birendra Dhanasingham13, Alex Drlica-Wagner3,16,17, Cora Dvorkin18, Christopher Fassnacht19, Eric Gawiser1, Maurizio Giannotti20, Vera Gluscevic21, Alma Gonzalez-Morales22,23, Renée Hložek24, M. James Jee19,25, Stacy Kim26, Akhtar Mahmood27, Rachel Mandelbaum28, Siddharth Mishra-Sharma18,29,30, Marc Moniez31, Ethan O. Nadler21,32, Chanda Prescod-Weinstein33, J. Anthony Tyson19, Risa H. Wechsler7,34, Hai-Bo Yu6, and Gabrijela Zaharijas35

Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck II: Cross-correlation measurements and cosmological constraints

Abstract: C. Chang,1, 2 Y. Omori,1, 2, 3, 4 E. J. Baxter,5 C. Doux,6 A. Choi,7 S. Pandey,6 A. Alarcon,8 O. Alves,9, 10 A. Amon,4 F. Andrade-Oliveira,9 K. Bechtol,11 M. R. Becker,8 G. M. Bernstein,6 F. Bianchini,3, 4, 12 J. Blazek,13, 14 L. E. Bleem,8, 2 H. Camacho,15, 10 A. Campos,16 A. Carnero Rosell,10, 17, 18 M. Carrasco Kind,19, 20 R. Cawthon,21 R. Chen,22 J. Cordero,23 T. M. Crawford,1, 2 M. Crocce,24, 25 C. Davis,4 J. DeRose,26 S. Dodelson,16, 27 A. Drlica-Wagner,1, 2, 28 K. Eckert,6 T. F. Eifler,29, 30 F. Elsner,31 J. Elvin-Poole,32, 33 S. Everett,34 X. Fang,29, 35 A. Ferté,30 P. Fosalba,24, 25 O. Friedrich,36 M. Gatti,6 G. Giannini,37 D. Gruen,38 R. A. Gruendl,19, 20 I. Harrison,23, 39, 40 K. Herner,28 H. Huang,29, 41 E. M. Huff,30 D. Huterer,9 M. Jarvis,6 A. Kovacs,17, 18 E. Krause,29 N. Kuropatkin,28 P.-F. Leget,4 P. Lemos,31, 42 A. R. Liddle,43 N. MacCrann,44 J. McCullough,4 J. Muir,45 J. Myles,3, 4, 46 A. Navarro-Alsina,47 Y. Park,48 A. Porredon,32, 33 J. Prat,1, 2 M. Raveri,6 R. P. Rollins,23 A. Roodman,4, 46 R. Rosenfeld,10, 49 A. J. Ross,32 E. S. Rykoff,4, 46 C. Sánchez,6 J. Sanchez,28 L. F. Secco,2 I. Sevilla-Noarbe,50 E. Sheldon,51 T. Shin,6 M. A. Troxel,22 I. Tutusaus,24, 25, 52 T. N. Varga,53, 54 N. Weaverdyck,9, 26 R. H. Wechsler,3, 4, 46 W. L. K. Wu,4, 46 B. Yanny,28 B. Yin,16 Y. Zhang,28 J. Zuntz,55 T. M. C. Abbott,56 M. Aguena,10 S. Allam,28 J. Annis,28 D. Bacon,57 B. A. Benson,1, 2, 28 E. Bertin,58, 59 S. Bocquet,60 D. Brooks,31 D. L. Burke,4, 46 J. E. Carlstrom,1, 2, 8, 61, 62 J. Carretero,37 C. L. Chang,1, 2, 8 R. Chown,63, 64 M. Costanzi,65, 66, 67 L. N. da Costa,10, 68 A. T. Crites,1, 2, 69 M. E. S. Pereira,70 T. de Haan,71, 72 J. De Vicente,50 S. Desai,73 H. T. Diehl,28 M. A. Dobbs,74, 75 P. Doel,31 W. Everett,76 I. Ferrero,77 B. Flaugher,28 D. Friedel,19 J. Frieman,2, 28 J. García-Bellido,78 E. Gaztanaga,24, 25 E. M. George,79, 72 T. Giannantonio,36, 80 N. W. Halverson,76, 81 S. R. Hinton,82 G. P. Holder,20, 75, 83 D. L. Hollowood,34 W. L. Holzapfel,72 K. Honscheid,32, 33 J. D. Hrubes,84 D. J. James,85 L. Knox,86 K. Kuehn,87, 88 O. Lahav,31 A. T. Lee,26, 72 M. Lima,10, 89 D. Luong-Van,84 M. March,6 J. J. McMahon,1, 2, 61, 62 P. Melchior,90 F. Menanteau,19, 20 S. S. Meyer,1, 2, 61, 62 R. Miquel,37, 91 L. Mocanu,1, 2 J. J. Mohr,60, 92, 93 R. Morgan,11 T. Natoli,1, 2 S. Padin,1, 2, 94 A. Palmese,35 F. Paz-Chinchón,19, 80 A. Pieres,10, 68 A. A. Plazas Malagón,90 C. Pryke,95 C. L. Reichardt,12 M. Rodríguez-Monroy,50 A. K. Romer,42 J. E. Ruhl,96 E. Sanchez,50 K. K. Schaffer,2, 61, 97 M. Schubnell,9 S. Serrano,24, 25 E. Shirokoff,1, 2 M. Smith,98 Z. Staniszewski,96, 30 A. A. Stark,99 E. Suchyta,100 G. Tarle,9 D. Thomas,57 C. To,32 J. D. Vieira,20, 83 J. Weller,53, 54 and R. Williamson101, 1, 2

Joint analysis of Dark Energy Survey Year 3 data and CMB lensing from SPT and Planck . II. Cross-correlation measurements and cosmological constraints

Abstract: Cross-correlations of galaxy positions and galaxy shears with maps of gravitational lensing of the cosmic microwave background (CMB) are sensitive to the distribution of large-scale structure in the Universe. Such cross-correlations are also expected to be immune to some of the systematic effects that complicate correlation measurements internal to galaxy surveys. We present measurements and modeling of the cross-correlations between galaxy positions and galaxy lensing measured in the first three years of data from the Dark Energy Survey with CMB lensing maps derived from a combination of data from the 2500 deg$^2$ SPT-SZ survey conducted with the South Pole Telescope and full-sky data from the Planck satellite. The CMB lensing maps used in this analysis have been constructed in a way that minimizes biases from the thermal Sunyaev Zel'dovich effect, making them well suited for cross-correlation studies. The total signal-to-noise of the cross-correlation measurements is 23.9 (25.7) when using a choice of angular scales optimized for a linear (nonlinear) galaxy bias model. We use the cross-correlation measurements to obtain constraints on cosmological parameters. For our fiducial galaxy sample, which consist of four bins of magnitude-selected galaxies, we find constraints of $\Omega_{m} = 0.272^{+0.032}_{-0.052}$ and $S_{8} \equiv \sigma_8 \sqrt{\Omega_{m}/0.3}= 0.736^{+0.032}_{-0.028}$ ($\Omega_{m} = 0.245^{+0.026}_{-0.044}$ and $S_{8} = 0.734^{+0.035}_{-0.028}$) when assuming linear (nonlinear) galaxy bias in our modeling. Considering only the cross-correlation of galaxy shear with CMB lensing, we find $\Omega_{m} = 0.270^{+0.043}_{-0.061}$ and $S_{8} = 0.740^{+0.034}_{-0.029}$. Our constraints on $S_8$ are consistent with recent cosmic shear measurements, but lower than the values preferred by primary CMB measurements from Planck.

Report of the Topical Group on Cosmic Probes of Dark Matter for Snowmass 2021

Abstract: Cosmological and astrophysical observations currently provide the only robust, positive evidence for dark matter. Cosmic probes of dark matter, which seek to determine the fundamental properties of dark matter through observations of the cosmos, have emerged as a promising means to reveal the nature of dark matter. This report summarizes the current status and future potential of cosmic probes to inform our understanding of the fundamental nature of dark matter in the coming decade. ar X iv :2 20 9. 08 21 5v 3 [ he pph ] 1 4 D ec 2 02 2

Snowmass Theory Frontier: Astrophysics and Cosmology

Abstract: We summarize progress made in theoretical astrophysics and cosmology over the past decade and areas of interest for the coming decade. This Report is prepared as the TF09 “Astrophysics and Cosmology” topical group summary for the Theory Frontier as part of the Snowmass 2021 process.

Constraining the Baryonic Feedback with Cosmic Shear Using the DES Year-3 Small-Scale Measurements

Abstract: We use the small scales of the Dark Energy Survey (DES) Year-3 cosmic shear measurements, which are excluded from the DES Year-3 cosmological analysis, to constrain the baryonic feedback. To model the baryonic feedback, we adopt a baryonic correction model and use the numerical package Baccoemu to accelerate the evaluation of the baryonic nonlinear matter power spectrum. We design our analysis pipeline to focus on the constraints of the baryonic suppression effects, utilizing the implication given by a principal component analysis on the Fisher forecasts. Our constraint on the baryonic effects can then be used to better model and ameliorate the effects of baryons in producing cosmological constraints from the next generation large-scale structure surveys. We detect the baryonic suppression on the cosmic shear measurements with a ∼ 2 σ significance. The characteristic halo mass for which half of the gas is ejected by baryonic feedback is constrained to be M c > 10 13 . 2 h − 1 M (cid:12) (95% C.L.). The best-fit baryonic suppression is ∼ 5% at k = 1 . 0Mpc h − 1 and ∼ 15% at k = 5 . 0Mpc h − 1 . Our findings are robust with respect to the assumptions about the cosmological parameters, specifics of the baryonic model, and intrinsic alignments.

LINNA: Likelihood Inference Neural Network Accelerator

Abstract: Bayesian posterior inference of modern multi-probe cosmological analyses incurs massive computational costs. For instance, depending on the combinations of probes, a single posterior inference for the Dark Energy Survey (DES) data had a wall-clock time that ranged from 1 to 21 days using a state-of-the-art computing cluster with 100 cores. These computational costs have severe environmental impacts and the long wall-clock time slows scientific productivity. To address these difficulties, we introduce LINNA: the Likelihood Inference Neural Network Accelerator. Relative to the baseline DES analyses, LINNA reduces the computational cost associated with posterior inference by a factor of 8–50. If applied to the first-year cosmological analysis of Rubin Observatory's Legacy Survey of Space and Time (LSST Y1), we conservatively estimate that LINNA will save more than U.S. $300,000 on energy costs, while simultaneously reducing CO2 emission by 2,400 tons. To accomplish these reductions, LINNA automatically builds training data sets, creates neural network emulators, and produces a Markov chain that samples the posterior. We explicitly verify that LINNA accurately reproduces the first-year DES (DES Y1) cosmological constraints derived from a variety of different data vectors with our default code settings, without needing to retune the algorithm every time. Further, we find that LINNA is sufficient for enabling accurate and efficient sampling for LSST Y10 multi-probe analyses. We make LINNA publicly available at https://github.com/chto/linna, to enable others to perform fast and accurate posterior inference in contemporary cosmological analyses.

Joint analysis of DES Year 3 data and CMB lensing from SPT and Planck I: Construction of CMB Lensing Maps and Modeling Choices

Abstract: Y. Omori,1, 2, 3, 4 E. J. Baxter,5 C. Chang,1, 2 O. Friedrich,6 A. Alarcon,7 O. Alves,8, 9 A. Amon,4 F. Andrade-Oliveira,8 K. Bechtol,10 M. R. Becker,7 G. M. Bernstein,11 J. Blazek,12, 13 L. E. Bleem,14, 2 H. Camacho,15, 9 A. Campos,16 A. Carnero Rosell,17, 9, 18 M. Carrasco Kind,19, 20 R. Cawthon,21 R. Chen,22 A. Choi,23 J. Cordero,24 T. M. Crawford,1, 2 M. Crocce,25, 26 C. Davis,4 J. DeRose,27 S. Dodelson,16, 28 C. Doux,11 A. Drlica-Wagner,1, 29, 2 K. Eckert,11 T. F. Eifler,30, 31 F. Elsner,32 J. Elvin-Poole,33, 34 S. Everett,35 X. Fang,36, 30 A. Ferté,31 P. Fosalba,25, 26 M. Gatti,11 G. Giannini,37 D. Gruen,38, 39 R. A. Gruendl,19, 20 I. Harrison,40, 24, 41 K. Herner,29 H. Huang,30, 42 E. M. Huff,31 D. Huterer,8 M. Jarvis,11 E. Krause,30 N. Kuropatkin,29 P.-F. Leget,4 P. Lemos,32, 43 A. R. Liddle,44, 45, 46 N. MacCrann,47 J. McCullough,4 J. Muir,46 J. Myles,3, 4, 48 A. Navarro-Alsina,49 S. Pandey,11 Y. Park,50 A. Porredon,33, 34 J. Prat,1, 2 M. Raveri,11 R. P. Rollins,24 A. Roodman,4, 48 R. Rosenfeld,51, 9 A. J. Ross,33 E. S. Rykoff,4, 48 C. Sánchez,11 J. Sanchez,29 L. F. Secco,2 I. Sevilla-Noarbe,52 E. Sheldon,53 T. Shin,11 M. A. Troxel,22 I. Tutusaus,54, 25, 26 T. N. Varga,55, 56 N. Weaverdyck,8, 27 R. H. Wechsler,3, 4, 48 W. L. K. Wu,4, 48 B. Yanny,29 B. Yin,16 Y. Zhang,29 J. Zuntz,44 T. M. C. Abbott,57 M. Aguena,9 S. Allam,29 J. Annis,29 D. Bacon,58 B. A. Benson,29, 1, 2 E. Bertin,59, 60 S. Bocquet,61 D. Brooks,32 D. L. Burke,4, 48 J. E. Carlstrom,2, 62, 63, 14, 1 J. Carretero,37 C. L. Chang,14, 1, 2 R. Chown,64, 65 M. Costanzi,66, 67, 68 L. N. da Costa,9, 69 A. T. Crites,70, 1, 2 M. E. S. Pereira,71 T. de Haan,72, 73 J. De Vicente,52 S. Desai,74 H. T. Diehl,29 M. A. Dobbs,75, 76 P. Doel,32 W. Everett,77 I. Ferrero,78 B. Flaugher,29 D. Friedel,19 J. Frieman,29, 2 J. García-Bellido,79 E. Gaztanaga,25, 26 E. M. George,80, 73 T. Giannantonio,81, 6 N. W. Halverson,77, 82 S. R. Hinton,83 G. P. Holder,20, 84, 76 D. L. Hollowood,35 W. L. Holzapfel,73 K. Honscheid,33, 34 J. D. Hrubes,85 D. J. James,86 L. Knox,87 K. Kuehn,88, 89 O. Lahav,32 A. T. Lee,73, 27 M. Lima,90, 9 D. Luong-Van,85 M. March,11 J. J. McMahon,1, 2, 62, 63 P. Melchior,91 F. Menanteau,19, 20 S. S. Meyer,1, 2, 62, 63 R. Miquel,92, 37 L. Mocanu,1, 2 J. J. Mohr,93, 94, 55 R. Morgan,10 T. Natoli,1, 2 S. Padin,23, 1, 2 A. Palmese,36 F. Paz-Chinchón,19, 81 A. Pieres,9, 69 A. A. Plazas Malagón,91 C. Pryke,95 C. L. Reichardt,96 A. K. Romer,43 J. E. Ruhl,97 E. Sanchez,52 K. K. Schaffer,98, 2, 62 M. Schubnell,8 S. Serrano,25, 26 E. Shirokoff,1, 2 M. Smith,99 Z. Staniszewski,31, 97 A. A. Stark,100 E. Suchyta,101 G. Tarle,8 D. Thomas,58 C. To,33 J. D. Vieira,20, 84 J. Weller,55, 94 and R. Williamson31, 1, 2

Tidal disruption of solitons in self-interacting ultralight axion dark matter

Abstract: Ultralight axions (ULAs) are promising dark matter candidates that can have a distinct impact on the formation and evolution of structure on nonlinear scales relative to the cold, collisionless dark matter (CDM) paradigm. However, most studies of structure formation in ULA models do not include the effects of self-interactions, which are expected to arise generically. Here, we study how the tidal evolution of solitons is affected by ULA self-interaction strength and sign. Specifically, using the pseudospectral solver UltraDark.jl , we simulate the tidal disruption of self-interacting solitonic cores as they orbit a 10 11 M (cid:12) Navarro-Frenk-White CDM host halo potential for a range of orbital parameters, assuming a fiducial ULA particle mass of 10 − 22 eV. We find that repulsive (attractive) self-interactions significantly accelerate (decelerate) soliton tidal disruption. We also identify a degeneracy between the self-interaction strength and soliton mass that determines the efficiency of tidal disruption, such that disruption timescales are affected at the ∼ 50% level for variations in the dimensionless ULA self-coupling from λ = − 10 − 92 to λ = 10 − 92 .

Dark Energy Survey Year 3 results: magnification modelling and impact on cosmological constraints from galaxy clustering and galaxy–galaxy lensing

Abstract: We study the effect of magnification in the Dark Energy Survey Year 3 analysis of galaxy clustering and galaxy–galaxy lensing, using two different lens samples: a sample of luminous red galaxies, redMaGiC, and a sample with a redshift-dependent magnitude limit, MagLim. We account for the effect of magnification on both the flux and size selection of galaxies, accounting for systematic effects using the Balrog image simulations. We estimate the impact of magnification on the galaxy clustering and galaxy–galaxy lensing cosmology analysis, finding it to be a significant systematic for the MagLim sample. We show cosmological constraints from the galaxy clustering autocorrelation and galaxy–galaxy lensing signal with different magnifications priors, finding broad consistency in cosmological parameters in ΛCDM and wCDM. However, when magnification bias amplitude is allowed to be free, we find the two-point correlation functions prefer a different amplitude to the fiducial input derived from the image simulations. We validate the magnification analysis by comparing the cross-clustering between lens bins with the prediction from the baseline analysis, which uses only the autocorrelation of the lens bins, indicating that systematics other than magnification may be the cause of the discrepancy. We show that adding the cross-clustering between lens redshift bins to the fit significantly improves the constraints on lens magnification parameters and allows uninformative priors to be used on magnification coefficients, without any loss of constraining power or prior volume concerns.

Symphony: Cosmological Zoom-in Simulation Suites over Four Decades of Host Halo Mass

Abstract: We present Symphony, a compilation of 262 cosmological, cold-dark-matter-only zoom-in simulations spanning four decades of host halo mass, from 1011–1015 M ⊙. This compilation includes three existing simulation suites at the cluster and Milky Way–mass scales, and two new suites: 39 Large Magellanic Cloud-mass (1011 M ⊙) and 49 strong-lens-analog (1013 M ⊙) group-mass hosts. Across the entire host halo mass range, the highest-resolution regions in these simulations are resolved with a dark matter particle mass of ≈3 × 10−7 times the host virial mass and a Plummer-equivalent gravitational softening length of ≈9 × 10−4 times the host virial radius, on average. We measure correlations between subhalo abundance and host concentration, formation time, and maximum subhalo mass, all of which peak at the Milky Way host halo mass scale. Subhalo abundances are ≈50% higher in clusters than in lower-mass hosts at fixed sub-to-host halo mass ratios. Subhalo radial distributions are approximately self-similar as a function of host mass and are less concentrated than hosts’ underlying dark matter distributions. We compare our results to the semianalytic model Galacticus, which predicts subhalo mass functions with a higher normalization at the low-mass end and radial distributions that are slightly more concentrated than Symphony. We use UniverseMachine to model halo and subhalo star formation histories in Symphony, and we demonstrate that these predictions resolve the formation histories of the halos that host nearly all currently observable satellite galaxies in the universe. To promote open use of Symphony, data products are publicly available at http://web.stanford.edu/group/gfc/symphony.

Six More Ultra-Faint Milky Way Companions Discovered in the DECam Local Volume Exploration Survey

Abstract: We report the discovery of six ultra-faint Milky Way satellites discovered through matched-filter searches conducted using Dark Energy Camera (DECam) data processed as part of the second data release of the DECam Local Volume Exploration (DELVE) survey. Leveraging deep Gemini/GMOS-N imaging (for four candidates) as well as follow-up DECam imaging (for two candidates), we characterize the morphologies and stellar populations of these systems. We find that these candidates all share faint absolute magnitudes ( M V ≥ − 3 . 2 mag) and old, metal-poor stellar populations ( τ > 10 Gyr, [Fe / H] < − 1 . 4 dex). Three of these systems are more extended ( r 1 / 2 > 15 pc), while the other three are compact ( r 1 / 2 < 10 pc). From these properties, we infer that the former three systems (Bo¨otes V, Leo Minor I, and Virgo II) are consistent with ultra-faint dwarf galaxy classifications, whereas the latter three (DELVE 3, DELVE 4, and DELVE 5) are likely ultra-faint star clusters. Using data from the Gaia satellite, we confidently measure the proper motion of Bo¨otes V, Leo Minor I, and DELVE 4, and tentatively detect a proper motion signal from DELVE 3 and DELVE 5; no signal is detected for Virgo II. We use these measurements to explore possible associations between the newly-discovered systems and the Sagittarius dwarf spheroidal, the Magellanic Clouds, and the Vast Polar Structure, finding several plausible associations. Our results offer a preview of the numerous ultra-faint stellar systems that will soon be discovered by the Vera C. Rubin Observatory and highlight the challenges of classifying the faintest stellar systems.

Target Selection and Sample Characterization for the DESI LOW-Z Secondary Target Program

Abstract: We introduce the DESI LOW-Z Secondary Target Survey, which combines the wide-area capabilities of the Dark Energy Spectroscopic Instrument (DESI) with an efficient, low-redshift target selection method. Our selection consists of a set of color and surface brightness cuts, combined with modern machine learning methods, to target low-redshift dwarf galaxies ($z$<0.03) between $19