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Roman Space Telescope will survey about 17 million emission-line galaxies over a range of redshifts. Its main targets are Hα emission-line galaxies at low redshifts (z < 2) and [O iii] emission-line galaxies at high redshifts (z > 2). The Roman Space Telescope will estimate the redshift of these galaxies with single-line identification. This suggests that other emission-line galaxies may be misidentified as the main targets. In particular, it is hard to distinguish between the H β and [O iii] lines as the two lines are close in wavelength and hence the photometric information may not be sufficient to separate them reliably. Misidentifying H β emitter as [O iii] emitter will cause a shift in the inferred radial position of the galaxy by approximately 90 Mpc h−1. This length-scale is similar to the Baryon Acoustic Oscillation (BAO) scale and could shift and broaden the BAO peak, possibly introduce errors in determining the BAO peak position. We qualitatively describe the effect of this new systematic and further quantify it with a light-cone simulation with emission-line galaxies. Our results show a systematic shift in the recovered isotropic BAO positions that depends on the percentage of interlopers (percentage of ${\rm H}\,\beta$) in the sample. The systematic shift can be as large as $0.1{-}0.3\,\mathrm{ per}\,\mathrm{ cent} \, {\rm x}\, {{\%}}{\rm H}\,\beta$ for analysis performed at redshifts z = 1.3−1.9.

The Nancy Grace Roman Space Telescope will use its wide-field instrument to carry out a suite of sky surveys in the near infrared. Several of the science objectives of these surveys, such as the measurement of the growth of cosmic structure using weak gravitational lensing, require exquisite control of instrument-related distortions of the images of astronomical objects. Roman will fly 4kx4k Teledyne H4RG-10 infrared detector arrays. This paper investigates whether the pixel centroids are located on a regular grid by projecting laser speckle patterns through a double slit aperture onto a non-flight detector array. We develop a method to reconstruct the pixel centroid offsets from the stochastic speckle pattern. Due to the orientation of the test setup, only x-offsets are measured here. We test the method both on simulations, and by injecting artificial offsets into the real images. We use cross-correlations of the reconstructions from different speckle realizations to determine how much of the variance in the pixel offset maps is signal (fixed to the detector) and how much is noise. After performing this reconstruction on 64x64 pixel patches, and fitting out the best-fit linear mapping from pixel index to position, we find that there are residual centroid offsets in the x (column) direction from a regular grid of 0.0107 pixels RMS (excluding shifts of an entire row relative to another, which our speckle patterns cannot constrain). This decreases to 0.0097 pix RMS if we consider residuals from a quadratic rather than linear mapping. These RMS offsets include both the physical pixel offsets, as well as any apparent offsets due to cross-talk and remaining systematic errors in the reconstruction. We comment on the advantages and disadvantages of speckle scene measurements as a tool for characterizing the pixel-level behavior in astronomical detectors., Comment: 24 pages, 9 figures, to be submitted to PASP

We present a sample of galaxies with the Dark Energy Survey (DES) photometry that replicates the properties of the BOSS CMASS sample. The CMASS galaxy sample has been well characterized by the Sloan Digital Sky Survey (SDSS) collaboration and was used to obtain the most powerful redshift-space galaxy clustering measurements to date. A joint analysis of redshift-space distortions (such as those probed by CMASS from SDSS) and a galaxy-galaxy lensing measurement for an equivalent sample from DES can provide powerful cosmological constraints. Unfortunately, the DES and SDSS-BOSS footprints have only minimal overlap, primarily on the celestial equator near the SDSS Stripe 82 region. Using this overlap, we build a robust Bayesian model to select CMASS-like galaxies in the remainder of the DES footprint. The newly defined DES-CMASS (DMASS) sample consists of 117,293 effective galaxies covering $1,244 {\rm deg}^2$. Through various validation tests, we show that the DMASS sample selected by this model matches well with the BOSS CMASS sample, specifically in the South Galactic cap (SGC) region that includes Stripe 82. Combining measurements of the angular correlation function and the clustering-z distribution of DMASS, we constrain the difference in mean galaxy bias and mean redshift between the BOSS CMASS and DMASS samples to be $\Delta b = 0.010^{+0.045}_{-0.052}$ and $\Delta z = \left( 3.46^{+5.48}_{-5.55} \right) \times 10^{-3}$ for the SGC portion of CMASS, and $\Delta b = 0.044^{+0.044}_{-0.043} $ and $\Delta z= ( 3.51^{+4.93}_{-5.91}) \times 10^{-3}$ for the full CMASS sample. These values indicate that the mean bias of galaxies and mean redshift in the DMASS sample is consistent with both CMASS samples within $1\sigma$., Comment: 22 pages, 17 figures

The Wide Field Infrared Survey Telescope (WFIRST) will conduct a galaxy redshift survey using the H$\alpha$ emission line primarily for spectroscopic redshift determination. Due to the modest spectroscopic resolution of the grism, the H$\alpha$ and the neighboring [NII] lines are blended, leading to a redshift bias that depends on the [NII]/H$\alpha$ ratio, which is correlated with a galaxy's metallicity, hence mass and ultimately environment. We investigate how this bias propagates into the galaxy clustering and cosmological parameters obtained from the WFIRST. Using simulation, we explore the effect of line blending on redshift-space distortion and baryon acoustic oscillation (BAO) measurements. We measure the BAO parameters $\alpha_{\parallel}$, $\alpha_{\perp}$, the logarithmic growth factor $f_{v}$, and calculate their errors based on the correlations between the line ratio and large-scale structure. We find $\Delta\alpha_{\parallel} = 0.31 \pm 0.23 \%$ ($0.26\pm0.17\%$), $\Delta\alpha_{\perp} = -0.10\pm0.10\%$ ($-0.12 \pm 0.11 \%$), and $\Delta f_{v} = 0.17\pm0.33\%$ ($-0.20 \pm 0.30\%$) for redshift 1.355--1.994 (0.700--1.345), which use approximately 18$\%$, 9$\%$, and 7$\%$ of the systematic error budget in a root-sum-square sense. These errors may already be tolerable but further mitigations are discussed. Biases due to the environment-independent redshift error can be mitigated by measuring the redshift error probability distribution function. High-spectral-resolution re-observation of a few thousand galaxies would be required (if by direct approach) to reduce them to below 25$\%$ of the error budget. Finally, we outline the next steps to improve the modeling of [NII]-induced blending biases and their interaction with other redshift error sources., Comment: 19 pages, 11 figures, minor changes, matched with MNRAS accepted version

The Nancy Grace Roman Space Telescope will conduct a High Latitude Spectroscopic Survey (HLSS) over a large volume at high redshift, using the near-IR grism (1.0-1.93 $\mu$m, $R=435-865$) and the 0.28 deg$^2$ wide field camera. We present a reference HLSS which maps 2000 deg$^2$ and achieves an emission line flux limit of 10$^{-16}$ erg/s/cm$^2$ at 6.5$\sigma$, requiring $\sim$0.6 yrs of observing time. We summarize the flowdown of the Roman science objectives to the science and technical requirements of the HLSS. We construct a mock redshift survey over the full HLSS volume by applying a semi-analytic galaxy formation model to a cosmological N-body simulation, and use this mock survey to create pixel-level simulations of 4 deg$^2$ of HLSS grism spectroscopy. We find that the reference HLSS would measure $\sim$ 10 million H$\alpha$ galaxy redshifts that densely map large scale structure at $z=1-2$ and 2 million [OIII] galaxy redshifts that sparsely map structures at $z=2-3$. We forecast the performance of this survey for measurements of the cosmic expansion history with baryon acoustic oscillations and the growth of large scale structure with redshift space distortions. We also study possible deviations from the reference design, and find that a deep HLSS at $f_{\rm line}>7\times10^{-17}$erg/s/cm$^2$ over 4000 deg$^2$ (requiring $\sim$1.5 yrs of observing time) provides the most compelling stand-alone constraints on dark energy from Roman alone. This provides a useful reference for future optimizations. The reference survey, simulated data sets, and forecasts presented here will inform community decisions on the final scope and design of the Roman HLSS., Comment: 29 pages, 8 figures, ApJ submitted

DES Collaboration: et al., The DES-CMASS sample (DMASS) is designed to optimally combine the weak lensing measurements from the Dark Energy Survey (DES) and redshift-space distortions (RSD) probed by the CMASS galaxy sample from the Baryonic Oscillation Spectroscopic Survey. In this paper, we demonstrate the feasibility of adopting DMASS as the equivalent of CMASS for a joint analysis of DES and BOSS in the framework of modified gravity. We utilize the angular clustering of the DMASS galaxies, cosmic shear of the DES METACALIBRATION sources, and cross-correlation of the two as data vectors. By jointly fitting the combination of the data with the RSD measurements from the CMASS sample and Planck data, we obtain the constraints on modified gravity parameters μ0=−0.37+0.47−0.45 and Σ0=0.078+0.078−0.082⁠. Our constraints of modified gravity with DMASS are tighter than those with the DES Year 1 REDMAGIC sample with the same external data sets by 29 per cent for μ0 and 21 per cent for Σ0, and comparable to the published results of the DES Year 1 modified gravity analysis despite this work using fewer external data sets. This improvement is mainly because the galaxy bias parameter is shared and more tightly constrained by both CMASS and DMASS, effectively breaking the degeneracy between the galaxy bias and other cosmological parameters. Such an approach to optimally combine photometric and spectroscopic surveys using a photometric sample equivalent to a spectroscopic sample can be applied to combining future surveys having a limited overlap such as DESI and LSST., AC acknowledges support from NASA grant no. 15-WFIRST15-0008. During the preparation of this paper, C.H. was supported by the Simons Foundation, NASA, and the U.S. Department of Energy. The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MICINN under grants ESP2017-89838, PGC2018-094773, PGC2018-102021, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Brazilian Instituto Nacional de Ciência e Tecnologia (INCT) do e-Universo (CNPq grant no. 465376/2014-2). This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science.

SPHEREx, the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and ices Explorer, is a NASA MIDEX mission planned for launch in 2024. SPHEREx will carry out the first all-sky spectral survey at wavelengths between 0.75µm and 5µm with spectral resolving power ~40 between 0.75 and 3.8µm and ~120 between 3.8 and 5µm At the end of its two-year mission, SPHEREx will provide 0.75-to-5µm spectra of each 6.”2 x 6.”2 pixel on the sky - 14 billion spectra in all. This paper updates an earlier description of SPHEREx presenting changes made during the mission's Preliminary Design Phase, including a discussion of instrument integration and test ow and a summary of the data processing, analysis, and distribution plans.

The baryon-acoustic oscillation (BAO) feature in the Lyman-$\alpha$ forest is one of the key probes of the cosmic expansion rate at redshifts z~2.5, well before dark energy is believed to have become dynamically significant. A key advantage of the BAO as a standard ruler is that it is a sharp feature and hence is more robust against broadband systematic effects than other cosmological probes. However, if the Lyman-$\alpha$ forest transmission is sensitive to the initial streaming velocity of the baryons relative to the dark matter, then the BAO peak position can be shifted. Here we investigate this sensitivity using a suite of hydrodynamic simulations of small regions of the intergalactic medium with a range of box sizes and physics assumptions; each simulation starts from initial conditions at the kinematic decoupling era (z~1059), undergoes a discrete change from neutral gas to ionized gas thermal evolution at reionization (z~8), and is finally processed into a Lyman-$\alpha$ forest transmitted flux cube. Streaming velocities suppress small-scale structure, leading to less violent relaxation after reionization. The changes in the gas distribution and temperature-density relation at low redshift are more subtle, due to the convergent temperature evolution in the ionized phase. The change in the BAO scale is estimated to be of the order of 0.12% at z=2.5; some of the major uncertainties and avenues for future improvement are discussed. The predicted streaming velocity shift would be a subdominant but not negligible effect (of order $0.26\sigma$) for the upcoming DESI Lyman-$\alpha$ forest survey, and exceeds the cosmic variance floor. It is hoped that this study will motivate additional theoretical work on the magnitude of the BAO shift, both in the Lyman-$\alpha$ forest and in other tracers of large-scale structure., Comment: 21 pages, 8 figures, matches MNRAS accepted version

One of the Roman Space Telescopes principal science objectives is to measure dark energy's equation-of-state using a strategic combination of imaging and spectroscopic surveys at high galactic latitude. Type Ia Supernovae survey requirements demand 0.3% photometric accuracy and calibration of key systematic effects. One of these is count rate dependent nonlinearity (CRNL) that if uncorrected affects the accuracy of SNe Ia distance measurements. Romans Relative Calibration System (RCS) enables on-orbit measurement and tracking of CRNL, through a direct illumination mode and a simultaneous lamp plus scene mode. We present results on the impact of CRNL calibration on the dark energy figure of merit (FoM), for a specific reduction of RCS capabilities. We examined many combinations of illumination and passbands, finding that only six meet the requirements. No RCS at all results in a factor of 5 degradation in the FoM.

The Wide Field Infrared Survey Telescope (WFIRST) will investigate the origins of cosmic acceleration using weak gravitational lensing at near infrared wavelengths. Lensing analyses place strict constraints on the precision of size and ellipticity measurements of the point spread function. WFIRST will use infrared detector arrays, which must be fully characterized to inform data reduction and calibration procedures such that unbiased cosmological results can be achieved. Hirata & Choi 2019 introduces formalism to connect the cross-correlation signal of different flat field time samples to non-linear detector behaviors such as the brighter fatter effect (BFE) and non-linear inter-pixel capacitance (NL-IPC), and this paper applies that framework to a WFIRST development detector, SCA 18237. We find a residual correlation signal after accounting for classical non-linearity. This residual correlation contains a combination of the BFE and NL-IPC; however, further tests suggest that the BFE is the dominant mechanism. If interpreted as a pure BFE, it suggests that the effective area of a pixel is increased by $(2.87\pm0.03)\times 10^{-7}$ (stat.) for every electron in the 4 nearest neighbors, with a rapid $\sim r^{-5.6\pm0.2}$ fall-off of the effect for more distant neighbors. We show that the IPC inferred from hot pixels contains the same large-scale spatial variations as the IPC inferred from auto-correlations, albeit with an overall offset of $\sim 0.06\%$. The NL-IPC inferred from hot pixels is too small to explain the cross-correlation measurement, further supporting the BFE hypothesis. This work presents the first evidence for the BFE in an H4RG-10 detector, demonstrates some of the useful insights that can be gleaned from flat field statistics, and represents a significant step towards calibration of WFIRST data., 28 pages, 8 figures, 3 tables, version accepted by PASP

A fraction of the light observed from edge-on disk galaxies is polarized due to two physical effects: selective extinction by dust grains aligned with the magnetic field, and scattering of the anisotropic starlight field. Since the reflection and transmission coefficients of the reflecting and refracting surfaces in an optical system depend on the polarization of incoming rays, this optical polarization produces both (a) a selection bias in favor of galaxies with specific orientations and (b) a polarization-dependent PSF. In this work we build toy models to obtain for the first time an estimate for the impact of polarization on PSF shapes and the impact of the selection bias due to the polarization effect on the measurement of the ellipticity used in shear measurements. In particular, we are interested in determining if this effect will be significant for WFIRST. We show that the systematic uncertainties in the ellipticity components are $8\times 10^{-5}$ and $1.1 \times 10^{-4}$ due to the selection bias and PSF errors respectively. Compared to the overall requirements on knowledge of the WFIRST PSF ellipticity ($4.7\times 10^{-4}$ per component), both of these systematic uncertainties are sufficiently close to the WFIRST tolerance level that more detailed studies of the polarization effects or more stringent requirements on polarization-sensitive instrumentation for WFIRST are required., Comment: 8 pages, 3 figures, updated to published version

Galaxy–galaxy lensing is an essential tool for probing dark matter haloes and constraining cosmological parameters. While galaxy–galaxy lensing measurements usually rely on shear, weak-lensing magnification contains additional constraining information. Using the Fundamental Plane (FP) of elliptical galaxies to anchor the size distribution of a background population is one method that has been proposed for performing a magnification measurement. We present a formalism for using the FP residuals of elliptical galaxies to jointly estimate the foreground mass and background redshift errors for a stacked lens scenario. The FP residuals include information about weak-lensing magnification κ, and therefore foreground mass, since to first order, non-zero κ affects galaxy size but not other FP properties. We also present a modular, extensible code that implements the formalism using emulated galaxy catalogues of a photometric galaxy survey. We find that combining FP information with observed number counts of the source galaxies constrains mass and photo-z error parameters significantly better than an estimator that includes number counts only. In particular, the constraint on the mass is 17.0 per cent if FP residuals are included, as opposed to 27.7 per cent when only number counts are included. The effective size noise for a foreground lens of mass $M_\mathrm{ H}=10^{14}\, \mathrm{M}_\odot$, with a conservative selection function in size and surface brightness applied to the source population, is σκ, eff = 0.250. We discuss the improvements to our FP model necessary to make this formalism a practical companion to shear analyses in weak-lensing surveys.

As the only dark matter candidate that does not invoke a new particle that survives to the present day, primordial black holes (PBHs) have drawn increasing attention recently. Up to now, various observations have strongly constrained most of the mass range for PBHs, leaving only small windows where PBHs could make up a substantial fraction of the dark matter. Here we revisit the PBH constraints for the asteroid-mass window, i.e., the mass range $3.5\times 10^{-17}M_\odot < m_{\mathrm{PBH}} < 4\times 10^{-12}M_\odot$. We revisit 3 categories of constraints. (1) For optical microlensing, we analyze the finite source size and diffractive effects and discuss the scaling relations between the event rate, $m_{\mathrm{PBH}}$ and the event duration. We argue that it will be difficult to push the existing optical microlensing constraints to much lower m$_{\mathrm{PBH}}$. (2) For dynamical capture of PBHs in stars, we derive a general result on the capture rate based on phase space arguments. We argue that survival of stars does not constrain PBHs, but that disruption of stars by captured PBHs should occur and that the asteroid-mass PBH hypothesis could be constrained if we can work out the observational signature of this process. (3) For destruction of white dwarfs by PBHs that pass through the white dwarf without getting gravitationally captured, but which produce a shock that ignites carbon fusion, we perform a 1+1D hydrodynamic simulation to explore the post-shock temperature and relevant timescales, and again we find this constraint to be ineffective. In summary, we find that the asteroid-mass window remains open for PBHs to account for all the dark matter., Updated to match accepted version for publication. 43 pages

The observable universe contains density perturbations on scales larger than any finite volume survey. Perturbations on scales larger than a survey can measure degrade its power to constrain cosmological parameters. The dependence of survey observables such as the weak lensing power spectrum on these long-wavelength modes results in super-sample covariance. Accurately forecasting parameter constraints for future surveys requires accurately accounting for the super-sample effects. If super-sample covariance is in fact a major component of the survey error budget, it may be necessary to investigate mitigation strategies that constrain the specific realization of the long-wavelength modes. We present a Fisher matrix based formalism for approximating the magnitude of super-sample covariance and the effectiveness of mitigation strategies for realistic survey geometries. We implement our formalism in the public code SuperSCRAM: Super-Sample Covariance Reduction and Mitigation. We illustrate SuperSCRAM with an example application, where the modes contributing to super-sample covariance in the WFIRST weak lensing survey are constrained by the low-redshift galaxy number counts in the wider LSST footprint. We find that super-sample covariance increases the volume of the error ellipsoid in 7D cosmological parameter space by a factor of 4.5 relative to Gaussian statistical errors only, but our simple mitigation strategy more than halves the contamination, to a factor of 2.0., Comment: 32 pages, 7 figures, 1 table, comments/suggestions welcome!

The magnetic fields of the solar system planets provide valuable insights into the planets' interiors and can have dramatic consequences for the evolution of their atmospheres and interaction with the solar wind. However, we have little direct knowledge of magnetic fields in exoplanets. Here we present a method for detecting magnetic fields in the atmospheres of close-in exoplanets based on spectropolarimetric transit observations at the wavelength of the helium line at 1083 nm. This methodology has been successfully applied before for exploring magnetic fields in solar coronal filaments. Strong absorption signatures (transit depths on the order of a few percent) in the 1083 nm line have recently been observed for several close-in exoplanets. We show that in the conditions in these escaping atmospheres, metastable helium atoms should be optically pumped by the starlight and, for field strengths more than a few $\times 10^{-4}$ G, should align with the magnetic field. This results in linearly polarized absorption at 1083 nm that traces the field direction (the Hanle effect), which we explore by both analytic computation and with the Hazel numerical code. The linear polarization $\sqrt{Q^2+U^2}/I$ ranges from $\sim 10^{-3}$ in optimistic cases down to a few $\times 10^{-5}$ for particularly unfavorable cases, with very weak dependence on field strength. The line-of-sight component of the field results in a slight circular polarization (the Zeeman effect), also reaching $V/I\sim {\rm few}\times 10^{-5}(B_\parallel/10\,{\rm G})$. We discuss the detectability of these signals with current (SPIRou) and future (extremely large telescope) high-resolution infrared spectropolarimeters, and we briefly comment on possible sources of astrophysical contamination., Comment: published in The Astrophysical Journal on February 14, 2020; updated to match the published version

ATLAS (Astrophysics Telescope for Large Area Spectroscopy) Probe is a mission concept for a NASA probe-class space mission with primary science goal the definitive study of galaxy evolution through the capture of 300,000,000 galaxy spectra up to z=7. It is made of a 1.5-m Ritchey-Chretien telescope with a field of view of solid angle 0.4 deg^2. The wavelength range is at least 1 μm to 4 μm with a goal of 0.9 μm to 5 μm. Average resolution is 600 but with a possible trade-off to get 1000 at the longer wavelengths. The ATLAS Probe instrument is made of 4 identical spectrographs each using a Digital Micro-mirror Device (DMD) as a multi-object mask. It builds on the work done for the ESA SPACE and Phase-A EUCLID projects. Three-mirror fore-optics re-image each sub-field on its DMD which has 2048 x 1080 mirrors 13.6 μm wide with 2 possible tilts, one sending light to the spectrograph, the other to a light dump. The ATLAS Probe spectrographs use prisms as dispersive elements because of their higher and more uniform transmission, their larger bandwidth, and the ability to control the resolution slope with the choice of glasses. Each spectrograph has 2 cameras. While the collimator is made of 4 mirrors, each camera is made of only one mirror which reduces the total number of optics. All mirrors are aspheric but with a relatively small P-V with respect to their best fit sphere making them easily manufacturable. For imaging, a simple mirror to replace the prism is not an option because the aberrations are globally corrected by the collimator and camera together which gives large aberrations when the mirror is inserted. An achromatic grism is used instead. There are many variations of the design that permit very different packaging of the optics. ATLAS Probe will enable ground-breaking science in all areas of astrophysics. It will (1) revolutionize galaxy evolution studies by tracing the relation between galaxies and dark matter from the local group to cosmic voids and filaments, from the epoch of reionization through the peak era of galaxy assembly; (2) open a new window into the dark universe by mapping the dark matter filaments to unveil the nature of the dark Universe using 3D weak lensing with spectroscopic redshifts, and obtaining definitive measurements of dark energy and modification of gravity using cosmic large-scale structure; (3) probe the Milky Way's dust-shrouded regions, reaching the far side of our Galaxy; and (4) characterize asteroids and other objects in the outer solar systems.

SPHEREx, a mission in NASA’s Medium Explorer (MIDEX) program recently selected for Phase-A implementation, is an all-sky survey satellite that will produce a near-infrared spectrum for every 6 arcsecond pixel on the sky. SPHEREx has a simple, high-heritage design with large optical throughput to maximize spectral mapping speed. While the legacy data products will provide a rich archive of spectra for the entire astronomical community to mine, the instrument is optimized for three specific scientific goals: to probe inflation through the imprint primordial non-Gaussianity left on today’s large-scale cosmological structure; to survey the Galactic plane for water and other biogenic ices through absorption line studies; and to constrain the history of galaxy formation through power spectra of background fluctuations as measured in deep regions near the ecliptic poles. The aluminum telescope consists of a heavily baffled, wide-field off-axis reflective triplet design. The focal plane is imaged simultaneously by two mosaics of H2RG detector arrays separated by a dichroic beamsplitter. SPHEREx assembles spectra through the use of mass and volume efficient linear variable filters (LVFs) included in the focal plane assemblies, eliminating the need for any dispersive or moving elements. Instead, spectra are constructed through a series of small steps in the spacecraft attitude across the sky, modulating the location of an object within the FOV and varying the observation wavelength in each exposure. The spectra will cover the wavelength range between 0.75 and 5.0 µm at spectral resolutions ranging between R=35 and R=130. The entire telescope is cooled passively by a series of three V-groove radiators below 80K. An additional stage of radiative cooling is included to reduce the long wavelength focal plane temperature below 60K, controlling the dark current. As a whole, SPHEREx requires no new technologies and carries large technical and resource margins on every aspect of the design.

We present the most detailed computation to date of the 21-cm global signal and fluctuations at $z\gtrsim 500$. Our calculations include a highly precise estimate of the Wouthuysen-Field (WF) effect and the first explicit calculation of the impact of free-free processes, the two dominant components of the signal at $z\gtrsim 800$. We implement a new high-resolution Ly$\alpha$ radiative transfer calculation, coupled to a state-of-the-art primordial recombination code. Using these tools, we find a global signal from 21-cm processes alone of roughly 0.01mK at $z\sim1000$, slightly larger than it would be without the WF effect, but much weaker than previous estimates including this effect. We also find that this signal is swamped by a smooth $1-2$ mK signal due to free-free absorption at high redshift by the partially ionized gas along the line of sight. In addition, we estimate the amplitude of 21-cm fluctuations, of order $\sim 10^{-7}$ mK at $z\sim1000$. Unfortunately, we find that due to the brightness of the low-frequency sky, these fluctuations will not be observable beyond $z\sim$ a few hundred by even extremely futuristic observations. The 21 cm fluctuations are exponentially suppressed at higher redshifts by the large free-free optical depth, making this the ultimate upper redshift limit for 21-cm surveys., Comment: 14 pages, 9 figures, submitted to PRD

The circular polarization of the cosmic microwave background (CMB) is usually taken to be zero since it is not generated by Thomson scattering. Here we explore the actual level of circular polarization in the CMB generated by conventional cosmological sources of birefringence. We consider two classes of mechanisms for birefringence. One is alignment of the matter to produce an anisotropic susceptibility tensor: the hydrogen spins can be aligned either by density perturbations or CMB anisotropies themselves. The other is anisotropy of the radiation field coupled to the non-linear response of the medium to electromagnetic fields: this can occur either via photon-photon scattering (non-linear response of the vacuum); atomic hyperpolarizability (non-linear response of neutral atoms); or plasma delay (non-linear response of free electrons). The strongest effect comes from photon-photon scattering from recombination at a level of $\sim 10^{-14}$ K. Our results are consistent with a negligible circular polarization of the CMB in comparison with the linear polarization or the sensitivity of current and near-term experiments., Comment: New version matches the accepted version for publication. 45 pages, 7 figures

Several recent papers have proposed schemes by which a dispersion measure, and hence electron column, could be obtained from a time-steady, incoherent radio source at a cosmological distance (such as an active galactic nucleus). If correct, this would open a new window on the distribution of intergalactic baryons. These schemes are based on the statistical properties of the received radiation, such as the 2- or 4-point correlation function of the received electric field, and in one case on the quantum nature of the electromagnetic field. We show, on the basis of general principles, that these schemes are not sensitive to dispersion measure (or have an extremely small signal-to-noise ratio), because (i) the classical 2-point correlation function is unaffected by dispersion; (ii) for a source with a large number of incoherently emitting electrons, the central limit theorem obliterates additional information in higher-order functions; and (iii) such an emitter produces a radiation density matrix that is equivalent to a statistical distribution of coherent states, which contains no information that is not already in the statistics of the classical waveforms. Why the proposed observables do not depend on dispersion measure (or have extremely tiny dependences) is discussed in detail., 16 pages, 1 figure

Statistical weak lensing by large-scale structure -- cosmic shear -- is a promising cosmological tool, which has motivated the design of several large upcoming surveys. Here, we present a measurement of cosmic shear using coadded Sloan Digital Sky Survey (SDSS) imaging in 168 square degrees of the equatorial region, with r, 23 pages, 21 figures, 2 tables, Part 2 of 2; to be submitted to MNRAS

The observed binary black hole (BBH) mergers indicate a large Galactic progenitor population continuously evolving from large orbital separations and low gravitational wave (GW) frequencies to the final merger phase. We investigate the equilibrium distribution of binary black holes in the Galaxy. Given the observed BBH merger rate, we contrast the expected number of systems radiating in the low-frequency $0.1-10\,$mHz GW band under two assumptions: (1) that all merging systems originate from near-circular orbits, as may be indicative of isolated binary evolution, and (2) that all merging systems originate at very high eccentricity, as predicted by models of dynamically-formed BBHs and triple and quadruple systems undergoing Lidov-Kozai eccentricity oscillations. We show that the equilibrium number of systems expected at every frequency is higher in the eccentric case (2) than in the circular case (1) by a factor of $\simeq 2-15$. This follows from the fact that eccentric systems spend more time than circular systems radiating in the low-frequency GW bands. The GW emission comes in pulses at periastron separated by the orbital period, which may be days to years. For a LISA-like sensitivity curve, we show that if eccentric systems contribute significantly to the observed merger rate, then $\simeq 10$ eccentric systems should be seen in the Galaxy., Comment: 12 pages, 6 figures, matches ApJ accepted version

Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 micron cut-off Teledyne HgCdTe/H2RG detector. We used a 880nm LED illumination source and f/22 pupil stop to produce undersampled point spread functions similar to those expected from WFIRST. We also emulated the WFIRST image reconstruction strategy, using the IMage COMbination (IMCOM) algorithm to derive oversampled images from dithered, undersampled input images. We created shear maps for this data and computed shear correlation functions to mimic a real weak lensing analysis. After removing only 2nd order polynomial fits to the shear maps, we found that the correlation functions could be reduced to O(10^-6). This places a conservative upper limit on the detector-induced bias to the correlation function (under our test conditions). This bias is two orders of magnitude lower than the expected weak lensing signal. Restricted to scales relevant to dark energy analyses (sky separations > 0.5 arcmin), the bias is O(10^-7): comparable to the requirement for future weak lensing missions to avoid biasing cosmological parameter estimates. Our experiment will need to be upgraded and repeated under different configurations to fully characterize the shape measurement performance of WFIRST IR detectors., 57 pages (double-spaced preprint format), 17 color figures, accepted to PASP. Changes to version 2: fixed typos, figure quality

The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of "dark energy" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious experimental efforts to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit "Stage IV" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski test, and direct measurements of H_0. We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from GR, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and CMB data. We also show the level of precision required for other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets with broad applications, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales., Comment: 289 pages, 55 figures. Accepted for publication in Physics Reports. Description of changes since original version --- fractionally small but significant in total --- is available at http://www.astronomy.ohio-state.edu/~dhw/Review

The GMRT Epoch of Reionization (EoR) experiment is an ongoing effort to measure the power spectrum from neutral hydrogen at high redshift. We have previously reported an upper limit of (70 mK)^2 at wavenumbers of k=0.65 h/Mpc using a basic piecewise-linear foreground subtraction. In this paper we explore the use of a singular value decomposition to remove foregrounds with fewer assumptions about the foreground structure. Using this method we also quantify, for the first time, the signal loss due to the foreground filter and present new power spectra adjusted for this loss, providing a revised measurement of a 2-sigma upper limit at (248 mK)^2 for k=0.50 h/Mpc. While this revised limit is larger than previously reported, we believe it to be more robust and still represents the best current constraints on reionization at z=8.6., Comment: 10 pages, 11 figures, accepted for publication in MNRAS

We perform a detailed study of the weak interactions of standard model neutrinos with the primordial plasma and their effect on the resonant production of sterile neutrino dark matter. Motivated by issues in cosmological structure formation on small scales, and reported X-ray signals that could be due to sterile neutrino decay, we consider 7 keV-scale sterile neutrinos. Oscillation-driven production of such sterile neutrinos occurs at temperatures T ≳ 100 MeV, where we study two significant effects of weakly charged species in the primordial plasma: (1) the redistribution of an input lepton asymmetry; (2) the opacity for active neutrinos. We calculate the redistribution analytically above and below the quark-hadron transition, and match with lattice QCD calculations through the transition. We estimate opacities due to tree level processes involving leptons and quarks above the quark-hadron transition, and the most important mesons below the transition. We report final sterile neutrino dark matter phase space densities that are significantly influenced by these effects, and yet relatively robust to remaining uncertainties in the nature of the quark-hadron transition. We also provide transfer functions for cosmological density fluctuations with cutoffs at k ≃ 10 h Mpc^(−1), that are relevant to galactic structure formation.

Cosmic surveys provide crucial information about high energy physics including strong evidence for dark energy, dark matter, and inflation. Ongoing and upcoming surveys will start to identify the underlying physics of these new phenomena, including tight constraints on the equation of state of dark energy, the viability of modified gravity, the existence of extra light species, the masses of the neutrinos, and the potential of the field that drove inflation. Even after the Stage IV experiments, DESI and LSST, complete their surveys, there will still be much information left in the sky. This additional information will enable us to understand the physics underlying the dark universe at an even deeper level and, in case Stage IV surveys find hints for physics beyond the current Standard Model of Cosmology, to revolutionize our current view of the universe. There are many ideas for how best to supplement and aid DESI and LSST in order to access some of this remaining information and how surveys beyond Stage IV can fully exploit this regime. These ideas flow to potential projects that could start construction in the 2020's.

A strong instrumentation and detector R&D program has enabled the current generation of cosmic frontier surveys. A small investment in R&D will continue to pay dividends and enable new probes to investigate the accelerated expansion of the universe. Instrumentation and detector R&D provide critical training opportunities for future generations of experimentalists, skills that are important across the entire Department of Energy High Energy Physics program.

At the epoch of decoupling, cosmic baryons had supersonic velocities relative to the dark matter that were coherent on large scales. These velocities subsequently slow the growth of small-scale structure and, via feedback processes, can influence the formation of larger galaxies. We examine the effect of streaming velocities on the galaxy correlation function, including all leading-order contributions for the first time. We find that the impact on the BAO peak is dramatically enhanced (by a factor of ~5) over the results of previous investigations, with the primary new effect due to advection: if a galaxy retains memory of the primordial streaming velocity, it does so at its Lagrangian, rather than Eulerian, position. Since correlations in the streaming velocity change rapidly at the BAO scale, this advection term can cause a significant shift in the observed BAO position. If streaming velocities impact tracer density at the 1% level, compared to the linear bias, the recovered BAO scale is shifted by approximately 0.5%. This new effect, which is required to preserve Galilean invariance, greatly increases the importance of including streaming velocities in the analysis of upcoming BAO measurements and opens a new window to the astrophysics of galaxy formation., 10 pages, 2 figures. PRL version with supplemental materials in appendix. Comments welcome

In this paper, we measure the optical-to-virial velocity ratios Vopt/V200c of disk galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of = 0.07 and with stellar masses 10^9 M_sun < M_* < 10^11 M_sun. Vopt/V200c, the ratio of the circular velocity measured at the virial radius of the dark matter halo (\sim150 kpc) to that at the optical radius of the disk (\sim10 kpc), is a powerful observational constraint on disk galaxy formation. It links galaxies to their dark matter haloes dynamically and constrains the total mass profile of disk galaxies over an order of magnitude in length scale. For this measurement, we combine Vopt derived from the Tully-Fisher relation (TFR) from Reyes et al. with V200c derived from halo masses measured with galaxy-galaxy lensing. In anticipation of this combination, we use similarly-selected galaxy samples for both the lensing and TFR analysis. For three M_* bins with lensing-weighted mean stellar masses of 0.6, 2.7, and 6.5 x 10^10 M_sun, we find halo-to-stellar mass ratios M_vir/M_* = 41, 23, and 26, with 1-sigma statistical uncertainties of around 0.1 dex, and Vopt/V200c = 1.27\pm0.08, 1.39\pm0.06, 1.27\pm0.08 (1{\sigma}). Our results suggest that the dark matter and baryonic contributions to the mass within the optical radius are comparable, if the dark matter halo profile has not been significantly modified by baryons. The results obtained in this work will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work. Finally, we note that this paper presents a new and improved galaxy shape catalogue for weak lensing that covers the full SDSS DR7 footprint.

Dark and baryonic matter moved at different velocities in the early Universe, which strongly suppressed star formation in some regions. This was estimated to imprint a large-scale fluctuation signal of about 2 mK in the 21-cm spectral line of atomic hydrogen associated with stars at a redshift of 20, although this estimate ignored the critical contribution of gas heating due to X-rays and major enhancements of the suppression. A large velocity difference reduces the abundance of halos and requires the first stars to form in halos of about a million solar masses, substantially greater than previously expected. Here we report a simulation of the distribution of the first stars at z=20 (cosmic age of ~180 Myr), incorporating all these ingredients within a 400 Mpc box. We find that the 21-cm signature of these stars is an enhanced (10 mK) fluctuation signal on the 100-Mpc scale, characterized by a flat power spectrum with prominent baryon acoustic oscillations. The required sensitivity to see this signal is achievable with an integration time of a thousand hours with an instrument like the Murchison Wide-field Array or the Low Frequency Array but designed to operate in the range of 50-100 MHz., 27 pages, 5 figures, close (but not exact) match to accepted version. Basic results unchanged from first submitted version, but justification strengthened, title and abstract modified, and substantial Supplementary Material added. Originally first submitted for publication on Oct. 12, 2011

In astrophysical regimes where the collisional excitation of hydrogen atoms is relevant, the cross sections for the interactions of hydrogen atoms with electrons and protons are necessary for calculating line profiles and intensities. In particular, at relative velocities exceeding ~1000 km/s, collisional excitation by protons dominates over that by electrons. Surprisingly, the hydrogen-proton cross sections at these velocities do not exist for atomic levels of n >= 4, forcing researchers to utilize extrapolation via inaccurate scaling laws. In this study, we present a faster and improved algorithm for computing cross sections for the hydrogen-proton collisional system, including excitation and charge transfer to the n >= 2 levels of the hydrogen atom. We develop a code named BDSCx which directly solves the Schrodinger equation with variable (but non-adaptive) resolution and utilizes a hybrid spatial-Fourier grid. Our novel hybrid grid reduces the number of grid points needed from ~4000 n^6 (for a "brute force", Cartesian grid) to ~2000 n^4 and speeds up the computation by a factor ~50 for calculations going up to n = 4 . We present (l,m)-resolved results for charge-transfer and excitation final states for n = 2--4 and for projectile energies of 5--80 keV, as well as fitting functions for the cross sections. The ability to accurately compute proton-hydrogen cross sections to n = 4 allows us to calculate the Balmer decrement, the ratio of Balmer alpha to Balmer beta line intensities. We find that the Balmer decrement starts to increase beyond its largely constant value of 2--3 below 10 keV, reaching values of 4--5 at 5 keV, thus complicating its use as a diagnostic of dust extinction when fast (~1000$ km/s) shocks are impinging upon the ambient interstellar medium.

Current and upcoming wide-field, ground-based, broad-band imaging surveys promise to address a wide range of outstanding problems in galaxy formation and cosmology. Several such uses of ground-based data, especially weak gravitational lensing, require highly precise measurements of galaxy image statistics with careful correction for the effects of the point-spread function (PSF). In this paper, we introduce the SHERA (SHEar Reconvolution Analysis) software to simulate ground-based imaging data with realistic galaxy morphologies and observing conditions, starting from space-based data (from COSMOS, the Cosmological Evolution Survey) and accounting for the effects of the space-based PSF. This code simulates ground-based data, optionally with a weak lensing shear applied, in a model-independent way using a general Fourier space formalism. The utility of this pipeline is that it allows for a precise, realistic assessment of systematic errors due to the method of data processing, for example in extracting weak lensing galaxy shape measurements or galaxy radial profiles, given user-supplied observational conditions and real galaxy morphologies. Moreover, the simulations allow for the empirical test of error estimates and determination of parameter degeneracies, via generation of many noise maps. The public release of this software, along with a large sample of cleaned COSMOS galaxy images (corrected for charge transfer inefficiency), should enable upcoming ground-based imaging surveys to achieve their potential in the areas of precision weak lensing analysis, galaxy profile measurement, and other applications involving detailed image analysis.

Anomalous microwave emission is known to exist in the Perseus cloud. One of the most promising candidates to explain this excess of emission is electric dipole radiation from rapidly rotating very small dust grains, commonly referred to as spinning dust. Photometric data obtained with the Spitzer Space Telescope have been reprocessed and used in conjunction with the dust emission model DUSTEM to characterise the properties of the dust within the cloud. This analysis has allowed us to constrain spatial variations in the strength of the interstellar radiation field ($\chi_\mathrm{ISRF}$), the mass abundances of the PAHs and VSGs relative to the BGs (Y$_\mathrm{PAH}$ and Y$_\mathrm{VSG}$), the column density of hydrogen (N$_\mathrm{H}$) and the equilibrium dust temperature (T$_\mathrm{dust}$). The parameter maps of Y$_\mathrm{PAH}$, Y$_\mathrm{VSG}$ and $\chi_\mathrm{ISRF}$ are the first of their kind to be produced for the Perseus cloud, and we used these maps to investigate the physical conditions in which anomalous emission is observed. We find that in regions of anomalous emission the strength of the ISRF, and consequently the equilibrium temperature of the dust, is enhanced while there is no significant variation in the abundances of the PAHs and the VSGs or the column density of hydrogen. We interpret these results as an indication that the enhancement in $\chi_\mathrm{ISRF}$ might be affecting the properties of the small stochastically heated dust grains resulting in an increase in the spinning dust emission observed at 33 GHz. This is the first time that such an investigation has been performed, and we believe that this type of analysis creates a new perspective in the field of anomalous emission studies, and represents a powerful new tool for constraining spinning dust models.

We study the effect of the relative velocity of dark matter and baryonic fluids after the epoch of recombination on the evolution of the first bound objects in the early universe. Recent work has shown that, although relative motion of the two fluids is formally a second order effect in density, it has a dramatic impact on the formation and distribution of the first cosmic structures. Focusing on the gas content, we analyze the effect of relative velocity on the properties of halos over a wide range of halo masses and redshifts. We calculate accurately the linear evolution of the baryon and dark matter fluctuations, and quantify the resulting effect on halos based on an analytical formalism that has been carefully checked with simulations in the case with no relative velocity. We estimate the effect on the abundance of and gas fraction in early halos. We find that the relative velocity effect causes several changes: (i) the characteristic mass that divides gas-rich and gas-poor halos is increased by roughly an order of magnitude, from 2 10^4 Msun to about 2 10^5 Msun; (ii) this characteristic mass has a large scatter (full width at half maximum is ~ 1.5 10^5 Msun at z=20); (iii) the fraction of baryons in star-less gas minihalos is suppressed by a factor of 4 at z=20; (iv) the fraction of baryons in halos that can cool and form stars is suppressed by a factor of 1.5 at z=20; and (v) there are enhanced spatial variations of these various fractions.

Lindblad resonances have been suggested as an important mechanism for angular momentum transport and heating in discs in binary black hole systems. We present the basic equations for the torque and heating rate for relativistic thin discs subjected to a perturbation. The Lindblad resonance torque is written explicitly in terms of metric perturbations for an equatorial disc in a general axisymmetric, time-stationary spacetime with a plane of symmetry. We show that the resulting torque formula is gauge-invariant. Computations for the Schwarzschild and Kerr spacetimes are presented in the companion paper.

We present a fully relativistic computation of the torques due to Lindblad resonances from perturbers on circular, equatorial orbits on discs around Schwarzschild and Kerr black holes. The computation proceeds by establishing a relation between the Lindblad torques and the gravitational waveforms emitted by the perturber and a test particle in a slightly eccentric orbit at the radius of the Lindblad resonance. We show that our result reduces to the usual formula when taking the nonrelativistic limit. Discs around a black hole possess an m=1 inner Lindblad resonance with no Newtonian Keplerian analogue; however its strength is very weak even in the moderately relativistic regime (r/M ~ few tens), which is in part due to the partial cancellation of the two leading contributions to the resonant amplitude (the gravitoelectric octupole and gravitomagnetic quadrupole). For equatorial orbits around Kerr black holes, we find that the m=1 ILR strength is enhanced for retrograde spins and suppressed for prograde spins. We also find that the torque associated with the m>=2 inner Lindblad resonances is enhanced relative to the nonrelativistic case; the enhancement is a factor of 2 for the Schwarzschild hole even when the perturber is at a radius of 25M.

We investigate the rotational emission from dust grains that rotate around non- principal axes. We argue that in many phases of the interstellar medium, the smallest grains, which dominate spinning dust emission, are likely to have their nutation state (orientation of principal axes relative to the angular momentum vector) randomized during each thermal spike. We recompute the excitation and damping rates associated with rotational emission from the grain permanent dipole, grain-plasma interactions, infrared photon emission, and collisions. The resulting spinning dust spectra gener- ally show a shift toward higher emissivities and peak frequencies relative to previous calculations.

If the orientations of galaxies are correlated with large-scale structure, then anisotropic selection effects such as preferential selection of face-on disc galaxies can contaminate large scale structure observables. Here we consider the effect on the galaxy bispectrum, which has attracted interest as a way to break the degeneracy between galaxy bias and the amplitude of matter fluctuations sigma_8. We consider two models of intrinsic galaxy alignments: one where the probability distribution for the galaxy's orientation contains a term linear in the local tidal field, appropriate for elliptical galaxies; and one with a term quadratic in the local tidal field, which may be applicable to disc galaxies. We compute the correction to the redshift-space bispectrum in the quasilinear regime, and then focus on its effects on parameter constraints from the transverse bispectrum, i.e. using triangles in the plane of the sky. We show that in the linear alignment model, intrinsic alignments result in an error in the galaxy bias parameters, but do not affect the inferred value of sigma_8. In contrast, the quadratic alignment model results in a systematic error in both the bias parameters and sigma_8. However, the quadratic alignment effect has a unique configuration dependence that should enable it to be removed in upcoming surveys.

We present a community-led assessment of the solar system investigations achievable with NASA’s next-generation space telescope, the Wide Field Infrared Survey Telescope (WFIRST). WFIRST will provide imaging, spectroscopic, and coronagraphic capabilities from 0.43 to 2.0 μm and will be a potential contemporary and eventual successor to the James Webb Space Telescope (JWST). Surveys of irregular satellites and minor bodies are where WFIRST will excel with its 0.28 deg^2 field-of-view Wide Field Instrument. Potential ground-breaking discoveries from WFIRST could include detection of the first minor bodies orbiting in the inner Oort Cloud, identification of additional Earth Trojan asteroids, and the discovery and characterization of asteroid binary systems similar to Ida/Dactyl. Additional investigations into asteroids, giant planet satellites, Trojan asteroids, Centaurs, Kuiper belt objects, and comets are presented. Previous use of astrophysics assets for solar system science and synergies between WFIRST, Large Synoptic Survey Telescope, JWST, and the proposed Near-Earth Object Camera mission is discussed. We also present the case for implementation of moving target tracking, a feature that will benefit from the heritage of JWST and enable a broader range of solar system observations.

Intrinsic alignments (IA), correlations between the intrinsic shapes and orientations of galaxies on the sky, are both a significant systematic in weak lensing and a probe of the effect of large-scale structure on galactic structure and angular momentum. In the era of precision cosmology, it is thus especially important to model IA with high accuracy. Efforts to use cosmological perturbation theory to model the dependence of IA on the large-scale structure have thus far been relatively successful; however, extant models do not consistently account for time evolution. In particular, advection of galaxies due to peculiar velocities alters the impact of IA, because galaxy positions when observed are generally different from their positions at the epoch when IA is believed to be set. In this work, we evolve the galaxy IA from the time of galaxy formation to the time at which they are observed, including the effects of this advection, and show how this process naturally leads to a dependence of IA on the velocity shear. We calculate the galaxy-galaxy-IA bispectrum to tree level (in the linear matter density) in terms of the evolved IA coefficients. We then discuss the implications for weak lensing systematics as well as for studies of galaxy formation and evolution. We find that considering advection introduces nonlocality into the bispectrum, and that the degree of nonlocality represents the memory of a galaxy's path from the time of its formation to the time of observation. We discuss how this result can be used to constrain the redshift at which IA is determined and provide Fisher estimation for the relevant measurements using the example of SDSS-BOSS., Comment: 30 pages, 5 figures, 2 tables

Observational evidence for escaping exoplanet atmospheres has been obtained for a few exoplanets to date. It comes from strong transit signals detected in the ultraviolet, most notably in the wings of the hydrogen Lyman-$\alpha$ (Ly$\alpha$) line. However, the core of the Ly$\alpha$ line is often heavily affected by interstellar absorption and geocoronal emission, limiting the information about the atmosphere that can be extracted from that part of the spectrum. Transit observations in atomic lines that are (a) sensitive enough to trace the rarefied gas in the planetary wind and (b) do not suffer from significant extinction by the interstellar medium could enable more detailed observations, and thus provide better constraints on theoretical models of escaping atmospheres. The absorption line of a metastable state of helium at 10830 \AA\ could satisfy both of these conditions for some exoplanets. We develop a simple 1D model of escaping planetary atmospheres containing hydrogen and helium. We use it to calculate the density profile of helium in the 2$^3$S metastable excited state and the expected in-transit absorption at 10830 \AA\ for two exoplanets known to have escaping atmospheres. Our results indicate that exoplanets similar to GJ 436b and HD 209458b should exhibit enhanced transit depths at 10830 \AA, with $\sim 8\%$ and $\sim 2\%$ excess absorption in the line core, respectively., Comment: New version matches the published version

In the first paper of this series, we proposed a novel method to probe large-scale intergalactic magnetic fields during the cosmic Dark Ages, using 21-cm tomography. This method relies on the effect of spin alignment of hydrogen atoms in a cosmological setting, and on the effect of magnetic precession of the atoms on the statistics of the 21-cm brightness-temperature fluctuations. In this paper, we forecast the sensitivity of future tomographic surveys to detecting magnetic fields using this method. For this purpose, we develop a minimum-variance estimator formalism to capture the characteristic anisotropy signal using the two-point statistics of the brightness-temperature fluctuations. We find that, depending on the reionization history, and subject to the control of systematics from foreground subtraction, an array of dipole antennas in a compact-grid configuration with a collecting area slightly exceeding one square kilometer can achieve a $1\sigma$ detection of $\sim$$10^{-21}$ Gauss comoving (scaled to present-day value) within three years of observation. Using this method, tomographic 21-cm surveys could thus probe ten orders of magnitude below current CMB constraints on primordial magnetic fields, and provide exquisite sensitivity to large-scale magnetic fields in situ at high redshift., Comment: 19 pages, 8 figures; key results are in Figures 4 and 5; code and other materials are available at https://github.com/veragluscevic/pmfs; to be submitted to PRD

Cosmological perturbation theory is a powerful tool to predict the statistics of large-scale structure in the weakly non-linear regime, but even at 1-loop order it results in computationally expensive mode-coupling integrals. Here we present a fast algorithm for computing 1-loop power spectra of quantities that depend on the observer's orientation, thereby generalizing the FAST-PT framework (McEwen et al., 2016) that was originally developed for scalars such as the matter density. This algorithm works for an arbitrary input power spectrum and substantially reduces the time required for numerical evaluation. We apply the algorithm to four examples: intrinsic alignments of galaxies in the tidal torque model; the Ostriker-Vishniac effect; the secondary CMB polarization due to baryon flows; and the 1-loop matter power spectrum in redshift space. Code implementing this algorithm and these applications is publicly available at https://github.com/JoeMcEwen/FAST-PT ., Comment: 32 pages, 5 figures, 4 tables. Minor changes. Published in JCAP. Code available at https://github.com/JoeMcEwen/FAST-PT

Correlations between intrinsic shear and the density field on large scales, a potentially important contaminant for cosmic shear surveys, have been robustly detected at low redshifts with bright galaxies in SDSS data. Here we present a more detailed characterization of this effect, which can cause anti-correlations between gravitational lensing shear and intrinsic ellipticity (GI correlations). This measurement uses 36278 Luminous Red Galaxies (LRGs) from the SDSS spectroscopic sample with 0.15 3sigma detections of the effect for all galaxy subsamples within the SDSS LRG sample; for the 2SLAQ sample, we find a 2sigma detection for a bright subsample, and no detection for a fainter subsample. Fitting formulae are provided for the scaling of the GI correlations with luminosity, transverse separation, and redshift. We estimate contamination in the measurement of sigma_8 for future cosmic shear surveys on the basis of the fitted dependence of GI correlations on galaxy properties. We find contamination to the power spectrum ranging from -1.5 (optimistic) to -33 per cent (pessimistic) for a toy cosmic shear survey using all galaxies to a depth of R=24 using scales l~500. This corresponds to a bias in sigma_8 of Delta sigma_8=-0.004 (optimistic), -0.02 (central), or -0.10 (pessimistic). We provide a prescription for inclusion of this error in cosmological parameter estimation codes. The principal uncertainty is in the treatment of the L

The 21-cm hyperfine line of atomic hydrogen (HI) is a promising probe of the cosmic dark ages. In past treatments of 21-cm radiation it was assumed the hyperfine level populations of HI could be characterized by a velocity-independent ``spin temperature'' T_s determined by a competition between 21-cm radiative transitions, spin-changing collisions, and (at lower redshifts) Lyman-alpha scattering. However we show here that, if the collisional time is comparable to the radiative time, the spin temperature will depend on atomic velocity, T_s=T_s(v), and one must replace the usual hyperfine level rate equations with a Boltzmann equation describing the spin and velocity dependence of the HI distribution function. We construct here the Boltzmann equation relevant to the cosmic dark ages and solve it using a basis-function method. Accounting for the actual spin-resolved atomic velocity distribution results in up to a 2 per cent suppression of the 21-cm emissivity, and a redshift and angular-projection dependent suppression or enhancement of the linear power spectrum of 21-cm fluctuations of up to 5 per cent. The effect on the 21-cm line profile is more dramatic -- its full-width at half maximum (FWHM) can be enhanced by up to 60 per cent relative to the velocity-independent calculation. We discuss the implications for 21-cm tomography of the dark ages.