arXiv subjects

Martin White

Publications and source records attributed to Martin White.

At least 199 records · Page 11Linked to original sources

arXiv2015

LUX likelihood and limits on spin-independent and spin-dependent WIMP couplings with LUXCalc

We present LUXCalc, a new utility for calculating likelihoods and deriving WIMP-nucleon coupling limits from the recent results of the LUX direct search dark matter experiment. After a brief review of WIMP-nucleon scattering, we derive LUX limits on the spin-dependent WIMP-nucleon couplings over a broad range of WIMP masses, under standard assumptions on the relevant astrophysical parameters. We find that, under these and other common assumptions, LUX excludes the entire spin-dependent parameter space consistent with a dark matter interpretation of DAMA's anomalous signal, the first time a single experiment has been able to do so. We also revisit the case of spin-independent couplings, and demonstrate good agreement between our results and the published LUX results. Finally, we derive constraints on the parameters of an effective dark matter theory in which a spin-1 mediator interacts with a fermionic WIMP and Standard Model fermions via axial-vector couplings. A detailed appendix describes the use of LUXCalc with standard codes to place constraints on generic dark matter theories.

hep-ph↗

arXiv2015

Reconstruction within the Zeldovich approximation

The Zeldovich approximation, 1st order Lagrangian perturbation theory, provides a good description of the clustering of matter and galaxies on large scales. The acoustic feature in the large-scale correlation function of galaxies imprinted by sound waves in the early Universe has been successfully used as a `standard ruler' to constrain the expansion history of the Universe. The standard ruler can be improved if a process known as density field reconstruction is employed. In this paper we develop the Zeldovich formalism to compute the correlation function of biased tracers in both real- and redshift-space using the simplest reconstruction algorithm with a Gaussian kernel and compare to N-body simulations. The model qualitatively describes the effects of reconstruction on the simulations, though its quantitative success depends upon how redshift-space distortions are handled in the reconstruction algorithm.

astro-ph.CO↗

arXiv2015

Voids in Lyα Forest Tomographic Maps

We present a new method of finding cosmic voids using tomographic maps of Lyα forest flux. We identify cosmological voids with radii of 2 - 12 $h^{-1}$Mpc in a large N-body simulation at $z = 2.5$, and characterize the signal of the high-redshift voids in density and Lyα forest flux. The void properties are similar to what has been found at lower redshifts, but they are smaller and have steeper radial density profiles. Similarly to what has been found for low-redshift voids, the radial velocity profiles have little scatter and agree very well with the linear theory prediction. We run the same void finder on an ideal Lyα flux field and tomographic reconstructions at various spatial samplings. We compare the tomographic map void catalogs to the density void catalog and find good agreement even with modest-sized voids ($r > 6 \, h^{-1}$Mpc). Using our simple void-finding method, the configuration of the ongoing CLAMATO survey covering 1 deg$^2$ would provide a sample of about 100 high-redshift voids. We also provide void-finding forecasts for larger area surveys, and discuss how these void samples can be used to test modified gravity models, study high-redshift void galaxies, and to make an Alcock-Paczynski measurement. To aid future work in this area, we provide public access to our simulation products, catalogs, and sample tomographic flux maps.

astro-ph.CO↗

arXiv2014

On Estimating Lyman-alpha Forest Correlations between Multiple Sightlines

The next frontier of Lyman-alpha forest studies is the reconstruction of 3D correlations from a dense sample of background sources. The measurement of 3D correlations has the potential to improve constraints on fundamental cosmological parameters, ionizing background models, and the reionization history. This study addresses the sensitivity of spectroscopic surveys to 3D correlations in the Lyman-alpha forest. We show that the sensitivity of a survey to this signal can be quantified by just a single number, a noise-weighted number density of sources on the sky. We investigate how the sensitivity of a spectroscopic quasar (or galaxy) survey scales as a function of its depth, area, and redshift. We propose a simple method for weighting sightlines with varying S/N levels to estimate the correlation function, and we show that this estimator generally performs nearly as well as the minimum variance quadratic estimator. In addition, we show that the sensitivity of a quasar survey to the flux correlation function is generally maximized if it observes each field just long enough to achieve S/N ~ 2 in a 1 A pixel on an L_* quasar while acquiring spectra for all quasars with L > L_*: Little is gained by integrating longer on the same targets or by including fainter quasars. We quantify how these considerations relate to constraints on the angular diameter distance, the curvature of space-time, and the reionization history.

astro-ph.CO↗

arXiv2014

The Zeldovich approximation

This year marks the 100th anniversary of the birth of Yakov Zel'dovich. Amongst his many legacies is the Zel'dovich approximation for the growth of large-scale structure, which remains one of the most successful and insightful analytic models of structure formation. We use the Zel'dovich approximation to compute the two-point function of the matter and biased tracers, and compare to the results of N-body simulations and other Lagrangian perturbation theories. We show that Lagrangian perturbation theories converge well and that the Zel'dovich approximation provides a good fit to the N-body results except for the quadrupole moment of the halo correlation function. We extend the calculation of halo bias to 3rd order and also consider non-local biasing schemes, none of which remove the discrepancy. We argue that a part of the discrepancy owes to an incorrect prediction of inter-halo velocity correlations. We use the Zel'dovich approximation to compute the ingredients of the Gaussian streaming model and show that this hybrid method provides a good fit to clustering of halos in redshift space down to scales of tens of Mpc.

astro-ph.CO↗

arXiv2014

Protocluster Discovery in Tomographic Ly$α$ Forest Flux Maps

We present a new method of finding protoclusters using tomographic maps of Ly$α$ Forest flux. We review our method of creating tomographic flux maps and discuss our new high performance implementation, which makes large reconstructions computationally feasible. Using a large N-body simulation, we illustrate how protoclusters create large-scale flux decrements, roughly 10 $h^{-1}$Mpc across, and how we can use this signal to find them in flux maps. We test the performance of our protocluster finding method by running it on the ideal, noiseless map and tomographic reconstructions from mock surveys, and comparing to the halo catalog. Using the noiseless map, we find protocluster candidates with about 90% purity, and recover about 75% of the protoclusters that form massive clusters ($> 3 \times 10^{14} \, h^{-1} M_{\odot}$). We construct mock surveys similar to the ongoing COSMOS Lyman-Alpha Mapping And Tomography Observations (CLAMATO) survey. While the existing data has an average sightline separation of 2.3 $h^{-1}$Mpc, we test separations of 2 - 6 $h^{-1}$Mpc to see what can be tolerated for our application. Using reconstructed maps from small separation mock surveys, the protocluster candidate purity and completeness are very close what was found in the noiseless case. As the sightline separation increases, the purity and completeness decrease, although they remain much higher than we initially expected. We extended our test cases to mock surveys with an average separation of 15 $h^{-1}$Mpc, meant to reproduce high source density areas of the BOSS survey. We find that even with such a large sightline separation, the method can still be used to find some of the largest protoclusters.

astro-ph.CO↗

arXiv2014

Tests of redshift-space distortions models in configuration space for the analysis of the BOSS final data release

Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for observing the build-up of cosmological structure, which depends both on the expansion rate of the Universe and our theory of gravity. In preparation for analysis of redshift-space distortions from the Baryon Oscillation Spectroscopic Survey (BOSS) final data release we compare a number of analytic and phenomenological `streaming' models, specified in configuration space, to mock catalogs derived in different ways from several N-body simulations. The galaxies in each mock catalog have properties similar to those of the higher redshift galaxies measured by BOSS but differ in the details of how small-scale velocities and halo occupancy are determined. We find that all of the analytic models fit the simulations over a limited range of scales while failing at small scales. We discuss which models are most robust and on which scales they return reliable estimates of the rate of growth of structure: we find that models based on some form of resummation can fit our N-body data for BOSS-like galaxies above $30\,h^{-1}$Mpc well enough to return unbiased parameter estimates.

astro-ph.CO↗

arXiv2014

Optimal Redshift Weighting For Baryon Acoustic Oscillations

Future baryon acoustic oscillation (BAO) surveys will survey very large volumes, covering wide ranges in redshift. We derive a set of redshift weights to compress the information in the redshift direction to a small number of modes. We suggest that such a compression preserves almost all of the signal for most cosmologies, while giving high signal-to-noise measurements for each combination. We present some toy models and simple worked examples. As an intermediate step, we give a precise meaning to the "effective redshift" of a BAO measurement.

astro-ph.CO↗

arXiv2014

Velocity Bias from the Small Scale Clustering of SDSS-III BOSS Galaxies

We present the measurements and modelling of the projected and redshift-space clustering of CMASS galaxies in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Data Release 11. For a volume-limited luminous red galaxy sample in the redshift range of $0.48<z<0.55$, we perform halo occupation distribution modelling of the small- and intermediate-scale ($0.1$--$60h^{-1}{\rm {Mpc}}$) projected and redshift-space two-point correlation functions, with an accurate model built on high resolution $N$-body simulations. To interpret the measured redshift-space distortions, the distribution of galaxy velocities must differ from that of the dark matter inside haloes of $\sim 10^{13}$--$10^{14}h^{-1}{\rm M_{\odot}}$, i.e. the data require the existence of galaxy velocity bias. Most notably, central galaxies on average are not at rest with respect to the core of their host haloes (defined by the inner 25% of particles around the halo potential minimum), but rather move around it with a 1D velocity dispersion of $0.22^{+0.03}_{-0.04}$ times that of the dark matter, implying a spatial offset from the centre at the level of $\lesssim$1% of the halo virial radius. The luminous satellite galaxies move more slowly than the dark matter, with velocities $0.86^{+0.08}_{-0.03}$ times those of the dark matter, which suggests that the velocity and spatial distributions of these satellites cannot both be unbiased. The constraints mainly arise from the Fingers-of-God effect at nonlinear scales and the smoothing to the Kaiser effect in the translinear regime; the robustness of the results is demonstrated by a variety of tests. In addition, no clear evidence is found for a strong luminosity dependence of the velocity bias. We discuss the implications of the existence of galaxy velocity bias for investigations of galaxy formation and cosmology.

astro-ph.CO↗

arXiv2014

Cross-correlation of cosmic far-infrared background anisotropies with large scale structures

We measure the cross-power spectra between luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS)-III Data Release Eight (DR8) and cosmic infrared background (CIB) anisotropies from Planck and data from the Improved Reprocessing (IRIS) of the Infrared Astronomical Satellite (IRAS) at 353, 545, 857, and 3000 GHz, corresponding to 850, 550, 350 and 100 micron, respectively, in the multipole range 100<l<1000. Using approximately 6.5 10^5 photometrically determined LRGs in 7760 deg^2 of the northern hemisphere in the redshift range 0.45 < z < 0.65, we model the far-infrared background (FIRB) anisotropies with an extended version of the halo model. With these methods, we confirm the basic picture obtained from recent analyses of FIRB anisotropies with Herschel and Planck, that the most efficient halo mass at hosting star forming galaxies is log(M_ eff/M_\odot)=12.84+/-0.15. We estimate the percentage of FIRB anisotropies correlated with LRGs as approximately 11.8 %, 3.9 %, 1.8 %, and 1.0 % of the total at 3000, 857, 545, and 353 GHz, respectively. At redshift z~0.55, the bias of FIRB galaxies with respect to the dark matter density field has the value b_{FIRB}~1.45, and the mean dust temperature of FIRB galaxies is T_d=26 K. Finally, we discuss the impact of present and upcoming cross-correlations with far-infrared background anisotropies on the determination of the global star formation history and the link between galaxies and dark matter.

astro-ph.CO↗

arXiv2014

Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2

We present the first observations of foreground Lyman-$α$ forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with $z\sim 2.3-2.8$ within a $5' \times 15'$ region of the COSMOS field. The transverse sightline separation is $\sim 2\,h^{-1}\mathrm{Mpc}$ comoving, allowing us to create a tomographic reconstruction of the 3D Ly$α$ forest absorption field over the redshift range $2.20\leq z\leq 2.45$. The resulting map covers $6\,h^{-1}\mathrm{Mpc} \times 14\,h^{-1}\mathrm{Mpc}$ in the transverse plane and $230\,h^{-1}\mathrm{Mpc}$ along the line-of-sight with a spatial resolution of $\approx 3.5\,h^{-1}\mathrm{Mpc}$, and is the first high-fidelity map of large-scale structure on $\sim\mathrm{Mpc}$ scales at $z>2$. Our map reveals significant structures with $\gtrsim 10\,h^{-1}\mathrm{Mpc}$ extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. Simulated reconstructions with the same sightline sampling, spectral resolution, and signal-to-noise ratio recover the salient structures present in the underlying 3D absorption fields. Using data from other surveys, we identified 18 galaxies with known redshifts coeval with our map volume enabling a direct comparison to our tomographic map. This shows that galaxies preferentially occupy high-density regions, in qualitative agreement with the same comparison applied to simulations. Our results establishes the feasibility of the CLAMATO survey, which aims to obtain Ly$α$ forest spectra for $\sim 1000$ SFGs over $\sim 1 \,\mathrm{deg}^2$ of the COSMOS field, in order to map out IGM large-scale structure at $\langle z \rangle \sim 2.3$ over a large volume $(100\,h^{-1}\mathrm{Mpc})^3$.

astro-ph.CO↗

arXiv2014

Comparing Simple Quasar Demographics Models

This paper explores several simple model variations for the connections among quasars, galaxies, and dark matter halos for redshifts 1 < z < 6. A key component of these models is that we enforce a self-consistent black hole (BH) history by tracking both BH mass and BH growth rate at all redshifts. We connect objects across redshift with a simple constant-number-density procedure, and choose a fiducial model with a relationship between BH and galaxy growth rates that is linear and evolves in a simple way with redshift. Within this fiducial model, we find the quasar luminosity function (QLF) by calculating an "intrinsic" luminosity based on either the BH mass or BH growth rate, and then choosing a model of quasar variability with either a lognormal or truncated power-law distribution of instantaneous luminosities. This gives four model variations, which we fit to the observed QLF at each redshift. With the best-fit models in hand, we undertake a detailed comparison of the four fiducial models, and explore changes to our fiducial model of the BH-galaxy relationship. Each model variation can successfully fit the observed QLF, the shape of which is generally set by the "intrinsic" luminosity at the faint end and by the scatter due to variability at the bright end. We focus on accounting for the reasons that physically different models can make such similar predictions, and on identifying what observational data or physical arguments are most essential in breaking the degeneracies among models.

astro-ph.CO↗

arXiv2014

A 2.5% measurement of the growth rate from small-scale redshift space clustering of SDSS-III CMASS galaxies

We perform the first fit to the anisotropic clustering of SDSS-III CMASS DR10 galaxies on scales of ~ 0.8 - 32 Mpc/h. A standard halo occupation distribution model evaluated near the best fit Planck LCDM cosmology provides a good fit to the observed anisotropic clustering, and implies a normalization for the peculiar velocity field of M ~ 2 x 10^13 Msun/h halos of f*sigma8(z=0.57) = 0.450 +/- 0.011. Since this constraint includes both quasi-linear and non-linear scales, it should severely constrain modified gravity models that enhance pairwise infall velocities on these scales. Though model dependent, our measurement represents a factor of 2.5 improvement in precision over the analysis of DR11 on large scales, f*sigma8(z=0.57) = 0.447 +/- 0.028, and is the tightest single constraint on the growth rate of cosmic structure to date. Our measurement is consistent with the Planck LCDM prediction of 0.480 +/- 0.010 at the ~1.9 sigma level. Assuming a halo mass function evaluated at the best fit Planck cosmology, we also find that 10% of CMASS galaxies are satellites in halos of mass M ~ 6 x 10^13 Msun/h. While none of our tests and model generalizations indicate systematic errors due to an insufficiently detailed model of the galaxy-halo connection, the precision of these first results warrant further investigation into the modeling uncertainties and degeneracies with cosmological parameters.

astro-ph.CO↗

arXiv2014

The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy samples

We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III (SDSS-III). Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately $8\,500$ square degrees and the redshift range $0.2<z<0.7$. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance $Λ$CDM cosmological model, the DR11 sample covers a volume of 13\,Gpc${}^3$ and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the baryon acoustic oscillation (BAO) feature. The acoustic features are detected at a significance of over $7\,σ$ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, $r_d$, which has a value of $r_{d,{\rm fid}}=149.28\,$Mpc in our fiducial cosmology. We find $D_V=(1264\pm25\,{\rm Mpc})(r_d/r_{d,{\rm fid}})$ at $z=0.32$ and $D_V=(2056\pm20\,{\rm Mpc})(r_d/r_{d,{\rm fid}})$ at $z=0.57$. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line-of-sight yields measurements at $z=0.57$ of $D_A=(1421\pm20\,{\rm Mpc})(r_d/r_{d,{\rm fid}})$ and $H=(96.8\pm3.4\,{\rm km/s/Mpc})(r_{d,{\rm fid}}/r_d)$. Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat cold dark matter model with a cosmological constant.

astro-ph.CO↗

arXiv2014

Observational Requirements for Lyman-alpha Forest Tomographic Mapping of Large-Scale Structure at z ~ 2

The z > 2 Lyman-alpha (Lya) forest traces the underlying dark-matter distribution on large scales and, given sufficient sightlines, can be used to create 3D maps of large-scale structure. We examine the observational requirements to construct such maps and estimate the signal-to-noise as a function of exposure time and sightline density. Sightline densities at z = 2.25 are n_los = [360, 1200,3300] deg^{-2} at limiting magnitudes of g =[24.0, 24.5,25.0], resulting in transverse sightline separations of d_perp = [3.6, 1.9, 1.2] h^{-1} Mpc, which roughly sets the reconstruction scale. We simulate these reconstructions using mock spectra with realistic noise properties, and find that spectra with S/N = 4 per angstrom can be used to generate maps that clearly trace the underlying dark-matter at overdensities of rho/ ~ 1. For the VLT/VIMOS spectrograph, exposure times t_exp = [4, 6, 10] hrs are sufficient for maps with spatial resolution epsilon_3d = [5.0, 3.2, 2.3] h^{-1} Mpc. Assuming ~ 250 h^{-1} Mpc is probed along the line-of-sight, 1 deg^2 of survey area would cover a comoving volume of ~ 10^6 h^{-3} Mpc^3 at =2.3, enabling efficient mapping of large volumes with 8-10m telescopes. These maps could be used to study galaxy environments, detect proto-clusters, and study the topology of large-scale structure at high-z.

astro-ph.CO↗

arXiv2014

The Clustering of Galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS): measuring growth rate and geometry with anisotropic clustering

We use the observed anisotropic clustering of galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 11 CMASS sample to measure the linear growth rate of structure, the Hubble expansion rate and the comoving distance scale. Our sample covers 8498 ${\rm deg}^2$ and encloses an effective volume of 6.0 ${\rm Gpc}^3$ at an effective redshift of $\bar{z} = 0.57$. We find $fσ_8 = 0.441 \pm 0.044$, $H = 93.1 \pm 3.0\ {\mathrm{km}\ \mathrm{s}^{-1} \mathrm{Mpc}^{-1}}$ and $D_{\rm A} = 1380 \pm 23\ {\rm Mpc}$ when fitting the growth and expansion rate simultaneously. When we fix the background expansion to the one predicted by spatially-flat $Λ$CDM model in agreement with recent Planck results, we find $fσ_8 = 0.447 \pm 0.028$ (6 per cent accuracy). While our measurements are generally consistent with the predictions of $Λ$CDM and General Relativity, they mildly favor models in which the strength of gravitational interactions is weaker than what is predicted by General Relativity. Combining our measurements with recent cosmic microwave background data results in tight constraints on basic cosmological parameters and deviations from the standard cosmological model. Separately varying these parameters, we find $w = -0.983 \pm 0.075$ (8 per cent accuracy) and $γ= 0.69 \pm 0.11$ (16 per cent accuracy) for the effective equation of state of dark energy and the growth rate index, respectively. Both constraints are in good agreement with the standard model values of $w=-1$ and $γ= 0.554$.

astro-ph.CO↗

arXiv2014

Using large galaxy surveys to distinguish z~0.5 quiescent galaxy models

One of the most striking properties of galaxies is the bimodality in their star-formation rates. A major puzzle is why any given galaxy is star-forming or quiescent, and a wide range of physical mechanisms have been proposed as solutions. We consider how observations, such as might be available in upcoming large galaxy surveys, might distinguish different galaxy quenching scenarios. To do this, we combine an N-body simulation and multiple prescriptions from the literature to create several quiescent galaxy mock catalogues. Each prescription uses a different set of galaxy properties (such as history, environment, centrality) to assign individual simulation galaxies as quiescent. We find how and how much the resulting quiescent galaxy distributions differ from each other, both intrinsically and observationally. In addition to tracing observational consequences of different quenching mechanisms, our results indicate which sorts of quenching models might be most readily disentangled by upcoming observations and which combinations of observational quantities might provide the most discriminatory power. Our observational measures are auto, cross, and marked correlation functions, pro- jected density distributions, and group multiplicity functions, which rely upon galaxy positions, stellar masses and of course quiescence. Although degeneracies between models are present for individual observations, using multiple observations in concert allows us to distinguish between all ten models we consider. In addition to identifying intrinsic and observational consequences of quiescence prescriptions and testing these quiescence models against each other and observations, these methods can also be used to validate colors (or other history and environment dependent properties) in simulated mock catalogues.

astro-ph.CO↗

arXiv2014

The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: galaxy clustering measurements in the low redshift sample of Data Release 11

We present the distance measurement to z = 0.32 using the 11th data release of the Sloan Digital Sky Survey-III Baryon Acoustic Oscillation Survey (BOSS). We use 313,780 galaxies of the low-redshift (LOWZ) sample over 7,341 square-degrees to compute $D_V = (1264 \pm 25)(r_d/r_{d,fid})$ - a sub 2% measurement - using the baryon acoustic feature measured in the galaxy two-point correlation function and power-spectrum. We compare our results to those obtained in DR10. We study observational systematics in the LOWZ sample and quantify potential effects due to photometric offsets between the northern and southern Galactic caps. We find the sample to be robust to all systematic effects found to impact on the targeting of higher-redshift BOSS galaxies, and that the observed north-south tensions can be explained by either limitations in photometric calibration or by sample variance, and have no impact on our final result. Our measurement, combined with the baryonic acoustic scale at z = 0.57, is used in Anderson et al. (2013a) to constrain cosmological parameters.

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