Clustering Amplitude Research Articles

Revisiting the clustering of narrow-line AGN in the local Universe: Joint dependence on stellar mass and colour

We investigate the clustering and dark halo properties for the narrow-line active galactic nuclei (AGN) in the SDSS, particularly examining the joint dependence on galaxy mass and color. AGN in galaxies with blue colors or massive red galaxies with M*>~10^{10.5}Msun are found to show almost identical clustering amplitudes at all scales to control galaxies of the same mass, color and structural parameters. This suggests AGN activity in blue galaxies or massive red galaxies is regulated by internal processes, with no correlation with environment. The antibias of AGN at scales between ~100kpc and a few Mpc, as found in Li et al. (2006) for the AGN as a whole, is observed only for the AGN hosted by galaxies with red colors and relatively low masses <10^{10.5}Msun. A simple halo model in which AGN are preferentially found at dark halo centers can reproduce the observational results, but requiring a mass-dependent central fraction which is a factor of ~4 higher than the fraction estimated from the SDSS group catalogue. The same group catalogue reveals that the host groups of AGN in red satellites tend to have lower halo masses than control galaxies, while the host groups of AGN in red centrals tend to form earlier, as indicated by a larger stellar mass gap between the two most massive galaxies in the groups. Our result implies that the mass assembly history of dark halos may play an additional role in the AGN activity in low-mass red galaxies.

Comparing approximate methods for mock catalogues and covariance matrices – III: bispectrum

We compare the measurements of the bispectrum and the estimate of its covariance obtained from a set of different methods for the efficient generation of approximate dark matter halo catalogs to the same quantities obtained from full N-body simulations. To this purpose we employ a large set of three-hundred realisations of the same cosmology for each method, run with matching initial conditions in order to reduce the contribution of cosmic variance to the comparison. In addition, we compare how the error on cosmological parameters such as linear and nonlinear bias parameters depends on the approximate method used for the determination of the bispectrum variance. As general result, most methods provide errors within 10% of the errors estimated from N-body simulations. Exceptions are those methods requiring calibration of the clustering amplitude but restrict this to two-point statistics. Finally we test how our results are affected by being limited to a few hundreds measurements from N-body simulation, and therefore to the bispectrum variance, by comparing with a larger set of several thousands realisations performed with one approximate method.

Comparing approximate methods for mock catalogues and covariance matrices – I. Correlation function

This paper is the first in a set that analyses the covariance matrices of clustering statistics obtained from several approximate methods for gravitational structure formation. We focus here on the covariance matrices of anisotropic two-point correlation function measurements. Our comparison includes seven approximate methods, which can be divided into three categories: predictive methods that follow the evolution of the linear density field deterministically (ICE-COLA, Peak Patch, and Pinocchio), methods that require a calibration with N-body simulations (Patchy and Halogen), and simpler recipes based on assumptions regarding the shape of the probability distribution function (PDF) of density fluctuations (log-normal and Gaussian density fields). We analyse the impact of using covariance estimates obtained from these approximate methods on cosmological analyses of galaxy clustering measurements, using as a reference the covariances inferred from a set of full N-body simulations. We find that all approximate methods can accurately recover the mean parameter values inferred using the N-body covariances. The obtained parameter uncertainties typically agree with the corresponding N-body results within 5% for our lower mass threshold, and 10% for our higher mass threshold. Furthermore, we find that the constraints for some methods can differ by up to 20% depending on whether the halo samples used to define the covariance matrices are defined by matching the mass, number density, or clustering amplitude of the parent N-body samples. The results of our configuration-space analysis indicate that most approximate methods provide similar results, with no single method clearly outperforming the others.

Emulating galaxy clustering and galaxy–galaxy lensing into the deeply non-linear regime: methodology, information, and forecasts

The combination of galaxy-galaxy lensing (GGL) with galaxy clustering is one of the most promising routes to determining the amplitude of matter clustering at low redshifts. We show that extending clustering+GGL analyses from the linear regime down to $\sim 0.5 \, h^{-1}$ Mpc scales increases their constraining power considerably, even after marginalizing over a flexible model of non-linear galaxy bias. Using a grid of cosmological N-body simulations, we construct a Taylor-expansion emulator that predicts the galaxy autocorrelation $\xi_{\text{gg}}(r)$ and galaxy-matter cross-correlation $\xi_{\text{gm}}(r)$ as a function of $\sigma_8$, $\Omega_m$, and halo occupation distribution (HOD) parameters, which are allowed to vary with large scale environment to represent possible effects of galaxy assembly bias. We present forecasts for a fiducial case that corresponds to BOSS LOWZ galaxy clustering and SDSS-depth weak lensing (effective source density $\sim 0.3$ arcmin$^{-2}$). Using tangential shear and projected correlation function measurements over $0.5 \leq r_p \leq 30 \, h^{-1}$ Mpc yields a 1.8% constraint on the parameter combination $\sigma_8\Omega_m^{0.58}$, a factor of two better than a constraint that excludes non-linear scales ($r_p > 2 \, h^{-1}$ Mpc, $4 \, h^{-1}$ Mpc for $\gamma_t,w_p$). Much of this improvement comes from the non-linear clustering information, which breaks degeneracies among HOD parameters that would otherwise degrade the inference of matter clustering from GGL. Increasing the effective source density to $3$ arcmin$^{-2}$ sharpens the constraint on $\sigma_8\Omega_m^{0.58}$ by a further factor of two. With robust modeling into the non-linear regime, low-redshift measurements of matter clustering at the 1-percent level with clustering+GGL alone are well within reach of current data sets such as those provided by the Dark Energy Survey.

Abundance of peaks and dips in 3D mass and halo density fields: a test for cosmology

Using cosmological N-body simulations, we study the abundance of local maxima (peaks) and minima (dips) identified in the smoothed distribution of halos and dark matter (DM) on scales of $10-100$s Mpcs. The simulations include Gaussian and local-type $f_{\rm NL}$ non-Gaussian initial conditions. The expression derived in the literature for the abundance (irrespective of height) of peaks for Gaussian fields is surprisingly accurate for the evolved halo and DM density fields for all initial conditions considered. Furthermore, the height distribution is very well fitted by a log-normal on quasi-linear scales. The abundance as a function of scale depends on the cosmological parameters ($H_0$ and background matter densities) through the shape of the power spectrum, but it is insensitive to the clustering amplitude. Further, the abundance in the smoothed halo distribution is substantially different in the non-Gaussian from the Gaussian simulations. The interpretation of this effect is straightforward in terms of the scale dependence of halo bias in non-Gaussian models. The abundance of extrema extracted from three-dimensional large galaxy redshift surveys could be a competitive probe of the cosmological parameters and initial non-Gaussianity. It breaks the degeneracy between $f_{\rm NL}$ and the clustering amplitude, making it complementary to counts of galaxy clusters and peaks in weak-lensing maps.

Mapping the Real Space Distributions of Galaxies in SDSS DR7. II. Measuring the Growth Rate, Clustering Amplitude of Matter, and Biases of Galaxies at Redshift 0.1

Abstract We extend the real-space mapping method developed in Shi et al. so that it can be applied to flux-limited galaxy samples. We use an ensemble of mock catalogs to demonstrate the reliability of this extension, showing that it allows for an accurate recovery of the real-space correlation functions and galaxy biases. We also demonstrate that, using an iterative method applied to intermediate-scale clustering data, we can obtain an unbiased estimate of the growth rate of structure , which is related to the clustering amplitude of matter, to an accuracy of ∼10%. Applying this method to the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7), we construct a real-space galaxy catalog spanning the redshift range 0.01 ≤ z ≤ 0.2, which contains 584,473 galaxies in the northern Galactic cap. Using these data, we infer at a median redshift z = 0.1, which is consistent with the WMAP9 cosmology at the 1σ level. By combining this measurement with the real-space clustering of galaxies and with galaxy–galaxy weak lensing measurements for the same sets of galaxies, we are able to break the degeneracy between f, σ 8, and b. From the SDSS DR7 data alone, we obtain the following cosmological constraints at redshift z = 0.1: f = , σ 8 = , and b = , , , and for galaxies within different absolute magnitude bins , [−22, 0, −21.0], [−21.0, −20.0], and [−20.0, −19.0], respectively.

KiDS+2dFLenS+GAMA: testing the cosmological model with the EG statistic

We present a new measurement of $E_{\rm G}$, which combines measurements of weak gravitational lensing, real-space galaxy clustering and redshift space distortions. This statistic was proposed as a consistency test of General Relativity (GR) that is insensitive to linear, deterministic galaxy bias and the matter clustering amplitude. We combine deep imaging data from KiDS with overlapping spectroscopy from 2dFLenS, BOSS DR12 and GAMA and find $E_{\rm G}(\overline{z}=0.267)=0.43 \pm 0.13$ (GAMA), $E_{\rm G}(\overline{z}=0.305)=0.27 \pm 0.08$ (LOWZ+2dFLOZ) and $E_{\rm G}(\overline{z}=0.554)=0.26 \pm 0.07$ (CMASS+2dFHIZ). We demonstrate that the existing tension in the value of the matter density parameter hinders the robustness of this statistic as solely a test of GR. We find that our $E_{\rm G}$ measurements, as well as existing ones in the literature, favour a lower matter density cosmology than the Cosmic Microwave Background. For a flat $\Lambda$CDM Universe and assuming GR, we find $\Omega_{\rm m}(z=0)=0.25\pm0.03$. With this paper we publicly release the 2dFLenS dataset at: \url{http://2dflens.swin.edu.au}.

Galaxy And Mass Assembly (GAMA): the signatures of galaxy interactions as viewed from small-scale galaxy clustering

Statistical studies of galaxy-galaxy interactions often utilise net change in physical properties of progenitors as a function of the separation between their nuclei to trace both the strength and the observable timescale of their interaction. In this study, we use two-point auto, cross and mark correlation functions to investigate the extent to which small-scale clustering properties of star forming galaxies can be used to gain physical insight into galaxy-galaxy interactions between galaxies of similar optical brightness and stellar mass. The Halpha star formers, drawn from the highly spatially complete Galaxy And Mass Assembly (GAMA) survey, show an increase in clustering on small separations. Moreover, the clustering strength shows a strong dependence on optical brightness and stellar mass, where (1) the clustering amplitude of optically brighter galaxies at a given separation is larger than that of optically fainter systems, (2) the small scale clustering properties (e.g. the strength, the scale at which the signal relative to the fiducial power law plateaus) of star forming galaxies appear to differ as a function of increasing optical brightness of galaxies. According to cross and mark correlation analyses, the former result is largely driven by the increased dust content in optically bright star forming galaxies. The latter could be interpreted as evidence of a correlation between interaction-scale and optical brightness of galaxies, where physical evidence of interactions between optically bright star formers, likely hosted within relatively massive halos, persist over larger separations than those between optically faint star formers.

The detection of the imprint of filaments on cosmic microwave background lensing

Galaxy redshift surveys, such as 2dF, SDSS, 6df, GAMA and VIPERS, have shown that the spatial distribution of matter forms a rich web, known as the cosmic web. The majority of galaxy survey analyses measure the amplitude of galaxy clustering as a function of scale, ignoring information beyond a small number of summary statistics. Since the matter density field becomes highly non-Gaussian as structure evolves under gravity, we expect other statistical descriptions of the field to provide us with additional information. One way to study the non-Gaussianity is to study filaments, which evolve non-linearly from the initial density fluctuations produced in the primordial Universe. In our study, we report the first detection of CMB (Cosmic Microwave Background) lensing by filaments and we apply a null test to confirm our detection. Furthermore, we propose a phenomenological model to interpret the detected signal and we measure how filaments trace the matter distribution on large scales through filament bias, which we measure to be around 1.5. Our study provides a new scope to understand the environmental dependence of galaxy formation. In the future, the joint analysis of lensing and Sunyaev-Zel'dovich observations might reveal the properties of `missing baryons', the vast majority of the gas which resides in the intergalactic medium and has so far evaded most observations.

The effects of assembly bias on the inference of matter clustering from galaxy–galaxy lensing and galaxy clustering

The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function $\langle N_\text{cen}(M_\text{min}) \rangle$ for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, $r_{gm} \equiv \xi_{gm} \cdot [ \xi_{mm} \xi_{gg} ]^{-1/2}$, is insensitive to assembly bias on scales $r \gtrsim 1 \; h^{-1}\text{Mpc}$, even though $\xi_{gm} $ and $\xi_{gg} $ are both affected individually. We can therefore recover the correct $\xi_{mm} $ from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For $M_r \leq -19$ or $M_r \leq -20$ samples the recovery of $\xi_{mm}$ is accurate to 2% or better. For a sample of red $M_r \leq -20$ galaxies we achieve 2% recovery at $r \gtrsim 2\;h^{-1}\text{Mpc}$ with EDHOD modeling but lower accuracy at smaller scales or with a standard HOD fit.

The environment and host haloes of the brightest z ∼ 6 Lyman-break galaxies

By studying the large-scale structure of the bright high-redshift Lyman-break galaxy (LBG) population it is possible to gain an insight into the role of environment in galaxy formation physics in the early Universe. We measure the clustering of a sample of bright (-22.7<M_UV<-21.125) LBGs at z~6 and use a halo occupation distribution (HOD) model to measure their typical halo masses. We find that the clustering amplitude and corresponding HOD fits suggests that these sources are highly biased (b~8) objects in the densest regions of the high-redshift Universe. Coupled with the observed rapid evolution of the number density of these objects, our results suggest that the shape of high luminosity end of the luminosity function is related to feedback processes or dust obscuration in the early Universe - as opposed to a scenario where these sources are predominantly rare instances of the much more numerous M_UV ~ -19 population of galaxies caught in a particularly vigorous period of star formation. There is a slight tension between the number densities and clustering measurements, which we interpret this as a signal that a refinement of the model halo bias relation at high redshifts or the incorporation of quasi-linear effects may be needed for future attempts at modelling the clustering and number counts. Finally, the difference in number density between the fields (UltraVISTA has a surface density ~1.8 times greater than UDS) is shown to be consistent with the cosmic variance implied by the clustering measurements.

The VIMOS Ultra Deep Survey

We present a study of the dependence of galaxy clustering on luminosity and stellar mass in the redshift range 2 &lt; z &lt; 3.5 using 3236 galaxies with robust spectroscopic redshifts from the VIMOS Ultra Deep Survey (VUDS), covering a total area of 0.92 deg2. We measured the two-point real-space correlation function wp(rp) for four volume-limited subsamples selected by stellar mass and four volume-limited subsamples selected by MUV absolute magnitude. We find that the scale-dependent clustering amplitude r0 significantly increases with increasing luminosity and stellar mass. For the least luminous galaxies (MUV &lt; −19.0), we measured a correlation length r0 = 2.87 ± 0.22 h−1 Mpc and slope γ = 1.59 ± 0.07, while for the most luminous (MUV &lt; −20.2) r0 = 5.35 ± 0.50 h−1 Mpc and γ = 1.92 ± 0.25. These measurements correspond to a strong relative bias between these two subsamples of Δb∕b* = 0.43. Fitting a five-parameter halo occupation distribution (HOD) model, we find that the most luminous (MUV &lt; −20.2) and massive (M⋆ &gt; 1010 h−1 M⊙) galaxies occupy the most massive dark matter haloes with ⟨Mh⟩ = 1012.30 h−1 M⊙. Similar to the trends observed at lower redshift, the minimum halo mass Mmin depends on the luminosity and stellar mass of galaxies and grows from Mmin = 109.73 h−1 M⊙ to Mmin = 1011.58 h−1 M⊙ from the faintest to the brightest among our galaxy sample, respectively. We find the difference between these halo masses to be much more pronounced than is observed for local galaxies of similar properties. Moreover, at z ~ 3, we observe that the masses at which a halo hosts, on average, one satellite and one central galaxy is M1 ≈ 4Mmin over all luminosity ranges, which is significantly lower than observed at z ~ 0; this indicates that the halo satellite occupation increases with redshift. The luminosity and stellar mass dependence is also reflected in the measurements of the large-scale galaxy bias, which we model as bg,HOD (&gt;L) = 1.92 + 25.36(L/L*)7.01. We conclude our study with measurements of the stellar-to-halo mass ratio (SHMR). We observe a significant model-observation discrepancy for low-mass galaxies, suggesting a higher than expected star formation efficiency of these galaxies.

The Galaxy–Halo Connection for as Revealed by the Spitzer Matching Survey of the UltraVISTA Ultra-deep Stripes

Abstract The Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) provides unparalleled depth at 3.6 and 4.5 μm over ∼0.66 deg2 of the COSMOS field, allowing precise photometric determinations of redshift and stellar mass. From this unique data set we can connect galaxy samples, selected by stellar mass, to their host dark matter halos for , filling in a large hitherto unexplored region of the parameter space. To interpret the observed galaxy clustering, we use a phenomenological halo model, combined with a novel method to account for uncertainties arising from the use of photometric redshifts. We find that the satellite fraction decreases with increasing redshift and that the clustering amplitude (e.g., comoving correlation length/large-scale bias) displays monotonic trends with redshift and stellar mass. Applying ΛCDM halo mass accretion histories and cumulative abundance arguments for the evolution of stellar mass content, we propose pathways for the coevolution of dark matter and stellar mass assembly. Additionally, we are able to estimate that the halo mass at which the ratio of stellar-to-halo mass is maximized is at . This peak halo mass is here inferred for the first time from stellar mass-selected clustering measurements at , and it implies a mild evolution of this quantity for , consistent with constraints from abundance-matching techniques.

Dark Energy Survey Year 1 results: the impact of galaxy neighbours on weak lensing cosmology with im3shape

We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The hoopoe image simulations include realistic blending, galaxy positions, and spatial variations in depth and PSF properties. Using the im3shape maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of $m \sim 0.03 - 0.09$ in the DES Y1 im3shape catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies $n_\mathrm{eff}$ of 30%. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude $S_8\equiv \sigma_8 (\Omega _\mathrm{m} /0.3)^{0.5}$ by $2 \sigma$ towards low values. Finally, we use the hoopoe simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias. We find the impact on the recovered $S_8$ of ignoring such correlations to be subdominant to statistical error at the current level of precision.

A Forecast for the Detection of the Power Asymmetry from Galaxy Surveys

Abstract We investigate the possibility of detecting a hemispherical power asymmetry in redshift surveys that is similar to that first reported in cosmic microwave background observations. We assume the hemispherical asymmetry arises from a linear gradient in comoving coordinates in the perturbation amplitude. We predict the resulting clustering of galaxy or galaxy cluster tracers using an excursion set approach; doing so accounts for the variation of both the underlying clustering and the tracer bias. Based on the predicted variation of the clustering of tracers, we perform a Fisher matrix forecast of the galaxy clustering amplitude and calculate the statistical significance for ideal surveys and planned surveys. The results indicate that the Dark Energy Spectroscopic Instrument (DESI) galaxy survey would be able to detect this signal with higher than 3σ significance if the asymmetry does exist. We also investigate the amplitude and scale dependence of the above result. The DESI galaxy survey can probe the dipole amplitude higher than 0.04, which correspond to a ±4% difference of the temperature fluctuation along and opposite the dipole direction, at least at the 2σ level. Additionally, we investigate a modulation of the power spectrum that exhibits asymmetry only for large scales. This modulation is potentially detectable. For Milky Way galaxy mass tracers, the scale-dependent modulation yields a larger change in the large-scale power spectrum than it does a scale-independent modulation because the former does not alter the bias.

IHC Posters - Thursday and Friday.

Objectives: Visual system abnormalities in migraine are linked to symptoms like photophobia and the visual aura. Little is known about the mechanisms contributing to these visual system alterations. Processing of visual input by the brain is a highly nonlinear operation, involving complex interactions among cortical and subcortical neuronal networks. Timing of this process can be estimated by analysing the cortical response to external light input at different frequencies. Using a sum-of-sinusoid light signal, instead of the classic pulse train, as input and novel EEG analyses it is possible to assess the time delay and frequency domain response. Here we investigate nonlinear visual processing in subgroups of migraine patients and headache-free participants. Methods: Migraine patients with aura, without aura and healthy participants (N = 10/group) were subjected to bi-sinusoidal light stimulation for 320 1 sec-epochs, while scalp EEG was recorded at the occipital, parietal and frontal lobes. Light stimulus frequencies were chosen to guarantee no overlap of their harmonic and intermodulation frequencies for different orders of nonlinearity. Nonlinear interactions and time delay from stimulus to cortical EEG response were analysed in the frequency domain using novel phase clustering measures and amplitude spectral measures. Results: Higher harmonic and intermodulation interactions were detected between visual input and cortical responses. Amplitude spectrum and phase clustering responses differed per order and group. Migraine patients with aura showed a decreased time delay only at the occipital lobe compared to healthy controls and migraine patients without aura. Conclusion: Visual processing is altered in migraine patients with aura compared to healthy controls and patients without aura. Furthermore, we demonstrated the potential of quantifying nonlinear interactions and temporal dynamics in the visual system using sum-of-sinusoid light stimulation. We are able to uncover alterations in visual processing in the context of neurological disease.

Constraining the H i–Halo Mass Relation from Galaxy Clustering

Abstract We study the dependence of galaxy clustering on H i mass using ∼16,000 galaxies with redshift in the range of 0.0025 &lt; z &lt; 0.05 and H i mass of M H I &gt; 10 8 M ☉ , drawn from the 70% complete sample of the Arecibo Legacy Fast ALFA survey. We construct subsamples of galaxies with M H I above different thresholds and make volume-limited clustering measurements in terms of three statistics: the projected two-point correlation function, the projected cross-correlation function with respect to a reference sample, and the redshift-space monopole moment. In contrast to previous studies, which found no/weak H i mass dependence, we find both the clustering amplitudes on scales above a few megaparsecs and the bias factors to increase significantly with increasing H i mass for M H I &gt; 10 9 M ☉ . For H i mass thresholds below ∼ 10 9 M ☉ , the inferred galaxy bias factors are systematically lower than the minimum halo bias from mass-selected halo samples. We extend the simple halo model, in which the galaxy content is only determined by halo mass, by including the halo formation time as an additional parameter. A model that puts H i-rich galaxies into halos that formed late can reproduce the clustering measurements reasonably well. We present the implications of our best-fitting model on the correlation of H i mass with halo mass and formation time, as well as the halo occupation distributions and H i mass functions for central and satellite galaxies. These results are compared with the predictions from semianalytic galaxy formation models and hydrodynamic galaxy formation simulations.

The VIMOS Public Extragalactic Redshift Survey (VIPERS)

We present measurements of the growth rate of cosmological structure from the modelling of the anisotropic galaxy clustering measured in the final data release of the VIPERS survey. The analysis is carried out in configuration space and based on measurements of the first two even multipole moments of the anisotropic galaxy auto-correlation function, in two redshift bins spanning the range $0.5 < z < 1.2$. We provide robust and cosmology-independent corrections for the VIPERS angular selection function, allowing recovery of the underlying clustering amplitude at the percent level down to the Mpc scale. We discuss several improvements on the non-linear modelling of redshift-space distortions (RSD) and perform detailed tests of a variety of approaches against a set of realistic VIPERS-like mock realisations. This includes using novel fitting functions to describe the velocity divergence and density power spectra $P_{\theta\theta}$ and $P_{\delta\theta}$ that appear in RSD models. These tests show that we are able to measure the growth rate with negligible bias down to separations of $5h^{-1}Mpc$. Interestingly, the application to real data shows a weaker sensitivity to the details of non-linear RSD corrections compared to mock results. We obtain consistent values for the growth rate times the matter power spectrum normalisation parameter of $f\sigma_8=0.55\pm 0.12$ and $0.40\pm0.11$ at effective redshifts of $z = 0.6$ and $z=0.86$ respectively. These results are in agreement with standard cosmology predictions assuming Einstein gravity in a $\Lambda \rm{CDM}$ background.

The FMOS-COSMOS Survey of Star-forming Galaxies at Z ∼ 1.6. V: Properties of Dark Matter Halos Containing Hα Emitting Galaxies

Abstract We study the properties of dark matter halos that contain star-forming galaxies at 1.43 ≤ z ≤ 1.74, using the FMOS-COSMOS survey. The sample consists of 516 objects with a detection of the Hα emission line, which represent the star forming population at this epoch, having a stellar mass range of 109.57 ≤ M */M ⊙ ≲ 1011.4 and a star-formation rate range of 15 ≲ SFR/(M ⊙ yr−1) ≲ 600. We measure the projected two-point correlation function while carefully taking into account observational biases, and find a significant clustering amplitude at scales of 0.04–10 h −1 cMpc, with a correlation length and a bias . We interpret our clustering measurement using a halo occupation distribution model. The sample galaxies appear to reside in halos with mass on average, which will likely become present-day halos of mass M h (z = 0) ∼ 2 × 1013 h −1 M ⊙, equivalent to the typical halo mass scale of galaxy groups. We then confirm the decline of the stellar-to-halo mass ratio at M h &lt; 1012 M ⊙, finding M */M h ≈ 5 × 10−3 at M h = 7. 5 × 1011 M ⊙, which is lower by a factor of 2–4 than those measured at higher masses (M h ∼ 1012–13 M ⊙). Finally, we use our results to illustrate the future capabilities of Subaru’s Prime-Focus Spectrograph, a next-generation instrument that will provide strong constraints on the galaxy-formation scenario by obtaining precise measurements of galaxy clustering at z &gt; 1.

The Correlation between Halo Mass and Stellar Mass for the Most Massive Galaxies in the Universe

Abstract We present measurements of the clustering of galaxies as a function of their stellar mass in the Baryon Oscillation Spectroscopic Survey. We compare the clustering of samples using 12 different methods for estimating stellar mass, isolating the method that has the smallest scatter at fixed halo mass. In this test, the stellar mass estimate with the smallest errors yields the highest amplitude of clustering at fixed number density. We find that the PCA stellar masses of Chen et al. clearly have the tightest correlation with halo mass. The PCA masses use the full galaxy spectrum, differentiating them from other estimates that only use optical photometric information. Using the PCA masses, we measure the large-scale bias as a function of for galaxies with , correcting for incompleteness at the low-mass end of our measurements. Using the abundance matching ansatz to connect dark matter halo mass to stellar mass, we construct theoretical models of that match the same stellar mass function but have different amounts of scatter in stellar mass at fixed halo mass, . Using this approach, we find . This value includes both intrinsic scatter as well as random errors in the stellar masses. To partially remove the latter, we use repeated spectra to estimate statistical errors on the stellar masses, yielding an upper limit to the intrinsic scatter of 0.16 dex.