scholarly journals The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: GLAM-QPM mock galaxy catalogues for the emission line galaxy sample

2020 ◽  
Vol 498 (4) ◽  
pp. 5251-5262 ◽  
Author(s):  
Sicheng Lin ◽  
Jeremy L Tinker ◽  
Anatoly Klypin ◽  
Francisco Prada ◽  
Michael R Blanton ◽  
...  
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Small Scale ◽  
Selection Function ◽  
Number Density ◽  
Acoustic Oscillations ◽  
Systematic Analysis ◽  
Galaxy Sample ◽  
Halo Occupation Distribution ◽  
Line Galaxy

ABSTRACT We present 2000 mock galaxy catalogues for the analysis of baryon acoustic oscillations (BAOs) in the Emission Line Galaxy (ELG) sample of the extended Baryon Oscillation Spectroscopic Survey Data Release 16 (eBOSS DR16). Each mock catalogue has a number density of $6.7 \times 10^{-4} h^3 \rm Mpc^{-3}$, covering a redshift range from 0.6 to 1.1. The mocks are calibrated to small-scale eBOSS ELG clustering measurements at scales of $\lesssim 30\, h^{-1}$Mpc. The mock catalogues are generated using a combination of GaLAxy Mocks (GLAM) simulations and the quick particle-mesh (QPM) method. GLAM simulations are used to generate the density field, which is then assigned dark matter haloes using the QPM method. Haloes are populated with galaxies using a halo occupation distribution. The resulting mocks match the survey geometry and selection function of the data, and have slightly higher number density that allows room for systematic analysis. The large-scale clustering of mocks at the BAO scale is consistent with data and we present the correlation matrix of the mocks.

scholarly journals The completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: large-scale structure catalogues and measurement of the isotropic BAO between redshift 0.6 and 1.1 for the Emission Line Galaxy Sample

2020 ◽  
Vol 500 (3) ◽  
pp. 3254-3274
Author(s):  
Anand Raichoor ◽  
Arnaud de Mattia ◽  
Ashley J Ross ◽  
Cheng Zhao ◽  
Shadab Alam ◽  
...  
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Sloan Digital Sky Survey ◽  
Acoustic Oscillations ◽  
Galaxy Sample ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Line Galaxy

ABSTRACT We present the Emission Line Galaxy (ELG) sample of the extended Baryon Oscillation Spectroscopic Survey from the Sloan Digital Sky Survey IV Data Release 16. We describe the observations and redshift measurement for the 269 243 observed ELG spectra, and then present the large-scale structure catalogues, used for the cosmological analysis, and made of 173 736 reliable spectroscopic redshifts between 0.6 and 1.1. We perform a spherically averaged baryon acoustic oscillations (BAO) measurement in configuration space, with density field reconstruction: the data two-point correlation function shows a feature consistent with that of the BAO, the BAO model being only weakly preferred over a model without BAO (Δχ2 < 1). Fitting a model constrained to have a BAO feature provides a 3.2 per cent measurement of the spherically averaged BAO distance DV(zeff)/rdrag = 18.23 ± 0.58 at the effective redshift zeff = 0.845.

scholarly journals Removing imaging systematics from galaxy clustering measurements with Obiwan: application to the SDSS-IV extended Baryon Oscillation Spectroscopic Survey emission-line galaxy sample

2020 ◽  
Vol 499 (3) ◽  
pp. 3943-3960 ◽  
Author(s):  
Hui Kong ◽  
Kaylan J Burleigh ◽  
Ashley Ross ◽  
John Moustakas ◽  
Chia-Hsun Chuang ◽  
...  
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Three Dimensional ◽  
Selection Function ◽  
Imaging Data ◽  
Scientific Analysis ◽  
Galaxy Sample ◽  
Systematic Biases ◽  
Redshift Survey ◽  
Emission Line Galaxies

ABSTRACT This work presents the application of a new tool, Obiwan, which uses image simulations to determine the selection function of a galaxy redshift survey and calculate three-dimensional (3D) clustering statistics. Obiwan relies on a forward model of the process by which images of the night sky are transformed into a 3D large-scale structure catalogue, and offers several advantages over more traditional map-based techniques – such as operating on individual exposures and adopting a maximum likelihood approach. The photometric pipeline automatically detects and models galaxies and then generates a catalogue of such galaxies with detailed information for each one of them, including their location, redshift, and so on. Systematic biases in the imaging data are therefore imparted into the catalogues and must be accounted for in any scientific analysis of their information content. Obiwan simulates this process for samples selected from the Legacy Surveys imaging data. This imaging data will be used to select target samples for the next-generation Dark Energy Spectroscopic Instrument (DESI) experiment. Here, we apply Obiwan to a portion of the SDSS-IV extended Baryon Oscillation Spectroscopic Survey emission-line galaxies (ELGs). Systematic biases in the data are clearly identified and removed. We compare the 3D clustering results to those obtained by the map-based approach applied to the complete eBOSS Data Release 16 (DR16) sample. We find the results are consistent, thereby validating the eBOSS DR16 ELG catalogues, which is used to obtain cosmological results.

Understanding the effectiveness of measures aiming to stabilize urban gullies in Congolese cities: a systematic analysis based on field surveys

2021 ◽  
Author(s):  
Eric Lutete Landu ◽  
Guy Ilombe Mawe ◽  
Charles Bielders ◽  
Fils Makanzu Imwangana ◽  
Olivier Dewitte ◽  
...  
Keyword(s):  
Large Scale ◽  
Clayey Soil ◽  
Waste Material ◽  
Control Measures ◽  
Household Waste ◽  
Small Scale ◽  
Systematic Analysis ◽  
Tropical Environments ◽  
Retention Ponds ◽  
Local Initiatives

<p>Many cities of the D.R. Congo are strongly affected by urban mega gullies. There are currently hundreds of such gullies in Kinshasa, Kikwit and Bukavu, representing a cumulative length of >200 km. Many of these gullies (typically tens of meters wide and deep) continue to expand, causing major damage to houses and other infrastructure and often claim human casualties. To mitigate these impacts, numerous measures are being implemented. The type and scale of these measures varies widely: from large structural measures like retention ponds to local initiatives of stabilizing gully heads with waste material. Nonetheless, earlier work indicates that an estimated 50% of the existing urban gullies continue to expand, despite the implementation of such measures. As such, we currently have very limited insight into the effectiveness of these measures and the overall best strategies to prevent and mitigate urban gullies. One reason for this is that most initiatives to stabilize urban gullies happen on a rather isolated basis and are rarely evaluated afterwards.</p><p>This work aims to improve our understanding of this issue. For this, we constructed a large inventory of measures implemented to stabilize urban gullies in Kinshasa, Kikwit and Bukavu and statistically confronted these measures with observed vegetation recovery and long-term gully expansion rates (derived from high-resolution imagery over a period of >14 years). Our preliminary results (based on a dataset of > 900 urban gullies) shows that the most commonly applied measures are revegetation and reinforcement of gully heads with sandbags or household waste material (implemented in around 65% of the cases). Retention ponds in streets and infiltration pits on house parcels are also frequently implemented (around 25% of the cases). Overall, techniques relying on vegetation are used relatively more frequently in regions with clayey soil, while techniques involving digging (e.g. infiltration pits) and topographic remodeling (e.g. gully reshaping by creation of terraces) are used mainly in sandy or sandy-clay areas. Surprisingly, small-scale local initiatives, such as stabilizing gully heads with household waste, often appear to have a higher effectivity than some large-scale civil engineering initiatives. However, such small-scale initiatives can come with important additional impacts (e.g. sanitation concerns). More research is needed to confirm these findings. Furthermore, the stability of gullies seems to be strongly linked to the degree of vegetation cover near the gully head. Nonetheless, it is not always clear if vegetation is the cause or the result of this stability. Overall, this study provides one of the first large scale assessments of the effectiveness of gully control measures in urban tropical environments. With this study, we hope to contribute to a better prevention and mitigation of this problem that affects many cities of the tropical Global South.</p>

scholarly journals An Emission-Line Galaxy Survey with the UK Schmidt Telescope

1987 ◽  
Vol 121 ◽  
pp. 53-55
Author(s):  
M. Kalafi ◽  
A. Savage ◽  
A.R. Good ◽  
R.D. Cannon ◽  
M.G. Yates
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Preliminary Investigation ◽  
Schmidt Telescope ◽  
Large Area ◽  
Number Magnitude ◽  
Emission Line Galaxies ◽  
Galaxy Populations ◽  
The Uk ◽  
Line Galaxy

The use of objective prisms in conjunction with the large area coverage afforded by Schmidt telescopes provides a very powerful means of detecting large numbers of emission-line galaxies, and allows one to study their large scale distribution. An important question that has yet to be fully addressed is the relationship between the number-magnitude distributions of the normal field galaxy and emission-line galaxy populations. A comparison such as this would effectively probe the evolution with time of these active objects. For example, study of the distant (z = 0.458) cluster of galaxies associated with 3C 295 (Dressler & Gunn 1983) indicates that emission-line objects may have been far more numerous in the past than at present. As a preliminary investigation in advance of a larger project, we report here on a search for emission-line galaxies in four United Kingdom 1.2m Schmidt Telescope (UKST) objective prism fields.

scholarly journals Voronoi volume function: a new probe of cosmology and galaxy evolution

2020 ◽  
Vol 495 (3) ◽  
pp. 3233-3251 ◽  
Author(s):  
Aseem Paranjape ◽  
Shadab Alam
Keyword(s):  
Dark Matter ◽  
Galaxy Evolution ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Voronoi Tessellation ◽  
Small Scale ◽  
Summary Statistics ◽  
Number Density ◽  
Volume Function ◽  
Space Effects

ABSTRACT We study the Voronoi volume function (VVF) – the distribution of cell volumes (or inverse local number density) in the Voronoi tessellation of any set of cosmological tracers (galaxies/haloes). We show that the shape of the VVF of biased tracers responds sensitively to physical properties such as halo mass, large-scale environment, substructure, and redshift-space effects, making this a hitherto unexplored probe of both primordial cosmology and galaxy evolution. Using convenient summary statistics – the width, median, and a low percentile of the VVF as functions of average tracer number density – we explore these effects for tracer populations in a suite of N-body simulations of a range of dark matter models. Our summary statistics sensitively probe primordial features such as small-scale oscillations in the initial matter power spectrum (as arise in models involving collisional effects in the dark sector), while being largely insensitive to a truncation of initial power (as in warm dark matter models). For vanilla cold dark matter (CDM) cosmologies, the summary statistics display strong evolution and redshift-space effects, and are also sensitive to cosmological parameter values for realistic tracer samples. Comparing the VVF of galaxies in the Galaxies & Mass Assembly (GAMA) survey with that of abundance-matched CDM (sub)haloes tentatively reveals environmental effects in GAMA beyond halo mass (modulo unmodelled satellite properties). Our exploratory analysis thus paves the way for using the VVF as a new probe of galaxy evolution physics as well as the nature of dark matter and dark energy.

scholarly journals The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: measurement of the BAO and growth rate of structure of the emission line galaxy sample from the anisotropic power spectrum between redshift 0.6 and 1.1

2020 ◽  
Author(s):  
Arnaud de Mattia ◽  
Vanina Ruhlmann-Kleider ◽  
Anand Raichoor ◽  
Ashley J Ross ◽  
Amélie Tamone ◽  
...  
Keyword(s):  
Growth Rate ◽  
Power Spectrum ◽  
Emission Line ◽  
Large Scale ◽  
Sloan Digital Sky Survey ◽  
Full Data ◽  
Data Set ◽  
Weak Preference ◽  
Galaxy Sample ◽  
Emission Line Galaxies

Abstract We analyse the large-scale clustering in Fourier space of emission line galaxies (ELG) from the Data Release 16 of the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey. The ELG sample contains 173,736 galaxies covering 1,170 square degrees in the redshift range 0.6 < z < 1.1. We perform a BAO measurement from the post-reconstruction power spectrum monopole, and study redshift space distortions (RSD) in the first three even multipoles. Photometric variations yield fluctuations of both the angular and radial survey selection functions. Those are directly inferred from data, imposing integral constraints which we model consistently. The full data set has only a weak preference for a BAO feature (1.4σ). At the effective redshift zeff = 0.845 we measure $D_{\rm V}(z_{\rm eff})/r_{\rm drag} = 18.33_{-0.62}^{+0.57}$, with DV the volume-averaged distance and rdrag the comoving sound horizon at the drag epoch. In combination with the RSD measurement, at zeff = 0.85 we find $f\sigma _8(z_{\rm eff}) = 0.289_{-0.096}^{+0.085}$, with f the growth rate of structure and σ8 the normalisation of the linear power spectrum, $D_{\rm H}(z_{\rm eff})/r_{\rm drag} = 20.0_{-2.2}^{+2.4}$ and DM(zeff)/rdrag = 19.17 ± 0.99 with DH and DM the Hubble and comoving angular distances, respectively. These results are in agreement with those obtained in configuration space, thus allowing a consensus measurement of fσ8(zeff) = 0.315 ± 0.095, $D_{\rm H}(z_{\rm eff})/r_{\rm drag} = 19.6_{-2.1}^{+2.2}$ and DM(zeff)/rdrag = 19.5 ± 1.0. This measurement is consistent with a flat ΛCDM model with Planck parameters.

scholarly journals Coherent Structures in the Boundary and Cloud Layers: Role of Updrafts, Subsiding Shells, and Environmental Subsidence

2016 ◽  
Vol 73 (4) ◽  
pp. 1789-1814 ◽  
Author(s):  
Seung-Bu Park ◽  
Pierre Gentine ◽  
Kai Schneider ◽  
Marie Farge
Keyword(s):  
Boundary Layer ◽  
Gravity Waves ◽  
Coherent Structures ◽  
Large Scale ◽  
Inversion Layer ◽  
Cloud Layer ◽  
Small Scale ◽  
Shallow Convection ◽  
Systematic Analysis ◽  
Heat And Moisture

Abstract Coherent structures, such as updrafts, downdrafts/shells, and environmental subsidence in the boundary and cloud layers of shallow convection, are investigated using a new classification method. Using large-eddy simulation data, the new method first filters out background turbulence and small-scale gravity waves from the coherent part of the flow, composed of turbulent coherent structures and large-scale transporting gravity waves. Then the algorithm divides this coherent flow into “updrafts,” “downdrafts/shells,” “subsidence,” “ascendance,” and four other flow structures using an octant analysis. The novel method can systematically track structures from the cloud-free boundary layer to the cloud layer, thus allowing systematic analysis of the fate of updrafts and downdrafts. The frequency and contribution of the coherent structures to the vertical mass flux and transport of heat and moisture can then be investigated for the first time. Updrafts, subsidence, and downdrafts/subsiding shells—to a lesser extent—are shown to be the most frequent and dominant contributors to the vertical transport of heat and moisture in the boundary layer. Contrary to previous perspective, environmental subsidence transport is shown to be weak in the cloud layer. Instead, downdrafts/shells are the main downward transport contributors, especially in the trade inversion layer. The newly developed method in this study can be used to better evaluate the entrainment and detrainment of individual—or an ensemble of—coherent structures from the unsaturated boundary layer to the cloud layer.

scholarly journals Do model emission line galaxies live in filaments at z ∼ 1?

2020 ◽  
Vol 498 (2) ◽  
pp. 1852-1870 ◽  
Author(s):  
V Gonzalez-Perez ◽  
W Cui ◽  
S Contreras ◽  
C M Baugh ◽  
J Comparat ◽  
...  
Keyword(s):  
Emission Line ◽  
Large Scale ◽  
Formation Rate ◽  
Stellar Mass ◽  
Fixed Number ◽  
Velocity Shear ◽  
Mass Star ◽  
Number Density ◽  
Star Forming ◽  
Emission Line Galaxies

ABSTRACT Current and future cosmological surveys are targeting star-forming galaxies at z ∼ 1 with nebular emission lines. We use a state-of-the-art semi-analytical model of galaxy formation and evolution to explore the large-scale environment of star-forming emission line galaxies (ELGs). Model ELGs are selected such that they can be compared directly with the DEEP2, VVDS, eBOSS-SGC, and DESI surveys. The large-scale environment of the ELGs is classified using velocity–shear–tensor and tidal–tensor algorithms. Half of the model ELGs live in filaments and about a third in sheets. Model ELGs that reside in knots have the largest satellite fractions. We find that the shape of the mean halo occupation distribution of model ELGs varies widely for different large-scale environments. To interpret our results, we also study fixed number density samples of ELGs and galaxies selected using simpler criteria, with single cuts in stellar mass, star formation rate, and [O ii] luminosity. The fixed number density ELG selection produces samples that are close to L[O ii] and SFR-selected samples for densities above 10−4.2 h3 Mpc−3. ELGs with an extra cut in stellar mass applied to fix their number density, present differences in sheets and knots with respect to the other samples. ELGs, SFR, and L[O ii] selected samples with equal number density have similar large-scale bias but their clustering below separations of 1h−1 Mpc is different.

scholarly journals High-resolution variations in size, number and arrangement of air bubbles in the EPICA DML (Antarctica) ice core

2013 ◽  
Vol 59 (217) ◽  
pp. 972-980 ◽  
Author(s):  
Verena Bendel ◽  
Kai J. Ueltzhöffer ◽  
Johannes Freitag ◽  
Sepp Kipfstuhl ◽  
Werner F. Kuhs ◽  
...  
Keyword(s):  
Bubble Size ◽  
Large Scale ◽  
Ice Core ◽  
Small Scale ◽  
Air Bubbles ◽  
Number Density ◽  
Glacial Ice ◽  
Size Number ◽  
Bubble Number ◽  
Bubble Number Density

AbstractWe investigated the large-scale (10–1000 m) and small-scale (mm–cm) variations in size, number and arrangement of air bubbles in the EPICA Dronning Maud Land (EDML) (Antarctica) ice core, down to the end of the bubble/hydrate transition (BHT) zone. On the large scale, the bubble number density shows a general correlation with the palaeo-temperature proxy, δ18O, and the dust concentration, which means that in Holocene ice there are fewer bubbles than in glacial ice. Small-scale variations in bubble number and size were identified and compared. Above the BHT zone there exists a strong anticorrelation between bubble number density and mean bubble size. In glacial ice, layers of high number density and small bubble size are linked with layers with high impurity content, identified as cloudy bands. Therefore, we regard impurities as a controlling factor for the formation and distribution of bubbles in glacial ice. The anticorrelation inverts in the middle of the BHT zone. In the lower part of the BHT zone, bubble-free layers exist that are also associated with cloudy bands. The high contrast in bubble number density in glacial ice, induced by the impurities, indicates a much more pronounced layering in glacial firn than in modern firn.

scholarly journals Dark energy survey year 1 results: Constraining baryonic physics in the Universe

2021 ◽  
Vol 502 (4) ◽  
pp. 6010-6031
Author(s):  
Hung-Jin Huang ◽  
Tim Eifler ◽  
Rachel Mandelbaum ◽  
Gary M Bernstein ◽  
Anqi Chen ◽  
...  
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Principal Component ◽  
External Information ◽  
Small Scale ◽  
Acoustic Oscillations ◽  
Dark Energy Survey ◽  
Theoretical Predictions ◽  
Hydrodynamical Simulations ◽  
Energy Survey

ABSTRACT Measurements of large-scale structure are interpreted using theoretical predictions for the matter distribution, including potential impacts of baryonic physics. We constrain the feedback strength of baryons jointly with cosmology using weak lensing and galaxy clustering observables (3 × 2pt) of Dark Energy Survey (DES) Year 1 data in combination with external information from baryon acoustic oscillations (BAO) and Planck cosmic microwave background polarization. Our baryon modelling is informed by a set of hydrodynamical simulations that span a variety of baryon scenarios; we span this space via a Principal Component (PC) analysis of the summary statistics extracted from these simulations. We show that at the level of DES Y1 constraining power, one PC is sufficient to describe the variation of baryonic effects in the observables, and the first PC amplitude (Q1) generally reflects the strength of baryon feedback. With the upper limit of Q1 prior being bound by the Illustris feedback scenarios, we reach $\sim 20{{\ \rm per\ cent}}$ improvement in the constraint of $S_8=\sigma _8(\Omega _{\rm m}/0.3)^{0.5}=0.788^{+0.018}_{-0.021}$ compared to the original DES 3 × 2pt analysis. This gain is driven by the inclusion of small-scale cosmic shear information down to 2.5 arcmin, which was excluded in previous DES analyses that did not model baryonic physics. We obtain $S_8=0.781^{+0.014}_{-0.015}$ for the combined DES Y1+Planck EE+BAO analysis with a non-informative Q1 prior. In terms of the baryon constraints, we measure $Q_1=1.14^{+2.20}_{-2.80}$ for DES Y1 only and $Q_1=1.42^{+1.63}_{-1.48}$ for DESY1+Planck EE+BAO, allowing us to exclude one of the most extreme AGN feedback hydrodynamical scenario at more than 2σ.

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