scholarly journals Mapping the Cosmic Web with the largest all-sky surveys

2014 ◽  
Vol 11 (S308) ◽  
pp. 143-148
Author(s):  
Maciej Bilicki ◽  
John A. Peacock ◽  
Thomas H. Jarrett ◽  
Michelle E. Cluver ◽  
Louise Steward
Keyword(s):  
Three Dimensional ◽  
Optical Data ◽  
Microwave Background ◽  
Sky Surveys ◽  
Photometric Redshift ◽  
Redshift Surveys ◽  
Cross Correlations ◽  
Galaxy Redshift ◽  
Celestial Sphere ◽  
The Universe

AbstractOur view of the low-redshift Cosmic Web has been revolutionized by galaxy redshift surveys such as 6dFGS, SDSS and 2MRS. However, the trade-off between depth and angular coverage limits a systematic three-dimensional account of the entire sky beyond the Local Volume (z< 0.05). In order to reliably map the Universe to cosmologically significant depths over the full celestial sphere, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. We have undertaken a dedicated program of cross-matching the largest photometric all-sky surveys – 2MASS, WISE and SuperCOSMOS – to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts – the 2MASS Photometric Redshift catalog (2MPZ, Bilickiet al. 2014a) – has been publicly released and includes almost 1 million galaxies with a mean redshift ofz=0.08. Here we summarize how this catalog was constructed and how using the WISE mid-infrared sample together with SuperCOSMOS optical data allows us to push to redshift shells ofz∼ 0.2 –0.3 on unprecedented angular scales. Our catalogs, with ∼ 20 million sources in total, provide access to cosmological volumes crucial for studies of local galaxy flows (clustering dipole, bulk flow) and cross-correlations with the cosmic microwave background such as the integrated Sachs-Wolfe effect or lensing studies.

COSMOLOGY FROM GALAXY SURVEYS

2011 ◽  
Vol 20 (10) ◽  
pp. 2115-2119
Author(s):  
WILL J. PERCIVAL
Keyword(s):  
Power Spectrum ◽  
Three Dimensional ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Peculiar Galaxy ◽  
Galaxy Surveys ◽  
Redshift Surveys ◽  
Galaxy Redshift ◽  
The Universe ◽  
Statistical Clustering

Galaxy Redshift surveys provide a three-dimensional map of the Universe. Three distinct processes that encode cosmological information in these maps, are commonly used to constrain models: (i) the comoving power spectrum shape depends on the physical properties of the early Universe, including the physical matter, baryon and neutrino densities, the inflation power spectrum and the degree of Gaussianity of density fluctuations; (ii) we can use the statistical clustering of galaxies as a standard ruler by matching it, or parts of it at different redshifts, and to the Cosmic Microwave Background (CMB); (iii) redshift-space distortions, anisotropic patterns caused by peculiar galaxy velocities, reveal structure growth. Following the design of my talk at the 1st Galileo–Xu Guangqi Meeting, I will use these proceedings to briefly review these experiments.

The experience of employment of the mathematical cartography methods in cosmology

2017 ◽  
Vol 923 (5) ◽  
pp. 7-16
Author(s):  
A.V. Kavrayskiy
Keyword(s):  
Background Radiation ◽  
Three Dimensional ◽  
Spherical Coordinates ◽  
Linear Element ◽  
Microwave Background ◽  
Euclidian Space ◽  
Microwave Background Radiation ◽  
Rectangular Coordinates ◽  
The Universe ◽  
Length Distortion

The experience of mathematical modeling of the 3D-sphere in the 4D-space and projecting it by mathematical cartography methods in the 3D-Euclidian space is presented. The problem is solved by introduction of spherical coordinates for the 3D-sphere and their transformation into the rectangular coordinates, using the mathematical cartography methods. The mathematical relationship for calculating the length distortion mp(s) of the ds linear element when projecting the 3D-sphere from the 4-dimensional Euclidian space into three-dimensional Euclidian space is derived. Numerical examples, containing the modeling of the ds small linear element by spherical coordinates of 3D-sphere, projecting this sphere into the 3D-Euclidian space and length of ds calculating by means of its projection dL and size of distortion mp(s) are solved. Based on the model of the Universe known in cosmology as the 3D-sphere, the hypothesis of connection between distortion mp(s) and the known observed effects Redshift and Microwave Background Radiation is considered.

scholarly journals Large-Scale Anisotropy of the Cosmic Relic Radiation in Spatially Open Cosmological Models

1983 ◽  
Vol 104 ◽  
pp. 149-152
Author(s):  
V. N. Lukash
Keyword(s):  
Large Scale ◽  
Background Radiation ◽  
Microwave Background ◽  
Spatial Homogeneity ◽  
Sensitive Tool ◽  
Microwave Background Radiation ◽  
Universal Expansion ◽  
Celestial Sphere ◽  
The Universe ◽  
Small Anisotropy

The observed microwave background radiation is a sensitive tool for studying the fundamental features of the universe. A puzzling constancy on the celestial sphere of the temperature, T, of the equilibrium relic radiation coming to us from causally nonrelated regions of space-time points to the global spatial homogeneity and isotropy of the cosmological expansion. On the other hand, a small anisotropy of the relic background can tell a lot about the physics of the beginning of the universal expansion, where primordial cosmological perturbations, which later affect the relic isotropy, formed (see, e.g., [1,2] and other reviews on the early universe). We would like to emphasize another factor that forms mainly the large-scale structure of relic anisotropy: the spatial curvature of the background Friedmann Universe. In the light of the discovery of the large-scale anisotropy of the cosmic radiation [3–5], this problem becomes very important.

scholarly journals Measuring the Universe with Galaxy Redshift Surveys

2018 ◽  
pp. 1-16
Author(s):  
L. Guzzo ◽  
J. Bel ◽  
D. Bianchi ◽  
C. Carbone ◽  
B. R. Granett ◽  
...  
Keyword(s):  
Redshift Surveys ◽  
Galaxy Redshift ◽  
The Universe

scholarly journals Mapping the Dark Energy Equation of State

2005 ◽  
Vol 216 ◽  
pp. 59-66
Author(s):  
Eric V. Linder
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Cosmic Microwave Background ◽  
Structure Formation ◽  
Energy Equation ◽  
Microwave Background ◽  
Redshift Surveys ◽  
Expansion Of The Universe ◽  
The Universe

The acceleration of the expansion of the universe has deep implications for structure formation, the composition of the universe, and its fate. Roughly 70% of the energy density is in a dark energy, whose nature remains unknown. Mapping the expansion history through supernovae, mapping the geometry of the universe and formation of structure through redshift surveys, and mapping the distance to recombination through the cosmic microwave background provide complementary, precise probes of the equation of state of the dark energy. Together these next generation maps of the cosmos can reveal not only the value today, but the redshift variation, of the equation of state, providing a critical clue to the underlying physics.

scholarly journals Darth Fader: Analysing galaxy spectra at low signal-to-noise

2014 ◽  
Vol 10 (S306) ◽  
pp. 72-74
Author(s):  
Adrienne Leonard ◽  
Daniel P. Machado ◽  
Filipe B. Abdalla ◽  
Jean-Luc Starck
Keyword(s):  
Spectral Lines ◽  
Signal To Noise ◽  
Automated Method ◽  
Redshift Surveys ◽  
Formation History ◽  
The Galaxy ◽  
History Of ◽  
Galaxy Redshift ◽  
The Universe

AbstractSpectroscopic redshift surveys are an incredibly valuable tool in cosmology, allowing us to trace the distribution of galaxies as a function of distance and, thus, trace the evolution of structure formation in the Universe. However, estimating the redshifts from spectra with low signal-to-noise is difficult, and such data are often either discarded or require human classification of spectral lines to obtain the galaxy redshift. Darth Fader offers an automated method for estimating the redshifts of galaxies in the low signal-to-noise regime. Using a sophisticated, wavelet-based technique, galaxy spectra can be separated into continuum, line and noise components, and the lines can then be cross-correlated with template spectra in order to estimate the redshifts. Cross-matching of the identified lines then allows for a cleaning of the resulting catalogue, effectively removing the vast majority of erroneous redshift estimates and resulting in a highly pure, highly accurate redshift catalogue. Darth Fader allows us to effectively use low signal-to-noise galaxy spectra, and dramatically reduces the number of human hours required to do this, allowing spectroscopic surveys to probe deeper into the formation history of the Universe.

scholarly journals Interactive Visualization of 3D Redshift Surveys with SDvision

2010 ◽  
Vol 6 (S277) ◽  
pp. 154-157
Author(s):  
Daniel Pomarède ◽  
Marguerite Pierre
Keyword(s):  
Software Package ◽  
Three Dimensional ◽  
Interactive Visualization ◽  
Data Reconstruction ◽  
Clusters Of Galaxies ◽  
Ray Casting ◽  
Photometric Redshifts ◽  
Photometric Redshift ◽  
Density Peaks ◽  
Redshift Surveys

AbstractThe three-dimensional visualization of redshift surveys is a key player in the comprehension of the structuration of the cosmic web. The SDvision software package, intended primarily for the visualization of massive cosmological simulations, has been extended to provide an interactive visual representation of different classes of redshift surveys, with the objective to enable direct comparisons between the rare highest-density peaks traced by the clusters of galaxies found in the XMM-LSS Survey and the densely populated catalogues of galaxy photometric redshifts. We present the various possibilities offered by this tool in terms of filtering of the data, reconstruction of density fields, interactivity and visual rendering, including various techniques such as ray-casting, isosurfaces, slicing and texturing. This is illustrated using the C1 and C2 samples of the XMM-LSS Survey, and the publicly released COSMOS and CFHTLS photometric redshift Catalogs. Comparisons with published results are presented and discussed.

scholarly journals Evidence for cosmic acceleration with next-generation surveys: a model-independent approach

2020 ◽  
Vol 499 (1) ◽  
pp. L6-L10 ◽  
Author(s):  
Carlos A P Bengaly
Keyword(s):  
Dark Energy Model ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Redshift Surveys ◽  
Model Independent ◽  
Galaxy Redshift ◽  
Hubble Parameters ◽  
The Universe ◽  
Lower Redshift ◽  
A Current

ABSTRACT We quantify the evidence for cosmic acceleration using simulations of H(z) measurements from SKA- and Euclid-like surveys. We perform a non-parametric reconstruction of the Hubble parameters and its derivative to obtain the deceleration parameter q(z) using the Gaussian Processes method. This is a completely model-independent approach, so we can determine whether the Universe is undergoing accelerated expansion regardless of any assumption of a dark energy model. We find that Euclid-like and SKA-like band 1 surveys can probe cosmic acceleration at over 3 and 5σ confidence level, respectively. By combining them with an SKA-like band 2 survey, which reaches lower redshift ranges, the evidence for a current accelerated phase increases to over 7σ. This is a significant improvement from current H(z) measurements from cosmic chronometers and galaxy redshift surveys, showing that these surveys can underpin cosmic acceleration in a model-independent way.

scholarly journals Large-Scale Flows in the Local Universe

1996 ◽  
Vol 168 ◽  
pp. 175-182 ◽  
Author(s):  
D.S. Mathewson ◽  
V.L. Ford
Keyword(s):  
Large Scale ◽  
Velocity Measurements ◽  
Local Universe ◽  
Peculiar Velocities ◽  
Redshift Surveys ◽  
Density Maps ◽  
The Universe ◽  
Great Wall ◽  
Great Attractor ◽  
Streaming Flow

Peculiar velocity measurements of 2500 southern spiral galaxies show large-scale flows in the direction of the Hydra-Centaurus clusters which fully participate in the flow themselves. The flow is not uniform over this region and seems to be associated with the denser regions which participate in the flow of amplitude about 400km/s. In the less dense regions the flow is small or non-existent. This makes the flow quite asymmetric and inconsistent with that expected from large-scale, parallel streaming flow that includes all galaxies out to 6000km/s as previously thought. The flow cannot be modelled by a Great Attractor at 4300km/s or the Centaurus clusters at 3500km/s. Indeed, from the density maps derived from the redshift surveys of “optical” and IRAS galaxies, it is difficult to see how the mass concentrations can be responsible particularly as they themselves participate in the flow. These results bring into question the generally accepted reason for the peculiar velocities of galaxies that they arise solely as a consequence of infall into the dense regions of the universe. To the N. of the Great Attractor region, the flow increases and shows no sign of diminishing out to the redshift limit of 8000km/s in this direction. We may have detected flow in the nearest section of the Great Wall.

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