Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLarge-scale Cosmic Flows from Cosmicflows-2 Catalog
138
0
0.0
(
0
)
Authors
Richard Watkins
Ask ChatGPT about the research
No Arabic abstract
The Cosmicflows-2 catalogue is a compendium of peculiar velocity measurements. While it has many objects in common with the COMPOSITE catalogue, a previously analysed collection of peculiar velocity data found to give an unexpectedly large bulk flow on large scales, the data in Cosmicflows-2 have been reanalysed to ensure consistency between distances measured using different methods. In particular, a focus on accurate distances led the authors of the Cosmicflows-2 to not correct for homogeneous or inhomogeneous Malmquist bias, both or which are corrected for in the COMPOSITE compilation. We find remarkable agreement between the COMPOSITE and the Cosmicflows-2 if the small EFAR sample of clusters located in two dense superclusters is removed from both surveys, giving results that are inconsistent with the $Lambda$ cold dark matter standard model with Planck central parameters at the 98% level. On smaller scales we find overall agreement between data sets and consistency with the standard model.
rate research
Read More
In this study, we present an update of a compilation of line width measurements of neutral atomic hydrogen (HI) galaxy spectra at 21 cm wavelength. Our All Digital HI (ADHI) catalog consists of the previous release augmented with our new HI observations and an analysis of archival data. This study provides the required HI information to measure the distances of spiral galaxies through the application of the Tully-Fisher (TF) relation. We conducted observations at the Green Bank telescope (GBT) and reprocessed spectra obtained at the Nancay radiotelescope by the Nancay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) and Kinematics of the Local Universe (KLUN) collaborations and we analyzed the recently published full completion Arecibo Legacy Fast ALFA (ALFALFA) 100% survey in order to identify galaxies with good quality HI line width measurements. This paper adds new HI data adequate for TF use for 385 galaxies observed at GBT, 889 galaxies from archival Nancay spectra, and 1,515 rescaled Arecibo ALFALFA spectra. In total, this release adds 1,274 new good quality measurements to the ADHI catalog. Today, the ADHI database contains 18,874 galaxies, for which 15,433 have good quality data for TF use. The final goal is to compute accurate distances to spiral galaxies, which will be included in the next generation of peculiar velocities catalog: Cosmicflows-4.
The peculiar velocity of a mass tracer is on average aligned with the dipole modulation of the surrounding mass density field. We present a first measurement of the correlation between radial peculiar velocities of objects in the cosmicflows-3 catalog and the dipole moment of the 2MRS galaxy distribution in concentric spherical shells centered on these objects. Limiting the analysis to cosmicflows-3 objects with distances of $100 rm Mpc h^{-1}$, the correlation function is detected at a confidence level $> 4sigma$. The measurement is found consistent with the standard $Lambda$CDM model at $< 1.7sigma$ level. We formally derive the constraints $0.32<Omega^{0.55}sigma_8<0.48$ ($68% $ confidence level) or equivalently $0.34<Omega^{0.55}/b<0.52$, where $b$ is the galaxy bias factor. Deeper and improved peculiar velocity catalogs will substantially reduce the uncertainties, allowing tighter constraints from this type of correlations.
Reconstruction of the local velocity field from the overdensity field and a gravitational acceleration that falls off from a point mass as r^-2 yields velocities in broad agreement with peculiar velocities measured with galaxy distance indicators. MONDian gravity does not. To quantify this, we introduce the velocity angular correlation function as a diagnostic of peculiar velocity field alignment and coherence as a function of scale. It is independent of the bias parameter of structure formation in the standard model of cosmology and the acceleration parameter of MOND. A modified gravity acceleration consistent with observed large scale structure would need to asymptote to zero at large distances more like r^-2, than r^-1.
The cosmic infrared background (CIB) is a powerful probe of large-scale structure across a very large redshift range, and consists of unresolved redshifted infrared emission from dusty galaxies. It can be used to study the astrophysics of galaxies, the star formation history of the universe, and the connection between dark and luminous matter. It can furthermore be used as a tracer of the large-scale structure and thus assist in de-lensing of the cosmic microwave background. The major difficulty in its use lies in obtaining accurate and unbiased large-scale CIB images that are cleaned of the contamination by Galactic dust. We used data on neutral atomic hydrogen from the recently-released HI4PI Survey to create template maps of Galactic dust, allowing us to remove this component from the Planck intensity maps from 353 to 857 GHz for approximately $25%$ of the sky. This allows us to constrain the CIB power spectrum down to $ellgtrsim 70$. We present these CIB maps and the various processing and validation steps that we have performed to ensure their quality, as well as a comparison with previous studies. All our data products are made publicly available at https://doi.org/10.7910/DVN/8A1SR3, thereby enabling the community to investigate a wide range of questions related to the universes large-scale structure.
This is a report on the status and prospects of the quantification of neutrino properties through the cosmological neutrino background for the Cosmic Frontier of the Division of Particles and Fields Community Summer Study long-term planning exercise.
Experiments planned and underway are prepared to study the cosmological neutrino background in detail via its influence on distance-redshift relations and the growth of structure. The program for the next decade described in this document, including upcoming spectroscopic galaxy surveys eBOSS and DESI and a new Stage-IV CMB polarization experiment CMB-S4, will achieve sigma(sum m_nu) = 16 meV and sigma(N_eff) = 0.020. Such a mass measurement will produce a high significance detection of non-zero sum m_nu, whose lower bound derived from atmospheric and solar neutrino oscillation data is about 58 meV. If neutrinos have a minimal normal mass hierarchy, this measurement will definitively rule out the inverted neutrino mass hierarchy, shedding light on one of the most puzzling aspects of the Standard Model of particle physics --- the origin of mass. This precise a measurement of N_eff will allow for high sensitivity to any light and dark degrees of freedom produced in the big bang and a precision test of the standard cosmological model prediction that N_eff = 3.046.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
