The redshift-distance relation. IV. The composite nature of N galaxies, their Hubble diagram, and the validity of measured redshifts as distance indicators.

1973 ◽  
Vol 180 ◽  
pp. 687 ◽  
Author(s):  
A. Sandage
Keyword(s):  
Hubble Diagram ◽  
Composite Nature ◽  
Distance Indicators ◽  
Distance Relation

scholarly journals MODIFICATIONS OF THE HUBBLE LAW IN SCALE-DEPENDENT COSMOLOGY

1996 ◽  
Vol 11 (31) ◽  
pp. 5519-5539 ◽  
Author(s):  
C.W. KIM ◽  
J. SONG ◽  
T.H. LEE
Keyword(s):  
Cosmological Model ◽  
Mass Density ◽  
Numerical Results ◽  
Luminosity Distance ◽  
Hubble Diagram ◽  
Inhomogeneous Universe ◽  
Open Universe ◽  
The Universe ◽  
Distance Relation ◽  
Increasing Function

We study some observational consequences of a recently proposed scale-dependent cosmological model for an inhomogeneous universe. In this model the universe is pictured as being inside a highly dense and rapidly expanding shell with the underdense center. For nearby objects (z≪1), the linear Hubble diagram is shown to remain valid even in this model, which has been demonstrated both analytically and numerically. For large z, we present some numerical results of the redshift luminosity distance relation and the behavior of the mass density as a function of the redshift. It is shown that the Hubble diagram in this model for a locally open universe (Ω(t0, r~0)=0.1) resembles that of the flat Friedmann cosmology. This implies that the study of the Hubble diagram cannot uniquely determine the value of q0 or Ω0. The model also accounts for the fact that Ω0 is an increasing function of the redshift.

Magellanic Cloud Eclipsing Binaries: Primary Distance Indicators

1999 ◽  
Vol 190 ◽  
pp. 563-566
Author(s):  
J. D. Pritchard ◽  
W. Tobin ◽  
J. V. Clausen ◽  
E. F. Guinan ◽  
E. L. Fitzpatrick ◽  
...  
Keyword(s):  
New Zealand ◽  
Magellanic Cloud ◽  
Eclipsing Binaries ◽  
Fundamental Parameters ◽  
Distance Indicators

Our collaboration involves groups in Denmark, the U.S.A. Spain and of course New Zealand. Combining ground-based and satellite (IUEandHST) observations we aim to determine accurate and precise stellar fundamental parameters for the components of Magellanic Cloud Eclipsing Binaries as well as the distances to these systems and hence the parent galaxies themselves. This poster presents our latest progress.

scholarly journals What Solar–Terrestrial Link Researchers Should Know about Interplanetary Drivers

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 138
Author(s):  
Yuri I. Yermolaev ◽  
Irina G. Lodkina ◽  
Lidia A. Dremukhina ◽  
Michael Y. Yermolaev ◽  
Alexander A. Khokhlachev
Keyword(s):  
Interplanetary Shock ◽  
Magnetic Storms ◽  
System Response ◽  
Ionospheric Disturbances ◽  
Atmosphere System ◽  
Compression Region ◽  
Different Types ◽  
Methodological Approaches ◽  
Composite Nature ◽  
Incorrect Data

One of the most promising methods of research in solar–terrestrial physics is the comparison of the responses of the magnetosphere–ionosphere–atmosphere system to various types of interplanetary disturbances (so-called “interplanetary drivers”). Numerous studies have shown that different types of drivers result in different reactions of the system for identical variations in the interplanetary magnetic field. In particular, the sheaths—compression regions before fast interplanetary CMEs (ICMEs)—have higher efficiency in terms of the generation of magnetic storms than ICMEs. The growing popularity of this method of research is accompanied by the growth of incorrect methodological approaches in such studies. These errors can be divided into four main classes: (i) using incorrect data with the identification of driver types published in other studies; (ii) using incorrect methods to identify the types of drivers and, as a result, misclassify the causes of magnetospheric-ionospheric disturbances; (iii) ignoring a frequent case with a complex, composite, nature of the driver (the presence of a sequence of several simple drivers) and matching the system response with only one of the drivers; for example, a magnetic storm is often generated by a sheath in front of ICME, although the authors consider these events to be a so-called “CME-induced” storm, rather than a “sheath-induced” storm; (iv) ignoring the compression regions before the fast CME in the case when there is no interplanetary shock (IS) in front of the compression region (“sheath without IS” or the so-called “lost driver”), although this type of driver generates about 10% of moderate and large magnetic storms. Possible ways of solving this problem are discussed.

scholarly journals A Dynamic Factor and Neural Networks Analysis of the Co-movement of Public Revenues in the EMU

2021 ◽  
Author(s):  
Cosimo Magazzino ◽  
Marco Mele
Keyword(s):  
Neural Networks ◽  
Factor Model ◽  
Common Factor ◽  
Back Propagation ◽  
Dynamic Factor ◽  
Common Component ◽  
Economic Cycles ◽  
Composite Nature ◽  
Empirical Demonstration ◽  
Public Revenues

AbstractThis paper shows that the co-movement of public revenues in the European Monetary Union (EMU) is driven by an unobserved common factor. Our empirical analysis uses yearly data covering the period 1970–2014 for 12 selected EMU member countries. We have found that this common component has a significant impact on public revenues in the majority of the countries. We highlight this common pattern in a dynamic factor model (DFM). Since this factor is unobservable, it is difficult to agree on what it represents. We argue that the latent factor that emerges from the two different empirical approaches used might have a composite nature, being the result of both the more general convergence of the economic cycles of the countries in the area and the increasingly better tuned tax structure. However, the original aspect of our paper is the use of a back-propagation neural networks (BPNN)-DF model to test the results of the time-series. At the level of computer programming, the results obtained represent the first empirical demonstration of the latent factor’s presence.

scholarly journals The effects of peculiar velocities in SN Ia environments on the local H0 measurement

2020 ◽  
Vol 500 (3) ◽  
pp. 3728-3742
Author(s):  
Thomas M Sedgwick ◽  
Chris A Collins ◽  
Ivan K Baldry ◽  
Philip A James
Keyword(s):  
Hubble Constant ◽  
Density Parameter ◽  
Host Galaxies ◽  
Peculiar Velocities ◽  
Standard Candle ◽  
Modern Cosmology ◽  
Type Ia ◽  
The Difference ◽  
Ia Supernovae ◽  
Distance Indicators

ABSTRACT The discrepancy between estimates of the Hubble constant (H0) measured from local (z ≲  0.1) scales and from scales of the sound horizon is a crucial problem in modern cosmology. Peculiar velocities (vpec) of standard candle distance indicators can systematically affect local H0 measurements. We here use 2MRS galaxies to measure the local galaxy density field, finding a notable z  <  0.05 underdensity in the SGC-6dFGS region of 27  ±  2 per cent. However, no strong evidence for a ‘Local Void’ pertaining to the full 2MRS sky coverage is found. Galaxy densities are used to measure a density parameter, Δϕ+−, which we introduce as a proxy for vpec that quantifies density gradients along a supernova (SN) line of sight. Δϕ+− is found to correlate with local H0 estimates from 88 Pantheon Type Ia supernovae (SNe Ia; 0.02  <  z  <  0.05). Density structures on scales of ∼50 Mpc are found to correlate strongest with H0 estimates in both the observational data and in mock data from the MDPL2-Galacticus simulation. Using trends of H0 with Δϕ+−, we can correct for the effects of density structure on local H0 estimates, even in the presence of biased vpec. However, the difference in the inferred H0 estimate with and without the peculiar velocity correction is limited to < 0.1  per cent. We conclude that accounting for environmentally induced peculiar velocities of SN Ia host galaxies does not resolve the tension between local and CMB-derived H0 estimates.

scholarly journals An updated Type II supernova Hubble diagram

2018 ◽  
Vol 611 ◽  
pp. A25 ◽  
Author(s):  
E. E. E. Gall ◽  
R. Kotak ◽  
B. Leibundgut ◽  
S. Taubenberger ◽  
W. Hillebrandt ◽  
...  
Keyword(s):  
Spectral Lines ◽  
Balmer Line ◽  
Type Ii ◽  
Dependent Relation ◽  
Measuring Techniques ◽  
Distance Indicators ◽  
Larger Sample ◽  
Current Record ◽  
Initial Results ◽  
The Continuum

We present photometry and spectroscopy of nine Type II-P/L supernovae (SNe) with redshifts in the 0.045 ≲ z ≲ 0.335 range, with a view to re-examining their utility as distance indicators. Specifically, we apply the expanding photosphere method (EPM) and the standardized candle method (SCM) to each target, and find that both methods yield distances that are in reasonable agreement with each other. The current record-holder for the highest-redshift spectroscopically confirmed supernova (SN) II-P is PS1-13bni (z = 0.335−0.012+0.009), and illustrates the promise of Type II SNe as cosmological tools. We updated existing EPM and SCM Hubble diagrams by adding our sample to those previously published. Within the context of Type II SN distance measuring techniques, we investigated two related questions. First, we explored the possibility of utilising spectral lines other than the traditionally used Fe iiλ5169 to infer the photospheric velocity of SN ejecta. Using local well-observed objects, we derive an epoch-dependent relation between the strong Balmer line and Fe iiλ5169 velocities that is applicable 30 to 40 days post-explosion. Motivated in part by the continuum of key observables such as rise time and decline rates exhibited from II-P to II-L SNe, we assessed the possibility of using Hubble-flow Type II-L SNe as distance indicators. These yield similar distances as the Type II-P SNe. Although these initial results are encouraging, a significantly larger sample of SNe II-L would be required to draw definitive conclusions.

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