Observing SNe Ia at z > 1 with the HST and at z ≃ 0.2 with the SDSS-II

2006 ◽  
Vol 2 (14) ◽  
pp. 314-315
Author(s):  
Hubert Lampeitl ◽  
Adam G. Riess
Keyword(s):  
Hubble Space Telescope ◽  
High Redshift ◽  
Sloan Digital Sky Survey ◽  
Accelerated Expansion ◽  
Hubble Diagram ◽  
Sky Survey ◽  
Direct Measurements ◽  
Expansion Of The Universe ◽  
Intermediate Redshifts ◽  
The Universe

AbstractSNe Ia are currently providing the most direct measurements of the accelerated expansion of the Universe and also put constraints on the nature and evolution of the so-called ‘dark energy’. Despite major efforts to increase the number of known high-redshift SNe Ia with reliable distance estimates, two regions in the Hubble diagram remain only sparsely observed. At redshifts z > 1 the limitations of ground-based instruments require the Hubble Space Telescope and its superior angular resolution to get meaningful distance estimates, while at intermediate redshifts (z ≃ 0.2) the large solid angle necessary presents an obstacle to most surveys that can be overcome with the Sloan Digital Sky Survey, SDSS-II.

scholarly journals Construcción de un diagrama de Hubble: Una herramienta para la Enseñanza de la Astronomía - Building a Hubble Diagram: A Tool for Teaching Astronomy

2016 ◽  
Vol 1 (24) ◽  
pp. 17
Author(s):  
Giovanni Cardona-Rodriguez ◽  
Jaime Duván Reyes- Roncancio ◽  
Mauricio Giraldo
Keyword(s):  
Hubble Parameter ◽  
Sloan Digital Sky Survey ◽  
Educational Activity ◽  
Hubble Diagram ◽  
Evolution Of The Universe ◽  
Sky Survey ◽  
Expansion Of The Universe ◽  
Para Determinar ◽  
Hubble’S Law ◽  
The Universe

Se presenta una actividad que puede apoyar el trabajo de los docentes que dirigen  clubes de Astronomía y quieren abordar el tema de evolución del Universo, ya que   se  reconstruye  la ley de Hubble  a partir de la construcción de un Diagrama de Hubble con  datos  tomados del Sloan Digital Sky Survey   (SDSS) ,  del  cual se obtiene el valor del parámetro de Hubble y se infiere la expansión del Universo. Esta actividad  didáctica permite a los profesores orientar a sus estudiantes por el camino que siguió Hubble  para determinar su ley, en este sentido se exponen algunas implicaciones de aplicación de la misma en el contexto de la formación de profesores de física y de los clubes de Astronomía. Construction of a Hubble Diagram: A tool for teaching astronomyThis article presents the construction and analysis of an activity that can support the work of teachers who run Astronomy clubs and want to address the issue of evolution of the Universe. Here Hubble's law is reconstructed by reproducing a Hubble diagram with Sloan Digital Sky Survey's (SDSS) data, from which the Hubble parameter value is obtained and the expansion of the Universe is inferred. This educational activity allows teachers to guide their students along the path followed by Hubble to determine his law. In this sense some implications of applying the latter are discussed in the context of teacher's training in Physics and Astronomy clubs.Construção de um diagrama de Hubble: Uma ferramenta para ensino de astronomíaSe apresenta uma actividade que pode apoiar o trabalho dos professores que dirigem clubes de Astronomia e querem abordar a questão da evolução do Universo, como a lei de Hubble é reconstruída a partir da reprodução de um diagrama de Hubble com os dados tomados do Sloan digital Sky Survey (SDSS), é achado o parâmetro de Hubble e inferida a expansão do universo. Esta actividade educativa permite aos professores orientar seus alunos ao longo do caminho seguido Hubble para determinar a lei. Neste sentido algumas implicações da aplicação da mesma no contexto da formação de professores de física e clubes astronomia. 

scholarly journals Studying Luminous Red Galaxies to probe H(z) at high redshift

2012 ◽  
Vol 8 (S295) ◽  
pp. 185-185
Author(s):  
A. Ratsimbazafy ◽  
C. Cress ◽  
S. Crawford ◽  
Keyword(s):  
High Redshift ◽  
Sloan Digital Sky Survey ◽  
Age Dating ◽  
Time Interval ◽  
Spectral Fitting ◽  
Luminous Red Galaxies ◽  
Sky Survey ◽  
Intense Burst ◽  
Red Galaxies ◽  
The Universe

AbstractLuminous Red Galaxies (LRGs) have old, red stellar populations often interpreted as evidence of a formation scenario in which these galaxies form in a single intense burst of star formation at high redshift. By measuring the average age of LRGs at two different redshifts, one can potentially measure the redshift interval corresponding to a time interval and thus measure the Hubble parameter H(z) ≈ −(1 + z)−1 Δ z/Δt (as in Jimenez & Loeb). The goal of this project is to measure directly the expansion rate of the universe at the redshift range 0.1 < z < 1.0 within 3% precision. We explore the age-dating of Sloan Digital Sky Survey LRGs using the stellar population models of Lick absorption line indices after stacking spectra in redshift bins to increase the signal-to-noise. We also use the method of full spectral fitting to measure the ages of LRGs observed with the Southern Africa Large Telescope (SALT).

Cosmological constant

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Vacuum Fluctuations ◽  
Present Epoch ◽  
Modify Gravity ◽  
Expansion Of The Universe ◽  
The Universe

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

The Quest for Relics: Massive compact galaxies in the local Universe

2019 ◽  
Vol 15 (S359) ◽  
pp. 441-443
Author(s):  
F. S. Lohmann ◽  
A. Schnorr-Müller ◽  
M. Trevisan ◽  
R. Riffel ◽  
N. Mallmann ◽  
...  
Keyword(s):  
High Redshift ◽  
Control Sample ◽  
Sloan Digital Sky Survey ◽  
Integral Field Spectroscopy ◽  
Sky Survey ◽  
Size Evolution ◽  
Compact Galaxies ◽  
Minor Mergers ◽  
Significant Size ◽  
Integral Field

AbstractObservations at high redshift reveal that a population of massive, quiescent galaxies (called red nuggets) already existed 10 Gyr ago. These objects undergo a significant size evolution over time, likely due to minor mergers. In this work we present an analysis of local massive compact galaxies to assess if their properties are consistent with what is expected for unevolved red nuggets (relic galaxies). Using integral field spectroscopy (IFS) data from the MaNGA survey from the Sloan Digital Sky Survey (SDSS), we characterized the kinematics and properties of stellar populations of massive compact galaxies, and find that these objects exhibit, on average, a higher rotational support than a control sample of average sized early-type galaxies. This is in agreement with a scenario in which these objects have a quiet accretion history, rendering them candidates for relic galaxies.

INFLATION, QUINTESSENCE PROBLEM AND VARYING SPEED OF LIGHT

2002 ◽  
Vol 17 (05) ◽  
pp. 295-302
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Speed Of Light ◽  
Expansion Of The Universe ◽  
The Universe

In this paper it is shown that the present accelerated expansion of the Universe can be explained only by considering variation of the speed of light, without taking into account the cosmological constant or quintessence matter.

Heuristic determination of the cosmological constant

2021 ◽  
pp. 2150114
Author(s):  
Manuel Urueña Palomo ◽  
Fernando Pérez Lara
Keyword(s):  
Field Theory ◽  
Energy Density ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Fundamental Constants ◽  
Quantum Field ◽  
Brute Force ◽  
Expansion Of The Universe ◽  
The Universe

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

scholarly journals Can accelerated expansion of the universe be due to spacetime vorticity?

2018 ◽  
Vol 33 (40) ◽  
pp. 1850240
Author(s):  
Babur M. Mirza
Keyword(s):  
Magnetic Field ◽  
Accelerated Expansion ◽  
Newtonian Gravity ◽  
Hubble’S Parameter ◽  
Cosmic Expansion ◽  
Zero Curvature ◽  
Expansion Of The Universe ◽  
General Relativistic ◽  
The Universe ◽  
The Magnetic Field

We present here a general relativistic mechanism for accelerated cosmic expansion and the Hubble’s parameter. It is shown that spacetime vorticity coupled to the magnetic field density in galaxies causes the galaxies to recede from one another at a rate equal to the Hubble’s constant. We therefore predict an oscillatory universe, with zero curvature, without assuming violation of Newtonian gravity at large distances or invoking dark energy/dark matter hypotheses. The value of the Hubble’s constant, along with the scale of expansion, as well as the high isotropy of CMB radiation are deduced from the model.

scholarly journals Time Blast Wave Theory for the Expansion of the Universe

2021 ◽  
Author(s):  
G K Jarvis
Keyword(s):  
Blast Wave ◽  
Space Dimension ◽  
High Redshift ◽  
Wave Theory ◽  
Time Dimension ◽  
Expansion Time ◽  
Expansion Of The Universe ◽  
Time Away ◽  
The Universe ◽  
Strong Agreement

Abstract A new theory is presented and tested that time itself is the phenomenon that causes the expansion of the universe and that without expansion, time would simply not be. The model of the theory accurately matches observed cosmological luminosity data consequently accurately describing the observed expansion of the universe. The theory implies that the universe exploded outwards within the dimension of time with all particles expanding from this event within a time blast sphere. Each space dimension is wrapped around the time dimension and every object that is gravitationally separate within the time blast-wave will progress on their own time trajectory of time away from time zero. This has the effect that all objects will expand or move apart as the time sphere expands. We observe distant, and therefore historic, objects on a spiral timeline. We have modelled the theory and shown strong agreement with luminosity observations both at low and high redshift without the need for a cosmological constant thus indicating that the universe is not accelerating in its expansion. The model in fact predicts it is decelerating. The theory also predicts that the unperturbed speed of time expansion will impose a limit on the universe in terms of the fastest speed possible and the speed that light must always travel at. With this limit and as no object can ever be stationary in the time dimension, but that faster and heavier objects will expand less, the theory consequently leads us to explain why special and general relativity occur. Gravity can be explained by the clumping of matter into the dimension of time causing a localised slowing of expansion subsequently causing time dilation and thus resulting in an attractive force with other objects. By this theory, black holes are not singularities but are simply dimples on the time blast wave front.

Sign in / Sign up

Export Citation Format

Share Document