24/7 Space News
Alternative models could clarify Universe's expansion debate
This new sample of quasars constitutes the "Gold sample". This figure shows the number of sources (N), the OM derived, and its probability (PDF). The Gold Quasars sample yields a precision on OM unprecedentedly reached with only quasars, even greater than the current SNe Ia precision. This analysis also shows a trend toward OM =0.1
Alternative models could clarify Universe's expansion debate
by Simon Mansfield
Sydney, Australia (SPX) Aug 22, 2023

The quest for the true value of the Hubble constant (H0) tension which gives a measure of the current expansion of the Universe is still on. The fervent debate today is about the discrepancy between the H0 values obtained from type Ia supernovae (SNe Ia) and from the Cosmic Microwave Background Radiation (CMB), a radiation emitted from the early Universe close to its origin.

Because of this debate, an international team led by Dr. Maria Dainotti, assistant professor at the National Astronomical Observatory of Japan (NAOJ) and affiliate research scientist at Space Science Institute, Boulder, CO, opened a new research field of investigation with a series of three papers by investigating if this tension could be alleviated when considering alternative cosmological models (namely when the Universe is not flat as currently assumed, but it is closed for example) with the aid of statistics and supercomputing facilities at NAOJ.

The team included a statistical expert, Prof. Malgorzata Bogdan from Lund University, and theoreticians from the National Autonomous University of Mexico (UNAM), Prof. Nissim Fraija, and University of Nevada Las Vegas, Prof. Bing Zhang. The team was assisted in running the simulations at the supercomputing facilities by Kazunari Iwasaki, Assistant Professor at NAOJ and member of the Center for Computational Astrophysics (CfCA) at NAOJ.

The fate of a flat Universe is that it will only expand at a rate just sufficient to avoid collapse, whereas a closed Universe will expand to a maximum size and after that will then collapse in upon itself. To tackle this issue, the team, in Bargiacchi, Dainotti et al. (2022), investigated different statistical tools from the ones commonly used in the framework of standard cosmological models.

They quantified the difference between the theoretical formulation, which includes the shape of the Universe (e.g., flat or closed Universe), of the distance from us to several cosmological objects, such as the SNe Ia, Quasars, Baryon Acoustic Oscillations, and Gamma-Ray Bursts (GRBs) compared with the observed distance obtained by using these objects as distance estimators independently from the shape of the Universe.

They pinpointed that this difference is not Gaussian (bell curve shaped) as is commonly assumed, but instead has other statistical shapes. By using these more appropriate statistics, Dainotti et al. (2023a), within the alternative cosmology framework, showed reduced uncertainties of the Hubble constant by 35%. This increased precision leads to values of H0 which are closer to the values of SNe Ia, but the discrepancy with the early Universe with CMB increases.

In addition, although a flat cosmological model is the most suitable one, there is a hint toward a closed Universe. Computations were carried out at facilities at the Center for Computational Astrophysics (CfCA), National Astronomical Observatory of Japan with the collaboration of the coauthor Iwasaki, Assistant Professor at Division of Science and at the CfCA.

Excited by the possibility of further investigating this tension with distant probes, the researchers strived to use quasars to increase the precision of the dark matter density, OM. Because quasars are observed at high distances, they are appealing probes for the early phases of the Universe. However, so far, precision on the evaluation of the cosmological parameters (e.g., OM) is possible only with SNe Ia. Dainotti et al. (2023b) have developed a method to determine a sample of quasars that constrain OM with the same precision as SNe Ia but reaching much higher distances.

To apply quasars in cosmology, they measured their distance through a physical relation between their X-ray and ultraviolet luminosities. This relation is reliable as a cosmological tool because it does not suffer from observational selection effects. However, its intrinsic dispersion was still too large to constrain cosmological parameters within a precision comparable to the one of SNe Ia. To overcome this issue, a statistical technique was applied to select from the original sample only the sources that present a small dispersion from the studied relation.

This new sample of quasars constitutes the "Gold sample", and yields a precision on OM unprecedentedly reached with only quasars, even greater than the current SNe Ia precision. This analysis also shows a trend toward OM =0.1

Research Report:Reducing the uncertainty on the Hubble constant up to 35% with an improved statistical analysis: different best-fit likelihoods for Supernovae Ia, Baryon Acoustic Oscillations, Quasars, and Gamma-Ray Bursts"

Research Report:Quasars: Standard Candles up to z = 7.5 with the Precision of Supernovae Ia

Related Links
Space Science at Hubble
Understanding Time and Space

Subscribe Free To Our Daily Newsletters

The following news reports may link to other Space Media Network websites.
Rewriting the past and future of the universe
Tokyo, Japan (SPX) Aug 22, 2023
New research has improved the accuracy of the parameters governing the expansion of the Universe. More accurate parameters will help astronomers determine how the Universe grew to its current state, and how it will evolve in the future. It is well established that the Universe is expanding. But with no landmarks in space, it is difficult to accurately measure how fast it is expanding. So, astronomers search for reliable landmarks. The same way a candle looks fainter as it gets farther away, even t ... read more

Indian lunar lander splits from propulsion module in key step

NASA challenges students to fly Earth and Space experiments

US seeks to extend China science accord, but only briefly for now

Embracing the future we need

Rocket Lab inks dedicated launch deal with Japanese EO company iQPS

NASA SpaceX Crew-7 'Go' for August 25 Launch

Rocket Lab Launches 40th Electron Mission, Successfully Flies Reused Engine

Elon Musk arrives in Japan for first visit since 2014

Martian Tapas With a View: Sols 3926-3927

Delight at Dream Lake

Scientists proposed to adapt a Mars ISRU system to the changing Mars environment

A 'Blissful' Martian Rock Paradise, Straight Ahead: Sols 3919-3920

From rice to quantum gas: China's targets pioneering space research

China to launch "Innovation X Scientific Flight" program, applications open worldwide

Scientists reveal blueprint of China's lunar water-ice probe mission

Shenzhou 15 crew share memorable moments from Tiangong Station mission

Atlas Credit Partners provides $100M strategic financing to AST SpaceMobile

Momentus announces reverse stock split

Pentagon awards contracts for next 'swarm' of tiny missile defense satellites

Intelsat completes C-Band spectrum clearing for 5G Deployment

True Anomaly opens GravityWorks; gains federal clearances for space operations

MIT engineers use kirigami to make ultrastrong, lightweight structures

China's new rules on AI-generated content

Taiwan's antique jade dealers see trade losing lustre

Size dependence and the collisional dynamics of protoplanetary dust growth

A "Jupiter" hotter than the Sun

Study explains how part of the nucleolus evolved

Watch an exoplanet's 17-year journey around its star

Neptune's Disappearing Clouds Linked to the Solar Cycle

The Road to Jupiter: Two decades of trajectory optimization

NASA's Europa probe gets a hotline to Earth

All Eyes on the Ice Giants

Subscribe Free To Our Daily Newsletters


The content herein, unless otherwise known to be public domain, are Copyright 1995-2023 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.