New method could accurately estimate cosmological distances

Researchers have identified a new potential methodology to precisely measure cosmic distances based on the Baryon Acoustic Oscillations (BAO). 
Mrigakshi Dixit
Recreation of Baryon Acoustic Oscillations
Recreation of Baryon Acoustic Oscillations

Zosia Rostomian, Lawrence Berkeley National Laboratory). 

Researchers have identified a new potential methodology to precisely measure cosmic distances based on the Baryon Acoustic Oscillations (BAO). 

As per the official release from the University of Cordoba, the presence of these waves was first proved in 2005. Interestingly, these waves were imprinted shortly after the Big Bang and can still be detected. 

BAO waves swept across the hot cosmic matter during the first 380,000 years of the universe's existence.

Shortly after the Big Bang, the universe expanded and eventually began to cool to the point where these waves were frozen in time, precisely where they were. Over time, galaxies formed along those frozen ripples. 

These frozen ripples stretched as the early universe expanded, increasing the distance between galaxies. 

Think of BAO as the universe's cosmic ruler, helping scientists measure the rate of the universe's expansion and cosmic distances. 

However, the difficulty is determining the precise placement of these frozen waves in the vast universe. 

Examining a database of nearly one million galaxies

Astronomers previously depended on galaxy clusters to discover these frozen waves, but this new study shows how to locate them by examining galaxy shapes and orientations. 

Using statistical approaches, the researchers examined a nearly one million galaxies database. 

According to the official release, they were particularly interested in gathering data on two distinct factors: "the ellipticity of the galaxies and the density around them."

In the universe, galaxies tend to stretch in the direction where more galaxies are clustered together, influenced by the force of gravity. However, there are specific regions where this gravitational effect is less significant.

"It is in those points, where galaxies do not point where they should, where statistics tell us that the Baryon Acoustic Oscillations are located, since these waves also act as points of gravity attraction," explained Antonio J. Cuesta, one of the authors of this new study. 

Using this information set, researchers could more precisely determine galaxies' precise positions and distances. This enhanced knowledge could be leveraged to create more accurate maps of the universe.

"The first practical application that this study could have is to establish more precisely where the galaxies are located and the separation between them and the Earth, but, in a way, we are also gazing into the past," Cuesta added. 

This novel strategy might help scientists better grasp the universe's perplexing expansion, a process that they are now unable to explain thoroughly.

It may also give insight into other governing mysteries about the cosmos, such as the enigmatic dark matter and energy. 

The results have been published in the journal Nature Astronomy.

Study abstract:

The baryon acoustic oscillation feature in the clustering of galaxies or quasars provides a ‘standard ruler’ for distance measurements in cosmology. In this work, we report a 2–3σsignal of the baryon acoustic oscillation dip feature in the galaxy density–ellipticity cross-correlation functions using the spectroscopic sample of the Baryon Oscillation Spectroscopic Survey CMASS, combined with the deep Dark Energy Spectroscopic Instrument Legacy Imaging Surveys for precise galaxy shape measurements. We measure the galaxy–ellipticity correlation functions and model them using the linear alignment model. We constrain the distance DV/rd to redshift 0.57 to a precision of 3–5%, depending on the details of modelling. The galaxy–ellipticity measurement reduces the uncertainty of distance measurement by ~10% on top of that derived from the galaxy–galaxy correlation. More importantly, for future large and deep galaxy surveys, the independent galaxy–ellipticity measurements can help sort out the systematics in the baryon acoustic oscillation studies.

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