Revealing Hidden Galaxies in the Local Group: A New Discovery

An image from the HESTIA simulations depicts dark matter (in red), gas (green), and stars (white) within a simulated Local Group. The Milky Way and Andromeda galaxy analogs are positioned centrally, and ultra-diffuse galaxies are highlighted with circles. Salvador Cardona-Barrero is credited for the image.

A group of international researchers anticipates the identification of large, faint galaxies, potentially revolutionizing our understanding of the cosmos and theories of galaxy formation.

Employing the most sophisticated and detailed cosmic simulations to date, this team predicts the existence of numerous faint galaxies in our cosmic vicinity, poised for discovery.

Ultra-Diffuse Galaxies Explored

The research delves into ultra-diffuse galaxies, which are faint and possess masses up to a billion Suns – roughly one-thousandth of the Milky Way’s mass. They extend across areas similar to the Milky Way’s size, rendering them extremely faint and challenging to detect, thus remaining largely elusive.

The Local Group, comprising about 60 known galaxies including the Milky Way and Andromeda, is believed to be a promising site for finding more of these galaxies. Presently, only two ultra-diffuse galaxies have been identified in the Local Group, but comprehending their total number is deemed essential for a deeper cosmic understanding.

Insights from HESTIA Simulations

What additional galaxies might exist in our cosmic vicinity? To answer this, the team utilized the HESTIA simulations – the most precise and detailed representations of the Milky Way and its neighboring area. Named after the Greek goddess of home, these simulations suggest the possible existence of up to 12 undiscovered ultra-diffuse galaxies in the Local Group. Analysis of these galaxies in the HESTIA simulations indicates that some might be detectable with existing data from surveys like the Sloan Digital Sky Survey.

Galaxy Formation: Broader Implications

Unearthing these galaxies could profoundly impact our grasp of galaxy formation and evolution. Present theories propose that nearly half of all low-mass galaxies in the universe are extended and diffuse, with most being beyond our current observational capabilities. The number of galaxies is a key prediction in various cosmological models, so discovering the full scope of ultra-diffuse galaxies in the Local Group could invalidate some of these models.

This research is detailed in “The Undiscovered Ultradiffuse Galaxies of the Local Group,” published in The Astrophysical Journal Letters, authored by Oliver Newton, Arianna Di Cintio, Salvador Cardona–Barrero, Noam I. Libeskind, Yehuda Hoffman, Alexander Knebe, Jenny G. Sorce, Matthias Steinmetz, and Elmo Tempel, dated March 30, 2023.
DOI: 10.3847/2041-8213/acc2bb

Frequently Asked Questions (FAQs) about Ultra-Diffuse Galaxies

More about Ultra-Diffuse Galaxies

• HESTIA Project Overview
• Ultra-Diffuse Galaxies Explained
• The Astrophysical Journal Letters
• Local Group Astronomy
• Sloan Digital Sky Survey Data
• Cosmological Models and Theories