2 weeks Ago By Pranjal Malewar
New measurements of the diffuse ionized hydrogen surrounding galaxies account for missing mass. Astronomers have struggled to account for all normal matter in the universe, with over half missing since the Big Bang 13.6 billion years ago.
New measurements suggest this missing matter is found more extensively in diffuse ionized hydrogen gas halos surrounding galaxies than previously thought. These findings resolve a conflict between observations and models of the universe’s evolution while revealing that black holes at galaxy centers may eject gas much farther than expected—up to five times farther. Presented by a team of 75 scientists, the study is undergoing peer review and highlights an important step toward understanding the universe’s matter distribution.
Dark matter constitutes about 84% of the universe’s matter and remains a mystery. The remaining 16% is normal matter, with only 7% forming stars. The rest exists as invisible hydrogen gas, mostly ionized, spread across galaxies and filaments that form a vast cosmic web.
This ionized gas and its associated electrons are known as the warm-hot intergalactic medium. It is too cold and diffuse to detect with standard astronomical techniques, making it elusive until recent discoveries shed light on its presence. The most accurate map of all the matter in the Universe Researchers estimated the distribution of ionized hydrogen gas around galaxies by analyzing data from around 7 million luminous red galaxies located within 8 billion light-years of Earth.
They measured the kinematic Sunyaev-Zel’dovich effect , which tracks slight changes in the cosmic microwave background (CMB) caused by electrons in the ionized gas. The CMB is a cosmic “backlight,” revealing the unseen gas. Galaxy data was collected by the Dark Energy Spectroscopic Instrument (DESI) on the Mayall Telescope in Arizona, which is creating a 3D map of the universe to study dark energy.
CMB measurements were made by the Atacama Cosmology Telescope (ACT) in Chile, which was known for its precise CMB observations before its decommissioning in 2022. The analysis, conducted with teams from DESI, ACT, Stanford University, and SLAC National Accelerator Laboratory, advances the understanding of ionized gas distribution in the universe. Astronomers once believed that massive black holes at galaxy centers expelled gas only during their early phases, known as active galactic nuclei (AGN) or quasars.
However, a new study suggests that the more diffuse and extensive ionized hydrogen halos around galaxies indicate that black holes may also become active later in their lives in duty cycles. This expulsion and return of gas, called feedback, regulates star formation in galaxies. Earlier hints of extended feedback were found in 2020, but the new study covers more galaxies with precise measurements.
It also reveals that gas isn’t evenly distributed but follows cosmic filaments across the universe. Current galaxy evolution models must now account for this more vigorous feedback. Identifying the missing matter in the universe, or baryons is crucial to addressing key questions in cosmology, such as the role of gas in cosmic evolution.
The expulsion of gas from massive galaxy cores challenges the idea that gas closely follows dark matter, potentially resolving inconsistencies in cosmological models, including issues about the universe’s clumpiness . Many astronomers are eager to explore this data further to understand galaxy formation and evolution. The researchers measured this gas using the kinematic Sunyaev-Zel’dovich effect, a technique that could also help study the early universe.
This approach may reveal insights into the large-scale structure of the cosmos and early physical laws and provide a way to test gravity and general relativity. Journal Reference: Hadzhiyska, B., Ferraro, S.
, Guachalla, B. R., Schaan, E.
, Aguilar, J., Battaglia, N., Bond, J.
R., Brooks, D., Calabrese, E.
, Choi, S. K., Claybaugh, T.
, Coulton, W. R., Dawson, K.
, Devlin, M., Dey, B., Doel, P.
, Duivenvoorden, A. J., Dunkley, J.
, Farren, G. S., .
. . Zou, H.
(2024). Evidence for large baryonic feedback at low and intermediate redshifts from kinematic Sunyaev-Zel’dovich observations with ACT and DESI photometric galaxies. ArXiv .
DOI: 10.48550/arXiv.2407.
07152 Topics Big Bang Galaxy Matter Universe.
