An international team of scientists, featuring astronomers from Penn State, has utilized data from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) to construct the most extensive and accurate 3D map to date of excited hydrogen light in the early universe. This period spans approximately 9 to 11 billion years ago.
Unveiling Lyman Alpha: A Cosmic Beacon
This specific type of light, known as Lyman alpha, is produced in significant quantities when hydrogen atoms interact with stellar energy.
According to Robin Ciardullo, a Penn State professor of astronomy and astrophysics and a research team member, Lyman alpha radiation is a key indicator of galaxies during an era of intense star formation.
Previous studies had limited information on the locations of fainter galaxies and gas that also emit Lyman alpha radiation.
Methodology: Line Intensity Mapping
The new map brings these previously unobserved objects into focus, adding detail to this formative period of the universe, using a technique called Line Intensity Mapping.
This approach charts the distribution and concentration of specific elements across an entire region, differing from observing individual objects.
Maja Lujan Niemeyer, a HETDEX scientist who led the map's development, stated that observing the early universe provides insights into galaxy evolution and the function of intergalactic gas.
Julian Muñoz, a HETDEX scientist and co-author, explained Line Intensity Mapping as analogous to viewing a scene from a smudged window, capturing all light rather than just the brightest points.
HETDEX's Pivotal Role
While Line Intensity Mapping is not a novel technique, this application marks its first use for charting Lyman alpha emissions with such extensive data and precision.
HETDEX, operating the Hobby-Eberly Telescope in Texas, gathers over 600 million spectra across a vast sky area, aiming to map over one million bright galaxies to understand dark energy. The team leveraged a small fraction (approximately 5%) of the collected data.
Karl Gebhardt, HETDEX principal investigator, noted the substantial potential in using the remaining data for additional research.
Lujan Niemeyer highlighted that HETDEX observes everything in a given sky patch, but only a minimal amount of data relates to the brightest galaxies targeted by the project. The new map utilized the substantial light present in the seemingly empty regions between these bright galaxies.