Small and faint galaxies play a key role in explaining hydrogen emission from the early Universe
Astronomers conducting research using the James Webb Space Telescope were able to uncover one of the most mysterious secrets of astronomy — why the light of hydrogen atoms, which should have been blocked by gas, is observed in the galaxy environment of the early Universe.
This indicates the presence of weak Lyman-alpha radiation — light emitted by hydrogen atoms, which the researchers were able to detect using the NIRCam instrument. The data obtained and modern computer simulations of galaxies made it possible to establish that the source of this radiation — in a galaxy merger.
The process was explained by the study's author, Callum Witten: «One of the biggest mysteries — detection of radiation emanating from hydrogen atoms in the early Universe, which should have been completely blocked by the neutral gas formed after the Big Bang. Many hypotheses have been proposed to explain this radiation.
Observations with the telescope «James Webb» made it possible to resolve smaller and fainter galaxies near bright galaxies in which hydrogen emission was detected. A member of the research team, Sergio Martin-Alvarez, emphasizes: «Where “Hubble” saw only one large galaxy, “James Webb” sees a cluster of small interacting galaxies, and this is what had a huge impact on our understanding of the unexpected hydrogen emissions from some of the first galaxies.
Simultaneous application of data from the «James Webb» and computer models allows astronomers to continue solving long-standing puzzles about the early universe. They found that the rapid accumulation of stellar mass through galaxy mergers leads to strong hydrogen emission and facilitates the emission of this radiation through channels cleared of the abundance of neutral gas. Thus, the high rate of mergers of previously unobserved small galaxies provides a compelling solution to the long-standing mystery of early hydrogen emission.
The team is planning additional observations of galaxies in various stages of merger to continue to develop an understanding of how hydrogen emissions are released from these interacting systems.