New research from the University of Michigan sheds light on the surprising star-forming capabilities of less evolved dwarf galaxies. Unlike their larger counterparts, these dwarf galaxies experience a 10-million-year delay in the onset of powerful galactic winds, allowing star-forming regions to retain their gas and dust, facilitating higher star formation rates.
In these relatively pristine dwarf galaxies, the researchers observed that massive stars, ranging from 20 to 200 times the sun’s mass, collapse into black holes instead of exploding as supernovae. This phenomenon delays the initiation of strong superwinds, which, in turn, prolongs star formation.
The Hubble tuning fork, a diagram classifying galaxies, was a reference for the researchers. They noted that the least evolved, smallest galaxies at the end of the tuning fork’s tines exhibited substantial star-forming regions, contrasting to more giant galaxies that have already converted their gas into stars.
The delay in galactic winds allows for gas retention, enabling astronomers to witness scenarios akin to the cosmic dawn—immediately following the Big Bang. In these pristine dwarf galaxies, gas clumps together, forming gaps that allow radiation to escape, resembling the “picket fence” model where ultraviolet radiation escapes between “slats” of gas.
This delay in superwinds provides a unique opportunity for astronomers to observe conditions similar to the early universe. UV radiation escapes through gaps in the gas, analogous to the universe transitioning from opaque to transparent after the Big Bang.
A subsequent study led by U-M astronomer Sally Oey, published in the Astrophysical Journal Letters, investigated the dwarf galaxy region Mrk 71, approximately 10 million light-years away. The team used the Hubble Space Telescope to examine the region and found observational evidence supporting the scenario proposed in the initial study.
Utilizing a filter set that analyzes the light of triply ionized carbon, the researchers observed a diffuse glow of ionized carbon throughout Mrk 71. This indicated that the energy within the region is radiated away, preventing the formation of a hot superwind. As a result, dense gas remains in the environment, aligning with the delayed galactic wind hypothesis.
These findings not only provide insights into the unique star-forming capabilities of dwarf galaxies but also have implications for understanding galaxies observed during cosmic dawn by the James Webb Space Telescope.
