The Interstellar Medium inDwarf Irregular Galaxies

Hunter, Deidre A.

doi:10.1146/annurev-astro-052622-031748

The Interstellar Medium inDwarf Irregular Galaxies

2024-09-13

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DOI：10.1146/annurev-astro-052622-031748

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Dwarf irregular (dIrr) galaxies are among the most common type of galaxy in the Universe. They typically have gas-rich, low-surface-brightness, metal-poor, and relatively thick disks. Here, we summarize the current state of our knowledge of the interstellar medium (ISM), including atomic, molecular, and ionized gas, along with their dust properties and metals. We also discuss star-formation feedback, gas accretion, and mergers with other dwarfs that connect the ISM to the circum galactic and intergalactic media. We high-light one of the most persistent mysteries: the nature of pervasive gas that is yet undetected as either molecular or cold hydrogen, the dark gas. Some highlights include the following: Significant quantities of Hiare in far-outer gas disks. Cold Hiin dIrrs would be molecular in the Milky Way, making the chemical properties of star-forming clouds significantly different. Stellar feedback has a much larger impact in dIrrs than in spiral galaxies. The escape fraction of ionizing photons is significant, making dIrrs aplausible source for reionization in the early Universe. Observations suggest a significantly higher abundance of hydrogen (H2or cold Hi) associated with CO in star-forming regions than that tracedby the CO alone

Keywords:

dwarf irregular galaxies

interstellar medium

atomic gas

molecular gas

CO-dark gas

dust

The Interstellar Medium inDwarf Irregular Galaxies

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