Скачать или смотреть Cooling Mechanisms for Primordial Star Formation

Presentation given by Gokul Kannan, Jeremy Chien, and Anthony Benjamin

Formation of the first stars requires cooling of primordial gas from greater than 10^6 K to near 500 K. Current established mechanisms are efficient until 10^4 K, when Bremsstrahlung radiation and other metal-based radiative mechanisms are no longer favored. Below 10^4 K, it is thought that H2 and HD-based termolecular collisions drive cooling. However, the inefficiency of such mechanisms leaves an open question in the formation of the first stars.
To bridge this knowledge gap, our group proposes a mechanism based in H3+, an abundant, long-lived reaction facilitator and precursor to other molecules in interstellar dust clouds. Previous mid-IR lasing lines were accidentally observed in supersonic H2 and rare gas plasmas. These 1430 cm^-1 emissions were assigned to 4d-4p transitions in the metastable H3 created from binary H3+ and electron recombination in plasma. This mechanism entails a top-down population inversion while emitting radiation to the lower 4p levels of H3. This new proposal suggests a more efficient cooling mechanism for condensing primordial gas for forming the first stars; as H3 Rydberg forms at a very high energy level, there is potential for large radiative energy release. H3 recombination kinetics are favorable as well; below 10^4 K, H3 maintains a relatively high rate coefficient and follows second order rate laws.
We aim to understand this mechanism’s role as a primary coolant of primordial gases below 10^4 K. Recent work on binary and ternary H3+ recombination with electrons, associative attachment of H- and H, and astrochemical implications are discussed.