Speaker
Description
Population III stars were the first generation of stars that formed in the Universe out of primordial gas. Thanks to JWST, we are now in an era where observing campaigns to discover Pop III stars has become a possibility. Over the last 3 years, several proposals on Pop III stars (from star cluster to galaxy scales) have been successful in getting time on JWST, however no convincing detections have resulted yet. The two most pertinent challenges are: 1.) if most Pop III stars were massive, they would have not survived for a time window long enough for JWST to capture them, and 2.) if they formed at redshifts > 15, which even with the sensitivity of JWST remains notoriously hard to observe.
There has been a longstanding idea that revolves around a 'low' redshift mode of Pop III star formation, which has recently garnered support from state of the art cosmological simulations. These simulations find copious amounts of pristine gas down to the end of Epoch of Reionization (EoR, z ~ 6), which could potentially harbour Pop III stars. If realistic, this could be a game changer since the natural expectation is that such Pop III stars would have been less massive, lived to a longer time period, and are located at cosmological distances within the reach of instruments aboard the JWST.
Motivated by these possibilities, we carry out the first 3D radiation magnetohydrodyamics simulations of Pop III star formation during the EoR. We find significant differences in the mass, multiplicity, radiation and cluster properties of Pop III stars between z = 6 and z > 15. Contrary to expectations, even though the gas is colder at z = 6, there is less fragmentation within the pristine cloud due to the combined effects of magnetic fields and radiation feedback. Differences in protostellar accretion rates at z = 6 and z > 15 lead to very distinct stellar evolution, which changes the amount of ionizing and dissociating photons produced, and subsequent escape fractions. The differences are even more dramatic when a background Lyman-Werner radiation appropriate at z = 6 is included. The differing nature of the low redshift mode of Pop III star formation is expected to modify spectral signatures, which are currently not accounted for in Pop III population synthesis models.
By providing realistic, full physics-guided estimates of the mass and radiation properties of these stars, our simulations provide much needed benchmarks for designing Pop III observing campaigns with JWST towards the end of the first billion years.
| Talk category | NOVA Network 2 |
|---|---|
| Preference for a talk or poster | Talk |
