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Star formation in the first galaxies
textThe ignition of the first sources of light marked the end of the cosmic dark ages, an era when the Universe transitioned from the relatively simple conditions following the Big Bang to the complex tapestry of dark matter, baryons, and pervasive cosmic radiation fields we see today. To better understand this uncharted cosmic epoch, we primarily utilize hydrodynamical, N-body simulations to model the assembly of the first galaxies at redshifts greater than ten and the stars that form within them. These simulations begin from cosmological initial conditions, employ a robust, non-equilibrium chemo-thermodynamic model, and take advantage of adaptive-grid-refinement to probe the multi-scale, complex process of star formation from ab initio principles. We explore the consequences that metal enrichment has on the process of star formation, confirming the presence of a critical metallicity for low-mass star formation. To assess the observational prospects of these primeval stellar populations with next-generation telescopes, like the James Webb Space Telescope, we constrain the star formation efficiency of both metal-enriched and metal-free star formation in a typical first galaxy. We also resolve the formation of individual metal-enriched stars in simulations that ultimately began from cosmological scales, allowing meaningful comparisons between our simulations and the recently discovered ultra-faint dwarf satellite galaxies, the suspected analogs of the first galaxies in the local Universe.Astronom
Primordial star clusters at extreme magnification
Gravitationally lensed galaxies with magnification ~10-100 are routinely
detected at high redshifts, but magnifications significantly higher than this
are hampered by a combination of low probability and large source sizes.
Magnifications of ~1000 may nonetheless be relevant in the case of
intrinsically small, high-redshift objects with very high number densities.
Here, we explore the prospects of detecting compact (< 10 pc), high-redshift (z
> 7) Population III star clusters at such extreme magnifications in large-area
surveys with planned telescopes like Euclid, WFIRST and WISH. We find that the
planned WISH 100 sq. deg ultradeep survey may be able to detect a small number
of such objects, provided that the total stellar mass of these star clusters is
> 10000 solar masses. If candidates for such lensed Population III star
clusters are found, follow-up spectroscopy of the surrounding nebula with the
James Webb Space Telescope or groundbased Extremely Large Telescopes should be
able to confirm the Population III nature of these objects. Multiband
photometry of these objects with the James Webb Space Telescope also has the
potential to confirm that the stellar initial mass function in these Population
III star clusters is top-heavy, as supported by current simulations.Comment: 8 pages, 3 figures. v.2: Accepted for publication by MNRAS, with
updated WISH detection limit