Galaxies, star clusters, and the high-redshift Universe: a thread inspired by the really interesting paper by Vanzella et al. on today's arXiv. arxiv.org/abs/1809.02617
There's a lot we don't know about the earliest stages of galaxy evolution, particularly the Epoch of Reionization (redshifts ~6-10, when the Universe was < 1 billion years old)
Directly observing galaxies from that era is hard; even @NASAHubble is only capable of seeing progenitors of Milky Way like systems in typical regions of the sky
But, gravity can provide an assist: lensing magnifies some sources substantially, allowing @NASAHubble to see what would otherwise be far too faint.
And lensing is not just for galaxies: star clusters can also be lensed, if they exist and are caught at the right time. (It has to be the right time because star clusters form all of their stars in a very short period, so they will only be visible briefly in the rest frame UV)
Today, Vanzella et al. show results indicating that they've observed a dwarfy galaxy hosting a super star cluster forming at z~6.1! arxiv.org/abs/1809.02617
While the Vanzella et al. system is a somewhat bright host (M_UV ~ -17, with the star cluster being a factor of 4 fainter at M_UV ~ -15.6), there should be lots of fainter galaxies, and their star clusters could outshine the entire galaxy briefly adsabs.harvard.edu/abs/2018arXiv1…
JWST will make a huge difference for systems like this: what is difficult/impossible with HST will be routine with @NASAWebb. And we might learn a lot about both galaxies and star clusters / globular clusters this way.
Do globular clusters form at the centers of their own dark matter halos or in the outskirts of other galaxies? What reionized the Universe? When did the typical globular cluster form? So much science to do!
adsabs.harvard.edu/abs/2017arXiv1…
adsabs.harvard.edu/abs/2017arXiv1…
[End]
adsabs.harvard.edu/abs/2017arXiv1…
adsabs.harvard.edu/abs/2017arXiv1…
[End]
