New JWST paper from Lancaster’s @hmostevo.bsky.social 🧪🔭 #extragalactic

"Evidence that pre-processing in filaments drives the anisotropic quenching of satellite galaxies in massive clusters": academic.oup.com/mnras/articl...

P.S. If you are interested in my other works, you can check them out in the below links:

Quasar Sightline and Galaxy Evolution (QSAGE) – III. The mass–metallicity and fundamental metallicity relation of z ≈ 2.2 galaxies: academic.oup.com/mnras/articl...

I'll leave it there! A huge thanks goes Dr Kenneth Duncan and Corey Pirie for all their advice throughout this project, and of course to @jpsastro.bsky.social for his supervision!

Keep an eye out for other JELS papers!

I have linked my paper again here. Cheers!

arxiv.org/abs/2509.08045

Our results, combined with recent literature results, show that star-forming galaxies during the EoR build-up inconsistently through bursts of star formation. We suggest a more complex approach to galaxy evolution is needed at this epoch.

Galaxies build up their stellar mass either through in-situ star formation, or from mergers.

Given this, we determined a (major) merger fraction using close-pair analysis. Below is how our results compare to other studies, with good agreement with Puskás et al. (2025).

Pirie et al. (2025) found these galaxies are undergoing a current burst of star formation.

Mounting evidence in the literature suggests EoR galaxies have bursty star-forming histories.

So, combined with this, our results suggest these previous episodes may have been bursts!

Interestingly we found that emission from the established stellar populations is marginally more extended than the star-forming regions traced by Hα, as well as the near-UV (F277W). This suggests that previous episodes of star formation must have occurred to form this population!

This offset is expected, and using our size-mass relationship in rest-R-band (F444W) at 10^9.25 solar masses, we find an average size of ≈ 0.76 kpc. This is in good agreement with other studies at z ≈ 6, and a variety of size-z relationships from observations and simulations!

In our work, we measure the half-light radius of 23 HAEs at z=6.1 to determine the size-mass relationship at the EoR at multiple rest-frame wavelengths (near-UV, optical and Hα). We find a slope that agrees with the literature, but is negatively offset in size from lower-z works.

The sample we use for our work stems from the v0.8 z=6.1 Hα-emitters (HAEs) catalogue described in detail by Corey Pirie (Edinburgh) in his similarly excellent paper! We refer to this as the "parent" catalogue. I will delegate all the details to his work:

academic.oup.com/mnras/articl...

The possible science that will come from JELS is very exciting because of the nature of its homogeneous sample selection!

For all the details on the JELS observations and strategy, please see Kenneth Duncan's (Edinburgh) excellent survey paper:

academic.oup.com/mnras/articl...

JELS isolates the Hα emission line using JWST NIRCam F466N & F470N narrow-band filters at z = 6.1. Hα is associated with regions of active star formation as it originates from recombination in gas ionised by massive, short-lived (~10 Myr) stars.

(Figure from Duncan et al. 2025)

This work is the first full science paper from the JWST Emission Line Survey (JELS) - the first survey to perform narrow-band rest-optical emission line selection with JWST, and also the first to do so at the Epoch of Reionization (EoR)!

(Figure from Duncan et al. 2025)

Hello everyone! My first Bluesky posts!

I am very pleased to share that my 3rd first-author paper of my PhD is now available on arXiv! The paper has also been submitted to MNRAS following minor suggested revisions from the anonymous referee!

arxiv.org/abs/2509.08045

Thread on the details 🧵