MUSE Analysis of Gas around Galaxies (MAGG) -- VII. Emission line galaxies near strong blended Ly$\alpha$ absorption systems at $z\gtrsim3$

TL;DR

This study reveals a strong spatial and velocity correlation between strong, blended Ly$eta$ absorption systems and Ly$eta$ emitting galaxies at high redshift, indicating SBLAs as effective probes of the circumgalactic medium.

Contribution

It demonstrates the connection between SBLAs and LAEs at $z extgreater3$, highlighting the dependence on spectral binning and confirming SBLAs as CGM tracers.

Findings

Strong LAE-SBLA clustering within 300 kpc and 300 km/s.

Correlation strength increases with decreasing flux and smaller separations.

No clustering observed for spectral regions with flux > 0.25.

Abstract

We investigate the connection between strong, blended Ly$\alpha$ absorption systems (SBLAs) and $\approx1000$ Ly$\alpha$ emitting galaxies (LAEs) at $z\gtrsim3$ in 28 quasar fields from the MUSE Analysis of Gas around Galaxies (MAGG) survey. Selecting SBLAs as spectral regions with transmitted flux $-0.05<F<0.25$ over $\approx138\text{ km s}^{-1}$ bins, we find a strong correlation with LAEs within a projected distance of $R\le300\rm\,kpc$ and line-of-sight velocity separation of $|\Delta v|\le300 \text{ km s}^{-1}$. The association rate increases significantly with decreasing flux, a trend that persists also at smaller separations ($R<100$ kpc). A two-dimensional cross-correlation analysis confirms significant clustering of LAEs around SBLAs, while no such clustering is seen for spectral regions with $F>0.25$. The correlation appears to also depend on the width of the spectral window used to identify SBLAs, with a larger window yielding a stronger signal. Our analysis confirms that SBLAs serve as probes of the CGM at the interface between the Ly$\alpha$ forest and the optically-thick Lyman limit systems. The significant dependence of the LAE-SBLA cross-correlation on the spectral binning used to select these absorbers motivates future tests of the current SBLA framework as a tracer of halos.