MUSE Analysis of Gas around Galaxies (MAGG) -- VII. Emission line galaxies near strong blended Ly$\hat{I}\pm$ absorption systems at $z\gtrsim 3$

Abstract

We investigate the connection between strong, blended Ly$\hat{I}\pm$ absorption systems (SBLAs) and $\approx 1000$ Ly$\hat{I}\pm$ emitting galaxies (LAEs) at $z\gtrsim 3$ 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 $\approx 138{\text{ km s}}^{-1}$ bins, we find a strong correlation with LAEs within a projected distance of $R\le 300\mathrm{kpc}$ and line-of-sight velocity separation of $|\hat{I}”v|\le 300{\text{ km s}}^{-1}$. 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$\hat{I}\pm$ 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.

Accepted for publication in A&A. 9 pages, 7 figures