MUSE Analysis of Gas around Galaxies (MAGG)

We investigate the connection between strong, blended Ly α absorption systems (SBLAs) and ≈1000 Ly α -emitting galaxies (LAEs) at z ≳ 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 ≈ 138 km s −1 bins, we find a strong correlation with LAEs within a projected distance of R ≤ 300 kpc and line-of-sight velocity separation of |Δ v | ≤ 300 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 circumgalactic medium (CGM) at the interface between the Ly α 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.