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arXiv · 1904.07874

On the detectability of visible-wavelength line emission from the local circumgalactic and intergalactic medium

Deborah Lokhorst·Roberto Abraham·Pieter van Dokkum·Nastasha Wijers·Joop Schaye
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Abstract

We describe a new approach to studying the intergalactic and circumgalactic medium in the local Universe: direct detection through narrow-band imaging of ultra-low surface brightness visible-wavelength line emission. We use the hydrodynamical cosmological simulation EAGLE to investigate the expected brightness of this emission at low redshift ($z$ $\lesssim$ 0.2). H$α$ emission in extended halos (analogous to the extended Ly$α$ halos/blobs detected around galaxies at high redshifts) has a surface brightness of $\gtrsim700$ photons cm$^{-2}$ sr$^{-1}$ s$^{-1}$ out to $\sim$100 kpc. Mock observations show that the Dragonfly Telephoto Array, equipped with state-of-the-art narrow-band filters, could directly image these structures in exposure times of $\sim$10 hours. H$α$ fluorescence emission from this gas can be used to place strong constraints on the local ultra-violet background, and on gas flows around galaxies. Detecting H$α$ emission from the diffuse intergalactic medium (the "cosmic web") is beyond current capabilities, but would be possible with a hypothetical 1000-lens Dragonfly array.

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Deborah Lokhorst, Roberto Abraham, Pieter van Dokkum, Nastasha Wijers, Joop Schaye. 2019-04-16. On the detectability of visible-wavelength line emission from the local circumgalactic and intergalactic medium. https://doi.org/10.3847/1538-4357%2Fab184e

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