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arXiv · 2304.02666

Early Results from GLASS-JWST XXIII: The transmission of Lyman-alpha from UV-faint z ~ 3-6 galaxies

Gonzalo Prieto-Lyon·Charlotte Mason·Sara Mascia·Emiliano Merlin·Namrata Roy·Alaina Henry·Guido Roberts-Borsani·Takahiro Morishita·Xin Wang·Kit Boyett·Patricia Bolan·Marusa Bradac·Marco Castellano·Amata Mercurio·Themiya Nanayakkara·Diego Paris·Laura Pentericci·Claudia Scarlata·Michele Trenti·Tommaso Treu·Eros Vanzella
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Abstract

Lyman-alpha (Ly$\alpha$) emission from galaxies can be used to trace neutral hydrogen in the epoch of reionization, however, there is a degeneracy between the attenuation of Ly$\alpha$ in the intergalactic medium (IGM) and the line profile emitted from the galaxy. Large shifts of Ly$\alpha$ redward of systemic due to scattering in the interstellar medium can boost Ly$\alpha$ transmission in the IGM during reionization. The relationship between Ly$\alpha$ velocity offset from systemic and other galaxy properties is not well-established at high-redshift or low luminosities, due to the difficulty of observing emission lines which trace systemic redshift. Rest-frame optical spectroscopy with JWST/NIRSpec has opened a new window into understanding of Ly$\alpha$ at z>3. We present a sample of 12 UV-faint galaxies ($-20 \lesssim$ MUV $\lesssim -16$) at $3 \lesssim z \lesssim 6$, with Ly$\alpha$ velocity offsets, $\Delta v_{\mathrm{Ly}\alpha}$, measured from VLT/MUSE and JWST/NIRSpec from the GLASS-JWST Early Release Program. We find median $\Delta v_{\mathrm{Ly}\alpha}$ of 205 km s$^{-1}$ and standard deviation 75 km s$^{-1}$, compared to 320 and 170km s$^{-1}$ for MUV < -20 galaxies in the literature. Our new sample demonstrates the previously observed trend of decreasing Ly$\alpha$ velocity offset with decreasing UV luminosity and optical line velocity dispersion, extends to MUV $\gtrsim$ -20, consistent with a picture where the Ly$\alpha$ profile is shaped by gas close to the systemic redshift. Our results imply that during reionization Ly$\alpha$ from UV-faint galaxies will be preferentially attenuated, but that detecting Ly$\alpha$ with low $\Delta v_{\mathrm{Ly}\alpha}$ can be an indicator of large ionized bubbles.

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Gonzalo Prieto-Lyon, Charlotte Mason, Sara Mascia, Emiliano Merlin, Namrata Roy, Alaina Henry, Guido Roberts-Borsani, Takahiro Morishita, Xin Wang, Kit Boyett, Patricia Bolan, Marusa Bradac, Marco Castellano, Amata Mercurio, Themiya Nanayakkara, Diego Paris, Laura Pentericci, Claudia Scarlata, Michele Trenti, Tommaso Treu, Eros Vanzella. 2023-04-05. Early Results from GLASS-JWST XXIII: The transmission of Lyman-alpha from UV-faint z ~ 3-6 galaxies. https://doi.org/10.3847/1538-4357%2Facf715

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