JADES: Discovery of extremely high equivalent width Lyman-alpha emission from a faint galaxy within an ionized bubble at z=7.3
| Autor: | Saxena, Aayush, Robertson, Brant E., Bunker, Andrew J., Endsley, Ryan, Cameron, Alex J., Charlot, Stephane, Simmonds, Charlotte, Tacchella, Sandro, Witstok, Joris, Willott, Chris, Carniani, Stefano, Curtis-Lake, Emma, Ferruit, Pierre, Jakobsen, Peter, Arribas, Santiago, Chevallard, Jacopo, Curti, Mirko, D'Eugenio, Francesco, De Graaff, Anna, Jones, Gareth C., Looser, Tobias J., Maseda, Michael V., Rawle, Tim, Rix, Hans-Walter, Del Pino, Bruno Rodríguez, Smit, Renske, Übler, Hannah, Eisenstein, Daniel J., Hainline, Kevin, Hausen, Ryan, Johnson, Benjamin D., Rieke, Marcia, Williams, Christina C., Willmer, Christopher N. A., Baker, William M., Bhatawdekar, Rachana, Bowler, Rebecca, Boyett, Kristan, Chen, Zuyi, Egami, Eiichi, Ji, Zhiyuan, Nelson, Erica, Perna, Michele, Sandles, Lester, Scholtz, Jan, Shivaei, Irene |
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| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | A&A 678, A68 (2023) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/202346245 |
| Popis: | We report the discovery of a remarkable Ly$\alpha$ emitting galaxy at z = 7.2782, JADES-GS-z7-LA, with EW$_0$(Ly$\alpha$) $= 388.0 \pm 88.8$\AA and UV magnitude -17.0. The spectroscopic redshift is confirmed via rest-frame optical lines [O II], H$\beta$ and [O III] in its JWST/NIRSpec Micro-Shutter Assembly (MSA) spectrum. The Ly$\alpha$ line is detected in both lower resolution PRISM as well as medium resolution G140M grating spectra. The LSF-deconvolved Ly$\alpha$ FWHM in the grating is $383.9 \pm 56.2$ km/s and the Ly$\alpha$ velocity offset compared to the systemic redshift is $113.3 \pm 80.0$ km/s, indicative of very little neutral gas or dust within the galaxy. We estimate the Ly$\alpha$ escape fraction to be >70%. JADES-GS-z7-LA has a O32 ratio of $11.1 \pm 2.2$ and a R23 ratio of $11.2 \pm 2.6$, consistent with low metallicity and high ionization parameters. Deep NIRCam imaging also revealed a close companion source (separated by 0.23"), which exhibits similar photometry to that of JADES-GS-z7-LA, with a photometric excess in the F410M NIRCam image consistent with [O III]+H$\beta$ emission at the same redshift. The spectral energy distribution of JADES-GS-z7-LA indicates a "bursty" star formation history, with a low stellar mass of $\approx 10^7$ $M_\odot$. Assuming that the Ly$\alpha$ transmission through the intergalactic medium is the same as its measured escape fraction, an ionized region of size > 1.5 pMpc is needed to explain the high Ly$\alpha$ EW and low velocity offset compared to systemic seen in JADES-GS-z7-LA. Owing to its UV-faintness, we show that it is incapable of single-handedly ionizing a region large enough to explain its Ly$\alpha$ emission. Therefore, we suggest that JADES-GS-z7-LA (and possibly the companion source) may be a part of a larger overdensity, presenting direct evidence of overlapping ionized bubbles at $z>7$. Comment: 14 pages, 8 figures, Accepted for publication in A&A |
| Databáze: | arXiv |
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