RELICS-DP7: Spectroscopic Confirmation of a Dichromatic Primeval Galaxy at z ~ 7
| Autor: | Pelliccia, Debora, Strait, Victoria, Lemaux, Brian C., Bradac, Marusa, Coe, Dan, Bolan, Patricia, Bradley, Larry D., Frye, Brenda, Gandhi, Pratik J., Mainali, Ramesh, Mason, Charlotte, Ouchi, Masami, Sharon, Keren, Trenti, Michele, Zitrin, Adi |
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| Rok vydání: | 2020 |
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| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/2041-8213/abdf56 |
| Popis: | We report the discovery of a spectroscopically-confirmed strong Lyman-$\alpha$ emitter at $z=7.0281\pm0.0003$, observed as part of the Reionization Cluster Lensing Survey (RELICS). This galaxy, dubbed "Dichromatic Primeval Galaxy" at $z\sim7$ (DP7), shows two distinct components. While fairly unremarkable in terms of its ultraviolet (UV) luminosity ($\sim0.3L^{\ast}_{UV}$, where $L^{\ast}_{UV}$ is the characteristic luminosity), DP7 has one of the highest observed Lyman-$\alpha$ equivalent widths (EWs) among Lyman-$\alpha$ emitters at $z>6$ ($>200$ Angstrom in the rest frame). The strong Lyman-$\alpha$ emission generally suggests a young metal-poor, low-dust galaxy; however, we find that the UV slope $\beta$ of the galaxy as a whole is redder than typical star-forming galaxies at these redshifts, $-1.13\pm 0.84$, likely indicating, on average, a considerable amount of dust obscuration, or an older stellar population. When we measure $\beta$ for the two components separately, however, we find evidence of differing UV colors, suggesting two separate stellar populations. Also, we find that Lyman-$\alpha$ is spatially extended and likely larger than the galaxy size, hinting to the possible existence of a Lyman-$\alpha$ halo. Rejuvenation or merging events could explain these results. Either scenario requires an extreme stellar population, possibly including a component of Population III stars, or an obscured Active Galactic Nucleus. DP7, with its low UV luminosity and high Lyman-$\alpha$ EW, represents the typical galaxies that are thought to be the major contribution to the reionization of the Universe, and for this reason DP7 is an excellent target for follow-up with the James Webb Space Telescope. Comment: 8 pages, 3 figures, 2 table. Accepted for publication in ApJL |
| Databáze: | arXiv |
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