论文标题
来自IRAC5.8μm观测值的Hα+[N II]发射的高等效宽度[N II]发射：在重新离子化时期，有效的Lyman-Continuum光子产生有效的Lyman-Continuum光子的证据
High Equivalent Width of Hα+[N II] Emission in z~8 Lyman-break Galaxies from IRAC 5.8μm Observations: Evidence for Efficient Lyman-continuum Photon production in the Epoch of Re-ionization
论文作者
论文摘要
我们首次测量$ z \ sim8 $的星形星系中H $α$+[n ii]的中值等效宽度（EW）。我们的估计利用Spitzer/IRAC $5.8μ$ M -Band Mosaics（$ \ \ 5500-7100 $ a in $ z \ sim8 $）的独特光度深度（探测$ \ of 5500-7100 $ a），来自Spitzer（Greats）计划。在仔细消除了来自附近的来源的潜在污染后，我们将$ 102 $ Lyman-Break Galaxies的邮票叠加在$ 3.6、4.5、5.8 $和8.0μ$ M的邮票中。我们推断出一个极端的休息框架EW $ _0 $（H $α$+[n ii]）$ = 2328^{+1326} _ { - 1127} $ a来自测得的红色$ [3.6] - [5.8] = 0.82 \ pm0.27 $ mag，与年轻人一致（$ hime y sim at y y y y $ yr y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y y $ y y $ y y y y $ y mag sim sim sim sim sim sim 8 $这意味着$ \ log的电离光子生产效率（ξ_ {\ mathrm {ion}，0}/\ mathrm {erg \ hz}^{ - 1} = 25.97^{+0.18} _ { - 0.28} $。 Such a high value for photo production, similar to the highest values found at $z\lesssim4$, indicates that only modest escape fractions $f_\mathrm{esc}\lesssim0.3$ (at $2σ$) are sufficient for galaxies brighter than $M_\mathrm{UV}<-18$ mag to re-ionize the neutral Hydrogen at $z\sim8$.当考虑到比$ M_ \ Mathrm {uv} \大约-13 $ mag的星系明亮时，这一要求更加轻松到$ f_ \ mathrm {Esc} \ le 0.1 $，与最近的亮度功能相一致，并且通常在解决重新定性的研究中所假定。这些非凡的结果清楚地表明，星系可以是电源化光子的主要来源，并为我们提供了令人兴奋的一瞥，我们可能很快就会从即将发布的JWST/MIRI和NIRCAM程序中了解到早期宇宙，尤其是关于Reionization Epoch的知识。
We measure, for the first time, the median equivalent width (EW) of H$α$+[N II] in star-forming galaxies at $z\sim8$. Our estimate leverages the unique photometric depth of the Spitzer/IRAC $5.8μ$m-band mosaics (probing $\approx 5500 - 7100$ A at $z\sim8$) of the GOODS Reionization Era Wide Area Treasury from Spitzer (GREATS) program. We median stacked the stamps of $102$ Lyman-break galaxies in the $3.6, 4.5, 5.8$ and $8.0μ$m bands, after carefully removing potential contamination from neighbouring sources. We infer an extreme rest-frame EW$_0$(H$α$+[N II])$=2328^{+1326}_{-1127}$ A from the measured red $[3.6]-[5.8]=0.82\pm0.27$ mag, consistent with young ($\lesssim10^7$ yr) average stellar population ages at $z\sim8$. This implies an ionizing photon production efficiency of $\log(ξ_{\mathrm{ion},0}/\mathrm{erg\ Hz}^{-1})=25.97^{+0.18}_{-0.28}$. Such a high value for photo production, similar to the highest values found at $z\lesssim4$, indicates that only modest escape fractions $f_\mathrm{esc}\lesssim0.3$ (at $2σ$) are sufficient for galaxies brighter than $M_\mathrm{UV}<-18$ mag to re-ionize the neutral Hydrogen at $z\sim8$. This requirement is relaxed even more to $f_\mathrm{esc}\le 0.1$ when considering galaxies brighter than $M_\mathrm{UV}\approx -13$ mag, consistent with recent luminosity functions and as typically assumed in studies addressing re-ionization. These exceptional results clearly indicate that galaxies can be the dominant source of reionizing photons, and provide us with an exciting glimpse into what we might soon learn about the early universe, and particularly about the Reionization Epoch, from forthcoming JWST/MIRI and NIRCam programs.
