Title: Broad emission lines in optical spectra of hot dust-obscured galaxies can contribute significantly to JWST/NIRCam photometry Show Chinese title

Title: 热尘蔽 galaxy 的光学光谱中的宽发射线可以对 JWST/NIRCam 光度学做出显著贡献。

Abstract: Selecting the first galaxies at z>7-10 from JWST surveys is complicated by z<6 contaminants with degenerate photometry. For example, strong optical nebular emission lines at z<6 may mimic JWST/NIRCam photometry of z>7-10 Lyman Break Galaxies (LBGs). Dust-obscured 3<z<6 galaxies in particular are potentially important contaminants, and their faint rest-optical spectra have been historically difficult to observe. A lack of optical emission line and continuum measures for 3<z<6 dusty galaxies now makes it difficult to test their expected JWST/NIRCam photometry for degenerate solutions with NIRCam dropouts. Towards this end, we quantify the contribution by strong emission lines to NIRCam photometry in a physically motivated manner by stacking 21 Keck II/NIRES spectra of hot, dust-obscured, massive ($\log\mathrm{M_*/M_\odot}\gtrsim10-11$) and infrared (IR) luminous galaxies at z~1-4. We derive an average spectrum and measure strong narrow (broad) [OIII]5007 and H$\alpha$ features with equivalent widths of $130\pm20$ A ($150\pm50$ A) and $220\pm30$ A ($540\pm80$ A) respectively. These features can increase broadband NIRCam fluxes by factors of 1.2-1.7 (0.2-0.6 mag). Due to significant dust-attenuation ($A_V\sim6$), we find H$\alpha$+[NII] to be significantly brighter than [OIII]+H$\beta$, and therefore find that emission-line dominated contaminants of high-z galaxy searches can only reproduce moderately blue perceived UV continua of $S_\lambda\propto\lambda^\beta$ with $\beta>-1.5$ and z>4. While there are some redshifts (z~3.75) where our stack is more degenerate with the photometry of z>10 LBGs between $\lambda_{rest}\sim0.3-0.8\,\mu$m, redder filter coverage beyond $\lambda_{obs}>3.5\,\mu$m and far-IR/sub-mm follow-up may be useful for breaking the degeneracy and making a crucial separation between two fairly unconstrained populations, dust-obscured galaxies at z~3-6 and LBGs at z>10. Show Chinese abstract

Abstract: 从JWST巡天中选择红移\(z>7-10\)的首批星系因红移\(z<6\)的光谱退化污染物而变得复杂。例如，红移\(z<6\)的强光学星云发射线可能模仿红移\(z>7-10\)莱曼破裂星系(LBGs)的JWST/NIRCam测光值。特别是，3<\(z\)<6的尘埃遮蔽星系可能是重要的污染物，它们微弱的静止光学光谱历史上难以观测。缺乏3<\(z\)<6尘埃星系的光学发射线和连续谱测量现在使得很难测试它们预期的NIRCam滴落与退化解的JWST/NIRCam测光值。为此，我们通过堆叠21个凯克II/NIRES光谱，在物理基础上量化了强发射线对NIRCam测光的贡献，这些光谱来自红移\(z\sim1-4\)的炽热、尘埃遮蔽、质量大（$\log\mathrm{M_*/M_\odot}\gtrsim10-11$）且红外(IR)亮度高的星系。我们推导出平均光谱，并分别测量了等效宽度为$130\pm20$Å ($150\pm50$Å)和$220\pm30$Å ($540\pm80$Å)的强窄(宽)\([OIII]5007\)和H$\alpha$特征。这些特征可以使宽带NIRCam流量增加1.2-1.7倍（0.2-0.6星等）。 由于显著的尘埃消光（$A_V\sim6$），我们发现H$\alpha$+[NII]比[OIII]+H$\beta$明显更亮，因此得出结论，高红移星系搜索中的发射线主导污染只能部分再现$S_\lambda\propto\lambda^\beta$的适度偏蓝的UV连续谱，且条件为$\beta>-1.5$和 z>4。 尽管在某些红移（约z=3.75）上，我们的堆叠与z>10的LBG（Lyman-break galaxy）在$\lambda_{rest}\sim0.3-0.8\,\mu$m波段的测光数据更为退化，但超过$\lambda_{obs}>3.5\,\mu$m的红滤光片覆盖范围以及远红外/亚毫米波段的后续观测可能有助于打破这种退化，并在两个相对不受约束的群体之间做出关键区分，即z~3-6的尘埃遮蔽星系和z>10的LBG。