发表机构
University of Science and Technology of China（中国科学技术大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用DESI和SDSS双光纤观测的2万余个星系，通过统一重拟合光谱，定量测量了孔径偏差对光学发射线诊断的显著影响。
AI 中文摘要
固定角孔径采样了邻近星系的不同物理区域，因此可能使光学发射线诊断产生偏差。我们利用暗能量光谱仪（DESI）和斯隆数字巡天（SDSS）共同观测的20,545个高置信度发射线星系作为双光纤实验，其中DESI的1.5角秒光纤嵌套在SDSS的3角秒光纤内。为了将孔径效应与谱线测量系统效应分离，我们使用相同的eMILES恒星连续谱和发射线模型重新拟合每一条光谱，同时保留每条光谱的波长相关线扩展函数。这一共同重拟合产生了20,200个质量受控的匹配星系。相对于SDSS，较小的DESI孔径产生了微小但高度显著的偏移：$\Delta\log({\rm N2})=+0.0067\pm0.0002$，$\Delta\log({\rm S2})=-0.0148\pm0.0003$，$\Delta\log({\rm O3})=-0.0246\pm0.0006$，$\Delta{\rm O3N2}=-0.0327\pm0.0007$，以及$\Delta\log({\rm H}\alpha/{\rm H}\beta)=-0.0195\pm0.0003$，其中$\Delta$表示DESI减去SDSS。这些偏移在Baldwin--Phillips--Terlevich选择的恒星形成星系和近同心子集中持续存在。它们的幅度随红移分布变化，并且在控制红移后仍保留对表观光纤覆盖率的可测量依赖性，表明红移和相对孔径覆盖率共同调节孔径项。我们得出结论，对于高信噪比发射线星系，即使连续谱建模、发射线拟合和光谱分辨率处理保持固定，DESI--SDSS比较仍携带可测量的、依赖于诊断的光纤孔径项。
英文摘要
Fixed angular apertures sample different physical regions of nearby galaxies and can therefore bias optical emission-line diagnostics. We use 20,545 high-confidence emission-line galaxies observed by both the Dark Energy Spectroscopic Instrument (DESI) and the Sloan Digital Sky Survey (SDSS) as a two-fibre experiment, in which the DESI 1.5 arcsec fibre is nested within the SDSS 3 arcsec fibre. To isolate aperture effects from line-measurement systematics, we refit every spectrum using the same eMILES stellar-continuum and emission-line model while preserving the wavelength-dependent line-spread function of each spectrum. This common refit yields 20,200 quality-controlled matched galaxies. Relative to SDSS, the smaller DESI aperture produces small but highly significant offsets: $Δ\log({\rm N2})=+0.0067\pm0.0002$, $Δ\log({\rm S2})=-0.0148\pm0.0003$, $Δ\log({\rm O3})=-0.0246\pm0.0006$, $Δ{\rm O3N2}=-0.0327\pm0.0007$, and $Δ\log({\rm H}α/{\rm H}β)=-0.0195\pm0.0003$, where $Δ$ denotes DESI minus SDSS. These offsets persist in Baldwin--Phillips--Terlevich-selected star-forming galaxies and in a near-concentric subset. Their amplitudes vary across the redshift distribution and retain a measurable dependence on apparent fibre coverage after redshift is controlled, showing that redshift and relative aperture coverage jointly modulate the aperture terms. We conclude that, for high-S/N emission-line galaxies, DESI--SDSS comparisons carry measurable, diagnostic-dependent fibre-aperture terms even when continuum modelling, emission-line fitting, and spectral-resolution treatment are held fixed.
CommentsAccepted for publication
