The MOSDEF survey: a comprehensive analysis of the rest-optical emission-line properties of z ∼ 2.3 star-forming galaxies
The MOSDEF survey: a comprehensive analysis of the rest-optical emission-line properties of z ∼ 2.3 star-forming galaxies
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DOI：
10.1093/mnras/stab119
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发表时间：
2021-01
影响因子：
4.8
通讯作者：
Jordan N. Runco;A. Shapley;R. Sanders;M. Topping;M. Kriek;N. Reddy;A. Coil;B. Mobasher;B. Siana;W. Freeman;I. Shivaei;Mojegan Azadi;S. Price;G. Leung;T. Fetherolf;Laura de Groot-Laura-de Groot-2124568861;T. Zick;F. Fornasini;G. Barro
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文献类型：
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作者：
Jordan N. Runco;A. Shapley;R. Sanders;M. Topping;M. Kriek;N. Reddy;A. Coil;B. Mobasher;B. Siana;W. Freeman;I. Shivaei;Mojegan Azadi;S. Price;G. Leung;T. Fetherolf;Laura de Groot-Laura-de Groot-2124568861;T. Zick;F. Fornasini;G. Barro
我们分析了完整的MOSFIRE深部演化场观测中z∼2.3恒星形成星系的静止光发射线光谱。在研究[O III]λ5 0 0 8/HβVS[N II]λ6 5 85/Hα(‘[N II]BPT’)图中高红移星系序列和局部星系序列之间众所周知的偏移量的来源时，我们定义了两类z∼2.3MOSDEF星系。这包括相对于本地序列向更高的[O III]λ5008/Hβ和/或[N II]λ6585/Hα偏移的高种群，以及与该序列重叠的低种群。这两个群在[O III]λ5008/Hβ对[S II]λλ6718,6733/Hα和[O III]λλ4960,5008/[O II]λλ3727,3730(O32)对([O III]λλ4960,5008+[O II]λλ3727,3730)/Hβ(R23)图中也是分开的，这定性地表明，在较偏移的星系中，恒星形成区的特征是在固定的星云氧丰度下具有较硬的电离光谱。我们还研究了分裂样本的许多星系性质，发现高样本的平均尺寸较小，质量较小，但具有较高的比恒星形成率(SFR)和SFR面密度值，并且与低样本相比略年轻。根据Cloudy+BPASS光电离模型，我们估计高布居数比低布居数具有较低的恒星金属丰度(即较硬的电离光谱)，但星云金属丰度略高，电离参数较高。虽然高群体比低群体更有α增强(即更高的α/Fe)，但与具有相似静止-光学线比的本地恒星形成星系相比，这两个样本的α增强程度明显更高。这些差异必须在所有高红移恒星形成星系中得到解释--不仅仅是那些从局部激发序列“偏移”出来的星系。
We analyse the rest-optical emission-line spectra of z ∼ 2.3 star-forming galaxies in the complete MOSFIRE Deep Evolution Field (MOSDEF) survey. In investigating the origin of the well-known offset between the sequences of high-redshift and local galaxies in the [O iii]λ5008/Hβ versus [N ii]λ6585/Hα (‘[N ii] BPT’) diagram, we define two populations of z ∼ 2.3 MOSDEF galaxies. These include the high population that is offset towards higher [O iii]λ5008/Hβ and/or [N ii]λ6585/Hα with respect to the local SDSS sequence and the low population that overlaps the SDSS sequence. These two groups are also segregated within the [O iii]λ5008/Hβ versus [S ii]λλ6718,6733/Hα and the [O iii]λλ4960,5008/[O ii ]λλ3727,3730 (O32) versus ([O iii]λλ4960,5008+[O ii]λλ3727,3730)/Hβ (R23) diagrams, which suggests qualitatively that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. We also investigate many galaxy properties of the split sample and find that the high sample is on average smaller in size and less massive, but has higher specific star formation rate (SFR) and SFR surface density values and is slightly younger compared to the low population. From Cloudy+BPASS photoionization models, we estimate that the high population has a lower stellar metallicity (i.e. harder ionizing spectrum) but slightly higher nebular metallicity and higher ionization parameter compared to the low population. While the high population is more α-enhanced (i.e. higher α/Fe) than the low population, both samples are significantly more α-enhanced compared to local star-forming galaxies with similar rest-optical line ratios. These differences must be accounted for in all high-redshift star-forming galaxies – not only those ‘offset’ from local excitation sequences.