{"title":"在 JWST 光谱中发现的 z ∼ 6 高 N/O 星系中的强 He i 发射线: 高 He/H 丰度比还是高电子密度?","authors":"Hiroto Yanagisawa, Masami Ouchi, Kuria Watanabe, Akinori Matsumoto, Kimihiko Nakajima, Hidenobu Yajima, Kentaro Nagamine, Koh Takahashi, Minami Nakane, Nozomu Tominaga, Hiroya Umeda, Hajime Fukushima, Yuichi Harikane, Yuki Isobe, Yoshiaki Ono, Yi Xu and Yechi Zhang","doi":"10.3847/1538-4357/ad72ec","DOIUrl":null,"url":null,"abstract":"We present He i/Hβ flux and He/H abundance ratios in three James Webb Space Telescope galaxies with significant constraints on N/O abundance ratios, GS-NDG-9422, RXCJ2248-ID, and GLASS150008 at z ∼ 6 mostly with the spectroscopic coverage from He iλ4471 and He iiλ4686 to He iλ7065, and comparing with 68 local dwarf galaxies. We find that these high-z galaxies present strong He i emission with He i/Hβ flux ratios generally larger than those of local dwarf galaxies. We derive He/H with all of the detected Hei, He ii, and 2−3 hydrogen Balmer lines in the same manner as the local He/H determination conducted for cosmology studies. These high-z galaxies show He overabundance He/H ≳0.10 or high electron density of ne ∼ 103−4 cm−3 much larger than local values at low O/H, . In contrast, we obtain low He/H and ne values for our local dwarf galaxies by the same technique with the same helium and hydrogen lines, and confirm that the difference between the high-z and local dwarf galaxies is not mimicked by systematics. While two scenarios of (1) He overabundance and (2) high electron density are not clearly concluded, we find that there is a positive correlation between the He/H–N/O or ne–N/O plane by the comparison of the high-z and local dwarf galaxies. Scenario (1) suggests that the overabundant helium and nitrogen are not explained by the standard chemical enrichment of core-collapse supernovae, but by the CNO-cycle products and equilibrium ratios, respectively. Scenario (2) indicates that the strong helium lines originated from the central dense clouds of the high-z galaxies by excessive collisional excitation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Strong He i Emission Lines in High N/O Galaxies at z ∼ 6 Identified in JWST Spectra: High He/H Abundance Ratios or High Electron Densities?\",\"authors\":\"Hiroto Yanagisawa, Masami Ouchi, Kuria Watanabe, Akinori Matsumoto, Kimihiko Nakajima, Hidenobu Yajima, Kentaro Nagamine, Koh Takahashi, Minami Nakane, Nozomu Tominaga, Hiroya Umeda, Hajime Fukushima, Yuichi Harikane, Yuki Isobe, Yoshiaki Ono, Yi Xu and Yechi Zhang\",\"doi\":\"10.3847/1538-4357/ad72ec\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We present He i/Hβ flux and He/H abundance ratios in three James Webb Space Telescope galaxies with significant constraints on N/O abundance ratios, GS-NDG-9422, RXCJ2248-ID, and GLASS150008 at z ∼ 6 mostly with the spectroscopic coverage from He iλ4471 and He iiλ4686 to He iλ7065, and comparing with 68 local dwarf galaxies. We find that these high-z galaxies present strong He i emission with He i/Hβ flux ratios generally larger than those of local dwarf galaxies. We derive He/H with all of the detected Hei, He ii, and 2−3 hydrogen Balmer lines in the same manner as the local He/H determination conducted for cosmology studies. These high-z galaxies show He overabundance He/H ≳0.10 or high electron density of ne ∼ 103−4 cm−3 much larger than local values at low O/H, . In contrast, we obtain low He/H and ne values for our local dwarf galaxies by the same technique with the same helium and hydrogen lines, and confirm that the difference between the high-z and local dwarf galaxies is not mimicked by systematics. While two scenarios of (1) He overabundance and (2) high electron density are not clearly concluded, we find that there is a positive correlation between the He/H–N/O or ne–N/O plane by the comparison of the high-z and local dwarf galaxies. Scenario (1) suggests that the overabundant helium and nitrogen are not explained by the standard chemical enrichment of core-collapse supernovae, but by the CNO-cycle products and equilibrium ratios, respectively. Scenario (2) indicates that the strong helium lines originated from the central dense clouds of the high-z galaxies by excessive collisional excitation.\",\"PeriodicalId\":501813,\"journal\":{\"name\":\"The Astrophysical Journal\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-10-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"The Astrophysical Journal\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.3847/1538-4357/ad72ec\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Astrophysical Journal","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3847/1538-4357/ad72ec","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
摘要
我们介绍了三个詹姆斯-韦伯太空望远镜星系(GS-NDG-9422、RXCJ2248-ID和GLASS150008)的He i/Hβ通量和He/H丰度比,这些星系对N/O丰度比具有重要的约束,其z∼ 6的光谱覆盖范围从He iλ4471 和He iiλ4686 到He iλ7065,并与68个本地矮星系进行了比较。我们发现,这些高兹星系有很强的 He i 辐射,He i/Hβ 通量比普遍大于本地矮星系。我们利用所有探测到的 Hei、He ii 和 2-3 条氢巴尔默线推导出 He/H,其方法与为宇宙学研究而进行的本地 He/H 测定相同。这些高赫兹星系显示出 He/H ≳0.10 的过量或 ne ∼ 103-4 cm-3 的高电子密度,远大于低 O/H 时的本地值。与此相反,我们用同样的技术和同样的氦线和氢线得到了本地矮星系的低He/H和ne值,证实了高兹星系和本地矮星系之间的差异不是由系统学模拟的。虽然没有明确得出(1)氦过剩和(2)电子密度过高这两种情况的结论,但我们发现通过对比高兹星系和本地矮星系,氦/氢-N/O平面或氖-N/O平面之间存在正相关。方案(1)表明,过量的氦和氮不是由核心坍缩超新星的标准化学富集来解释的,而是分别由CNO循环产物和平衡比来解释的。方案(2)表明,强氦线源自高兹星系中心致密云的过度碰撞激发。
Strong He i Emission Lines in High N/O Galaxies at z ∼ 6 Identified in JWST Spectra: High He/H Abundance Ratios or High Electron Densities?
We present He i/Hβ flux and He/H abundance ratios in three James Webb Space Telescope galaxies with significant constraints on N/O abundance ratios, GS-NDG-9422, RXCJ2248-ID, and GLASS150008 at z ∼ 6 mostly with the spectroscopic coverage from He iλ4471 and He iiλ4686 to He iλ7065, and comparing with 68 local dwarf galaxies. We find that these high-z galaxies present strong He i emission with He i/Hβ flux ratios generally larger than those of local dwarf galaxies. We derive He/H with all of the detected Hei, He ii, and 2−3 hydrogen Balmer lines in the same manner as the local He/H determination conducted for cosmology studies. These high-z galaxies show He overabundance He/H ≳0.10 or high electron density of ne ∼ 103−4 cm−3 much larger than local values at low O/H, . In contrast, we obtain low He/H and ne values for our local dwarf galaxies by the same technique with the same helium and hydrogen lines, and confirm that the difference between the high-z and local dwarf galaxies is not mimicked by systematics. While two scenarios of (1) He overabundance and (2) high electron density are not clearly concluded, we find that there is a positive correlation between the He/H–N/O or ne–N/O plane by the comparison of the high-z and local dwarf galaxies. Scenario (1) suggests that the overabundant helium and nitrogen are not explained by the standard chemical enrichment of core-collapse supernovae, but by the CNO-cycle products and equilibrium ratios, respectively. Scenario (2) indicates that the strong helium lines originated from the central dense clouds of the high-z galaxies by excessive collisional excitation.