颜色-颜色指纹将早型星系中的紫外超与溶解球状星团的第二代恒星联系起来
A Colour-colour Fingerprint Links the UV Upturn in Early-type Galaxies to Second-generation Stars from Dissolved Globular Clusters
AI总结：
通过HST/WFC3观测，发现F275W-F390W颜色梯度与紫外超强度相关，支持富金属球状星团溶解产生的第二代恒星（高氦、高氮）是紫外超起源的假说。
摘要：
我们探讨了早型星系（ETGs）中两个与质量相关的性质：（1）丰度比[N/Fe]和[Na/Fe]，以及（2）远紫外（FUV）波段中心集中的“紫外超”，这很可能由具有超太阳氦丰度的极端水平分支星产生。利用HST/WFC3对一个FUV弱和一个FUV强的ETG的新观测，我们检验了Goudfrooij提出的“MP情景”，该情景认为紫外超以及ETG内部和之间N和Na随质量变化的丰度差异在物理上相关，并由富金属球状星团的溶解产生——这是已知唯一发生He、N和Na质量依赖增丰的星系环境（即“多重星族”现象的第二代恒星）。我们表明，当结合F475W和F850LP的存档数据时，F275W和F390W波段对积分光测中$Y$和[N/Fe]的相关变化特别敏感。虽然F475W-F850LP在两个星系中都随半径增加而减小（与已知的金属丰度梯度一致），但F275W-F390W随半径增加而增大，正如紫外超由具有超太阳$Y$和[N/Fe]的第二代恒星引起所预期的那样。此外，F275W-F390W的径向梯度以及He和N增强星的隐含比例在FUV强的ETG中显著大于FUV弱的ETG，这与MP情景的预测一致。
英文摘要：
We address two mass-dependent properties among early-type galaxies (ETGs): (1) abundance ratios [N/Fe] and [Na/Fe], and (2) the centrally concentrated "UV upturn" at far-UV (FUV) wavelengths, which is likely produced by extreme horizontal branch stars with supersolar helium abundances. Using new HST/WFC3 observations of one FUV-weak and one FUV-bright ETG, we probe the "MP scenario" by Goudfrooij who posited that the UV upturn and the mass-dependent abundance variations of N and Na within and among ETGs are physically connected and produced by dissolution of metal-rich globular clusters, which represent the only galactic environment where mass-dependent enrichment of He, N, and Na is known to occur (i.e., second-generation stars of the "multiple stellar populations" (MPs) phenomenon). We show that passbands F275W and F390W are uniquely sensitive to correlated changes in $Y$ and [N/Fe] in integrated-light photometry when combined with archival data in F475W and F850LP. While F475W-F850LP is found to decrease with increasing radius in both galaxies, consistent with known metallicity gradients, F275W-F390W increases with increasing radius, as expected if the UV upturn is caused by second-generation stars with supersolar $Y$ and [N/Fe]. Furthermore, the radial gradient in F275W-F390W and the implied fractions of He- and N-enhanced stars are found to be significantly larger in the FUV-bright ETG than in the FUV-weak one, consistent with the predictions of the MP scenario.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
