论文标题
Z〜7时不需要极端恒星质量：COS-87259的测试案例研究
No Need for Extreme Stellar Masses at z~7: A Test-case Study of COS-87259
论文作者
论文摘要
关于Z> 6处的大规模存在（log（m/msun）> 11）星系存在的最新争议对银河系理论构成了挑战。因此，了解拟合方法对电离星系时期恒星质量估计的影响至关重要。在这项工作中，我们对具有光谱红移Z = 6.853的AGN宿主星系候选cos-87259进行了案例研究，据称其具有极高的恒星质量（m/msun）〜11.2。我们在我们独立测量的17个宽带中的光度法上测试了一套不同的SED拟合算法和恒星种群模型的套件。在五个不同的代码设置之间，cos-87259跨度log（m/msun）的恒星质量估计值= 10.24-11.00，而拟合的卡方值降低了DCHI2 = 1.2中的统一值，因此SED拟合的质量基本上是不可分割的。只有当我们在探矿者中采用非参数恒星形成历史模型时，才能检索超过日志的恒星质量（m/msun）= 11。尽管在使用先前报道的该来源的光度法时，衍生的恒星质量会发生变化，但非参数拟合方法始终产生最高值。随着这些模型在詹姆斯·韦伯（James Webb）太空望远镜高红移科学方面变得越来越流行，我们强调了测试各种SED拟合程序的绝对重要性，尤其是在如此高的红移中显然非常庞大的星系上。
Recent controversy regarding the existence of massive (log(M/Msun)>11) galaxies at z>6 poses a challenge for galaxy formation theories. Hence, it is of critical importance to understand the effects of SED fitting methods on stellar mass estimates of Epoch of Reionization galaxies. In this work, we perform a case study on the AGN host galaxy candidate COS-87259 with spectroscopic redshift z=6.853, that is claimed to have an extremely high stellar mass of log(M/Msun)~11.2. We test a suite of different SED fitting algorithms and stellar population models on our independently measured photometry in 17 broad bands for this source. Between five different code setups, the stellar mass estimates for COS-87259 span log(M/Msun)=10.24-11.00, whilst the reduced chi-squared values of the fits are all close to unity within dchi2=1.2, so that the quality of the SED fits is basically indistinguishable. Only when we adopt a nonparametric star formation history model within Prospector do we retrieve a stellar mass exceeding log(M/Msun)=11. Although the derived stellar masses change when using previously reported photometry for this source, the nonparametric SED-fitting method always yields the highest values. As these models are becoming increasingly popular for James Webb Space Telescope high-redshift science, we stress the absolute importance of testing various SED fitting routines particularly on apparently very massive galaxies at such high redshifts.
