论文标题
那些小事是什么？与JWST的SMACS0723字段中紧凑型星团的首次研究
What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST
论文作者
论文摘要
我们将JWST NIRCAM早期发行的前所未有的分辨率和深度（1-5 $ $ m m）在SMACS J0723.3-7327 Galaxy群集中的寄主星系附近的恒星星系群中的恒星质量，年龄和金属性研究恒星质量，年龄和金属性。这些恒星簇的测得的颜色在同一红移时显示出与静态星系相似的分布，但比当前宽田星系调查的深度> 3个幅度。在NIRCAM/F150W数据中未解决恒星簇，表明小于50pc的大小。这比局部星系中的恒星形成团块或矮星系要小得多。从将其光度法与简单的恒星总体（SSP）模型拟合在一起，我们发现恒星金属度与0.2-0.3 $ z _ {\ odot} $一致，年龄为$ 1.5^{+0.5} _ { - 0.5} _ { - 0.5} $ gyrs。我们排除金属<0.2 $ z _ {\ odot} $和4 $σ$显着性的太阳能/超极。假设从最佳拟合SSP获得的质量与光比，我们估计恒星质量为$ 2.4^{+3.0} _ { - 1.5} \ times10^6 $ m $ _ {\ odot} $。这些是在局部球状簇和矮星系的平均质量之间。我们的分析表明，在z = 0.5-0.7时，中期球状的形成时间相对较新，由于群集环境中的相互作用或在冷流中形成群集核心，可能随后将其从宿主星系中剥离。但是，我们不能排除这些对象是剥离矮星系的紧凑核心。
We use the unprecedented resolution and depth of the JWST NIRCam Early Release Observations at 1-5 $μ$m to study the stellar mass, age, and metallicity of compact star clusters in the neighborhood of the host galaxies in the SMACS J0723.3-7327 galaxy cluster field at z = 0.39. The measured colors of these star clusters show a similar distribution as quiescent galaxies at the same redshift, but are >3 magnitudes fainter than the current depths of wide-field galaxy survey. The star clusters are unresolved in the NIRCam/F150W data suggesting sizes smaller than 50pc. This is significantly smaller than star forming clumps or dwarf galaxies in local galaxies. From fitting their photometry with simple stellar population (SSP) models, we find stellar metallicities consistent with 0.2-0.3 $Z_{\odot}$ and ages of $1.5^{+0.5}_{-0.5}$ Gyrs. We rule out metallicities <0.2 $Z_{\odot}$ and solar/super-solar at 4$σ$ significance. Assuming mass-to-light ratios obtained from the best-fit SSPs, we estimate stellar masses of $2.4^{+3.0}_{-1.5}\times10^6$ M$_{\odot}$. These are between average masses of local globular clusters and dwarf galaxies. Our analysis suggests middle-aged globulars with relatively recent formation times at z=0.5-0.7, which could have been subsequently stripped away from their host galaxies due to interactions in the cluster environment, or formed in cold flows onto the cluster core. However, we cannot rule out these objects being compact cores of stripped dwarf galaxies.
