标题： CANDELS-COSMOS场中BzK选择的红移约2星系的形态和结构 显示英文标题

标题： Morphology and structure of BzK-selected galaxies at z~2 in the CANDELS-COSMOS field

摘要： 利用基于 BzK 的选择技术，我们从 COSMOS/UltraVISTA 场的 K 选（K<22.5）目录中获得了 14550 个恒星形成星系（sBzKs）和 1763 个被动星系（pBzKs），红移约为 2。sBzKs 和 pBzKs 的微分数目计数与文献中的结果一致。与观测结果相比，星系形成和演化的半解析模型在高（低）质量端提供的星系数量过少（过多）。此外，我们发现 sBzKs 的恒星形成率（SFR）和恒星质量遵循主序列关系。基于哈勃空间望远镜/宽视场相机 3（WFC3）F160W 成像，我们发现 sBzKs 的形态多样性范围很广，从弥散到早期螺旋结构，具有相对较高的 M20、较大的尺寸和较低的 G 值，而 pBzKs 是椭圆状紧凑形态，具有较低的 M20、较小的尺寸和较高的 G 值，表明 pBzKs 中恒星群体分布的空间集中度和对称性高于 sBzKs。此外，红移约为 2 的 pBzKs（sBzKs）的大小平均比具有相似恒星质量的本地早期型（晚期型）星系小两到三倍（一到两倍）。我们的研究结果表明这两个类别具有不同的演化模式和质量组装历史。 显示英文摘要

摘要： Utilizing a BzK-selected technique, we obtain 14550 star-forming galaxies (sBzKs) and 1763 passive galaxies (pBzKs) at z~2 from the K-selected (K<22.5) catalog in the COSMOS/UltraVISTA field. The differential number counts of sBzKs and pBzKs are consistent with the results from the literature. Compared to the observed results, semi-analytic models of galaxy formation and evolution provide too few (many) galaxies at high (low)-mass end. Moreover, we find that the star formation rate (SFR) and stellar mass of sBzKs follow the relation of main sequence. Based on the HST/Wide Field Camera 3 (WFC3) F160W imaging, we find a wide range of morphological diversities for sBzKs, from diffuse to early-type spiral structures, with relatively high M20, large size and low G, while pBzKs are elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating the more concentrated and symmetric spatial extent of stellar population distribution in pBzKs than sBzKs. Furthermore, the sizes of pBzKs (sBzKs) at z~2 are on average two to three (one to two) times smaller than those of local early-type (late-type) galaxies with similar stellar mass. Our findings imply that the two classes have different evolution modes and mass assembly histories.