EGS场中高红移极亮红外星系的形态与结构

Morphology and Structure of Ultraluminous Infrared Galaxies at z≈2 in the EGS Field

通过利用CANDELS-EGS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey-Extended Groth Strip)场中HST WFC3(Hubble Space Telescope Wide Field Camera 3)F160W高分辨率的观测图像,研究了9个光谱红极亮红外星系的形态结构特征.发现这些星系的形态表现出多样性(从椭圆到多个亮核或弥散的结构),如:双核,气体桥,双不对称体,不规则或椭圆结构.为了定量地研究这些极亮红外星系的形态,测量了它们在静止光学波段的形态参数(基尼系数G和矩指数M20).与近邻极亮红外星系相比,高红移极亮红外星系的G偏小而M20偏大,表明这些星系的星族分布聚集度小且不对称性大.基于对样本中极亮红外星系2维面亮度轮廓的拟合,得到这些星系的有效半径分布在2.4 kpc到5.8 kpc之间,其平均值是(3.9±1.1)kpc.相比较于近邻相似质量的恒星形成星系来说,高红移极亮红外星系的平均大小要小1到2倍.在类似红移和红外光度条件下,得出的这些结果也与其它文献中给出的结论相一致.

Using high-resolution HST WFC3 （Hubble Space Telescope Wide Field Camera 3） F160W imaging from the CANDELS-EGS （Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey-Extended Groth Strip） field, we present the morphology analysis of 9 ultraluminous infrared galaxies （ULIRGs） at z ≈ 2. We find a wide range of morphological diversities for these ULIRGs, from spheroid to multiple bright nuclei or diffuse structures, e.g., double nuclei, bridges, dual asymmetries, irregular, or elliptical structures. In quantitative, these sources show a lower Gini coefficient （G） and a higher moment （M20） in the rest-frame optical morphology, compared to the lower redshift counterparts, indicating less concentrated and symmetric spatial distri- bution of the stellar mass of ULIRGs at z ≈ 2. Moreover, we derive accurate effective radii of these ULIRGs through 2-D profile fitting, which range from 2.4 to 5.8 kpc, with a mean value of （3.9 ± 1.1） kpc. We find that the sizes of these ULIRGs at z ≈ 2 are on average one to two times smaller than those of the local star-forming galaxies with analogous stellar mass. Our results are consistent with those studies at similar redshift and infrared luminosity.