星系结构成分分解星表的比较以及对低表面亮度星系选取的影响

Comparison of Photometric and Morpholgical Decompositions Catalgues

星系面亮度轮廓的成分分解有助于理解星系的形成与演化。已有若干个基于大样本星系图像给出的星系结构成分分解星表,它们在星系结构的统计性质研究上具有重要意义,但由于个体拟合结果相差较大,当选取低表面亮度星系(low surface brightness galaxies, LSBG)进行小样本研究时,会导致较大偏差,因此,研究这些星表结果的异同十分必要。基于Meert等人(M16星表)和Domínguez等人(MPP-VAC星表)发布的星系成分分解星表,对两个星表在单成分拟合及两成分分解的结果进行了比较,得到主要结论如下:对于单成分拟合样本,两个星表各拟合参数的结果比较接近。而对两成分拟合结果进行比较后发现,在早型星系中,除了Sérsic指数,两个星表核球成分拟合结果的一致性略好于盘成分,核球与盘成分的半光半径、面亮度和视星等的平均弥散比分别为0.83, 0.94和0.52;在晚型星系中,两个星表盘成分拟合结果的一致性要显著好于核球成分,核球和盘成分的半光半径、Sérsic指数、面亮度和视星等的平均弥散比分别为4.9, 3, 3和4。而造成两个星表两成分拟合结果差异的主要原因是MPP-VAC星表对因中心像素太亮而影响拟合的星系在拟合时限制了Sérsic指数n的取值范围,使所得成分分解的结果更为合理。依据LSBG的定义,发现晚型星系中LSBG候选体占12%,其中只有1/4的星系被两个星表共同认定为LSBG,而由于拟合结果差异使得剩余3/4的星系仅被一个星表判定为LSBG。

The decomposition of the surface brightness profile of galaxies is helpful to understand the star formation and evolution history of galaxies. There are several catalgues of the photometric and morpholgical decomposition of galaxies based on large samples in the literature, which are of great significance in the study of the statistical properties of galactic structures. However, due to the difference in individual fitting results, selecting certain special types of galaxies for small samples will lead to large deviations. Therefore, it is necessary to compare and understand the similarities and differences of these catalgues.Based on the galactic decomposition catalgues published by Meert et al. and Domínguez et al.(2021, MPP-VAC), there are two sub-samples, i.e., Sérsic and Sérsic + Exponential fits, have been matched. After comparing the fitting results of the two catalgues, the main conclusions are as follows: for single-component fits, the apparent magnitude and axis ratio of the two catalgues are relatively consistent. When comparing the two-component fitting results of the two catalgues, it is found that in the early-type galaxies, in addition to the Sérsic index, the consistency of the fitting results of the bulge component is better than that of the disk component, and the average dispersion ratios of the half-light radius, surface brightness and apparent magnitude of the bulge and disk components are 0.83, 0.94 and 0.52, respectively;However, in late-type galaxies, the consistency of the fitting results of the disk component is significantly better than that of the bulge component, and the average dispersion ratios of the half-light radius, Sérsic index, surface brightness, and apparent magnitude of the bulge and disk components are 4.9, 3, 3 and 4 respectively. The main reason for this difference in the two-component fitting results of the two catalgues is that the MPPVAC catalgue set an upper limit on the Sérsic n if the innermost pixels is too bright and affects the fitting results, making the decomposition results more reasonable. According to the definition of low surface brightness galaxies(LSBGs), 12% of the late-type galaxies are identified as LSBGs candidates, of which only 1/4 of the galaxies were identified as LSBGs by both two catalgues, and due to differences in individual fitting results, the remaining 3/4 of the candidates are identified as LSBGs by only one catalgue.