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arXiv 2101.05321astro-ph.GA
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复合材料凸起-- II。条形Galerkin中的经典隆起和核盘:NGC 4608和NGC 4643的对比

Composite Bulges -- II. Classical Bulges and Nuclear Discs in Barred Galaxies: The Contrasting Cases of NGC 4608 and NGC 4643

Peter Erwin, Anil Seth, Victor P. Debattista, Marja Seidel, Kianusch Mehrgan, Jens Thomas, Roberto Saglia, Adriana de Lorenzo-Cáceres, Witold Maciejewski, Maxim… 展开作者

Peter Erwin, Anil Seth, Victor P. Debattista, Marja Seidel, Kianusch Mehrgan, Jens Thomas, Roberto Saglia, Adriana de Lorenzo-Cáceres, Witold Maciejewski, Maximilian Fabricius, Jairo Méndez-Abreu, Ulrich Hopp, Matthias Kluge, John E. Beckman, Ralf Bender, Niv Drory, Deanne Fisher

摘要:

我们提出了详细的形态,光度和恒星运动学分析的中心区域的两个大规模的,早期型棒星系几乎相同的大尺度形态。两者都有大而坚固的棒,内部光度明显过剩,我们将其与方形/花生形(B/P)凸起联系起来;后者构成了星系光的30%。在它的B/P凸起内,NGC 4608有一个紧凑的,几乎是圆形的结构(半光半径R_e约为1.5米)。310 pc,Sérsic n = 2.2)是一个典型的核球,占总光的12.1%,同时还有一个核星团(R_e ~ 4 pc)。相反,NGC 4643有一个不寻常的破指数表面亮度轮廓(13.2%的光)和一个非常小的球形成分(R_e约为1.2%)的核盘。35 pc,n = 1.6; 0.5%的光)。IFU的恒星运动学支持这一观点,NGC 4608的经典凸起缓慢旋转,并以高速色散为主,而NGC 4643的核盘显示出较低的色散,快速旋转,V-h3的关系,以及升高的h4。这两个星系都显示出至少有一些证据表明,在酒吧(各自的经典凸起和核盘)的V-h3相关,与模型预测一致。两个星系的标准2分量(球/盘)分解产生B/T ~ 0.5-0.7(球n > 2)。这高估了真正的“球状体”成分,分别是NGC 4608和NGC 4643的4倍和100倍以上,说明了将原始的膨胀盘分解应用于大质量棒星系的危险性。

英文摘要:

We present detailed morphological, photometric, and stellar-kinematic analyses of the central regions of two massive, early-type barred galaxies with nearly identical large-scale morphologies. Both have large, strong bars with prominent inner photometric excesses that we associate with boxy/peanut-shaped (B/P) bulges; the latter constitute ~ 30% of the galaxy light. Inside its B/P bulge, NGC 4608 has a compact, almost circular structure (half-light radius R_e approx. 310 pc, Sérsic n = 2.2) we identify as a classical bulge, amounting to 12.1% of the total light, along with a nuclear star cluster (R_e ~ 4 pc). NGC 4643, in contrast, has a nuclear disc with an unusual broken-exponential surface-brightness profile (13.2% of the light), and a very small spheroidal component (R_e approx. 35 pc, n = 1.6; 0.5% of the light). IFU stellar kinematics support this picture, with NGC 4608's classical bulge slowly rotating and dominated by high velocity dispersion, while NGC 4643's nuclear disc shows a drop to lower dispersion, rapid rotation, V-h3 anticorrelation, and elevated h4. Both galaxies show at least some evidence for V-h3 correlation in the bar (outside the respective classical bulge and nuclear disc), in agreement with model predictions. Standard 2-component (bulge/disc) decompositions yield B/T ~ 0.5-0.7 (and bulge n > 2) for both galaxies. This overestimates the true "spheroid" components by factors of four (NGC 4608) and over 100 (NGC 4643), illustrating the perils of naive bulge-disc decompositions applied to massive barred galaxies.

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