Galaxy properties as revealed by MaNGA – II. Differences in stellar populations of slow and fast rotator ellipticals and dependence on environment
Galaxy properties as revealed by MaNGA – II. Differences in stellar populations of slow and fast rotator ellipticals and dependence on environment
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DOI：
10.1093/mnras/stz2413
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发表时间：
2019-04
影响因子：
4.8
通讯作者：
M. Bernardi;H. D. Sánchez;J. Brownstein;N. Drory;R. Sheth
中科院分区：
文献类型：
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作者：
M. Bernardi;H. D. Sánchez;J. Brownstein;N. Drory;R. Sheth
我们给出了来自MANGA-DR15观测的慢旋转(SR)和快旋转(SR)椭圆星系的堆叠光谱的恒星布居梯度(SP)估计。我们发现：(1)与相同光度Lr和中心速度色散∼0的FR相比，FR年轻了5 Gyr，更富金属，α增强较少，并且小于相同光度的SR和中心速度色散σ0。这就解释了为什么当一个人结合SR和FR时，对于它们的LR和σ0来说较小的对象往往更年轻。它们的SP梯度也不同。(2)忽略FR/SR二分法会导致人们得出结论，即致密星系比同等质量的大星系更古老，尽管FRS和SRS的情况几乎正好相反。(3)具有σ0≤2 5 0 KM S−1的SRS在∼Re中具有显著的均质性：它们是古老的，α增强，仅具有轻微的超极金属性。这些SRS在年龄和M*/LR上没有梯度，在金属丰度上没有梯度，在[α/Fe]上有轻微的正梯度(后者与模型有关)。σ0≥250 KM S−1的SR略年轻，金属含量更丰富，这与之前的工作相反，即年龄随着σ0的增加而增加。它们还显示出更大的M*/LR梯度。(4)自洽地考虑M*/L梯度得到Mdyn≈M*，因为梯度使Mdyn减少0.2dex，而仅略微增加使用∼(而不是Salpeter)初始质量函数所推断的M*。(5)SR种群开始控制大于$M_*\ge 3\×10^{11}\，\mathm{M}_\Oot$的计数；这是大小-质量关联和其他标度关系变化的同一尺度。我们的结果支持这一发现，即这是一个与环境相关的重要质量标度，在此之上，合并是重要的。
We present estimates of stellar population (SP) gradients from stacked spectra of slow rotator (SR) and fast rotator (SR) elliptical galaxies from the MaNGA-DR15 survey. We find that (1) FRs are ∼5 Gyr younger, more metal rich, less α-enhanced and smaller than SRs of the same luminosity Lr and central velocity dispersion σ0. This explains why when one combines SRs and FRs, objects which are small for their Lr and σ0 tend to be younger. Their SP gradients are also different. (2) Ignoring the FR/SR dichotomy leads one to conclude that compact galaxies are older than their larger counterparts of the same mass, even though almost the opposite is true for FRs and SRs individually. (3) SRs with σ0 ≤ 250 km s−1 are remarkably homogeneous within ∼Re: they are old, α-enhanced, and only slightly supersolar in metallicity. These SRs show no gradients in age and M*/Lr, negative gradients in metallicity, and slightly positive gradients in [α/Fe] (the latter are model dependent). SRs with σ0 ≥ 250 km s−1 are slightly younger and more metal rich, contradicting previous work suggesting that age increases with σ0. They also show larger M*/Lr gradients. (4) Self-consistently accounting for M*/L gradients yields Mdyn ≈ M* because gradients reduce Mdyn by ∼0.2 dex while only slightly increasing the M* inferred using a Kroupa (not Salpeter) initial mass function. (5) The SR population starts to dominate the counts above $M_*\ge 3\times 10^{11}\, \mathrm{M}_\odot$; this is the same scale at which the size–mass correlation and other scaling relations change. Our results support the finding that this is an important mass scale that correlates with the environment and above which mergers matter.