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arXiv 1607.07049astro-ph.GA
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来自RAVE数据的局部恒星动力学- VII。红丛星的金属丰度

Local Stellar Kinematics from RAVE data - VII. Metallicity Gradients from Red Clump Stars

O. Onal Tas, S. Bilir, G. M. Seabroke, S. Karaali, S. Ak, T. Ak, Z. F. Bostanci

摘要:

我们调查了银河系的径向和垂直的金属丰度梯度使用的样本47,406红丛星从RAVE DR 4。该样本是研究径向和垂直金属丰度梯度的文献中最大样本的两倍多。Groenewegen(2008)的绝对星等被用来确定到我们样本恒星的距离。由此得到的距离与宾尼等人(2014)对同一颗恒星的RAVE DR 4距离一致。我们的测光方法还提供了6185颗在RAVE DR 4中没有指定距离的恒星的距离。金属丰度梯度是根据它们目前的轨道位置($R_{gc}$和$Z$)和它们的轨道特性(平均银心距、$R_{m}$和$z_{max}$)计算的,作为到银道面距离的函数:$0\leq |Z|\leq0.5$ kpc的d[Fe/H]/d $R_{gc}=$ - $0.047\pm0.003$ dex/kpc,$0\leq z_{max}\leq0.5$ kpc的d[Fe/H]/d $R_m=$ - $0.025\pm0.002$ dex/kpc。这再次证实了薄盘中的径向金属丰度梯度,但强调了梯度对$R_{gc}$和$R_{m}$之间差异引起的选择效应敏感。径向梯度在距平面0.5-1 kpc的距离区间内是平坦的,然后在距平面大于1 kpc时变为正的。径向金属丰度梯度也与偏心率有关。我们表明,在距离间隔$0\leq z_{max}\leq0.5$ kpc中,$e_p\leq0.05$、$e_p\leq0.07$、$e_p\leq0.10$和$e_p\leq0.20$子样品的d[Fe/H]/d $R_m=$-$0.089\pm0.010$、-$0.073\pm0.007$、- $0.053\pm0.004$和- $0.044\pm0.002$ dex/kpc分别为。垂直金属丰度梯度也有类似的趋势。随着样品偏心率的增加,金属丰度的径向和垂直梯度都变浅。这些发现可以用来约束厚盘和薄盘的不同形成方案。

英文摘要:

We investigate the Milky Way Galaxy's radial and vertical metallicity gradients using a sample of 47,406 red clump stars from the RAVE DR4. This sample is more than twice the size of the largest sample in the literature investigating radial and vertical metallicity gradients. The absolute magnitude of Groenewegen (2008) is used to determine distances to our sample stars. The resulting distances agree with the RAVE DR4 distances Binney et al. (2014) of the same stars. Our photometric method also provides distances to 6185 stars that are not assigned a distance in RAVE DR4. The metallicity gradients are calculated with their current orbital positions ($R_{gc}$ and $Z$) and with their orbital properties (mean Galactocentric distance, $R_{m}$ and $z_{max}$), as a function of the distance to the Galactic plane: d[Fe/H]/d$R_{gc}=$-$0.047\pm0.003$ dex/kpc for $0\leq |Z|\leq0.5$ kpc and d[Fe/H]/d$R_m=$-$0.025\pm0.002$ dex/kpc for $0\leq z_{max}\leq0.5$ kpc. This reaffirms the radial metallicity gradient in the thin disc but highlights that gradients are sensitive to the selection effects caused by the difference between $R_{gc}$ and $R_{m}$. The radial gradient is flat in the distance interval 0.5-1 kpc from the plane and then becomes positive greater than 1 kpc from the plane. The radial metallicity gradients are also eccentricity dependent. We showed that d[Fe/H]/d$R_m=$-$0.089\pm0.010$, -$0.073\pm0.007$, -$0.053\pm0.004$ and -$0.044\pm0.002$ dex/kpc for $e_p\leq0.05$, $e_p\leq0.07$, $e_p\leq0.10$ and $e_p\leq0.20$ sub-samples, respectively, in the distance interval $0\leq z_{max}\leq0.5$ kpc. Similar trend is found for vertical metallicity gradients. Both the radial and vertical metallicity gradients are found to become shallower as the eccentricity of the sample increases. These findings can be used to constrain different formation scenarios of the thick and thin discs.

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