论文标题
DESI传统成像调查中低红移星系的颜色梯度
Colour gradients of low-redshift galaxies in the DESI Legacy Imaging Survey
论文作者
论文摘要
星系中的径向颜色梯度是由恒星年龄，金属性和灰尘变红的梯度引起的。大区域成像调查的颜色梯度的大样本可以补充较小的整体场光谱数据集，可用于约束星系形成模型。在这里，我们使用DESI传统成像调查DR9的光度法测量了低红移星系的颜色梯度（z <0.1）。我们的样本包括〜93,000个带有光谱红移的星系，并带有〜574,000个带有光度红移的星系。我们专注于径向范围为0.5 re re的梯度，这对应于低红移时典型的晚期系统的内部磁盘。该区域一直是先前对颜色梯度的统计研究的重点，并且最近通过漫画等光谱调查探索了该区域。我们发现样品中大多数星系的颜色梯度为负（向中心红色），与文献一致。我们研究了颜色梯度，$ g-r $和$ r-z $颜色，$ m_r $，$ m_ \ star $和SSFR之间的经验关系。 $ m_r $（$ m_ \ star $）梯度强度的趋势显示近似$ m_r \ sim-21 $（$ \ log_ {10} \，m_ \ star/\ star/\ mathrm {m_ \ odot} \ sim10.5 $）。在此质量下方，颜色梯度随着$ m_ \ star $的增加而变得陡峭，而更大的星系中的颜色梯度变得更浅。我们发现，对于$ M _ {\ star} \ sim10^{8} {8} \，\ Mathrm {M_ \ odot} $的星系的阳性梯度（较小半径的蓝星）是典型的。我们将我们的结果与两个来自不同恒星种群库的拟合的数据集中的年龄和金属性梯度与漫画光谱进行了比较，但是对于我们观察到的趋势没有明确的共识解释。两个漫画数据集似乎都意味着粉尘变红的重要贡献，特别是解释沿红色序列的颜色梯度的平坦度。
Radial colour gradients within galaxies arise from gradients of stellar age, metallicity and dust reddening. Large samples of colour gradients from wide-area imaging surveys can complement smaller integral-field spectroscopy datasets and can be used to constrain galaxy formation models. Here we measure colour gradients for low-redshift galaxies (z<0.1) using photometry from the DESI Legacy Imaging Survey DR9. Our sample comprises ~93,000 galaxies with spectroscopic redshifts and ~574,000 galaxies with photometric redshifts. We focus on gradients across a radial range 0.5 Re to Re, which corresponds to the inner disk of typical late type systems at low redshift. This region has been the focus of previous statistical studies of colour gradients and has recently been explored by spectroscopic surveys such as MaNGA. We find the colour gradients of most galaxies in our sample are negative (redder towards the centre), consistent with the literature. We investigate empirical relationships between colour gradient, average $g-r$ and $r-z$ colour, $M_r$, $M_\star$, and sSFR. Trends of gradient strength with $M_r$ ($M_\star$) show an inflection around $M_r\sim-21$ ($\log_{10} \, M_\star/\mathrm{M_\odot}\sim10.5$). Below this mass, colour gradients become steeper with increasing $M_\star$, whereas colour gradients in more massive galaxies become shallower. We find that positive gradients (bluer stars at smaller radii) are typical for galaxies of $M_{\star}\sim10^{8}\,\mathrm{M_\odot}$. We compare our results to age and metallicity gradients in two datasets derived from fits of different stellar population libraries to MaNGA spectra, but find no clear consensus explanation for the trends we observe. Both MaNGA datasets seem to imply a significant contribution from dust reddening, in particular, to explain the flatness of colour gradients along the red sequence.
