论文标题
银河系只是点亮了吗？银河盘最近的恒星形成史
Did the Milky Way just light up? The recent star formation history of the Galactic disc
论文作者
论文摘要
[删节]我们绘制了6kpc $ \，\ times \，$ 6kpc的银河光盘区域的恒星年龄分布（$ \ Lessim 1 $ gyr），以限制我们Galaxy最近的恒星形成历史。我们的建模利用了Zari等人的样品。 （2021）涵盖了所有假定的Disc oba星（$ \ sim 500,000 $），$ g <16 $。要对变红的敏感性较小，我们不会转发这些恒星的详细CMD分布，而是在具有$ M_K <0 $和$ t _ {\ Mathrm {\ Mathrm {eff}}> 7000 $ k的$ m_k <0 $和$ t _k <0 $和$ t _k <0 $和$ n（m_k）$的k波段的绝对幅度分布（m_k）$中$ b（τ〜 |〜\ vec {x}，\vecα）$，年龄从$τ= 5 $ myr到$τ= 1 $ gyr。给定一组等线和KROUPA（2001）初始质量函数，我们采样了$ b（τ\，| \，\ vec {x}，\vecα）$，以最大程度地提高数据的可能性，并考虑了选择功能。这会导致一组跨银河盘的一组恒星密度图。这些地图表明，有些（但不是全部）螺旋臂反映在500 Myr的年轻恒星过度中。最年轻的恒星（$ <10 $ MYR）的地图追踪主要明星形成区域。所有年龄段的地图都表现出外部密度梯度和独特的螺旋状空间结构，在所有年龄间隔中的大尺度上在质量上相似。当将地图的区域求和到整个光盘上时，我们在$ \ 3.3 \ mathrm {m _ {\ odot}/yr} $的最后10个MYR中发现有效的星形成率，高于先前发布的估计值。值得注意的是，我们的出色年龄分布意味着，在最后一个回旋中，恒星形成率降低了三倍，仅在最近的过去才明显增长。
[Abridged] We map the stellar age distribution ($\lesssim 1$ Gyr) across a 6kpc$\,\times\,$6kpc area of the Galactic disc to constrain our Galaxy's recent star-formation history. Our modelling draws on the sample of Zari et al. (2021) that encompasses all presumed disc OBA stars ($\sim 500,000$ sources) with $G<16$. To be less sensitive to reddening, we do not forward model the detailed CMD distribution of these stars, but instead the K-band absolute magnitude distribution, $n(M_K)$, among stars with $M_K<0$ and $T_{\mathrm{eff}} > 7000$K at a certain positions $\vec{x}$ in the disc as a step function with five age bins, $b(τ~|~\vec{x}, \vecα)$, logarithmically-spaced in age from $τ= 5$ Myr to $τ= 1$ Gyr. Given a set of isochrones and a Kroupa (2001) initial mass function, we sample $b(τ\,|\,\vec{x}, \vecα)$ to maximize the likelihood of the data, accounting for the selection function. This results in a set of mono-age stellar density maps across a sizeable portion of the Galactic disc. These maps show that some, but not all, spiral arms are reflected in overdensities of stars younger than 500 Myr. The maps of the youngest stars ($<10$ Myr) trace major star forming regions. The maps at all ages exhibit an outward density gradient and distinct spiral-like spatial structure, which is qualitatively similar on large scales among all age intervals. When summing over the maps' area and extrapolating to the whole disc, we find an effective star-formation rate over the last 10 Myr of $\approx 3.3 \mathrm{M_{\odot}/yr}$, higher than previously published estimates. Remarkably, our stellar age distribution implies that the star-formation rate has been three times lower throughout most of the last Gyr, having risen distinctly only in the very recent past.
