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arXiv 1601.04713astro-ph.GA
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KROSS:绘制z~1恒星形成序列中的Ha辐射

KROSS: Mapping the Ha emission across the star-formation sequence at z~1

Georgios E. Magdis, M. Bureau, J. P. Stott, A. Tiley, A. M. Swinbank, R. Bower, A. J. Bunker, M. Jarvis, H. Johnson, R. Sharples

摘要:

本文介绍了KMOS红移一号光谱巡天(KROSS)的第一批观测结果。KROSS是一项利用VLT KMOS对1000个z~1恒星形成星系进行的大型运动学巡天。在目标星系(~500到目前为止),我们检测和空间分辨哈发射的~90%和77%的样本分别。基于积分的哈流量测量和空间分辨地图,我们得出一个中位数的恒星形成率(SFR)的约7.0 Msun/年和中位数的物理尺寸<r $_{\rm e}$ >= 5.1kpc。我们结合推断的SFR和有效半径的测量,以获得恒星形成表面密度(SFR),并提出了一个“解决”的版本的恒星形成的主要序列(MS),似乎在亚星系尺度,具有类似的斜率和散射的推断从星系综合性能。我们的数据还产生了一个趋势之间的sSFR和Δ(sSFR)(距离MS),这表明具有较高sSFR的星系的特点是密集的恒星形成活动。同样,我们发现了气相金属丰度(Z)和Δ(sSFR)之间存在反相关性的证据,这表明MS内星系的金属含量有0.2dex的变化,而MS以上星系的金属丰度明显较低。可能是由沿着MS和离开MS的星系的气体分数或恒星形成效率的变化之间的相互作用驱动的。为了解决这个问题,有必要对我们的样本进行后续观测,以估计气体质量。

英文摘要:

We present first results from the KMOS Redshift One Spectroscopic Survey (KROSS), an ongoing large kinematical survey of a thousand, z~1 star forming galaxies, with VLT KMOS. Out of the targeted galaxies (~500 so far), we detect and spatially resolve Ha emission in ~90% and 77% of the sample respectively. Based on the integrated Ha flux measurements and the spatially resolved maps we derive a median star formation rate (SFR) of ~7.0 Msun/yr and a median physical size of <r$_{\rm e}$> = 5.1kpc. We combine the inferred SFRs and effective radii measurements to derive the star formation surface densities (ΣSFR) and present a "resolved" version of the star formation main sequence (MS) that appears to hold at sub-galactic scales, with similar slope and scatter as the one inferred from galaxy integrated properties. Our data also yield a trend between ΣSFR and Δ(sSFR) (distance from the MS) suggesting that galaxies with higher sSFR are characterised by denser star formation activity. Similarly, we find evidence for an anti-correlation between the gas phase metallicity (Z) and the Δ(sSFR), suggesting a 0.2dex variation in the metal content of galaxies within the MS and significantly lower metallicities for galaxies above it. The origin of the observed trends between ΣSFR - Σ(sSFR) and Z - Δ(sSFR) could be driven by an interplay between variations of the gas fraction or the star formation efficiency of the galaxies along and off the MS. To address this, follow-up observations of the our sample that will allow gas mass estimates are necessary.

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