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arXiv 2202.09377astro-ph.GA
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在$2\lesssim z \lesssim6$探索透镜状恒星形成团块的物理性质

Exploring the physical properties of lensed star-forming clumps at $2\lesssim z \lesssim6$

U. Meštrić, E. Vanzella, A. Zanella, M. Castellano, F. Calura, P. Rosati, P. Bergamini, A. Mercurio, M. Meneghetti, C. Grillo, G. B. Caminha, M. Nonino, E. Merl… 展开作者

U. Meštrić, E. Vanzella, A. Zanella, M. Castellano, F. Calura, P. Rosati, P. Bergamini, A. Mercurio, M. Meneghetti, C. Grillo, G. B. Caminha, M. Nonino, E. Merlin, G. Cupani, E. Sani

摘要:

我们研究了166个红移为$z \sim 2-6.2$的恒星形成团块的物理性质(大小、恒星质量、光度、恒星形成速率)和标度关系。它们被哈勃前沿场星系团MACS~ J 0416放大,并具有强大的透镜放大率($2\lesssim μ\lesssim 82$),通过使用我们的高精度透镜模型计算,基于182个多图像。我们的样品延伸了$\sim 3$乘以在$z \gtrsim 2$处光谱确认的透镜状团块的数量。我们在紫外线连续图像中识别出团块,并发现每当有效空间分辨率(通过引力透镜增强)增加时,它们就会分裂成更小的实体,这可能反映了恒星形成的分层组织性质。kpc规模的团块,最常见的领域,在我们的样品中没有发现。我们的样品的物理性质扩展了通常由$z \gtrsim 1$现场观测和模拟探测的参数空间,通过填充低质量(M $_\star \lesssim 10^7$ M $_\odot$),低恒星形成率(SFR $\lesssim 0.5$ M $_\odot$ YR $^{-1}$)和小尺寸(R $_\mathrm{eff} \lesssim 100$ pc)制度。我们的研究探索的新领域接近致密恒星复合体和星团的制度。在质量大小平面上,我们的样本跨越了星系和球状星团之间的区域,在年轻星团和球状星团的区域中有一些团块。对于我们的大部分样本,我们测量的恒星形成率高于那些在紧凑的恒星系统中观察到的,表明不同的条件下,恒星形成在高红移比在当地的宇宙。

英文摘要:

We study the physical properties (size, stellar mass, luminosity, star formation rate) and scaling relations for a sample of 166 star-forming clumps with redshift $z \sim 2-6.2$. They are magnified by the Hubble Frontier Field galaxy cluster MACS~J0416 and have robust lensing magnification ($2\lesssim μ\lesssim 82$) computed by using our high-precision lens model, based on 182 multiple images. Our sample extends by $\sim 3$ times the number of spectroscopically-confirmed lensed clumps at $z \gtrsim 2$. We identify clumps in ultraviolet continuum images and find that, whenever the effective spatial resolution (enhanced by gravitational lensing) increases, they fragment into smaller entities, likely reflecting the hierarchically-organized nature of star formation. Kpc-scale clumps, most commonly observed in field, are not found in our sample. The physical properties of our sample extend the parameter space typically probed by $z \gtrsim 1$ field observations and simulations, by populating the low mass (M$_\star \lesssim 10^7$ M$_\odot$), low star formation rate (SFR $\lesssim 0.5$ M$_\odot$ yr$^{-1}$), and small size (R$_\mathrm{eff} \lesssim 100$ pc) regime. The new domain probed by our study approaches the regime of compact stellar complexes and star clusters. In the mass-size plane, our sample spans the region between galaxies and globular clusters, with a few clumps in the region populated by young star clusters and globular-clusters. For the bulk of our sample, we measure star-formation rates which are higher than those observed locally in compact stellar systems, indicating different conditions for star formation at high redshift than in the local Universe.

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