arXiv 2306.032302023-06-12astro-ph.GA

基于VIPERS巡天的z~0.7处红核星系的环境

Environments of red nuggets at z~0.7 from the VIPERS survey

M. Siudek, K. Lisiecki, J. Krywult, D. Donevski, C. P. Haines, A. Karska, K. Małek, T. Moutard, A. Pollo

备注：: Accepted for publication in MNRAS, 15 pages, 8 figures, 3 appendices
DOI：: 10.1093/mnras/stad1685

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AI总结：

本研究利用VIPERS巡天数据首次分析中等红移处红核星系的环境特性，发现其占比不随局地密度变化，且遗迹与宁静红核偏好不同环境，提出红核存活至低红移的两种演化途径。

摘要：

被称为“红核（red nuggets）”的红色超致密大质量星系形成于高红移（z~2-3）。在低红移（z<2）处观测到的红核幸存天体（也叫遗迹星系）被认为自形成以来几乎未发生变化。我们首次利用VIMOS河外星系红移巡天（VIPERS）中的42个红色、大质量（log(M_{star}/M_{⊙}) ≥ 10.9）且超致密（R_{e}<1.5 kpc）的星系，验证了中等红移（0.5<z<0.9）处红核的环境特性。我们发现，向更高密度环境移动时红星系占比上升的趋势，是由红色大质量正常尺度星系驱动的。红核与红色中等质量（10.4≲log(M_{star}/M_{⊙})<10.9）超致密星系类似，存在于各类环境中，在所有局地密度下的占比均保持一致（在1σ范围内）。对红核恒星年龄的分析表明，遗迹星系更倾向于出现在高密度区域，而宁静红核在低密度环境中的数量则超出预期。我们推测红核能存活到低红移有两种途径：i）在低密度环境中，由于并合活动（极为）有限，红核的占比随时间推移逐渐降低；ii）在高密度环境中，红核的数量在高红移时因并合活动而减少，而在低红移时由于星系团的高速度阻止了它们被吞噬，数量得以维持。此外，随着宇宙时间推移，红色大质量正常尺度星系被剥离外层包层后加入红核行列，星系团中红核的占比可能还会上升。

英文摘要：

Red ultra-compact massive galaxies, called red nuggets were formed at high redshifts ($\rm{z\sim2-3}$). Survivors of red nuggets, known as relics, observed at lower redshifts ($\rm{z<2}$) are believed to remain almost unchanged since their formation. For the first time, we verify the environmental properties of red nuggets at intermediate redshift ($0.5<\rm{z}<0.9$ ) using 42 red, massive ($\rm{log(M_{star}/M_{\odot}) \geq 10.9}$) and ultra-compact ($\rm{R_{e}}<1.5$ kpc) from the VIMOS Public Extragalactic Redshift Survey (VIPERS). We found that the increasing fraction of red galaxies, when moving to denser environments, is driven by the red massive normal-size galaxies. Red nuggets, similarly to red intermediate-mass ($\rm{10.4\lesssim log(M_{star}/M_{\odot})<10.9}$) ultra-compact galaxies, are found in various types of environments, with consistent (within $1σ$) fractions across all local densities. Analysis of red nugget stellar ages suggests that relics are preferably found in high-density regions while quiescent red nuggets are overabundant in low-density environments. We speculate that red nuggets have survived to lower redshifts via two channels: i) in low-density environments where the fraction of red nuggets decreases as time passes due to (very) limited merger activity, ii) in high-density environments, where the number of red nuggets drops at higher redshift due to merger activity and is preserved at lower redshift as the high velocities of clusters prevent them from being cannibalised. Even more, the fraction of red nuggets in clusters may increase due to the addition of red massive normal-size galaxies deprived of their envelopes with cosmic time.

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