ZFIRE：使用[ OII ]测量电子密度，作为z = 1.62时环境的函数
ZFIRE: Measuring Electron Density with [OII] as a function of environment at z = 1.62
摘要：
在恒星质量不变的情况下，星系的恒星形成率（SFR）随红移的增加而增加，并随环境的变化而变化。本文通过测量z~2星系团和场星系的[OII]（3727 A/3729 A）比值，探讨恒星形成速率的变化是否也适用于星际介质（ISM）的电子密度。我们在z=1.62的UDS质子团中测量了六个星系的电子密度中值ne = 366+/-84 cm-3（1-sigma散射= 163 cm-3）。我们发现，在UDS光团环境中的星系的电子密度中位数是三倍高的场星系的电子密度中位数（NE = 113+/- 63 cm-3和1-西格玛散射= 79 cm-3）在可比的红移，恒星质量和SFR。然而，我们注意到，六个光团星系的样本是不足以可靠地测量在z~2的平均港团环境中的电子密度。我们得出结论，在z~2（z ~ 0时ne = 30 +/-1cm-3，z~1.5时ne =254+/- 76 cm-3）范围内，电子密度随着红移的增加而增加。我们发现了初步的证据（~2.6西格玛）的电子密度对环境的可能依赖性，但结果需要更大的样本量的确认。
英文摘要：
The global star formation rates (SFR) of galaxies at fixed stellar masses increase with redshift and are known to vary with environment unto z~2. We explore here whether the changes in the star formation rates can also apply to the electron densities of the inter-stellar medium (ISM) by measuring the [OII] (3727A/3729A) ratio for cluster and field galaxies at z~2. We measure a median electron density of ne = 366+/-84 cm-3 for six galaxies (with 1-sigma scatter = 163 cm-3) in the UDS proton-cluster at z=1.62. We find that the median electron density of galaxies in the UDS photo-cluster environment is three times higher compared to the median electron density of field galaxies (ne = 113+/- 63 cm-3 and 1-sigma scatter = 79 cm-3) at comparable redshifts, stellar mass and SFR. However, we note that a sample of six photo-cluster galaxies is insufficient to reliably measure the electron density in the average porto-cluster environment at z~2. We conclude that the electron density increases with redshift in both cluster and field environments up to z~2 (ne = 30 +/- 1 cm-3 for z ~ 0 to ne =254+/- 76 cm-3 for z~1.5). We find tentative evidence (~2.6 sigma ) for a possible dependence of electron density on environment, but the results require confirmation with larger sample sizes.
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