Extended red emission (ERE) has been detected in many dusty astrophysical objects, raising the question of whether ERE is present only in discrete objects or if it is an observational feature of all dust, i.e., present in the diffuse interstellar medium. In order to answer this question, we determined the blue and red intensities of the radiation from the diffuse interstellar medium (ISM) and examined the red intensity for the presence of an excess above that expected for scattered light. The diffuse ISM blue and red intensities were obtained by subtracting the integrated star and galaxy intensities from the blue and red measurements made by the Imaging Photopolarimeters (IPPs) aboard the Pioneer 10 and 11 spacecraft. The unique characteristic of the Pioneer measurements is that they were taken outside the zodiacal dust cloud and, therefore, are free from zodiacal light. The color of the diffuse ISM was found to be redder than the Pioneer intensities. If the diffuse ISM intensities were entirely caused by scattering from dust (i.e., diffuse Galactic light or DGL), the color of the diffuse ISM would be bluer than the Pioneer intensities. Finding a redder color implies the presence of an excess red intensity. Using a model for the DGL, we found the blue diffuse ISM intensity to be entirely attributable to the DGL. The red DGL was calculated using the blue diffuse ISM intensities and the approximately invariant color of the DGL calculated with the DGL model. Subtracting the calculated red DGL from the red diffuse ISM intensities resulted in the detection of an excess red intensity with an average value of ~10 S10(V)G2 V. This represents the likely detection of ERE in the diffuse ISM since Hα emission cannot account for the strength of this excess and the only other known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears to be a general characteristic of dust. The correlation between NH I and ERE intensity is (1.43 ± 0.31) × 10-29 ergs s-1 ?-1 sr-1 H atom-1, from which the ERE photon conversion efficiency was estimated at 10% ± 3%.
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机译：在许多尘土飞扬的天体物体中都检测到了扩展的红色发射（ERE），这引发了一个问题，即ERE是否仅存在于离散的物体中，还是它是所有尘埃的观测特征，即是否存在于星际弥漫性介质中。为了回答这个问题，我们确定了来自星际漫射介质（ISM）的辐射的蓝色和红色强度，并检查了红色强度中是否存在超过散射光预期强度的过量光。扩散ISM的蓝色和红色强度是通过从先锋10号和11号航天器上的成像光偏光计（IPP）进行的蓝色和红色测量中减去积分的星和银河强度而获得的。先锋测量的独特特征是它们是在黄道尘埃云之外拍摄的，因此没有黄道光。发现漫射ISM的颜色比先驱强度更红。如果漫射ISM强度完全是由灰尘（即银河漫射光或DGL）散射引起的，则漫射ISM的颜色会比先锋强度更蓝。找到较红的颜色表示存在过量的红色强度。使用DGL模型，我们发现蓝色漫反射ISM强度完全归因于DGL。使用蓝色漫射ISM强度和使用DGL模型计算出的DGL的近似不变颜色来计算红色DGL。从红色漫射ISM强度中减去计算出的红色DGL，导致检测到多余的红色强度，其平均值约为10 S10（V）G2V。这表示在漫射ISM中可能检测到ERE，因为Hα发射无法解释因为这种过量的强度，并且适用于扩散ISM的唯一其他已知发射过程是ERE。因此，ERE似乎是灰尘的一般特征。 NH I和ERE强度之间的相关性为（1.43±0.31）×10-29 ergs s-1？-1 sr-1 H atom-1，据此估计ERE光子转换效率为10％±3％。
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