The Survey for Ionization in Neutral Gas Galaxies. III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation
The Survey for Ionization in Neutral Gas Galaxies. III. Diffuse, Warm Ionized Medium and Escape of Ionizing Radiation
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DOI：
10.1086/517867
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发表时间：
2007-03
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通讯作者：
M. Oey;G. Meurer;S. Yelda;S. Yelda;E. Furst;S. M. Caballero-Nieves;S. M. Caballero-Nieves;D. Hanish;Emily M. Levesque;D. Thilker;G. Walth;J. Bland-Hawthorn;M. Dopita;H. Ferguson;T. Heckman;M. Doyle;M. Drinkwater;Kenneth C. Freeman;R. Kennicutt;V. Kilborn;V. Kilborn;P. Knezek;Baerbel S. Koribalski;Martin Meyer;M. Putman;E. Ryan-Weber;R. C. Smith;L. Staveley-Smith;Rachel L. Webster;J. Werk;M. Zwaan
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作者：
M. Oey;G. Meurer;S. Yelda;S. Yelda;E. Furst;S. M. Caballero-Nieves;S. M. Caballero-Nieves;D. Hanish;Emily M. Levesque;D. Thilker;G. Walth;J. Bland-Hawthorn;M. Dopita;H. Ferguson;T. Heckman;M. Doyle;M. Drinkwater;Kenneth C. Freeman;R. Kennicutt;V. Kilborn;V. Kilborn;P. Knezek;Baerbel S. Koribalski;Martin Meyer;M. Putman;E. Ryan-Weber;R. C. Smith;L. Staveley-Smith;Rachel L. Webster;J. Werk;M. Zwaan
我们使用的第一个数据发布的SINGG Hα调查的H I选定的星系的扩散，温暖的电离介质（WIM）的定量行为的范围内的属性所代表的这109个星系。该样品中弥漫电离气体的平均分数fWIM为0.59 ± 0.19，略高于先前样品中发现的分数。由于较低的表面亮度星系往往有较高的fWIM，我们认为，这种差异大部分是由于选择效应有利于大，光学明亮，附近的星系高星星形成率。正如以前的研究所发现的，与哈勃类型或总星星形成率没有明显的相关性。然而，我们发现，在Hα半光半径范围内，Hα表面亮度大于2.5 × 1039 erg s-1 kpc-2的星暴星系，其弥散Hα辐射的比例要低得多。原因显然不是由较低比例的场OB星所主导的。然而，这是定性一致的电离辐射超过阈值星星形成率，从我们的模型中，ISM被粉碎的压力驱动的超新星反馈预测的预期逃逸。在星暴星系的氢气体分数也较低，这表明星暴正在消耗和电离所有的气体，从而促进区域的密度有界电离。如果属实，这些效应意味着一定量的莱曼连续辐射正在从大多数星暴星系中逸出，并且WIM特性和机械反馈的流出很可能是压力驱动的。然而，鉴于先前的研究表明电离辐射的逃逸分数通常很低，很可能其他因素也驱动了星爆中弥漫电离气体的低分数。
We use the first data release from the SINGG Hα survey of H I-selected galaxies to study the quantitative behavior of the diffuse, warm ionized medium (WIM) across the range of properties represented by these 109 galaxies. The mean fraction fWIM of diffuse ionized gas in this sample is 0.59 ± 0.19, slightly higher than found in previous samples. Since lower surface brightness galaxies tend to have higher fWIM, we believe that most of this difference is due to selection effects favoring large, optically bright, nearby galaxies with high star formation rates. As found in previous studies, there is no appreciable correlation with Hubble type or total star formation rate. However, we find that starburst galaxies, defined here by an Hα surface brightness >2.5 × 1039 erg s-1 kpc-2 within the Hα half-light radius, do show much lower fractions of diffuse Hα emission. The cause apparently is not dominated by a lower fraction of field OB stars. However, it is qualitatively consistent with an expected escape of ionizing radiation above a threshold star formation rate, predicted from our model in which the ISM is shredded by pressure-driven supernova feedback. The H I gas fractions in the starburst galaxies are also lower, suggesting that the starbursts are consuming and ionizing all the gas, and thus promoting regions of density-bounded ionization. If true, these effects imply that some amount of Lyman continuum radiation is escaping from most starburst galaxies, and that WIM properties and outflows from mechanical feedback are likely to be pressure-driven. However, in view of previous studies showing that the escape fraction of ionizing radiation is generally low, it is likely that other factors also drive the low fractions of diffuse ionized gas in starbursts.