Constraints on the Cosmic-Ray Ionization Rate in the $z\sim2.3$ Lensed Galaxies SMM J2135$-$0102 and SDP 17b from Observations of OH$^+$ and H$_2$O$^+$
Nick Indriolo, E. A. Bergin, E. Falgarone, B. Godard, M. A. Zwaan, D. A. Neufeld, M. G. Wolfire
备注：
16 pages, 5 figures, 3 tables, accepted for publication in ApJ
宇宙射线主要在与恒星形成有关的冲击波中加速，如超新星遗迹和恒星风气泡，因此宇宙射线通量和宇宙射线电离率$ζ_{\rm H}$应该与星系中的恒星形成率相关。亚毫米亮星系（SMG）是宇宙中最多产的恒星形成星系，引力透镜SMG提供了适合于吸收线研究的明亮连续光源。当结合化学模型时，OH $^+$和H $_2$ O $^+$的丰度可用于推断$ζ_{\rm H}$，并已在银河系内用于此目的。在红移$z\gtrsim2$过渡出地面旋转状态的OH $^+$和H $_2$ O $^+$是观察与ALMA，我们目前的观察这两个分子的吸收朝向透镜SMG SMM J2135 $-$ 0102和SDP 17 b。这些探测使$ζ_{\rm H}$在极端恒星形成和高超新星率的星系中的探索成为可能，这两者都应该显着增强宇宙射线的产生。观测到的OH $^+$和H $_2$ O $^+$吸收被认为是在这些星系周围的大量、延伸的冷扩散气体晕中产生的。使用的化学模型，旨在专注于重要的两个物种的反应网络，我们推断宇宙射线电离率的$ζ_{\rm H}\sim10^{-16}$ - $10^{-14}$的$^{-1}$在这些扩展的气体晕。由于我们的估计来自远离宇宙射线加速点的气体，它们意味着这些星系中恒星形成的致密区域的宇宙射线电离率要高出几个数量级。
英文摘要：
Cosmic rays are predominantly accelerated in shocks associated with star formation such as supernova remnants and stellar wind bubbles, so the cosmic-ray flux and thus cosmic-ray ionization rate, $ζ_{\rm H}$, should correlate with the star-formation rate in a galaxy. Submillimeter bright galaxies (SMGs) are some of the most prolific star forming galaxies in the Universe, and gravitationally lensed SMGs provide bright continuum sources suitable for absorption line studies. Abundances of OH$^+$ and H$_2$O$^+$ are useful for inferring $ζ_{\rm H}$ when combined with chemical models, and have been used for this purpose within the Milky Way. At redshifts $z\gtrsim2$ transitions out of the ground rotational states of OH$^+$ and H$_2$O$^+$ are observable with ALMA, and we present observations of both molecules in absorption toward the lensed SMGs SMM J2135$-$0102 and SDP 17b. These detections enable an exploration of $ζ_{\rm H}$ in galaxies with extreme star formation and high supernova rates, both of which should significantly enhance cosmic-ray production. The observed OH$^+$ and H$_2$O$^+$ absorption is thought to arise in massive, extended halos of cool, diffuse gas that surround these galaxies. Using a chemical model designed to focus on the reaction network important to both species, we infer cosmic-ray ionization rates of $ζ_{\rm H}\sim10^{-16}$-$10^{-14}$ s$^{-1}$ in these extended gaseous halos. As our estimates come from gas that is far away from the sites of cosmic-ray acceleration, they imply that cosmic-ray ionization rates in the compact regions where star formation occurs in these galaxies are orders of magnitude higher.
Sub-kiloparsec Test of the Kennicutt-Schmidt Relation in a Strongly Lensed Dusty Star-Forming Galaxy at z~2.78
Universidad de Valparaíso（瓦尔帕莱索大学）；Millenium Nucleus for Galaxies (MINGAL)（星系千年核（MINGAL））；STAR Institute（STAR研究所）；Université Côte d’Azur（蔚蓝海岸大学）；University of Florida（佛罗里达大学）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）；Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE)（国家天体物理学、光学和电子学研究所）；Universidad Central de Chile（智利中央大学）
