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arXiv 1902.01413astro-ph.GA
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$z\sim 6$类星体中高J CO发射线的限制

Constraints on high-J CO emission lines in $z\sim 6$ quasars

S. Carniani, S. Gallerani, L. Vallini, A. Pallottini, M. Tazzari, A. Ferrara, R. Maiolino, C. Cicone, C. Feruglio, R. Neri, V. D'Odorico, R. Wang, J. Li

摘要:

我们提出了阿塔卡马大型毫米波/亚毫米波天线阵(ALMA)观测八个高激发CO两个$z\sim6$类星体的(J $_{\rm up}>8$)谱线和连续辐射:SDSS J231038.88+185519.7(以下简称J2310),其中观察到CO(8-7)、CO(9-8)和CO(17-16)谱线,以及ULAS J131911.29+095951.4(J1319),在CO(14-13)中观察到,CO(17-16)和CO(19-18)线。这两个类星体的连续辐射都来自一个致密的区域($< 0.9$ kpc)。通过假设一个修改后的黑体定律,我们估计日志$(M_{\rm dust}/M_{\odot})=8.75\pm0.07$和日志$(M_{\rm dust}/M_{\odot})=8.8\pm0.2$和$T_{\rm dust}=76\pm3~{\rm K}$和$T_{\rm dust}=66^{+15}_{-10}~{\rm K}$,分别为J2310和J1319的尘埃质量和尘埃温度。只有CO(8-7)和CO(9-8)在J2310中被检测到,而$3σ$的光度上限报告的其他线的两个类星体。J2310和J1319的CO线光度和上限与在本地AGN和星暴星系以及其他$z\sim 6$类星体中观测到的一致,除了SDSS J1148+5251(J1148),它是$z=6.4$上唯一一个先前探测到CO(17-16)线的类星体。通过计算J2310、J1319和J1149的CO SLEDs归一化到CO(6-5)线和FIR光度,我们得出结论,不同的气体加热机制(X射线辐射和/或冲击)可以解释在这些$z\sim6$类星体中观察到的不同CO光度。未来的J $_{\rm up}>8$ CO观测对于理解发光高$_{\rm up}>8$类星体中分子气体激发的过程至关重要。

英文摘要:

We present Atacama Large Millimiter/submillimiter Array (ALMA) observations of eight highly excited CO (J$_{\rm up}>8$) lines and continuum emission in two $z\sim6$ quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO(17-16) lines have been observed, and ULAS J131911.29+095951.4 (J1319), observed in the CO(14-13), CO(17-16) and CO(19-18) lines. The continuum emission of both quasars arises from a compact region ($< 0.9$ kpc). By assuming a modified black-body law, we estimate dust masses of Log$(M_{\rm dust}/M_{\odot})=8.75\pm0.07$ and Log$(M_{\rm dust}/M_{\odot})=8.8\pm0.2$ and dust temperatures of $T_{\rm dust}=76\pm3~{\rm K}$ and $T_{\rm dust}=66^{+15}_{-10}~{\rm K}$, respectively for J2310 and J1319. Only CO(8-7) and CO(9-8) in J2310 are detected, while $3σ$ upper limits on luminosities are reported for the other lines of both quasars. The CO line luminosities and upper limits measured in J2310 and J1319 are consistent with those observed in local AGN and starburst galaxies, and other $z\sim 6$ quasars, except for SDSS J1148+5251 (J1148), the only quasar at $z=6.4$ with a previous CO(17-16) line detection. By computing the CO SLEDs normalised to the CO(6-5) line and FIR luminosities for J2310, J1319, and J1149, we conclude that different gas heating mechanisms (X-ray radiation and/or shocks) may explain the different CO luminosities observed in these $z\sim6$ quasar. Future J$_{\rm up}>8$ CO observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-$z$ quasars.

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