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arXiv 2302.06629astro-ph.GAastro-ph.CO
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对40个近邻(超)亮红外星系的高灵敏度APEX与ALMA CO(1-0)、CO(2-1)、CO(3-2)及[CI](1-0)光谱巡天

A sensitive APEX and ALMA CO(1-0), CO(2-1), CO(3-2), and [CI](1-0) spectral survey of 40 local (U)LIRGs

I. Montoya Arroyave, C. Cicone, E. Makroleivaditi, A. Weiss, A. Lundgren, P. Severgnini, C. De Breuck, B. Baumschlager, A. Schimek, S. Shen, M. Aravena

AI总结:

本研究利用APEX、ALMA等望远镜对40个近邻(U)LIRGs开展多谱线巡天,揭示其分子气体性质、谱线比值规律及AGN反馈对恒星形成的影响。

摘要:

我们对40个近邻(超)亮红外星系((U)LIRGs)开展了CO(1-0)、CO(2-1)、CO(3-2)和[CI](1-0)的高灵敏度谱线巡天,所有样本均有已有的Herschel OH119 μm观测数据。我们使用了APEX望远镜的单碟观测数据(首席研究员项目数据及存档数据),并辅以ALMA和ACA的数据。我们研究了总辐射,并特别关注延展的低面亮度成分。\n我们发现低J CO与[CI]的谱线光度之间存在紧密相关性,表明至少在星系尺度上取平均时,二者的辐射来自相似区域。我们以[CI]作为独立示踪剂,估算出ULIRGs的CO-to-H₂转换因子中位数为1.7±0.5 M☉(K km s⁻¹ pc²)⁻¹。我们推导得到星系积分的CO谱线比值(r₂₁、r₃₁和r₃₂)以及r_CICO的中位数,均显著高于正常恒星形成星系,证实了ULIRGs独特的分子气体性质。\n我们发现r₂₁和r₃₂并不是ULIRGs中CO激发的良好示踪剂,而r₃₁与红外光度L_IR和恒星形成率(SFR)呈正相关,与H₂气体消耗时标τ_dep呈负相关。在研究CO谱线比值随气体运动学的变化时,我们发现r₂₁与速度弥散σ_v之间存在正相关关系,这可以用CO的光深效应解释。我们发现[CI]谱线的线宽比CO谱线窄约10%,这可能表明[CI]的低光深会增加其在弥散、低面亮度外流中的探测难度,也会影响其作为这些成分中CO暗H₂气体示踪剂的应用。最后,我们发现更高的活动星系核光度L_AGN对应更长的τ_dep,这与活动星系核反馈可能降低恒星形成效率的假说一致。

英文摘要:

We present a high sensitivity spectral line survey of CO(1-0), CO(2-1), CO(3-2) and [CI](1-0) in 40 local (ultra) luminous infrared galaxies ((U)LIRGs), all with previous Herschel OH119 $μ$m observations. We use single-dish observations (PI and archival) conducted with APEX, complemented with ALMA and ACA data. We study the total emission and pay special attention to the extended low-surface brightness components. We find a tight correlation between low-J CO and [CI] line luminosities suggesting their emission arise from similar regions, at least when averaged over galactic scales. We estimate a median CO-to-H$_2$ conversion factor of $1.7\pm 0.5$ M$_{\odot}$ (K km s$^{-1}$ pc$^2)^{-1}$ for ULIRGs, using [CI] as an independent tracer. We derive median galaxy-integrated CO line ratios ($r_{21}$, $r_{31}$ and $r_{32}$), as well as $r_{CICO}$, significantly higher than normal star forming galaxies, confirming the exceptional molecular gas properties of ULIRGs. We find that $r_{21}$ and $r_{32}$ are poor tracers of CO excitation in ULIRGs, while $r_{31}$ shows a positive trend with $L_{IR}$ and SFR, and a negative trend with the H$_2$ gas depletion timescales ($τ_{dep}$). When studying CO line ratios as a function of gas kinematics, we find a positive relation between $r_{21}$ and $σ_v$, which can be explained by CO opacity effects. We find that the linewidths of [CI] lines are ~10% narrower than CO lines, which may suggest that the low optical depth of [CI] can challenge its detection in diffuse, low-surface brightness outflows, and so its use as a tracer of CO-dark H$_2$ gas in these components. Finally, we find that higher $L_{AGN}$ are associated to longer $τ_{dep}$, consistent with the hypothesis that AGN feedback may reduce the efficiency of star formation.

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