arXiv 1507.026862015-07astro-ph.GA

预测多$J$ CO线的强度映射信号

Predicting the intensity mapping signal for multi-$J$ CO lines

Natalie Mashian, Amiel Sternberg, Abraham Loeb

备注：: 25 pages, 8 figures; JCAP accepted

摘要：

我们提出了一种新的方法来估计的强度映射信号的任何CO的旋转线在再电离时期（EoR）。我们的方法是基于大速度梯度（LVG）建模，一个辐射转移建模技术，产生完整的CO谱线能量分布（SLED）的指定气体动力学温度，体积密度，速度梯度，分子丰度，和柱密度。这些参数，驱动CO跃迁的物理过程，并最终决定了CO SLED的形状和振幅，可以与宿主星系的整体性质联系起来，主要是恒星形成率（SFR）和SFR表面密度。通过进一步采用经验推导的SFR-M关系高红移星系，我们可以表示LVG参数，从而任何CO旋转过渡的具体强度，作为主机晕质量M和红移z的函数。在可能存在CO发光星系的晕质量范围内进行积分，我们预测CO（1-0）的平均亮温范围为z= 6时的~0.6 μK到z= 10时的~0.03 μ K，亮温涨落分别为$Δ_{CO}^2$ ~ 0.1和0.005 μK，k = 0.1 Mpc $^{-1}$ .在该模型中，对于z = 6的高转动能级，CO发射信号仍然很强，<T $_{CO}$ >CO J = 6->5和CO J = 10->9跃迁的发射信号分别为~ 0.3和0.05 μK。在这些分子云中包括CO光解离的影响，特别是在低金属丰度下，导致CO信号的幅度整体降低，在红移范围4 < z < 10内，低J和高J线分别减弱2-20%和10- 45%。

英文摘要：

We present a novel approach to estimating the intensity mapping signal of any CO rotational line emitted during the Epoch of Reionization (EoR). Our approach is based on large velocity gradient (LVG) modeling, a radiative transfer modeling technique that generates the full CO spectral line energy distribution (SLED) for a specified gas kinetic temperature, volume density, velocity gradient, molecular abundance, and column density. These parameters, which drive the physics of CO transitions and ultimately dictate the shape and amplitude of the CO SLED, can be linked to the global properties of the host galaxy, mainly the star formation rate (SFR) and the SFR surface density. By further employing an empirically derived SFR-M relation for high redshift galaxies, we can express the LVG parameters, and thus the specific intensity of any CO rotational transition, as functions of the host halo mass M and redshift z. Integrating over the range of halo masses expected to host CO-luminous galaxies, we predict a mean CO(1-0) brightness temperature ranging from ~0.6 μK at z= 6 to ~0.03 μ at z= 10 with brightness temperature fluctuations of $Δ_{CO}^2$ ~ 0.1 and 0.005 μK respectively, at k = 0.1 Mpc$^{-1}$. In this model, the CO emission signal remains strong for higher rotational levels at z = 6, with <T$_{CO}$>~ 0.3 and 0.05 μK for the CO J = 6->5 and CO J = 10->9 transitions respectively. Including the effects of CO photodissociation in these molecular clouds, especially at low metallicities, results in the overall reduction in the amplitude of the CO signal, with the low- and high-J lines weakening by 2-20% and 10-45%, respectively, over the redshift range 4 < z < 10.

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