Predicting the intensity mapping signal for multi-J CO lines
Predicting the intensity mapping signal for multi-J CO lines
复制标题
预测多 J CO 线的强度映射信号
DOI：
10.1088/1475-7516/2015/11/028
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发表时间：
2015
影响因子：
6.4
通讯作者：
A. Loeb
中科院分区：
文献类型：
--
作者：
N. Mashian;A. Sternberg;A. Loeb
我们提出了一种新的方法来估计在再电离时代(EOR)期间发射的任何CO旋转线的强度映射信号。我们的方法是基于大速度梯度(LVG)建模，这是一种辐射传输建模技术，可以生成特定气体动力学温度、体积密度、速度梯度、分子丰度和柱密度的完整CO谱线能量分布(SLED)。这些参数驱动了CO跃迁的物理过程，并最终决定了CO SLED的形状和幅度，这些参数可以与宿主星系的整体性质联系在一起，主要是恒星形成率(SFR)和SFR表面密度。通过对高红移星系进一步采用经验推导的Sfr−M关系，我们可以将Lvg参数以及任意CO自转跃迁的比强度表示为宿主晕质量M和红移z的函数。在预期承载共发光星系的晕质量范围内积分，我们预测了在z=6时CO(1-0)的平均亮度温度从∼0.6MPC K到z=10时的Δ0.03MPC K，当k=0.1MPC∼1时，亮度温度的波动分别为0.1MPCμK和0.1MPC−1。在这个模型中，我们预测了当k=0.1MPC MPC 1时，平均CO(1-0)亮温度范围为Δ0.6 MPC K到∼0.0 3MPC K在z=6时，较高转动能级的CO发射信号仍然很强，对于CO J=6 arrow5和CO J=10 arrow9跃迁，⟨TCO⟩∼分别为0.3和0.0 5μK。包括这些分子云中CO光解的影响，特别是在低金属含量时，导致CO信号的幅度总体降低，在红移范围4<；z<；10，低J线和高J线分别减弱2-20%和10-45%。
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 μK at z = 10 with brightness temperature fluctuations of ΔCO2 ∼ 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 ⟨ TCO ⟩ ∼ 0.3 and 0.05 μK for the CO J = 6arrow5 and CO J = 10arrow9 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.