[论文解读] Forecasting the cross correlation of Terahertz Intensity Mapper [CII] line intensity maps with Euclid galaxies

Justin S. Bracks, Ryan P. Keenan+25 more|arXiv (Cornell University)|Feb 27, 2026

Galaxies: Formation, Evolution, Phenomena被引用 0

一句话总结

本文预测 TIM 与 Euclid 的 EDF-F 的时延-交叉相关，以在中位红移约为1.1处以>7σ 检测 [CII]-星系 交叉功率谱，并在四个红shift bin 中实现>3σ 的交叉-shot 噪声检测。

ABSTRACT

We forecast that the Terahertz Intensity Mapper (TIM) cross-correlated with Euclid's Fornax deep field (EDF-F), TIM$ imes$EDF-F, will detect the [CII]-galaxy cross-power spectrum at a median redshift of 1.1 with $\gtrsim 7 σ$ confidence. The Poisson component of the cross-power spectrum at $0.1 \leq k \leq 10$ hMpc$^{-1}$ (i.e. cross-shot noise) will be detected at $\gtrsim 3 σ$ in 4 bins spanning $0.5 < z< 1.7$. This measurement will constrain the mean [CII] specific intensity over half of cosmic history and assess the degree to which Euclid-selected galaxies account for the [CII] intensity observed by TIM. We find that TIM can detect the cross-power spectrum across a wide range of [CII] intensity models.

研究动机与目标

• Motivate the use of line intensity mapping (LIM) for tracing obscured star formation and large-scale structure at z~1.
• Forecast the [CII]-galaxy cross-power spectrum between TIM and Euclid EDF-F.
• Assess the detectability and information gain from cross-correlation versus auto-power spectra.
• Constrain the mean [CII] intensity and its connection to cosmic star formation history across half the cosmic timeline.

提出的方法

• Adopt a line-line cross-spectrum formalism with 2-halo, 1-halo (omitted in fiducial forecast), and shot-noise terms.
• Model the cross-power as P_x = b_CII b_Gal ⟨I_CII⟩ P_M + (f_s ⟨I_CII⟩)/n_Gal, incorporating cross-shot noise.
• Estimate biases b_CII(z) and b_Gal from SimIM and galaxy surveys to anchor the cross-power forecast.
• Compute the matter power spectrum P_M(k,z) using CAMB and apply a linear-bias approximation for the regime k ≲ 1 h Mpc⁻¹.
• Incorporate instrumental noise via NEI, voxel volume, and beam/spectral attenuation to obtain the cross-spectrum variance.

Figure 1: The specific intensity of select FIR line species (left y-axis) versus observed frequency. The dotted lines (using right y-axis) represent the thermal atmospheric background brightness at the ALMA site (dark) and at typical scientific ballooning altitudes (light). The color bar denotes the

实验结果

研究问题

• RQ1 What is the expected cross-power spectrum between TIM [CII] intensity maps and Euclid galaxies across z ~ 0.5–1.7?
• RQ2 What are the detection significances (σ) for the cross-power and cross-shot noise in TIM’s four z-bins?
• RQ3 How does the cross-correlation constrain the mean [CII] intensity ⟨I_[CII]⟩ and the implied star-formation rate density history?
• RQ4 How do instrumental and survey parameters (beam, spectral resolution, NEI, area) affect the cross-spectrum sensitivity and mode sampling?

主要发现

• TIM × EDF-F forecasts yield a >7σ detection of the [CII]-galaxy cross-power at z~1.1.
• The cross-shot component is detectable at ≳3σ in four redshift bins spanning 0.5 < z < 1.7.
• The measurement can constrain the mean [CII] intensity over half the cosmic history and assess the share of [CII] luminosity coming from Euclid-selected galaxies.
• TIM can detect the cross-power across a range of [CII] intensity models, aided by cross-correlation with a spectroscopic galaxy survey.

Figure 2: Top Nominal NEI for the TIM detector focal planes. We present the averaged NEI for TIM’s 4 redshift bins separately in purple, blue, yellow and red, depicting increasing redshift. Gray-filled areas denote the wavelength bands for TIM’s SWA (upward hashed) and LWA (downward hashed). TIM’s b