A Self-consistent Framework for Multiline Modeling in Line Intensity Mapping Experiments

Line intensity mapping (LIM) provides a unique and powerful means to probe cosmic structures by measuring the aggregate line emission from all galaxies across redshift. The method is complementary to conventional galaxy redshift surveys that are object-based and demand exquisite point-source sensitivity. The Tomographic Ionized-carbon Mapping Experiment (TIME) will measure the star formation rate (SFR) during cosmic reionization by observing the redshifted [C II] 158 µm line (6 z 9) in the LIM regime. TIME will simultaneously study the abundance of molecular gas during the era of peak star formation by observing the rotational CO lines emitted by galaxies at 0.5 z 2. We present the modeling framework that predicts the constraining power of TIME on a number of observables, including the line luminosity function, and the auto-and cross-correlation power spectra, including synergies with external galaxy tracers. Based on an optimized survey strategy and fiducial model parameters informed by existing observations, we forecast constraints on physical quantities relevant to reionization and galaxy evolution, such as the escape fraction of ionizing photons during reionization, the faint-end slope of the galaxy luminosity function at high redshift, and the cosmic molecular gas density at cosmic noon. We discuss how these constraints can advance our understanding of cosmological galaxy evolution at the two distinct cosmic epochs for TIME, starting in 2021, and how they could be improved in future phases of the experiment.

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“…Similar to the CO case, we use the scaling factors given in Sun et al (2019) to account for the effects of σ C ii on the [C II] power spectrum.…”

Section: Ionized Carbon During the Eormentioning

confidence: 99%

Probing Cosmic Reionization and Molecular Gas Growth with TIME

Sun

Chang

Uzgil

et al. 2021

ApJ

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“…It is essential to have a model that incorporates relevant ISM physics, yet is simple enough that can be efficiently used in theoretical predictions of the line signal and in generating mock intensity maps based on Nbody simulations. In this regard, sophisticated simulations of hydrodynamical galaxy formation and radiative transfer (e.g., [44,105,106]) together with observational data (e.g., cosmic infrared background anisotropies [65], and galaxy UV luminosity functions), provide guidelines for constructing such models.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, we compute the corrections to line Poisson shot noise on large scales, originating from halo exclusion and clustering on small scales using the halo model [62][63][64]. We limit our analysis to real space (neglecting the redshift-space distortions) and consider only the autocorrelations of the CO and [CII] lines, leaving a multi-line study [46,[65][66][67] to future works. While we consider only CO and [CII] lines, the extended halo model we construct applies to other lines emitted from galaxies.…”

Section: Introductionmentioning

confidence: 99%

Precision Tests of CO and [CII] Power Spectra Models against Simulated Intensity Maps

Dizgah,

Nikakhtar,

Keating

et al. 2021

Preprint

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Line intensity mapping (LIM) is an emerging technique with a unique potential to probe a wide range of scales and redshifts. Realizing the full potential of LIM, however, relies on accurate modeling of the signal. We introduce an extended halo model for the power spectrum of intensity fluctuations of CO rotational lines and [CII] fine transition line in real space, modeling nonlinearities in matter fluctuations and biasing relation between the line intensity fluctuations and the underlying dark matter distribution. We also compute the stochastic contributions beyond the Poisson approximation using the halo model framework. To establish the accuracy of the model, we create the first cosmological-scale simulations of CO and [CII] intensity maps, MithraLIMSims, at redshifts 0.5 ≤ z ≤ 6, using halo catalogs from Hidden-Valley simulations, and painting halos according to mass-redshift-luminosity relations for each line. We show that at z = 1 on scales k max 0.8 Mpc −1 h, the model predictions of clustering power (with only two free parameters) are in agreement with the measured power spectrum at better than 5%. At higher redshift of z = 4.5, this remarkable agreement extends to smaller scale of k max 2 Mpc −1 h. Furthermore, we show that on large scales, the stochastic contributions to CO and CII power spectra are non-Poissonian, with amplitudes reproduced reasonably well by the halo model prescription. Lastly, we assess the performance of the theoretical model of the baryon acoustic oscillations (BAO) and show that hypothetical LIM surveys probing CO lines at z = 1, that can be deployed within this decade, will be able to make a high significance measurement of the BAO. On a longer time scale, a space-based mission probing [CII] line can uniquely measure the BAO on a wide range of redshifts at an unprecedented precision.

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“…Importantly, 𝑟 12 also determines the ability to use one line as a tracer of the other, in order to subtract foregrounds/interlopers (Schaan & White 2021), with values near one indicating good subtraction while values near zero indicate ineffective subtraction. Moreover, since the lines considered in this paper all trace slightly different gas phases in the ISM of star-forming galaxies, the correlated abundance of these lines can help constrain the ISM of high-redshift galaxies (Sun et al 2019).…”

Section: Cross-correlation Spectramentioning

confidence: 94%

The THESAN project: predictions for multi-tracer line intensity mapping in the Epoch of Reionization

Kannan,

Smith,

Garaldi

et al. 2021

Preprint

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Line intensity mapping (LIM) is rapidly emerging as a powerful technique to study galaxy formation and cosmology in the highredshift Universe. We present LIM estimates of select spectral lines originating from the interstellar medium (ISM) of galaxies and 21 cm emission from neutral hydrogen gas in the Universe using the large volume, high resolution reionization simulations. A combination of sub-resolution photo-ionization modelling for H regions and Monte Carlo radiative transfer calculations is employed to estimate the dust-attenuated spectral energy distributions (SEDs) of high-redshift galaxies (𝑧 5.5). We show that the derived photometric properties such as the ultraviolet (UV) luminosity function and the UV continuum slopes match observationally inferred values, demonstrating the accuracy of the SED modelling. We provide fits to the luminosity-star formation rate relation (𝐿-SFR) for the brightest emission lines and find that important differences exist between the derived scaling relations and the widely used low-𝑧 ones because the interstellar medium of reionization era galaxies is generally less metal-enriched than in their low redshift counterparts. We use these relations to construct line intensity maps of nebular emission lines and cross correlate with the 21 cm emission. Interestingly, the wavenumber at which the correlation switches sign (𝑘 transition ) depends heavily on the reionization model and to a lesser extent on the targeted emission line, which is consistent with the picture that 𝑘 transition probes the typical sizes of ionized regions. The derived scaling relations and intensity maps represent a timely state-of-the-art framework for forecasting and interpreting results from current and upcoming LIM experiments.

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A Self-consistent Framework for Multiline Modeling in Line Intensity Mapping Experiments

Cited by 55 publications

References 145 publications

Probing Cosmic Reionization and Molecular Gas Growth with TIME

Probing Cosmic Reionization and Molecular Gas Growth with TIME

Precision Tests of CO and [CII] Power Spectra Models against Simulated Intensity Maps

The THESAN project: predictions for multi-tracer line intensity mapping in the Epoch of Reionization

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