A scale-dependent bias on linear scales: the case for H i intensity mapping at z = 1

Pénin, Aurélie; Umeh, Obinna; Santos, Mário G.

doi:10.1093/mnras/stx2635

Cited by 14 publications

(19 citation statements)

References 40 publications

(49 reference statements)

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“…In Section 5, we found that the halo H I mass function, M H I (M, z), from IllustrisTNG can be well reproduced by a fitting formula like - has been widely used (e.g., Bagla et al 2010;Obuljen et al 2017;Villaescusa-Navarro et al 2017;Pénin et al 2018). We have fit our results to that function, and while the reduced χ 2 is larger than that with our fiducial function, it is still a good fit to the underlying data.…”

Section: Appendix E Halo H I Mass Functionmentioning

confidence: 54%

“…A more conventional parameterization of the halo H I mass function falls more slowly for very low halo masses than the standard profile. In order to facilitate the comparison with works using the above parameterization (e.g., Bagla et al 2010;Obuljen et al 2018a;Villaescusa-Navarro et al 2017;Pénin et al 2018), we also provide the best-fit values for the more conventional fit in Appendix E.…”

Section: Halo H I Mass Functionmentioning

confidence: 99%

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Ingredients for 21 cm Intensity Mapping

Villaescusa-Navarro

Genel

Castorina

et al. 2018

ApJ

211

309

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Current and upcoming radio telescopes will map the spatial distribution of cosmic neutral hydrogen (H I) through its 21 cm emission. In order to extract the maximum information from these surveys, accurate theoretical predictions are needed. We study the abundance and clustering properties of H I at redshifts z5 using TNG100, a large state-of-the-art magnetohydrodynamic simulation of a 75h −1 Mpc box size, which is part of the IllustrisTNG Project. We show that most of the H I lies within dark matter halos, and we provide fits for the halo H I mass function, i.e.,the mean H I mass hosted by a halo of mass M at redshift z. We find that only halos with circular velocities larger than ;30km s −1 contain H I. While the density profiles of H I exhibit a large halo-to-halo scatter, the mean profiles are universal across mass and redshift. The H I in low-mass halos is mostly located in the central galaxy, while in massive halos the H I is concentrated in the satellites. Our simulation reproduces the bias value of damped Lyα systems from observations. We show that the H I and matter density probability distribution functions differ significantly. Our results point out that for small halos, the H I bulk velocity goes in the same direction and has the same magnitude as the halo peculiar velocity, while in large halos, differences show up. We find that halo H I velocity dispersion follows a power law with halo mass. We find a complicated H I bias, with H I already becoming nonlinear at k=0.3 h Mpc −1 at z3. The clustering of H I can, however, be accurately reproduced by perturbative methods. We find a new secondary bias by showing that the clustering of halos depends not only on mass but also on H I content. We compute the amplitude of the H I shot noise and find that it is small at all redshifts, verifying the robustness of BAO measurements with 21 cm intensity mapping. We study the clustering of H I in redshift space and show that linear theory can explain the ratio between the monopoles in redshift and real space down to 0.3, 0.5, and 1 h Mpc −1 at redshifts 3, 4, and 5, respectively. We find that the amplitude of the Fingers-of-God effect is larger for H I than for matter, since H I is found only in halos above a certain mass. We point out that 21 cm maps can be created from N-body simulations rather than full hydrodynamic simulations. Modeling the one-halo term is crucial for achieving percent accuracy with respect to a full hydrodynamic treatment. Although our results are not converged against resolution, they are, however, very useful as we work at the resolution where the model parameters have been calibrated to reproduce galaxy properties.

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Section: Appendix E Halo H I Mass Functionmentioning

confidence: 54%

Section: Halo H I Mass Functionmentioning

confidence: 99%

Ingredients for 21 cm Intensity Mapping

Villaescusa-Navarro

Genel

Castorina

et al. 2018

ApJ

211

309

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“…The bias can be measured on simulations simply computing the HI power spectrum (shot noise subtracted) and the matter power spectrum P m (k). On large scales, b HI (k) is expected to be roughly constant, while at small scales it has a more complex behavior (e.g Guha Sarkar et al 2012;Camera et al 2013;Pénin et al 2018). This is shown in figure 12, where the large scale measurements are noisy due to sample variance.…”

Section: Hi Biasmentioning

confidence: 99%

The atomic hydrogen content of the post-reionization Universe

Spinelli

Zoldan

Lucia

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present a comprehensive analysis of atomic hydrogen (HI) properties using a semianalytical model of galaxy formation and N-body simulations covering a large cosmological volume at high resolution. We examine the HI mass function and the HI density, characterizing both their redshift evolution and their dependence on hosting halo mass. We analyze the HI content of dark matter haloes in the local Universe and up to redshift z = 5, discussing the contribution of different galaxy properties. We find that different assembly history plays a crucial role in the scatter of this relation. We propose new fitting functions useful for constructing mock HI maps with HOD techniques. We investigate the HI clustering properties relevant for future 21 cm Intensity Mapping (IM) experiments, including the HI bias and the shot noise level. The HI bias increases with redshift and it is roughly flat on the largest scales probed. The scale dependency is found at progressively larger scales with increasing redshift, apart from a dip feature at z = 0. The shot-noise values are consistent with the ones inferred by independent studies, confirming that shot-noise will not be a limiting factor for IM experiments. We detail the contribution from various galaxy properties on the HI power spectrum and their relation to the halo bias. We find that HI poor satellite galaxies play an important role at the scales of the 1-halo term. Finally, we present the 21 cm signal in redshift space, a fundamental prediction to be tested against data from future radio telescopes such as SKA.

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“…Therefore, considering more realistic models or measurements from numerical simulations is of great importance for robust cosmological analyses. To predict the Hi bias, halo model approach has been considered (Padmanabhan et al 2017;Pénin et al 2018), and several work have been done using pure N-body simulations (Sarkar et al 2016;Sarkar & Bharadwaj 2018). They do not fully solve the radiative transfer but populate the Hi according to the mass of the host dark matter halo.…”

Section: Introductionmentioning

confidence: 99%

Redshift space distortion of 21 cm line at 1 < $z$ < 5 with cosmological hydrodynamic simulations

Ando

Nishizawa

Hasegawa

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We measure the scale dependence and redshift dependence of 21 cm line emitted from the neutral hydrogen gas at redshift 1 < z < 5 using full cosmological hydrodynamic simulations by taking the ratios between the power spectra of Hi-dark matter cross correlation and dark matter auto-correlation. The neutral hydrogen distribution is computed in full cosmological hydrodynamic simulations including star formation and supernova feedback under a uniform ultra-violet background radiation. We find a significant scale dependence of Hi bias at z > 3 on scales of k 1hMpc −1 , but it is roughly constant at lower redshift z < 3. The redshift evolution of Hi bias is relatively slow compared to that of QSOs at similar redshift range. We also measure a redshift space distortion (RSD) of Hi gas to explore the properties of Hi clustering. Fitting to a widely applied theoretical prediction, we find that the constant bias is consistent with that measured directly from the real-space power spectra, and the velocity dispersion is marginally consistent with the linear perturbation prediction. Finally we compare the results obtained from our simulation and the Illustris simulation, and conclude that the detailed astrophysical effects do not affect the scale dependence of Hi bias very much, which implies that the cosmological analysis using 21 cm line of Hi will be robust against the uncertainties arising from small-scale astrophysical processes such as star formation and supernova feedback.

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A scale-dependent bias on linear scales: the case for H i intensity mapping at z = 1

Cited by 14 publications

References 40 publications

Ingredients for 21 cm Intensity Mapping

Ingredients for 21 cm Intensity Mapping

The atomic hydrogen content of the post-reionization Universe

Redshift space distortion of 21 cm line at 1 < $z$ < 5 with cosmological hydrodynamic simulations

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