scholarly journals Beyond ΛCDM with H i intensity mapping: robustness of cosmological constraints in the presence of astrophysics

2020 ◽  
Vol 496 (4) ◽  
pp. 4115-4126 ◽  
Author(s):  
Stefano Camera ◽  
Hamsa Padmanabhan
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Cosmological Parameters ◽  
Neutral Hydrogen ◽  
Temperature Fluctuations ◽  
Dark Matter Halo ◽  
Cosmological Constraints ◽  
Intensity Mapping ◽  
Standard Cosmological Model ◽  
First Time

ABSTRACT Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (H i) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of the standard cosmological model, such as modified gravity and primordial non-Gaussianity, taking self-consistently into account. The present constraints on the astrophysics of H i clustering in the treatment of the brightness temperature fluctuations. To understand the boundaries within which results thus obtained can be considered reliable, we examine the robustness of cosmological parameter estimation performed via studies of 21-cm intensity mapping, against our knowledge of the astrophysical processes leading to H i clustering. Modelling of astrophysical effects affects cosmological observables through the relation linking the overall H i mass in a bound object, to the mass of the underlying dark matter halo that hosts it. We quantify the biases in estimates of standard cosmological parameters and those describing modified gravity and primordial non-Gaussianity that are obtained if one misconceives the slope of the relation between H i mass and halo mass, or the lower virial velocity cut-off for a dark matter halo to be able to host H i. Remarkably, we find that astrophysical uncertainties will not affect searches for primordial non-Gaussianity – one of the strongest science cases for H i intensity mapping – despite the signal being deeply linked to the H i bias.

scholarly journals Intensity mapping as a probe of axion dark matter

2020 ◽  
Vol 500 (3) ◽  
pp. 3162-3177
Author(s):  
Jurek B Bauer ◽  
David J E Marsh ◽  
Renée Hložek ◽  
Hamsa Padmanabhan ◽  
Alex Laguë
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Neutral Hydrogen ◽  
Matrix Formalism ◽  
Intensity Mapping ◽  
Matter Power Spectrum ◽  
Wide Range ◽  
Non Linear ◽  
Order Of Magnitude ◽  
Magnitude Improvement

ABSTRACT We consider intensity mapping (IM) of neutral hydrogen (H i) in the redshift range 0 ≲ z ≲ 3 employing a halo model approach where H i is assumed to follow the distribution of dark matter (DM) haloes. If a portion of the DM is composed of ultralight axions, then the abundance of haloes is changed compared to cold DM below the axion Jeans mass. With fixed total H i density, $\Omega _{\rm H\, \rm {\small I}}$, assumed to reside entirely in haloes, this effect introduces a scale-independent increase in the H i power spectrum on scales above the axion Jeans scale, which our model predicts consistent with N-body simulations. Lighter axions introduce a scale-dependent feature even on linear scales due to its suppression of the matter power spectrum near the Jeans scale. We use the Fisher matrix formalism to forecast the ability of future H i surveys to constrain the axion fraction of DM and marginalize over astrophysical and model uncertainties. We find that a HIRAX-like survey is a very reliable IM survey configuration, being affected minimally by uncertainties due to non-linear scales, while the SKA1MID configuration is the most constraining as it is sensitive to non-linear scales. Including non-linear scales and combining a SKA1MID-like IM survey with the Simons Observatory CMB, the benchmark ‘fuzzy DM’ model with ma = 10−22 eV can be constrained at few per cent. This is almost an order of magnitude improvement over current limits from the Ly α forest. For lighter ULAs, this limit improves below 1 per cent, and allows the possibility to test the connection between axion models and the grand unification scale across a wide range of masses.

scholarly journals Testing dark energy models with a new sample of strong-lensing systems

2020 ◽  
Vol 498 (4) ◽  
pp. 6013-6033
Author(s):  
Mario H Amante ◽  
Juan Magaña ◽  
V Motta ◽  
Miguel A García-Aspeitia ◽  
Tomás Verdugo
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Velocity Dispersion ◽  
Cosmological Parameters ◽  
Cosmic Acceleration ◽  
Dark Matter Halo ◽  
Measured Velocity ◽  
Strong Lensing ◽  
The Impact ◽  
Einstein Radius

ABSTRACT Inspired by a new compilation of strong-lensing systems, which consist of 204 points in the redshift range 0.0625 < zl < 0.958 for the lens and 0.196 < zs < 3.595 for the source, we constrain three models that generate a late cosmic acceleration: the ω-cold dark matter model, the Chevallier–Polarski–Linder, and the Jassal–Bagla–Padmanabhan parametrizations. Our compilation contains only those systems with early-type galaxies acting as lenses, with spectroscopically measured stellar velocity dispersions, estimated Einstein radius, and both the lens and source redshifts. We assume an axially symmetric mass distribution in the lens equation, using a correction to alleviate differences between the measured velocity dispersion (σ) and the dark matter halo velocity dispersion (σDM) as well as other systematic errors that may affect the measurements. We have considered different subsamples to constrain the cosmological parameters of each model. Additionally, we generate a mock data of SLS to asses the impact of the chosen mass profile on the accuracy of Einstein radius estimation. Our results show that cosmological constraints are very sensitive to the selected data: Some cases show convergence problems in the estimation of cosmological parameters (e.g. systems with observed distance ratio Dobs < 0.5), others show high values for the χ2 function (e.g. systems with a lens equation Dobs > 1 or high velocity dispersion σ > 276 km s−1). However, we obtained a fiduciary sample with 143 systems, which improves the constraints on each tested cosmological model.

scholarly journals Modelling the post-reionization neutral hydrogen (H i) 21-cm bispectrum

2019 ◽  
Vol 490 (2) ◽  
pp. 2880-2889 ◽  
Author(s):  
Debanjan Sarkar ◽  
Suman Majumdar ◽  
Somnath Bharadwaj
Keyword(s):  
Perturbation Theory ◽  
Power Spectrum ◽  
Cosmological Parameters ◽  
Neutral Hydrogen ◽  
Order Perturbation ◽  
Order Perturbation Theory ◽  
Intensity Mapping ◽  
High Level ◽  
Second Order Perturbation Theory ◽  
Good Agreement

ABSTRACT Measurements of the post-reionization 21-cm bispectrum $B_{{\rm H\,{\small I}}\, }(\boldsymbol {k_1},\boldsymbol {k_2},\boldsymbol {k_3})$ using various upcoming intensity mapping experiments hold the potential for determining the cosmological parameters at a high level of precision. In this paper, we have estimated the 21-cm bispectrum in the z range 1 ≤ z ≤ 6 using seminumerical simulations of the neutral hydrogen (H i) distribution. We determine the k and z range where the 21-cm bispectrum can be adequately modelled using the predictions of second-order perturbation theory, and we use this to predict the redshift evolution of the linear and quadratic H i bias parameters b1 and b2, respectively. The b1 values are found to decrease nearly linearly with decreasing z, and are in good agreement with earlier predictions obtained by modelling the 21-cm power spectrum $P_{{\rm H\,{\small I}}\, }(k)$. The b2 values fall sharply with decreasing z, becomes zero at z ∼ 3 and attains a nearly constant value b2 ≈ −0.36 at z < 2. We provide polynomial fitting formulas for b1 and b2 as functions of z. The modelling presented here is expected to be useful in future efforts to determine cosmological parameters and constrain primordial non-Gaussianity using the 21-cm bispectrum.

scholarly journals Detecting ultralight axion dark matter wind with laser interferometers

2016 ◽  
Vol 26 (07) ◽  
pp. 1750063 ◽  
Author(s):  
Arata Aoki ◽  
Jiro Soda
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Modified Gravity ◽  
Laser Interferometer ◽  
Mass Range ◽  
Dark Matter Halo ◽  
Detector Signal ◽  
Modified Gravity Theory ◽  
Axion Field ◽  
Laser Interferometers

The ultralight axion with mass around [Formula: see text][Formula: see text]eV is known as a candidate of dark matter. A peculiar feature of the ultralight axion is oscillating pressure in time, which produces oscillation of gravitational potentials. Since the solar system moves through the dark matter halo at the velocity of about [Formula: see text], there exists axion wind, which looks like scalar gravitational waves for us. Hence, there is a chance to detect ultralight axion dark matter with a wide mass range by using laser interferometer detectors. We calculate the detector signal induced by the oscillating pressure of the ultralight axion field, which would be detected by future laser interferometer experiments. We also argue that the detector signal can be enhanced due to the resonance in modified gravity theory explaining the dark energy.

scholarly journals Detection of a slow H i bar in the dwarf irregular galaxy DDO 168

2019 ◽  
Vol 488 (4) ◽  
pp. 4942-4951
Author(s):  
Narendra Nath Patra ◽  
Chanda J Jog
Keyword(s):  
Dark Matter ◽  
Time Scale ◽  
Dark Matter Halo ◽  
Irregular Galaxy ◽  
Stringent Constraint ◽  
Dynamical Time ◽  
Dimensionless Ratio ◽  
Pattern Speed ◽  
Pattern Speeds ◽  
First Time

Abstract We examine the H i total intensity maps of the VLA LITTLE-THINGS galaxies and identify an H i bar in the dwarf irregular galaxy DDO 168 which has a dense and compact dark matter halo that dominates at all radii. This is only the third galaxy found to host an H i bar. Using the H i kinematic data, we apply the Tremaine–Weinberg method to estimate the pattern speed of the bar. The H i bar is found to have an average pattern speed of 23.3 ± 5.9 $\rm km \, s^{-1} \, kpc^{-1}$. Interestingly, for the first time, we find that the observed pattern speeds of the bar in the two kinematic halves are different. We identify the origin of this difference to be the kinematic asymmetry. This observed offset in the pattern speed serves to put a stringent constraint on the lifetime of the bar set by the winding time-scale. The lifetime of the bar is found to be 5.3 × 108 yr, which is two times the dynamical time-scale of the disc. We also find the H i bar in DDO 168 to be a weak bar with a strength of 0.2. If H i bar being weak can be easily disturbed, this could possibly explain why it is extremely rare to observe H i bars in galaxies. We estimate the bar radius to be 1 kpc and the dimensionless ratio, RL/Rb to be ≥2.1 indicating a ‘slow’ bar in DDO 168. Our results confirm the proposition that the dynamical friction with the halo slows down a rotating bar in a galaxy dominated by dark matter halo from inner radii.

scholarly journals Mild Velocity Dispersion Evolution of massive galaxies since z~2

2009 ◽  
Vol 5 (S262) ◽  
pp. 184-187
Author(s):  
Ignacio Trujillo ◽  
A. Javier Cenarro
Keyword(s):  
Dark Matter ◽  
Velocity Dispersion ◽  
Cosmic Time ◽  
Stellar Mass ◽  
Dark Matter Halo ◽  
Massive Galaxies ◽  
Strong Change ◽  
First Time ◽  
Lower Redshift

AbstractMaking use of public spectra from Cimatti et al. (2008), we measure for the first time the velocity dispersion of spheroid-like massive (M* ~ 1011M⊙) galaxies at z ~ 1.6. By comparing with galaxies of similar stellar mass at lower redshifts, we find evidence for a mild evolution in velocity dispersion, decreasing from ~240 kms−1 at z ~ 1.6 down to ~180 km s−1 at z ~ 0. Such mild evolution contrasts with the strong change in size (a factor of ~4) found for these type of objects in the same cosmic time, and it is consistent with a progressive larger role, at lower redshift, of the dark matter halo in setting the velocity dispersion of these galaxies. We discuss the implications of our results within the context of different scenarios proposed for the evolution of these massive objects.

scholarly journals Towards accurate rescaling of a halo mass function

2018 ◽  
Vol 27 (1) ◽  
pp. 150-156
Author(s):  
Victoria Yankelevich ◽  
Sergey V. Pilipenko
Keyword(s):  
Dark Matter ◽  
Cosmological Parameters ◽  
Mass Function ◽  
Dark Matter Halo ◽  
The Difference ◽  
The One

Abstract We investigate the precision within which a simulated dark matter halo mass function can be rescaled to a different set of cosmological parameters. Our tests show that the accuracy almost linearly depends on the difference of the cosmological parameters and amounts to few percent in the case of WMAP5 and PLANCK parameters. The rescaling thus allows us to obtain a mass function with better precision than the one given by the Sheth-Mo-Tormen approximation and even more modern fits currently used in the literature.

scholarly journals Dark matter halo sparsity of modified gravity scenarios

2020 ◽  
Vol 102 (4) ◽  
Author(s):  
Pier Stefano Corasaniti ◽  
Carlo Giocoli ◽  
Marco Baldi
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Dark Matter Halo

scholarly journals Searching for H i imprints in cosmic web filaments with 21-cm intensity mapping

2019 ◽  
Vol 489 (1) ◽  
pp. 385-400 ◽  
Author(s):  
Denis Tramonte ◽  
Yin-Zhe Ma ◽  
Yi-Chao Li ◽  
Lister Staveley-Smith
Keyword(s):  
Principal Component Analysis ◽  
Confidence Level ◽  
Column Density ◽  
Neutral Hydrogen ◽  
Principal Component ◽  
Density Parameter ◽  
Common Reference ◽  
Intensity Mapping ◽  
Upper Limits ◽  
First Time

ABSTRACT We investigate the possible presence of neutral hydrogen (H i) in intergalactic filaments at very low redshift (z ∼ 0.08), by stacking a set of 274 712 2dFGRS galaxy pairs over 21-cm maps obtained with dedicated observations conducted with the Parkes radio telescope, over a total sky area of approximately 1300 deg2 covering two patches in the northern and in the southern Galactic hemispheres. The stacking is performed by combining local maps in which each pair is brought to a common reference frame; the resulting signal from the edge galaxies is then removed to extract the filament residual emission. We repeat the analysis on maps cleaned removing either 10 or 20 foreground modes in a principal component analysis. Our study does not reveal any clear H i excess in the considered filaments in either case; we determine upper limits on the total filament H i brightness temperature at $T_{\rm b} \lesssim 10.3 \, \mu \text{K}$ for the 10-mode and at $T_{\rm b} \lesssim 4.8 \, \mu \text{K}$ for the 20-mode removed maps at the 95 per cent confidence level. These estimates translate into upper limits for the local filament H i density parameter, $\Omega _{\rm HI}^{\rm (f)} \lesssim 7.0\times 10^{-5}$ and $\Omega _{\rm HI}^{\rm (f)} \lesssim 3.2\times 10^{-5}$, respectively, and for the H i column density, $N_{\rm HI} \lesssim 4.6\times 10^{15}\, \text{cm}^{-2}$ and $N_{\rm HI} \lesssim 2.1\times 10^{15}\, \text{cm}^{-2}$, respectively. These column density constraints are consistent with previous detections of H i in the warm-hot intergalactic medium obtained observing broad Ly α absorption systems. This work shows for the first time how such constraints can be achieved using the stacking of galaxy pairs on 21-cm maps.

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