scholarly journals Using strong gravitational lensing to probe the post-reionization H i power spectrum

2020 ◽  
Vol 498 (3) ◽  
pp. 3275-3282
Author(s):  
Urvashi Arora ◽  
Prasun Dutta
Keyword(s):  
Power Spectrum ◽  
Gravitational Lensing ◽  
Neutral Hydrogen ◽  
Point Sources ◽  
Dark Matter Halo ◽  
Strong Gravitational Lensing ◽  
The Galaxy ◽  
Formation And Evolution ◽  
The Universe ◽  
Expected Signal

ABSTRACT Probing statistical distribution of the neutral hydrogen (H i) using the redshifted 21-cm hyperfine-transition spectral line holds the key to understand the formation and evolution of the matter density in the Universe. The two-point statistics of the H i distribution can be estimated by measuring the power spectrum of the redshifted 21-cm signal using visibility correlation. A major challenge in this regard is that the expected signal is weak compared to the foreground contribution from the Galactic synchrotron emission and extragalactic point sources in the observing frequencies. In this work, we investigate the possibility of detecting the power spectrum of the redshifted 21-cm signal by using strong gravitational lensing of the galaxy clusters. This method has the advantage that it only enhances the H i signal and not the diffuse Galactic foreground. Based on four simple models of the cluster potentials, we show that the strong lenses at relatively lower redshifts with more than one dark matter halo significantly enhance the 21-cm signal from the post-reionization era. We discuss the merits and demerits of the method and the future studies required for further investigations.

scholarly journals The impact of AGN feedback on galaxy intrinsic alignments in the Horizon simulations

2020 ◽  
Vol 492 (3) ◽  
pp. 4268-4282 ◽  
Author(s):  
Adam Soussana ◽  
Nora Elisa Chisari ◽  
Sandrine Codis ◽  
Ricarda S Beckmann ◽  
Yohan Dubois ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Gravitational Lensing ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Three Dimensions ◽  
High Mass ◽  
Angular Momenta ◽  
The Galaxy ◽  
The Impact ◽  
The Universe

ABSTRACT The intrinsic correlations of galaxy shapes and orientations across the large-scale structure of the Universe are a known contaminant to weak gravitational lensing. They are known to be dependent on galaxy properties, such as their mass and morphologies. The complex interplay between alignments and the physical processes that drive galaxy evolution remains vastly unexplored. We assess the sensitivity of intrinsic alignments (shapes and angular momenta) to active galactic nuclei (AGN) feedback by comparing galaxy alignment in twin runs of the cosmological hydrodynamical Horizon simulation, which do and do not include AGN feedback, respectively. We measure intrinsic alignments in three dimensions and in projection at $z$ = 0 and $z$ = 1. We find that the projected alignment signal of all galaxies with resolved shapes with respect to the density field in the simulation is robust to AGN feedback, thus giving similar predictions for contamination to weak lensing. The relative alignment of galaxy shapes around galaxy positions is however significantly impacted, especially when considering high-mass ellipsoids. Using a sample of galaxy ‘twins’ across simulations, we determine that AGN changes both the galaxy selection and their actual alignments. Finally, we measure the alignments of angular momenta of galaxies with their nearest filament. Overall, these are more significant in the presence of AGN as a result of the higher abundance of massive pressure-supported galaxies.

scholarly journals New Results on DLA Systems: Statistics

2015 ◽  
Vol 11 (S319) ◽  
pp. 40-40
Author(s):  
Sandhya Rao ◽  
David Turnshek ◽  
Eric Monier ◽  
Gendith Sardane
Keyword(s):  
Galaxy Formation ◽  
Mass Density ◽  
Neutral Hydrogen ◽  
Gas Content ◽  
Neutral Gas ◽  
Quasar Spectra ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
Space Data ◽  
The Universe

AbstractThe damped Lyman-α absorption-line systems (DLAs) that are observed in quasar spectra arise in neutral-gas-rich regions of intervening galaxies. With the highest neutral hydrogen column densities observed (N(HI) ⩾ 2 × 1020 atoms cm−2), they are known to trace the bulk of the neutral gas content of the Universe, and are thus powerful probes of galaxy formation and evolution. However, DLAs are extremely rare, and since the Lyman-α line falls in the UV for redshifts z < 1.65, not many are known at low redshift due to the limited availability of space data. Our HST surveys for DLAs in strong MgII absorbers have been successful at showing that MgII can be used as an unbiased tracer of DLAs. We present new results on their incidence, or redshift number density, dn/dz, and cosmological neutral gas mass density, ΩDLA, at redshifts 0.11 ⩽ z ⩽ 1.65, and incorporate results from higher and lower redshift studies in the literature to derive the evolution of neutral gas in the Universe.

Very Metal-Poor Stars and the Early Universe

2017 ◽  
Vol 13 (S334) ◽  
pp. 3-10
Author(s):  
John E. Norris
Keyword(s):  
Near Field ◽  
Field Studies ◽  
Far Field ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Physical Conditions ◽  
The Galaxy ◽  
Formation And Evolution ◽  
The Universe ◽  
Insight Into

AbstractVery metal-poor stars ([Fe/H] &lt; –2.0) inform our understanding of the formation and evolution of the Galaxy, and the physical conditions in the earliest star-forming environments of the Universe. They play an integral part in the paradigms of stellar populations, stellar archaeology, and near-field cosmology. We review the carbon-rich and carbon-normal sub-populations of the most iron-poor stars, providing insight into chemical enrichment at the earliest times in the Universe. We also discuss the role of very metal-poor stars in providing insight into the Galaxy’s halo, thick disk, and bulge, and the promise they hold for the future. A comparison between the abundances obtained for the nine most Fe-poor stars ([Fe/H] &lt; –4.5) (all but one of which is C-rich) with abundances obtained from far-field cosmology suggests that the former are the most chemically primitive objects yet observed and probably older than the DLA- and sub-DLA systems for which data are currently available from far-field studies.

THE LINK BETWEEN GALAXIES AND DARK MATTER

2011 ◽  
Vol 20 (10) ◽  
pp. 1771-1777
Author(s):  
HOUJUN MO
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Luminosity Function ◽  
The Other ◽  
Dark Matter Halos ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Galaxy Halo ◽  
Formation And Evolution ◽  
The Universe

Given that dark matter is gravitationally dominant in the universe, and that galaxy formation is closely related to dark matter halos, a key first step in understanding galaxy formation and evolution in the CDM paradigm is to quantify the galaxy-halo connection for galaxies of different properties. Here I will present results about the halo/galaxy connection obtained from two different methods. One is based on the conditional luminosity function, which describes the occupation of galaxies in halos of different masses, and the other is based on galaxy systems properly selected to represent dark halos.

scholarly journals Generating approximate halo catalogues for blind challenges in precision cosmology

2019 ◽  
Vol 485 (2) ◽  
pp. 2407-2416 ◽  
Author(s):  
Lehman H Garrison ◽  
Daniel J Eisenstein
Keyword(s):  
Dark Matter ◽  
Transfer Function ◽  
Power Spectrum ◽  
High Precision ◽  
Real Space ◽  
Dark Matter Halo ◽  
The Real ◽  
The Galaxy ◽  
Similar Accuracy ◽  
Better Than

ABSTRACT We present a method for generating suites of dark matter halo catalogues with only a few N-body simulations, focusing on making small changes to the underlying cosmology of a simulation with high precision. In the context of blind challenges, this allows us to re-use a simulation by giving it a new cosmology after the original cosmology is revealed. Starting with full N-body realizations of an original cosmology and a target cosmology, we fit a transfer function that displaces haloes in the original so that the galaxy/HOD power spectrum matches that of the target cosmology. This measured transfer function can then be applied to a new realization of the original cosmology to create a new realization of the target cosmology. For a 1 per cent change in σ8, we achieve 0.1 per cent accuracy to $k = 1\, h\, \mathrm{Mpc}^{-1}$ in the real-space power spectrum; this degrades to 0.3 per cent when the transfer function is applied to a new realization. We achieve similar accuracy in the redshift-space monopole and quadrupole. In all cases, the result is better than the sample variance of our $1.1\, h^{-1}\, \mathrm{Gpc}$ simulation boxes.

scholarly journals The first power spectrum limit on the 21-cm signal of neutral hydrogen during the Cosmic Dawn at z = 20–25 from LOFAR

2019 ◽  
Vol 488 (3) ◽  
pp. 4271-4287 ◽  
Author(s):  
B K Gehlot ◽  
F G Mertens ◽  
L V E Koopmans ◽  
M A Brentjens ◽  
S Zaroubi ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Neutral Hydrogen ◽  
Hyperfine Line ◽  
The North ◽  
Upper Limits ◽  
Gain Errors ◽  
The Universe ◽  
Early Phases ◽  
Additional Variance ◽  
Spectrum Limit

ABSTRACT Observations of the redshifted 21-cm hyperfine line of neutral hydrogen from early phases of the Universe such as Cosmic Dawn and the Epoch of Reionization promise to open a new window onto the early formation of stars and galaxies. We present the first upper limits on the power spectrum of redshifted 21-cm brightness temperature fluctuations in the redshift range z = 19.8–25.2 (54–68 MHz frequency range) using 14 h of data obtained with the LOFAR-Low Band Antenna (LBA) array. We also demonstrate the application of a multiple pointing calibration technique to calibrate the LOFAR-LBA dual-pointing observations centred on the North Celestial Pole and the radio galaxy 3C220.3. We observe an unexplained excess of $\sim 30\!-\!50{{\ \rm per\ cent}}$ in Stokes / noise compared to Stokes V for the two observed fields, which decorrelates on ≳12 s and might have a physical origin. We show that enforcing smoothness of gain errors along frequency direction during calibration reduces the additional variance in Stokes I compared Stokes V introduced by the calibration on sub-band level. After subtraction of smooth foregrounds, we achieve a 2σ upper limit on the 21-cm power spectrum of $\Delta _{21}^2 \lt (14561\, \text{mK})^2$ at $k\sim 0.038\, h\, \text{cMpc}^{-1}$ and $\Delta _{21}^2 \lt (14886\, \text{mK})^2$ at $k\sim 0.038 \, h\, \text{cMpc}^{-1}$ for the 3C220 and NCP fields respectively and both upper limits are consistent with each other. The upper limits for the two fields are still dominated by systematics on most k modes.

scholarly journals Measuring the power spectrum of dark matter substructure using strong gravitational lensing

2016 ◽  
Vol 2016 (11) ◽  
pp. 048-048 ◽  
Author(s):  
Yashar Hezaveh ◽  
Neal Dalal ◽  
Gilbert Holder ◽  
Theodore Kisner ◽  
Michael Kuhlen ◽  
...  
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Gravitational Lensing ◽  
Strong Gravitational Lensing

scholarly journals FLUCTUATIONS IN A PRIMORDIAL ANISOTROPIC ERA

1998 ◽  
Vol 13 (03) ◽  
pp. 363-379 ◽  
Author(s):  
MÁRIO NOVELLO ◽  
LUCIANE R. DE FREITAS
Keyword(s):  
Phase Transition ◽  
Power Spectrum ◽  
Galaxy Formation ◽  
Formation Process ◽  
Current Knowledge ◽  
Efficient Process ◽  
Anisotropic Expansion ◽  
The Galaxy ◽  
The Universe ◽  
Fluid Configuration

The primordial Universe is treated in terms of a nonperfect fluid configuration endowed with an anisotropic expansion. The deGennes–Landau mechanism of phase transition acts as a very efficient process to provide the elimination of the previous anisotropy and to set the universe in the current isotropic FRW stage. The entropy produced, as a consequence of the phase transition, depends on the strength of the previous shear. We suggest the hypothesis that the germinal perturbations that will grow into the observed system of galaxies occurring in the anisotropic era. We present a model to deal with this idea that provides a power spectrum of fluctuations of the form [Formula: see text]. We compare this prediction of our model to the current knowledge on the galaxy formation process.

scholarly journals Formation and Evolution of Disk Galaxies

1999 ◽  
Vol 183 ◽  
pp. 153-153
Author(s):  
C. Firmani ◽  
V. Avila-Reese
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Power Spectrum ◽  
Mass Velocity ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Physical Factors ◽  
Disk Galaxies ◽  
Velocity Relation ◽  
Formation And Evolution

We have developed a semianalitical approach to study galaxy formation and evolution in the cosmological context. Disk galaxies (dark matter halo+luminous disk) are considered to be formed through an extended process of gravitational collapse, whose character is determined by the statistical properties of the density fluctuation field assumed here to be Gaussian. Gas disks in centrifugal equilibrium within the collapsing dark halos are built up (detailed angular momentum conservation is assumed), and their galactic evolution is calculated with a model which consider all the gravitational interactions, the hydrodynamics of the ISM, and the SF process. A bulge as product of stellar disk gravitational instabilities is constructed. To study general behaviors a Gaussian σ8 = 1 SCDM model is used. For a given mass one obtains a range of dark matter configurations. The average case is in excellent agreement with results of cosmological N-body simulations. The slope of the mass-velocity relation agrees with the slope of the H- and I-band Tully-Fisher relations, but the velocities are too high. This problem dissapears if the power spectrum is renormalized to σ8 = 0.57, suggesting that the TF relation is result of the natural extension to galactic scales of the galaxy distribution power spectrum, and that on the basis of its origin are the cosmological initial conditions. The scatter on the mass-velocity relation is realistic. The models predict disk exponential surface brightness (SB) profiles, nearly flat rotation curves, and negative radial gradients in the B-V color. The obtained, gas fractions, B-V colors, central SBs μB0, bulge-to-disk (b/d) ratios, and rotation velocities (for σ8 = 0.57) are in agreement with observations, and their correlations are similar to those which define the Hubble sequence, including the LSB galaxies. These properties and correlations are the product of the combination of three fundamental physical factors: the mass, the mass aggregation history (MAH), and the initial angular momentum. The intensive properties are almost invariant to the mass, the MAH determines the B-V color, and the spin parameter λ mainly influences on μB0, and b/d ratio.

Sign in / Sign up

Export Citation Format

Share Document