scholarly journals Collaborative Research: Large Scale Intensity Mapping of Neutral Hydrogen with the Tianlai Pathfinders

2021 ◽  
Author(s):  
◽  
Keyword(s):  
Collaborative Research ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Intensity Mapping

scholarly journals Neutral hydrogen in the post-reionization universe

2017 ◽  
Vol 12 (S333) ◽  
pp. 216-221
Author(s):  
Hamsa Padmanabhan
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Lyman Alpha ◽  
Intensity Mapping ◽  
Best Fitting ◽  
Hydrodynamical Simulations ◽  
Intermediate Redshift ◽  
Intermediate Redshifts ◽  
The Universe

AbstractThe evolution of neutral hydrogen (HI) across redshifts is a powerful probe of cosmology, large scale structure in the universe and the intergalactic medium. Using a data-driven halo model to describe the distribution of HI in the post-reionization universe (z ∼ 5 to 0), we obtain the best-fitting parameters from a rich sample of observational data: low redshift 21-cm emission line studies, intermediate redshift intensity mapping experiments, and higher redshift Damped Lyman Alpha (DLA) observations. Our model describes the abundance and clustering of neutral hydrogen across redshifts 0 - 5, and is useful for investigating different aspects of galaxy evolution and for comparison with hydrodynamical simulations. The framework can be applied for forecasting future observations with neutral hydrogen, and extended to the case of intensity mapping with molecular and other line transitions at intermediate redshifts.

scholarly journals The neutral hydrogen distribution in large-scale haloes from 21-cm intensity maps

2020 ◽  
Vol 498 (4) ◽  
pp. 5916-5935
Author(s):  
Denis Tramonte ◽  
Yin-Zhe Ma
Keyword(s):  
Large Scale ◽  
Neutral Hydrogen ◽  
Principal Component ◽  
Theoretical Models ◽  
Mapping Data ◽  
Hydrogen Distribution ◽  
Intensity Mapping ◽  
Concentration Parameter ◽  
Functional Forms ◽  
First Time

ABSTRACT We detect the neutral hydrogen (H i) radial brightness temperature profile in large-scale haloes by stacking 48 430 galaxies selected from the 2dFGRS catalogue on to a set of 21-cm intensity maps obtained with the Parkes radio telescope, spanning a total area of ∼1300 deg2 on the sky and covering the redshift range 0.06 ≲ z ≲ 0.10. Maps are obtained by removing both 10 and 20 foreground modes in the principal component analysis. We perform the stack at the map level and extract the profile from a circularly symmetrized version of the halo emission. We detect the H i halo emission with the significance 12.5σ for the 10-mode and 13.5σ for the 20-mode removed maps at the profile peak. We jointly fit for the observed halo mass Mv and the normalization $c_{0,\rm H\, \small{I}}$ for the H i concentration parameter against the reconstructed profiles, using functional forms for the H i halo abundance proposed in the literature. We find $\log _{10}{(M_{\rm v}/\text{M}_{\odot })}= 16.1^{+0.1}_{-0.2}$, $c_{0,\rm H\, \small{I}}=3.5^{+0.7}_{-1.0}$ for the 10-mode and $\log _{10}{(M_{\rm v}/\text{M}_{\odot })}= 16.5^{+0.1}_{-0.2}$, $c_{0,\rm H\, \small{I}}=5.3^{+1.1}_{-1.7}$ for the 20-mode removed maps. These estimates show the detection of the integrated contribution from multiple galaxies located inside very massive haloes. We also consider subsamples of 13 979 central and 34 361 satellite 2dF galaxies separately, and obtain marginal differences suggesting satellite galaxies are H i-richer. This work shows for the first time the feasibility of testing theoretical models for the H i halo content directly on profiles extracted from 21-cm maps and opens future possibilities for exploiting upcoming H i intensity-mapping data.

scholarly journals HIR4: cosmology from a simulated neutral hydrogen full sky using Horizon Run 4

2020 ◽  
Vol 495 (2) ◽  
pp. 1788-1806
Author(s):  
Jacobo Asorey ◽  
David Parkinson ◽  
Feng Shi ◽  
Yong-Seon Song ◽  
Kyungjin Ahn ◽  
...  
Keyword(s):  
Large Scale ◽  
Cosmological Parameters ◽  
Line Emission ◽  
Neutral Hydrogen ◽  
Angular Power Spectrum ◽  
Intensity Mapping ◽  
Free Case ◽  
Foreground Removal ◽  
The Universe ◽  
Mapping Information

ABSTRACT The distribution of cosmological neutral hydrogen will provide a new window into the large-scale structure of the Universe with the next generation of radio telescopes and surveys. The observation of this material, through 21 cm line emission, will be confused by foreground emission in the same frequencies. Even after these foregrounds are removed, the reconstructed map may not exactly match the original cosmological signal, which will introduce systematic errors and offset into the measured correlations. In this paper, we simulate future surveys of neutral hydrogen using the Horizon Run 4 (HR4) cosmological N-body simulation. We generate H i intensity maps from the HR4 halo catalogue, and combine with foreground radio emission maps from the Global Sky Model, to create accurate simulations over the entire sky. We simulate the H i sky for the frequency range 700–800 MHz, matching the sensitivity of the Tianlai pathfinder. We test the accuracy of the fastICA, PCA, and log-polynomial fitting foreground removal methods to recover the input cosmological angular power spectrum and measure the parameters. We show the effect of survey noise levels and beam sizes on the recovered the cosmological constraints. We find that while the reconstruction removes power from the cosmological 21 cm distribution on large scales, we can correct for this and recover the input parameters in the noise-free case. However, the effect of noise and beam size of the Tianlai pathfinder prevents accurate recovery of the cosmological parameters when using only intensity mapping information.

scholarly journals Measuring ultralarge scale effects in the presence of 21 cm intensity mapping foregrounds

2021 ◽  
Vol 504 (1) ◽  
pp. 267-279
Author(s):  
José Fonseca ◽  
Michele Liguori
Keyword(s):  
High Precision ◽  
Large Scale ◽  
Scale Effects ◽  
Cosmological Parameters ◽  
Neutral Hydrogen ◽  
Joint Analysis ◽  
Forward Modelling ◽  
Intensity Mapping ◽  
Best Fitting ◽  
The Universe

ABSTRACT H i intensity mapping will provide maps of the large-scale distribution of neutral hydrogen (H i) in the universe. These are prime candidates to be used to constrain primordial non-Gaussianity using the large-scale structure of the Universe as well as to provide further tests of Einstein’s theory of Gravity (GR). But H i maps are contaminated by foregrounds, which can be several orders of magnitude above the cosmological signal. Here we quantify how degenerated are the large-scale effects (fNL and GR effects) with the residual foregrounds. We conclude that a joint analysis does not provide a catastrophic degradation of constraints and provides a framework to determine the marginal errors of large scale-effects in the presence of foregrounds. Similarly, we conclude that the macroscopical properties of the foregrounds can be measured with high precision. Notwithstanding, such results are highly dependent on accurate forward modelling of the foregrounds, which incorrectly done catastrophically bias the best-fitting values of cosmological parameters, foreground parametrizations, and large-scale effects.

scholarly journals Extracting H i astrophysics from interferometric Intensity Mapping

2021 ◽  
Author(s):  
Zhaoting Chen ◽  
Laura Wolz ◽  
Marta Spinelli ◽  
Steven G Murray
Keyword(s):  
Galaxy Formation ◽  
Shot Noise ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Mass Function ◽  
Small Scale ◽  
Number Density ◽  
Model Framework ◽  
Intensity Mapping ◽  
Cent Level

Abstract We present a new halo model of neutral hydrogen (H i) calibrated to galaxy formation simulations at redshifts z ∼ 0.1 and z ∼ 1.0 which we employ to investigate the constraining power of interferometric H i Intensity Mapping on H i astrophysics. We demonstrate that constraints on the small-scale H i power spectrum can break the degeneracy between the H i density $\Omega _{\rm H\, \rm \small {I}}$ and the H i bias $b_{\rm H\, \rm \small {I}}$. For z ∼ 0.1, we forecast that an accurate measurement of $\Omega _{\rm H\, \rm \small {I}}$ up to 6 per cent level precision and the large scale H i bias $b_{\rm H\, \rm \small {I}}^0$ up to 1 per cent level precision can be achieved using Square Kilometre Array (SKA) pathfinder data from MeerKAT and ASKAP. We also propose a new description of the H i shot noise in the halo model framework in which a scatter of the relation between the H i mass of galaxies and their host halo mass is taken into account. Furthermore, given the number density of H i galaxies above a certain H i mass threshold, future surveys will also be able to constrain the H i Mass Function using only the H i shot noise. This will lead to constraints at the 10 per cent level using the standard Schechter function. This technique will potentially provide a new way of measuring the H i Mass Function, independent from existing methods. We predict that the SKA will be able to further improve the low redshift constraints by a factor of three, as well as pioneering measurements of H i astrophysics at higher redshifts.

scholarly journals The degeneracy between primordial non-Gaussianity and foregrounds in 21 cm intensity mapping experiments

2020 ◽  
Vol 499 (3) ◽  
pp. 4054-4067
Author(s):  
Steven Cunnington ◽  
Stefano Camera ◽  
Alkistis Pourtsidou
Keyword(s):  
Nuisance Parameter ◽  
Neutral Hydrogen ◽  
Real Data ◽  
Line Of Sight ◽  
Markov Chain Analysis ◽  
Significant Progress ◽  
Intensity Mapping ◽  
Chain Analysis ◽  
Parallel Text ◽  
Foreground Removal

ABSTRACT Potential evidence for primordial non-Gaussianity (PNG) is expected to lie in the largest scales mapped by cosmological surveys. Forthcoming 21 cm intensity mapping experiments will aim to probe these scales by surveying neutral hydrogen (H i) within galaxies. However, foreground signals dominate the 21 cm emission, meaning foreground cleaning is required to recover the cosmological signal. The effect this has is to damp the H i power spectrum on the largest scales, especially along the line of sight. Whilst there is agreement that this contamination is potentially problematic for probing PNG, it is yet to be fully explored and quantified. In this work, we carry out the first forecasts on fNL that incorporate simulated foreground maps that are removed using techniques employed in real data. Using an Monte Carlo Markov Chain analysis on an SKA1-MID-like survey, we demonstrate that foreground cleaned data recovers biased values [$f_{\rm NL}= -102.1_{-7.96}^{+8.39}$ (68 per cent CL)] on our fNL = 0 fiducial input. Introducing a model with fixed parameters for the foreground contamination allows us to recover unbiased results ($f_{\rm NL}= -2.94_{-11.9}^{+11.4}$). However, it is not clear that we will have sufficient understanding of foreground contamination to allow for such rigid models. Treating the main parameter $k_\parallel ^\text{FG}$ in our foreground model as a nuisance parameter and marginalizing over it, still recovers unbiased results but at the expense of larger errors ($f_{\rm NL}= 0.75^{+40.2}_{-44.5}$), which can only be reduced by imposing the Planck 2018 prior. Our results show that significant progress on understanding and controlling foreground removal effects is necessary for studying PNG with H i intensity mapping.

scholarly journals Mapping large-scale-structure evolution over cosmic times

2021 ◽  
Author(s):  
Marta B. Silva ◽  
Ely D. Kovetz ◽  
Garrett K. Keating ◽  
Azadeh Moradinezhad Dizgah ◽  
Matthieu Bethermin ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
High Redshift ◽  
Formation Rate ◽  
Far Infrared ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Structure Evolution ◽  
Intensity Mapping ◽  
Wide Range

AbstractThis paper outlines the science case for line-intensity mapping with a space-borne instrument targeting the sub-millimeter (microwaves) to the far-infrared (FIR) wavelength range. Our goal is to observe and characterize the large-scale structure in the Universe from present times to the high redshift Epoch of Reionization. This is essential to constrain the cosmology of our Universe and form a better understanding of various mechanisms that drive galaxy formation and evolution. The proposed frequency range would make it possible to probe important metal cooling lines such as [CII] up to very high redshift as well as a large number of rotational lines of the CO molecule. These can be used to trace molecular gas and dust evolution and constrain the buildup in both the cosmic star formation rate density and the cosmic infrared background (CIB). Moreover, surveys at the highest frequencies will detect FIR lines which are used as diagnostics of galaxies and AGN. Tomography of these lines over a wide redshift range will enable invaluable measurements of the cosmic expansion history at epochs inaccessible to other methods, competitive constraints on the parameters of the standard model of cosmology, and numerous tests of dark matter, dark energy, modified gravity and inflation. To reach these goals, large-scale structure must be mapped over a wide range in frequency to trace its time evolution and the surveyed area needs to be very large to beat cosmic variance. Only a space-borne mission can properly meet these requirements.

scholarly journals Bark Beetle Population Dynamics in the Anthropocene: Challenges and Solutions

2018 ◽  
Author(s):  
Peter H. W. Biedermann ◽  
Jean-Claude Grégoire ◽  
Axel Gruppe ◽  
Jonas Hagge ◽  
Almuth Hammerbacher ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Bark Beetle ◽  
Collaborative Research ◽  
Bark Beetles ◽  
Large Scale ◽  
Ips Typographus ◽  
Ecological Framework ◽  
Beetle Population ◽  
Spruce Bark ◽  
Important Pest

Tree-killing bark beetles are the most economically important insects in conifer forests worldwide. Yet  despite >200 years of research, the drivers of population eruptions or crashes are still not fully understood, precluding reliable predictions of the effects of global change on beetle population dynamics and impacts on ecosystems and humans.  We critically analyze potential biotic and abiotic drivers of population dynamics of the European spruce bark beetle (Ips typographus) and present a novel ecological framework that integrates the multiple drivers governing this bark beetle system. We call for large-scale collaborative research efforts to improve our understanding of the population dynamics of this important pest; an approach that might serve as a blueprint for other eruptive forest insects.

scholarly journals Faraday rotation measures of Northern hemisphere pulsars using CHIME/Pulsar

2020 ◽  
Vol 496 (3) ◽  
pp. 2836-2848 ◽  
Author(s):  
C Ng ◽  
A Pandhi ◽  
A Naidu ◽  
E Fonseca ◽  
V M Kaspi ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Faraday Rotation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Signal ◽  
First Year ◽  
Systematic Analysis ◽  
Intensity Mapping ◽  
Rotation Measure ◽  
High Cadence

ABSTRACT Using commissioning data from the first year of operation of the Canadian Hydrogen Intensity Mapping Experiment’s (CHIME) Pulsar backend system, we conduct a systematic analysis of the Faraday Rotation Measure (RM) of the Northern hemisphere pulsars detected by CHIME. We present 55 new RMs as well as obtain improved RM uncertainties for 25 further pulsars. CHIME’s low observing frequency and wide bandwidth between 400 and 800 MHz contribute to the precision of our measurements, whereas the high cadence observation provides extremely high signal-to-noise co-added data. Our results represent a significant increase of the pulsar RM census, particularly regarding the Northern hemisphere. These new RMs are for sources that are located in the Galactic plane out to 10 kpc, as well as off the plane to a scale height of ∼16 kpc. This improved knowledge of the Faraday sky will contribute to future Galactic large-scale magnetic structure and ionosphere modelling.

Sign in / Sign up

Export Citation Format

Share Document