scholarly journals Measuring cosmic density of neutral hydrogen via stacking the DINGO-VLA data

2021 ◽  
Author(s):  
Qingxiang Chen ◽  
Martin Meyer ◽  
Attila Popping ◽  
Lister Staveley-Smith ◽  
Julia Bryant ◽  
...  
Keyword(s):  
Atomic Hydrogen ◽  
Mass Measurement ◽  
Three Dimensional ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
One Dimensional ◽  
The Galaxy ◽  
Mass Assembly ◽  
The Universe ◽  
Good Agreement

Abstract We use the 21 cm emission line data from the DINGO-VLA project to study the atomic hydrogen gas H i of the Universe at redshifts z < 0.1. Results are obtained using a stacking analysis, combining the H i signals from 3622 galaxies extracted from 267 VLA pointings in the G09 field of the Galaxy and Mass Assembly Survey (GAMA). Rather than using a traditional one-dimensional spectral stacking method, a three-dimensional cubelet stacking method is used to enable deconvolution and the accurate recovery of average galaxy fluxes from this high-resolution interferometric dataset. By probing down to galactic scales, this experiment also overcomes confusion corrections that have been necessary to include in previous single dish studies. After stacking and deconvolution, we obtain a 30σ H i mass measurement from the stacked spectrum, indicating an average H i mass of ${{M_{\rm {{H}\,{I}}}}}=(1.67\pm 0.18)\times 10^{9}~{{{\rm M}_{\odot }}}$. The corresponding cosmic density of neutral atomic hydrogen is ${{\Omega _{\rm {{H}\,{I}}}}}=(0.38\pm 0.04)\times 10^{-3}$ at redshift of z = 0.051. These values are in good agreement with earlier results, implying there is no significant evolution of ΩH I at lower redshifts.

Studying the Patterns of the Universe

2011 ◽  
Vol 20 (2) ◽  
Author(s):  
T. Sepp ◽  
E. Tempel ◽  
M. Gramann ◽  
P. Nurmi ◽  
M. Haupt
Keyword(s):  
Dark Matter ◽  
Galaxy Cluster ◽  
Analytical Models ◽  
Matter Distribution ◽  
Galaxy Groups ◽  
The Galaxy ◽  
Dark Matter Distribution ◽  
Distribution Studies ◽  
The Universe ◽  
Good Agreement

AbstractThe SDSS galaxy catalog is one of the best databases for galaxy distribution studies. The SDSS DR8 data is used to construct the galaxy cluster catalog. We construct the clusters from the calculated luminosity density field and identify denser regions. Around these peak regions we construct galaxy clusters. Another interesting question in cosmology is how observable galaxy structures are connected to underlying dark matter distribution. To study this we compare the SDSS DR7 galaxy group catalog with galaxy groups obtained from the semi-analytical Millennium N-Body simulation. Specifically, we compare the group richness, virial radius, maximum separation and velocity dispersion distributions and find a relatively good agreement between the mock catalog and observations. This strongly supports the idea that the dark matter distribution and galaxies in the semi-analytical models and observations are very closely linked.

scholarly journals 3D non-LTE line formation of neutral carbon in the Sun

2019 ◽  
Vol 624 ◽  
pp. A111 ◽  
Author(s):  
A. M. Amarsi ◽  
P. S. Barklem ◽  
R. Collet ◽  
N. Grevesse ◽  
M. Asplund
Keyword(s):  
Three Dimensional ◽  
Solar Spectrum ◽  
Neutral Hydrogen ◽  
Stellar Atmospheres ◽  
Impact Excitation ◽  
Solar Photosphere ◽  
Late Type ◽  
Current Standard ◽  
Standard Value ◽  
Good Agreement

Carbon abundances in late-type stars are important in a variety of astrophysical contexts. However C I lines, one of the main abundance diagnostics, are sensitive to departures from local thermodynamic equilibrium (LTE). We present a model atom for non-LTE analyses of C I lines, that uses a new, physically-motivated recipe for the rates of neutral hydrogen impact excitation. We analyse C I lines in the solar spectrum, employing a three-dimensional (3D) hydrodynamic model solar atmosphere and 3D non-LTE radiative transfer. We find negative non-LTE abundance corrections for C I lines in the solar photosphere, in accordance with previous studies, reaching up to around 0.1 dex in the disk-integrated flux. We also present the first fully consistent 3D non-LTE solar carbon abundance determination: we infer log ɛC = 8.44 ± 0.02, in good agreement with the current standard value. Our models reproduce the observed solar centre-to-limb variations of various C I lines, without any adjustments to the rates of neutral hydrogen impact excitation, suggesting that the proposed recipe may be a solution to the long-standing problem of how to reliably model inelastic collisions with neutral hydrogen in late-type stellar atmospheres.

scholarly journals Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures

Coatings ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
Minho Seong ◽  
Hyun-Ha Park ◽  
Insol Hwang ◽  
Hoon Eui Jeong
Keyword(s):  
Aspect Ratio ◽  
Structural Stability ◽  
High Aspect Ratio ◽  
Three Dimensional ◽  
Normal Direction ◽  
One Dimensional ◽  
Reversible Adhesion ◽  
Adhesion Behavior ◽  
Organic Nanomaterials ◽  
Good Agreement

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-aspect-ratio, slender structures are mechanically less durable. In this study, we demonstrate a highly flexible and robust interlocking system that exhibits strong and reversible adhesion based on physical interlocking between three-dimensional (3D) microscale architectures. The 3D microstructures have protruding tips on their cylindrical stems, which enable tight mechanical binding between the microstructures. Based on the unique 3D architectures, the interlocking adhesives exhibit remarkable adhesion strengths in both the normal and shear directions. In addition, their adhesion is highly reversible due to the robust mechanical and structural stability of the microstructures. An analytical model is proposed to explain the measured adhesion behavior, which is in good agreement with the experimental results.

scholarly journals Line Intensity Mapping during the Epoch of Reionization

2017 ◽  
Vol 12 (S333) ◽  
pp. 250-253
Author(s):  
Marta B. Silva ◽  
Saleem Zaroubi
Keyword(s):  
High Redshift ◽  
Three Dimensional ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Light Sources ◽  
First Stars ◽  
Galaxy Surveys ◽  
Gas Phases ◽  
Intensity Mapping ◽  
High Redshift Universe

AbstractCharacterizing the properties and the evolution of the first stars and galaxies is a challenging task for traditional galaxy surveys since they are sensitivity limited and can only detect the brightest light sources. Three-dimensional intensity mapping (IM) of transition lines can be a valuable alternative to study the high redshift Universe given that this technique avoids sensitivity limitation problems by measuring the overall emission of a line, with a low resolution, without resolving its sources. While 21cm line IM surveys probe neutral hydrogen gas and can, therefore, be used to probe the state of the IGM and the evolution of the ionization field during the Epoch of Reionization (EoR). IM surveys of other lines, such as CO, CII, Ly-alpha or H-alpha, can be used to probe the galaxies which emitted most of the ionizing radiation responsible for the EoR. These lines will trace the different ISM gas phases, the excitation state of this gas, its metallicity, etc. This study addresses IM of multiple transition lines and how it can be used to probe the EoR and to constrain the redshift evolution of galaxy properties.

scholarly journals Neutral hydrogen gas within and around NGC 1316

2019 ◽  
Vol 628 ◽  
pp. A122 ◽  
Author(s):  
P. Serra ◽  
F. M. Maccagni ◽  
D. Kleiner ◽  
W. J. G. de Blok ◽  
J. H. van Gorkom ◽  
...  
Keyword(s):  
Large Scale ◽  
Molecular Form ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Neutral Gas ◽  
Tidal Forces ◽  
The Galaxy ◽  
Long Tails ◽  
Stellar Body ◽  
Fornax Cluster

We present MeerKAT observations of neutral hydrogen gas (H I) in the nearby merger remnant NGC 1316 (Fornax A), the brightest member of a galaxy group which is falling into the Fornax cluster. We find H I on a variety of scales, from the galaxy centre to its large-scale environment. For the first time we detect H I at large radii (70–150 kpc in projection), mostly distributed on two long tails associated with the galaxy. Gas in the tails dominates the H I mass of NGC 1316: 7 × 108 M⊙– 14 times more than in previous observations. The total H I mass is comparable to the amount of neutral gas found inside the stellar body, mostly in molecular form. The H I tails are associated with faint optical tidal features thought to be the remnant of a galaxy merger occurred a few billion years ago. They demonstrate that the merger was gas-rich. During the merger, tidal forces pulled some gas and stars out to large radii, where we now detect them in the form of optical tails and, thanks to our new data, H I tails; while torques caused the remaining gas to flow towards the centre of the remnant, where it was converted into molecular gas and fuelled the starburst revealed by the galaxy’s stellar populations. Several of the observed properties of NGC 1316 can be reproduced by a ∼10:1 merger between a dominant, gas-poor early-type galaxy and a smaller, gas-rich spiral occurred 1–3 Gyr ago, likely followed by subsequent accretion of satellite galaxies.

Numerical Investigation of the Thermal Behavior in a Hydrogen Tank During Fast Filling Process

2011 ◽  
Author(s):  
Youhei Takagi ◽  
Naoya Sugie ◽  
Kazuhiro Takeda ◽  
Yasunori Okano ◽  
Tooru Eguchi ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Hydrogen Gas ◽  
Tank Wall ◽  
Filling Process ◽  
Adiabatic Wall ◽  
Buoyant Force ◽  
One Dimensional ◽  
Dimensional Simulation

To investigate the thermal behavior during fast hydrogen filling process, the simple one-dimensional analysis considering the heat conduction in tank wall and the three-dimensional numerical simulation dealing with inner gas region were carried out. The numerical analyses were subject to the fast filling test of 35 MPa hydrogen gas into 34 litter tank for 80 seconds. The one-dimensional analysis predicted the temperature rise and the heat loss into surrounding air qualitatively and the averaged temperature of tank wall was underestimated. On the other hand, the three-dimensional simulation overestimated the temperature distribution because of using adiabatic wall condition. However, the effects of buoyant force and convective flow on local thermal profile were fully explained from our numerical results.

scholarly journals Galactic Plane Surveys at Low Frequencies

2002 ◽  
Vol 199 ◽  
pp. 251-258
Author(s):  
A.R. Taylor
Keyword(s):  
Interstellar Medium ◽  
Atomic Hydrogen ◽  
Angular Resolution ◽  
Spatial Scales ◽  
High Sensitivity ◽  
Hydrogen Gas ◽  
Dimensional Structure ◽  
High Angular Resolution ◽  
Wide Field ◽  
The Galaxy

Until recently, high angular resolution and high sensitivity surveys of the radio emission from the plane of our Galaxy were available only at frequencies of several GHz, where large single dish radio telescopes provide arcminute scale angular resolution. At these frequencies thermal radiation from HII regions and diffuse ionized gas comprise a major component of the Galactic emission. Advances in wide field interferometric imaging techniques now make it possible to carry out high sensitivity surveys of the Galaxy with arcminute scale angular resolution at 1.4 GHz and below. Over the past few years initial synthesis surveys have been made. More ambitious surveys that combined sensitive continuum observations with full polarimetry and images of the 3-dimensional structure of atomic hydrogen gas at pc scales are currently underway in the northern (DRAO) and southern (ATNF) hemispheres. The interstellar medium of the Galaxy contains structure on all spatial scales, and these surveys combined data from aperture synthesis telescopes and signal dish antennas to provide full spatial frequency coverage to the resolution limit. Preliminary results reveal wide-spread features and processes in the the interstellar medium that are not readily visible by other means, including, for example, unusual atomic hydrogen structures related to the vertical transfer of matter and radiation between the disk and halo of the Galaxy, Faraday rotation structures that allow study of the magnetic field and diffuse ionized component in the plane of the Galaxy, and a cold atomic phase of the neutral medium that may provide a link between global shock phenomena in the galaxy and the formation of molecular clouds.

scholarly journals The Detection of Dark Galaxies in Blind HI Surveys

2007 ◽  
Vol 3 (S244) ◽  
pp. 7-16 ◽  
Author(s):  
Jonathan I. Davies
Keyword(s):  
Dark Matter ◽  
Numerical Model ◽  
Atomic Hydrogen ◽  
Cold Dark Matter ◽  
The Galaxy ◽  
Galaxy Population ◽  
The Universe

AbstractOne explanation for the disparity between Cold Dark Matter predictions of galaxy numbers and observations could be that there are numerous dark galaxies in the Universe. These galaxies may still contain baryons, but no stars, and may be detectable in the 21cm line of atomic hydrogen. In this paper we describe a numerical model of the galaxy population and predict what might be found in blind 21cm surveys. We describe the detection of a dark galaxy candidate (VIRGOHI21) and discuss a model of its origin.

The new one-dimensional coordination polymercatena-poly[[diaquasodium(I)]-μ-oxalato-[diaquairon(III)]-μ-oxalato]

2016 ◽  
Vol 72 (3) ◽  
pp. 243-250 ◽  
Author(s):  
Mohamed Al Amine Benhacine ◽  
Malika Hamadène ◽  
Sofiane Bouacida ◽  
Hocine Merazig
Keyword(s):  
Three Dimensional ◽  
Local Symmetry ◽  
Ternary Oxide ◽  
Inorganic Polymers ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
One Dimensional ◽  
Oxalate Ligand ◽  
Metal Oxalate ◽  
Good Agreement

The oxalate dianion is one of the most studied ligands and is capable of bridging two or more metal centres and creating inorganic polymers based on the assembly of metal polyhedra with a wide variety of one-, two- or three-dimensional extended structures. Yellow single crystals of a new mixed-metal oxalate, namelycatena-poly[[diaquasodium(I)]-μ-oxalato-κ4O1,O2:O1′,O2′-[diaquairon(III)]-μ-oxalato-κ4O1,O2:O1′,O2′], [NaFe(C2O4)2(H2O)4]n, have been synthesized and the crystal structure elucidated by X-ray diffraction analysis. The compound crystallizes in the noncentrosymmetric space groupI41(Z= 4). The asymmetric unit contains one NaIand one FeIIIatom lying on a fourfold symmetry axis, one μ2-bridging oxalate ligand and two aqua ligands. Each metal atom is surrounded by two chelating oxalate ligands and two equivalent water molecules. The structure consists of infinite one-dimensional chains of alternating FeO4(H2OW1)2and NaO4(H2OW2)2octahedra, bridged by oxalate ligands, parallel to the [100] and [010] directions, respectively. Because of thecisconfiguration and the μ2-coordination mode of the oxalate ligands, the chains run in a zigzag manner. This arrangement facilitates the formation of hydrogen bonds between neighbouring chains involving the H2O and oxalate ligands, leading to a two-dimensional framework. The structure of this new one-dimensional coordination polymer is shown to be unique among theAIMIII(C2O4)2(H2O)nseries. In addition, the absorption bands in the IR and UV–Visible regions and their assignments are in good agreement with the local symmetry of the oxalate ligand and the irregular environment of iron(III). The final product of the thermal decomposition of this precursor is the well-known ternary oxide NaFeO2.

scholarly journals Quantifying EoR delay spectrum contamination from diffuse radio emission

2020 ◽  
Vol 494 (3) ◽  
pp. 3712-3727 ◽  
Author(s):  
Adam E Lanman ◽  
Jonathan C Pober ◽  
Nicholas S Kern ◽  
Eloy de Lera Acedo ◽  
David R DeBoer ◽  
...  
Keyword(s):  
Radio Emission ◽  
Large Scale ◽  
Power Spectra ◽  
Neutral Hydrogen ◽  
Spectral Structure ◽  
Wide Field ◽  
Electromagnetic Simulations ◽  
The Galaxy ◽  
Spectral Weighting ◽  
The Universe

ABSTRACT The 21 cm hyperfine transition of neutral hydrogen offers a promising probe of the large-scale structure of the universe before and during the Epoch of Reionization (EoR), when the first ionizing sources formed. Bright radio emission from foreground sources remains the biggest obstacle to detecting the faint 21 cm signal. However, the expected smoothness of foreground power leaves a clean window in Fourier space where the EoR signal can potentially be seen over thermal noise. Though the boundary of this window is well defined in principle, spectral structure in foreground sources, instrumental chromaticity, and choice of spectral weighting in analysis all affect how much foreground power spills over into the EoR window. In this paper, we run a suite of numerical simulations of wide-field visibility measurements, with a variety of diffuse foreground models and instrument configurations, and measure the extent of contaminated Fourier modes in the EoR window using a delay-transform approach to estimate power spectra. We also test these effects with a model of the Hydrogen Epoch of Reionization Array (HERA) antenna beam generated from electromagnetic simulations, to take into account further chromatic effects in the real instrument. We find that foreground power spillover is dominated by the so-called pitchfork effect, in which diffuse foreground power is brightened near the horizon due to the shortening of baselines. As a result, the extent of contaminated modes in the EoR window is largely constant over time, except when the Galaxy is near the pointing centre.

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