scholarly journals High-redshift test of gravity using enhanced growth of small structures probed by the neutral hydrogen distribution

2019 ◽  
Vol 100 (6) ◽  
Author(s):  
Matteo Leo ◽  
Christian Arnold ◽  
Baojiu Li
Keyword(s):  
High Redshift ◽  
Neutral Hydrogen ◽  
Hydrogen Distribution

scholarly journals Constraining the reionization history using deep learning from 21-cm tomography with the Square Kilometre Array

2020 ◽  
Vol 494 (1) ◽  
pp. 600-606 ◽  
Author(s):  
Tumelo Mangena ◽  
Sultan Hassan ◽  
Mario G Santos
Keyword(s):  
High Redshift ◽  
Neutral Hydrogen ◽  
Power Spectral Analysis ◽  
High Accuracy ◽  
Neutral Fraction ◽  
Coefficient Of Determination ◽  
Data Sets ◽  
Imaging Data ◽  
Hydrogen Distribution ◽  
Power Spectral

ABSTRACT Upcoming 21-cm surveys with the SKA1-LOW telescope will enable imaging of the neutral hydrogen distribution on cosmological scales in the early Universe. These surveys are expected to generate huge imaging data sets that will encode more information than the power spectrum. This provides an alternative unique way to constrain the reionization history, which might break the degeneracy in the power spectral analysis. Using convolutional neural networks, we create a fast estimator of the neutral fraction from the 21-cm maps that are produced by our large seminumerical simulation. Our estimator is able to efficiently recover the neutral fraction ($x_{\rm H\,{\small I}}$) at several redshifts with a high accuracy of 99 per cent as quantified by the coefficient of determination R2. Adding the instrumental effects from the SKA design slightly increases the loss function, but nevertheless we are still able to recover the neutral fraction with a similar high accuracy of 98 per cent, which is only 1 per cent less. While a weak dependence on redshift is observed, the accuracy increases rapidly with decreasing neutral fraction. This is due to the fact that the instrumental noise increases towards high redshift where the Universe is highly neutral. Our results show the promise of directly using 21cm-tomography to constrain the reionization history in a model-independent way, complementing similar efforts, such as those of the optical depth measurements from the cosmic microwave background observations by Planck.

scholarly journals The effect of dust bias on the census of neutral gas and metals in the high-redshift Universe due to SDSS-II quasar colour selection

2019 ◽  
Vol 486 (3) ◽  
pp. 4377-4397 ◽  
Author(s):  
Jens-Kristian Krogager ◽  
Johan P U Fynbo ◽  
Palle Møller ◽  
Pasquier Noterdaeme ◽  
Kasper E Heintz ◽  
...  
Keyword(s):  
Mass Density ◽  
High Redshift ◽  
Target Selection ◽  
Neutral Hydrogen ◽  
Sloan Digital Sky Survey ◽  
Selection Probability ◽  
Optical Extinction ◽  
Neutral Gas ◽  
High Redshift Universe ◽  
The Impact

ABSTRACT We present a systematic study of the impact of a dust bias on samples of damped Ly α absorbers (DLAs). This bias arises as an effect of the magnitude and colour criteria utilized in the Sloan Digital Sky Survey (SDSS) quasar target selection up until data release 7 (DR7). The bias has previously been quantified assuming only a contribution from the dust obscuration. In this work, we apply the full set of magnitude and colour criteria used up until SDSS-DR7 in order to quantify the full impact of dust biasing against dusty and metal-rich DLAs. We apply the quasar target selection algorithm on a modelled population of intrinsic colours, and by exploring the parameter space consisting of redshift, ($z_{\rm{\small QSO}}$and zabs), optical extinction, and H i column density, we demonstrate how the selection probability depends on these variables. We quantify the dust bias on the following properties derived for DLAs at z ≈ 3: the incidence rate, the mass density of neutral hydrogen and metals, and the average metallicity. We find that all quantities are significantly affected. When considering all uncertainties, the mass density of neutral hydrogen is underestimated by 10–50 per cent, and the mass density in metals is underestimated by 30–200 per cent. Lastly, we find that the bias depends on redshift. At redshift z = 2.2, the mass density of neutral hydrogen and metals might be underestimated by up to a factor of 2 and 5, respectively. Characterizing such a bias is crucial in order to accurately interpret and model the properties and metallicity evolution of absorption-selected galaxies.

scholarly journals Observations of the Lyman-α Universe

2020 ◽  
Vol 58 (1) ◽  
pp. 617-659
Author(s):  
Masami Ouchi ◽  
Yoshiaki Ono ◽  
Takatoshi Shibuya
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Formation Rate ◽  
Neutral Hydrogen ◽  
Resonant Scattering ◽  
Dark Matter Halo ◽  
Emission Data ◽  
Star Forming ◽  
High Redshift Universe

Hydrogen Lyman-α (Lyα) emission has been one of the major observational probes for the high-redshift Universe since the first discoveries of high- z Lyα-emitting galaxies in the late 1990s. Due to the strong Lyα emission originated by resonant scattering and recombination of the most abundant element, Lyα observations witness not only Hii regions of star formation and active galactic nuclei (AGNs) but also diffuse Hi gas in the circumgalactic medium (CGM) and the intergalactic medium (IGM). Here, we review Lyα sources and present theoretical interpretations reached to date. We conclude the following: ▪  A typical Lyα emitter (LAE) at z ≳ 2 with a L* Lyα luminosity is a high- z counterpart of a local dwarf galaxy, a compact metal-poor star-forming galaxy (SFG) with an approximate stellar (dark matter halo) mass and star-formation rate of 108−9M⊙ (1010−11M⊙) and 1–10 M⊙ year−1, respectively. ▪  High- z SFGs ubiquitously have a diffuse Lyα-emitting halo in the CGM extending to the halo virial radius and beyond. ▪  Remaining neutral hydrogen at the epoch of cosmic reionization makes a strong dimming of Lyα emission for galaxies at z > 6 that suggests the late reionization history. The next-generation large-telescope projects will combine Lyα emission data with Hi Lyα absorptions and 21-cm radio data that map out the majority of hydrogen (Hi+Hii) gas, uncovering the exchanges of ( a) matter by outflow and inflow and ( b) radiation, relevant to cosmic reionization, between galaxies and the CGM/IGM.

scholarly journals The First Sample of Sub-Damped Lyα Systems and their Chemical Properties

2004 ◽  
Vol 217 ◽  
pp. 268-269
Author(s):  
Miroslava Dessauges-Zavadsky ◽  
Céline Péroux ◽  
Sandro D'Odorico ◽  
Tae-Sun Kim ◽  
Richard G. McMahon
Keyword(s):  
High Redshift ◽  
Chemical Properties ◽  
Neutral Hydrogen ◽  
Detailed Comparison ◽  
Main Concern ◽  
Chemical Abundance ◽  
Homogeneous Sample ◽  
Quasar Spectra ◽  
Hydrogen Mass ◽  
Detailed Chemical

We took advantage of the ESO UVES/VLT archive of quasar spectra to build a homogeneous sample of ‘sub-DLAs’, absorption line systems with HI column densities between 1019 and 2×1020 cm−2. According to Péroux et al. (2002), these systems should contain a major fraction of the neutral hydrogen mass at z > 3.5 and may thus play an important role at high redshift. Twelve sub-DLAs have been identified. We performed a detailed chemical analysis, and addressed the issues of photoionization corrections. We obtained the first sub-DLA chemical abundance data base ideal for the study of a number of interesting properties of these systems. The implication of sub-DLAs in the cosmic metallicity evolution was our main concern. We also undertook a detailed comparison of the sub-DLA chemical properties with the well studied DLAs to see whether the sub-DLAs are associated with a different class of objects.

scholarly journals Search for HI Bubbles Around WR Stars: WR 149

1996 ◽  
Vol 169 ◽  
pp. 619-620
Author(s):  
C. Cappa de Nicolau ◽  
V.S. Niemela ◽  
U. Herbstmeier ◽  
B. Koribalski
Keyword(s):  
Interstellar Medium ◽  
Neutral Hydrogen ◽  
Gas Bubbles ◽  
Stellar Winds ◽  
Hydrogen Distribution ◽  
Neutral Gas ◽  
Rayet Star

The interaction of strong stellar winds with the interstellar medium creates large cavities or interstellar bubbles surrounded by expanding outer shells. 21-cm line (HI) observations have revealed the presence of such neutral gas bubbles around several WR stars (e.g. Niemela & Cappa de Nicolau 1991 and references therein; Dubner et al. 1992).Continuing our search for HI bubbles around WR stars, we have analyzed the neutral hydrogen distribution in the vicinity of the Wolf-Rayet star WR149, a highly reddened WN6-7 star located at 6.5 kpc in the direction (l,b) = (89.°53,+0.°65).

scholarly journals Lyman α Emission from Disk Absorption Systems in QSOs: Star Formation in Young Galaxy Disks

1989 ◽  
Vol 134 ◽  
pp. 557-559
Author(s):  
Harding E. Smith ◽  
Ross D. Cohen ◽  
Joseph E. Burns ◽  
David J. Moore ◽  
Barbara Uchida
Keyword(s):  
Rest Frame ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Disk Galaxies ◽  
List Type ◽  
Ionization State ◽  
Low Velocity ◽  
High Ionization ◽  
Dispersion Component ◽  
Disk Component

The strong self-damped Lyman α absorption systems present in the spectra of high redshift QSOs represent a unique population of absorber which has recently been associated with the precursors of current disk galaxies. In a low resolution survey for what we have come to call “Lyman α disk systems” performed at Lick Observatory (Wolfe, et al. 1986, Ap. J. Suppl. 61, 249) approximately 18 systems with confirmed damped Lyman α profiles and rest frame equivalent widths greater than 5 Å were detected in a sample of 68 high redshift QSOs (Smith, Cohen and Bradley 1986, Ap. J. 310, 583). Subsequent higher resolution study has shown these systems to have the following properties (Turnshek, et al. 1988, Ap. J., in press): 1.Neutral hydrogen column densities, 2 × 1020 ≤ NHI ≤ 8 × 1021 cm−2.2.Low-mixed ionization state. Typically the low ionization states dominate the high ionization states (e.g. CII ≫ CIV). Some enrichment has occurred, −2≲[X/H]⊙ ≲0.3.Gas density, n ≲ 1 cm−3.4.The gas shows two components, a quiescent (disk) component, σν ≲ 10 km s−1, and a turbulent (halo) component, σν ≲ 20 km s−1. Some systems show only the low velocity dispersion component.5.At least one system intervening toward a radio QSO (Pks 0458-020) shows 21-cm absorption. The system shows multiple cloud structure with σν ≈ 6 km s−1, Ts ≈ 100 K, and structure extended over several kpc on the sky.6.There is evidence that these systems may be self gravitating with scale height of the order of 300 pc.7.These systems represent a unique population of absorber (distinct from the ‘Lyman a forest’ and heavy element systems) covering approximately 20% of the sky to z ≈ 3 and accounting for all of the baryonic matter at that redshift.

scholarly journals The Gaseous Content of Galaxies

1972 ◽  
Vol 44 ◽  
pp. 12-36 ◽  
Author(s):  
Morton S. Roberts
Keyword(s):  
Neutral Hydrogen ◽  
Hubble Constant ◽  
Type Systems ◽  
Systematic Difference ◽  
Optical Center ◽  
Hydrogen Distribution ◽  
Interstellar Gas ◽  
A Value ◽  
Galaxy Type ◽  
The Difference

A general review is given of the content and distribution of interstellar gas within galaxies. The constancy of the ratio N(He)/N(H), independent of galaxy type (spirals and irregulars), is discussed and the possible mechanisms for this constancy are considered. The helium abundance does not vary across the disk of spirals, although nitrogen and possibly other elements do.The gross features of the neutral hydrogen distribution in our Galaxy and other systems are described. In spirals, the peak of the radial distribution of Hi is located well away from the optical center. This is not the case for irregular-type systems. A possible correlation of the relative location of the maxima of Hi and Hii distributions with galaxy type is described. Many spirals studied with high enough relative angular resolution show concentrations of Hi in their outermost regions. These may be due to hydrogen companions or warps in the hydrogen plane. Hydrogen ‘bridges’ are described and a new example for the triple system M81–M82–NGC 3077 is given. This latter case may be an extreme example of distortion by companion galaxies of the Hi associated with a massive galaxy.The neutral hydrogen content of a galaxy and its correlation with other integral properties is discussed. The absorption profile due to hydrogen associated with the radio galaxy Centaurus A is given. Comparison of optical and 21-cm measurements of galaxian redshifts shows excellent agreement over the radical velocity range −400 to + 5200 km s−1. There is, however, a systematic difference between 21 cm and optical redshifts over the range ∼ 1200 to ∼ 2400 km s−1 for optical values based on blue-sensitive spectra. The difference, ∼ 100 km s−1, is most likely due to blending of galaxian and night sky H and K absorption lines. The Hubble Constant is derived from a redshift-21 cm flux relation. Values in the range 78 to 109 km s−1 Mpc−1 are derived. A value of 97 kms−1 Mpc−1 is favored.

scholarly journals Tracing Cosmic Dawn

2017 ◽  
Vol 12 (S333) ◽  
pp. 22-25
Author(s):  
Anastasia Fialkov
Keyword(s):  
High Redshift ◽  
Neutral Hydrogen ◽  
Parameter Study ◽  
Radio Bursts ◽  
Large Uncertainty ◽  
Poor Knowledge ◽  
Model Independent ◽  
High Redshift Universe ◽  
Observational Effort ◽  
The Way

AbstractObservational effort is on the way to probe the 21-cm of neutral hydrogen from the epochs of Reionization and Cosmic Dawn. Our current poor knowledge of high redshift astrophysics results in a large uncertainty in the theoretically predicted 21-cm signal. A recent parameter study that is highlighted here explores the variety of 21-cm signals resulting from viable astrophysical scenarios. Model-independent relations between the shape of the signal and the underlying astrophysics are discussed. Finally, I briefly note on possible alternative probes of the high redshift Universe, specifically Fast Radio Bursts.

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.

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