scholarly journals Stacking redshifted 21 cm images of H ii regions around high-redshift galaxies as a probe of early reionization

2020 ◽  
Vol 501 (1) ◽  
pp. 146-156
Author(s):  
James E Davies ◽  
Rupert A C Croft ◽  
Tiziana Di-Matteo ◽  
Bradley Greig ◽  
Yu Feng ◽  
...  
Keyword(s):  
High Redshift ◽  
Neutral Hydrogen ◽  
Neutral Fraction ◽  
H Ii Regions ◽  
Fourier Space ◽  
Signal To Noise ◽  
First Stars ◽  
High Redshift Galaxies ◽  
H Ii Region ◽  
The Universe

ABSTRACT A number of current and future experiments aim to detect the reionization of neutral hydrogen by the first stars and galaxies in the Universe via the redshifted 21 cm line. Using the bluetides simulation, we investigate the measurement of an average ionized region towards the beginning of reionization by stacking redshifted 21 cm images around optically identified bright galaxies using mock observations. We find that with an SKA 1000 h observation, assuming perfect foreground subtraction, a 5σ detection of a stacked H ii region can be made with 30 images around some of the brightest galaxies in bluetides (brighter than MUV < −22.75) at z = 9 (corresponding to a neutral fraction of 90.1 per cent in our model). We present simulated relationships between the UV magnitude of galaxies, the sizes of the ionized regions they reside in, and the shape of the stacked profiles. These mock observations can also distinguish between scenarios where the intergalactic medium is in net emission or absorption of 21 cm photons. Once 21 cm foreground contamination is included, we find that even with up to 200 images around these rare, bright galaxies, only a tentative >1σ detection will be possible. However, partial foreground subtraction substantially improves signal to noise. For example, we predict that reducing the area of Fourier space dominated by foregrounds by 50 (80) per cent will allow >3σ (>5σ) detections of ionized regions at z = 9.

scholarly journals Shedding light on high-redshift galaxies with the 21cm signal

2019 ◽  
Vol 15 (S352) ◽  
pp. 69-69
Author(s):  
Anne Hutter
Keyword(s):  
Galaxy Evolution ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
First Stars ◽  
High Redshift Galaxies ◽  
Redshift Galaxy ◽  
First Galaxies ◽  
Galaxy Population ◽  
The Impact ◽  
Redshift Galaxies

AbstractReionization represents an important epoch in the history in the Universe, when the first stars and galaxies gradually ionize the neutral hydrogen in the intergalactic medium (IGM). Understanding the nature of the ionizing sources, the associated ionization of the IGM, and its impact on subsequent structure formation and galaxy evolution by means of radiative feedback effects, represent key outstanding questions in current astrophysics. High-redshift galaxy observations and simulations have significantly extended our knowledge on the nature of high-redshift galaxies. However, essential properties such as the escape fraction of ionizing photons from galaxies into the IGM and their dependency on galactic properties remain essentially unknown, but determine significantly the distribution and time evolution of the ionized regions during reionization. Analyzing this ionization topology by means of the neutral hydrogen sensitive 21cm signal with radio interferometers such as SKA offers a complementary and unique opportunity to determine the nature of these first galaxies. I will show results from a self-consistent semi-numerical model of galaxy evolution and reionization, and discuss the potential of inferring galactic properties with the 21cm signal as well as the impact of reionization on the high-redshift galaxy population and its evolution.

scholarly journals Results from Searches for High-Redshift Galaxies around Damped Lyα Systems

1996 ◽  
Vol 171 ◽  
pp. 291-294
Author(s):  
S. J. Warren ◽  
P. Møller
Keyword(s):  
Narrow Band ◽  
Narrow Band Imaging ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
The Other ◽  
High Redshift Galaxies ◽  
Groups Of Galaxies ◽  
Damped Systems ◽  
The Universe ◽  
Redshift Galaxies

There was not much said at this conference about the damped Lyα absorbers, yet locally and at high redshift nearly all the neutral hydrogen in the Universe lies in the damped systems, so they may have much to tell us about when and how galaxies formed. This talk is concerned with the results of narrow-band imaging searches for Lyα emission from, and around, damped Lyα absorbers. There have been many such searches, but very few detections. Here we concentrate on two groups of galaxies at high redshift, z > 2, found by this technique. One of these is a recent discovery (Francis et al. 1995), and for the other we discuss some new observations (Warren and Møller 1995). A study of these two groups provides some clues to the nature of the damped absorbers at high redshift, and the rôle they play in the formation of galaxies.

scholarly journals New methods for identifying Lyman continuum leakers and reionization-epoch analogues

2020 ◽  
Vol 498 (1) ◽  
pp. 164-180 ◽  
Author(s):  
Harley Katz ◽  
Dominika Ďurovčíková ◽  
Taysun Kimm ◽  
Joki Rosdahl ◽  
Jeremy Blaizot ◽  
...  
Keyword(s):  
Emission Line ◽  
Galaxy Formation ◽  
Dwarf Galaxy ◽  
High Redshift ◽  
Indirect Methods ◽  
High Redshift Galaxies ◽  
Lyman Continuum ◽  
The Universe ◽  
Ionization Parameter ◽  
Redshift Galaxies

ABSTRACT Identifying low-redshift galaxies that emit Lyman continuum radiation (LyC leakers) is one of the primary, indirect methods of studying galaxy formation in the epoch of reionization. However, not only has it proved challenging to identify such systems, it also remains uncertain whether the low-redshift LyC leakers are truly ‘analogues’ of the sources that reionized the Universe. Here, we use high-resolution cosmological radiation hydrodynamics simulations to examine whether simulated galaxies in the epoch of reionization share similar emission line properties to observed LyC leakers at z ∼ 3 and z ∼ 0. We find that the simulated galaxies with high LyC escape fractions (fesc) often exhibit high O32 and populate the same regions of the R23–O32 plane as z ∼ 3 LyC leakers. However, we show that viewing angle, metallicity, and ionization parameter can all impact where a galaxy resides on the O32–fesc plane. Based on emission line diagnostics and how they correlate with fesc, lower metallicity LyC leakers at z ∼ 3 appear to be good analogues of reionization-era galaxies. In contrast, local [S ii]-deficient galaxies do not overlap with the simulated high-redshift LyC leakers on the S ii Baldwin–Phillips–Terlevich (BPT) diagram; however, this diagnostic may still be useful for identifying leakers. We use our simulated galaxies to develop multiple new diagnostics to identify LyC leakers using infrared and nebular emission lines. We show that our model using only [C ii]158 μm and [O iii]88 μm can identify potential leakers from non-leakers from the local Dwarf Galaxy Survey. Finally, we apply this diagnostic to known high-redshift galaxies and find that MACS 1149_JD1 at z = 9.1 is the most likely galaxy to be actively contributing to the reionization of the Universe.

scholarly journals Metallicity Evolution of Damped Lyman-α Systems

2001 ◽  
Vol 204 ◽  
pp. 307-321
Author(s):  
Sandra Savaglio
Keyword(s):  
Metal Content ◽  
Column Density ◽  
High Redshift ◽  
Heavy Elements ◽  
Gas Content ◽  
High Redshift Galaxies ◽  
The Galaxy ◽  
The Universe ◽  
Ism Dust ◽  
General Method

According to Pei, Fall, & Hauser (1999), the global metallicity evolution of the Universe can be represented by the ratio of the total metal content to the total gas content measured in damped Lyman–α (DLA) systems (the “column density weighted metallicity” à la Pettini). To minimize dust obscuration effects, a DLA sample with negligible dust content is considered, namely, 50 DLAs with log NHI < 20.8. The global metallicity found shows clear evidence of redshift evolution that goes from ~ 1/30 solar at z ~ 4.1 to solar at z ~ 0.4. More generally, DLAs with measured heavy elements probe the ISM of high redshift galaxies. The whole sample collected from the literature contains 75 DLAs. The metallicity is calculated adopting for the dust correction the most general method used so far, based on models of the ISM dust depletions in the Galaxy. The intrinsic metallicity evolution of DLA galaxies is d log ZDLA/dz = −0.33 ± 0.06.

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 The importance of magnetic fields for the initial mass function of the first stars

2020 ◽  
Vol 497 (1) ◽  
pp. 336-351 ◽  
Author(s):  
Piyush Sharda ◽  
Christoph Federrath ◽  
Mark R Krumholz
Keyword(s):  
Magnetic Fields ◽  
Initial Conditions ◽  
High Redshift ◽  
Three Dimensional ◽  
Mass Function ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Dynamo Theory ◽  
First Stars ◽  
High Redshift Galaxies

ABSTRACT Magnetic fields play an important role for the formation of stars in both local and high-redshift galaxies. Recent studies of dynamo amplification in the first dark matter haloes suggest that significant magnetic fields were likely present during the formation of the first stars in the Universe at redshifts of 15 and above. In this work, we study how these magnetic fields potentially impact the initial mass function (IMF) of the first stars. We perform 200 high-resolution, three-dimensional (3D), magnetohydrodynamic (MHD) simulations of the collapse of primordial clouds with different initial turbulent magnetic field strengths as predicted from turbulent dynamo theory in the early Universe, forming more than 1100 first stars in total. We detect a strong statistical signature of suppressed fragmentation in the presence of strong magnetic fields, leading to a dramatic reduction in the number of first stars with masses low enough that they might be expected to survive to the present-day. Additionally, strong fields shift the transition point where stars go from being mostly single to mostly multiple to higher masses. However, irrespective of the field strength, individual simulations are highly chaotic, show different levels of fragmentation and clustering, and the outcome depends on the exact realization of the turbulence in the primordial clouds. While these are still idealized simulations that do not start from cosmological initial conditions, our work shows that magnetic fields play a key role for the primordial IMF, potentially even more so than for the present-day IMF.

scholarly journals Star Formation in Damped Lyman α Selected Galaxies

2007 ◽  
Vol 3 (S244) ◽  
pp. 284-288
Author(s):  
Lise Christensen
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
High Redshift ◽  
Neutral Hydrogen ◽  
Disk Galaxies ◽  
Local Universe ◽  
High Redshift Galaxies ◽  
Neutral Gas ◽  
Integral Field Spectroscopy ◽  
Integral Field

AbstractI present results from an ongoing survey to study galaxies associated with damped Lyman-α (DLA) systems at redshifts z>2. Integral field spectroscopy is used to search for Lyα emission line objects at the wavelengths where the emission from the quasars have been absorbed by the DLAs. The DLA galaxy candidates detected in this survey are found at distances of 10–20 kpc from the quasar line of sight, implying that galaxies are surrounded by neutral hydrogen at large distances. If we assume that the distribution of neutral gas is exponential, the scale length of the neutral gas is ~6 kpc, similar to large disk galaxies in the local Universe. The emission line luminosities imply smaller star formation rates compared to other high redshift galaxies found in luminosity selected samples.

scholarly journals An analytic model for [O iii] fine structure emission from high redshift galaxies

2020 ◽  
Vol 499 (3) ◽  
pp. 3417-3433 ◽  
Author(s):  
Shengqi Yang ◽  
Adam Lidz
Keyword(s):  
Fine Structure ◽  
High Redshift ◽  
Formation Rate ◽  
Line Emission ◽  
Relative Volume ◽  
H Ii Regions ◽  
Analytic Model ◽  
Free Electrons ◽  
High Redshift Galaxies ◽  
Better Than

ABSTRACT Recent ALMA measurements have revealed bright [O iii] 88 micron line emission from galaxies during the Epoch of Reionization (EoR) at redshifts as large as z ∼ 9. We introduce an analytic model to help interpret these and other upcoming [O iii] 88 micron measurements. Our approach sums over the emission from discrete Str$\ddot{\mathrm{o}}$mgren spheres and considers the total volume of ionized hydrogen in a galaxy of a given star-formation rate. We estimate the relative volume of doubly ionized oxygen and ionized hydrogen and its dependence on the spectrum of ionizing photons. We then calculate the level populations of O iii ions in different fine-structure states for H ii regions of specified parameters. In this simple model, a galaxy’s [O iii] 88 μm luminosity is determined by the typical number density of free electrons in H ii regions (ne), the average metallicity of these regions (Z), the rate of hydrogen ionizing photons emitted (QH i), and the shape of the ionizing spectrum. We cross-check our model by comparing it with detailed cloudy calculations, and find that it works to better than 15${{\ \rm per\ cent}}$ accuracy across a broad range of parameter space. Applying our model to existing ALMA data at z ∼ 6–9, we derive lower bounds on the gas metallicity and upper bounds on the gas density in the H ii regions of these galaxies. These limits vary considerably from galaxy to galaxy, with the tightest bounds indicating Z ≳ 0.5Z⊙ and nH ≲ 50 cm−3 at 2 − σ confidence.

scholarly journals The Magellanic Clouds and the Primordial Helium Abundance

2000 ◽  
Vol 198 ◽  
pp. 194-203 ◽  
Author(s):  
Manuel Peimbert ◽  
Antonio Peimbert
Keyword(s):  
Neutral Hydrogen ◽  
Magellanic Clouds ◽  
Heavy Elements ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Temperature Variations ◽  
Systematic Effects ◽  
H Ii Region ◽  
Primordial Helium

A new determination of the pregalactic helium abundance based on the Magellanic Clouds H II regions is discussed. This determination amounts to Yp = 0.2345 ± 0.0030 and is compared with those derived from giant extragalactic H II regions in systems with extremely low heavy elements content. It is suggested that the higher primordial value derived by other authors from giant H II region complexes could be due to two systematic effects: the presence of neutral hydrogen inside the helium Strömgren sphere and the presence of temperature variations inside the observed volume.

scholarly journals Luminosity Bias. II. The Cosmic Web of the First Stars

2013 ◽  
Vol 30 ◽  
Author(s):  
R. Barkana
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Relative Velocity ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Unique Form ◽  
Velocity Difference ◽  
First Stars ◽  
Formation And Evolution ◽  
The Universe

AbstractUnderstanding the formation and evolution of the first stars and galaxies represents one of the most exciting frontiers in astronomy. Since the universe was filled with neutral hydrogen at early times, the most promising method for observing the epoch of the first stars is using the prominent 21-cm spectral line of the hydrogen atom. Current observational efforts are focused on the reionisation era (cosmic age t ~ 500 Myr), with earlier times considered much more challenging. However, the next frontier of even earlier galaxy formation (t ~ 200 Myr) is emerging as a promising observational target. This is made possible by a recently noticed effect of a significant relative velocity between the baryons and dark matter at early times. The velocity difference suppresses star formation, causing a unique form of early luminosity bias. The spatial variation of this suppression enhances large-scale clustering and produces a prominent cosmic web on 100 comoving Mpc scales in the 21-cm intensity distribution. This structure makes it much more feasible for radio astronomers to detect these early stars, and should drive a new focus on this era, which is rich with little-explored astrophysics.

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