Probing the first galaxies with the Square Kilometer Array

Santos, Mário G.; Silva, Marta B.; Pritchard, Jonathan R.; Cen, Renyue; Cooray, Asantha

doi:10.1051/0004-6361/201015695

Cited by 29 publications

(35 citation statements)

References 56 publications

(77 reference statements)

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“…The signal follows the expected qualitative trends (e.g. Furlanetto et al 2006;Baek et al 2010;Santos et al 2011;Mesinger et al 2016;Park et al 2019). During the cosmic dawn, the first galaxies begin to build up the Lyman-α background, coupling the spin (Ts) and kinetic temperatures (T k ).…”

Section: Mock 21-cm Observationmentioning

confidence: 54%

A tale of two sites – I. Inferring the properties of minihalo-hosted galaxies from current observations

Qin

Mesinger

Park

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The very first galaxies that started the cosmic dawn likely resided in so-called "minihalos, with masses of ∼10 5 -10 8 M , accreting their gas from the intergalactic medium through H 2 cooling. Such molecularly-cooled galaxies (MCGs), mostly formed in pristine environments, hosted massive, metal-free stars, and were eventually sterilized by the build-up of a disassociating (Lyman-Werner; LW) background. Therefore, their properties might be very different from the galaxies we see in the later Universe. Although MCGs are probably too faint to be observed directly, we could nevertheless infer their properties from the imprint they leave in the cosmic 21-cm signal. Here we quantify this imprint by extending the public simulation code 21cmFAST to allow for a distinct population of MCGs. We allow MCGs to have different properties from other galaxies, including unique scaling relations for their stellar to halo mass ratios, ionizing escape fractions, and spectral energy distributions. We track inhomogeneous recombinations, disassociative LW feedback, and photo-heating from reionization. After demonstrating how MCGs can shape the 21-cm signal, we explore to what extent current observations can already place constraints on their properties. The CMB optical depth from Planck sets an upper limit on the product of the ionizing escape fraction and the stellar mass in MCGs. When including also the timing of the putative EDGES absorption signal, we find an additional strong degeneracy between the stellar mass and the X-ray luminosity of MCGs. If proven to be of cosmic origin, the timing of the EDGES signal would have been set by MCGs.

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Section: Mock 21-cm Observationmentioning

confidence: 54%

A tale of two sites – I. Inferring the properties of minihalo-hosted galaxies from current observations

Qin

Mesinger

Park

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…However, SKA observations may provide measurements from periods in which fluctuations in the spin temperature dominate (Santos & Cooray 2006). This effect from peculiar velocities could then be used to separate the astrophysical contributions and provide extra information on the nature of the first objects emitting radiation (Barkana & Loeb 2005a;Santos et al 2011). …”

Section: -Simple Astrophysicsmentioning

confidence: 99%

Reionization and the Cosmic Dawn with the Square Kilometre Array

et al. 2013

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The Square Kilometre Array (SKA) will have a low frequency component (SKA-low) which has as one of its main science goals the study of the redshifted 21cm line from the earliest phases of star and galaxy formation in the Universe. This 21cm signal provides a new and unique window both on the time of the formation of the first stars and accreting black holes and the subsequent period of substantial ionization of the intergalactic medium. The signal will teach us fundamental new things about the earliest phases of structure formation, cosmology and even has the potential to lead to the discovery of new physical phenomena. Here we present a white paper with an Executive SummaryThe Square Kilometre Array (SKA) will have a low frequency component (AA-low/SKA-low 1 ) which has as one of its main science goals the study of the redshifted 21cm line from the earliest phases of star and galaxy formation in the Universe (see SKA Memo 125). It is during this phase that the first building blocks of the galaxies that we see around us today, including our own Milky Way, were formed. It is a crucial period for understanding the history of the Universe and one for which we have currently very little observational data.We divide the period into two different phases based on the physical processes which affect the Intergalactic Medium. The first period, which we call the Cosmic Dawn, saw the formation of the first stars and accreting black holes, which changed the quantum state of the still neutral Intergalactic Medium. The second period, known as the Epoch of Reionization, is the one during which large areas between the galaxies were photo-ionized by the radiation produced in galaxies and which ended when the Intergalactic Medium had become completely ionized.Observations of the redshifted 21-cm line with SKA will provide a new and unique window on the entire period of Cosmic Dawn and Reionization. The signal is sensitive to the emergence of the first stellar populations, radiation from growing massive black holes and the formation of larger groups of galaxies and bright quasars. At the same time it maps the distribution of most of the baryonic matter in the Universe. The study of the redshifted 21cm line will teach us fundamental new things about the earliest phases of structure formation and cosmology. It even has the potential to lead to the discovery of new physical phenomena. Here we present an overview of the science questions that SKA-low can address, how we plan to tackle these questions and what this implies for the basic design of the telescope.The redshifted 21cm signal will be analyzed with different techniques, which each come with their own requirements for the SKA: (i) Tomography, (ii) power-spectra and higher-order statistics, (iii) hydrogen absorption, (iv) global/total-intensity signal. Whereas all precursors/pathfinders aim to study the signal statistically through its power spectrum, SKA will be able to image the neutral hydrogen distribution directly and its focus will therefore be more on tomograph...

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“…We chose the noise power spectrum given by Eq. (12) of Santos et al (2011), which models the resulting noise after the foregrounds were removed:…”

Section: Detectabilitymentioning

confidence: 99%

Distinctive rings in the 21 cm signal of the epoch of reionization

Vonlanthen

Semelin

Baek

et al. 2011

A&A

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Context. It is predicted that sources emitting UV radiation in the Lyman band during the epoch of reionization show a series of discontinuities in their Lyα flux radial profile as a consequence of the thickness of the Lyman-series lines in the primeval intergalactic medium. Through unsaturated Wouthuysen-Field coupling, these spherical discontinuities are also present in the 21 cm emission of the neutral IGM. Aims. We study the effects that these discontinuities have on the differential brightness temperature of the 21 cm signal of neutral hydrogen in a realistic setting that includes all other sources of fluctuations. We focus on the early phases of the epoch of reionization, and we address the question of the detectability by the planned Square Kilometre Array (SKA). Such a detection would be of great interest because these structures could provide an unambiguous diagnostic tool for the cosmological origin of the signal that remains after the foreground cleaning procedure. These structures could also be used as a new type of standard rulers. Methods. We determine the differential brightness temperature of the 21 cm signal in the presence of inhomogeneous WouthuysenField effect using simulations that include (hydro)dynamics as well as ionizing and Lyman lines 3D radiative transfer with the code LICORICE. We include radiative transfer for the higher-order Lyman-series lines and consider also the effect of backreaction from recoils and spin diffusivity on the Lyα resonance. Results. We find that the Lyman horizons are difficult to indentify using the power spectrum of the 21 cm signal but are clearly visible in the maps and radial profiles around the first sources of our simulations, if only for a limited time interval, typically Δz ≈ 2 at z ∼ 13. Stacking the profiles of the different sources of the simulation at a given redshift results in extending this interval to Δz ≈ 4. When we take into account the implementation and design planned for the SKA (collecting area, sensitivity, resolution), we find that detection will be a challenging task. It may be possible with a 10 km diameter for the core, but will be difficult with the currently favored design of a 5 km core.

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Probing the first galaxies with the Square Kilometer Array

Cited by 29 publications

References 56 publications

A tale of two sites – I. Inferring the properties of minihalo-hosted galaxies from current observations

A tale of two sites – I. Inferring the properties of minihalo-hosted galaxies from current observations

Reionization and the Cosmic Dawn with the Square Kilometre Array

Distinctive rings in the 21 cm signal of the epoch of reionization

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