category
stringclasses 4
values | question
stringlengths 30
247
| choices.A
stringlengths 1
128
| choices.B
stringlengths 1
138
| choices.C
stringlengths 1
162
| ideal
stringclasses 3
values | reference
stringlengths 0
69
| reason
stringlengths 0
151
|
|---|---|---|---|---|---|---|---|
theory
|
Ionospheric refraction increases the zenith angle of incoming radio waves in the frequency range relevant to EoR as they pass through the a homogeneous F-layer of the ionosphere.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/503/1/344/6145010
|
The F-layer refraction bends the signal towards the zenith as it passes through the F-layer, decreasing the zenith angle.
|
theory
|
In the absence of X-ray heating and ionization, The 21-cm signal during the cosmic dawn or EoR is sensitive to the details of the IMF and can probe the typical mass of stars if it is dominated by stars heavier than 20 solar masses.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/516/1/841/6648845?login=true
| |
theory
|
Global 21-cm absorption feature during cosmic dawn/ EoR becomes deeper with increasing x-ray emissivity.
|
yes
|
no
|
dunno
|
B
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
|
Increasing x-ray emissivity heats IGM, making the difference to the 21-cm spin temperature smaller and the absorption feature shallower.
|
theory
|
Global 21-cm absorption feature during cosmic dawn/ EoR becomes deeper with increasing lyman-alpha emissivity.
|
yes
|
no
|
dunno
|
A
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
|
Increased Lyman-alpha emissivity enhances the Wouthuysen-Field effect, coupling the spin temperature to the cold gas, deepening the absorption feature.
|
experiment
|
The REACH global 21-cm experiment uses polynomials to fit the astrophysical foregrounds
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/506/2/2041/6307526?login=true
|
It uses a sophisticated sky division model based on spectral index.
|
theory
|
In 21-cm cosmology, which process strongly couples the spin and kinetic temperatures?
|
Compton scattering
|
Wouthuysen-Field effect
|
collisional coupling
|
B
|
https://ieeexplore.ieee.org/document/4065250
| |
theory
|
At redshift 300, the gas kinetic temperature decreases more slowly than the radio background temperature.
|
yes
|
no
|
dunno
|
B
|
The gas kinetic temperature decreases adiabatically as (1+z)^2, while the radio background temperature decreases as (1+z); it decreases faster.
|
|
theory
|
What is the dominant heating mechanism until around redshift 150?
|
Compton scattering
|
Wouthuysen-Field effect
|
X-ray heating
|
A
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
theory
|
At which redshift does Compton heating become ineffective at coupling the gas kinetic temperature to the radio background temperature?
|
50
|
100
|
150
|
C
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
theory
|
What is the primary astrophysical mechanism that heats the intergalactic medium (IGM) during the cosmic dawn?
|
X-ray heating
|
Lyman-alpha heating
|
Cosmic ray heating
|
A
|
https://iopscience.iop.org/article/10.1086/323691
| |
theory
|
It is generally assumed that the Universe was reionised by UV photons, but X-rays could potentially fully reionise the Universe.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/426/2/1349/974573
|
Chandra observations place limits on this contribution of X-ray to reionisation.
|
theory
|
The 21-cm signal is observable in emission during the early stages of reionisation before significant heating.
|
yes
|
no
|
dunno
|
B
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
|
Before significant heating, the spin temperature is coupled to the CMB temperature, making the 21-cm signal observable in absorption.
|
theory
|
Which radiation background is responsible for the coupling of the spin temperature before reionisation starts?
|
cosmic microwave background
|
X-ray radiation
|
Lyman-alpha radiation
|
C
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
theory
|
The Wouthuysen–Field effect is important during the dark ages before the formation of the first stars.
|
yes
|
no
|
dunno
|
B
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
|
The Wouthuysen–Field effect is present when there are lyman-alpha photons available, which is after the first stars form.
|
theory
|
The 21-cm photons are created from the radiative cascade of an electron from the n=2 level back to one of the hyperfine levels of the n=1 ground state.
|
yes
|
no
|
dunno
|
B
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
|
This statement describes the Wouthuysen–Field effect not how 21-cm photons are created.
|
theory
|
When the magnetic field is perpendicular to the line of sight, the electron undergoes circular motion about the magnetic field lines, causing its acceleration vector to rotate with time, resulting in circularly polarised radiation to the observer.
|
yes
|
no
|
dunno
|
B
|
This happens when they are parallel.
|
|
theory
|
What is the angle between the magnetic field and the line of sight that would result in purely circularly polarised radiation?
|
0 degrees
|
45 degrees
|
90 degrees
|
A
| ||
theory
|
Which radiation is the foreground dominated by in the frequency range relevant to 21-cm cosmology?
|
cosmic microwave background
|
synchrotron radiation
|
dust free-free emission
|
B
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
experiment
|
What is the statistical approach adopted in the REACH global 21-cm experiment?
|
Bayesian inference
|
frequentist statistics
|
neither
|
A
|
https://academic.oup.com/mnras/article/506/2/2041/6307526
| |
experiment
|
In a Bayesian framework, which quantity is used to compare different models?
|
likelihood
|
Bayesian evidence
|
posterior probability distribution
|
B
|
https://academic.oup.com/mnras/article/506/2/2041/6307526
| |
theory
|
What is the spin temperature of neutral hydrogen defined by the kinetic temperature of hydrogen atomsin the context of 21-cm cosmology?
|
the temperature characterising the relative population of the hyperfine states
|
the kinetic temperature of hydrogen atoms
|
the temperature of the cosmic microwave background
|
A
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
theory
|
Which of the following statements provides the most precise description of the Wouthuysen-Field mechanism
|
The absorption of Lyman-alpha photons heats the hydrogen gas directly, coupling its kinetic temperature to the spin temperature.
|
Lyman-alpha photons yield a thermal equilibrium between the 21-cm spin temperature and the temperature of the Lyman-alpha radiation field.
|
The repeated scattering of Lyman-alpha photons repopulate the hydrogen hyperfine levels, driving the 21-cm spin temperature to the kinetic temperature of the gas.
|
C
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
theory
|
When does Lyman-alpha coupling become effective?
|
when Wouthuysen-Field coupling rate exceeds the Hubble expansion rate
|
when the first stars form and emit Lyman-alpha radiation
|
when the universe becomes dominated by dark energy
|
A
|
https://academic.oup.com/mnras/article/367/1/259/1018616
| |
theory
|
Why is the 21-cm line unobservable during the dark ages even though neutral hydrogen is abundant
|
the spin temperature is coupled to the CMB temperature
|
the optical depth is too high
|
hydrogen is too cold to emit radiation
|
A
| ||
theory
|
Cross-correlating 21-cm experiments with galaxy surveys does not provide significant constraints on which of the following?
|
the total matter density of the universe,
|
the escape fraction of ionising photons from the observed galaxies
|
the astrophysical bias of the observed galaxy population
|
A
| ||
theory
|
What is the statistical weight ratio of the hydrogen hyperfine levels at n=1?
|
1
|
2
|
3
|
C
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
| |
theory
|
21-cm forest refers to the appearance of lines from regions of neutral gas at different distances to the CMB.
|
yes
|
no
|
dunno
|
B
|
https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901
|
It is with respect to the radio source, not the CMB.
|
theory
|
The amplitude of the EDGES global 21-cm profile can be explained by warm dark matter.
|
yes
|
no
|
dunno
|
B
| ||
theory
|
In the warm dark matter scenario, the onset of star formation happens earlier than in the cold dark matter.
|
yes
|
no
|
dunno
|
B
| ||
theory
|
In the warm dark matter scenario, the Wouthuysen-Field coupling saturates earlier than in the lambda-CDM scenario.
|
yes
|
no
|
dunno
|
B
| ||
theory
|
Double reionisation is likely.
|
yes
|
no
|
dunno
|
B
| ||
theory
|
Cosmic ray heating creates 21-cm signatures on larger spacial scales compared to X-ray heating.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/526/3/4262/7291942
|
Cosmic ray heating of the IGM is short-ranged
|
experiment
|
The shape of the EDGES global 21-cm absorption profile cannot be recreated in models even with several heating contributions.
|
yes
|
no
|
dunno
|
B
| ||
experiment
|
What does foreground wedge in the delay space refer to?
|
the region where reionisation occurs
|
an interferometric instrumental artifact
|
a region contaminated by the foregrounds
|
C
| ||
experiment
|
Which methodologies of calibration do global 21-cm experiments use?
|
direction dependent
|
direction independent
|
both
|
B
| ||
experiment
|
For 21-cm signal observations after reionisation, aiming for spatial fluctuations at the scale of ionised bubbles is appropriate.
|
yes
|
no
|
dunno
|
B
|
https://iopscience.iop.org/article/10.1088/1538-3873/ab5bfd
| |
instrumentation
|
How many calibrators are there in the global 21-cm experiment REACH?
|
4
|
8
|
12
|
C
|
https://link.springer.com/article/10.1007/s10686-024-09975-3
| |
instrumentation
|
SKA-low antenna response is sufficiently smooth to recover the EoR signal through statistical methods.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/469/3/2662/3605382
|
Mutual coupling between antennas within a station makes this untrue.
|
instrumentation
|
SKA-low antenna mutual coupling can be resolved by randomising the position and direction of the antennae.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/538/1/31/8010856
| |
theory
|
Timing of Lyman-alpha coupling is well constrained by observations of high-redshift quasars, galaxies, and the CMB.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/506/4/5479/6325554
| |
theory
|
In the context of 21-cm cosmology, Lyman-alpha photons would travel further on a larger scale when multiple scattering is included.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/506/4/5479/6325554
| |
theory
|
In most scenarios (except in cases like with weak X-ray heating), multiple scattering plays an important role at lower redshift where Lyman-alpha coupling saturates and the 21-cm fluctuations are dominated by heating processes.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/506/4/5479/6325554
|
At higher redshift.
|
theory
|
Lower X-ray efficiency would make reionisation more homogeneous.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/464/3/3498/2514572?login=false
|
Higher X-ray efficiency.
|
instrumentation
|
In 21-cm experiments, impedance mismatch between the low noise amplifiers and optical transmitters causes power from the foreground signals to appear at lower delays, potentially contaminating the EoR window.
|
yes
|
no
|
dunno
|
B
|
https://academic.oup.com/mnras/article/533/3/2876/7745848
|
it would appear at higher delays, not lower delays.
|
experimentation
|
In a delay power spectrum for 21-cm experiments, which k-modes should exhibit the lowest foreground-to-signal ratio?
|
those above the horizon limit
|
those below the horizon limit
|
there is no difference
|
A
|
https://academic.oup.com/mnras/article/533/3/2876/7745848
| |
instrumentation
|
What data types are correlation saved to in measurement set in radio astronomy?
|
COMPLEX*8
|
COMPLEX*16
|
COMPLEX*32
|
A
| ||
theory
|
Other parameters being the same, decreasing density of matter will increase the width of the 21-cm absorption signal.
|
yes
|
no
|
dunno
|
B
|
https://articles.adsabs.harvard.edu/pdf/1977SvAL....3..155V
|
YAML Metadata
Warning:
empty or missing yaml metadata in repo card
(https://huggingface.co/docs/hub/datasets-cards)
21cmQA is an evaluation dataset, designed to serve as a benchmark for RAG applications to 21-cm cosmology.
- Downloads last month
- 15