The document discusses the cosmic dawn and reionization period in the early universe. It describes the evolution from the dark ages after recombination to the epoch of reionization around z=6-20. Key aspects discussed include understanding the sources and sinks of ionizing photons that drove reionization, and challenges in modeling this period due to the large parameter space and scales involved, from single stars to the entire universe. Seminumerical simulations are presented as an efficient method to model reionization and predict 21cm signals.
The muse 3_d_view_of_the_hubble_deep_field_southSérgio Sacani
Artigo mostra como foram as observações feitas com o MUSE, o novo instrumento do VLT do campo profundo do Hubble. Além de descobrir 20 novos objetos, o MUSE conseguiu medir as propriedades das galáxias e até representar as mais próximas em 3 dimensões.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
The muse 3_d_view_of_the_hubble_deep_field_southSérgio Sacani
Artigo mostra como foram as observações feitas com o MUSE, o novo instrumento do VLT do campo profundo do Hubble. Além de descobrir 20 novos objetos, o MUSE conseguiu medir as propriedades das galáxias e até representar as mais próximas em 3 dimensões.
Observed glacier and volatile distribution on Pluto from atmosphere–topograph...Sérgio Sacani
Pluto has a variety of surface frosts and landforms as well as a
complex atmosphere1. There is ongoing geological activity related
to the massive Sputnik Planum glacier, mostly made of nitrogen (N2)
ice mixed with solid carbon monoxide and methane2, covering the
4-kilometre-deep, 1,000-kilometre-wide basin of Sputnik Planum1,3
near the anti-Charon point. The glacier has been suggested to arise
from a source region connected to the deep interior, or from a sink
collecting the volatiles released planetwide1. Thin deposits of N2
frost, however, were also detected at mid-northern latitudes and
methane ice was observed to cover most of Pluto except for the
darker, frost-free equatorial regions2. Here we report numerical
simulations of the evolution of N2, methane and carbon monoxide
on Pluto over thousands of years. The model predicts N2 ice
accumulation in the deepest low-latitude basin and the threefold
increase in atmospheric pressure that has been observed to occur
since 19884–6. This points to atmospheric–topographic processes as
the origin of Sputnik Planum’s N2 glacier. The same simulations also
reproduce the observed quantities of volatiles in the atmosphere and
show frosts of methane, and sometimes N2, that seasonally cover the
mid- and high latitudes, explaining the bright northern polar cap
reported in the 1990s7,8 and the observed ice distribution in 20152.
The model also predicts that most of these seasonal frosts should
disappear in the next decade.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
2015-02-20: Review of Hargreaves [1969]: Auroral Absorption of HF Radio Waves...inverseuniverse
A review of the first decade of riometry with an eye towards modern implementations (e.g., the IRIS riometer and the Automated Geophysical Observatories in Antarctica).
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
2015-02-20: Review of Hargreaves [1969]: Auroral Absorption of HF Radio Waves...inverseuniverse
A review of the first decade of riometry with an eye towards modern implementations (e.g., the IRIS riometer and the Automated Geophysical Observatories in Antarctica).
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Galaxy dynamics and the mass density of the universeSérgio Sacani
Dynamical evidence accumulated over the
past 20 years has convinced astronomers that luminous matter
in a spiral galaxy constitutes no more than 10% of the mass of
a galaxy. An additional 90% is inferred by its gravitational
effect on luminous material. Here I review recent observations
concerning the distribution of luminous and nonluminous
matter in the Milky Way, in galaxies, and in galaxy clusters.
Observations of neutral hydrogen disks, some extending in
radius several times the optical disk, confirm that a massive
dark halo is a major component of virtually every spiral. A
recent surprise has been the discovery that stellar and gas
motions in ellipticals are enormously complex. To date, only for
a few spheroidal galaxies do the velocities extend far enough to
probe the outer mass distribution. But the diverse kinematics
of inner cores, peripheral to deducing the overall mass distribution,
offer additional evidence that ellipticals have acquired
gas-rich systems after initial formation. Dynamical results are
consistent with a low-density universe, in which the required
dark matter could be baryonic. On smallest scales of galaxies
[10 kiloparsec (kpc); H. = 50 kmsec'lmegaparsec'11 the
luminous matter constitutes only 1% of the closure density. On
scales greater than binary galaxies (i.e., .100 kpc) all systems
indicate a density -10% of the closure density, a density
consistent with the low baryon density in the universe. If
large-scale motions in the universe require a higher mass
density, these motions would constitute the first dynamical
evidence for nonbaryonic matter in a universe of higher
density.
Phase problem sorts out all the problem which occurs after the x-ray crystallization data. In this way, we have to find out maximum values of phases and amplitude both to give the better picture of electron density map and later it is verified and validated upto maximum refined 3-D structure.
I am Hannah M . I am an Electromagnetism Assignment expert at eduassignmenthelp.com. I hold a Ph.D. in Statistics, from Kean University, USA. I have been helping students with their homework for the past 8 years. I solve assignments related to Electromagnetism.
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Invited Seminar presented at the VIA Forum Astroparticle Physics Forum COSMOVIA
21 March 2020
http://viavca.in2p3.fr/2010c_o_s_m_o_v_i_a__forum_sd24fsdf4zerfzef4ze5f4dsq34sdteerui45788789745rt7yr68t4y54865h45g4hfg56h45df4h86d48h48t7uertujirjtiorjhuiofgrdsqgxcvfghfg5h40yhuyir/viewtopic.php?f=73&t=3705&sid=c56cbf76f87536fc4c3ff216d9edaba2
Author: O.M. Lecian
Speaker: O.M. Lecian
Abstract: The LHAASO experiment is aimed at detecting highly-energetic particles of cosmological origin within a large
range of energies.
The sensitivity of the experimental apparatus can within the frameworks of statistical fluctuations of the
background.
Acceleration and lower-energy particles can be analyzed.
The anisotropy mass composition of cosmic rays can analytically described.
The LHAASO Experiment is also suited for detecting particles of cosmological origin originated from the breach
(and/or other kinds of modifications) of particle theories paradigms comprehending other symmetry groups.
Some physical implications of anisotropies can be looked for.
The study of anisotropy distribution for particles of cosmological origin as well as the anisotropies of their velocities
both in the case of a flat Minkowskian background as well as in the case of curved space-time can be investigated,
as far as the theoretical description of the cross-section is concerned, as well as for the theoretical expressions of
such quantities to be analyzed.
The case of a geometrical phase of particles can be schematized by means of a geometrical factor.
Particular solutions are found under suitable approximations.
A comparison with the study of ellipsoidal galaxies is achieved.
The case of particles with anisotropies in velocities falling off faster than dark matter (DM) is compared.
The study of possible anisotropies in the spatial distribution of cosmological particles can therefore be described
also deriving form the interaction of cosmic particles with the gravitational field, arising at quantum distances, at
the semiclassical level and at the classical scales, within the framework of the proper description of particles
anisotropies properties.
The shadow _of_the_flying_saucer_a_very_low_temperature_for_large_dust_grainsSérgio Sacani
Os astrónomos usaram o ALMA e os telescópios do IRAM para fazer a primeira medição direta da temperatura dos grãos de poeira grandes situados nas regiões periféricas de um disco de formação planetária que se encontra em torno de uma estrela jovem. Ao observar de forma inovadora um objeto cujo nome informal é Disco Voador, os astrónomos descobriram que os grãos de poeira são muito mais frios do que o esperado: -266º Celsius. Este resultado surpreendente sugere que os modelos teóricos destes discos precisam de ser revistos.
Uma equipa internacional liderada por Stephane Guilloteau do Laboratoire d´Astrophysique de Bordeaux, França, mediu a temperatura de enormes grãos de poeira que se encontram em torno da jovem estrela 2MASS J16281370-2431391 na região de formação estelar Rho Ophiuchi, a cerca de 400 anos-luz de distância da Terra.
Esta estrela encontra-se rodeada por um disco de gás e poeira — chamado disco protoplanetário, uma vez que se encontra na fase inicial da formação de um sistema planetário. Este disco é visto de perfil quando observado a partir da Terra e a sua aparência em imagens no visível levou a que se lhe desse o nome informal de Disco Voador.
Os astrónomos utilizaram o ALMA para observar o brilho emitido pelas moléculas de monóxido de carbono no disco da 2MASS J16281370-2431391. As imagens revelaram-se extremamente nítidas e descobriu-se algo estranho — em alguns casos o sinal recebido era negativo. Normalmente um sinal negativo é fisicamente impossível, mas neste caso existe uma explicação, que leva a uma conclusão surpreendente.
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1. Tuning your radio to
reionization and the cosmic dawn
Andrei Mesinger
Scuola Normale Superiore, Pisa
2. Cosmic History
z
~
6
tage
~
1
Gyr
z~1100
tage
~
0.4
Myr
Reioniza5on
Dark
Ages
Recombina5on
HII
z
~
20
tage
~
150
Myr
z
=
0
tage ~ 14 Gyr
HI
3. Cosmic Dawn and Reionization
z
~
6
tage
~
1
Gyr
z~1100
tage
~
0.4
Myr
Reioniza5on
Dark
Ages
Recombina5on
HII
z
~
20
tage
~
150
Myr
z
=
0
tage ~ 14 Gyr
HI
Bulk of our light cone: observational future!
4. Sources Sinks
Understanding reionization means understanding sources and sinks
of ionizing photons.
simple analytic model for global evolution (e.g. Barkana Loeb 2004):
e ∼ 1 – 3.
SNe Rates
och, and hence
re unknown at
SOs offer sug-
onization was
quite extended
SFR and SNR
However, even
elow) scenario
n feature is as
not be smooth,
uch transitions
fferent sources
er 2003).
h and shape of
e filling factor
small, vulner-
mal state of the
SNRs, in each
es
nizing sources
formation with
es
are still forming at such late stages are probably not going to be
very near the large overdensities which were likely to be ion-
ized during earlier stages (Furlanetto Oh 2005; Ricotti et al.
2002). We also require (4) to be reasonably high (i.e. that the
dominant ionizing sources appear around the same time, with-
out too much cosmic scatter). Below, we further quantify such
a scenario.
One can get a sense of the possible shapes of the reionization
feature through an estimate of the evolution of the filling factor
of ionized regions, FHII(z), (c.f. Barkana Loeb 2001; Haiman
Holder 2003):
dFHII(z)
dt
= ∗ fesc
Nph/b
0.76
dFcol( Mmin(z),z)
dt
αBC n0
H (1!z)3
FHII .
(7)
Here fesc is the escape fraction of ionizing photons, Nph/b is
the number of ionizing photons per baryon emitted by a typical
source, Fcol( M,z) is the fraction of baryons that reside in col-
lapsed halos with a total mass greater than M at redshift z, αB is
the hydrogen case B recombination coefficient, C ≡ n2
H / nH
2
is the clumping factor, and n0
H is the current hydrogen number
density. The first term on the right hand side accounts for “new”
ionizations contributing to the growth of the HII regions and the
last term on the right hand side accounts for “old” reionizations
due to recombinations inside the HII region. This equation is
a very rough approximation, as it does not include feedback
effects, light travel time, and it does not accurately model the
period when bubbles start overlapping (i.e. FHII(z) ∼ 1). How-
ever, it can suffice for the crude estimates we are making here.
In Figure 9, we plot FHII(z) for several values of Mmin(z) cor-
sources
sinks
Even such an overly-simplified model has several unknown,
redshift and spatial dependent parameters:
nant ionizing sources appear around the same time,
oo much cosmic scatter). Below, we further quantify
nario.
ne can get a sense of the possible shapes of the reioniz
re through an estimate of the evolution of the filling f
nized regions, FHII(z), (c.f. Barkana Loeb 2001; Ha
older 2003):
I(z)
= ∗ fesc
Nph/b
0.76
dFcol( Mmin(z),z)
dt
αBC n0
H (1!z)
fesc is the escape fraction of ionizing photons, Nph
umber of ionizing photons per baryon emitted by a ty
ce, Fcol( M,z) is the fraction of baryons that reside in
d halos with a total mass greater than M at redshift z,
2
ill forming at such late stages are probably not going to be
near the large overdensities which were likely to be ion-
during earlier stages (Furlanetto Oh 2005; Ricotti et al.
). We also require (4) to be reasonably high (i.e. that the
nant ionizing sources appear around the same time, with-
oo much cosmic scatter). Below, we further quantify such
nario.
e can get a sense of the possible shapes of the reionization
re through an estimate of the evolution of the filling factor
nized regions, FHII(z), (c.f. Barkana Loeb 2001; Haiman
lder 2003):
(z)
= ∗ fesc
Nph/b
0.76
dFcol( Mmin(z),z)
dt
αBC n0
H (1!z)3
FHII .
(7)
fesc is the escape fraction of ionizing photons, Nph/b is
umber of ionizing photons per baryon emitted by a typical
e, Fcol( M,z) is the fraction of baryons that reside in col-
d halos with a total mass greater than M at redshift z, αB is
ydrogen case B recombination coefficient, C ≡ n2
H / nH
2
0
ough small halos at that epoch to act as signposts for
tion. From Figure 6, we see that this a reasonable as-
n, especially given the fact that most small halos which
forming at such late stages are probably not going to be
ar the large overdensities which were likely to be ion-
ing earlier stages (Furlanetto Oh 2005; Ricotti et al.
We also require (4) to be reasonably high (i.e. that the
nt ionizing sources appear around the same time, with-
much cosmic scatter). Below, we further quantify such
io.
an get a sense of the possible shapes of the reionization
hrough an estimate of the evolution of the filling factor
ed regions, FHII(z), (c.f. Barkana Loeb 2001; Haiman
er 2003):
= ∗ fesc
Nph/b
0.76
dFcol( Mmin(z),z)
dt
αBC n0
H (1!z)3
FHII .
(7)
c is the escape fraction of ionizing photons, Nph/b is
ber of ionizing photons per baryon emitted by a typical
Fcol( M,z) is the fraction of baryons that reside in col-
alos with a total mass greater than M at redshift z, αB is
2 2
ure 6, we see that this a reasonable as-
ven the fact that most small halos which
late stages are probably not going to be
rdensities which were likely to be ion-
es (Furlanetto Oh 2005; Ricotti et al.
(4) to be reasonably high (i.e. that the
ces appear around the same time, with-
catter). Below, we further quantify such
of the possible shapes of the reionization
mate of the evolution of the filling factor
(z), (c.f. Barkana Loeb 2001; Haiman
dFcol( Mmin(z),z)
dt
αBC n0
H (1!z)3
FHII .
(7)
fraction of ionizing photons, Nph/b is
photons per baryon emitted by a typical
most small halos which
robably not going to be
were likely to be ion-
Oh 2005; Ricotti et al.
ably high (i.e. that the
d the same time, with-
e further quantify such
apes of the reionization
tion of the filling factor
Loeb 2001; Haiman
)
αBC n0
H (1!z)3
FHII .
(7)
zing photons, Nph/b is
- escape fraction of ionizing photons
- mass efficiency of conversion of gas to stars
- mean # of ionizing photons per stellar baryon
- minimum halo mass to host ionizing sources
- clumping factor (measurement of the average recombination rate)
Many groups are working on modeling such parameters!
5. Challenges
~ FoV of 21cm
interferometers
• Dynamic range required is enormous: single star -- Universe
• We know next to nothing about high-z -- ENORMOUS parameter space to explore
S1 S3 S4S2
z=7.7z=7.3z=8.7
Figure 3. Comparison of four radiative transfer simulations post-processed on the same density field, but using different source prescriptions parametrized by
˙N(m) = α(m) m. The white regions are ionized and the black are neutral. The left-hand panel, left centre panel, right centre panel and right-hand panels are,
respectively, cuts through Simulations S2 (α ∝ m−2/3), S1 (α ∝ m0), S3 (α ∝ m2/3) and S4 (α ∝ m0, but only haloes with m 4 × 1010 M host sources). For
the top panels, the volume-ionized fraction is ¯xi,V ≈ 0.2 (the mass-ionized fraction is ¯xi,M ≈ 0.3) and z = 8.7. For the middle panels, ¯xi,V ≈ 0.5(xi,M ≈ 0.6)
and z = 7.7, and for the bottom panels, ¯xi,V ≈ 0.7(¯xi,M ≈ 0.8) and z = 7.3. Note that the S4 simulation outputs have the same ¯xi,M , but ¯xi,V that are typically
0.1 smaller than that of other runs. In S4, the source fluctuations are nearly Poissonian, resulting in the bubbles being uncorrelated with the density field
(¯xi,V ≈ ¯xi,M ). Each panel is 94 Mpc wide and would subtend 0.6 degrees on the sky.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1 10
RdP/dR
0.01
0.1
0.1 1 10
∆xx
2
k (h Mpc
-1
)
z = 7.3
0.01
0.1
∆xx
2
z = 7.7
0.01
0.1
∆xx
2
z = 8.7
!#$$$% !#$$%
x
HI
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
z = 5.00
xHI v = 0.10
1Mpc
94Mpc
2Gpc
Wise+ (2010)
McQuinn+ (2007)
Mesinger (2010)
6. Philosophy… how to approach the problem
scale
Hydrodynamical Numerical Simulations (+RT)
Seminumerical Simulations or
lower resolution large-scale numerical simulations
Seminumerical Simulations
or Analytic Estimates
Strategy #1:
7. Philosophy… how to approach the problem
Strategy #2:
Large scales/analytic models to generate
general, robust claims (true for large swaths
of parameter space)
make predictions match observations
(caution: interpretation is difficult; watch
out for degeneracies..)
8. DexM 21cmFAST
• Combines excursion-set approach with perturbation theory for efficient generation
of large-scale density, velocity, halo, ionization, radiation, 21cm brightness fields
• Portable and FAST! (if it’s in the name, it must be true…)
– A realization can be obtained in ~ minutes on a single CPU
– New parallelized version, optimized for parameter studies
• Run on arbitrarily large scales
• Vary many independent free parameters; cover wide swaths of parameter space
• Tested against state-of-the-art hydrodynamic cosmological simulations (Trac Cen
2007; Trac+ 2008)
• Publically available!
semi-numerical simulation (Mesinger Furlanetto 2007;
Mesinger, Furlanetto, Cen 2011)
Tools for modeling large-scale signal:
12. Ionization fields
Trac Cen (2007)
21cmFAST (Mesinger+ 2011)
Zahn+ (2010)
DexM (with halos;
Mesinger Furlanetto; 2007)
6
McQuinnetal.TracCenFFRT
X=0.25 X=0.51 X=0.72
z=8.49 z=7.56 z=7.11
MesingerFurlanetto
Fig. 1.— Comparison of ionization fields generated from four schemes: McQuinn et al., Trac Cen, MF07, and FFRT. The maps are
from the same slice (100 Mpc/h by 100 Mpc/h with depth of 0.4 Mpc/h) through the simulation box.
13. Redshift space distortions (sorry no pics)
nonlinear structure formation creates an asymmetric velocity gradient distribution
14. 21cm comparison (stay tuned…)
hydro+DM+RT
DexM (with halos)
21cmFAST (no halos)
~ 1 week on 1536 cores
~ few min on 1 core
100 Mpc/h
17. 21 cm line from neutral hydrogen
Hyperfine transition in the ground
state of neutral hydrogen produces
21cm line.
Predicted by van den Hulst when
Oort told him to find unknown
radio lines to study our galaxy
18. Now widely used to map the HI content of
nearby galaxies
Circinus Galaxy
ATCA HI image by B. Koribalski (ATNF, CSIRO), K. Jones, M. Elmouttie (University
of Queensland) and R. Haynes (ATNF, CSIRO).
19. Once upon a time, HI was much more abundant
z
~
6
z~1100
Recombina5on
HII
z
~
20
CMB backlight
z
=
0
HI
υ21~
70
MHz
υ21~
200
MHz
Redshifted 21cm signal.
tune radio to:
20. Once upon a time, HI was much more abundant
z
~
6
z~1100
Recombina5on
HII
CMB backlight
z
~
20
HI
υ21~
70
MHz
υ21~
200
MHz
Redshifted 21cm signal.
tune radio to:
LOFAR,
MWA,
PAPER,
21CMA,
GMRT
2nd gen: SKA
interferometer
21. What we learn: Cosmological 21cm Signal
neutral fraction
gas density
LOS velocity gradient
spin temperature
22. Cosmological 21cm Signal
Powerful probe:
Astrophysics
Has something everyone can enjoy!
The trick is to disentangle the components:
• separation of epochs and/or
• accurate, efficient modeling (21cmFAST)
Cosmology
25. Power of the pre-reionization thermal
evolution to constrain astro and cosmo
spin temperature:
fields, using excursion set formalism to estimate the mean num-
ber of sources inside spherical shells corresponding to some higher
redshift. As discussed above, bypassing the halo field allows the
code to be faster, with modest memory requirements. Below we go
through our formalism in detail.
The spin temperature can be written as (e.g. Furlanetto et al.
2006):
T−1
S =
T−1
γ + xαT−1
α + xcT−1
K
1 + xα + xc
(5)
where TK is the kinetic temperature of the gas, and Tα is the color
temperature, which is closely coupled to the kinetic gas tempera-
ture, Tα ≈ TK (Field 1959). There are two coupling coefficients
in the above equation. The collisional coupling coefficient can be
written as:
xc =
0.0628 K
A10Tγ
h
nHIκHH
1−0(TK) + neκeH
1−0(TK) + npκpH
1−0(TK)
i
,
(6)
Tγ – temperature of the CMB
TK – gas kinetic temperature
Tα – color temperature ~ TK
the spin temperature interpolates between Tγ and TK
Any source of heat could leave an imprint:
-X-rays, shocks, DM annihilation, cosmic strings…
28. But 21cm also probes cosmology
1) “clean” epochs where cosmo signal dominates à Dark
Ages z 40
!#$%'($)*+,-.$
/0,.$1,12-3$
45,$
29. But 21cm also probes cosmology
2) Models which suppress small-scale power, like WDM
result in a dearth of low mass galaxies
30. But 21cm also probes cosmology
3) Heat input (e.g. DM annihilations)
FIG. 3: Evolution of the 21cm power at k = 0.1 h Mpc−1
.
Evoli+, in prep
31. Conclusions
• Cosmological 21cm signal is very rich in information, containing both
cosmological and astrophysical components.
• The range of scales and unknown parameter space is enormous! We need (i)
bottom-up modeling; (ii) parameter space explorations
• SKA is great!
!#$%'($)*+,-.$
/0,.$1,12-3$
45,$