tirthankar roy choudhury national centre for radio
TRANSCRIPT
![Page 1: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/1.jpg)
Reionization Physics
Tirthankar Roy ChoudhuryNational Centre for Radio AstrophysicsTata Institute of Fundamental Research
Pune
Frontiers in 21 cm CosmologyKodaikanal Solar Observatory, India
10 December 2018
0
![Page 2: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/2.jpg)
Studying the epoch of reionization
✼ ✽ ✾ ✶� ✶✁ ✶✂ ✁�
✶✽� ✶✄� ✶☎� ✶✆� ✶✶� ✾� ✼�
③ ✥
♥ ✥✭✝✞✟✠
Figure courtesy Raghunath Ghara
◮ universe getting ionized by the first stars
◮ aim is to study the neutral hydrogen fraction xHI(x, z) as it decreases from∼ 1 to ∼ 0
◮ get insights on the nature of the first stars
1
![Page 3: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/3.jpg)
Thomson scattering τel from CMB
τel = σT c
∫ z[t]
0
dt ne (1 + z)3
Planck Collaboration (2016)
2
![Page 4: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/4.jpg)
Thomson scattering τel from CMB
τel = σT c
∫ z[t]
0
dt ne (1 + z)3
Planck Collaboration (2016)
2
![Page 5: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/5.jpg)
Quasar absorption spectra at z & 6
Fan, Carilli & Keating (2006)
Fobs = Fcont e−τGP , τGP ∼(
xHI
10−5
)
3
![Page 6: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/6.jpg)
Data constrained models
Mitra, TRC & Ferrara (2015)
Constraints based on
◮ Planck15 data on τel
◮ quasar absorption line measurements at z . 6 (either ΓHI or 〈τeff〉)◮ prior on xHI at z ∼ 5.5 − 6 based on “dark pixel” fraction
McGreer, Mesinger & D’Odorico (2015)4
![Page 7: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/7.jpg)
Data constrained models
Mitra, TRC & Ferrara (2015)
◮ reionization starts at z ∼ 12 − 15
◮ 50% ionized at z ∼ 6 − 10
◮ large uncertainties at 7 . z . 104
![Page 8: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/8.jpg)
Other probes of reionization
◮ Galaxy luminosity function: uncertain escape fraction
◮ Quasar absorption spectra (damping wings/near zones): only a few quasarsknown till date
◮ IGM temperature: requires detailed modelling
◮ Lyman-α emitters (number density and clustering): systematics, modeldependent constraints
5
![Page 9: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/9.jpg)
21 cm line◮ Hydrogen 1s ground state split by the interaction between the electron spin
and the nuclear spin.
|↑ ↑〉1√2[|↑ ↓〉+ |↓ ↑〉]
|↓ ↓〉
1√2[|↑ ↓〉 − |↓ ↑〉]
unperturbed
1s
triplet
singlet
ν = 1420 MHz, λ = 21 cm
Line transition =⇒ a transition originating at z will be observed at a frequencyνobs = 1420/(1 + z) MHz.
◮ It is a magnetic dipole transition, with transition probabilityA21 = 2.85 × 10−15 s−1 =⇒ an atom in the upper level is expected to make adownward transition once in 107 yr.For Lyα transition, the corresponding coefficient is A21 ≈ 6 × 108 s−1.
6
![Page 10: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/10.jpg)
The 21 cm signal
Figure from Zaroubi (2013)
CMBRHIResultant
The signal: δIν ∝ ρHI
(
1 − TCMB
Tspin
)
∝ ρHI (if Tspin ∼ Tgas ≫ TCMB)
7
![Page 11: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/11.jpg)
Global 21 cm signature
δTb ∝ Ts − TCMB(z)
Ts
ρHI
T−1s =
T−1CMB + xcT
−1k
+ xαT−1k
1 + xc + xα
Pritchard & Loeb (2012)
8
![Page 12: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/12.jpg)
Recent detection of the global 21 cm signal
Bowman et al (2018)9
![Page 13: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/13.jpg)
Consistent with standard calculations?
Bowman et al (2018)
Pritchard & Loeb (2012)
δTb = 0.023 K xHI
(
Ts − TCMB(z)
Ts
)
10
![Page 14: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/14.jpg)
Reionization model ingredients
√Formation of (dark matter) haloes:Analytical: Press-Schechter/Sheth-Tormen formalism
Simulations: DM only N-body codes
11
![Page 15: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/15.jpg)
Reionization model ingredients
√Formation of (dark matter) haloes:Analytical: Press-Schechter/Sheth-Tormen formalism
Simulations: DM only N-body codes
◮ Photon production nγ
11
![Page 16: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/16.jpg)
Reionization model ingredients
√Formation of (dark matter) haloes:Analytical: Press-Schechter/Sheth-Tormen formalism
Simulations: DM only N-body codes
◮ Photon production nγ
× Galaxy/star formation: cooling, fragmentation,feedback (radiative, mechanical, chemical)
11
![Page 17: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/17.jpg)
Reionization model ingredients
√Formation of (dark matter) haloes:Analytical: Press-Schechter/Sheth-Tormen formalism
Simulations: DM only N-body codes
◮ Photon production nγ
× Galaxy/star formation: cooling, fragmentation,feedback (radiative, mechanical, chemical)√Radiation from stars: population synthesis.
11
![Page 18: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/18.jpg)
Reionization model ingredients
√Formation of (dark matter) haloes:Analytical: Press-Schechter/Sheth-Tormen formalism
Simulations: DM only N-body codes
◮ Photon production nγ
× Galaxy/star formation: cooling, fragmentation,feedback (radiative, mechanical, chemical)√Radiation from stars: population synthesis.
× Escape of photons fesc: neutral hydrogen withinthe host galaxy
11
![Page 19: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/19.jpg)
Reionization model ingredients
√Formation of (dark matter) haloes:Analytical: Press-Schechter/Sheth-Tormen formalism
Simulations: DM only N-body codes
◮ Photon production nγ
× Galaxy/star formation: cooling, fragmentation,feedback (radiative, mechanical, chemical)√Radiation from stars: population synthesis.
× Escape of photons fesc: neutral hydrogen withinthe host galaxy
× Radiative transfer in the IGM: evolution ofionization frontsSimulations, semi-numerical, analytical
11
![Page 20: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/20.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 21: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/21.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 22: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/22.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 23: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/23.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 24: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/24.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 25: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/25.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 26: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/26.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12
![Page 27: Tirthankar Roy Choudhury National Centre for Radio](https://reader030.vdocuments.net/reader030/viewer/2022013009/61ce013d3136e2776167500f/html5/thumbnails/27.jpg)
Hydrogen reionization by stars
N-body simulations (GADGET) + Semi-numerical radiative transferTRC, Haehnelt & Regan (2009)
Figure courtesy Aditya Chowdhury
12