Analysis of differential observations of the cosmological radio background: studying the SZE-21cm

Transcription

1 Analysis of differential observations of the cosmological radio background: studying the SZE-21cm Charles Mpho Takalana Supervisor: Prof Sergio Colafrancesco University of the Witwatersrand November 28, 2017 Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

2 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

3 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

4 Probes for the evolution of the universe Our knowledge and understanding of the early universe Evolution and Transition (Recombination DA EoR) harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

5 Probes for the evolution of the universe Our knowledge and understanding of the early universe Evolution and Transition (Recombination DA EoR) A suitable probe has to be identified harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

6 Probes for the evolution of the universe Our knowledge and understanding of the early universe Evolution and Transition (Recombination DA EoR) A suitable probe has to be identified Widely accepted probe is obsevation of the 21cm-background: Comes with Challenges: 21cm-background signal is faint compared to CMB (Furlanetto et al. 2006) Galactic and extragalactic foregrounds (Oliveira-Costa et al. 2008) Much larger compared to expected signal Possible solutions: Study the 21cm fluctuations (Barkana & Loeb 2005a) Measure the contrast between the 21cm signal and the bubbles of ionized plasma (Furlanetto et al. 2006) Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

7 Probes for the evolution of the universe Our knowledge and understanding of the early universe Evolution and Transition (Recombination DA EoR) A suitable probe has to be identified Widely accepted probe is obsevation of the 21cm-background: Comes with Challenges: 21cm-background signal is faint compared to CMB (Furlanetto et al. 2006) Galactic and extragalactic foregrounds (Oliveira-Costa et al. 2008) Much larger compared to expected signal Possible solutions: Study the 21cm fluctuations (Barkana & Loeb 2005a) Measure the contrast between the 21cm signal and the bubbles of ionized plasma (Furlanetto et al. 2006) Alternative solution: Differential observations using the SZE-21cm Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

8 Why the SZE-21cm? Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

9 Why the SZE-21cm? SZE-21cm observations can be carried out with radio interferometers, on and off target cosmic structures with hot plasma harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

10 Why the SZE-21cm? SZE-21cm observations can be carried out with radio interferometers, on and off target cosmic structures with hot plasma Differential observations are less affected by: Exact calibration of the observed intensity using external sources Large scale foregrounds, for low frequency studies (Colafrancesco et al., 2016) harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

11 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

12 The Sunyaev-Zel dovich Effect SZE-21cm, a specific form of the Sunyaev-Zeldovich effect (SZE) produced when photons of the 21cm background are inverse Compton (up-)scattered by electrons residing in hot plasma: Galaxy clusters Active radio galaxies Radio lobes Halos Figure 1: Credit: astro.uchicago.edu/sza/primer.html harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

13 The Sunyaev-Zel dovich Effect Figure 1: Credit: astro.uchicago.edu/sza/primer.html SZE-21cm, a specific form of the Sunyaev-Zeldovich effect (SZE) produced when photons of the 21cm background are inverse Compton (up-)scattered by electrons residing in hot plasma: Galaxy clusters Active radio galaxies Radio lobes Halos The SZE is redshift independent Measure clusters motions Used to measure properties of gas in clusters harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

14 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

15 The 21cm Cosmological Signal The 21 cm background was produced when neutral hydrogen emitted radiation due to spin-flip transitions (DA & EoR ) The signal we expect is weak compared to the foregrounds Separating signal from foregrounds, non-trivial To confirm any signal detection great understanding of 21cm signatures is required harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

16 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

17 The 21cm brightness temperature The observable 21cm differential brightness temperature: harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

18 The 21cm brightness temperature The observable 21cm differential brightness temperature: Public 21cm N-body Simulation code: Simfast21 (Santos et al., 2010, MNRAS) 21cmFAST (Mesinger et al., 2010, MNRAS) Figure 2: Sky averaged 21cm brightness temperature, δt b, from simulation used for work in this Talk harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

19 Formalism for the SZE-21cm applied to simulated data Modification to the CMB spectrum in terms of the Brightness temperature: δt b (ν) = c2 2kν δi(ν) 2 The CMB spectrum modified by effects during DA & EoR: Where: The SZE-21cm is: I 0,mod (ν) = I 0,st (ν) + δi(ν) I 0,st (ν) = 2 (kt0)3 (hc) 2 x 3 e x 1 I mod (ν) = I mod (ν) I 0,mod (ν) Where I mod (ν) is the spectral distortion at the cluster due to the SZE (For detailed derivation see: Colafrancesco et al., 2016, A&A) Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

20 Simulating the SZE-21cm: At 91.88MHz (z =14.46) Simulate 30Mpc 21cm temperature cubes Insert a 3Mpc radius SZE-Galaxy cluster Slice the cube towards and away from the cluster One contains the cluster signal and background, with Modification due to the thermal effects for thermal plasma at kt = 10 KeV and with τ of order 10 3 : ( ) ] θ T mod = T mod,0 [1 3β 2 + θ c Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

21 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

22 Foreground removal:at 91.88MHz (z =14.46) Consider an area away from the cluster The background Detection of the 21cm signal depends on accurate foreground removal methods 21cm background fluctuations are of order , Bad for SZE-21cm signal extraction Removal of bright sources and residual error subtraction The SZE-21cm is the modification of the CMB for easy detection fluctuations of order 10 5 similar to the CMB primordial fluctuations harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

23 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

24 The SZE-21cm: At 91.88MHz (z =14.46) Take two signals (A + B and B) (A+B): SZE-21cm Signal with foreground B: foreground/background SZE-21cm = (A+B) - B = A Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

25 The SZE-21cm: (15-180MHz) The SZE-21cm from difference images (15-180MHz) Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

26 The SZE-21cm: (15-180MHz) Fluxes for SZE-21cm I mod and the non-modified CMB I st compared with SKA-50%, SKA1-low & SKA2 sensitivities for 100kHz bandwidth, 1000 hrs integration for 2 polarizations Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

27 Outline 1 Introduction 2 The SZE-21cm 3 The 21cm Cosmological Signal 4 Simulations of the 21cm Signal 5 Foregrounds and Fluctuations 6 Results 7 Conclusion harles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22

28 Conclusion Differential techniques are ideal for probing the DA and EoR The SZE-21cm spectrum will help us obtain information on physical mechanisms producing the modification SZE-21cm is Observable : MHz HERA MHz SKA1-low: MHz Other ongoing work for low frequency radio images show that the Image differencing technique can enhanced certain features, obtaining better signal to noise Charles Mpho Takalana (University of the Witwatersrand) SARAO Bursary Conference November 28, / 22