arXiv:1809 - cmb-s4.orgCMB-S4 Lensing + LSST Galaxies: ! Towards Neutrino Mass without Optical Depth...
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CMB-S4 Lensing + LSST Galaxies: Towards Neutrino Mass without Optical Depth (et al.) Blake D. Sherwin (DAMTP / KICC, Cambridge) for Byeonghee Yu , Z Knight, Simone Ferraro, Lloyd Knox, Marcel Schmittfull arXiv:1809.02120 τ
Transcript of arXiv:1809 - cmb-s4.orgCMB-S4 Lensing + LSST Galaxies: ! Towards Neutrino Mass without Optical Depth...
CMB-S4 Lensing + LSST Galaxies: !Towards Neutrino Mass without Optical Depth (et al.) !
!
Blake D. Sherwin (DAMTP / KICC, Cambridge) for!Byeonghee Yu, Z Knight, Simone Ferraro, Lloyd Knox, Marcel Schmittfull!
arXiv:1809.02120!
τ!
Blake D. Sherwin (DAMTP / KICC, Cambridge) for!Byeonghee Yu, Z Knight, Simone Ferraro, Lloyd Knox, Marcel Schmittfull!
τ!
CMB-S4 Lensing + LSST Galaxies: !Towards Neutrino Mass without Optical Depth (et al.) !
! arXiv:1809.02120!
Motivation: measuring neutrino mass!
3!
• Neutrinos have mass – associated physics not well understood!
• we don’t know:!– absolute scale!– mass ordering!– their own
antiparticle?!– what gives neutrinos
mass? +…!• Cosmology:
measurement of mass sum >60meV will give insights!
!!!!
Xm⌫
Reminder: neutrino mass in cosmology!
4!
!• Massive neutrinos suppress small structure growth by !
#( scale factor, )!!!
[Palanque-Delabrouille 2015]!
a�3f⌫/5
z~1100!
f⌫ ⌘ ⌦⌫/⌦m /X
m⌫a
matter !power!
How to constrain neutrino mass!
5!
!Three ways of obtaining neutrino mass from structure growth: !1) compare low-z amplitude vs. z~1100 amplitude (requires tau); !!!
LSS structure probes!
Inferred from CMB, which probes Ase-2τ! 1)!
= τ = optical depth to CMB!
6!
!Three ways of obtaining neutrino mass from structure growth: !1) compare low-z amplitude vs. z~1100 amplitude (requires tau); !!!
LSS structure probes!
Inferred from CMB, which probes Ase-2τ! 1)!
current tau (optical depth) error limited – can’t improve constraints beyond 25meV!# # # # # # # # # # # # # # #(S4 lensing) !
How to constrain neutrino mass!
7!
!Three ways of obtaining neutrino mass from structure growth: !1) compare low-z amplitude vs. z~1100 amplitude (requires tau); !2) compare low-z amplitude vs. z~3-5 amplitude (without tau)!!!
LSS structure probes!
2)!
1)!
Inferred from CMB, which probes Ase-2τ!
How to constrain neutrino mass!
8!
!Three ways of obtaining neutrino mass from structure growth: !1) compare low-z amplitude vs. z~1100 amplitude (requires tau); !2) compare low-z amplitude vs. z~3-5 amplitude (without tau)!3) P(k) shape: compare high- vs low-k amplitude (without tau)!!!
LSS structure probes!
2)!
1)!3)!
Inferred from CMB, which probes Ase-2τ!
How to constrain neutrino mass!
• Lensing x galaxies + galaxy power !• S4+LSST: Schmittfull/Seljak ‘17 forecast tight constraints on σ8(z)#
# #!
!
!• Constrain neutrino mass without tau via σ8(z~3-5) vs. σ8(z~0-1)?!!!
Motivation 2): Mv from Low-z Growth?!
9!
σ8(z) measured within few x 10-3!!
“Magic” of sample variance cancellation for bias (ask me!)!
Cg` ⇠ b�2
8 Cgg` ⇠ b2�2
8 ! �8
0 1 2 3 4 5 6 7
z
10�3
10�2
10�1
1
101
102
dn/d
z[a
rcm
in�
2 ]
0
0.2
0.4
0.6
0.8
1.0
W
W
LSST Optimistic
LSST Gold
LSST galaxies
• Assume 1uK-arcmin temp noise, 1’ beam, ~40% sky CMB-S4 lensing (+ primary CMB)
DESI BAO • Expected uncertainties on the distances from 18 bins in the
range 0.15 < z < 1.85
Forecasting: CMB lensing + galaxies!Cg
` , C` , Cgg
`
+ linear bias!
0 1 2 3 4 5 6 7
z
10�3
10�2
10�1
1
101
102
dn/d
z[a
rcm
in�
2 ]
0
0.2
0.4
0.6
0.8
1.0
W
W
LSST Optimistic
LSST GoldLSST galaxies
• Assume 1uK-arcmin temp noise, 1’ beam, ~40% sky CMB-S4 lensing (+ primary CMB)
DESI BAO • Expected uncertainties on the distances from 18 bins in the
range 0.15 < z < 1.85
Forecasting: CMB lensing + galaxies!Cg
` , C` , Cgg
`
!!
Major caveat: not yet fully analysed systematic errors - redshift uncertainty and scale dependent bias potential
issues. Proof of concept for now!!!!
!!!!!!!!!
• Competitive constraints without optical depth information appear possible!
0.2 1 2 3 4 5 6 7zmax
20
30
40
50
�(P m
⌫)
[meV
]
Planck/S4(l > 30) + DESI+ S4Lens (C
l )
+ LSST Gold (Cgl + Cgg
l )
+ LSST Optimistic (Cgl + Cgg
l )
Forecast: neutrino mass! constraints without tau information!
no tau - S4Lens + DESI constraints!
gold!
optimistic!
no tau – LSST gal. + S4Lens + DESI constraints!>2 sigma !
>3 sigma !
min.!mass >!
!!!!!!!!!
• Competitive constraints without optical depth information appear possible; go beyond usual constraints when tau info also included.!
0.2 1 2 3 4 5 6 7zmax
20
30
40
50
�(P m
⌫)
[meV
]
Planck/S4(l > 30) + DESI+ S4Lens (C
l )
+ LSST (Cgl + Cgg
l )
Forecast: neutrino mass! constraints without tau information!
no tau – LSST gal. + S4Lens + DESI constraints!
add tau prior!
no tau - S4Lens + DESI constraints!
S4Lens + DESI constraints – with tau!>2 sigma !
>3 sigma !
min.!mass >!
• Scale dependence quite weak (hope for systematics?)!
Constraints without optical depth!
0 1 2 3 4 5 6 7z
0.98
0.99
1.0
1.01
�8(
z)/�
8(z)
, fidu
cial
a�3f⌫/5
Marginalize over ⇤CDM parameters and Bi; S4 + DESI added
Fixing ⇤CDM parameters
Origin of constraints? !Can’t all be from growth…!
not enough S/N to distinguish at ~2-3 sigma!
0.2 1 2 3 4 5 6 7zmax
25
30
35
40
45
50
�(P m
⌫)
[meV
]S4Lens + Planck/S4 Primary + DESI
Planck/S4 Primary + DESI + LSST Cggl (no “shape e↵ect”)
S4Lens + Planck/S4 Primary + DESI + LSST (no “shape e↵ect”)
Planck/S4 Primary + DESI + LSST Cggl
S4Lens + Planck/S4 Primary + DESI + LSST
CMB lensing removed
“shape effect” removed
Both “shape effect” and CMB lensing removed
!!!!!!!!!
• Both growth and shape responsible for majority of constraining power and contribute similarly (shape a bit more)!
Origin of constraints without optical depth!
0.2 2 4 6 8 10zmax
16
20
24
28
32�(P m
⌫)
[meV
]
CMB-S4 Nl + N shotLSST Gold:
LSST Optimistic: CMB-S4 Nl + N shot
CMB-S4 Nl + Zero N shot
Zero Nl + N shot
Zero Nl + Zero N shot
Zero Nl + Zero N shot (N = 21)
Further Improvements?!!!!!!!!!!
!!
• Improvements beyond tau limit possible with these methods, but extremely challenging. (Perhaps galaxy lensing can help?)!
lower lensing + shot noise!
go to even higher z!
Conclusions!
!!!!!!!• ~25meV neutrino mass constraint without
tau information appears possible w. LSST galaxies + CMB-S4; even better with tau.!
!• Caveat: systematics potentially challenging
and need to be investigated in more detail!!• Origin of constraints: from P(k) shape as
well as growth!0 1 2 3 4 5 6 7
z
0.98
0.99
1.0
1.01
�8(
z)/�
8(z)
, fidu
cial
a�3f⌫/5
Marginalize over ⇤CDM parameters and Bi; S4 + DESI added
Fixing ⇤CDM parameters
Also in progress: similar analysis of dark energy constraints led by Z Knight, L. Knox:!!
DE FoM increased by adding CMB lensing!!
Backup Slides - I!!!!!!!!!
!!
• Improvements important for current tau (less if tau improved)!
Backup Slides - II!!!!!!!!!
