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Transcript of Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle...
![Page 1: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/1.jpg)
Selecting Supernovae for Cosmology
Cosmic Co-Motion, Courant Cove, September 2010
Troels Haugbø[email protected]
Niels Bohr International Academy – University of Copenhagen
Collaborators: Bjarne Thomsen, Steen Hannestad
![Page 2: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/2.jpg)
Main Points
With upcoming survey telescopes we will discover so many local
supernovae that complete spectroscopic follow up of is unfeasible.
To sample the peculiar velocity field, a regularly spaced
distribution is advantageous, to avoid power leaking.
Obtaining spectra for only a carefully selected subset gives the
best constraints from the least observational investment.
![Page 3: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/3.jpg)
Peculiar Velocity Fields
Velocity trace mass:
v = - H f(m)
where is the density contrast, and f(m) the growth factor
The peculiar velocity field is sourced by the gravitational
potential: It is directly dependent on the dark matter distribution
![Page 4: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/4.jpg)
Connecting the matter and velocity powerspectrum
● Velocity trace mass: v = - H f(m)
● The angular velocity powerspectrum is related to the matter powerspectrum :
![Page 5: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/5.jpg)
Peculiar Velocity Fields● Further away than ~80 Mpc h-1 cosmic variance is small
enough, that we can constrain cosmological models
● Gravity sources the velocity field from density fluctuations on larger scales
● This is why peculiar velocities may be the best measure of 8 at z=0
The velocity field 90 Mpc h-1 away
-1100 1100 km/s
The density field 90 Mpc h-1 away
![Page 6: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/6.jpg)
Upcoming surveys● Lensing/asteroid surveys are better for local supernovae,
than the high-z SNe surveys. They scan the sky continuously, and observe in many bands (typically 6).
● LSST saturates at m < 16-17 or d < 75-120 Mpc h-1
Pan-Starrs
(4x)1.4Gp
2009+
Hawaii
Sky Mapper
256Mp
2010
Australia
LSST3.2Gp
2014
Chile
Pan-Starrs
![Page 7: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/7.jpg)
Goals
● Predict how well we can probe the local velocity field, with upcoming supernovae surveys
● Design the optimal observational strategy to maximize science output
● Use the angular power spectrum of the peculiar velocity field as a tool for constraining cosmology
![Page 8: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/8.jpg)
Goals
● Predict how well we can probe the local velocity field, with upcoming supernovae surveys
● Design the optimal observational strategy to maximize science output
● Use the angular power spectrum of the peculiar velocity field as a tool for constraining cosmology
![Page 9: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/9.jpg)
Goals
● Predict how well we can probe the local velocity field, with upcoming supernovae surveys
● Design the optimal observational strategy to maximize science output
● Use the angular power spectrum of the peculiar velocity field as a tool for constraining cosmology
![Page 10: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/10.jpg)
Forecast● The local supernova rate is approximately
1.2 x 10-4 SN yr-1 h3 Mpc-3
● This gives 60000 potential Type Ia SN per year with distances less than 500 h-1 Mpc (z < 0.17)
● There will be light curves from survey telescopes, but precise redshifts are needed
![Page 11: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/11.jpg)
Forecast● The local supernova rate is approximately
1.2 x 10-4 SN yr-1 h3 Mpc-3
● This gives 60000 potential Type Ia SN per year with distances less than 500 h-1 Mpc (z < 0.17)
● There will be light curves from survey telescopes, but precise redshifts are needed
● A dedicated 1 m telescope would be able to take ~7000 spectra per year, or roughly 25% of the Type Ia SNe, assuming the survey telescopes covers half the sky
![Page 12: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/12.jpg)
Goals
● Predict how well we can probe the local velocity field, with upcoming supernovae surveys
● Design the optimal observational strategy to maximize science output
● Use the angular power spectrum of the peculiar velocity field as a tool for constraining cosmology
![Page 13: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/13.jpg)
Observational Strategy
●The precision we can measure the angular powerspectrum with depends crucially on the geometric distribution on the sphere
●Essentially power can “leak out” if there are big holes on the sky.
●We know where the SNe are before finding the redshift from the surveys
![Page 14: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/14.jpg)
Reconstructing the velocity PS- a geometric detour -
3072 Random Points3072 Glass Points3072 “HealPix” Points12288 Random Points
![Page 15: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/15.jpg)
(figures thanks to Anja Weyant)
Signal
Power Leaking
![Page 16: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/16.jpg)
How to make a supernova survey
Make Nbody sim
Find density and velocity on a spherical shell
Populate with Supernovae
Calculate Angular PS
Size of voids/Max of matter PS
Size of clusters
![Page 17: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/17.jpg)
...but there is more to it
● With a limited amount of SNe, we can only measure a limited part of the powerspectrum
● Algorithm:● Given a set of Supernovae. Calculate powerspectrum
![Page 18: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/18.jpg)
...but there is more to it
● With a limited amount of SNe, we can only measure a limited part of the powerspectrum
● Algorithm:● Given a set of Supernovae. Calculate powerspectrum● Make N mock catalogues with same errors
![Page 19: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/19.jpg)
...but there is more to it
● With a limited amount of SNe, we can only measure a limited part of the powerspectrum
● Algorithm:● Given a set of Supernovae. Calculate powerspectrum● Make N mock catalogues with same errors● Compare the mock powerspectra to the underlying
powerspectrum● This gives theshot noise + window function
![Page 20: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/20.jpg)
...but there is more to it
● With a limited amount of SNe, we can only measure a limited part of the powerspectrum
● Algorithm:● Given a set of Supernovae. Calculate powerspectrum● Make N mock catalogues with same errors● Compare the mock powerspectra to the underlying
powerspectrum● This gives theshot noise +window function
● Subtract the error term from the observed powerspectrum
![Page 21: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/21.jpg)
● There are light curves, but we need precise redshifts● A 1 m telescope can take 1 spectra in ~20 minutes
~7000 spectra per year
● It is not realistic to measure 60000 redshifts per year
● We need to optimize our observation strategy and only select “the right” supernovae
Supernovae on a glass
![Page 22: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/22.jpg)
Goals
● Predict how well we can probe the local velocity field, with upcoming supernovae surveys
● Design the optimal observational strategy to maximize science output
● Use the angular power spectrum of the peculiar velocity field as a tool for constraining cosmology
![Page 23: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/23.jpg)
Connecting the matter and velocity powerspectrum
Small scale amplitude 8
![Page 24: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/24.jpg)
Small scale amplitude or 8
● Amplitude on large scales is fixed by the CMB●8 can be affected by
●Massive neutrinoes less power
256
Mp
c h
-1
Standard CDM 3 x 2.3 eV neutrinoes
![Page 25: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/25.jpg)
Small scale amplitude or 8
● Amplitude on large scales is fixed by the CMB●8 can be affected by
●Massive neutrinoes less power●Features / tilts in the primordial power spectrum
![Page 26: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/26.jpg)
Consequences for cosmology● The overall amplitude depends on
H f(m)8
This combination break
degeneracies,and8 can be constrained: Using 6 redshift bins (3 yrs of data, 23.000 glass Sne), and a simple 2 analysis (with fixed H), we find
a determination of 8 with 95% confidence
![Page 27: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/27.jpg)
● The overall amplitude depends on
H f(m)8
This combination break
degeneracies,and8 can be constrained: Using 6 redshift bins (3 yrs of data, 23.000 glass Sne), and a simple 2 analysis, we find
a determination of 8 with 95% confidence
Consequences for cosmologyGlass SupernovaeAll Supernovae
![Page 28: Selecting Supernovae for Cosmology Cosmic Co-Motion, Courant Cove, September 2010 Troels Haugbølle haugboel@nbi.dk Niels Bohr International Academy – University.](https://reader035.fdocuments.net/reader035/viewer/2022062511/551ad3e05503466b6a8b5586/html5/thumbnails/28.jpg)
● Peculiar velocities or bulk flows can be measured using low redshift supernovae
● The peculiar velocity field is important to understand:● It tells out about the structure of the local Universe● It has to be corrected for in the Hubble diagram● We can directly probe the gravitational potential, do
Cosmology, and learn about the bias
● Upcoming survey telescopes will observe thousands of low redshift supernovae - but this potential can only be realized if time at support telescopes is allocated
● Optimizing the window function optimizes the science output
● We forecast that with 3 years of LSST data we can constrain 8 to roughly 5%
Summary