andrew hopkins- the cosmic star formation history and the diffuse supernova neutrino background

8/3/2019 Andrew Hopkins- The Cosmic Star Formation History and the Diffuse Supernova Neutrino Background

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The Cosmic Star Formation History and the

Diffuse Supernova Neutrino Background

Andrew HopkinsThe University of Sydney

With special thanks to John Beacom for significantcontributions, help, suggestions and advice.


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Cosmological parameters are now known to high accuracy.

Physical measurements of galaxy properties can be made with much

greater reliability than ever before.Galaxy evolution is now truly aquantitative subject. Understanding the underlying physical processes isnow within our reach.


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http://www.astro.princeton.edu/~frei/Gcat_htm/poster.jpg

In the nearby universe, galaxies look like this:


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But at very high redshift, galaxies look like this :


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and this:

Why?

One reason is

that the rate atwhich galaxiesform their starsevolves.


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Star formation in galaxies can be measured using many tracers:

Ultraviolet ( UV ) radiation, photons emitted directly by massive, young, short-lived stars

Balmer recombination line emission ( H in particular)

Dust emission (observed at far-infrared, FIR, wavelengths)

this is emission produced by dust grains which absorb UV andre-emit in the FIR.Synchrotron emission (observed at radio wavelengths) thought to be connected to star formation processes throughsupernova ejecta shock-accelerating cosmic ray electronpopulations to relativistic speeds in the ambient galacticmagnetic field.Others: Lyman, Paschen series in H, forbidden [OII]transition, X-rays, sub-mm dust emission, and more.


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FIRRadio

H

M51 Whirlpool Galaxy UV Visible NIR


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Star Formation Rate Density

Perform an observational survey, at a star-formationsensitive wavelength.Calculate the Luminosity Function (the number of galaxies as a function of luminosity, per unit volume).Scale luminosity to SFR using appropriate calibration,correcting as necessary for obscuration effects,incompleteness, instrumental or other systematics, etc.(A lot of recent work in particular has emphasisedreliable dust corrections, but the correction factors for

other effects can be of similar order.)Integrate over the Luminosity (SFR) Function todetermine total space density of SFR.Repeat for as many redshift slices as possible.


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Comoving space density of SFR

Redshift

S F R

d e n s

i t y


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Brief summary of the DSNBMid-1980s: Several researchers qualitatively explore neutrino emissionfrom supernovae and the DSNB (e.g., Krauss, Glashow & Schramm,Nature 1984, 310, 191)

1995: Totani & Sato (Astropart. Phys. 3, 376) calculate the neutrinospectrum for a supernova, and estimate the flux of electron antineutrinosfrom all supernovae, the relic supernova neutrino flux.

1997-2003: Various estimates for the level of the DSNB (e.g., Malaney

1997, Kaplinghat et al 2000, Ando et al 2003, Fukugita & Kawasaki 2003)2003: Malek et al (Phys. Rev. Lett. 90, 061101) measure an upper limiton the DSNB e flux with SK, of 1.2 cm -2 s -1.

2004: Beacom & Vagins (Phys. Rev. Lett. 93 171101) suggest loading SK with GdCl 3 to improve DSNB detection (and coin the new term).

2003-2006: Many and various combinations of cosmic SFH and DSNBlimit to infer average e temperature and other parameters.

2005: Lunardini (astro-ph/0509233) uses SN1987A to estimate DSNB.

2006: Hopkins & Beacom (astro-ph/0601463; ApJ in press) use SK DSNBlimit to constrain the normalisation of the cosmic star formation history.

_

_


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With distances well known, we can startthinking about comparing apparent and

absolute neutrino luminosities:ObjectSun

SN1987A

DSNB

ApparentMeasured

Measured

Upper limit

AbsoluteKnown (stellartheory)Known (SNtheory)Known (SN theory plus SN1987A)

Number1

1

Many (measured)


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All core-collapse supernovae (types II, Ib, Ic)have similar properties regarding neutrinoproduction

Neutrinos emitted with Fermi-Dirac energy spectrum

Total energy of 3 1053 erg = 3 1046 J

Total energy mostly shared among neutrinoflavours (after mixing in the SN)

Assumptions about e emission from SNe_


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Totani & Sato 1995

Neutrino Energy (MeV)

E m

i t t e d N e u

t r i n

o N

u m

b e r

Neutrino spectrum per supernova


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Totani & Sato 1995

Predicted DSNB energy spectrum

Neutrino Energy (MeV)

N u m b e r f l u x ( c m

- 2 s - 1 M e V

- 1)


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Comoving space density of SFR

S F R

d e n s

i t y

Redshift


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The Initial Mass Function

Baldry & Glazebrook 2003 ApJ 593, 258

SalB IMF

BG IMF


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Normalisation of the SFH

SalA IMF BG IMF

T=4 MeV or 6 MeV T=8 MeV

Characteristic e temperature:_


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Predicted e spectrum given the SFH_

E>19.3 MeV


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Constraints on the SFH: Summary

The SK neutrino limits place an upper limit on the(z


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Comments for further thoughtThe SK measurements are limited to energies above about 19

MeV, corresponding to the SFH up to redshifts of z~1. Novelmethods for sampling the DSNB spectrum down to ~5 MeV could constrain the SN rate at redshifts z>1 (Malaney 1997).

The slope of the DSNB spectrum is sensitive to the neutrino

temperature. Detecting and resolving the spectrum provides adirect probe of the characteristic SN neutrino temperature(Totani & Sato 1995).

Loading SK with GdCl 3 can improve its sensitivity to the DSNB

significantly (Beacom & Vagins 2004).Combining the background analysis from SK with thesensitivity to e of SNO can improve the measurement limit to6 cm -2 s-1 over 22.5


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andrew hopkins- the cosmic star formation history and the diffuse supernova neutrino background

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