black holes in the universe

T.N. Ukwatta et al "Fermi Sensitivity to PBH Bursts" MG12 Paris July 12 - 18 2009

SENSITIVITY OF THE FERMI DETECTORS TO GAMMA-RAY BURSTS FROM EVAPORATING

PRIMORDIAL BLACK HOLES (PBHs) T. N. Ukwatta, Jane H. MacGibbon, W. C. Parke,

K. S. Dhuga, A. Eskandarian, N. Gehrels, L. Maximon, D. C. Morris and Stephen Rhodes

JANE H MACGIBBONUNIVERSITY OF NORTH FLORIDA


BLACK HOLES IN THE UNIVERSE

GALACTIC CENTERS: Supermassive BHs M ~ 1038 – 1043 g rs ~ 10 -3 - 103 AU

INTERMEDIATE MASS BLACK HOLES?: M ~ 1037 g rs ~ 103 km

STELLAR COLLAPSE: M ~ 1034 – 1035 g rs ~ 10 - 102 km

PRIMORDIAL BLACK HOLES?: M ~ 10 -5 – 1043 g rs ~ 10 -33 cm - 103 AU


PRIMORDIAL BLACK HOLESFORMATION MECHANISMS

Collapse of Overdense Regions

- Primordial Density Inhomogeneities- Inflation, Soft Equation of State, Cosmological

Phase Transitions

Colliding Bubbles of Broken Symmetry

Oscillating Cosmic Strings

Collapse of Domain Walls


PBH FORMATION

BH mass up to ~ cosmic horizon mass at formation

If form from Scale-Invariant Density Perturbations

1523( ) 10 g

10 sHtM t

2* *2 /i PBH crit

i

dn M M MdM

1, radiation era 2

PBH LIMITSConstraints on β = fraction of regions of

mass M which collapse

Graph: Carr (2005)

1PBH R z

PBH LIMITSConstraints on ε = fractional overdensity of

formation regions

Graph: Carr (2005)

2

2( ) ~ ( ) exp2 ( )

M MM


BLACK HOLE THERMODYNAMICS

HAWKING TEMPERATURE:

Solar Mass BH TBH ~ 10 -7 K MBH ~ 10 25 g TBH ~ 3 K CMB

HAWKING RADIATION FLUX:

3

131.06 GeV8 10

BHBH

BH

MckTGM g

12

2

,

exp 1 2 / 2

sS snl

n l

d N E n edt dE c

HAWKING RADIATION

Sources: Page, Elster, Simkins


TOTAL BLACK HOLE EMISSION

MASS LOSS RATE:

BLACK HOLE LIFETIME: Mass of PBH whose lifetime equals age of Universe

(MacGibbon, Carr & Page 2008):

gm 1004.000.5 14M

s x1024.6 1327- iievap MfM

225 15 x 10 / g g sBHBH BH

dM M f Mdt


STANDARD PICTURE

BH should directly evaporate those particles which appear non-composite compared to wavelength of the radiated energy (or equivalently BH size) at given TBH

As TBH increases: BH directly emits photons + gravitons + neutrinoes +

electrons + muons + pions

Once TBH >>ΛQCD: BH directly emits quarks and gluons (not direct pions) which

shower and hadronize into astrophysically stable γ , ν, p, pbar, e-, e+

BH EMISSION SPECTRA

Source: MacGibbon and Webber (1990)


BH EMISSION SPECTRA

Photosphere/Chromosphere Models (due to interactions between emitted particles)

eg Heckler, Cline and Hong, Kapusta and Daghigh, Belyanin et al, Bugaev et al

MacGibbon, Carr and Page 2008: None of the photosphere/chromosphere models work

because they neglect the requirement that the emitted particles must be in causal contact to interact and neglect LPM effects in any multiple scatterings; Also no quark-gluon plasma when TBH ~ ΛQCD

BH EMISSION SPECTRA


Astrophysical Spectra from Uniformly Distributed PBHs with dn/dMi α Mi

-2.5

Source: MacGibbon and Carr (1991)


ASTROPHYSICAL SPECTRA

GAMMA RAY EXTRAGALACTIC BACKGROUND (Carr & MacGibbon 1998):

IF PBHS CLUSTER IN GALACTIC HALO: Local density enhancement Galactic Halo Gamma Ray Background (Wright 1996) Antiprotons, Positrons Antimatter interactions, Microlensing

9 25.1 1.3 x10PBH h

125

local 1.010x5

hh

ANTIPROTONS

Barrau et al (2002)


ASTROPHYSICAL SPECTRA

CAN BURSTS FROM INDIVIDUAL BLACK HOLES AT THE END OF THEIR LIFE BE DETECTED?

Greater detection probability if number density of

PBHs is locally enhanced

WHAT WOULD PBH BURST SIGNAL LOOK LIKE?


PBH Bursts

PBHs Expiring Today:

(independent of formation spectrum)

Number Expiring:

Remaining lifetime for given TBH:

-1-3local

7 yr pc 10 N

2*, BH BH

BH

dn M M MdM


PBH as Seen by Ideal DetectorPhoton Flux from BH:

Photon flux per unit area reaching Earth fromBH at distance d:

If detector of effective area Aeff requires Xphotons over time t to register burst, need i.e. BH must be closer thanBH effF A t X

1/20.8 1/22

2

2.6 10 pcTeV m 1 min

effBHAT td

X

1.629 11.4 10 s

TeVBH BH

dN Tdt

2

/4

BHBH

dN dtF

d


PBH as Seen by Ideal DetectorWhat TBH maximizes chance of detection?

Take maximum t to be remaining BH lifetimeτevap. Then BH will be detected by ideal detector

if it is closer than distance d:

Detectability is maximized for lowest TBH BH visible above background and/or by using longest detector exposure time

1/20.7

2

0.03 pcTeV m

effBHATd

X


PBH as Seen by Ideal DetectorFor detector of angular resolution Ω to resolveBH above background Fγ :

Take EGRET background:

Then BH will be resolved above background byideal detector if it is closer than distance d:

BH eff effF A F A

2.46 2 1 1 11.0 x 10 cm GeV s sr

1 GeVdF EdE

0.81/2 0.7

0.04 pcsr 1 GeV TeV

BHTEd


Comparison of DetectorsTo detect, BH must be closer than:

Scanned volume where ωA is detector

acceptance angle (field of view). To resolve above background,

BH must be closer than:

Number that may be Expiring Today:

Air Shower Detectors: large Aeff but small ωA , large Ω,

background-limited

Fermi: smaller Aeff ~ 0.8 m2 but large ωA , small Ω ~ 1°, good time resolution, lower energy threshold, background-free

3

sr 3A

BHdV

-1-3local

7 yr pc 10 N

0.81/2 0.7

0.04 pcsr 1 GeV TeV

BHTEd

1/20.7

2

0.03 pcTeV m

effBHATd

X


FERMI Gamma-Ray Space Telescope

• launched June 2008

• detectors: Gamma-ray Burst

Monitor (GBM)

Large Area Telescope (LAT)

http://en.wikipedia.org/wiki/File:Delta_II_Heavy_just_before_liftoff_with_GLAST.jpg

PBH Bursts


Fermi LAT Energy Range: 20 MeV – 300 GeV


Detecting BH Bursts with LATSpectral Lag Method:

• Compare light curve in two energy bands

• Does not need many counts because not reconstructing full spectrum

• BH burst will show positive to negative evolution with increasing energy (TBH increases with time as

BH loses mass and )0.5

13 10 GeVGeV

BHTE

black holes in the universe

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