Transcript Primordial black holes

Primordial black holes
B. Czerny
Copernicus Astronomical Center, Warsaw
on behalf of collaboration: D. Cline, B. Czerny,
A. Dobrzycki, A. Janiuk, C. Matthey, M.
Nikołajuk, S. Otwinowski
Introduction
The existence of the primary black holes is an unproved but a very interesting
possibility. Their detection, or their absence, will impose important constraints on
the physics of the early Universe, nature of the dark mass constituting the
dominant part of the matter, the origin of the high energy radiation and cosmic
rays, and finally on the quantum gravity.
Primary black holes were supposed to form during the early stage of the Big
Bang. In standard 4-dimensional approach their formation epoch t_0, their
expected lifetime, t_1, and the temperature of their Hawking emission are given
by the following expressions:
t0
M 0  10
[g]
 23
10
15
M 3
t1  ( 15 ) t now
10 g
T  10
7
M
[K ]
Msun
The existence of higher dimensions modify this predictions. Therefore, in our
search for primordial black holes we have to allow for a broad range of their
properties.
Scenarios of PBH formation
Several possibilities are discussed in the literature (see eg. Carr 2005):
• inhomogeneities formed during the inflation epoch
• epoch of soft equation of state
• collapse of cosmic loops
• bubble collisions
• collapse of domain walls
All these mechanisms give different expectations as for the range of masses
produced. For example, soft state phase and bubbles of broken symmetry creates
black holes with a narrow mass range, domain walls lead to brod range of masses
with fractal structure while inhomogeneities give broad power law distributions.
Where can we see now PBH?
Several plausible hypothesis were brought in so far:
• PBH constiture the dark mass, i.e. are seen through its gravitational effect
• some PBH evaporate now and
*
are seen as some type gamma of ray emission
*
produce cosmic rays
On the other hand, PBH are by no means the only explanation of these
phenomena so carefull analysis is needed in order to establish whether PBH can
contribute, or must contribute, to these phenomena. Several results were already
obtained with respect to this issue.
Present observational
constraints on PBH
1. Mmin = 1 g from the CMB quadrupole moment limit to the reheat temperature
2. Dark mass PBH in the mass range 1017-1020 g are excluded by lack of
femtolensing in gamma-ray bursts
3. Dark mass PBH in the mass range 1026-1034 g are excluded by lack of
microlensing in LMC stars (Alcock et al. 2001)
4. Present evaporation rate of 1015 g PBH consistent with COMPTEL and EGRET
data is 2.5 x 10-14 η pc-3 yr-1 (Green et al. 2001). The local overdensity factor
consistent with PBH constituting dark halo is η=2x105.
We plan to estimate the density of the more massive black holes at the basis of their Xray and gamma-ray radiation due to accretion of the interstellar/intergalactic material.
Preliminary formula for a total luminosity of the dark halo:
Laccr
r
n
M DH
M
 10
[erg / s]
5
3
12
10 (T / 100K ) 10 M sun M sun
41
Are any of GRB caused by PBH?
We have found that a significant
fraction of the Very Short Gamma Ray
Bursts (T90 < 0.1 s) show very
peculiar properties:
• they concentrate strongly in 1/8 of
the sky in the BATSE data
• they are much harder, with emission
extending beyond 5 MeV
• they probably do not have strong Xray afterglow, unlike (some) SWIFT
VSB events
Enhanced number of VSB in BATSE data are
Many such events are seen in KONUS comming from the anticenter region, unlike
data but without localization.
SWIFT/HETE2 events with afterglows (Cline et
al. in preparation).
Cline et al. 1999, 2005
Are any of GRB caused by PBH?
V/Vmax test shows that this class of
bursts is not located at cosmological
distances. Spectral properties are
consistent with expectation of the
evaporation of PBH. If so, the bursts
are located at a distance of about 100
pc, for a 4-d black hole mass.
Emission must be slightly beamed to
satisfy the occurance frquency of
Green et al. (2001). Anisotropy is an
interesting aspect, consistent with the
results of the Millenium cosmological
simulations of the dark matter
perturbations which predict
significant clumpiness of dark matter.
Tests based on dark matter
structure
There are plans to perform detailed studies of the dark matter distribution in
galaxies using the SALT ground telescope facility.
The target classes of objects:
• dwarf galaxies (Łokas et al.)
• Low Surface Brightness Galaxies (Czerny et al.)