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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.

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Primordial black holes

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  1. 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

  2. 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: 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.

  3. 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.

  4. 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.

  5. Present observational constraints on PBH • Mmin = 1 g from the CMB quadrupole moment limit to the reheat temperature • Dark mass PBH in the mass range 1017-1020 g are excluded by lack of femtolensing in gamma-ray bursts • Dark mass PBH in the mass range 1026-1034 g are excluded by lack of microlensing in LMC stars (Alcock et al. 2001) • 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 X-ray and gamma-ray radiation due to accretion of the interstellar/intergalactic material. Preliminary formula for a total luminosity of the dark halo:

  6. 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 X-ray afterglow, unlike (some) SWIFT VSB events • Many such events are seen in KONUS data but without localization. Enhanced number of VSB in BATSE data are comming from the anticenter region, unlike SWIFT/HETE2 events with afterglows (Cline et al. in preparation). Cline et al. 1999, 2005

  7. 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.

  8. 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.)

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