Browsing by Author "Sureda, Joaquin"

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    Power spectrum of density fluctuations, halo abundances, and clustering with primordial black holes
    (2021) Padilla, Nelson D.; Magana, Juan; Sureda, Joaquin; Araya, Ignacio J.
    We study the effect of dark matter (DM) being encapsulated in primordial black holes (PBHs) on the power spectrum of density fluctuations P(k); we also look at its effect on the abundance of haloes and their clustering. We allow the growth of Poisson fluctuations since matter and radiation equality and study both monochromatic and extended PBH mass distributions. We present updated monochromatic black hole mass constraints by demanding < 10 per cent deviations from the Lambda cold dark matter (CDM) power spectrum at a scale of k = 1 hMpc(-1). Our results show that PBHs with masses > 10(4) h(-1) M-circle dot are excluded from conforming all of the DM in the Universe. We also apply this condition to our extended Press-Schechter (PS) mass functions, and find that the Poisson power is scale dependent even before applying evolution. We find that characteristic masses M* <= 10(2) h(-1) M-circle dot are allowed, leaving only two characteristic PBH mass windows of PS mass functions when combining with previous constraints, M* similar to 10(2) h(-1) M-circle dot and similar to 10(-8) h(-1) M-circle dot where all of the DM can be in PBHs. The resulting DM halo mass functions within these windows are similar to those resulting from CDM made of fundamental particles. However, as soon as the parameters produce unrealistic P(k), the resulting halo mass functions and their bias as a function of halo mass deviate strongly from the behaviour measured in the real Universe.
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    Press-Schechter primordial black hole mass functions and their observational constraints
    (2021) Sureda, Joaquin; Magana, Juan; Araya, Ignacio J.; Padilla, Nelson D.
    We present a modification of the Press-Schechter (PS) formalism to derive general mass functions for primordial black holes (PBHs), considering their formation as being associated with the amplitude of linear energy density fluctuations. To accommodate a wide range of physical relations between the linear and non-linear conditions for collapse, we introduce an additional parameter to the PS mechanism, and that the collapse occurs at either a given cosmic time, or as fluctuations enter the horizon. We study the case where fluctuations obey Gaussian statistics and follow a primordial power spectrum of broken power-law form with a blue spectral index for small scales. We use the observed abundance of supermassive black holes (SMBH) to constrain the extended mass functions taking into account dynamical friction. We further constrain the modified PS by developing a method for converting existing constraints on the PBH mass fraction, derived assuming monochromatic mass distributions for PBHs, into constraints applicable for extended PBH mass functions. We find that when considering well-established monochromatic constraints, there are regions in parameter space where all the dark matter can be made of PBHs. Of special interest is the region for the characteristic mass of the distribution similar to 10(2) M-circle dot, for a wide range of blue spectral indices in the scenario where PBHs form as they enter the horizon, where the linear threshold for collapse is of the order of the typical overdensities, as this is close to the black hole masses detected by LIGO, which are difficult to explain by stellar collapse.