arXiv subjects

Oswaldo D. Miranda

Publications and source records attributed to Oswaldo D. Miranda.

At least 19 recordsLinked to original sources

arXiv2025

The cosmological lithium problem

The discrepancy between the predictions of primordial nucleosynthesis and the observed lithium abundance in Spite plateau stars has been attributed either to a challenge to the standard model of nucleosynthesis or to stellar processes occurring after the stars formed. To understand the origin of this discrepancy, it is crucial to link the cosmic star formation rate with a chemical enrichment model that incorporates the yields of both Population (Pop) III and II stars. It is within this framework that the evolution of lithium can be determined. The primary goal is to demonstrate that there is no discrepancy between the predictions of primordial nucleosynthesis and the observed lithium abundance. By combining a standard chemical evolution model with the hierarchical structure formation scenario, it is possible to determine the lithium abundance as a function of $[\mathrm{Fe/H}]$. The model's results are compared with observational data, including two extremely iron-poor stars: J0023+0307 and SMSS J0313-6708. The Spite plateau is naturally established in the range $-8.0 \lesssim [\mathrm{Fe/H}] \lesssim -2.0$ with $^{7}\mathrm{Li/H}$ $\sim 1.81 \times 10^{-10}$. We find that J0023+0307 could have formed $\sim 4.4 \times 10^{5} - 1.3 \times 10^{6}$ years after the explosion of the first Pop III star in the Universe, whereas for SMSS J0313-6708 this event would have occurred $\sim 2.2 \times 10^{5} - 4.4 \times 10^{5}$ years later. The Spite plateau serves as an observational signature of the formation of Pop III stars. The abundances observed in J0023+0307 and SMSS J0313-6708 are consistent with Pop III progenitor stars in the mass range $10-100 M_{\odot}$. However, if some high-redshift star formation occurs within subhalo-like structures, the contribution of stars in the mass range $140-260 M_{\odot}$ to the formation of the extended Spite plateau cannot be ruled out.

astro-ph.CO↗

arXiv2025

Optimal Detection Bands for Intermediate-Mass Black Hole Binaries: Prospects for LISA and AMIGO in General Relativity and $f(R, T)$ Gravity

We present a semi analytic forecast for the detection of intermediate mass black hole (IMBH) binaries with the space based detectors LISA (millihertz band) and AMIGO (deci hertz band). A redshift dependent population model is built from extrapolated black hole mass functions and realistic pairing and merger time scales. Folding this population through the instrument sensitivities yields event rates of about 1e4 mergers for LISA in four observing years and between 1e2 and 1e3 mergers for AMIGO in three years, with complementary optimal detection bands in total mass and redshift. We then incorporate the minimal matter coupled modified gravity model f(R,T) = R + 2 lambda T. In this scenario the strain amplitude is rescaled by (1 - lambda / 8 pi)^(5/6) while the waveform phasing is unchanged at leading order. For Solar System compatible couplings abs(lambda) <= 2 x 10^-3, the peak detection redshift shifts by less than one percent and the total number of events changes by less than five percent. Combined statistics from LISA and AMIGO therefore provide a consistency check on f(R,T) gravity without spoiling standard IMBH forecasts.

gr-qc↗

arXiv2022

Potential contributions of Pop III and intermediate-mass Pop II stars to cosmic chemical enrichment

We propose a semi-analytic model that is developed to understand the cosmological evolution of the mean metallicity in the Universe. In particular, we study the contributions of Population III (Pop III) and Population II (Pop II) stars to the production of $\mathrm{Fe,~Si,~Zn, ~Ni,~P, ~Mg, ~Al, ~S, ~C, ~N}$, and $\mathrm{~O}$. We aim to quantify the roles of two different models in the chemical enrichment of the Universe. The first model (A) considers both stars with Pop III and Pop II yields. For the second model (B), the yields involved are only for Pop II stars. We start by describing the cosmic star formation rate (CSFR) through an adaptation of a scenario developed within the hierarchical scenario of structure formation with a Press-Schechter-like formalism. We adapt the formalism to implement the CSFR to the standard chemical evolution scenario to investigate the course of chemical evolution on a cosmological basis. Calculations start at redshift $z\sim 20$, and we compare the results of our two models with data from damped Lyman-$α$ systems (DLAs), and globular clusters (GCs). Our main results find that metal production in the Universe occurred very early, quickly increasing with the formation of the first stars. When comparing results for [Fe/H] with observations from GCs, yields of Pop II stars are not enough to explain the observed chemical abundances, requiring stars with physical properties similar those expected from Pop III stars. Our semi-analytic model can deliver consistent results for the evolution of cosmic metallicities. Our results show that the chemical enrichment in the early Universe is rapid, and at redshift $\sim 12.5$, the metallicity reaches $10^{-4}\, Z_{\odot}$ for the model that includes Pop III stars. In addition, we explore values for the initial mass function (IMF) within the range $[0.85, 1.85]$.

astro-ph.CO↗

arXiv2021

Dark matter Annihilation in the Most Luminous and the Most Massive Ultracompact Dwarf Galaxies (UCD)

In this paper, we explore the potential astrophysical signatures of dark matter (DM) annihilations in ultra-compact dwarf galaxies (UCDs) considering two of the richest known galaxy clusters within 100 million light-years, nominally, Virgo and Fornax. Fornax UCD3 is the most luminous known UCD and M59 UCD3 is the most massive known UCD. With the detection of a 3.5 million solar mass black hole (BH) in Fornax UCD3, we carefully model several dark matter (DM) enhanced profile scenarios, considering the presence of both a supermassive black hole (SMBH) and DM. For Fornax UCD3, the comparison of the stellar and dynamical masses suggests that there is little content of DM in UCDs. M59 UCD3 did not receive the same attention in simulations as Fornax UCD3, however deep radio imaging and X-ray observations were performed for M59 UCD3 and can be used to place limits in DM content of these UCDs. We take an average estimate of dark matter content and used the Salpeter and Kroupa mass functions. We model Fornax UCD3 and M59 UCD3 to have a DM content that is the average of these mass functions. We then analyze the constraints for Fornax and M59 UCD3 coming from $γ$-ray and radio sources, considering a dark matter particle with a mass between 10 and 34 GeV in our simulations. In the absence of a strong $γ$-ray signature, we show that the synchrotron emission from electrons and positrons produced by DM annihilations can be very sensitive to indirect DM search. We find that DM parameters can be significantly constrained at radio frequencies and that the spike profiles play an interesting role in the deep study of the enhancements of DM & BH interactions in ultra-compact galaxies.

astro-ph.GA↗

arXiv2020

Magnetohydrodynamic waves excited by a coupling between gravitational waves and a strongly magnetized plasma in binaries of neutron stars

Coalescence of binary neutron stars (BNSs) is one of the sources of gravitational waves (GWs) able to be detected by ground-based interferometric detectors. The event GW170817 was the first observed in the gravitational and electromagnetic spectra, showing through this joint analysis a certain compatibility with the models of short gamma-ray bursts (sGRBs) to explain the signature of this system. Due to the intense magnetic fields of the neutron stars, the plasma magnetosphere stays strongly magnetized and the propagation of the GW through plasma can excite magnetohydrodynamic (MHD) modes such as Alfvén and magnetosonic waves. The MHD modes carry energy and momentum through the plasma, suggesting a mechanism to accelerate the matter during the coalescence of the binaries, explaining some characteristics of the fireball model of the sGRBs. We present a semianalytical formalism to determine the energy transferred by the GW-MHD interaction during the inspiral phase of the stars. Using the inferred physical parameters for GW170817, we show that the energy in the plasma can reach maximum value $\sim 10^{35}\,{\rm J}$ ($\sim 10^{32}\,{\rm J}$) for the Alfvén mode (magnetosonic mode) if the angle formed between the background magnetic field and the GW propagation direction is $θ= π/ 4$. Particularly, for $θ= π/ 2$ only the magnetosonic mode is in coherence with the GWs. In this case, the excited energy in the plasma reaches maximum value $\sim 10^{36} {\rm J}$. If the magnetic field on the surface of the progenitors of the event GW170817 was $\sim 2\times 10^{9}\,{\rm T}$ then energies comparable to those inferred for the GRB 170817A could be obtained. In particular, our semianalytical formalism show consistence with the results obtained by other authors through full general relativistic magnetohydrodynamics (GRMHD) simulations. [ABRIDGED]

astro-ph.HE↗

arXiv2020

What Could be the Observational Signature of Dark Matter in Globular Clusters?

Here we investigate the possibility that some globular clusters (GCs) harbor intermediate mass black holes (BH) in their centers and are also embedded in a low-mass dark matter (DM) halo. Up to date, there is no evidence on whether or not GCs have DM in their constitution. For standard cold DM cosmology, it is expected that GCs form with their own DM halos. Other studies investigate the possibility that GCs were initially embedded in massive DM halos that evolved during the cluster lifetime. An additional intriguing question is related to the existence of intermediate mass black holes (IMBH) in the of GCs. The determination of whether GCs hold IMBHs would be able to answer important questions about GCs formation and the circumstances that gave rise to the IMBHs. DM & IMBH in the context of GCs are interesting subjects to be studied and we will perform such studies here, assuming the coexistence of both of them in some GCs. Having such information, we perform the study possible DM signals from GCs. One important subject to be studied is the DM density profile. In the inner regions of GCs, the DM density profile is still an open question of fundamental importance to DM studies, specially for the study of radio and $γ$-ray emission from DM annihilation in such regions (abridged).

astro-ph.HE↗

arXiv2019

Some Implications of the Leptonic Annihilation of Dark Matter: Possible Galactic Radio Emission Signatures and the Excess Radio Flux of Extragalactic Origin

We give theoretical predictions for the radio emission of a dark matter candidate annihilating into 2-lepton and 4-lepton final states. We then compare our results with the known radio measurements of the sky temperature as a function of the frequency. In particular, we calculate the radio emission for some dark matter candidates annihilating into intermediate bosons that subsequently decay into a 4-lepton channel with a thermal annihilation cross-section. We show that within the range of frequencies from $20\,{\rm MHz}$ to $5\,{\rm GHz}$, this channel can produce a stronger signature than direct annihilation into leptons.

hep-ph↗

arXiv2019

Mimetic gravity: mimicking the dynamics of the primeval universe in the context of loop quantum cosmology

Mimetic gravity can be described as a formulation capable of mimicking different evolutionary scenarios regarding the universe dynamics. Notwithstanding its initial aim of producing a similar evolution to the one expected from the dark components of the standard cosmology, a recent association with loop quantum cosmology could also provide interesting results. In this work, we reinterpret the physics behind the curvature potential of mimetic gravity description of loop quantum cosmology. Furthermore, we also test the compatibility of our formulation for a Higgs-type field, proving that the mimetic curvature potential can mimic the dynamics from a Higgs inflationary model. Additionally, we discuss possible scenarios that emerge from the relationship between matter and mimetic curvature and, within certain limits, describe results for the primeval universe dynamics obtained by other authors.

gr-qc↗

arXiv2018

Simulating the Interaction of a Comet With the Solar Wind Using a Magnetohydrodynamic Model

We present simulations of a comet interacting with the solar wind. Such simulations are treated in the framework of the ideal, 2D magnetohydrodynamics (MHD), using the FLASH code in order to solve the equations of such a formalism. Besides, the comet is treated as a spherically symmetric source of ions in the equations of MHD. We generate results considering several scenarios, using different values for the physical parameters of the solar wind and of the comet in each case. Our aim is to study the influence of the solar wind on the characteristics of the comet and, given the nonlinear nature of the MHD, we search for the occurrence of phenomena which are typical of nonlinear systems such as instabilities and turbulence.

physics.space-ph↗

arXiv2017

Connecting the Cosmic Star Formation Rate with the Local Star Formation

We present a model that unifies the cosmic star formation rate (CSFR), obtained through the hierarchical structure formation scenario, with the (Galactic) local star formation rate (SFR). It is possible to use the SFR to generate a CSFR mapping through the density probability distribution functions (PDFs) commonly used to study the role of turbulence in the star-forming regions of the Galaxy. We obtain a consistent mapping from redshift $z\sim 20$ up to the present ($z = 0$). Our results show that the turbulence exhibits a dual character, providing high values for the star formation efficiency ($\langle\varepsilon\rangle \sim 0.32$) in the redshift interval $z\sim 3.5-20$ and reducing its value to $\langle\varepsilon\rangle = 0.021$ at $z = 0$. The value of the Mach number ($\mathcal{M}_{\rm crit}$), from which $\langle\varepsilon\rangle$ rapidly decreases, is dependent on both the polytropic index ($Γ$) and the minimum density contrast of the gas. We also derive Larson's first law associated with the velocity dispersion ($\langle V_{\rm rms}\rangle$) in the local star formation regions. Our model shows good agreement with Larson's law in the $\sim 10-50\,{\rm pc}$ range, providing typical temperatures $T_{0} \sim 10-80\,{\rm K}$ for the gas associated with star formation. As a consequence, dark matter halos of great mass could contain a number of halos of much smaller mass, and be able to form structures similar to globular clusters. Thus, Larson's law emerges as a result of the very formation of large-scale structures, which in turn would allow the formation of galactic systems, including our Galaxy.

astro-ph.GA↗

arXiv2013

Probing a cosmological model with a $Λ= Λ_0 + 3βH^2$ decaying-vacuum

In this work we study the evolution of matter-density perturbations for an arbitrary $Λ(t)$ model, and specialize our analysis to the particular phenomenological law $Λ= Λ_0 + 3βH^2$. We study the evolution of the cosmic star formation rate in this particular dark energy scenario and, by constraining the $β$ parameter using both the age of the universe and the cosmic star formation rate curve, we show that it leads to a reasonable physical model for $β\lesssim 0.1$.

gr-qc↗

arXiv2012

Stochastic background of relic gravitons in a bouncing quantum cosmological model

The spectrum and amplitude of the stochastic background of relic gravitons produced in a bouncing universe is calculated. The matter content of the model consists of dust and radiation fluids, and the bounce occurs due to quantum cosmological effects when the universe approaches the classical singularity in the contracting phase. The resulting amplitude is very small and it cannot be observed by any present and near future gravitational wave detector. Hence, as in the ekpyrotic model, any observation of these relic gravitons will rule out this type of quantum cosmological bouncing model.

gr-qc↗

arXiv2012

Stochastic backgrounds of gravitational waves from cosmological sources - The role of dark energy

[Abridged] We investigate the detectability of the gravitational stochastic background produced by cosmological sources in scenarios of structure formation. The model considers the coalescences of three kind of binary systems: double neutron stars, the neutron star-black hole binaries, and the black hole-black hole systems. We also included the core-collapse supernovae leaving black holes as compact remnants. We use two different dark-energy scenarios, cosmological constant and Chaplygin gas, in order to verify their influence on the cosmic star formation rate, the coalescence rates, and on the gravitational wave backgrounds. We calculate the gravitational wave signals separately for each kind of source as well as we determine their collective contribution for the stochastic background of gravitational waves. Concerning to the compact binary systems, we verify that these sources produce stochastic backgrounds with signal-to-noise ratios (S/N) ~ 1.5 (~ 0.90) for NS-NS, ~ 0.50 (~ 0.30) for NS-BH, ~ 0.20 (~ 0.10) for BH-BH for a pair of advanced LIGO detectors in the cosmological constant (Chaplygin gas) cosmology. Particularly, the sensitivity of the future third generation of detectors as the Einstein Telescope (ET) could increase the present signal-to-noise ratios by a high-factor (~ 300 - 1000) when compared to the (S/N) calculated for advanced LIGO detectors. Thus, the third generation of gravitational wave detectors could be used to reconstruct the history of star formation in the Universe as well as for contributing with the characterization of the dark energy, for example, identifying if there is evidence for the evolution of the dark energy equation-of-state parameter w(a).

astro-ph.CO↗

arXiv2012

OGCOSMO: An auxiliary tool for the study of the Universe within hierarchical scenario of structure formation

In this work is presented the software OGCOSMO. This program was written using high level design methodology (HLDM), that is based on the use of very high level (VHL) programing language as main, and the use of the intermediate level (IL) language only for the critical processing time. The languages used are PYTHON (VHL) and FORTRAN (IL). The core of OGCOSMO is a package called OGC{\_}lib. This package contains a group of modules for the study of cosmological and astrophysical processes, such as: comoving distance, relation between redshift and time, cosmic star formation rate, number density of dark matter haloes and mass function of supermassive black holes (SMBHs). The software is under development and some new features will be implemented for the research of stochastic background of gravitational waves (GWs) generated by: stellar collapse to form black holes, binary systems of SMBHs. Even more, we show that the use of HLDM with PYTHON and FORTRAN is a powerful tool for producing astrophysical softwares.

cs.CE↗

arXiv2012

Programing Using High Level Design With Python and FORTRAN: A Study Case in Astrophysics

In this work, we present a short review about the high level design methodology (HLDM), that is based on the use of very high level (VHL) programing language as main, and the use of the intermediate level (IL) language only for the critical processing time. The languages used are Python (VHL) and FORTRAN (IL). Moreover, this methodology, making use of the oriented object programing (OOP), permits to produce a readable, portable and reusable code. Also is presented the concept of computational framework, that naturally appears from the OOP paradigm. As an example, we present the framework called PYGRAWC (Python framework for Gravitational Waves from Cosmological origin). Even more, we show that the use of HLDM with Python and FORTRAN produces a powerful tool for solving astrophysical problems.

cs.CE↗

arXiv2011

Supermassive Black Holes: Connecting the Growth to the Cosmic Star Formation Rate

In this Letter, we present a model connecting the cosmic star formation rate (CSFR) to the growth of supermassive black holes. Considering that the evolution of the massive black hole is dominated by accretion (Soltan's argument) and that the accretion process can be described by a probabilistic function directly regulated by the CSFR, we obtain the evolution of the black hole mass density. Then using the quasar luminosity function, we determine both the functional form of the radiative efficiency and the evolution of the quasar duty-cycle as functions of the redshift. We analyze four different CSFRs showing that the quasar duty-cycle, $δ(z)$, peaks at $z\sim 8.5-11$ and so within the window associated with the reionization of the Universe. In particular, $δ_{\rm max}\sim 0.09-0.22$ depending on the CSFR. The mean radiative efficiency, $\barη(z)$, peaks at $z\sim 0.1-1.3$ with $\barη_{\rm max}\sim 0.10-0.46$ depending on the specific CSFR used. Our results also show that is not necessary a supercritical Eddington accret

astro-ph.CO↗

arXiv2010

Massive Black Hole Binary Systems in Hierarchical Scenario of Structure Formation

The hierarchical scenario of structure formation describes how objects like galaxies and galaxy clusters are formed by mergers of small objects. In this scenario, mergers of galaxies can lead to the formation of massive black hole (MBH) binary systems. On the other hand, the merger of two MBH could produce a gravitational wave signal detectable, in principle, by the Laser Interferometer Space Antenna (LISA). In the present work, we use the Press-Schechter formalism, and its extension, to describe the merger rate of haloes which contain massive black holes. Here, we do not study the gravitational wave emission of these systems. However, we present an initial study to determine the number of systems formed via mergers that could permit, in a future extension of this work, the calculation of the signature in gravitational waves of these systems.

astro-ph.CO↗

arXiv2010

Can Massive Gravitons be an Alternative to Dark Energy?

In this work, we explore some cosmological implications of the model proposed by M. Visser in 1998. In his approach, Visser intends to take in account mass for the graviton by means of an additional bimetric tensor in the Einstein's field equations. Our study has shown that a consistent cosmological model arises from Visser's approach. The most interesting feature is that an accelerated expansion phase naturally emerges from the cosmological model, and we do not need to postulate any kind of dark energy to explain the current observational data for distant type Ia supernovae (SNIa).

astro-ph.CO↗