arXiv subjects

Noraiz Tahir

Publications and source records attributed to Noraiz Tahir.

15 recordsLinked to original sources

arXiv2026

Evolution of Virial Clouds - II: From the Formation of First Stars up to their Explosion

The existence of cold gas and dust clouds close to the cosmic microwave background (CMB) temperature was proposed as a potential repository for a significant fraction of the missing baryons in galactic halos. While the evolution of the virial clouds from the last scattering surface (LSS) ($z=1100$) up to the formation of Population III (Pop III) stars ($z=48$) was studied in [N. Tahir, A. Qadir, M. Sakhi, \& F. De Paolis, The Euro. Phys. Jour. C 81, 827 (2021)] (Paper I), the subsequent evolution during the epoch of the first stars remained unexplored. In the present work, we investigate the second evolutionary phase of the virial clouds, covering the redshift range $48 \gtrsim z \gtrsim 10$. We develop a comprehensive model incorporating the coupled thermal, chemical, and dynamical evolution of the cloud, including CMB heating, adiabatic compression due to gravitational contraction, H$_2$ and metal-line cooling, and feedback from Pop III supernovae. Solving the coupled ordinary differential equations (ODE) numerically, we find that the cloud cools monotonically from $137$~K to $41.5$~K, contracts from $120$~pc to $89.8$~pc, and becomes enriched in metals and molecular hydrogen, while the cooling rate dominates the heating rate throughout the evolution.

astro-ph.GA↗

arXiv2026

Dark Matter Imprints on Black Hole Shadows and Chaotic Dynamics: A Comparative Study of Halo Profiles around Sgr A and M87

The gravitational influence of dark matter (DM) halos on the strong-field regime around supermassive black holes (SMBHs) remains largely unexplored. In the present work, we try to make a framework of the halo-modified space times for four well-known DM profiles including the Navarro Frenk-White (NFW), Moore, Burkert, and Dehnen-(1,4,3/4) profiles, respectively. We derive the corresponding photon spheres, shadow radii, and innermost stable circular orbits (ISCO) for the Sgr A* and M87*. We then constrain the DM halo parameters by comparing the theoretical values with the observed Event Horizon Telescope (EHT) data, and the robustness was checked by comparing the obtained virial mass of the Milky Way and M87 from the parameters with the values already present in the literature. In addition to this we extend the geodesic analysis by formulating the perturbed orbital dynamics using a Painlevé-Gullstrand Hamiltonian framework, and as a result we compute orbital trajectories, Poincaré sections, and finite-time Lyapunov ex ponents. These chaotic dynamics leave distinct imprints on gravitational waveforms, including phase irregularities and amplitude modulations.

physics.gen-ph↗

arXiv2026

Optical Signatures of Sgr A* and M87* with Dark Matter Halos

The event horizon telescope (EHT) has opened a new window onto the strong-field regime by imaging the shadows of the supermassive black holes (SMBHs) Sgr A* and M87*. These observations provide a unique laboratory for probing the dark matter (DM) distribution around black holes. In this work we systematically investigate the imprints of two distinct DM halo models, the cold DM (CDM), and the cored scalar field DM (SFDM) profiles on the gravitational lensing signatures of Sgr A* and M87*. We compute the photon spheres, shadows, weak and strong lensing observables, and caustic structures for both models. We then compared the obtained values of the shadow diameters with the EHT data, using $χ^2$ statistics. We found that all the models are within $1.2σ$ of the measured shadow diameters with the small $χ^2$ differences, $Δχ^2 \lesssim 1.2$. The caustic analysis reveals distinct topological regimes, Sgr A* retains both tangential and radial critical curves, while M87* may show only tangential critical curves due to its larger mass. This topological difference provides a clear observational signature for future observations.

astro-ph.CO↗

arXiv2026

Dark Matter and Dark Energy in Three-Higgs Doublet Model

This article discusses the incorporation of dark matter and dark energy into a new physics model called the Three-Higgs Doublet Model. Dark matter and dark energy are accommodated as CP-even and $Z_2$-odd scalars in their respective inert doublets. By leveraging a $Z_2$ symmetry to suppress certain interactions, we model the behavior of dark matter. Similarly, by imposing a shift symmetry, dark energy can be mimicked within the same framework for the current cosmic epoch. The dark matter relic density is calculated for our model using \texttt{micrOMEGAs}. It is shown that despite the inclusion of dark energy, dark matter relic density can be brought within observational bounds and match existing literature. Furthermore, the one-loop and two-loop Renormalization Group Equations (RGEs) were computed using \texttt{SARAH} to ensure radiative stability over a large range of energies. This study lays the groundwork for a future study of dark matter-dark energy interactions in the early universe and the exploration of different early universe dynamics.

hep-ph↗

arXiv2026

Black hole shadow parameters and quasi-normal modes for Weyl-incorporated gravity

An additional term of the form $λ\mathbf{T} \cdot \mathbf{C} \cdot \mathbf{T}$ in the Einstein-Hilbert Lagrangian was introduced to explain the interaction between matter and pure gravitational field [H. W. Lee and A. Qadir, Motion of test particle for Weyl-interaction gravity, {\it Int. Jour. Mod. Phys. D} {\bf 28}(16) (2019) 2040014], the modified relativistic dynamics (MORD). In this paper, we estimate the shadow parameters of black hole in a spherically symmetric static spacetime within the MORD framework. As a first approximation, we assume that the black hole is surrounded by a constant-density baryonic matter halo. The analysis is then extended by introducing a homogeneous plasma background. We compute the shadow radii for various black hole masses and analyze their dependence on the WIG coupling parameter $λ$. In addition, we compute the fundamental quasi-normal mode (QNM) frequencies under test-field approximation, and perform a time-domain integration analysis.

gr-qc↗

arXiv2026

The Galactic Halo Rotation by Weyl Incorporated Gravity

A modification of the Einstein-Hilbert Lagrangian by introducing a coupling between the Weyl tensor and the stress-energy tensor was proposed to explain flat galactic rotation curves without the exotic (non-baryonic) dark matter (DM) [1]. The proposed coupling constant was previously determined by fitting the rotational velocities of the Milky Way and M31 modeled with constant density, yielding the same coupling constant for both [2,3]. In this work, we have modified the formalism for a variable density by modeling the galactic systems with realistic, spherically symmetric and radially varying density profiles for the baryonic matter and this analysis is applied to seven edge-on spiral galaxies of the local cluster [4-10] and the Milky Way.

astro-ph.GA↗

arXiv2025

Accounting for the absence of anomalous microwave emission in the M 31 halo

The discovery of a temperature asymmetry in the cosmic microwave background (CMB) data towards various galaxies has opened a window for a deeper comprehension of galactic halos. A crucial step forward is that of estimating the fraction of missing baryons in the halos, but it relies on understanding the real cause of the observed CMB temperature asymmetry since many effects might give a non-negligible contribution. Here, we analyzed the contribution played by the anomalous microwave emission (AME) from halo dust grains in the halo of the M 31 galaxy. Assuming either amorphous carbon and silicates dust grains with size ranging from $0.01~μ$m to about $0.3~μ$m and mass in the range $10^{-14} - 10^{-13}$ g, we estimated the total mass, distribution, and diffuse emission in the $100\,μ$m band of the Infrared Astronomical Satellite (IRAS). Then, we estimated the temperature asymmetry induced by the rotation of the M 31 halo and compared the obtained values with the \textit{Planck}'s SMICA-processed data. We find that the AME cannot account for the measured CMB temperature asymmetry, with its contribution constrained to $\lesssim 7\%$, thereby indicating that additional physical mechanisms must be responsible for the observed signal.

astro-ph.GA↗

arXiv2024

The Baryonic Mass Estimates of the Milky Way Halo in the form of High Velocity Clouds

The halo of our Galaxy is populated with a significant number of high-velocity clouds (HVCs) moving with a speed up to $500$ km/s. It is suggested that these HVCs might contain a non-negligible fraction of the missing baryons. The main aim of the current paper is to estimate the baryonic mass of the Milky Way halo in the form of HVCs in order to constrain a fraction of missing baryons in the form of these clouds. Such findings would give substantial help in the studying halo dynamics of our Galaxy. We first estimate the HVCs distance. We consider the most recent and updated HVC catalog, namely the Galactic All Sky Survey (GASS), which, however, covers the southern sky declinations, south of $b \leq 60^\circ$. Following a model presented in the literature, we assume that most of the HVCs (not all of the HVCs in the Milky Way) were ejected from the Magellanic Clouds (MCls) which is at a distance of about 50 kpc. We assume that the HVCs have a temperature in the range of about $10^2 - 10^4$ K, and are distributed in the Galactic halo as the Navarro-Frenk-White (NFW) profile. Since the GASS survey covers a small portion of the sky, we estimate the number of missing clouds by using Monte Carlo (MC) simulations. The next step will be to estimate the total mass of the Milky Way contained in the form of these HVCs. The total mass resulted to be $\sim (7 \pm 2) \times 10^{9} M_{\odot}$ in the form of HVCs and compact high-velocity clouds (CHVCs).

astro-ph.GA↗

arXiv2023

On the Galactic Halos Rotation by Planck Data

As galactic halos are not directly visible, there are many ambiguities regarding their composition and rotational velocity. Though most of the dark matter is non-baryonic, {\it some fraction is}, and it can be used to trace the halo rotation. Asymmetries in the CMB towards M31 had been seen in the Planck data and ascribed to the rotational Doppler shift of the M31 halo. Subsequently, the same methods were used in the direction of five other galaxies belonging to the Local Group, namely M33, M81, M82, NGC 5128, and NGC 4594. It had been proved that there could be stable clouds of gas and dust in thermal equilibrium with the CMB at 2.7 K, which had been called ``virial clouds''. In this paper, adopting this scenerio, an attempt is made to constrain the fraction of dust grains and gas molecules in the clouds.

astro-ph.GA↗

arXiv2022

Virial clouds to explain rotational asymmetry in galactic halos

The rotation of the galactic objects has been seen by asymmetric Doppler shift in the CMB data. Molecular hydrogen clouds at virial temperature may contribute to the galactic halo dark matter and they might be the reason for the observed rotational asymmetry in the galactic halos. We present a method to constrain the parameters of these virial clouds given that they are composed of a single fluid. The method is such that it should be possible to extend it to more than one fluid.

astro-ph.GA↗

arXiv2022

The rotational kinetic Sunyaev-Zeldovich contribution to the temperature asymmetry toward the M31 halo

Temperature asymmetry in the cosmic microwave background (CMB) data by the Planck satellite has been discovered and analyzed toward several nearby edge-on spiral galaxies. It provides a way to probe galactic halo rotation, and to constrain the baryon fraction in the galactic halos. The frequency independence of the observed data provides a strong indication of the Doppler shift nature of the effect, due to the galactic halo rotation. It was proposed that this effect may arise from the emission of cold gas clouds populating the galactic halos. However, in order to confirm this view, other effects that might give rise to a temperature asymmetry in the CMB data, have to be considered and studied in detail. The main aim of the present paper is to estimate the contribution in the CMB temperature asymmetry data due to the free-free emission by hot gas (particularly electrons) through the rotational kinetic Sunyaev-Zeldovich (rkSZ) effect. We concentrate, in particular, on the M31 galactic halo and compare the estimated values of the rkSZ induced temperature asymmetry with those obtained by using the SMICA pipeline of the Planck data release, already employed to project out the SZ sources and for lensing studies. As an additional consistency check, we also verified that the hot gas diffuse emission in the X-ray band does not exceed that detected in the soft X-ray band by ROSAT observations. We note that our results clearly show that the rkSZ effect gives only a minor contribution to the observed M31 halo temperature asymmetry by Planck data.

astro-ph.GA↗

arXiv2021

Seeing the halo rotation of nearby spiral galaxies using Planck data

The rotation of the galactic halos is a fascinating topic which is still waiting to be addressed. Planck data has shown the existence of a temperature asymmetry towards the halo of several nearby galaxies, such as M31, NGC 5128, M33, M81, and M82. However, the cause of this asymmetry is an open problem. A possibility to explain the observed effect relies on the presence of "cold gas clouds" populating the galactic halos, which may be the answer to the so-called missing baryon problem. Here, we present a technique to estimate an upper limit to the rotational velocity of the halo of some nearby spiral galaxies by using both their dynamical masses and the Planck data.

astro-ph.GA↗

arXiv2021

Virial clouds explaining the observed rotational asymmetry in the galactic halos

Rotation of galactic objects has been seen in the cosmic microwave background (CMB) that could be ascribed to molecular hydrogen clouds with, or without, dust contamination and contamination from other sources. We model the clouds using the canonical ensemble for pure molecular hydrogen, a mixture of hydrogen helium and/or dust, in order to constrain the physical parameters of these clouds. Since the clouds are cold, we justify the use of the canonical ensemble by explicitly calculating the interaction between the hydrogen molecules and the CMB photons and determining the time required for thermal equilibrium to be reached and show that there is enough time for equilibrium to be attained.

astro-ph.GA↗

arXiv2021

Virial clouds evolution from the last scattering upto the formation of first stars

The asymmetry in the cosmic microwave background (CMB) towards several nearby galaxies detected by Planck data is probably due to the rotation of "cold gas" clouds present in the galactic halos. In 1995 it had been proposed that galactic halos are populated by pure molecular hydrogen clouds which are in equillibrium with the CMB. More recently, it was shown that the equillibrium could be stable. Nevertheless, the cloud chemical composition is still a matter to be studied. To investigate this issue we need to trace the evolution of these virial cloud from the time of their formation to the present, and to confront the model with the observational data. The present paper is a short summary of a paper [1]. Here we only concentrate on the evolution of these clouds from the last scattering surface (LSS) up to the formation of first generation of stars (population-III stars).

astro-ph.GA↗

arXiv2021

Evolution of virial clouds-I: from surface of last scattering up to the formation of population-III stars

The analysis of WMAP and Planck CMB data has shown the presence of temperature asymmetries towards the halos of several galaxies, which is probably due to the rotation of clouds present in these halos about the rotational axis of the galaxies. It had been proposed that these are hydrogen clouds that {\it should} be in equilibrium with the CMB. However, standard theory did not allow equilibrium of such clouds at the very low CMB temperature, but it was recently shown that the equilibrium {\it could} be stable. This still does not prove that the cloud concentration and that the observed temperature asymmetry is due to clouds in equilibrium with the CMB. To investigate the matter further, it would be necessary to trace the evolution of such clouds, which we call "virial clouds", from their formation epoch to the present, so as to confront the model with the observational data. The task is to be done in two steps: (1) from the cloud formation before the formation of first generation of stars; (2) from that time to the present. In this paper we deal with the first step leaving the second one to a subsequent analysis.

astro-ph.GA↗