UNDERSTANDING THE PHYSICS OF GALAXY CLUSTERS OUT TO THEIR VIRIAL RADII AND BEYOND

In the hierarchical structure formation model, galaxy clusters grow and evolve via mergers and accretion from the surrounding cosmic web, leaving distinctive marks in the gas properties, metallicity, and dynamical state at the outskirts of clusters, which needs to be probed to better understand the growth of a cluster. I probed the gas properties of four nearby galaxy groups MKW4, Antlia, RXJ1159, and ESO3060170 out to their virial radii using deep Suzaku and mostly snapshot Chandra observations. I found the gas entropy profiles of MKW4 follow a power-law at its outskirts - as expected from purely gravitational structure formation model. I measured an enclosed baryon fraction of 11% at the outskirts of MKW4, remarkably smaller than the cosmic baryon fraction of 15%, suggesting galaxy groups due to their shallow gravitation potential are vulnerable to baryon loss. I measured the average Fe abundance of four groups at their outskirts, which is remarkably uniform and strikingly similar to that of massive clusters and fully consistent with the numerical predictions from the IllustrisTNG cosmological simulation. This result support an early-enrichment scenario among galactic systems over an order of magnitude in mass even before their formation. I also studied the gas dynamics of a early-stage merging galaxy cluster, Abell 98, using deep Chandra observations. I reported the first unambiguous detection of an axial merger shock, which unveils a critical epoch in the formation of a massive galaxy cluster when two subclusters are caught in the early phase of the merging process. I also detected X-ray emission from the the warm-hot intergalactic medium (WHIM) filament, lies between two subclusters of Abell 98

Tolosa-Hunt syndrome: a rare case report with uncommon imaging findings and discussion

A 45 year old diabetic but non hypertensive female presented with unilateral ptosis and complete external ophthalmoplegia on the left side. All the routine investigations were inconclusive. A signal void change was found in MRI study including angiogram of brain. On performing VEP (visually evoked potential), there was mild left optic pathway dysfunction (axonal and demyelinating). A probable diagnosis of Tolosa-Hunt Syndrome (THS) was made and the patient was started on steroids. She responded dramatically to the therapy and was discharged on steroids. Thus the diagnosis of THS was confirmed. On follow up after one month, both her ptosis and ophthalmoplegia had resolved completely. On subsequent follow up visits, she was free of any ophthalmological symptoms and signs

Perturbative correction terms to electromagnetic self-force due to metric perturbation : astrophysical and cosmological implications

We consider the equation of motion of a charged particle or a charged compact object in curved space-time, under the reaction of electromagnetic radiation and also consider a physical situation such that the charged particle or compact object emits gravitational radiation, thereby gravitational radiation reaction also acts on it. We investigate the effect of this metric perturbation i.e. the gravitational radiation on the electromagnetic self-force. We show that, besides the interaction terms derived by P. Zimmerman and E. Poisson, additional perturbative terms are generated, which are linear in metric perturbation and are generated due to perturbation of the electromagnetic self-force by the metric perturbation. We discuss the conditions of significance of these perturbative terms and also the interaction terms with respect to the gravitational self-force in various astrophysical and cosmological cases ; such as the motion of charged particles around black holes, some extreme mass-ratio inspirals (EMRIs) involving sufficiently accelerated motion of charged stars (specially neutron stars) or charged stellar mass black holes around supermassive black holes, and motion of charged particles around charged primordial black holes formed in the early Universe etc.. We find that in some astrophysical and cosmological cases these perturbative terms can have significant effect in comparison with the gravitational radiation-reaction term.Comment: 13 page

Non-HIV AIDS presenting with adrenal histoplasmosis and pulmonary tuberculosis: a mesmerising case report and discussion

Non-HIV AIDS or idiopathic CD4 lymphocytopenia (ICL) is an acquired immunodeficiency syndrome resulting in CD4 lymphopenia without any evidence of HIV infection or any other apparent cause of immunosuppression.  A non-diabetic patient presented with adrenal histoplasmosis and UTI leading to adrenal failure. No immediate cause of immunosuppression was found, HIV, HTLV screening were negative. A CD4 count was done and the patient was found to be having non-HIV AIDS (idiopathic CD4 lymphocytopenia). He was treated and discharged. Few months later the patient presented again with adrenal failure & pulmonary tuberculosis. Adrenal FNAC showed persisting adrenal histoplasmosis. CD4 count found to be low again, but this time it was worse than the previous scenario