arXiv subjects

G. Anand

Publications and source records attributed to G. Anand.

5 recordsLinked to original sources

arXiv2025

The MUSE view of the Sculptor galaxy: survey overview and the planetary nebulae luminosity function

NGC 253, the Sculptor galaxy, is the southern, massive, star-forming disk galaxy closest to the Milky Way. In this work, we present a new 103-pointing MUSE mosaic of this galaxy covering the majority of its star-forming disk up to 0.75xR25. With an area of ~20x5 arcmin2 (~20x5 kpc2, projected) and a physical resolution of ~15 pc, this mosaic constitutes one of the largest, highest physical resolution integral field spectroscopy surveys of any star-forming galaxy to date. Here, we exploit the mosaic to identify a sample of ~500 planetary nebulae (~20 times larger than in previous studies) to build the planetary nebula luminosity function (PNLF) and obtain a new estimate of the distance to NGC 253. The value obtained is 17% higher than estimates returned by other reliable measurements, mainly obtained via the top of the red giant branch method (TRGB). The PNLF also varies between the centre (r < 4 kpc) and the disk of the galaxy. The distance derived from the PNLF of the outer disk is comparable to that of the full sample, while the PNLF of the centre returns a distance ~0.9 Mpc larger. Our analysis suggests that extinction related to the dust-rich interstellar medium and edge-on view of the galaxy (the average E(B-V) across the disk is ~0.35 mag) plays a major role in explaining both the larger distance recovered from the full PNLF and the difference between the PNLFs in the centre and in the disk.

astro-ph.GA↗

arXiv2023

GAASP: Genetic Algorithm Based Atomistic Sampling Protocol for High-Entropy Materials

High-Entropy Materials are composed of multiple elements on comparatively simpler lattices. Due to the multicomponent nature of such materials, the atomic scale sampling is computationally expensive due to the combinatorial complexity. We propose a genetic algorithm based methodology for sampling such complex chemically-disordered materials. Genetic Algorithm based Atomistic Sampling Protocol (GAASP) variants can generate low and well as high-energy structures. GAASP low-energy variant in conjugation with metropolis criteria avoids the premature convergence as well as ensures the detailed balance condition. GAASP can be employed to generate the low-energy structures for thermodynamic predictions as well as diverse structures can be generated for machine learning applications.

cond-mat.mtrl-sci↗

arXiv2022

Order Parameter Engineering for Random Systems

The chemical short-range order (CSRO) in the crystalline materials influences the properties and its effect is particularly important in the context of the multicomponent materials. We propose a scheme for CSRO parameter or $\mathrm{Δ-}$parameter in terms of number of like and unlike bonds in the multicomponent systems. The OPERA or $\bf{O}$rder $\bf{P}$arameter $\bf{E}$ngineering for $\bf{RA}$ndom Systems scheme for both semi-canonical as well as canonical ensemble is proposed. The proposed framework provides a high-throughput scheme for exploration of the CSRO in terms of the $\mathrm{Δ-}$parameter. We demonstrate the applicability of the $\mathrm{Δ-}$parameter for describing the CSRO in multicomponent alloys and oxides (FCC-CoCrNi, BCC-MoNbTaW and (CoCuMgNiZn)O). We show that the $\mathrm{Δ-}$parameter not only inherits the merit of Warren-Cowley order parameter, but it also addresses its limitations. The $\mathrm{Δ-}$parameter being a scalar quantity can represent the chemical order and OPERA framework can deal with both semi-canonical and canonical ensemble

cond-mat.mtrl-sci↗

arXiv2019

Electron spin mediated distortion in metallic systems

The deviation of positions of atoms from their ideal lattice sites in crystalline solid state systems causes distortion and can lead to variation in structural [1] and functional properties [2]. Distortion in molecular systems has been traditionally understood in the term of Jahn-Teller distortion [3], while for the one-dimensional chain of metals, the Peierls distortion mechanism has been proposed [4]. In a real three dimensional metallic systems, a fundamental description of the distortion is missing, which we need to design alloys with attractive structural properties. The present investigation presents the evolution of distortion in metallic systems in terms of magnetovolume effects arising due to magnetic ground-state of the system. Particularly the significant distortion in the case of Cr due to presence of other transition metals is seen. Cr alloyed with transition metals as a candidate system to study the correlation between charge disproportion, spin-flip, magnetovolume effects and Fermi surface nesting. This study provides a novel explanation of strengthening effect of Cr observed in alloys due to its unique magnetic properties.

cond-mat.mtrl-sci↗

arXiv2017

The High-Redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: The \spitzer Catalog

We present 190 galaxy cluster candidates (most at high redshift) based on galaxy overdensity measurements in the \spitzer/IRAC imaging of the fields surrounding 646 bent, double-lobed radio sources drawn from the Clusters Occupied by Bent Radio AGN (COBRA) Survey. The COBRA sources were chosen as objects in the VLA FIRST survey that lack optical counterparts in the Sloan Digital Sky Survey (SDSS) to a limit of $m_r=22$, making them likely to lie at high redshift. This is confirmed by our observations: the redshift distribution of COBRA sources with estimated redshifts peaks near $z=1$, and extends out to $z\approx3$. Cluster candidates were identified by comparing our target fields to a background field and searching for statistically significant ($\ge2σ$) excesses in the galaxy number counts surrounding the radio sources; 190 fields satisfy the $\ge2σ$ limit. We find that 530 fields (82.0\%) have a net positive excess of galaxies surrounding the radio source. Many of the fields with positive excesses but below the $2σ$ cutoff are likely to be galaxy groups. Forty-one COBRA sources are quasars with known spectroscopic redshifts, which may be tracers of some of the most distant clusters known.

astro-ph.GA↗