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Jyoti Yadav

Publications and source records attributed to Jyoti Yadav.

At least 19 recordsLinked to original sources
arXiv2026

Spatial Correlations of PAH, UV, H$\alpha$ Emission and IMF - PAH Variations in the Star-Forming Complexes of NGC 628

We examine the spatial correlation of emission from polycyclic aromatic hydrocarbons (PAH) (3.3 $\mu$m, 7.7 $\mu$m, and 11.3 $\mu$m) with the far-ultraviolet (FUV), near-ultraviolet (NUV), and H$\alpha$ emission from star-forming complexes (SFCs) in different regions of NGC 628. We use the James Webb Space Telescope to detect PAH emission, along with the Ultraviolet Imaging Telescope and Multi Unit Spectroscopic Explorer observations to sample the UV and H$\alpha$ emission, respectively. We investigate the correlation of PAH luminosities with FUV, NUV, and H$\alpha$ luminosities for the extracted SFCs. We find that the arm and spur SFCs show bright PAH emission, except for those with only NUV emission, located primarily in bubbles and superbubbles. We also examine these correlations in the phantom void, the largest superbubble in NGC 628. We investigate the trend for FUV-NUV and the Initial mass function (IMF) index $\alpha_2$ derived from the ratio of B stars with PAH band ratios (F335M/F1130W, F770W/F1130W, and F335M/F770W). We find that PAH band ratios increase as the IMF becomes more top-heavy and the SFCs become bluer, consistent with enhanced PAH excitation and ionisation in stronger UV radiation fields. However, $\alpha_2$ of spur SFCs shows a flat trend with PAH band ratios compared to arms. Upon closer examination, two SFCs in the shell region of the phantom void showed a flatter IMF compared to the SFC located near the elongated bubble. This is likely due to gas accumulation, possibly through feedback mechanisms in the shell region, while the SFC near the elongated bubble may have formed in a region affected by shear.

astro-ph.GA↗
arXiv2026

Star Formation Beyond the Optical Disk : The Low-Density Outskirts of NGC2090

We present a far-ultraviolet (FUV) analysis of the star-forming complexes (SFCs) in the nearby spiral galaxy NGC\,2090, based on observations from the Ultraviolet Imaging Telescope (UVIT), and compare it with emission from the optical and infrared bands. NGC\,2090 exhibits prominent star formation in its extended outer disk, with FUV emission traced out to $\sim$30 kpc, far beyond the truncation of the old stellar disk at $\sim$5 kpc. It is classified as an extended UV (XUV) disk galaxy. We identify and characterize the SFCs both within and beyond the optical radius (R$_{25}$), estimating their physical sizes and star formation rates (SFRs). The outer-disk SFCs are generally smaller in area and show a narrower distribution of SFR surface density ($Σ_{\mathrm{SFR}}$) compared to the inner-disk SFCs. We investigate the properties of the inner disk using mid-infrared data from the James Webb Space Telescope (JWST), and find that the polycyclic aromatic hydrocarbon (PAH) emission is strongly correlated with regions of active star formation. The specific SFR (sSFR) increases with radius, consistent with a scenario of inside-out disk growth. The observed number of SFCs and their H$α$-to-FUV flux ratios in the outer disk of NGC\,2090 indicate ongoing massive star formation and are consistent with a top-heavy IMF, implying that the upper end of the IMF is not truncated in the low-density, metal-poor outskirts. These results suggest that XUV disks can host significant massive star formation despite their low stellar density and metallicity.

astro-ph.GA↗
arXiv2026

Search for Faint Lone Double-Peaked H$α$ Lines as IMBH Signatures in the MUSE Deep Field

Double-peaked H$α$ emission profiles can serve as potential signatures of accreting intermediate-mass black holes (IMBHs), particularly those residing outside galactic nuclei. Such features are expected to arise from rotating disk-like structures around black holes and can be used to identify elusive IMBH candidates. \citet{Almeida2022ApJ...934..100S} reported a sample of such double-peaked H$α$ sources in the MUSE-Wide survey, interpreting them as potential signatures of wandering IMBHs after systematically excluding alternative explanations. Their method relied on constructing H$α$ maps around central galaxies and visually identifying compact emission clumps in the surrounding halo regions. In this work, we revisit the analysis using the deeper MUSE Extremely Deep Field (MXDF) data and an automated detection algorithm tailored to identify such features. However, we do not recover any candidate population in MXDF, resulting in a null detection. This outcome is nevertheless informative, as it (1) highlights the inherent challenges in detecting IMBHs, and (2) demonstrates the potential of automated approaches for future systematic searches, even though it did not yield a positive outcome in this case.

astro-ph.GA↗
arXiv2026

Environment and Gas Fraction in Type-2 AGN versus Non-AGN Galaxies

We investigate the environmental parameters and gas fraction (f$_{gas}$) properties of type~2 AGN and non-AGN galaxies, utilizing a large sample of galaxies from SDSS DR7 with z $\le$ 0.3. We find that the environment affects type~2 AGN and non-AGN galaxies in similar ways and does not impact the strength of AGN-driven outflows. The f$_{gas}$ of type~2 AGN and non-AGN host galaxies show no variation between group and isolated environments, suggesting that host galaxy gas content is largely independent of large-scale environment. We find that type~2 AGN host galaxies possess systematically lower f$_{gas}$ than their non-AGN counterparts when matched in stellar mass and star formation rate (SFR). This suggests that AGN activity plays a significant role in regulating the molecular gas reservoir and, consequently, the star formation processes within galaxies. We find that Type~2 AGNs exhibiting strong outflows are associated with higher gas fractions, higher star-formation rates, and younger stellar populations than those with weak or no outflows. This may indicate either concurrent star formation in gas-rich systems hosting powerful outflows, or a time delay between AGN activity and its effect on star formation consistent with a delayed AGN feedback scenario.

astro-ph.GA↗
arXiv2025

Spin Hall effect in the high-resistivity high-entropy alloy AlCrMoW

We study thin films of the high-entropy alloy system Al$_{x}$(CrMoW)$_{1-x}$, grown on Ta seed layers by magnetron co-sputtering. Between $x=0.2$ and $x=0.6$, a resistivity larger than 100$μΩ$cm is achieved, with a peak of 180$μΩ$cm at $x=0.5$. Around the stoichiometric composition AlCrMoW, the alloy forms a bcc solid solution. The harmonic Hall method was used to characterize the spin Hall angle of the alloy series, where a maximum spin Hall angle of $θ= -0.12 \pm 0.01$ is observed for $x=0.25$. The implied spin Hall conductivity is $σ_\mathrm{SH} \approx -72\,000 \, \hbar/(2e)$\,S/m. The experimental results show excellent agreement with density functional theory calculations, which show similar trends and values. The results demonstrate that high-entropy alloys with a main-group element component can form a simple crystal structure and show high resistivity. This suggests that a whole new class of materials for spin Hall device engineering is available with simple methods.

cond-mat.mtrl-sci↗
arXiv2025

On the geometry of Riemannian warped product maps

In this paper, we begin by introducing Clairaut Riemannian warped product maps and establish the condition under which a regular curve becomes a geodesic. We obtain the conditions for a Riemannian warped product map to be Clairaut Riemannian warped product map followed by Ricci curvature. Further, we study the Ricci soliton structure on a Riemannian warped product manifold using curvature tensor. We examine the Bochner type formulae for Clairaut Riemannian warped product map and construct a supporting example. Furthermore, we extend the study to introduce and examine some geometric aspects of conformal Riemannian warped product maps. We derive the integral formula for scalar curvature of conformal Riemannian warped product map. Finally, we construct an example for conformal Riemannian warped product map.

math.DG↗
arXiv2025

Enhanced THz emission from spintronic emitters with Pt-Al alloys

Platinum (Pt) is the element with the largest spin Hall conductivity and is known as the most efficient spin-to-charge conversion material in spintronic THz emitters. By alloying with aluminum (Al), its resistivity can be substantially increased, exceeding $100\,μΩ$cm. While the spin Hall conductivity is reduced by alloying, the relative resistivity increase surpasses the reduction of spin Hall conductivity and thereby enhances the spin Hall angle. We make use of this mechanism to improve the commonly used Pt-based spintronic THz emitter and demonstrate that an increase of 67% in the THz emission amplitude can be achieved between 20\% and 30\% Al in Pt. We show that the enhanced THz emission amplitude is driven by the enhanced multilayer impedance due to the larger resistivity.

cond-mat.mtrl-sci↗
arXiv2025

Emergent spin Hall conductivity in Tantalum-Rhenium alloys

We investigate the spin Hall conductivity (SHC) of a composition series of a Ta-Re bcc solid solution. At approximately 60 at.% Ta the Ta-Re alloy features an SHC similar to bcc-W, while both endpoints of the compositional series have rather moderate SHC. The intermediate stoichiometries exhibit a substantial enhancement due to Fermi level tuning through the same band structure feature which gives bcc-W and $β$-W its large SHC. We provide experimental evidence for the enhancement of the SHC in the alloy via THz emission upon ultrafast laser excitation of Ta-Re/CoFeB bilayers. We demonstrate that a rigid band model derived from bcc-W and Fermi level tuning describes the experimental data with a similar accuracy as coherent potential approximation alloy calculations of the SHC.

cond-mat.mtrl-sci↗
arXiv2025

Unveiling the kinematics of a central region in the triple AGN host NGC 7733-7734 interacting group

We present a detailed study of the interacting triple active galactic nuclear system NGC 7733-34, focusing on stellar kinematics, ionised gas characteristics and star formation within the central region and stellar bars of both galaxies. We performed a comprehensive analysis using archival data from MUSE, HST/ACS, and DECaLS, complemented by observations from UVIT and IRSF. We identified a disc-like bulge in both NGC 7733 and NGC 7734 through 2-D decomposition. A central nuclear structure, with a semi-major axis of $\sim$1.113 kpc, was detected in NGC 7733 via photometric and kinematic analysis, confirmed by the strong anti-correlation between $V/σ$ and $h_{3}$, indicative of circular orbits in the centre. NGC 7734 lacks a distinct nuclear structure. The presence of disc-like bulge results in an anti-correlation between $V/σ$ and $h_{3}$ along with diffuse light. However, it does show higher central velocity dispersion, possibly attributed to an interaction with a smaller clump, which is likely a fourth galaxy within the system. Both galaxies demonstrate ongoing star formation, evidenced by $FUV$ and $Hα$ observations. NGC 7734 shows recent star formation along its bar, while NGC 7733 experiences bar quenching. The star formation rate (SFR) analysis of NGC 7734 reveals that the bar region's SFR dominates the galaxy's overall SFR. Conversely, in NGC 7733, the lack of star formation along the bar and the presence of a Seyfert 2 active galactic nuclei at the galaxy centre leave the possibility of a connection between both facts. However, it does not affect the galaxy's overall star formation. Our findings provide valuable insights into the stellar and gas kinematics, star formation processes, and active galactic nuclear feedback mechanisms in interacting galaxies hosting stellar bars.

astro-ph.GA↗
arXiv2024

Clairaut anti-invariant Riemannian maps with Kähler and Ricci soliton structures

The aim of this article is to explore the Clairaut anti-invariant Riemannian maps from/to Kähler manifolds admitting Ricci solitons. We find the curvature relations and calculate the Ricci tensor under different conditions. We discuss the condition under which range space becomes $α$-Ricci soliton. We obtain conditions for the range and kernel spaces of these maps to be Einstein. Next, we find the scalar curvature for range space. Further, we give the relation between Ricci curvature and Lie derivative under these maps. Moreover, we find the condition for a vertical potential vector field on target manifold to be conformal vector field on range space of these maps. Finally, we give non-trivial examples of such maps.

math.DG↗
arXiv2024

The morphology and kinematics of the galaxy group AM 1054-325: A MUSE perspective

Galaxy interactions in groups can lead to intense starbursts and the activation of active galactic nuclei (AGNs). The stripped gas from the outer disk can lead to star-forming clumps along the tidal tails or sometimes tidal dwarf galaxies. We investigate the impact of interaction on various galaxy properties, including morphology, star formation rates, and chemical composition in the galaxy group AM\,1054-325 using Multi Unit Spectroscopic Explorer (MUSE) data. We conduct a comprehensive spatially and spectrally resolved investigation of the star formation rate, star formation histories, metallicity, and AGN activity. The galaxy subgroup AM\,1054-325A shows multiple star-forming clumps in H$α$ emission along the western tidal tail, which are formed due to tidal stripping. These clumps also have higher metallicities. AM\,1054-325B is quenched and shows disturbed gas kinematics and the signature of gas accretion in the H$α$ map. The specific star formation along the tidal tail is higher, contributing to the galaxy's overall stellar mass growth.

astro-ph.GA↗
arXiv2024

A Comparative Study of Star Forming Dwarf Galaxies using the UVIT

We present a Far-Ultraviolet (FUV) study of sixteen star-forming dwarf galaxies (SFDGs) using the Ultraviolet Imaging Telescope (UVIT). Morphologically, SFDGs are classified as dwarf spirals, dwarf irregulars, and blue compact dwarfs (BCDs). We extracted the star-forming complexes (SFCs) from the sample galaxies, derived their sizes, and estimated the FUV+24$μm$ star formation rates (SFRs). We also determined the approximate stellar disk mass associated with the SFCs using IRAC 3.6-micron images. We derived the specific SFRs (sSFRs), as well as the SFR densities ($Σ(SFR)$) for the SFCs. We find that the lower $Σ(SFR)$ for each type is different, with the dwarf irregulars having the lowest $Σ(SFR)$ compared to others. However, the median size of the SFCs in the dwarf irregulars is the largest compared to the other two types when compared at roughly the same distance. We have derived the star-forming main sequence (SFMS) on the scale of SFCs for all three classes of SFDGs. We find that although all SFDGs approximately follow the global SFMS relation, i.e. $SFR\propto {M_{*}}^α$ (where globally $α\approx1$ for low surface brightness galaxies and $0.9$ for SFDGs), on the scale of SFCs the $α$ value for each type is different. The $α$ values for dwarf spirals, dwarf irregulars, and BCDs are found to be 0.74$\pm$0.13, 0.8$\pm$0.16, and 0.8$\pm$0.19, respectively. However, the age of all SFCs approximately corresponds to 1 Gyr. Finally, we find that the outer SFCs in most galaxies except BCDs have a high sSFR, supporting the inside-out model of galaxy growth.

astro-ph.GA↗
arXiv2023

A FUV and optical study of star formation in closely interacting galaxies: star forming rings, tidal arms and nuclear outflows

We present a study of the morphology of star formation and the associated nuclear activity in a sample of 8 closely interacting southern galaxies, which are in different stages of interaction, starting with nearly merged nuclei that have one prominent bulge to more widely spaced interacting galaxies. We have used Far-Ultraviolet (FUV) observations from the Ultraviolet Imaging telescope (UVIT), near-Infrared observations from the infrared survey facility telescope (IRSF) and archival optical data from the VLT/MUSE integral field spectrograph. Analysing resolved stellar populations across the disk of the interacting galaxies can provide unique insights into how interactions affect galaxy properties, such as morphology, star formation rates and chemical composition. We take advantage of the unprecedented capabilities of MUSE and UVIT to carry out a highly detailed spatially and spectrally resolved study of star formation rate, star formation histories, metallicity and AGN activity in the sample of eight interacting galaxies which are in different stages of interaction. Most of our sample galaxies are gas-rich and show evidence of recent, massive star formation in tidal tails, rings and spiral arms. This is evident from their FUV and H$α$ emissions, which trace young, massive star-forming regions. We compared the star formation rate in the barred and unbarred galaxies in our sample and found that the barred galaxies do not show significant enhancement in star formation rate or large-scale difference in star formation morphology compared to unbarred galaxies. IC5250 and NGC7733N, show extended nuclear outflows of size $\sim$ 5 kpc and 8 kpc respectively.

astro-ph.GA↗
arXiv2023

Clairaut slant Riemannian maps to Kähler manifolds

The aim of this article is to describe the idea of Clairaut slant Riemannian maps from Riemannian manifolds to Kähler manifolds. First, for the slant Riemannian map, we obtain the necessary and sufficient conditions for a curve to be a geodesic on the base manifold. Further, we find the necessary and sufficient conditions for the slant Riemannian map to be a Clairaut slant Riemannian map; for Clairaut slant Riemannian map to be totally geodesic; for the base manifold to be a locally product manifold. Further, we obtain the necessary and sufficient condition for the integrability of range of derivative map. Also, we investigate the harmonicity of Clairaut slant Riemannian map. Finally, we get two inequalities in terms of second fundamental form of a Clairaut slant Riemannian map and check the equality case.

math.DG↗
arXiv2023

Linking Alternative Fuel Vehicles Adoption with Socioeconomic Status and Air Quality Index

This is a study on the potential widespread usage of alternative fuel vehicles, linking them with the socio-economic status of the respective consumers as well as the impact on the resulting air quality index. Research in this area aims to leverage machine learning techniques in order to promote appropriate policies for the proliferation of alternative fuel vehicles such as electric vehicles with due justice to different population groups. Pearson correlation coefficient is deployed in the modeling the relationships between socio-economic data, air quality index and data on alternative fuel vehicles. Linear regression is used to conduct predictive modeling on air quality index as per the adoption of alternative fuel vehicles, based on socio-economic factors. This work exemplifies artificial intelligence for social good.

cs.AI↗
arXiv2021

Hidden in Plain Sight: UVIT and MUSE Discovery of a Large, Diffuse Star-Forming Galaxy

We report the discovery of a nearby large, diffuse galaxy that shows star formation, using Ultra Violet Imaging Telescope (UVIT) far-UV observations, archival optical data from Multi-Unit Spectroscopic Explorer (MUSE) and Dark Energy Camera Legacy Survey (DECaLS), and InfraRed Survey Facility (IRSF) near-infrared observations. The galaxy was not detected earlier due to its superposition with the background galaxy, NGC 6902A. They were together mistakenly classified as an interacting system. NGC 6902A is at a redshift of 0.05554, but MUSE observations indicate that the interacting tail is a separate star-forming, foreground galaxy at a redshift of 0.00980. We refer to the new galaxy as UVIT J202258.73-441623.8 (UVIT J2022). The near-infrared observations show that UVIT J2022 has a stellar mass of 8.7$\times$10$^{8}$M$_{\odot}$. Its inner disk (R$<$4 kpc) shows UV and H$α$ emission from ongoing massive star formation. The rest of the disk is extremely low luminosity, has a low stellar surface density, and extends out to a radius of R$\sim$9 kpc. The velocity and metallicity distribution maps and the star formation history indicate that UVIT J2022 has undergone three bursts of star formation. The latest episode is ongoing, which is supported by the presence of widespread H$α$ and UV emission in its inner disk. The galaxy also shows patchy spiral arms in far-UV, and there is a metallicity enhancement along a bar-like feature. UVIT J2022 is thus a unique example of triggered star formation in a diffuse galaxy, resulting in the growth of its inner stellar disk. Our study raises the intriguing possibility that (i) there could be similar diffuse galaxies that have been mistakenly interpreted as interacting galaxies due to their superposition, and (ii) UV or H$α$ could be a way to detect such diffuse galaxies in our local universe.

astro-ph.GA↗
arXiv2021

A Triple AGN in the NGC 7733-7734 Merging Group

Context: Galaxy interactions and mergers can lead to supermassive black hole (SMBH) binaries which become active galactic nuclei (AGN) pairs when the SMBHs start accreting mass. If there is a third galaxy involved in the interaction, then a triple AGN system can form. Aims: Our goal is to investigate the nature of the nuclear emission from the galaxies in the interacting pair NGC\,7733--NGC\,7734 using archival VLT/MUSE Integral field spectrograph data and study its relation to the stellar mass distribution traced by near-infrared (NIR) observations from the South African Astronomical Observatory (SAAO). Methods:We conducted near-infrared observations using the SAAO and identified the morphological properties of bulges in each galaxy. We used MUSE data to obtain a set of ionized emission lines from each galaxy and studied the ionization mechanism. We also examined the relation of the galaxy pair with any nearby companions with Far-UV observations using the UVIT. Conclusions: The emission line analysis from the central regions of NGC\,7733 and NGC\,7734 show Seyfert and LINER type AGN activity. The galaxy pair NGC\,7733--34 also shows evidence of a third component, which has Seyfert-like emission. Hence, the galaxy pair NGC\,7733--34 forms a triple AGN system. We also detected an Extended Narrow-line region (ENLR) associated with the nucleus of NGC\,7733.

astro-ph.GA↗