arXiv subjects

Ganesh Narayanan

Publications and source records attributed to Ganesh Narayanan.

7 recordsLinked to original sources

arXiv2025

Siren -- Advancing Cybersecurity through Deception and Adaptive Analysis

Siren represents a pioneering research effort aimed at fortifying cybersecurity through strategic integration of deception, machine learning, and proactive threat analysis. Drawing inspiration from mythical sirens, this project employs sophisticated methods to lure potential threats into controlled environments. The system features a dynamic machine learning model for realtime analysis and classification, ensuring continuous adaptability to emerging cyber threats. The architectural framework includes a link monitoring proxy, a purpose-built machine learning model for dynamic link analysis, and a honeypot enriched with simulated user interactions to intensify threat engagement. Data protection within the honeypot is fortified with probabilistic encryption. Additionally, the incorporation of simulated user activity extends the system's capacity to capture and learn from potential attackers even after user disengagement. Overall, Siren introduces a paradigm shift in cybersecurity, transforming traditional defense mechanisms into proactive systems that actively engage and learn from potential adversaries. The research strives to enhance user protection while yielding valuable insights for ongoing refinement in response to the evolving landscape of cybersecurity threats.

cs.CR↗

arXiv2024

The dynamical lineage of field ultra-diffuse galaxies

Ultra-diffuse galaxies (UDGs) exhibit morphological similarities with other low-luminosity galaxies indicating a possible evolutionary connection. We investigate for common dynamical characteristics of isolated, HI-rich UDGs with other low luminosity field galaxies, namely the low surface brightness galaxies (LSBs) and the dwarf irregulars (dIrrs). From the galaxy scaling relation studies, we note that UDGs and LSBs constitute statistically different populations. However, for UDGs and dIrrs, the null hypotheses of these statistical tests cannot be rejected : stellar mass versus atomic hydrogen mass; stellar mass versus dynamical mass; and dark matter core density versus core radius mass scaling. Interestingly, the dynamical models suggest that UDGs, LSBs and dIrrs constitute different galaxy populations as reflected by their radial-to-vertical velocity dispersion, and the rotational velocity-to-total stellar velocity dispersion. Finally, we observe that the total HI and stellar mass mostly regulate the variance in the structural and kinematical data both for the UDGs and dIrrs, while the ratio of radial-to-vertical velocity dispersion, and the total HI mass dominate the same in LSBs. UDGs and LSBs represent statistically different galaxy populations with respect to their mass and structural properties. But the fact that their structural parameters follow the same distributions is not ruled out. However, UDGs, dIrrs and LSBs constitute very different populations as far as their kinematical parameters are concerned. Finally, we note that the variation in the structural and kinematical data of both the UDGs and the dIrrs is mostly accounted for by their stellar mass and HI mass, whereas for the LSBs, the same is explained by the ratio of the radial-to-vertical stellar dispersion followed by the HI mass. Thus we conclude that the UDGs and dIrrs to share common dynamical lineage.

astro-ph.GA↗

arXiv2024

How does a low surface brightness galaxy form spiral arms?

The formation and evolution of spiral arms in low surface brightness galaxies (LSBs) are not well-understood. We study the dynamics of spiral arms in two prototypical LSBs, F568-VI and F568-01, using both analytical models and N-body + hydrodynamical simulations. We first consider the disk as a 2-component system of gravitationally-coupled stars and gas in the force field of a \emph{spherical} dark matter halo, subjected to local, non-axisymmetric perturbations. However, no local spirals are formed. We next assume the disk to be a 1-component system of stars in the net gravitational potential of a galaxy with a \emph{spherical} dark matter halo perturbed by a global $m=2$ instability. In this case, the growth time for spiral formation was low, equal to 0.78 and 0.96 Gyrs, respectively, corresponding to a few dynamical times of the galaxies. Finally, we simulate the LSBs using the N-body + hydrodynamical simulation code RAMSES. \emph{Our results show that a quadrupolar field associated with an oblate halo with an axial ratio of 0.7} is necessary to drive a long-lived global spiral in the LSB disks. Further, feedback corresponding to a supernova mass fraction of $\sim$ 0.05 is essential to comply with the observed stellar surface density. The simulated spirals survives for about ten dynamical times and the average pattern speed lies between 10 - 15 $\rm{kms^{-1}{kpc}^{-1}}$. The spiral arm thus formed is therefore a transient global pattern driven by the tidal field of the oblate dark matter halo.

astro-ph.GA↗

arXiv2023

Analyzing the cosmic architecture in the vicinity of Grand-design and Flocculent spiral galaxies with Local Geometric Index

We explore the environment of 351 grand-design and 541 flocculent spiral galaxies recently identified employing convolutional neural networks from the $17^{th}$ data release of Sloan Digital Sky Survey. We introduce a novel estimator called the Local Geometric Index to quantify the morphology of the local environment of these 892 spirals. Based on the local geometric index of the galaxies, we identify their local environments to be voids, sheets, filaments or clusters. We find that grand-designs are mostly located in dense environments like clusters and filaments ($\sim 76\%$), whereas a reasonable fraction of the flocculents lie in sparse environments like voids and sheets ($\sim 45\%$). A $p$-value $<$ $10 ^{-10}$ from a Kolmogorov-Smirnov test indicates that our results are statistically significant at $99.9\%$ confidence level. Further, we note that dense environments with large tidal flows are dominated by the grand-designs. Metal-poor environments, such as sheets and voids, with a high abundance of gas clouds, on the other hand, are mostly populated by the flocculents.

astro-ph.GA↗

arXiv2023

Analyzing the cosmic web environment in the vicinity of grand-design and flocculent spirals with local geometric index

We explore the environment of a combined set of $367$ grand-design and $619$ flocculent spiral galaxies. We introduce a novel estimator called the \textit{local geometric index} to quantify the morphology of the local environment of these $986$ spirals. The local geometric index allows us to classify the environment of galaxies into voids, sheets, filaments, and clusters. We find that grand-designs are mostly located in dense environments like clusters and filaments ($\sim 78\%$), whereas the fraction of the flocculents lying in sparse environments like voids and sheets is significantly higher ($ > 10\%$) than that of the grand-designs. A $p$-value $<$ $10 ^{-3}$ from a Kolmogorov-Smirnov test indicates that our results are statistically significant at $99.9\%$ confidence level. Further, we note that dense environments with large tidal flows are dominated by the grand-designs. On the other hand, low-density environments such as sheets and voids favor the growth of flocculents.

astro-ph.GA↗

arXiv2022

Identification of Grand-design and Flocculent Spirals from SDSS using Convolutional Neural network

Spiral galaxies can be classified into the {\it Grand-designs} and {\it Flocculents} based on the nature of their spiral arms. The {\it Grand-designs} exhibit almost continuous and high contrast spiral arms and are believed to be driven by density waves, while the {\it Flocculents} have patchy and low-contrast spiral features and are primarily stochastic in origin. We train a convolutional neural network (CNN) model to classify spirals into {\it Grand-designs} and {\it Flocculents}, with a testing accuracy of $\mathrm{97.2\%}$. We then use the above model for classifying $\mathrm{1,354}$ new spirals from the SDSS. Out of these, $\mathrm{721}$ were identified as {\it Flocculents}, and the rest as {\it Grand-designs}. We find the median asymptotic rotational velocities of our newly classified {\it Grand-designs} and {\it Flocculents} are $218 \pm 86$ and $145 \pm 67$ respectively, indicating that the {\it Grand-designs} are mostly the high-mass and the {\it Flocculents} the intermediate-mass spirals. This is further corroborated by the observation that the median morphological indices of the {\it Grand-designs} and {\it Flocculents} are $2.6 \pm 1.8$ and $4.7 \pm 1.9$ respectively, implying that the {\it Flocculents} primarily consist of a late-type galaxy population in contrast to the {\it Grand-designs}. Finally, an almost equal fraction of of bars $\sim$ 0.3 in both the classes of spiral galaxies reveals that the presence of a bar component does not regulate the type of spiral arm hosted by a galaxy. Our results may have important implications for formation and evolution of spiral arms in galaxies.

astro-ph.GA↗

arXiv2022

Are superthin galaxies low surface brightness galaxies seen edge-on? The star formation probe

Superthin galaxies (STs) are edge-on disc galaxies with strikingly high planar-to-vertical axes ratios of $\sim 10 - 20$ with no bulge component, and central surface brightness in $B$-band $>$ 23 mag arcsec$^{-2}$ comparable to low surface brightness galaxies (LSBs). Although STs and LSBs have similar dynamical, stellar and atomic hydrogen (HI) masses on an average, it is tricky to conclude if they constitute the same galaxy population, given the edge-on and face-on orientations of the STs and the LSBs respectively. We systematically study star formation rate (SFR) in a sample of STs and LSBs using SED fitting of photometric data in ten bands including GALEX: FUV, NUV, SDSS: u,g,r,i,z \& 2MASS: J, H, Ks using stellar population synthesis models employing the publicly-available software MAGPHYS (Multi-Wavelength Analysis of Galaxy Physical Properties). The estimated median SFRs for LSBs and STs are $0.4^{+2.2}_{-0.3} $ $M_{\odot}yr^{-1}$ \& $0.2^{+0.9}_{-0.2}$ $M_{\odot}yr^{-1}$ respectively. Our calculations indicate that this deficit in the SFR of an ST can be attributed to inclination and opacity effects. Therefore, we conclude that STs and LSBs have equal intrinsic SFR over and above other physical properties, which possibly implies that STs are just LSBs seen in edge-on.

astro-ph.GA↗