arXiv subjects

C. Mondal

Publications and source records attributed to C. Mondal.

At least 19 recordsLinked to original sources

arXiv2024

Study of Star-formation in Dual Nuclei Galaxies using UVIT observations

We have used the Ultraviolet Imaging Telescope (UVIT) aboard AstroSat to study star formation in a sample of nine dual nuclei galaxies with separations ~11 kpc, which is an expected outcome of galaxy mergers. To minimize the contribution of active galactic nuclei (AGN) emission, we have used mid-IR color cut-offs and masked the AGN-dominated nuclei. The UV continuum slope ($β$) is used to calculate the internal extinction (A$_V$) which ranges from 0.53 to 4.04 in the FUV band and 0.44 to 3.10 in the NUV band for the sample. We have detected $1-20$ star-forming clumps (SFCs) in our sample galaxies. The extinction-corrected total FUV star-formation rate (SFR) ranges from $\sim$0.35 to $\sim$32 M$_\odot$ yr$^{-1}$. Our analyses of A$_V$, specific SFR (sSFR) show that dual nuclei sources are associated with dusty, star-forming galaxies. The FUV$-$NUV color maps show redder color in the nuclear and disk regions while bluer color is observed in the outskirts of most galaxies which can be due to embedded dust or different stellar populations. We have found some signatures of possible stellar/AGN feedback like a ring of star formation, a redder ring around blue nuclei, etc. However, further observations are required to confirm this.

astro-ph.GA↗

arXiv2023

Detectability of a phase transition in neutron star matter with third-generation gravitational wave interferometers

Possible strong first-order hadron-quark phase transitions in neutron star interiors leave an imprint on gravitational waves, which could be detected with planned third-generation interferometers. Given a signal from the late inspiral of a binary neutron star (BNS) coalescence, %the possibility of assessing the presence of such a phase transition depends on the precision that can be attained in the determination of the tidal deformability parameter, as well as on the model used to describe the hybrid star equation of state. For the latter, we employ here a phenomenological meta-modelling of the equation of state that largely spans the parameter space associated with both the low density phase and the quark high density compatible with current constraints. We show that with a network of third-generation detectors, a single loud BNS event might be sufficient to infer the presence of a phase transition at low baryon densities with an average Bayes factor $B\approx 100$, up to a luminosity distance ($\mathcal{D}_L \lesssim$ 300 Mpc).

astro-ph.HE↗

arXiv2023

Relativistic approach for the determination of nuclear and neutron star properties in consideration of PREX-II results

The bulk properties of nuclear matter and neutron stars with the newly generated relativistic interaction DBHP are investigated which provides an opportunity to modify the coupling parameters keeping in view the finite nuclei, nuclear matter, PREX-II data for neutron skin thickness in $^{208}$Pb and astrophysical constraints. The relativistic interaction has been generated by including all possible self and mixed interactions between $σ$, $ω$, and $ρ$-meson up to the quartic order satisfying the naturalness behavior of parameters. A covariance analysis is performed to assess the statistical uncertainties on the model parameters and observables of interest along with correlations amongst them. We obtained a value of neutron skin thickness for $^{208}$Pb nucleus $Δr_{np}$ = 0.24 $\pm$ 0.02 fm. The maximum gravitational mass of neutron star and radius corresponding to the canonical mass ($R_{1.4}$) come out to be 2.03 $\pm$ 0.04 M$\odot$ and 13.39 $\pm$ 0.41 km respectively. The dimensionless tidal deformability, $Λ$ for a neutron star is also analyzed.

nucl-th↗

arXiv2022

Effect of isovector scalar meson on equation of state of dense matter within relativistic mean field model

The effects of the isovector-scalar $δ$-meson field on the properties of finite nuclei, infinite nuclear matter and neutron stars are investigated within the Relativistic Mean Field (RMF) model which includes non-linear couplings. Several parameter sets (SRV's) are generated to asses the influence of $δ$-meson on the properties of neutron star. These parametrizations correspond to different values of coupling constant of $δ$-meson to the nucleons with remaining ones calibrated to yield finite nuclei and infinite nuclear matter properties consistent with the available experimental data. It is observed that to fit the properties of finite nuclei and infinite nuclear matter, a stronger coupling between isovector-vector $ρ$ meson and nucleons is required in the presence of $δ$ field. Furthermore, the $δ$-meson is found to affect the radius of canonical neutron star significantly. The value of dimensionless tidal deformability, $Λ$ for the canonical neutron star also satisfies the constraints from the waveform models analysis of GW170817 binary neutron star merger event. A covariance analysis is performed to estimate the statistical uncertainties of the model parameters as well as correlations among the model parameters and different observables of interest.

nucl-th↗

arXiv2022

Bayesian reconstruction of nuclear matter parameters from the equation of state of neutron star matter

The nuclear matter parameters (NMPs), those underlie in the construction of the equation of state (EoS) of neutron star matter, are not directly accessible. The Bayesian approach is applied to reconstruct the posterior distributions of NMPs from the EoS of neutron star matter. The constraints on lower-order parameters as imposed by the finite nuclei observables are incorporated through appropriately chosen prior distributions. The calculations are performed with two sets of pseudo data on the EoS whose true models are known. The median values of second or higher order NMPs show sizeable deviations from their true values and associated uncertainties are also larger. The sources of these uncertainties are intrinsic in nature, identified as (i) the correlations among various NMPs and (ii) the variations in the EoS of symmetric nuclear matter, symmetry energy, and the neutron-proton asymmetry in such a way that the neutron star matter EoS remain almost unaffected.

nucl-th↗

arXiv2021

Analysis of critical parameters for nonrelativistic models in symmetric nuclear matter

In this work we have analyzed several features of symmetric nuclear matter (SNM) at finite temperature described by different zero- and finite-range nonrelativistic families of models, namely, Skyrme, Gogny, Momentum-dependent interaction (MDI), Michigan three-range Yukawa (M3Y) and Simple Effective Interaction (SEI). We have calculated the critical parameters (CP) associated to the liquid-gas phase coexistence for nuclear matter from these parametrizations and show that they are in agreement with their experimental and theoretical values obtained in the literature. Our study also points out to a strong evidence of universality presented by the hadronic models, namely, model independence in the gaseous phase and distinguishability among different interactions in the liquid phase. We have performed a correlation study among different CP and SNM properties. Such studies involving different finite range interactions are scarce in literature. The analyzed models show an overall increasing trend of the critical temperature as a function of critical pressure.

nucl-th↗

arXiv2021

UVIT-HST-Gaia-VISTA study of KRON 3 in the Small Magellanic Cloud: A cluster with an extended red clump in UV

We have demonstrated the advantage of combining multi-wavelength observations, from the ultraviolet (UV) to near-infrared, to study Kron 3, a massive star cluster in the Small Magellanic Cloud. We have estimated the radius of the cluster Kron 3 to be 2.'0 and for the first time, we report the identification of NUV-bright red clump (RC) stars and the extension of the RCin colour and magnitude in the NUV vs (NUV-optical) colour-magnitude diagram (CMD). We found that extension of the RC is an intrinsic property of the cluster and it is not due to contamination of field stars or differential reddening across the field. We studied the spectral energy distribution of the RC stars and estimated a small range in temperature ~5000 - 5500K, luminosity ~60 - 90 Land radius ~8.0 - 11.0 Supporting their RC nature. The range of UV magnitudes amongst the RC stars (~23.3 to 24.8 mag) is likely caused by the combined effect of variable mass loss, variation in initial helium abundance (Y_ini=0.23 to 0.28), and a small variation in age (6.5-7.5 Gyr) and metallicity ([Fe/H]=-1.5 to -1.3). Spectroscopic follow-up observations of RC stars in Kron 3 are necessary to confirm the cause of the extended RC.

astro-ph.GA↗

arXiv2020

More insights into bar quenching. Multi-wavelength analysis of four barred galaxies

The underlying nature of the process of star formation quenching in the central regions of barred disc galaxies that is due to the action of stellar bar is not fully understood. We present a multi-wavelength study of four barred galaxies using the archival data from optical, ultraviolet, infrared, CO, and HI imaging data on star formation progression and stellar and gas distribution to better understand the process of bar quenching. We found that for three galaxies, the region between the nuclear or central sub-kiloparsec region and the end of the bar (bar region) is devoid of neutral and molecular hydrogen. While the detected neutral hydrogen is very negligible, we note that molecular hydrogen is present abundantly in the nuclear or central sub-kiloparsec regions of all four galaxies. The bar co-rotation radius is also devoid of recent star formation for three out of four galaxies. One galaxy shows significant molecular hydrogen along the bar, which might mean that the gas is still being funnelled to the centre by the action of the stellar bar. Significant star formation is also present along the bar co-rotation radius of this galaxy. The study presented here supports a scenario in which gas redistribution as a result of the action of stellar bar clears the bar region of fuel for further star formation and eventually leads to star formation quenching in the bar region.

astro-ph.GA↗

arXiv2020

Structure and composition of inner crust of neutron stars from Gogny interactions

The detailed knowledge of the inner crust properties of neutron stars might be important to explain different phenomena such as pulsar glitches or the possibility of an {\it r-process} site in neutron star mergers. It has been shown in the literature that quantal effects like shell correction or pairing may play a relevant role to determine the composition of the inner crust of the neutron star. In this paper we construct the equation of state of the inner crust using the finite-range Gogny interactions, where the mean field and the pairing field are calculated with same interaction. We have used the semiclassical Variational Wigner-Kirkwood method along with shell and pairing corrections calculated with the Strutinsky integral method and the BCS approximation, respectively. Our results are compared with those of some popular models from the literature. We report a unified equation of state of the inner crust and core computed with the D1M* Gogny force, which was specifically fabricated for astrophysical calculations.

nucl-th↗

arXiv2019

Tides in merging neutron stars: Consistency of the GW170817 event with experimental data on finite nuclei

The agreement of the nuclear equation of state (EoS) deduced from the GW170817 based tidal deformability with the one obtained from empirical data on microscopic nuclei is examined. It is found that suitably chosen experimental data on isoscalar and isovector modes of nuclear excitations together with the observed maximum neutron star mass constrain the EoS which displays a very good congruence with the GW170817 inspired one. The giant resonances in nuclei are found to be instrumental in limiting the tidal deformability parameter and the radius of neutron star in somewhat narrower bounds. At the 1$σ$ level, the values of the canonical tidal deformability $Λ_{1.4}$ and the neutron star radius $R_{1.4}$ come out to be $267\pm144$ and $11.6\pm1.0$ km, respectively.

nucl-th↗

arXiv2018

Insights on bar quenching from a multi-wavelength analysis: The case of Messier 95

The physical processes related to the effect of bar in the quenching of star formation in the region between the nuclear/central sub-kpc region and the ends of the bar (bar-region) of spiral galaxies is not fully understood. It is hypothesized that the bar can either stabilize the gas against collapse, inhibiting star formation or efficiently consume all the available gas, with no fuel for further star formation. We present a multi-wavelength study using the archival data of an early-type barred spiral galaxy, Messier 95, which shows signatures of suppressed star formation in the bar-region. Using the optical, ultraviolet, infrared, CO and HI imaging data we study the pattern of star formation progression, stellar/gas distribution and try to provide insights on the process responsible for the observed pattern. The FUV$-$NUV pixel colour map reveals a cavity devoid of UV flux in the bar-region that interestingly matches with the length of the bar ($\sim$ 4.2kpc). The central nuclear region of the galaxy is showing a blue color clump and along the major-axis of the stellar bar the colour progressively becomes redder. Based on a comparison to single stellar population models, we show that the region of galaxy along the major-axis of the bar (unlike the region outside the bar) is comprised of stellar populations with ages $\geq$ 350 Myr, with a star-forming clump in the center of younger ages ($\sim$ 150Myr). Interestingly the bar-region is also devoid of neutral and molecular hydrogen but with an abundant molecular hydrogen present at the nuclear region of the galaxy. Our results are consistent with a picture in which the stellar bar in Messier 95 is redistributing the gas by funneling gas inflows to nuclear region, thus making the bar-region devoid of fuel for star formation.

astro-ph.GA↗

arXiv2018

The nucleon effective mass and its isovector splitting

Using an energy density functional (EDF) based on the thermodynamic Gibbs-Duhem relation, found equivalent to the standard Skyrme EDF for infinite nuclear matter, it is demonstrated that the parameters of this EDF are not uniquely determined from the fit of the empirical and theoretical data related to nuclear matter. This prevents an unambiguous determination of the nucleon effective mass ($\frac{m_0^*}{m}$) and its isovector splitting ($Δm_0^*$). Complementary information from dipole polarizability of atomic nuclei helps in removing this ambiguity and plausible values of $\frac{m_0^*}{m}$ and $Δm_0^*$ can be arrived at. Presently considered fit data on infinite nuclear matter and dipole polarizability of finite nuclei yield $\frac{m_0^*}{m} =0.68 \pm 0.04 $ and $Δm_0^* =(-0.20 \pm 0.09)δ$. This EDF is consistent with the constraint on the maximum mass of the neutron star.

nucl-th↗

arXiv2018

Gogny forces in the astrophysical context

The most successful Gogny interactions of the D1 family, namely D1S, D1N and D1M, suffer the common problem of a too soft neutron matter equation of state at high density, which prevents them from predicting a maximal mass of neutron stars of two solar masses, as required by recent astronomical observations. To cure this deficiency, we have proposed recently a reparametrization of the D1M force by fine tuning the slope of the symmetry energy in such a way that it preserves the ground-state properties of D1M in finite nuclei and also describes successfully the global properties of neutron stars, in particular its maximal mass, in consonance with the observational data. In this contribution we revisit this reparametrization by discussing two modified Gogny forces, dubbed D1M$^*$ and D1M$^{**}$.

nucl-th↗

arXiv2018

Correlations among symmetry energy elements in Skyrme models

Motivated by the interrelationships found between the various symmetry energy elements of the energy density functionals (EDF) based on the Skyrme forces, possible correlations among them are explored. A total of 237 Skyrme EDFs are used for this purpose. As some of these EDFs yield values of a few nuclear observables far off from the present acceptable range, studies are done also with a subset of 162 EDFs that comply with a conservative set of constraints on the values of nuclear matter incompressibility coefficient, effective mass of the nucleon and the isovector splitting of effective nucleon masses to see the enhancement of the correlation strength, if any. The curvature parameter $K^0_{sym}$ and the skewness parameter $Q^0_{sym}$ of the symmetry energy are found to be very well correlated with the linear combination of the symmetry energy coefficient and its density derivative $L_0$ . The isovector splitting of the effective nucleon mass, however, displays a somewhat meaningful correlation with a linear combination of the symmetry energy, its slope and its curvature parameter.

nucl-th↗

arXiv2018

Ultra-Violet Imaging Telescope Observations of the Star-Forming Ring in NGC7252: Evidence of Possible AGN Feedback Suppressing Central Star Formation

Some post-merger galaxies are known to undergo a starburst phase that quickly depletes the gas reservoir and turns it into a red-sequence galaxy, though the details are still unclear. Here we explore the pattern of recent star formation in the central region of the post-merger galaxy NGC7252 using high resolution UV images from the UVIT on ASTROSAT. The UVIT images with 1.2 and 1.4 arcsec resolution in the FUV and NUV are used to construct a FUV-NUV colour map of the central region. The FUV-NUV pixel colour map for this canonical post-merger galaxy reveals a blue circumnuclear ring of diameter $\sim$ 10 " (3.2 kpc) with bluer patches located over the ring. Based on a comparison to single stellar population models, we show that the ring is comprised of stellar populations with ages $\lesssim$ 300 Myr, with embedded star-forming clumps of younger age ($\lesssim$ 150Myr). The suppressed star formation in the central region, along with the recent finding of a large amount of ionised gas, leads us to speculate that this ring may be connected to past feedback from a central super-massive black hole that has ionised the hydrogen gas in the central $\sim$ 4" $\sim$ 1.3 kpc.

astro-ph.GA↗

arXiv2017

Interdependence of different symmetry energy elements

Relations between the nuclear symmetry energy coefficient and its density derivatives are derived. The relations hold for a class of interactions with quadratic momentum dependence and a power-law density dependence. The structural connection between the different symmetry energy elements as obtained seems to be followed by almost all reasonable nuclear energy density functionals, both relativistic and non-relativistic, suggesting a universality in the correlation structure. This, coupled with known values of some well-accepted constants related to nuclear matter, helps in constraining values of different density derivatives of the nuclear symmetry energy shedding light on the isovector part of the nuclear interaction.

nucl-th↗

arXiv2017

In-orbit Calibrations of the Ultra-Violet Imaging Telescope

The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in ASTROSAT, the first Indian Space Observatory. The UVIT instrument has two 375mm telescopes: one for the far-ultraviolet (FUV) channel (1300--1800Å), and the other for the near-ultraviolet (NUV) channel (2000--3000Å) and the visible (VIS) channel (3200--5500Å). UVIT is primarily designed for simultaneous imaging in the two ultraviolet channels with spatial resolution better than 1.8 arcsec, along with provision for slit-less spectroscopy in the NUV and FUV channels.The results of in-orbit calibrations of UVIT are presented in this paper.

astro-ph.IM↗

arXiv2017

Quark Wigner distributions and spin-spin correlations

We investigate the Wigner distributions for $u$ and $d$ quarks in a light-front quark-diquark model of a proton to unravel the spatial and spin structure. The light-front wave functions are modeled from the soft-wall AdS/QCD prediction. We consider the contributions from both the scalar and the axial vector diquarks. The Wigner distributions for unpolarized, longitudinally polarized, and transversely polarized protons are presented in the transverse momentum plane as well as in the transverse impact parameter plane. The Wigner distributions satisfy a Soffer-bound-type inequality. We also evaluate all the leading twist GTMDs and show their scale evolution. The spin-spin correlations between the quark and the proton are investigated

hep-ph↗