arXiv subjects

Suvodip Mukherjee

Publications and source records attributed to Suvodip Mukherjee.

At least 37 records · Page 2Linked to original sources

arXiv2026

Modified Cosmology or Modified Galaxy Astrophysics is Driving the z>6 JWST Results? CMB Experiments can discover the Origin in the Near Future

The massive and bright galaxies observed by the James Webb Space Telescope (JWST) at high redshifts ($z > 6$) have challenged our understanding of the Universe. This may require revisiting the physics of galaxy formation and evolution, or modifying the $Λ$CDM cosmological model to explain these observations, or both. We show that high-resolution CMB experiments such as the Simons Observatory (or CMB-S4) can measure smoking-gun signatures jointly in weak lensing and kinematic Sunyaev-Zeldovich (kSZ) power spectra, which can shed light on both these scenarios. An increase in the matter power spectrum at small scales will enhance the number density of dark matter halos at high redshifts, thereby increasing the galaxy formation rate. This will cause enhanced weak lensing signal from these redshifts and also lead to enhanced patchy-kSZ signal from the epoch of reionization. However, if only galaxy astrophysics is modified, without any modification in the matter power spectrum, then the patchy-kSZ signal gets altered, while the weak lensing signal remains nearly unaltered. We show that we can measure the modified astrophysical and cosmological scenarios at a statistical significance of $10.4σ$ (and $29.8σ$) from Simons Observatory (and CMB-S4), which will enable a conclusive understanding on what physical process is driving the high-redshift observations of JWST.

astro-ph.CO↗

arXiv2026

The First Upper Bound on the Nano-Hertz Gravitational Waves and Galaxy Cross-Correlation signal using 15-year NANOGrav Data and DESI Galaxy Survey

The recent detection of a common-spectrum stochastic signal by multiple pulsar timing array (PTA) collaborations has provided tentative evidence for a nanohertz (nHz) stochastic gravitational-wave background (SGWB). This signal can be widely interpreted as originating from a cosmic population of inspiraling supermassive black hole binaries (SMBHBs). Current PTA analyses primarily constrain the SGWB power spectrum and its auto-angular power spectrum. However, the supermassive black holes will produce an underlying correlation with the large-scale structure of the Universe, which can help in understanding the formation and evolution of the binaries. In this work, we develop a new analysis pipeline PyGxGW-PTA for studying the cross-correlation of nHz GW signal with galaxy surveys ($C^{\rm g\, GW}_\ell$) and obtain the first constraint on the SGWB and galaxy distribution cross-correlation using the NANOGrav 15-year dataset in combination with the DESI galaxy catalog. We find no statistically significant correlation between the SGWB and the large-scale distribution of DESI galaxies and using an optimal estimator we put an upper bound on $C^{\rm g\, GW}_{\ell=8} < 0.0083$ at $95\%$ C.I. This yields the first observational upper limit on the spatial correlation between the nHz SGWB and the large-scale structure of the Universe, establishing the observational groundwork for future multi-tracer analyses that will combine PTA data with next-generation galaxy surveys to unveil the SMBHB-galaxy correlation.

astro-ph.CO↗

arXiv2025

The Route to Unveil the Cosmic Genealogy of Supermassive Black Hole Binaries Using Nano-Hertz Gravitational Waves and Galaxy Surveys

The nano-hertz (nHz) stochastic gravitational wave background (SGWB), generated by unresolved supermassive black hole binaries (SMBHBs), provides a unique probe of their population and its cosmic evolution. In this work, we explore the potential of uncovering the SMBHB population and its redshift dependence by combining the SGWB signal and its anisotropies with galaxy distribution through cross-correlation analyses. Using a Fisher analysis technique, we show that the SGWB power spectrum alone can not provide any information on the evolutionary history of SMBHBs, whereas the inclusion of the angular power spectrum of the SGWB and its cross-correlation with the galaxy distribution substantially improves constraints on the redshift evolution parameters. Assuming pulsar timing array (PTA) configurations achievable in the Square Kilometre Array (SKA) era, we find that the combined use of isotropic and anisotropic SGWB signals, together with galaxy surveys, can provide valuable measurements of the redshift evolution of the SMBH-galaxy connection and the frequency distribution of SMBHBs. These results highlight the potential of joint GW-galaxy studies to address the long-standing open question of SMBH growth and evolution across cosmic time.

astro-ph.CO↗

arXiv2025

The Phase Space of Low-Mass Binary Compact Objects from LIGO-Virgo-KAGRA Catalog: Hints on the Chances of Different Formation Scenarios

Gravitational wave (GW) observations have significantly advanced our understanding of binary compact object (BCO) formation, yet directly linking these observations to specific formation scenarios remains challenging. The BCO phase space provides a robust and data-driven approach to discover the likely formation scenarios of these binaries. In this study, we expand the previously introduced binary black hole phase space technique to encompass low-mass compact objects (LMCOs), establishing a novel framework to investigate their diverse formation mechanisms. Applying this approach to selected low-mass events $(\lesssim 5 M_\odot)$ from the GWTC-3 catalog and the recently observed GW230529 event, we show for the first time the phase space demonstration of the LMCOs and find the associated probabilities for different formation scenarios including neutron star, astrophysical black hole, or primordial black hole. Our analysis includes the astrophysical modelling uncertainties in and how it causes degeneracy between different formation scenarios. In future, with improvements in GW detector sensitivity and with detection of more GW events, the LMCO phase space framework will significantly strengthen our capacity to associate more likely formation scenarios over the other, thereby refining our understanding of compact object formation for both astrophysical and primordial scenarios, and its evolution across the cosmic redshift.

astro-ph.HE↗

arXiv2025

An Accurate Modeling of Nano-hertz Gravitational Wave Signal from Eccentric Supermassive Binary Black Holes: An Essential Step Toward a Robust Discovery

The stochastic gravitational wave background (SGWB) in the nanohertz (nHz) regime, detectable by pulsar timing arrays (PTAs), provides a promising probe of the cosmic population of supermassive black hole binaries (SMBHBs). These binaries are expected to retain significant eccentricity throughout their evolution. We present a new technique to model the nHz SGWB by incorporating eccentricity into a multi-scale adaptive simulation framework. Using the time-domain eccentric waveform model ESIGMAHM, we generate realistic GW signals from astrophysical populations of SMBHBs. Unlike circular binaries, eccentric systems emit across multiple frequencies, introducing spectral correlations between frequency bins. These correlations provide a novel observational signature of the eccentricity distribution of the SMBHB population. In this work, we adopt simplified power-law models for the eccentricity distribution. While this does not capture the full complexity of galactic environments, it effectively highlights the key features of GW emission from eccentric binaries and their imprint on the SGWB. Our approach advances nHz GW signal modeling by incorporating eccentricity at small scales, enabling more realistic predictions and offering a new avenue for probing SMBHB astrophysics with future PTA observations.

astro-ph.CO↗

arXiv2025

Binary Black Hole Phase Space Discovers the Signature of Pair Instability Supernovae Mass Gap

The rapidly expanding catalog of gravitational-wave detections provides a powerful probe of the formation history of compact binaries across cosmic time. In this work, we extend the Binary Compact Object (BCO) phase-space framework to the full set of events in the GWTC-4 catalog to map the observed binary formation scenarios in a data-driven way. Applying this framework, we identify distinct regions of phase-space associated with different channels and discover for the first time a unique mass-cutoff scale in a data-driven way. The mapping of these on different formation channels reveals a population of first-generation (1G) black holes sharply truncated at approximately 45.5 $M_\odot$, consistent with the theoretically predicted pair-instability supernova (PISN) mass gap. These findings demonstrate the capability of the BCO phase-space to disentangle overlapping formation pathways, establish robust connections between gravitational-wave observations and binary evolution, and highlight the potential of upcoming observing runs to reveal rare populations and exotic origins.

astro-ph.HE↗

arXiv2025

The Prospect from the Upcoming CMB Experiment LiteBIRD to Discover Axion-like Particles Using Milky Way

The existence of axion-like particles (ALPs) can be probed from their signatures in the Cosmic Microwave Background (CMB) due to the photon-ALP resonant conversion over the mass range of ALPs that matches with the effective mass of photons in the plasma in the astrophysical systems. Such a conversion can also occur in the Milky Way halo and disk and can cause a unique spatial and spectral distortion. The signal is highly non-Gaussian and cannot be measured precisely by the usual power-spectrum approach. We devise a new technique to search for this signal from the upcoming full-sky CMB experiment LiteBIRD using its multi-frequency band using a template-based spatial profile of the ALP distortion signal. This technique captures the large-scale non-Gaussian aspects of the ALP distortion signal in terms of a spatial template and makes it possible to search for any non-zero ALP signal. We show that the inference of the ALP coupling using the template-based technique from LiteBIRD can provide constraints on the coupling constant approximately $ g_{aγ} < 6.5 \times 10^{-12} \, \mathrm{GeV}^{-1}$ for ALP masses below $10^{-14}$ eV at 95\% confidence interval which is an order of magnitude better than the current bounds from CERN Axion Solar Telescope (CAST) at $g_{aγ} < 6.6 \times 10^{-11} \, \mathrm{GeV}^{-1}$, This shows the capability of future multi-band CMB experiment LiteBIRD in opening the discovery space towards physics beyond the standard model.

astro-ph.CO↗

arXiv2025

Gravitational Wave Burst from Bremsstrahlung in Milky Way Can Discover Sub-Solar Dark Matter in Near Future

What is Dark Matter, and what is its concentration in the Milky Way remains an open question in physics. We show that if a significant fraction of dark matter is composed of sub-solar mass primordial black holes (PBHs), gravitational bremsstrahlung resulting from hyperbolic encounters between unbound PBHs within the galactic halos can generate distinctive chromatic gravitational-wave (GW) emission concentrated around the galactic dark matter halo, and it provides a direct window to discover such compact objects. We find that for both generalized NFW and Einasto dark matter profiles of Milky Way, the signal-to-noise ratio can be more than five in one year of observation for the upcoming ground based GW observatories Cosmic Explorer if PBH dark matter fraction $f_{\rm PBH} = 1$ over the mass range $10^{-14} M_\odot \lesssim m_{\rm PBH} \lesssim 10^{-8} M_\odot$. Our results show that the Galactic Center could appear as a GW-bright source, enabling new insights into dark matter and its distribution.

astro-ph.CO↗

arXiv2025

A New Gravitational Wave Probe to the Nature of Dark Energy from the Aging of the Universe

One of the most dominant energy budgets in the Universe is Dark Energy, which remains enigmatic since its existence was first claimed based on observations of late-time cosmic acceleration. We propose a new way of inferring the dark energy equation of state (EoS) by measuring the aging of the Universe using only gravitational wave (GW) signals from coalescing binary compact objects of any masses. We show that the behavior of dark energy as the Universe ages will lead to a change in the observed chirp mass of GW sources inferred from observations of different stages of their coalescence. This change can be studied by monitoring a coherent source over a few years, with two well-separated GW frequencies. With a coordinated network of GW detectors that can reach a sensitivity of Big Bang Observer, we can reach a $5σ$ detection of the dark energy EoS parameter $w_0=-1$ and its variation with cosmic time by using stellar origin binary black holes and binary neutron stars up to high redshift over 10 years of observation time without using any external calibrator. If the next generation of GW detectors can achieve this precision, then it can open a new window to discover the fundamental nature of dark energy.

astro-ph.CO↗

arXiv2025

The First Model-Independent Chromatic Microlensing Search: No Evidence in the Gravitational Wave Catalog of LIGO-Virgo-KAGRA

The lensing of Gravitational Waves (GWs) due to intervening matter distribution in the universe can lead to chromatic and achromatic signatures in the wave-optics and geometrical-optics limit respectively. This makes it difficult to model for the unknown mass distribution of the lens and hence requires a model-independent lensing detection technique from GW data. We perform the first model-independent microlensing search in the wave-optics limit on the 72 super-threshold GW events observed with both the LIGO detectors up to the third observation catalog GWTC-3 of LIGO-Virgo-KAGRA using the analysis method $μ$-\texttt{GLANCE}. These unmodelled searches pick up one plausible candidate $\rm GW190408\_181802$ with a slightly above threshold residual amplitude compared to the residual expected from detector noise. However, exploring the microlensing modulation signatures on this event, we do not find any conclusive evidence of the microlensing signal in the data. With this, we confidently rule out the presence of any statistically significant microlensing signal in the 72 events up to GWTC-3 in a model-independent way.

gr-qc↗

arXiv2025

Illuminating Dark Energy with Bright Standard Sirens from Future Detectors

Understanding the nature and evolution of dark energy (DE) is a central challenge in modern cosmology. In this work, we explore the constraining power of bright standard sirens -- gravitational wave (GW) events with electromagnetic counterparts - for probing the DE equation of state as function of redshift. Focusing on future GW observations from next-generation ground-based GW detectors such as the Einstein Telescope and Cosmic Explorer, we perform a comprehensive analysis using simulated binary neutron star (BNS) and neutron star-black hole (NSBH) events over five years of observation with a $75\%$ duty cycle. We consider three broad classes of DE models: (i) phenomenological parametrizations, specifically the Barboza-Alcaniz extension to the Chevallier-Polarski-Linder model; (ii) physically motivated scalar field scenarios, specifically hilltop quintessence; and (iii) evolving dark matter setup in which the matter density evolves as $(1+z)^{3+α}$. For each case, we jointly infer the Hubble constant $H_0$ and model-specific DE parameters from the observed GW luminosity distances and spectroscopic redshifts. Our results demonstrate that bright sirens alone can yield competitive and independent constraints on the time evolution of DE indicating that multi-messenger cosmology has the potential to test a wide range of DE theories, bridging phenomenological and physically motivated models, and paving the way for precision cosmology in the era of GW astronomy.

astro-ph.CO↗

arXiv2025

Discovering the Dispersion of Gravitational Waves using Multi-Band Observation including Deci-Hertz: A Unique Probe to Cosmic Acceleration

The dispersion in the speed of gravitational waves is a novel way to test the general theory of relativity and understand whether the origin of cosmic acceleration is due to any alternative theory of gravity. Several alternative theories of gravity predict dispersion in the gravitational wave signal in a frequency-dependent deviation from the speed of light at lower frequencies than accessible from current ground-based detectors. We show how a multi-band observation of gravitational wave signal combining deci-Hertz gravitational wave signal from LGWA (Lunar Gravitational Wave Antenna) with ground-based detectors such as Cosmic Explorer or Einstein Telescope, and also including LISA (Laser Interferometer Space Antenna), we can probe the energy scale associated with effective theory of modified gravity scenarios by combining only $\mathcal{O}(10)$ high signal to noise ratio (SNR) with a precision of approximately $8.6\%$. This precision will further improve with the inclusion of more events as $\sqrt{N}$. In the future, this measurement will shed light on an unexplored domain of fundamental physics and will bring deeper insights into the phenomenon of cosmic acceleration. The operation of the gravitational wave detector in the deci-Hertz frequency band is key to exploring this frontier of fundamental physics.

gr-qc↗

arXiv2025

Phase Space of Binary Black Holes from Gravitational Wave Observations to Unveil its Formation History

Gravitational Wave (GW) sources offer a valuable window to the physical processes that govern the formation of binary compact objects (BCOs). However, deciphering such information from GW data is substantially challenging due to the difficulty in mapping from the space of observation to the space of numerous theoretical models. We introduce the concept of BCO Phase-Space that connects the observable space to the evolution trajectories of the BCO formation channels with cosmic time and apply it to the third GW transient catalog (GWTC-3) that brings new insights into probable astrophysical formation scenarios of nearly $90$ events. Our study reveals that two events, GW190425 and GW230529, show an overlap with a \texttt{BCO Phase Space} trajectory of the same formation channel arising from a sub-solar mass black hole scenario that has grown into a higher mass by accretion, hinting towards the common primordial origin of both these sources. Though the actual formation channel is yet to be confirmed, with the availability of more GW events, the \texttt{BCO Phase Space} can delve into distinguishing features of different formation channels for both astrophysical and primordial origin and opens the possibility of bringing new and deeper insights on the formation and evolution of BCOs across all observable masses over most of the cosmic time.

astro-ph.HE↗

arXiv2025

A White Paper on The Multi-Messenger Science Landscape in India

The multi-messenger science using different observational windows to the Universe such as Gravitational Waves (GWs), Electromagnetic Waves (EMs), Cosmic Rays (CRs), and Neutrinos offer an opportunity to study from the scale of a neutron star to cosmological scales over a large cosmic time. At the smallest scales, we can explore the structure of the neutron star and the different energetics involved in the transition of a pre-merger neutron star to a post-merger neutron star. This will open up a window to study the properties of matter in extreme conditions and a guaranteed discovery space. On the other hand, at the largest cosmological scales, multi-messenger observations allow us to study the long-standing problems in physical cosmology related to the Hubble constant, dark matter, and dark energy by mapping the expansion history of the Universe using GW sources. Moreover, the multi-messenger studies of astrophysical systems such as white dwarfs, neutron stars, and black holes of different masses, all the way up to a high redshift Universe, will bring insightful understanding into the physical processes associated with them that are inaccessible otherwise. This white paper discusses the key cases in the domain of multi-messenger astronomy and the role of observatories in India which can explore uncharted territories and open discovery spaces in different branches of physics ranging from nuclear physics to astrophysics.

astro-ph.HE↗

arXiv2025

Turbulence Induced Non-Gaussian Spectral Distortion in the Microwave Sky from Photon-Axion Conversion in Galaxy Clusters

The conversion of CMB photons to axions (or axion-like particles (ALPs)) can lead to a unique spectral distortion in the temperature and polarization sky which can be explored in upcoming CMB experiments. In this work we have developed a numerical simulation-based technique of photons to ALPs conversion in the galaxy clusters and show for the first time that this physical process can lead to large non-Gaussian signal in the temperature and polarization field, which is impacted by the presence of inhomogeneities and turbulence in the electron density and magnetic field. Our simulation-based technique can simulate the theoretical signal for different scenarios of cluster electron density and magnetic field turbulence and provides testable predictions to discover ALPs from galaxy clusters using spatially non-Gaussian and anisotropic spectral distortion of the microwave sky. We show that the presence of turbulence in the magnetic field and electron density can impact the Gaussian part of the signal captured in terms of the angular power spectra of the signal by more than an order of magnitude. Also, the presence of turbulence in different clusters will lead the temperature and polarization fluctuations around the cluster region to have varying non-Gaussian distribution, with peaks and tails different from the Gaussian statistics of the CMB anisotropy. This new numerical technique has made it possible to calculate also the non-Gaussian signals and can be used in future CMB analysis in synergy with X-ray and radio observations to unveil ALPs coupling with photons in the currently unexplored ranges, for the masses between about $10^{-14}$ eV--$10^{-11}$ eV.

astro-ph.CO↗

arXiv2025

Blinded Mock Data Challenge for Gravitational-Wave Cosmology-I: Assessing the Robustness of Methods Using Binary Black Holes Mass Spectrum

Gravitational Wave (GW) sources are standard sirens that provide an independent way to map the cosmic expansion history by combining with an independent redshift measurement either from an electromagnetic counterpart for a bright siren or using different statistical techniques for dark sirens. In this analysis, we perform the first Blinded Mock Data Challenge (\texttt{Blinded-MDC}) to test the robustness in inferring the value of Hubble constant $H_0$ for a dark siren technique which depends on astrophysical mass distribution of Binary Black Holes (BBHs). We have considered different analysis setups for the \texttt{Blinded-MDC} to test both statistical and systematic uncertainties and demonstrate the capabilities in inferring $H_0$ with detector sensitivity as per the fourth observation run of LIGO-Virgo-KAGRA. We find that when the astrophysical population of BBHs matches with the underlying assumption of the model, a cosmological pipeline can recover the injected parameters using the observed mass distribution. However, when the mock mass distribution of the astrophysical population depends slightly on redshift and one is ignorant about it in analyzing the data, it can cause a systematic discrepancy in the inferred value of $H_0$ by about $1.5σ$, above the statistical fluctuations due to noise and a limited number of events. In the future, elaborate studies will be required to mitigate systematic uncertainties due to unknown astrophysical complexities. This MDC framework sets the road map for inspecting the precision and accuracy of standard siren cosmology and provides the first insight into the robustness of the population-dependent cosmology inference in a blinded analysis setup.

astro-ph.CO↗

arXiv2025

The Gravitational Wave Bias Parameter from Angular Power Spectra: Bridging Between Galaxies and Binary Black Holes

This study presents the modeling of the gravitational wave (GW) bias parameter by bridging a connection between simulated GW sources and galaxies in low redshift galaxy surveys 2MPZ and WISExSCOS (WISC). We study this connection by creating a mock GW catalog, populating galaxy surveys with binary black holes (BBHs) for different scenarios of the GW host-galaxy probability as a function of the galaxy stellar mass. We probe the observable consequences of this connection by exploring the spatial clustering of the GW sources in terms of the GW bias parameter. We consider a phenomenological broken power law model for the host-galaxy probability function, with a potential turnover $M_{K}$ at high stellar mass ($10^{11}$ $M_{\odot}$ in the fiducial model) where the star formation efficiency begins to drop. We vary the parameters of the GW host-galaxy probability function and find that generically the GW bias increases as $M_{K}$ increases (and gets suppressed as $M_{K}$ decreases). The change in the GW bias parameter shows a maximum change of about $30\%$ for different scenarios explored in this work in comparison to the galaxy bias. Future measurements of the GW bias can help constrain $M_{K}$ and the slopes of the host-galaxy probability function and thus offer insights into the underlying astrophysical processes.

astro-ph.GA↗

arXiv2025

$μ$-GLANCE: A Novel Technique to Detect Chromatically and Achromatically Lensed Gravitational Wave Signals

Gravitational microlensing in the wave-optics (WO) regime occurs when the Schwarzschild radius of a lensing object is comparable to or smaller than the wavelength of incoming gravitational waves (GWs), producing chromatic amplitude and phase modulations. In contrary, geometric optics effects happen when wavelength is much smaller than the lensing object leading to frequency independent amplifications and phase shifts. GWs can undergo both effects of lensing due to interactions with objects of different scales. To detect and characterize the wave-optics features from a lensed GW, we have developed a novel method \texttt{$μ$-GLANCE} (Micro-Gravitational Lensing Authenticator using Non-modelled Cross-correlation Exploration). In this technique, we calculate the cross-correlation between the residuals from different detectors. We assign a false alarm rate to each potential WO microlensed candidate from a statistical viewpoint, depending on how many times the noise cross-correlation matches the strength of the residual cross-correlation of the candidate over a certain period of time. We show that for an event with a matched-filtering signal-to-noise ratio (SNR) close to thirty, a residual due to wave-optics lensing with an amplitude about $10\%$ of magnification $μ\approx 3.2$ will start to show deviation from noise distribution at more than $68\%$ Confidence interval with the LIGO-Virgo-KAGRA sensitivity for the fourth observation run. This method provides the first technique to detect geometric optics and wave-optics effects from a WO microlensed GW without assuming any specific lensing model, and its application on the current and future GW data can identify events with both chromatic and achromatic lensed scenarios.

gr-qc↗