arXiv subjects

Sujit K. Dalui

Publications and source records attributed to Sujit K. Dalui.

3 recordsLinked to original sources

arXiv2026

Probing cosmic anisotropy with galaxy clusters and supernovae

Using $Λ$CDM and Padé-(2,1) cosmography, we study directional variations in the Hubble constant, $H_0$, using galaxy cluster and Type Ia Supernovae (from Pantheon Plus) by the hemisphere decomposition method. Since there is a degeneracy between $H_0$ and absolute magnitude $M_B$ for Supernovae, Cepheid host calibration is usually required to constrain $H_0$. Hence, in this work in order to complement the Cepheid host calibration in Supernovae, we also use calibrations based on galaxy cluster scaling relations. We find that there is a $\lesssim 1σ$ difference in $H_0$ variations when using galaxy clusters as calibrators compared to Cepheids highlighting that the variations in $H_0$ are robust across different calibration methods. Across all combinations of models and data sets used, we obtain a consistent deviation $\sim 2σ$ from isotropy. In nearly all cases, we notice that the maximum $ΔH_0$ aligns with the CMB dipole direction.

astro-ph.CO↗

arXiv2026

A test of invariance of halo surface density for FIRE-2 simulations with cold dark matter and self-interacting dark matter

Numerous observations have shown that the dark matter halo surface density, defined as the product of core radius and halo central density of cored dark matter haloes is nearly constant and independent of galaxy mass over a whole slew of galaxy types. Here we calculate the surface density in cold dark matter(CDM) and self-interacting dark matter (SIDM) models including baryons, as well as SIDM without baryons, for dwarf galaxies of masses $\approx 10^{10} M_{\odot}$ using mock catalogs obtained from simulations as part of the Feedback In Realistic Environments project. We find that the dark matter surface density and column density are nearly constant for CDM and SIDM for this mass range. The halo surface density obtained from the Burkert profile fit is consistent with galactic-scale observations within $1σ$. We also computed the empirical scaling relations between the central surface density and maximum velocity using the best-fit dark matter profiles, and found that they agree with observations of Milky Way and M31 dwarfs.

astro-ph.CO↗

arXiv2025

Testing the cosmic distance duality relation using model-independent approach

In this work, we test the cosmic distance duality relation (CDDR) using the arbitrary redshift pivot Padé-(2,1) expansion methodology developed in arXiv:2509.16196. This approach allows us to constrain cosmography parameters and test CDDR at any redshift. Further, it does not rely on data reconstructions or extrapolations of the cosmography parameters to higher redshifts. We employ observational data from the Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation dataset, cosmic chronometers (CC), and Type Ia supernovae from the Pantheon Plus (PP) and Dark Energy Survey Year 5 (DESY5) compilations. We find no significant deviations from the standard CDDR relation in the range $0\lesssim z \lesssim 1$ when considering DESI$+r_d$ dataset in combination with PP$+$CC and DESY5$+$CC datasets. However, on imposing a Gaussian prior on $M_B \in \mathcal{N}(-19.253, 0.027)$ (instead of treating it as a free parameter) in the dataset combination PP$+$CC, we find CDDR violation at a level of $(3-5)σ.$

astro-ph.CO↗