arXiv subjects

Pralay Biswas

Publications and source records attributed to Pralay Biswas.

5 recordsLinked to original sources

arXiv2026

The Size-Mass Relation and Inside-Out Quenching of Massive Quiescent Galaxies at $2<z<3$ with JWST PRIMER and MINERVA

We investigate the morphology, size--mass relations, and spatially resolved star formation histories of 26 massive quiescent galaxies at cosmic noon ($2 < z < 3$) in the Ultra-Deep Survey field using deep JWST NIRCam imaging from the PRIMER and MINERVA surveys. Combining 16 broadband and medium-band filters with empirical point spread function matching, we perform single-Sérsic modeling and bulge--disk decompositions with pysersic across six filters (F115W to F444W), alongside Bayesian size--mass fitting with dynesty. In the rest-frame optical (F200W), the size--mass relation exhibits a steep slope of $α= 0.59 \pm 0.12$ and effective radius of $A = 0.83_{-0.07}^{+0.08}\ \mathrm{kpc}$ at $M_* = 5 \times 10^{10}\ M_\odot$. In the rest-frame near-infrared (F356W), we derive $α= 0.56 \pm 0.13$ and a more compact radius of $A = 0.70_{-0.06}^{+0.07}\ \mathrm{kpc}$. Galaxy sizes shrink by $\approx 22\%$ from F115W to F444W, reflecting negative color gradients and centrally concentrated mass profiles. Two-thirds of the sample are bulge-dominated ($B/T \ge 0.5$), whereas one-third are disk-dominated. Central bulges are ultra-compact ($R_{e,\mathrm{Bulge}} \approx 0.49\ \mathrm{kpc}$) with negligible mass dependence, whereas outer disks extend to $R_{e,\mathrm{Disk}} \approx 1.4\text{--}1.5\ \mathrm{kpc}$. Resolved spectral energy distribution modeling with piXedfit demonstrates positive radial specific star formation rate gradients and inner regions that formed at least $\approx 0.7\ \mathrm{Gyr}$ earlier and quenched faster than their outskirts. These results confirm inside-out quenching, consistent with dissipative gas compaction assembling the dense core, active galactic nucleus feedback halting central star formation, and the compact bulge dynamically stabilizing the surviving disk against fragmentation.

astro-ph.GA↗

arXiv2026

Morphological and Star Formation Properties of Cosmic Noon Massive Quiescent Galaxies

We analyze the star formation and morphological properties of massive quiescent galaxies at cosmic noon ($2 < z < 3$) in the Abell 2744 field, using deep JWST NIRCam broadband and medium-band imaging from the UNCOVER Treasury program and the MegaScience survey, complemented by archival HST data. Using BAGPIPES SED modeling, we select 14 unique massive quiescent galaxies ($M_* \gtrsim 10^{10}$ M$_\odot$, $\mathrm{sSFR} < 0.2/t_\mathrm{age}$). Morphological analysis with statmorph and pysersic reveals that most galaxies are intermediate type or S0s with a median Sérsic index $n \sim 4$, consistent with bulge-dominated systems. This value remains constant over $z \sim 1.5$--$4$, indicating that the morphology of massive galaxies is linked to their quiescence since at least $z \sim 4$. Spatially resolved SED modeling with piXedfit shows that 11 out of 14 galaxies exhibit positive radial sSFR gradients, providing direct evidence for inside-out quenching, with the mean sSFR increasing by $\sim2$ dex from $R/R_e = 0.5$ to $4.5$. Formation time ($t_{50}$) profiles confirm that inner regions formed $\approx 0.5$ Gyr earlier, on average, than the outer regions, and quenching timescale profiles show that the cores were quenched more rapidly than the outskirts. Most galaxies are compact, with a mean half-mass radius of $R_e = 1.95 \pm 0.13$ kpc. The observed inside-out quenching pattern is consistent with quenching driven by AGN feedback, while the bulge-dominated morphologies suggest morphological quenching may also contribute.

astro-ph.GA↗

arXiv2026

Optically Invisible Galaxies at Cosmic Noon and beyond with JWST/UNCOVER

The traditional selection bias in high-redshift galaxy surveys toward rest-frame ultraviolet emission has constrained our understanding of the high-redshift universe by systematically excluding optically faint (observer-frame) galaxies. Utilising JWST UNCOVER and MegaScience data of the Abell 2744 cluster field, we identify 113 high-redshift ($z > 2$) and 94 low-redshift ($z < 2$) HST-dark galaxies using a red $1.50-3.56 \ μ$m color criterion. Their physical properties were derived using multiwavelength photometry from 20 JWST/NIRCam and 7 HST filters. Unlike classical submillimeter and \textit{Spitzer}-selected HST-dark galaxies that primarily identify the most massive, dusty, highly star-forming galaxies, our study uncovers a moderately dusty population across a significantly broader range of stellar mass and star-formation rate. Leveraging gravitational magnification and ultra-deep JWST imaging, we found HST-dark galaxies with a stellar mass as low as $10^{7.5}$ at $z>2$. These galaxies have smaller sizes and follow the star-forming main sequence. Our analysis reveals a prominent peak in the Star Formation Rate Density at $z \approx 4.5$ ($9.89^{+6.93}_{-4.34} \times 10^{-3} \, M_{\odot} \, \text{yr}^{-1} \, \text{Mpc}^{-3}$). We also characterise a sub-population at $z < 2$ of Highly Extincted Low-Mass analogues with extremely low stellar masses (median $\log M_{\star}/M_{\odot} \approx 7.10$) and high dust extinction (median $A_V \approx 1.97$ mag). Our sample demonstrates the unique power of JWST to reveal this previously missing galaxy population and to provide a more complete census of galaxies in the high-z universe.

astro-ph.GA↗

arXiv2026

uGMRT and MeerKAT observation of RXCJ0232-4420: a quiet cluster with a giant radio halo

Giant radio halos are the Mpc-scale extended sources associated with the merging clusters, while the mini-halos are preferentially associated with cool-core clusters. Both trace the ICM plasma physical process, and recent low-frequency observations increasingly blur the distinction between the two classes. We present the first multi-frequency spectral analysis of the galaxy cluster RXCJ0232--4420, hosting a cool core, using uGMRT (400 and 650 MHz) and MeerKAT (1283 MHz) observations. The central radio emission extends beyond $\sim 1$ Mpc at all frequencies, confirming it as a giant radio halo. One candidate relic (in the east) has also been detected, with an extent of $\sim 300$ kpc. The integrated spectral indices of halo and candidate east relic are $α= -1.17 \pm 0.17$, and $α= -0.85 \pm 0.17$, respectively. The resolved spectral map of the halo is mostly uniform ($-1.0$ to $-1.3$) and does not show any radial steepening. The radio surface brightness profile is well modelled by a single exponential law, with the e-folding radius constant across frequencies. The radio halo emission is morphologically well correlated with the thermal emission. Point-to-point radio-X-ray correlation analysis gives a sublinear relationship (slope $\sim 0.80$), with no frequency evolution. The presence of Mpc-scale emission in the cool-core cluster shows that such emission can arise in dynamically intermediate systems. Our results demonstrate that merger-driven turbulence, even from minor disturbances, can sustain cluster-wide particle re-acceleration without destroying the cool core.

astro-ph.GA↗

arXiv2024

Structure and Kinematics of Star-forming Elliptical Galaxies in SDSS-MaNGA

Using 'spatially' resolved spectroscopy, we investigated the characteristics and different modes of formation of stars in elliptical galaxies. We identified an unusual population of 59 star-forming elliptical (SF-E) galaxies in SDSS-MaNGA, our primary sample. To identify these rare star-forming ellipticals, we combined GSWLC-A2 containing outputs of stellar population synthesis models with morphological results from the deep-learning catalog and resolved and integrated properties from the MaNGA Pipe3D value-added catalog. We have also constructed two control samples of star-forming spirals (SF-Sps; 2419 galaxies) and quenched ellipticals (Q-Es; 684 galaxies) to compare with our primary sample of SF-Es. H$α$ emission line flux of SF-Es is similar to spiral galaxies. The D4000 spectral index indicates that SF-Es have a mixture of old and young stellar populations. Mass-weighted stellar age and metallicity for the SF-Es are lower than the Q-Es and 67\% of stellar- and gas- velocity maps of the primary sample show signs of kinematic disturbance. All of these indicate that SF-Es have acquired metal-poor gas through recent mergers or interactions with other galaxies and are forming a new generation of stars. Further, we subdivide our primary sample of SF-Es into four classes based on their bulge to total luminosity ratio $(B/T)$ and spin parameter $λ_{re}$. These four classes have their distinct evolutionary history and modes of formation. Based on these results, we suggest that the Hubble diagram does not accurately capture galaxy evolution processes, and we need a revised morphology diagram like the comb morphology diagram to get a complete picture of the galaxy evolution processes.

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