arXiv subjects

Novan Saputra Haryana

Publications and source records attributed to Novan Saputra Haryana.

8 recordsLinked to original sources

arXiv2026

Rest-Frame UV and Optical Structural Evolution of Narrowband-Selected Lyman-alpha Emitters at z = 2-7 with JWST/NIRCam

We present a systematic study of the rest-frame ultraviolet (UV) and optical morphologies of Ly$α$ emitters (LAEs) at $z \simeq 2$-$7$ from the SILVERRUSH multi-narrowband catalog, using JWST/NIRCam imaging from COSMOS-Web. We fit Sérsic profiles in four NIRCam filters (F115W, F150W, F277W, F444W) for LAEs spanning $\sim 2.2$ Gyr of cosmic time. LAE sizes show a mild increase from rest-frame UV to optical wavelengths, with a median optical-to-UV size ratio of $R_{e,\rm opt}/R_{e,\rm UV} = 1.14^{+0.01}_{-0.02}$, indicating a small morphological $K$-correction; this offset is significant at $z \leq 5.7$ but not at $z = 6.6$. The rest-frame optical sizes follow a power-law evolution, given by $R_e \propto (1+z)^{-0.94 \pm 0.09}$, decreasing from $0.91^{+0.07}_{-0.07}$ kpc at $z = 2.2$ to $\sim 0.5$ kpc at $z \gtrsim 5$, in close agreement with a recent JWST study of spectroscopically confirmed LAEs. The rest-frame optical size-mass relation slopes are broadly consistent with those of the general star-forming galaxy (SFG) population, while LAEs lie below it in normalization over $z \sim 3$-$6$. More compact LAEs tend to exhibit higher Ly$α$ equivalent widths, a trend driven mainly by the most compact, marginally resolved sources. These compact systems also occupy elevated SFR surface-density regimes, consistent with a scenario in which concentrated star formation may facilitate Ly$α$ escape. No significant correlation of LAE rest-frame optical size with projected large-scale environment is found over $z \simeq 2$-$7$, suggesting that LAE morphology may be governed primarily by internal galaxy properties, except possibly in the most extreme overdensities.

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arXiv2026

Interplay of Compaction, Quenching, and Black Hole Growth in the Most Massive Galaxies since $z\sim5$: Insights from JWST and Chandra Data

The buildup of dense stellar cores is expected to mark an important transition in the star-formation and black-hole growth of massive galaxies. Using spatially resolved spectral energy distribution (SED) fitting of James Webb Space Telescope near-infrared imaging, combined with stacking analysis of Chandra X-ray data, we trace stellar mass buildup and average black hole accretion in the most massive galaxies at $z<5$, selecting 50 most massive galaxies per redshift bin at constant number density of $\sim4.4\times10^{-5}$ cMpc$^{-3}$. To robustly constrain central stellar populations, we separate active galactic nuclei (AGN) components affecting the photometry using multi-band morphological decomposition and SED analysis. We find that the sample selected with constant number density exhibits evolutionary trend of rapid central compaction at $z\sim4$, during which the median central 1 kpc stellar mass increases by $\sim0.60$ dex over $\sim400$ Myr. The majority of X-ray detected AGN ($63\%\pm12\%$) are hosted by galaxies undergoing the compaction, while we find neither individually detected X-ray sources nor a significant stacked X-ray signal at $z>4$, indicating that substantial average black-hole growth emerges primarily during, rather than before, the compaction. Following the compaction, central specific star formation rates (sSFR) decline by $\sim1.24$ dex over $\sim700$ Myr at $z\sim3$ while remaining elevated galaxy-wide, signaling the onset of inside-out quenching. Despite this central suppression, specific black hole accretion rate remains coupled to the total sSFR. Our results suggest that dense-core formation in the most massive galaxies marks the onset of inside-out quenching and a transition toward enhanced black-hole to stellar growth ratio.

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arXiv2026

GalSyn I: A Forward-Modeling Code for Synthetic Galaxy Observations from Hydrodynamical Simulations and First Data Release from IllustrisTNG

We present GalSyn (Galaxy Synthesizer), a modular and flexible Python package for generating synthetic observations from hydrodynamical galaxy simulations. GalSyn generates synthetic spectrophotometric data cubes for individual galaxies from simulation cutouts, employing a particle-by-particle spectral modeling approach that enables the rapid production of large synthetic datasets required for statistical population studies, offering a computationally efficient alternative to full radiative transfer codes. Users have full control over the spectral modeling choices, including the stellar population synthesis engine, stellar isochrones, spectral libraries, and initial mass functions. Dust attenuation is modeled at spatially resolved scales using a line-of-sight column-density method, with a comprehensive suite of fixed and adaptive attenuation laws. A decoupled kinematics model independently Doppler-shifts the stellar and nebular components, enabling realistic synthetic integral field unit data cubes. It also provides features to add observational realism, including PSF convolution and noise simulation. Beyond generating imaging and spectroscopic data cubes, GalSyn reconstructs spatially resolved physical property maps and star formation histories (SFHs) of a galaxy. Alongside this paper, we present the first data release of synthetic imaging observations and resolved SFHs generated from the IllustrisTNG simulations. This release includes four mock extragalactic survey fields together with data cubes of the individual galaxies within them, data cubes of 290 local massive galaxies and their progenitors tracked across $0<z<5$, and 259 major-merger systems. Each galaxy data cube contains imaging across 47 filters spanning HST, JWST, Euclid, Rubin/LSST, and the Roman Space Telescope. GalSyn is publicly available at https://github.com/aabdurrouf/GalSyn.

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arXiv2026

BEACON: JWST NIRCam Pure-parallel Imaging Survey. III. Constraints on the UV LF and the Clustering of z~7-14 Galaxies

The James Webb Space Telescope (JWST) has extended the frontier of galaxy detection to redshifts z>11, finding a high abundance of UV-bright sources that challenge theoretical models. However, most current results come from just a few fields, introducing uncertainties due to cosmic variance. Here, we constrain z~7-14 UV luminosity functions (LFs) over ~400 sq. arcmin across 36 independent sightlines from DR2 of BEACON, a JWST pure-parallel NIRCam multi-band imaging survey. We identify 164 7 13 do not rule out a possible excess. We measure significant clustering of bright (Muv<-20.5) galaxies at 7<z<10. Fields hosting such sources are approximately three times more likely to be overdense relative to the full survey, implying that UV-bright galaxies preferentially reside in the most massive halos at these redshifts. Comparing with semi-numerical simulations, we estimate that Muv < -20.5 galaxies inhabit halos ~0.8 dex less massive at z~11 than at z~8, consistent with a shift to higher star formation rates. However, their observed clustering exceeds predictions from pre-JWST luminosity-halo mass relations, suggesting these sources reside in more massive halos than previously modelled and/or multiple halo occupation.

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arXiv2026

A Compact Proto-group at $z \sim 5$: A Massive Galaxy Caught in Formation

We report the discovery of SCGG-z5, a compact galaxy proto-group at $z = 4.97$ in the MACS0416 field, identified from the SAPPHIRES Early Data Release. Six members are spectroscopically confirmed via H$α$ emission, spanning $4.96 \leq z_{\rm spec} \leq 4.98$ within a projected diameter of $\sim16$ pkpc. Spectral energy distribution (SED) fitting yields individual stellar masses $8.4 \leq \log(M_*/M_{\odot}) \leq 9.8$, a total group stellar mass of $\log(M_*/M_{\odot}) = 10.07 \pm 0.04$; three of the six members lie above or on the star-forming main sequence at $z \sim 5$, by up to $0.5$ dex. Pixel-by-pixel analysis reveals diverse resolved radial star-formation profiles: three members show declining specific SFR radial profiles and outward-rising stellar age gradients, consistent with inside-out stellar mass growth, while the most massive member shows a tentative inverted sSFR profile suggestive of reduced central star formation. The line-of-sight velocity dispersion over all six members is $σ_v = 375^{+55}_{-195}$ km s$^{-1}$. The projected mass estimator yields $\log(M_{\rm PM}/M_{\odot}) \approx 12.30^{+0.30}_{-0.25}$, consistent with a dark-matter-dominated group halo. EAGLE simulations of structurally similar groups predict full coalescence by $z \sim 3$--$4$, with the merged remnant reaching $\log(M_*/M_{\odot}) > 11$ by $z \sim 1$, consistent with SCGG-z5 representing a rare pre-coalescence phase of early massive galaxy formation, possibly tracing the assembly of a future brightest group or cluster galaxy.

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arXiv2026

BEACON: JWST NIRCam Pure-parallel Imaging Survey. IV. A Systematic Search for Galaxy Overdensities and Evidence for Gas Accretion Mode Transition

We systematically search for galaxy overdensities using 20 independent fields with a minimum of six filters (F090W, F115W, F150W, F277W, F356W, and F444W) from BEACON, the JWST Cycle 2 NIRCam pure-parallel imaging survey. We apply an adaptive kernel-density estimation method that incorporates the full photometric redshift probability distribution function of each galaxy to map galaxy overdensities, and identify 207 significant ($>4\,σ$) overdensities at $1.5 3$, potentially due to a larger cold gas supply in earlier times. Our study reveals a complex interplay between individual galaxies and large-scale environmental properties, marking the onset of environmental effects on galaxy quenching in massive halos at cosmic noon.

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arXiv2026

BEACON: JWST NIRCam Pure-parallel Imaging Survey. II. Physical Properties of $z=7-14$ Galaxies

We present photometric properties of 161 galaxy candidates at $z=7-14$ selected from the second data release (DR2) of BEACON, a JWST Cycle 2 pure-parallel NIRCam imaging program. Carefully selected from 36 independent pointings (corresponding to $\sim350$\,arcmin$^2$ sky coverage), and hence with reduced cosmic variance, our galaxy candidates provide an unbiased sample for investigating galaxy properties over a wide range of environments. We measure the physical properties, including UV continuum slope ($β_{\rm UV}$), stellar mass ($M_*$), star formation rate (SFR), and sizes. Our highest redshift galaxy candidate at $z=13.71\pm0.15$ has a remarkably bright UV luminosity of $M_{\rm UV}=-21.19\pm0.08$, making it the brightest galaxy at $z>12$ if spectroscopically confirmed. With an extremely blue UV slope, compact morphology, and high star formation rate surface density ($Σ_{\rm SFR}$), this candidate may have extremely low metallicity, high ionizing photon escape fraction, or contributions from an AGN. Among our multiple independent sightlines, we identify three fields of galaxy number overdensity with $>3σ$ significance. The properties of galaxies in various environments do not exhibit significant differences, implying either that accelerated galaxy evolution in overdense regions is not yet widespread at $z>7$, or that the current constraints are limited by sample size. Our simulations indicate that increasing the sample by an order of magnitude would allow such environmental trends to be robustly confirmed or ruled out, underscoring the importance of future pure-parallel observations.

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arXiv2025

Stellar Mass Assembly History of Massive Quiescent Galaxies since $z\sim4$: Insights from Spatially Resolved SED Fitting with JWST Data

Massive quiescent galaxies at high redshift show significantly more compact morphology than their local counterparts. To examine their internal structure across a wide redshift range and investigate potential redshift dependence, we performed spatially resolved SED fitting using pixedfit software on massive $(\log(M_*/M_\odot)\sim11)$ quiescent galaxies at $0 4$ kpc), while the central regions ($r \sim 1$ kpc) remain largely unchanged, with stellar mass surface density similar to local quiescent galaxies. The estimated star formation rates are too low to explain the stellar mass growth, indicating an additional stellar mass accumulation process, such as mergers, is necessary. We parameterize the size-mass relation of the most massive galaxies in our sample as $\log(R_{e,mass}) \propto α\log(M_*)$, and find $α= 2.67^{+1.14}_{-1.17}$ for $z\lessapprox2$, consistent with growth dominated by minor mergers, and $α= 0.91^{+0.20}_{-0.16}$ for $z\gtrapprox2$, consistent with growth dominated by major mergers. These results indicate that massive quiescent galaxies originate from compact quenched systems and grow through combinations of minor and major mergers.

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