arXiv subjects

Ibnu Nurul Huda

Publications and source records attributed to Ibnu Nurul Huda.

6 recordsLinked to original sources

arXiv2026

First Trigonometric Parallax Measurements with the KVN and VERA Array (KaVA)

To demonstrate the astrometric capability of the combined Korean VLBI (Very Long Baseline Interferometry) Network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA), we conducted six-epoch VLBI observations of 22-GHz H$_{2}$O masers associated with the star-forming region W3(OH). Two atmospheric calibration methods, (1) GPS and (2) JMA (Japan Meteorological Agency) mesoscale analysis data, and two phase-reference sources were independently applied to the astrometric analysis. Trigonometric parallaxes of W3(OH) were successfully measured with all calibration strategies, including the first successful parallax measurement using JMA calibration. The combined-fit parallax is 0.497$\pm$0.024 mas, corresponding to a distance of 2.01$^{+0.10}_{-0.09}$ kpc. This value is consistent with the previous Very Long Baseline Array (VLBA) result of 0.489$\pm$0.017 mas. KaVA achieved a 55$\%$ higher signal-to-noise ratio in phase-referenced maps than VERA, in good agreement with theoretical expectations. These results suggest that KaVA will enable trigonometric parallax measurements of 22-GHz H$_2$O masers that are difficult to observe with VERA alone because of low flux densities and/or limited $uv$ coverage. A flux variation from 510\,$\pm$\,50 to 3900\,$\pm$\,400 Jy was detected in W3(OH) over a one-year observing campaign and is attributed to two nearby maser features separated by only $\sim$64 AU at 2.01 kpc. The brightest feature showed a decrease in linewidth with increasing peak flux density, consistent with unsaturated maser amplification, whereas no similar trend was found for the other feature, suggesting different responses to the same amplification conditions, possibly owing to differences in saturation state and internal velocity structure.

astro-ph.GA↗

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.

astro-ph.GA↗

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.

astro-ph.GA↗

arXiv2024

Implementation of Allan Standard Deviation Technique in Stability Analysis of 4C31.61 Quasar Position

The International Celestial Reference Frame (ICRF) plays an important role in astronomy and geodesy. The realization of ICRF is based on the position of thousands of quasars observed using the Very-Long Baseline Interferometry (VLBI) technique. Better quality of ICRF is achieved when the position of the quasars is stable. In this study, we aim to analyze the stability of one of the quasars in ICRF called 4C31.61 (2201+315). We performed VLBI data analysis by using Vienna VLBI and Satellite Software (VieVS) to get the position of the quasar. We also used the data of the quasar's position from the Paris Observatory Geodetic VLBI Center. We examined the stability of the quasar position by using the Allan standard deviation technique. We found that the quasar 4C31.61 (2201+315) has a stable position with the dominance of white noise across the majority of time scales.

astro-ph.GA↗

arXiv2023

Studying the Equilibrium Points of the Modified Circular Restricted Three-Body Problem: the Case of Sun-Haumea System

We intend to study a modified version of the planar Circular Restricted Three-Body Problem (CRTBP) by incorporating several perturbing parameters. We consider the bigger primary as an oblate spheroid and emitting radiation while the small primary has an elongated body. We also consider the perturbation from a disk-like structure encompassing this three-body system. First, we develop a mathematical model of this modified CRTBP. We have found there exist five equilibrium points in this modified CRTBP model, where three of them are collinear and the other two are non-collinear. Second, we apply our modified CRTBP model to the Sun-Haumea system by considering several values of each perturbing parameter. Through our numerical investigation, we have discovered that the incorporation of perturbing parameters has resulted in a shift in the equilibrium point positions of the Sun-Haumea system compared to their positions in the classical CRTBP. The stability of equilibrium points is investigated. We have shown that the collinear equilibrium points are unstable and the stability of non-collinear equilibrium points depends on the mass parameter $μ$ of the system. Unlike the classical case, non-collinear equilibrium points have both a maximum and minimum limit of $μ$ for achieving stability. We remark that the stability range of $μ$ in non-collinear equilibrium points depends on the perturbing parameters. In context of the Sun-Haumea system, we have found that the non-collinear equilibrium points are stable.

astro-ph.EP↗

arXiv2021

Study of the relation between luni-solar periodicities and earthquake events

We revisit the work of Kilston and Knopoff (1983) to study the correlation of earthquakes with the main lunisolar tidal components in the limited zone of the Southern California region, with a considerably bigger amount of data. By adopting the same methodology as these authors, we confirm their results, i.e. that strong earthquakes with M >= 6 show a statistically significant correlation with half day and precession cycles, with respective periods 12 hr. and 18.6 y., while weaker earthquakes show a correlation with the annual cycle. Moreover we extended the study to the analysis of bi-modal phase to phase diagrams, leading to a very high probability of a lack of earthquake occurrences when both phases of the 12 hr. and 18.6 y. cycles are inside the [0 - 0.5] interval. Furthermore, we demonstrate that the statistical method is not really appropriate to study the correlation with the semi-lunar day and the fortnightly tidal components.

physics.geo-ph↗