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1	Astronomical History and Heritage	ABS-4
Local Astronomical Wisdom of Maluku Coastal Communities: Between Navigation, Seasons, and RitualsSubmit This Sample Abstract Helmina Kastanya (a)*, Ninawati Syahrul (b), Atisah (c) Pusat Riset Manuskrip, Literatur, dan Tradisi Lisan Badan Riset dan Inovasi Nasional emikastanya[at]gmail.com Abstract Local astronomical knowledge is part of the traditional wisdom system of coastal communities in Maluku. This study aims to reveal and analyze the function of the moon and stars in the lives of coastal communities in Maluku, especially in three main aspects: sea navigation, determining the seasons, and carrying out traditional rituals. This study uses a qualitative approach with ethnographic methods, through in-depth interviews, participatory observation, and documentation of living oral narratives in the form of folklore, as well as the daily practices of fishermen. The results of the study show that the constellations and the position of the moon are used as guidelines in determining the direction of traditional sailing, predicting changes in sea seasons, and as markers of sacred time in carrying out traditional ceremonies and spiritual activities. For example, the appearance of certain stars is considered a sign of the arrival of the fishing season, while the phase of the moon influences the decision of when to go to sea or plant. These findings indicate that local astronomical knowledge is not only functional, but also contains cosmological values that are integrated into the cultural structure of the community. However, modernization and changes in lifestyle have caused a shift in the practice and transmission of this knowledge. Therefore, the preservation of local astronomy as an intangible cultural heritage is important to support the sustainability of local identity and resource management based on traditional wisdom. This study is expected to contribute to strengthening local knowledge in the context of sustainable development and cultural education in coastal areas. Keywords: Local astronomy- Coastal communities- Maluku- Traditional navigation- Traditional knowledge- and Season and the sea Share Link | Plain Format | Corresponding Author (Helmina Kastanya)

2	Astronomical History and Heritage	ABS-10
Unveiling Visvanatha^s Mathematical Innovations in astronomy manuscripts B S Shubha, B S Shylaja Indian Institute Of Astrophysics, Bangalore Abstract Visvanatha is a well-known name in north India, who wrote many commentaries on different astronomy texts during 16th century. His work showcases methods for achieving predictions of astronomy events. His contributions highlight an understanding in several key areas. He accurately accounted for the precession of the equinoxes, which is crucial in celestial calculations. He demonstrated iterative methods, refining approximations through repeated calculations to achieve remarkable accuracy. He emphasized geometrical constructions to visually represent celestial events. This approach was valuable for practical application of his calculations. Beyond many of his theoretical treatises and commentaries, the construction of an astrolabe, proves his commitment to practical observation. This blend of theoretical innovation and practical application marks him as a unique astronomer. Bringing Visvanatha work to light not only enriches our understanding of 16th-century Indian astronomy but also emphasizes the sophisticated scientific heritage that often remains hidden in historical shadows. Keywords: Visvanatha, precession of the equinox, iterative method, geometrical calculations Share Link | Plain Format | Corresponding Author (Shubha BS)

3	Astronomical History and Heritage	ABS-12
The total solar eclipse of 18th August 1868 - the aftermath Shylaja B S Jawaharlal Nehru Planetarium, High Grounds, Bengaluru 560001 India Abstract The total solar eclipses have always been events which were eagerly watched out for a variety of reasons. It is delightful experience for lay persons, a great opportunity for astronomers, creating a sense of awe. The traditional scholars in India well versed with computations of eclipses were stunned at the accuracy achieved on the timings by European scholars in the 19th century. Although no records exist on the discussions, in the context of the eclipse of 18 August, 1868, we get some clues in some contemporary texts in regional languages. Here we elaborate these points which lead to a transformation of the methods computations, the process was not very smooth, though not a turmoil. Keywords: Solar eclipse 1868, Indian astronomy, Computations Share Link | Plain Format | Corresponding Author (Shylaja B S)

4	Astronomical History and Heritage	ABS-14
Possible New Astronomical Alignments in Cetho Temple Analysed from Digital Sky Simulation Kharisma Nabila (a,b*) and Mahirta (a) a) Department of Archaeology, Faculty of Cultural Science, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia. b) Archaeometry Research Centre, National Research and Innovation Agency, Jakarta Selatan 12710, Indonesia *kharismanabila250[at]mail.ugm.ac.id. Abstract Digital sky simulation is designed to overcome the limitations of human observation in reconstructing past celestial events. It enables scholars to open new pathways for interpreting archaeological remains based on astronomical alignments. This study utilizes digital sky simulations, such as SunCalc, MoonCalc, PlanetsCalc, Google Earth Pro, and Stellarium, to simulate the positions of celestial objects based on the landscape and the time at which the Cetho Temples were built ca. 1460 CE. A descriptive-qualitative method was applied to explain the expected research results, and interpretive methods were also applied to strengthen the hypothesis of the alignments. The preliminary findings of this study suggest that the Cetho temple does not align with the surrounding mountains, including Mount Lawu, Merbabu, and Merapi, as observed through Google Earths landscape. Based on findings, it is hypothesized that the Cetho temple was not built with the chthonic concept. The average azimuth of the Cetho Temple is 287.88, and we propose that the orientation of Cetho Temple is aligned with the setting of celestial objects such as the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn. These celestial objects may have a relationship with Hindu mythology and its believed deities. The setting of celestial objects may also be related to Hindu worship ceremonies, which are based on the periodic movements of certain celestial bodies. Furthermore, by applying digital technology, the findings underscore the significance of technology in facilitating the interpretation of ancient Javanese astronomical knowledge. Keywords: Cetho Temple- Celestial Objects- Astronomical Alignments- Interpretation Share Link | Plain Format | Corresponding Author (Kharisma Nabila)

5	Astronomical History and Heritage	ABS-18
The Heritage of Astronomical Manuscripts in Mysore B S Shubha, B S Shylaja and Annapurni Subramaniam Indian Institute Of Astrophysics Bangalore Jawaharlal Nehru planetarium, Bangalore Indian Institute Of Astrophysics, Bangalore Abstract The Mysore region has a rich heritage of astronomical manuscripts, with a significant collection preserved at the Oriental Research Institute (ORI) and numerous private family collections. These texts, are 400 years old palm-leaf manuscripts and some 200 years old paper manuscripts, written in a variety of languages. The archaic scripts are as Tigalari, Modi, and Nandinagari. Some notable examples include: -Laghumansa vyakhya: A comprehensive commentary on an astronomical treatise. -Bhugola nirnayaha: Presents straightforward translations and descriptions of the Earth and its fundamental constituents. -Grahaganita Bhaskara: Contains solved examples of celestial events, specifically calculated for the year 1847. - Pratibhagi tika: Serves as a practical ready reckoner for determining planetary positions. Also, we could identify Vasistha Siddhanta, an astronomical work, previously believed to be lost. Its rediscovery emphasizes the immense academic and historical value of Mysore^s manuscript heritage. Keywords: laghu manasa vykya, Grahaganita Bhaskara, Bhugola nirnaya Share Link | Plain Format | Corresponding Author (Shubha BS)

6	Astronomical History and Heritage	ABS-21
Virtual Reality Application for Simulation of Celestial Bodies Movement in Archaeoastronomy Manuella Ivana Uli Sianipar- Agung Dewandaru- Hakim Luthfi Malasan Institut Teknologi Bandung Abstract Archaeoastronomy explores how ancient structures relate to celestial phenomena, yet tools for visualizing historical skies from specific times and places remain limited. This study introduces a Virtual Reality (VR) sky simulation system developed in Unity for the Meta Quest 2, aimed at recreating past skies with a case focus on Borobudur temple, believed to have astronomical alignments, especially at its eastern gate. Users can enter parameters such as date, time, and location to view the sky from a chosen moment in history. The system calculates celestial positions using precession, nutation, and horizontal coordinate conversion, then renders the scene in real time using GPU instancing and the Unity Job System. Testing demonstrated accurate positioning, stable performance (averaging 71 FPS), and high immersion, with an IPQ score of 6.22 out of 7. A case simulation on March 21 at 07:00 AM showed the Sun at an azimuth of 89.88 degree, closely aligned with Borobudur^s eastern entrance. Keywords: Virtual Reality, sky simulation, archaeoastronomy, Unity, Meta Quest 2, precession, star visualization Share Link | Plain Format | Corresponding Author (Manuella Ivana Uli Sianipar)

7	Astronomical History and Heritage	ABS-27
Good Days and Bad Days Based on Astrological Calculations in the Malay-Minangkabau Palangkahan Manuscript Sastri Sunarti1- M. Yunis2- Ninawati Syahrul3- Atisah4- Harits Fadlly5 Pusat Riset Manuskrip, Literatur, dan Tradisi Lisan, BRIN Fakultas Ilmu Budaya Univeristas Andalas Padang Abstract The tradition of determining auspicious and inauspicious days for activities in Malay-Minangkabau society is well-recognised. This knowledge is known as Palangkahan, the science of calculating days based on astronomical principles (Falak). This knowledge is preserved in ancient manuscripts written in the Malay-Minangkabau Arabic script and still in use in Minangkabau, West Sumatra. This article explains techniques for calculating auspicious days for activities based on astronomical calculations in Minangkabau Palangkahan manuscripts. Data were obtained through a literature review and close reading of the Minangkabau manuscript collection. Through a philological and semiotic analysis of the manuscripts, three time symbols (kutiko) were identified: Kutiko Air and Kutiko Hilang, the latter used to determine when an item is lost or stolen. Palangkahan Lima determines the best time for trade, sailing, catching thieves, and starting wars. Gala Salapan guides matchmaking, marriages, selecting a leader (Batagak Penghulu), trade, determining trading locations, building houses, farming, warfare, sailing, finding lost items, and other activities. Seven star names are used to calculate days: Qamarun/Qamar, Katibun, Dzuhriyun/Zahro, Syamsun/Syam, Marijun/Marikh, and Musytarun/Musyitary. Additionally, paired animal symbols, such as tigers and goats, cats and mice (indicators of bad days), fish and water, and eagles and wood (indicators of good days), are also used. This research indicates that the traditional Malay Minangkabau community^s ethno-astronomical knowledge remains alive and thriving within its community. Keywords: Good Days and Bad Days, The Palangkahan Manuscript, Minangkabau Malay, Ethno-Astronomy Share Link | Plain Format | Corresponding Author (Sastri Sunarti)

8	Astronomical History and Heritage	ABS-48
Reconstruction of the Astronomical Phenomenon Behind the Tale of Lintang Kemukus in the Late Majapahit Era Aidila Fitria Syafa (a*), Mochamad Ikbal Arifyanto (a) a) Astronomy Research Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, Indonesia *dilasyafa02[at]gmail.com Abstract Since ancient times, the Javanese people have regarded lintang kemukus as a sign of significant events related to royal affairs. The story of lintang kemukus and the battle of sacred keris during the final era of Majapahit has long been popular among the Javanese, passed down both orally and in written form through traditional chronicles (babad), such as the Babad Segaluh-Mataram used in this study. The chronicle recounts a battle between the Keris Condongcampur, Keris Sengkelat, and Keris Sabuk Inten. This battle results in the defeated keris, Condongcampur, transforming into lintang kemukus. In modern astronomy, lintang kemukus is interpreted as a comet. This study aims to reconstruct the lintang kemukus event by identifying comets that appeared during the final phase of the Majapahit kingdom (1402-1471). The author utilizes comet data sourced from Cometography Volume 1 by Gary W. Kronk. To determine the relevant time span, a literature review was conducted on the reigns of Majapahit kings, particularly those mentioned in the Babad Segaluh-Mataram. This study selected 6 comet candidates within that time range and analyzed their visibility from Java (specifically Mojokerto) using Halley-Electronic Ephemerides of Comet and Stellarium software. Of the 6 comet candidates, Comet C/1471 Y1 was selected as the primary candidate. This decision was based on the year the comet appeared, which falls within the reign of Kertabhumi (the king featured in the lintang kemukus narrative), as well as the fact that it has the most complete and extensive historical records compared to other candidates. The reconstruction results indicate that Comet C/1471 Y1 was visible from Mojokerto between December 1, 1471, and January 21, 1472, in the early hours of the morning, with the highest magnitude among all the candidates. Keywords: Lintang kemukus- Comet- Majapahit- Orbital element Share Link | Plain Format | Corresponding Author (Aidila Fitria Syafa)

9	Astronomical History and Heritage	ABS-64
The impact of genetic and environmental data on changing SE Asian indigenous astronomical systems Wayne Orchiston University of Science and Technology of China, Hefei, China- and Centre for Astrophysics, University of Southern Queensland, Toowoomba, Australia. Abstract SE Asia as a unique ethnoastronomical field laboratory. We know that cultures evolve through time in response to major sea-level and climatic changes, to changing ecological responses and to the arrival of new human populations. As cultures evolve so too do astronomical systems. In this paper we document some of the major environmental and phylogenetic changes that occurred in island SE Asia over the past 60,000-70,000 years and how these would have led to changes in indigenous astronomical systems. We also note how newly-published data, especially involving mtDNA, can led us to immediately abandon previously held models that underpin our understanding of evolving astronomical systems. Keywords: Changing astronomical Systems- sea level changes, climate changes, phylogenetic changes Share Link | Plain Format | Corresponding Author (Wayne Orchiston)

10	Astronomical History and Heritage	ABS-66
King Narai and seventeenth-century Jesuit astronomy in Siam. 1: Father Antoine Thomas, Siam^s first documented Western astronomer Abstract The first ruler to encourage the adoption of Western culture and technology throughout Siam (present-day Thailand) was King Narai, who also had a passion for astronomy. He showed this by encouraging Jesuit missionaries to settle in Siam. One of these was the Belgian missionary-astronomer Father Antoine Thomas who settled in Ayutthaya and introduced ^Western astronomy^ to Siam. In this poster we provide biographical information about Antoine Thomas, examine the observations that he made in 1681 and 1682 to determine the latitude and longitude of Ayutthaya, and examine recent attempts to pinpoint his observing site in Ayutthaya. Keywords: Please Just Try to Submit This Sample Abstract Share Link | Plain Format | Corresponding Author (Wayne Orchiston)

11	Astronomical History and Heritage	ABS-67
King Narai and seventeenth-century Jesuit astronomy in Siam. 2: The lunar eclipse of 11 December 1685 Abstract In his quest to expose Siam to Western culture and technology King Narai invited a delegation of French missionary-astronomers from Ayutthaya to join him and his court astrologers and observe the 10-11 December 1685 lunar eclipse from near Lop Buri. In this poster we review this eclipse and the Jesuit astronomers who observed it, and we note the seminal role that this eclipse played in the development of scientific astronomy in Siam. Keywords: Please Just Try to Submit This Sample Abstract Share Link | Plain Format | Corresponding Author (Wayne Orchiston)

12	Astronomical History and Heritage	ABS-68
King Narai and seventeenth-century Jesuit astronomy in Siam. 3: The construction of Wat San Paulo Abstract Successful observations of the 10-11 December 1685 lunar eclipse led directly to the decision by King Narai to construct of a large Jesuit complex in Lop Buri that included an astronomical observatory. In this poster we discuss the politics behind this decision and how the design of the multi-storeyed observatory was inspired by the recently-erected Paris Observatory. We also mention the original plan to erect a second Western observatory, this time in Ayutthaya. Keywords: Please Just Try to Submit This Sample Abstract Share Link | Plain Format | Corresponding Author (Wayne Orchiston)

13	Astronomical History and Heritage	ABS-69
King Narai and seventeenth-century Jesuit astronomy in Siam. 4: Other lunar eclipses and the partial solar eclipse of 13 April 1688 Abstract Successful observations of the 10-11 December 1685 lunar eclipse also launched an intensive period of observational activity by two different contingents of French Jesuit missionary-astronomers. In this poster we examine two further lunar eclipses and a partial solar eclipse that were observed by the Jesuits from a number of different sites and how these events led to King Narai^s death and the banning of Western astronomers from Siam. Keywords: Please Just Try to Submit This Sample Abstract Share Link | Plain Format | Corresponding Author (Wayne Orchiston)

14	Astronomical History and Heritage	ABS-72
Sensing Local Development Triggered by Timau National Observatory Rhorom Priyatikanto National Research and Innovation Agency, Indonesia Abstract This study investigates the local development spurred by the Timau National Observatory project over the past decade. The establishment of infrastructure, including kilometers of paved roads and an electrical grid, to support the 3.8-meter optical telescope^s installation has inadvertently catalyzed development in the surrounding area. While a positive outcome, this growth necessitates careful management to preserve the pristine conditions crucial for the observatory^s research. We employ multi-source, multi-temporal remote sensing data to quantify the extent of this infrastructure-induced local development. Various metrics serve as proxies for development, with province-level averages acting as a benchmark for comparison. This research is vital for informing sustainable development strategies that balance community growth with the long-term operational needs of scientific research facilities. Keywords: observatory, remote sensing, regional development Share Link | Plain Format | Corresponding Author (Rhorom Priyatikanto)

15	Galaxies and Cosmology	ABS-9
Influence of Gaia Celestial Reference Frame on VLBI estimated Quasars Positions and Celestial Pole Offset I. Nurul Huda^{1,2*}, J.-C. Liu^1, N. Liu^1, and J. Yao^1 1. School of Astronomy and Space Science, Key Laboratory of Modern Astronomy and Astrophysics (Ministry of Education), Nanjing University, Nanjing, People^s Republic of China 2. Research Center for Computing, National Research and Innovation Agency, Bandung, Indonesia Email: ibnu.nurul.huda[at]nju.edu.cn Abstract Celestial Reference Frame is one of the important aspects on Very Long Baseline Interferometry (VLBI) data analysis. Conventionally, International Celestial Reference Frame (ICRF), which is now ICRF3, have been adopted to define apriori on quasar positions on VLBI data processing. Recently, satellite Gaia has produced their own CRF called Gaia CRF (Gaia-CRF), with Gaia-CRF3 as its new version. This another type of CRF has the same level of accuracy with its radio counterpart and it has also much dense quasars. ICRF3 has a deficiency on the quality of the observed quasars positions, notably in the southern hemisphere, which is due to unequal distribution of the observed VLBI antennas. This is not the case of Gaia-CRF3. In this study, we have adopted Gaia-CRF3 as the reference frame on VLBI data analysis. The results of this kind of configuration to the VLBI products will be presented. Keywords: Celestial Reference Frame, VLBI, Astrometry Share Link | Plain Format | Corresponding Author (Ibnu Nurul Huda)

16	Galaxies and Cosmology	ABS-30
A Parallax Distribution-Based Gaussian Mixture Model for Membership Determination in Open Clusters of Solar Neighborhood Rafli Rizaldi (a*) and Muhamad Irfan Hakim (a,b) a) Astronomy Study Program, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung ^raflirizaldigamer[at]gmail.com b) Bosscha Observatory, Institut Teknologi Bandung Abstract This study presents a machine learning approach for determining membership of newly identified open clusters in the solar neighborhood using Gaia DR3 data. Previous works have employed k-nearest neighbors (kNN) and Gaussian Mixture Models (GMM) to improve cluster membership identification. However, applying this method to poorly studied clusters often leads to difficulties in defining reliable parameter ranges using kNN alone. To address this limitation, we introduce a three-component parallax distribution-based GMM during the initial stage of membership selection. In the initial stage, the kNN algorithm is used to determine the range of astrometric parameters from cluster data downloaded within a small search radius. This step is followed by a three-component GMM applied to the parallax distribution to improve the initial membership selection. Subsequently, a two-component GMM is applied to the one-dimensional distribution of Mahalanobis distance. This process is performed on data obtained with a larger search radius, using the parameter range derived from the previous step to probabilistically identify cluster membership. The method is applied to eight clusters: four well-studied control clusters (NGC 2360, Alessi 1, NGC 2099, and NGC 752) and four poorly studied clusters (OCSN 13, 22, 37, and 56). The proposed method effectively distinguishes cluster members from field stars and yields consistent results with existing literature. Furthermore, the parallax distribution-based GMM reveals nine new cluster candidates, two of which correspond to OCSN 57 and OCSN 61. This method shows promising potential for broader application in the discovery of new clusters using current and future Gaia data releases. Keywords: Open cluster- Machine learning- Clustering- kNN- GMM Share Link | Plain Format | Corresponding Author (Rafli Rizaldi)

17	Galaxies and Cosmology	ABS-38
Correlation between Dust Attenuation and Star Formation Timescales in Nearby Galaxies Rafli Rizaldi (a*), Muhammad Fathir Rizqy Fadli (a), Luvena Yumi Odelia (a), Dian P. Triani (b) a) Astronomy Study Program, Faculty of Mathematics and Natural Sciences, ITB *raflirizaldigamer[at]gmail.com b) Center for Astrophysics, Harvard & Smithsonian Abstract The dust content in galaxies is a key indicator of star formation processes and galactic evolution. In high-redshift galaxies, there^s a strong anti-correlation between dust attenuation \(A_V\) and specific star formation rate \(sSFR\), likely driven by dust from core-collapse supernovae. In contrast, nearby galaxies have had more time for dust to form through other channels, like AGB stars and grain growth. This study will investigate whether the \(A_V-1/sSFR\) relation still holds in the local Universe. Using data from SDSS DR19 for a sample of nearby galaxies \(\left(z < 0.1\right)\), we derive the dust attenuation \(\left(A_V\right)\) from Balmer decrement \(\left(H\alpha/H\beta\right)\). Star formation rates \(\left(SFR\right)\) are estimated from dust-corrected \(H\alpha\) luminosities, while stellar masses \(\left(M_*\right)\) are calculated from galaxy photometry. From these parameters, we calculate the \(sSFR\) \(\left(SFR/M_*\right)\) for each galaxy. This allows us to map the \(A_V-1/sSFR\) relation, and compare it to the expectations based on different dust formation mechanisms. Keywords: Dust attenuation- Specific star formation rate- Balmer decrement Share Link | Plain Format | Corresponding Author (Rafli Rizaldi)

18	Galaxies and Cosmology	ABS-42
Analysis of the Redshift Lens Probability Distribution Method in Constraining Cosmological Parameters Hafiz Indra Arwinata (a*) and Anton Timur Jaelani (b,c,d) a) Astronomy Master Program, FMIPA, Institut Tekologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia *) handranata13[at]gmail.com b) Astronomy Research Group and Bosscha Observatory, FMIPA, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia c) U-CoE AI-VLB, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia d) University Center of Excellence for Space Science, Technology and Innovation, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132, Indonesia Abstract The flat \(\Lambda\)CDM model, as the standard model of cosmology, faces a significant challenge due to the Hubble tension arising from discrepancies between measurements of the early and late universe. Gravitational lensing serves as an effective tool for constraining cosmological parameters due to its independence from the cosmic microwave background (CMB) and the distance ladder. This study investigates the effectiveness of the lens redshift probability distribution method in constraining cosmological parameters. This method assumes a simple and isolated gravitational lens system represented by the singular isothermal sphere (SIS) model. The peak of the lens redshift probability depends on the velocity dispersion function (VDF) of the galaxy, the cosmological model, and the cosmological parameters. We constrain the cosmological parameters of the specific cosmological model by adopting VDF values from references and employing a sample of galaxy-scale gravitational lenses. Variations in VDF values do not affect the constraints of cosmological parameters. However, the constraints are significantly influenced by the distribution of the Einstein radius within the data. This distribution should reflect the actual distribution of gravitational lensing systems in the universe. Using this method, future improvements in the quality and quantity of gravitational lens data are expected to tighten the constraints on cosmological parameters. Keywords: gravitational lensing, cosmological parameters, lens redshift probability Share Link | Plain Format | Corresponding Author (Hafiz Indra Arwinata)

19	Galaxies and Cosmology	ABS-45
Constructing the Potential of a Noncanonical Scalar Field for Dark Energy and Analyzing Its Effects on Cosmic Inhomogeneity Abu Ala An-Nadwi (a*), Fargiza Abdan Malikul Mulki (bcd), Muchammad Najmi Syarif Al Baihaqi (a), Hesti Retno Tri Wulandari (bcd) a) Astronomy Study Program, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung, Indonesia *abuannadwi[at]gmail.com b) Astronomy Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung, Indonesia c) Bosscha Observatory, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Peneropongan Bintang No. 45 Lembang, Indonesia d) University Center of Excellence for Space Science, Technology and Innovation, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung, Indonesia Abstract We investigate a cosmological model in which dark energy is represented by a noncanonical scalar field, characterized by a Lagrangian with a nonlinearity index \( n \) in its kinetic term (a.k.a. noncanonical Lagrangian). The potential function is semi-analytically constructed and optimized under the assumption of a constant equation of state to describe the cosmological dynamics for various values of \( n \). Using Type Ia Supernova data, the cosmological parameters \( \Omega_{m,0} \) and \( H_0 \) are constrained to determine the value of \( n \) that fits the observations. The resulting potential exhibits a negative exponential form, indicating a weakening of its strength as the universe evolves. A perturbation analysis is subsequently performed in the conformal Newtonian gauge to investigate the dynamics of cosmic inhomogeneities. Based on this analysis, the structure growth rate \( f(z) \) at \( z \approx 1 \) is found to be approximately 0.74-0.78, which is lower than the corresponding value in the \(\Lambda \)CDM model, estimated at around 0.87-0.88. Furthermore, the model predicts a future loitering phase around \( a \sim 3.2 \), during which the growth of structure slows down due to the interplay between the repulsive nature of the scalar field and the gravitational attraction of matter. Keywords: Dark energy- Noncanonical scalar field- Potential construction Share Link | Plain Format | Corresponding Author (Abu Ala An-Nadwi)

20	Galaxies and Cosmology	ABS-47
Galaxy Cruise Season 2: Expanding Citizen Science-Based Galaxy Morphology Catalogs in the Local Universe Itsna K Fitriana, M Tanaka NAOJ/ITB Abstract We present preliminary results from Galaxy Cruise Season 2, a citizen science project designed to classify galaxy morphologies using deep optical imaging from the Subaru Hyper Suprime-Cam (HSC) survey. Building upon the success of Season 1-which demonstrated the ability of citizen scientists to reliably identify spiral and interacting galaxies-we expand the sample to include fainter galaxies (down to Mr ~ -15) within the same redshift range (z &#8804- 0.2). Season 2 introduces new challenges, particularly due to the increased variability in citizen classification results, as the targets become fainter and more complex. This requires careful correction and calibration to ensure the classifications can be reliably combined with those from Season 1, ultimately contributing to a unified and robust morphology catalog. These preliminary analyses suggest that the resulting catalog will remain robust even for lower-luminosity galaxies and will be highly valuable for studies of galaxy evolution in the local universe. Importantly, the catalog will be made openly available to the astronomical community, enabling broader scientific use. Beyond its scientific potential, Galaxy Cruise serves as an engaging platform that connects the public with astronomical research. It exemplifies a powerful public outreach tool that unites amateur and professional astronomers, fostering deeper public understanding of galaxy structure and evolution. Keywords: citizen science, galaxy morphology, galaxy evolution, public outreach, local universe Share Link | Plain Format | Corresponding Author (Itsna Khoirul Fitriana)

21	Galaxies and Cosmology	ABS-49
Determination of Galaxy Rotation Curves from the HALOGAS and LITTLE THINGS Surveys Using 2D and 3D Techniques Azumah Yasmin (a*), Hesti Wulandari (ab) a) Astronomy Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Bandung, Indonesia *azumahyasmin[at]gmail.com b) Bosscha Observatory, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Lembang, Indonesia Abstract The derivation of galactic rotation curves plays a fundamental role in the study of galactic dynamics, particularly in understanding the mass distribution of various structural components and providing compelling evidence for the presence of dark matter, which dominates at galactic scales. However, obtaining accurate and reliable rotation curves remains challenging due to factors such as determination of inclination angles, beam smearing effects and the presence of non-circular motions caused by unique galactic features, such as bar. The advancement of observational technologies has further supported the development of various methods for rotation curve extraction, each with differing assumptions and computational strategies. In this paper, rotation curves are derived using both two-dimensional (2D) and three-dimensional (3D) methods, with the aim of identifying the most robust method across different galaxy types and observational conditions. The analysis employs the tilted-ring model and harmonic decomposition using the software packages 3DBarolo (applying both the 3DBarolo and 2DBarolo methods) and DiskFit (applying the 2DiskFit method with disk and disk\(+\)bar models). A total of 15 spiral galaxies from the HALOGAS survey and 13 dwarf galaxies from the LITTLE THINGS survey were analyzed, selected to have intermediate inclination angles in the range of \(45^{\circ}<i<75^{\circ}\). Evaluation was carried out through visual inspection of the rotation curves and comparison of galactic parameters such as inclination and position angle (PA). The quality of the derived rotation curves varied, with some exhibiting significant fluctuations. In several cases, the different methods produced consistent results with one another and with the reference data. However, the 3DBarolo method generally yielded smoother and more stable rotation curves, despite its inability to model specific non-axisymmetric features, such as bars. The 2DBarolo method frequently resulted in highly fluctuating curves, while the 2DiskFit disk model showed moderate stability, outperforming 2DBarolo in most cases. Fluctuations were also observed in curves derived using the bar model- however, this model has the added advantage of indicating the possible presence of bar structures in galaxies, although further investigation is required for confirmation. Based on the findings of this study, 3DBarolo is recommended as a more reliable and robust tool for the derivation of galactic rotation curves without bar, and 2DiskFit bar model is recommended for galaxy with bar. Keywords: Spiral galaxies- Dwarf galaxies- Rotation curves Share Link | Plain Format | Corresponding Author (Azumah Yasmin)

22	Galaxies and Cosmology	ABS-52
Dust Attenuation of JWST Massive Star Forming Galaxies at z=5.6: Analysis on Evolution of Dusty Galaxy Environment Elvia Arum(a), Nathaniella Jeanne Suoth(a), Shafa Raissa Salma(a), Sarah Biddle(b), Itsna K Fitriana(c,d) a) Astronomy Study Program ITB b) Center for Astrophysics Harvard c) National Astronomical Observatory of Japan d) Faculty of Mathematics and Natural Sciences ITB Abstract The surface brightness-inclination relation of galaxies at z ~0.7 (around 6 Gyr after the Big Bang) shows a flatter trend compared to local galaxies, implying higher opacity for galaxies in the younger age of the universe (Sargent et al, 2010). With the advent of JWST, further research can be done for galaxies at the early epoch of the universe. By using JWST NIRCam observations with the F277W filter, we analyze the surface brightness-inclination relation of galaxies in their early formation at z ~5.6 when the universe was around 1 Gyr. We select massive star-forming galaxies from the newly published COSMOS-Web catalogue. We expect to constrain the dust geometry in early disks, whether its opacity speaks for an already complex and clumpy environment, or still in primitive, transparent stages. This research will help illuminate the evolution of dust content and geometry in galaxies over cosmic time, improving our general theory of galaxy evolution. Keywords: Galaxy- Dust Attenuation- Galaxy Evolution- Opacity Share Link | Plain Format | Corresponding Author (Nathaniella Jeanne Suoth)

23	Galaxies and Cosmology	ABS-56
Can Supersoft X-ray Sources Power Nebular He&#8239-II Emission? Modeling Predictions and Observational Clues Dian Puspita Triani, Caroline Erickson, Atanas Mitrev, Peixin Zhu, Rosanne Di Stefano Center for Astrophysics Harvard Smithsonian Abstract Nebular He&#8239-II&#8239-&#955-4686 emission remains one of the key diagnostics of hard ionizing radiation in galaxies, yet its origin, particularly in star-forming systems, remains uncertain. Supersoft X-ray sources (SSSs) are theoretically capable of producing He&#8314--ionizing photons but have often been neglected as contributors to He&#8239-II emission. In this talk, I present our recent modeling of SSSs using blackbody spectra and photoionization calculations to assess how the number and luminosity distribution of SSSs affect He&#8239-II ionization. We compare these predictions to observed He&#8239-II/H&#946- ratios in galaxies to evaluate whether SSSs can account for the required ionizing flux. I also highlight two student-led investigations that provide new observational constraints. First, using resolved data from M51, we examine the environments of known SSSs and find that the most luminous SSSs are embedded in dense gas in the central regions, favorable conditions for producing nebular He&#8239-II. Second, a cross-matched analysis of SDSS He&#8239-II emitters and XMM-Newton X-ray sources reveals that He&#8239-II and X-ray luminosities are tightly correlated across both star-forming galaxies and AGN. Interestingly, star-forming galaxies exhibit a higher He&#8239-II-to-X-ray luminosity ratio (LHeII / L&#8339-) and softer X-ray spectra compared to AGN, suggesting that softer, lower-luminosity X-ray sources may be more efficient He&#8239-II producers in these systems. Keywords: Interstellar medium, X-ray, photoionization Share Link | Plain Format | Corresponding Author (Dian Puspita Triani)

24	Galaxies and Cosmology	ABS-60
Star Formation and Quenching in COSMOS Groups: Environmental Trends beyond z~2 Dicky Setiawan(a), Fahmi Aziz Firmansyah(a), Widya Syafna Azhalia(a), Sarah Biddle(b), Itsna K Fitriana(c,d) a) Astronomy Study Program ITB b) Center for Astrophysics Harvard c) National Astronomical Observatory of Japan d) Faculty of Mathematics and Natural Sciences ITB Abstract Galaxy evolution is influenced by both internal processes and external environmental factors. A key question is how environment impacts star formation and quenching, and how this evolves over cosmic time. This study investigates these effects by analyzing the specific star formation rate (sSFR) and quiescent fraction of galaxies as a function of group richness, using the COSMOS-Web galaxy group catalog from Toni et al. (2025), which includes over 1600 galaxy groups up to redshift z ~ 3.7. This allows us to explore environmental effects into the early protocluster formation epoch. We cross-match galaxies in the catalog with photometric and SFR data from COSMOS-Web (Shuntov et al. 2025), apply detection flags to select robust samples, and compute sSFR from stellar mass and SFR estimates. Quiescent galaxies are identified using color-color cuts or an sSFR threshold (sSFR < 10^-11 yr^-1). Galaxies are binned by group richness (based on proxies like lambda* and amplitude A) and redshift intervals to measure average sSFR and quiescent fractions. By comparing trends across redshifts, we aim to identify when environmental quenching becomes effective. These results will be compared to continuous-density trends from Taamoli et al. (2024) to test whether discrete group environments follow similar evolutionary patterns, such as the SFR-density relation reversal at z > 2. This work will help clarify the role of group-scale environments in galaxy quenching across cosmic time. Keywords: Galaxy Quenching- Galaxy Evolution- SFR-Density Relation- Quiscent Fraction Share Link | Plain Format | Corresponding Author (Widya Syafna Azhalia)

25	Galaxies and Cosmology	ABS-61
Determination of Rotation Curves and Study of Galaxy Evolution Based on the KMOS 3D Survey at Redshifts 0.7 < z < 2.7 Va Syarif, Hesti Retno Tri Wulandari Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia Abstract Understanding galaxy evolution is key to unraveling the formation and growth of cosmic structures. This study examines the kinematic evolution of star-forming galaxies using KMOS 3D data across redshifts -0.7 < z < 2.7-. From a final sample of 24 galaxies, rotation curves and gas velocity dispersion profiles were derived using 3D Barolo modeling of H-\alpha- data. Most galaxies exhibit rising then flattening rotation curves, indicating dark matter dominance even at high redshift. The Stellar Mass Tully-Fisher Relation (sTFR) shows no significant evolution in intercept, though galaxies lie below the local relation, suggesting lower past stellar masses at fixed rotation velocity. A strong evolution in intrinsic gas velocity dispersion (-\sigma_{gas}-) is observed, increasing from -\sim-14-24 km/s (-z<1-) to -\sim-40-50 km/s (-z>2-), consistent with disk settling. Dark matter fractions (-f_{DM}-) are higher at -2R_e- than at -R_e-, supporting inside-out growth with weakening radial gradients over time. These results suggest that the basic kinematic structure of massive disk galaxies was already in place by -z \sim 2.3-, with evolution primarily in gas dynamics and stellar mass buildup. Keywords: Please Just Try to Submit This Sample Abstract Share Link | Plain Format | Corresponding Author (Va Syarif)

26	Galaxies and Cosmology	ABS-62
Spatially Resolved Relationship Between Attenuation and Specific Star Formation Rate in MaNGA Raisa Rahma Rizkia, Luki Aldila Ahmad, Cut Dafina Khalisha Institut Teknologi Bandung Abstract Dust in galaxies affects the appearance of active star formation regions by absorbing and scattering starlight which can make the regions appear fainter and redder. This effect, dust attenuation, varies across different parts of the galaxy, leading to misinterpretations of star formation activities. We present the relation of dust attenuation (A_V) and specific star formation rate (sSFR) of star-forming spiral galaxies using spatially resolved measurements from the SDSS-IV MaNGA survey and see how this relationship affects the properties of the galaxies, such as galaxy mass, morphology, and inclination. We use two methods to trace dust attenuation: (1) the Balmer decrement (H&#945-/H&#946-) to measure dust attenuation in gas (A_V,gas), and (2) full-spectrum stellar population fitting to measure the dust attenuation for stellar light (A_V,stars). By analyzing these quantities pixel-by-pixel, we explore how dust attenuation correlates with sSFR. Our hypothesis is that A_V,stars will be lower than A_V,gas due to the existence of two dust components: thick dust in stellar birth clouds and diffuse dust in the ISM. This study is important for the understanding of spatially varying dust attenuation in star formation studies and supports a model where dust geometry changes with both local star-forming conditions and global galaxy properties. Keywords: galaxies: ISM - galaxies: stellar content - galaxies: star formation - galaxies: spiral - ISM: dust - ISM: extinction Share Link | Plain Format | Corresponding Author (Raisa Rahma Rizkia)

27	Galaxies and Cosmology	ABS-65
Modeling the Origins of Galaxy Dust Attenuation Laws Using Simulated Data Abu Ala An-Nadwi (a*), Revaniza Adhistyani (a), Praneeta Bhojwani (a), Dian P. Triani (b) a) Astronomy Study Program, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No. 10 Bandung, Indonesia *abuannadwi[at]gmail.com b) Center for Astrophysics Harvard & Smithshonian, 60 Garden Street, Cambridge, Massachusetts 02138, USA Abstract We investigated the physical origins of galaxy dust attenuation laws by combining a flexible toy attenuation model with predictions from cosmological simulations. Building on the framework of Maheson et al. (2025), we constructed models that vary key parameters--specifically the optical depths of the birth-cloud and ISM dust, \(\tau_1\) and \(\tau_2\), the slope of the attenuation law, \(n_2\), and the fraction of young stars, \(f_{10}\). These parameters allow the model to produce a diverse set of attenuation curves, capturing variations in total attenuation, slope \(\,A_{\mathrm{UV}}/A_V\), and UV bump strength. To connect these models with realistic galaxy populations, we analyzed mock galaxy catalogs from the semi-analytic model Dusty SAGE, which self-consistently tracks the evolution of dust mass, stellar populations, and star formation across cosmic time. The resulting attenuation laws were compared with galaxy properties including dust mass, metallicity, stellar mass, and star formation rate. We find that \(A_V\) is strongly correlated with stellar mass, and shows a tentative correlation with star formation rate (the latter is less robust due to statistical uncertainties). This approach aims to uncover the key drivers of dust attenuation law diversity and to inform improved dust modeling. Keywords: Dust attenuation- Galaxy evolution- Cosmological simulations Share Link | Plain Format | Corresponding Author (Abu Ala An-Nadwi)

28	Galaxies and Cosmology	ABS-75
Machine learning to predict star formation rates and stellar masses from photometric data of galaxies Agharini Linda Ariyani (a*), Mochamad Ikbal Arifyanto (a) Department of Astronomy, Institut Teknologi Bandung, Bandung, West Java, Indonesia *agharini2906[at]gmail.com Abstract Stellar mass (SM) and star formation rate (SFR) are key diagnostics of galaxy evolution, yet their estimation through spectral energy distribution (SED) fitting is computationally demanding and impractical for large surveys. In this study, we evaluate machine learning (ML) methods as efficient alternatives for deriving these properties from photometric data. XGBoost---which showed the best performance among other ML architectures---were trained and tested on photometry data from the GAMA Panchromatic Data Release as features and MAGPHYS-derived properties as targets. We achieved RMSE values of 0.073 dex (SM) and 0.160 dex (SFR). SM predictions were consistently more accurate than SFR, reflecting the greater variability and dust dependence of star formation activity. Compared to traditional SED fitting, the ML models replicate results with competitive accuracy while reducing computation time by several orders of magnitude. These findings highlight the potential of ML to enable fast and scalable galaxy property estimation in upcoming large-scale surveys such as LSST. Keywords: Machine Learning, Galactic Properties, Photometry Share Link | Plain Format | Corresponding Author (Agharini Linda Ariyani)

29	Galaxies and Cosmology	ABS-79
Galaxy Cluster Membership Between z ~ 0.2-0.4 Using KDE Approach with RELICS Data Andi Sitti Mariyam (a*), Premana W. Premadi (b), Anton T. Jaelani (c) a) Department of Astronomy, ITB *email: andisittimariyam[at]gmail.com b) Department of Astronomy, ITB c) Department of Astronomy, ITB Abstract Understanding galaxy evolution within dense environments requires robust methods for identifying cluster membership. This study presents a probabilistic approach to determine galaxy cluster membership in the redshift range z ~ 0.2-0.4 using multiband photometric data from the Reionization Lensing Cluster Survey (RELICS). We implement Kernel Density Estimation (KDE) to identify overdensities in the color-redshift spaces. The results reveal a consistent trend between galaxy color and redshift at density peaks. Keywords: galaxy clusters- membership selection- Kernel Density Estimation Share Link | Plain Format | Corresponding Author (Andi Sitti Mariyam)

30	Galaxies and Cosmology	ABS-87
Unveiling Environmental Quenching in Galaxies at High Redshift Fahmi Aziz Firmansyah (a*), Dicky Setiawan (a), Widya Syafna Azhalia (a) a) Department of Astronomy, Institut Teknologi Bandung Jalan Ganesha 10, Bandung 40132, Indonesia fahmiazizfirmansyah[at]gmail.com Abstract This project addresses a central question in galaxy evolution: how environment affects star formation activity and quenching, and how this evolves over cosmic time. We are investigating this question to understand the relative importance of internal processes and external environmental factors in shaping galaxy properties. We will explore these questions by analyzing the specific star formation rate (sSFR) and quiescent fraction of galaxies as a function of group richness. Our research will utilize the newly released COSMOS-Web deep galaxy group catalog (Toni et al. 2025), which, based on JWST COSMOS-Web imaging, includes over 1600 galaxy groups extending out to \(z\approx3.7\). The analysis will involve measuring sSFRs and identifying quiescent galaxies across a range of group environments, using both group richness \(\lambda_*\) and amplitude (A) as mass proxies. We expect to determine when and how environmental quenching becomes effective by comparing results across redshift bins. We will then compare these trends to the continuous-density results from Taamoli et al. (2024), who studied how sSFR and star formation rate density vary with local overdensity across \(0.4<z<4.\) This comparison will test whether discrete group environments capture the same evolutionary trends observed in continuous density fields-including the potential reversal of the SFR-density relation at \(z>2\). The findings will help clarify whether group-scale environment is a key driver of quenching across cosmic time, providing crucial insights into galaxy evolution in the early universe. Keywords: Galaxy evolution- Star formation quenching- SFR-density relation Share Link | Plain Format | Corresponding Author (Fahmi Aziz Firmansyah)

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