Konkoly Extragalactic Workshop 2026
Detre Hall
Konkoly Observatory
Our solar system, indeed our own Milky Way galaxy, pales in comparison to the observable Universe's dimensions. Thus, the extragalactic research group at Konkoly Observatory has a wide array of intriguing research topics, astrophysical phenomena, and objects to choose from.
Our primary areas of interest include
- distant stellar explosions, supernovae, tidal catastrophes, gamma-ray bursts, and other transient phenomena (led by J. Vinkó).
- furthermore, we study active galactic nuclei across the entire electromagnetic spectrum and even employ tools from neutrino astronomy (led by S. Frey).
- a more recent addition of to our research lines is cosmology and the study of the large-scale structure of the Universe with novel data from ongoing galaxy surveys, trying to answer the pressing questions about the dark substances in the cosmos (led by A. Kovács).
Motivated by the possibility to collaborate more closely with each other, we decided to organise a workshop where Konkoly’s early-career scientists working on extragalactic topics give a short overview of their research projects. After the successful events in 2024 and 2025, the goal for this third workshop is to again discuss common themes and methods, leading to joint initiatives and creative new lines of research using state-of-the-art data sets.
Join us and present your results, or just sit in and hear some talks!
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Welcome
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Talks
Scientific talks by participants
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1
Intro & comments
A. Kovács, S. Frey, J. Vinkó
Speaker: András Kovács (Konkoly Observatory) -
2
Multimessenger Pathways to Extragalactic Neutrino Sources
Neutrino astronomy with the IceCube detector probes the high-energy Universe through astrophysical neutrinos in the GeV–PeV energy range in a fundamentally different way than photon-based observations. Neutrino telescopes do not record images of the sky; instead, source associations are inferred statistically from reconstructed neutrino events. To date, only three neutrino sources have reached discovery-level statistical significance with IceCube; two of them are active galactic nuclei. In this talk, I will provide a conceptual overview of how neutrino detections are defined, including event reconstruction and the interpretation of statistical significance. Given the present sensitivity of current detectors, progress in identifying extragalactic neutrino sources depends not only on accumulating more data over time or building larger future instruments, but also on incorporating physically motivated multimessenger priors into statistical analyses. I will argue that such multimessenger approaches offer a powerful pathway toward strengthening the association between high-energy cosmic neutrinos and their astrophysical origins.
Speaker: Emma Kun (HUN-REN Konkoly Observatory) -
3
The GALEX Extragalactic Spectral Database
The GALaxy Evolution eXplorer (GALEX) satellite imaged the sky at
ultraviolet wavelengths over 2003-13, making a well-cited catalogue.
It also took wide-field spectra of 125,000 objects over 0.75% of the
sky, which are under-exploited.To make the spectra useful, we present results from a project tocategorize and collect complementary multiband data for approximately
11,000 extragalactic sources in 211 GALEX spectroscopic fields which
overlap the Sloan Digital Sky Survey (SDSS). We will provide a useful
searchable database of GALEX UV spectra (R~100-200) of extragalactic
sources. For all extragalactic sources (known or classified by us)
with GALEX spectra, we have assembled complementary images and
photometry in FUV+NUV from GALEX, in ugriz from the SDSS, in JHK from
the Two Micron All Sky Survey (2MASS) and in W1-W4 from the Wide-field
Infrared Survey Explorer (WISE), and created spectral energy
distributions (SEDs). We have also logged SIMBAD and SDSS object
classification, redshift and angular size information, and provide
some indication of spectral data quality, since it largely varies
across the sample and even across the wavelength range of individual
spectra, owing to the grism observing strategy (Bianchi et al. 2018,
Astrophys. Space Sci., 363, 56).The UV spectral database consists of 1820 quasars, 2274star-forming galaxies, 6327 quiescent spirals and 386 ellipticals.
The mean redshifts for quasars, star-forming galaxies, quiescent
spirals and ellipticals are 0.99, 0.07, 0.35 and 0.05 respectively.
We will show representative spectra, SEDs and color-magnitude
diagrams. The database (Pritchard et al., in preparation) will be made
publicly available from the Mikulski Archive for Space Telescopes
(STScI's MAST) as a High-Level Science Product (HLSP), as well as from
Vizier.Speaker: Gerard Williger (Konkoly Obs / U Louisville) -
4
Implications of the nanoHertz Gravitational-Wave Background for Galactic Feedback and Massive Black Hole Growth
We investigate how pulsar timing array (PTA) measurements of the nanoHertz gravitational-wave background (GWB) can constrain models for the growth history of supermassive black holes (SMBHs) and how active galactic nucleus (AGN) and stellar feedback models can affect GWB predictions. Feedback regulates supermassive black hole (SMBH) growth, altering the black hole mass function (BHMF). Using BHMFs drawn from multiple cosmological simulation suites including IllustrisTNG, MillenniumTNG, Simba, and CAMELS, and combining these with a quasar-based SMBH binary population framework, we predict the resulting GWB amplitude under a range of different stellar and AGN feedback prescriptions. We find that the choice of both stellar and AGN feedback models alters the high-mass end of the BHMF and changes the predicted GWB amplitude by up to a factor of 2 for the fiducial simulations and a factor 10 for extreme feedback variations in CAMELS. Models with inefficient or absent AGN feedback produce abundant SMBHs and yield GWB amplitudes consistent with PTA data, yet fail in producing realistic galaxies. Fiducial models of AGN and stellar feedback suppress SMBH growth too much and under-predict the expected signal, an effect which could possibly be mitigated by more realistic black hole seeding and growth prescriptions. The mismatch between the GWB amplitudes predicted by cosmological simulations and those observed by PTAs suggests that SMBH growth is more efficient or occurs earlier than captured by current models. This demonstrates that PTA measurements provide a powerful new probe of feedback physics and the SMBH population.
Speaker: Dr Eniko Regos (Konkoly) -
5
Little Red Dots - What's behind the name?
A new population of high-redshift sources was discovered by the James Webb Space Telescope, referred to as little red dots (LRDs). These are a mysterious class of objects that appear to be extremely compact in size, show excess ultraviolet emission, have a red optical continuum in the rest-frame, and exhibit broad-line spectral features. Collecting a sample of 919 LRDs from the literature, we found no associated radio counterparts in catalogues of large radio surveys. To uncover possible sub-millijansky-level weak radio emission, we performed mean and median image stacking analyses of empty-field radio image cutouts centred on the LRD positions. As no underlying emission could be recovered down to ~10 uJy levels, the nature of these extremely radio-quiet LRDs is discussed with respect to `regular' active galactic nuclei at high redshifts.
Speaker: Krisztina Perger (Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences)
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1
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10:30
Coffee break
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Talks
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6
Probing the origin of radio emission in Te-REX objects
Milliarcsecond-scale radio observations of active galactic nuclei (AGN) can help us determine the origin of their radio emission. In case of blazars, radio-loud AGN with their jets pointed close to our line of sight, most of the emission comes from the relativistically boosted jet. However, the radio emission of AGN can originate not only from the jets but from the accretion disk corona or even star formation in the host galaxy.
Balmaverde et al. (2020) compiled a list of radio and X-ray emitting sources that are presumed to be good TeV-emitting candidates (Te-REX) to be detected by the upcoming Cherenkov Telescope Array (CTA). Based on whether they show nuclear activity according to their optical spectra, these sources can be divided into two groups: BL Lacs (a subtype of blazars) and Passive Elliptical Galaxies (PEGs). We obtained Very Long Baseline Interferometry (VLBI) observations of 2 PEGs and used archival VLBI measurements of 6 BL Lacs with additional multi-wavelength data to identify the origin of the radio emission.
We showed that radio emission originates from the nuclear activity in all cases. In one source, jet-related emission is the most probable explanation, while in 5 other objects coronal radio emission may be present.Speaker: Janka Kőmíves (Eötvös Loránd Tudományegyetem) -
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Complex radio jet in a distant blazar across two orders of magnitude in size: multi-frequency VLBI imaging of J1429+5406 at z~3
Our understanding of jet kinematics in z ≥ 3 quasars is still rather limited, based on a sample of less than about 50 objects. We present very long baseline interferometric (VLBI) observations of the powerful blazar J1429+5406 at z=3.015, observed at six frequencies (0.4–15 GHz) between 1994 and 2024. While outer jet components at ∼20–40 milliarcsecond (mas) show no apparent motion, three components within 10 mas exhibit significant proper motions (0.039–0.13) mas/yr, including one that is among the fastest-moving jet components at z ≥ 3 known to date. The core brightness temperature well exceeds the equipartition limit, indicating Doppler boosting. Based on the proper motion of the innermost component, we derive a low jet inclination (within ~5 deg), confirming the blazar nature of the source. Recently, we processed the latest high-sensitivity Very Long Baseline Array measurements of this blazar, taken in 2024. At 1.5 GHz, the radio map clearly reveals a complex, extended radio structure around the source, reaching up to ~400 mas. This resembles a precessing jet whose modeling may constrain its geometry in the future. The data, now based on three decades of observations, are consistent with our previous constraints on the physical parameters of the inner jet. The bulk Lorentz factor appears similar to typical values found in low-redshift blazars. This suggests that there is no fundamental difference between jet physics at low and high redshifts.
Speaker: Dávid Koller (Konkoly Observatory, HUN-REN CSFK / Eötvös Loránd University, Budapest) -
8
Advanced morphological analysis of spiral galaxies in the LSST era
The morphological analysis of galaxies provides important insights into the physical processes that shape their formation and evolution. Modern sky surveys, such as the Legacy Survey of Space and Time (LSST) conducted by the Vera C. Rubin Observatory, enable the study of galaxy morphology across large samples, further increasing the need for efficient automated analysis methods.
This presentation discusses ongoing work toward the large-scale morphological analysis of spiral galaxies in survey imaging data. The project aims to develop a scalable Python-based pipeline that integrates multiple techniques for characterizing spiral structure while maintaining robustness across heterogeneous imaging datasets and compatibility with high-volume survey workflows.
Beyond their astrophysical relevance, the extracted morphological features can add value to large galaxy catalogs, supporting efforts to extend compilations (such as GLADE+ and the newer UpGLADE catalog developed in LIGO) toward significantly larger samples.
Preliminary work focuses on implementing core components of the analysis pipeline and testing them on archival galaxy images. The talk outlines the methodological framework, summarizes initial results, and discusses directions for further development in preparation for future large survey datasets.
Speaker: Balázs Pinczel (Eötvös Loránd University) -
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Probing the primordial Universe with large scale structure surveys
We live in the era of big data cosmology, as many large scale structure surveys like DESI, Euclid and LSST are happening this decade. These datasets are mapping the Universe with unprecedented sensitivity and depth, and will allow us to better understand the nature of dark energy. However, they are also useful to trace the physics of the primordial Universe, and in particular, we can determine the nature of cosmic inflation by measuring the primordial non-Gaussianity parameter, as it has an imprint on the observed matter distribution. In this talk, I will present two recent studies about primordial non-Gaussianity from DESI Luminous Red Galaxies and Gaia quasars, and will comment about the next steps to improve these measurements with upcoming datasets.
Speaker: Dr Jose Bermejo (Konkoly Observatory) -
10
High-Velocity Features in Type Ia Supernovae—A puzzle still waiting to be solved after 26 years
High-velocity (25-30000 km/s) lines (HVFs) of Ca II were first discovered in the spectrum of SN1994D in 1999, and since then, they have been proven to be ubiquitous. Despite this, their exact origin remains unclear to this day. They appear to form in a higher-velocity layer above the photosphere (10-15000 km/s) and show varying strengths and velocity evolutions from object to object.
We used early-phase optical and near-infrared spectra of 56 Type Ia supernovae, observed over the span of 15 years by the Hobby–Eberly Telescope (McDonald Observatory, Texas) to determine the velocity, strength, and evolution of these features.
After using SYNOW to model the high-velocity features of these spectra, we compare them to Gaussian fits of the lines. We look at how velocity determination from the Gaussian fitting of spectral lines compares to velocities gained from the modelling of spectra. We confirm a connection between the light-curve width and the strength (and velocity) of the HVFs, with slow decliners showing stronger (and faster) high-velocity lines. We also demonstrate how high-velocity (HV) and normal-velocity (NV) Wang subtypes have differently behaving high-velocity features, which leads to interesting possibilities in the discussion of the progenitor systems of Type Ia supernovae.
Speaker: Zsófia Bora -
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Type Ia Supernovae in the Coma Cluster
The Coma galaxy cluster has long been used as a cosmic laboratory. This is no coincidence, as it is one of the closest large galaxy clusters to us after the Virgo cluster. Its distance is large enough for the Hubble flow to dominate, but still close enough to be studied in detail.
In our research, we attempted to determine the Coma galaxy cluster's distance as precisely as possible using Type Ia supernovae that were discovered within it. We used several publicly available photometric data sets from the ZTF, ATLAS and YSE surveys, as well as the SALT3 code for multi-colour light curve fitting, to make the distance measurements. We also used our own photometric measurements from the 60 cm Schmidt and 80 cm RC telescopes at the Piszkéstető Observatory. Using all this data, we were able to measure the distance to the Coma cluster more precisely than before. Furthermore, we were able to determine the cluster's average redshift with high accuracy using SDSS spectroscopic data. We also determined the Hubble constant based on our own results.Speaker: Ágoston Horti-Dávid (HUN-REN Csillagászati és Földtudományi Kutatóközpont Konkoly Thege Miklós Csillagászati Intézet)
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6
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12:30
Lunch
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Talks
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12
Integrated Sachs-Wolfe maps from the Gower Street wCDM simulations
The late-time linear Integrated Sachs-Wolfe (ISW) effect directly probes the dynamics of cosmic acceleration and the nature of dark energy. Detecting these weak, secondary temperature anisotropy signals of the CMB requires accurate theoretical predictions of their amplitude across cosmological models. By extending the pyGenISW package, previously limited to $\Lambda$CDM, we aim to generate full-sky ISW maps for a suite of 791 $w$CDM cosmologies using the Gower Street N-body simulations, thereby enabling ISW analyses across a broader dark-energy parameter space. We make our code and ISW data publicly available. We compute the ISW signals by tracing the time evolution of the gravitational potential across large-volume simulations that span dark energy equation of state parameters from phantom to quintessence, $-1.79 < w < -0.34$. These data are projected onto the sphere using HEALPix to obtain full-sky temperature maps. We validate our pipeline by comparing the measured ISW angular power spectra and ISW-density cross-correlations against linear theory expectations ($2 \leq \ell \leq 200$) computed with benchmarks from the pyCCL library. The agreement is excellent across the multipole range where the ISW contribution is expected to dominate, confirming the reliability of our modelling of gravitational-potential evolution. With additional tests of the ISW signal's strength in density extrema, as well as comparing all models to a reference $\Lambda$CDM cosmology, we found that quintessence-like models ($w > -1$) show higher ISW amplitudes than phantom models ($w < -1$), consistent with enhanced late-time decay of gravitational potentials. The consistency of our $w$CDM ISW maps and their agreement with theory predictions confirm the robustness of our methodology, establishing it as a reliable tool for theoretical and observational ISW-LSS analyses
Speaker: Mina Ghodsi Yengejeh (Konkoly Observatory) -
13
SBI of Cosmological Parameters from Density and ISW Maps
Utilizing a Graph Convolutional Neural Network (GCNN) called DeepSphere as the masked portion of a Masked Auto-regressive Flow (MAF), joint posteriors for Omega-Matter and Sigma-8 can be inferred from density maps and ISW maps derived from the first Gower Street simulation suite.
Speaker: Killian Maxwell (ELTE) -
14
Unidimensional Parameter for Galaxy Locations Across the Universe
The Large-Scale Structure (LSS) of the Universe is organised into clusters of galaxies connected by a network of filaments and underdense cosmic voids, which occupy most of the cosmic volume. This LSS can influence the formation and evolution of galaxies and affect their physical properties. However, there is currently no consensus on how to parametrise a galaxy location with respect to the LSS, and different studies can assign the same galaxy to different structures, reflecting the lack of a widely accepted and standardised criterion. In this context, we have obtained, for each galaxy of the Sloan Digital Sky Survey (SDSS), three predicted probabilities of being located in the different environments: voids, filaments, or clusters. These probabilities, derived from neural-network classifications trained on mock catalogues, provide a continuous description, quantifying the probability to belong to each structure on a scale from 0 to 100%. The aim of this work is to define a continuous unidimensional parameter that characterises the location of each spectroscopic galaxy observed by the SDSS, ranging from 0 to 1, from voids to clusters, respectively. We apply Principal Component Analysis (PCA) to reduce the three-dimensional classification into a unidimensional continuous parameter, called the PLSS parameter.
The values of the PLSS accumulate into three distinct peaks corresponding to the three main LSS environments, leaving some regions of the parameter space undersampled. To address this, we define a second complementary unidimensional parameter that uniformly samples the full range of environments. This parameter simplifies interpretation by providing a direct link between its value and the fraction of galaxies in lower and higher density regions. Both parameters are sensitive to the relative radial location of a galaxy within its host void or cluster and can distinguish between galaxies in more or less densely populated clusters.
By providing a unified and quantitative description of galaxy locations within the cosmic web through dimensionality reduction techniques, this approach facilitates the analysis of galaxy physical properties and offers a clearer and more intuitive interpretation of environmental trends. In particular, it enables a consistent framework to address fundamental questions in galaxy evolution: what are the main drivers of galaxy formation, and how does the environment regulate their evolution?Speaker: Mónica Hernández Sánchez (Universitat de València) -
15
Void dynamics with the kinematic Sunyaev-Zeldovich effect
Details will be here soon...
Speaker: Ágnes Bogdán (Konkoly Observatory) -
16
Investigating dSph galaxies with the Subaru PFS
Investigating dSph galaxies with the Subaru PFS
Speaker: Laszlo Dobos (E) -
17
HI kinematics and star formation – the case of a dwarf galaxy
Dwarf galaxies have low gravitational potential, low metallicity and are vulnerable to effects like shockwaves from supernovae. Star formation is expected to be inefficient in these systems, but that is not the case. I present my kinematical analysis of DDO 43, an isolated irregular dwarf in the Local Universe. I used VLA archival data of the HI content of DDO 43 to describe the local motions in around 150 positions over the galaxy, and to derive the global rotation as well. My presentation will cover the spectra analysis of DDO 43, and a comparative study of HI line properties and UV and IR imaging data. This allowed testing the relation of star formation to diffuse gas kinematics.
Speaker: Enikő Pichler
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12
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15:00
Coffee break
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Talks
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18
Catalogs of voids, clusters and quasars densities from the Gaia data
Understanding the formation and evolution of the cosmic web of galaxies is a fundamental goal of both theoretical and observational cosmology, which use various tracers of the cosmic large-scale structure at an ever wider range of redshifts. We present an advancement in mapping of the cosmic web at high redshifts using observational and synthetic catalogues of quasars, which offer a powerful probe of structure formation and the validity of the concordance cosmological model at the largest scales in the Universe.
Our analysis includes 708 483 quasars at 0.8 < z < 2.2 from the Quaia dataset; this enabled an extended reconstruction of the matter density field using 24,372 deg^2 sky area with a well-understood selection function, thus going beyond the capacity of previous studies. Using the REVOLVER method, we created catalogues of voids and clusters based on the estimation of the local density at quasar positions with Voronoi tessellation. We tested the consistency of Quaia data and 50 realistic mock catalogues, including various parameters of the voids and clusters in characteristic subsets of the data, and also measurements of the density profiles of these cosmic super-structures at R ≈ 100 Mpc/h scales.
We identified 12,820 voids and 41,154 clusters in the distribution of Quaia quasars. We found an ∼5−10% level of agreement between data and the ensemble of the 50 mocks considering void and cluster radii, average inner density, and density profiles at all redshifts. In particular, we tested the role of survey mask proximity effects in void and cluster detection, which, although present in the data, are consistent in simulations and observations. Testing the extremes, the largest voids and clusters reach Reff ≈ 250 Mpc/h and Reff ≈ 150 Mpc/h, respectively, but without evidence for ultra-large cosmic structures exceeding the dimensions of the largest structures in our mock catalogues.
Our data-analysis results highlight the capacity of Quaia quasars to robustly map the high-z cosmic web, further supported by the fully consistent statistical results from 50 mock catalogues. As an important deliverable, we share our density field estimation, void catalogues, and cluster catalogues with the public, which allows various additional cross-correlation probes in the high-z cosmic web.Speaker: Nestor Arsenov (Institute of Astronomy, Sofia; Konkoly Observatory, Budapest) -
19
VLBI Imaging Studies of Dual and Multiple AGN Systems
Dual and multiple active galactic nuclei (AGN) in merger systems play a crucial role in our understanding of supermassive black hole growth and evolution. However, the current scarcity of confirmed samples limits statistical studies. In this talk, I will present an overview of my ongoing research using high-resolution Very Long Baseline Interferometry (VLBI) to characterize and confirm scarce dual-AGN populations, including high-redshift dual quasars, sub-kpc-scale close AGN pairs, and radio-faint candidates. For the complex and rare triple AGN candidates, we have proposed deep VLBI imaging observations, which are expected to reveal their milliarcsecond-scale radio emission properties. Finally, I will briefly highlight our recently completed work on measuring blazar magnetic field properties using archival single-dish and VLBI data.
Speaker: Wancheng Xu (Xinjiang Astronomical Observatory of the Chinese Academy of Sciences; Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences) -
20
Investigation of super-Eddington disks around TDE's
Tidal disruption events (TDEs) occur when a supermassive black hole’s (SMBH) gravitational pull tears a star apart, resulting in a bright burst of electromagnetic radiation. These events provide important information about the environment of SMBHs. When the star is disrupted, some of its material forms an accretion disk around the black hole, emitting radiation as it heats up. However, the actual X-ray radiation of the disk is somehow “reprocessed” into optical bands, a phenomenon which is still unclear; therefore, there are various models for description. According to one of the models, when the fallback rate of the matter exceeds the super-Eddington limit, it creates an optically thick super-Eddington wind, which is responsible for the reprocessing. The exact ratio of the matter leaving with the wind to the amount bound in the disk is not well understood, hence further investigation of the Super Eddington Disk models is necessary.
The main goal of my work is implementing this super-Eddington slim disk model and study the connection between the disk and the wind. This requires solving an ordinary differential equation system in the horizontal direction, as well as the vertical direction, which leads to a nested univariate boundary value problem. Accordingly, I implemented a solving algorithm for these type of problems in C language. This consists of the shooting method for solving the boundary value problem in which the iterations are solved by the Brent's method, and a 4th order Runge-Kutta method was implemented to integrate the differential equations. To validate my code, I solve the Shakura-Sunyaev thin disk model similarly to the Super-Eddington slim disk. This means that I lift most of the analytical assumptions in the equations leading to a nested version of the equations, where the vertical and horizontal solutions depend on each other, analogously to the slim disk model.
The model presented here will be extended to include the wind and convection in the future to describe the Super-Eddington state. This implementation will potentially enables better insights into the connection between the disk and the wind in the context of TDEs.Speaker: Domonkos Szabó -
21
Star formation history of galaxy mergers in IllustrisTNG
Galaxy evolution over time remains unclear, with ongoing debate about how collisions affect star formation and metallicity. The role of the local environment shaped by the large-scale structure of the Universe in galaxy mergers may be significant, yet it has not been thoroughly examined. Using the IllustrisTNG cosmological simulation, we processed the catalogue data and merger tree files of the TNG300-1 run. We calculated the average star formation rate (SFR) and stellar mass of galaxies over the redshift range 0 < z < 15 to trace the cosmic star formation history and galaxy growth. We investigated the environments of galaxy mergers with a focus on local density within the cosmic web, and found that interactions with gas-rich dwarf galaxies can trigger a resurgence in gas supply, highlighting the importance of gas dynamics in sustaining star formation. We compared our results with recent JWST observations and identified differences in the star formation rate density (SFRD) history between simulations and observations, providing new insights into early galaxy formation and evolution. See Koncz et. al. Universe 2025, 11(9), 286.
Speaker: Bendegúz Koncz (Debreceni Egyetem)
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18
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