The Value of ArtScience: improving the balance in collaboration practices between artists and scientists can impact knowledge production

In a time in which scientific knowledge is in danger of being discredited, we return to the responsibility of art and science. There is widespread optimism that collaborations between artists and scientists can develop solutions to complex problems, co-create new knowledge and contribute to discovery and understanding. However, art-science pairings are often based on similar subject areas alone, and without structured efforts to enable cooperation. For artists and scientists, the path towards meaning-making is not guided by the same principles. The artist is not bound to scientific goals or facts and there is no obligation to produce truth, which makes art-science collaborations unique within inter- and transdisciplinary research. For scientific institutions or organisations, such collaborations are often perceived as ‘art in the service of science’ where outcomes of art-science collaborations are primarily seen as a means to communicate difficult scientific concepts to the public. It is rare that art becomes an acknowledged, integral ingredient in the production of scientific knowledge. This is surprising given the special psychological relationship of humans with art: experiencing art can lead to new ways of understanding and meaning-making — crucial for solving the complex and ‘wicked’ problems we are facing in the world today. Combining insights from the ongoing academic debate and my personal experience as an astrophysicist — and artist — who has actively worked in art-science collaborations for the past 12 years, this paper argues for a deep familiarity of the history and methodology of the other discipline as well as confronting one’s own prejudice and biases towards the other discipline

Integralfield spectroscopy of galaxies

Diese Arbeit beschätigt sich mit den Aktivitäten der Seyfert Galaxien UGC 1935, welche mit LEDA 212995 in Wechselwirkung steht, sowie Mrk 607, welche Teil eines Galaxienpaares ist. Kinematische Studien von Absorptionslinien (z.B. Rupke et al., 2005) zeigen großäumige Gasflüsse in wechselwirkenden Galaxien. Das metallarme Gas der Außenbereiche wird in das Zentrum getrieben, wo das akkretierte Material letztendlich das schwarze Loch des aktiven Kerns füttert. Zusätzlich wird Material der Zentralregion in Strömen nach außen getrieben. Die Kombination dieser Prozesse bewirkt einen Abfall der Metallizitäten im Zentrum und ein negativer radialer Metallizitätsgradient kann gemessen werden. Modelle zeigen Metallizitätsgradienten in engen Galaxienpaaren die flacher verlaufen oder abfallen, verglichen mit isolierten Galaxien. Rupke et al. (2010b) demonstrierte in N-body/SPH numerischen Simulationen von Mergern gleicher Masse, dass eine geringere Häufigkeit an Metallen in Gas auftritt, gemessen im Zeitraum zwischen ersten und zweiten Perizentrum der Bewegung. Der radiale Metallizitätsgradient flacht nach dem ersten Vorbeiflug aufgrund der Vermischung des Gases, ab. Die vorliegende Arbeit portraitiert die Seyfert Galaxie UGC 1935 und untersucht erstmalig Metallizietätsgradienten einer aktiven Galaxie. Die Ergebnisse wurden mit der Sy 2 Galaxie Mrk 607 verglichen, welche, obwohl Teil einer Gruppe, schein- bar noch nicht in Wechselwirkung steht.[OIII]/Hβ Linienverhältnisse wurden als Metallizitätsindikatoren über einen zentralen Bereich von 27′′ × 27′′ der Galaxien gemessen um nach Akkretionshinweisen zu suchen. Dafür wurden hochaufgeöste Daten des VLT Integral Field Units VIMOS, durch ein blaues Grism aufgenommen, verwendet und mit VIPGI, dem VIMOS Interactive Pipeline Graphical In- terface (Scodeggio et al., 2005), reduziert. Signaturen der Flu ̈sse als mögliche Auswirkungen der Wechselwirkung sowie zentrale Ausflüsse wurden in UGC 1935 gefunden, waren allerdings mit vorliegendem Material nicht zu sehen in Mrk 607. Nach einer Einleitung zu aktiven Galaxien im Allgemeinen und Seyfert Galaxien im Speziellen, folgt ein Überblick über die Vorteile der Integralfeld Spektroskopie. Zuletzt wird ein detailliertes Portrait der Galaxie UGC 1935 gezeichnet, welches Signaturen der Akkretion aufzeigt, und mit Mrk 607 verglichen.This work aims to give a closer look into the properties of the Seyfert galaxy UGC 1935 which is in interaction with LEDA 212995, as well as Mrk 607 which is part of a galaxy group. Kinematic studies using absorption lines (e.g. Rupke et al., 2005) show large scale gas flows in interacting galaxies. The metal-poor gas is carried from the outskirts of the galaxy towards the center where the accreted material ultimately fuels the black hole of the active galactic nucleus (AGN). Additionally, material from the central region is torqued out of the system in outflows. The combination of these processes cause the central metallicity to drop and a negative metallicity gradient towards the central regions can be measured. Models show metallicity gradients of close pairs that are significantly shallower or even drop compared to gradients of isolated galaxies. Rupke et al. (2010b) demonstrated in N-body/SPH numerical simulations of equal-mass mergers that an underabundance of metals in gas occurs between first and second pericenter of the merging process. The radial metallicity gradient flattens after first passage due to mixing of the gas. This work portrays the Seyfert galaxy UGC 1935 and introduces the investigation of decreasing metallicity gradients towards the center of an active galaxy, as well as compares the results with the Sy 2 galaxy Mrk 607 which, though part of a group, does not yet seem to be in interaction. [OIII]/Hβ line ratios were measured as metallicity indicators throughout the central 27′′ × 27′′ of the sample galaxies to look for accretion signatures. Here, VLT’s VIMOS Integralfield Unit in high resolution blue grism was used to search for such features. The data was reduced using VIPGI, the Vimos Interactive Pipeline Graphical Interface (Scodeggio et al., 2005). Signatures for inflows as a possible result of the interaction as well as outflows that would enhance the negative slope in the gradient, were found in UGC 1935, however were not detected in Mrk 607 with the present data. After an introduction to active galaxies and Seyfert galaxies in particular, an overview of the advantages of integralfield spectroscopy is given. Finally, a detailed portrait of the galaxy UGC 1935 is given with signatures for accretion listed, and compared to Mrk 607

CLASH-VLT: Is there a dependence in metallicity evolution on galaxy structures?

We investigate the environmental dependence of the mass-metallicty (MZ) relation and it's connection to galaxy stellar structures and morphologies. In our studies, we analyze galaxies in massive clusters at z~0.4 from the CLASH (HST) and CLASH-VLT surveys and measure their gas metallicities, star-formation rates, stellar structures and morphologies. We establish the MZ relation for 90 cluster and 40 field galaxies finding a shift of ~-0.3 dex in comparison to the local trends seen in SDSS for the majority of galaxies with logM<10.5. We do not find significant differences of the distribution of 4 distinct morphological types that we introduce by our classification scheme (smooth, disc-like, peculiar, compact). Some variations between cluster and field galaxies in the MZ relation are visible at the high mass end. However, obvious trends for cluster specific interactions (enhancements or quenching of SFRs) are missing. In particular, galaxies with peculiar stellar structures that hold signs for galaxy interactions, are distributed in a similar way as disc-like galaxies - in SFRs, masses and O/H abundances. We further show that our sample falls around an extrapolation of the star-forming main sequence (the SFR-M* relation) at this redshift, indicating that emission-line selected samples do not have preferentially high star-formation rates (SFRs). However, we find that half of the high mass cluster members (M*>10^10Msun) lie below the main sequence which corresponds to the higher mass objects that reach solar abundances in the MZ diagram.Comment: Proceedings of IAU Symposium 309, Vienna, ed. B.L. Ziegler, F. Combes, H. Dannerbauer, M. Verdug

The probability of identifying the cosmic web environment of galaxies around clusters motivated by the Weave Wide Field Cluster Survey

Upcoming wide-field spectroscopic surveys will observe galaxies in a range of cosmic web environments in and around galaxy clusters. In this paper, we test and quantify how successfully we will be able to identify the environment of individual galaxies in the vicinity of massive galaxy clusters, reaching out to $\sim5R_{200}$ into the clusters' infall region. We focus on the WEAVE Wide Field Cluster Survey (WWFCS), but the methods we develop can be easily generalised to any similar spectroscopic survey. Using numerical simulations of a large sample of massive galaxy clusters from \textsc{TheThreeHundred} project, we produce mock observations that take into account the selection effects and observational constraints imposed by the WWFCS. We then compare the `true' environment of each galaxy derived from the simulations (cluster core, filament, and neither core nor filament, {``NCF''}) with the one derived from the observational data, where only galaxy sky positions and spectroscopic redshifts will be available. We find that, while cluster core galaxy samples can be built with a high level of completeness and moderate contamination, the filament and NCF galaxy samples will be significantly contaminated and incomplete due to projection effects exacerbated by the galaxies' peculiar velocities. We conclude that, in the infall regions surrounding massive galaxy clusters, associating galaxies with the correct cosmic web environment is highly uncertain. However, with large enough spectroscopic samples like the ones the WWFCS will provide (thousands of galaxies per cluster, {out to $5R_{200}$}), and the correct statistical treatment that takes into account the probabilities we provide here, we expect we will be able to extract robust and well-quantified conclusions on the relationship between galaxy properties and their environment.Comment: Accepted for publication in MNRAS (14 pages, 7 figures

A Simulation-driven Deep Learning Approach for Separating Mergers and Star-forming Galaxies: The Formation Histories of Clumpy Galaxies in All of the CANDELS Fields

Being able to distinguish between galaxies that have recently undergone major merger events, or are experiencing intense star formation, is crucial for making progress in our understanding of the formation and evolution of galaxies. As such, we have developed a machine learning framework based on a convolutional neural network (CNN) to separate star forming galaxies from post-mergers using a dataset of 160,000 simulated images from IllustrisTNG100 that resemble observed deep imaging of galaxies with Hubble. We improve upon previous methods of machine learning with imaging by developing a new approach to deal with the complexities of contamination from neighbouring sources in crowded fields and define a quality control limit based on overlapping sources and background flux. Our pipeline successfully separates post-mergers from star forming galaxies in IllustrisTNG $80\%$ of the time, which is an improvement by at least 25\% in comparison to a classification using the asymmetry ($A$) of the galaxy. Compared with measured S\'ersic profiles, we show that star forming galaxies in the CANDELS fields are predominantly disc-dominated systems while post-mergers show distributions of transitioning discs to bulge-dominated galaxies. With these new measurements, we trace the rate of post-mergers among asymmetric galaxies in the universe finding an increase from $20\%$ at $z=0.5$ to $50\%$ at $z=2$. Additionally, we do not find strong evidence that the scattering above the Star Forming Main Sequence (SFMS) can be attributed to major post-mergers. Finally, we use our new approach to update our previous measurements of galaxy merger rates $\mathcal{R} = 0.022 \pm 0.006 \times (1+z)^{2.71\pm0.31}$Comment: Accepted for publication in ApJ. 28 pages, 18 Figures, 2 Tables. Pretrained models available at https://github.com/astroferreira/FERREIRA202

The Three Hundred project: connection between star formation quenching and dynamical evolution in and around simulated galaxy clusters

In this work, we combine the semi-analytic model of galaxy formation and evolution SAG with the $102$ relaxed simulated galaxy clusters from The Three Hundred project, and we study the link between the quenching of star formation (SF) and the physical processes that galaxies experience through their dynamical history in and around clusters. We classify galaxies in four populations based on their orbital history: recent and ancient infallers, and backsplash and neighbouring galaxies. We find that $\sim 85$ per cent of the current population of quenched galaxies located inside the clusters are ancient infallers with low or null content of hot and cold gas. The fraction of quenched ancient infallers increases strongly between the first and second pericentric passage, due to the removal of hot gas by the action of ram-pressure stripping (RPS). The majority of them quenches after the first pericentric passage, but a non-negligible fraction needs a second passage, specially galaxies with $M_\star \leq 10^{10.5} \, {\rm M_\odot}$. Recent infallers represent $\sim 15$ per cent of the quenched galaxies located inside the cluster and, on average, they contain a high proportion of hot and cold gas; moreover, pre-processing effects are the responsible for quenching the recent infallers prior to infall onto the main cluster progenitor. The $\sim 65$ per cent of quenched galaxies located around clusters are backsplash galaxies, for which the combination of RPS acting during a pre-processing stage and inside the cluster is necessary for the suppression of SF in this population.Comment: 23 pages, 13 figures + Supplementary material. Accepted for publication in MNRA

An inventory of galaxies in cosmic filaments feeding galaxy clusters: galaxy groups, backsplash galaxies, and pristine galaxies

Galaxy clusters grow by accreting galaxies from the field and along filaments of the cosmic web. As galaxies are accreted they are affected by their local environment before they enter (pre-processing), and traverse the cluster potential. Observations that aim to constrain pre-processing are challenging to interpret because filaments comprise a heterogeneous range of environments including groups of galaxies embedded within them and backsplash galaxies that contain a record of their previous passage through the cluster. This motivates using modern cosmological simulations to dissect the population of galaxies found in filaments that are feeding clusters, to better understand their history, and aid the interpretation of observations. We use zoom-in simulations from TheThreeHundred project to track halos through time and identify their environment. We establish a benchmark for galaxies in cluster infall regions that supports the reconstruction of the different modes of pre-processing. We find that up to 45% of all galaxies fall into clusters via filaments (closer than 1 −1 Mpc from the filament spine). 12% of these filament galaxies are long-established members of groups and between 30 and 60% of filament galaxies at 200 are backsplash galaxies. This number depends on the cluster's dynamical state and sharply drops with distance. Backsplash galaxies return to clusters after deflecting widely from their entry trajectory, especially in relaxed clusters. They do not have a preferential location with respect to filaments and cannot collapse to form filaments. The remaining pristine galaxies (∼30-60%) are environmentally effected by cosmic filaments alone

The three hundred project: thermodynamical properties, shocks and gas dynamics in simulated galaxy cluster filaments and their surroundings

Using cosmological simulations of galaxy cluster regions from The Three Hundred project we study the nature of gas in filaments feeding massive clusters. By stacking the diffuse material of filaments throughout the cluster sample, we measure average gas properties such as density, temperature, pressure, entropy and Mach number and construct one-dimensional profiles for a sample of larger, radially-oriented filaments to determine their characteristic features as cosmological objects. Despite the similarity in velocity space between the gas and dark matter accretion patterns onto filaments and their central clusters, we confirm some differences, especially concerning the more ordered radial velocity dispersion of dark matter around the cluster and the larger accretion velocity of gas relative to dark matter in filaments. We also study the distribution of shocked gas around filaments and galaxy clusters, showing that the surrounding shocks allow an efficient internal transport of material, suggesting a laminar infall. The stacked temperature profile of filaments is typically colder towards the spine, in line with the cosmological rarefaction of matter. Therefore, filaments are able to isolate their inner regions, maintaining lower gas temperatures and entropy. Finally, we study the evolution of the gas density-temperature phase diagram of our stacked filament, showing that filamentary gas does not behave fully adiabatically through time but it is subject to shocks during its evolution, establishing a characteristic z = 0, entropy-enhanced distribution at intermediate distances from the spine of about 1 - 2 $h^{-1}$ Mpc for a typical galaxy cluster in our sample.Comment: 16 pages, 13 figures. Accepted for publication in MNRA

The Three Hundred Project: Galaxy groups do not survive cluster infall

Abstract Galaxy clusters grow by accreting galaxies as individual objects, or as members of a galaxy group. These groups can strongly impact galaxy evolution, stripping the gas from galaxies, and enhancing the rate of galaxy mergers. However, it is not clear how the dynamics and structure of groups are affected when they interact with a large cluster, or whether all group members necessarily experience the same evolutionary processes. Using data from The Three Hundred project, a suite of 324 hydrodynamical resimulations of large galaxy clusters, we study the properties of 1340 groups passing through a cluster. We find that half of group galaxies become gravitationally unbound from the group by the first pericentre, typically just 0.5–1 Gyr after cluster entry. Most groups quickly mix with the cluster satellite population; only $8{{\ \rm per\ cent}}$ of infalling group haloes later leave the cluster, although for nearly half of these, all of their galaxies have become unbound, tidally disrupted or merged into the central by this stage. The position of galaxies in group-centric phase space is also important – only galaxies near the centre of a group (r ≲ 0.7R200) remain bound once a group is inside a cluster, and slow-moving galaxies in the group centre are likely to be tidally disrupted, or merge with another galaxy. This work will help future observational studies to constrain the environmental histories of group galaxies. For instance, groups observed inside or nearby to clusters have likely approached very recently, meaning that their galaxies will not have experienced a cluster environment before