Secular Evolution in Galaxies: Properties of Bars and Bulges as seen with Integral Field Spectroscopy Justus Neumann Leibniz-Institut fur¨ Astrophysik Potsdam (AIP) Dissertation zur Erlangung des akademischen Grades “doctor rerum naturalium” (Dr. rer. nat.) in der Wissenschaftsdisziplin Astrophysik eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultat¨ Institut fur¨ Physik und Astronomie der Universitat¨ Potsdam Potsdam, den 18. September 2019 Tag der Disputation: 23. Oktober 2020 Betreuer: Dr. Dimitri Gadotti European Southern Observatory, Garching bei München Prof. Dr. Lutz Wisotzki Leibniz-Institut für Astrophysik Potsdam Prof. Dr. Matthias Steinmetz Leibniz-Institut für Astrophysik Potsdam Gutachter: Prof. Dr. Lutz Wisotzki Leibniz-Institut für Astrophysik Potsdam Dr. Dimitri Gadotti European Southern Observatory, Garching bei München Prof. Dr. Johan Knapen Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain Cover photo: barred spiral galaxy NGC 1300 Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Knezek (WIYN) Published online on the Publication Server of the University of Potsdam: https://doi.org/10.25932/publishup-48270 https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-482701 Abstract Galaxies are gravitationally bound systems of stars, gas, dust and - probably - dark matter. They are the building blocks of the Universe. The morphology of galaxies is diverse: some galaxies have structures such as spirals, bulges, bars, rings, lenses or inner disks, among others. The main processes that characterise galaxy evolution can be separated into fast violent events that dominated evolution at earlier times and slower processes, which constitute a phase called secular evolution, that became dominant at later times. Internal processes of secular evolution include the gradual rearrangement of matter and angular momentum, the build-up and dissolution of substructures or the feeding of supermassive black holes and their feedback. Galaxy bulges – bright central components in disc galaxies –, on one hand, are relics of galaxy formation and evolution. For instance, the presence of a classical bulge suggests a relatively violent history. In contrast, the presence of a disc-like bulge instead indicates the occurrence of secular evolution processes in the main disc. Galaxy bars – elongated central stellar structures –, on the other hand, are the engines of secular evolution. Studying internal properties of both bars and bulges is key to comprehending some of the processes through which secular evolution takes place. The main objectives of this thesis are (1) to improve the classification of bulges by combining photometric and spectroscopic approaches for a large sample of galaxies, (2) to quantify star formation in bars and verify dependencies on galaxy properties and (3) to analyse stellar populations in bars to aid in understanding the formation and evolution of bars. Integral field spectroscopy is fundamental to the work presented in this thesis, which consists of three different projects as part of three different galaxy surveys: the CALIFA survey, the CARS survey and the TIMER project. The first part of this thesis constitutes an investigation of the nature of bulges in disc galaxies. We analyse 45 galaxies from the integral-field spectroscopic survey CALIFA by performing 2D image decompositions, growth curve measurements and spectral template fitting to derive stellar kinematics from CALIFA data cubes. From the obtained results, we present a recipe to classify bulges that combines four different parameters from photometry and kinematics: The bulge Sersic index nb, the concentration index C20;50, the Kormendy relation and the inner slope of the radial velocity dispersion profile rσ. The results of the different approaches are in good agreement and allow a safe classification for approximately 95% of the galaxies. We also find that our new ‘inner’ concentration index performs considerably better than the traditionally used C50;90 and, in combination with the Kormendy relation, provides a very robust indication of the physical nature of the bulge. In the second part, we study star formation within bars using VLT/MUSE observations for 16 nearby (0:01 < z < 0:06) barred active-galactic-nuclei (AGN)-host galaxies from the CARS survey. We derive spatially-resolved star formation rates (SFR) from Hα emission line fluxes and perform a detailed multi-component photometric decomposition on images derived from the data cubes. We find a clear separation into eight star-forming (SF) and eight non-SF bars, which we interpret as indication of a fast quenching process. We further report a correlation between the SFR in the bar and the shape of the bar surface brightness profile: only the flattest bars (nbar < 0:4) are SF. Both parameters are found to be uncorrelated with Hubble type. Additionally, owing to the high spatial resolution of the MUSE data cubes, for the first time, we are able to dissect the SFR within the bar and analyse trends parallel and perpendicular to the bar major axis. Star formation is 1.75 times stronger on the leading edge of a rotating bar than on the trailing edge and is radially decreasing. Moreover, from testing an AGN feeding scenario, we report that the SFR of the bar is uncorrelated with AGN luminosity. Lastly, we present a detailed analysis of star formation histories and chemical enrichment of stellar populations (SP) in galaxy bars. We use MUSE observations of nine very nearby barred galaxies from the TIMER project to derive spatially resolved maps of stellar ages and metallicities, [α/Fe] abundances, star formation histories, as well as Hα as tracer of star formation. Using these maps, we explore in detail variations of SP perpendicular to the bar major axes. We find observational evidence for a separation of SP, supposedly caused by an evolving bar. Specifically, intermediate-age stars (∼ 2-6 Gyr) get trapped on more elongated orbits forming a thinner bar, while old stars (> 8 Gyr) form a rounder and thicker bar. This evidence is further strengthened by very similar results obtained from barred galaxies in the cosmological zoom-in simulations from the Auriga project. In addition, we find imprints of typical star formation patterns in barred galaxies on the youngest populations (< 2 Gyr), which continuously become more dominant from the major axis towards the sides of the bar. The effect is slightly stronger on the leading side. Furthermore, we find that bars are on average more metal-rich and less α-enhanced than the inner parts of the discs that surrounds them. We interpret this result as an indication of a more prolonged or continuous formation of stars that shape the bar as compared to shorter formation episodes in the disc within the bar region. i ii Zusammenfassung Galaxien sind gravitativ gebundene Systeme aus Sternen, Gas, Staub und - wahrscheinlich - dunkler Materie. Sie sind die Bausteine des Universums. Die Morphologie von Galaxien ist vielfaltig:¨ Einige Galaxien haben Strukturen wie zum Beispiel Spirale, Bulges, Balken, Ringe, Linsen oder innere Scheiben. Die Hauptprozesse, die die Entwicklung von Galaxien charakterisieren, konnen¨ unterteilt werden in schnelle, heftige Prozesse, die zu fruheren¨ Zeiten die Evolution beherrschten, und langsamere Prozesse, die eine Phase bilden, die als sakulare¨ Evolution (secular evolution) bezeichnet wird, die zur jetzigen Zeit dominiert. Interne Prozesse der sakularen¨ Evolution sind zum Beispiel die schrittweise Umverteilung von Materie und Drehimpuls, der Auf- und Abbau von Substrukturen oder der Materiezufluss zu supermassereichen Schwarzen Lochern¨ und ihr Feedback. Bulges – helle zentrale Komponenten in Scheibengalaxien –, auf der einen Seite, sind Relikte der Entstehung und Entwicklung von Galaxien. Zum Beispiel, lasst¨ das Vorhandensein eines klassischen Bulges auf eine relativ heftige Entwicklung schließen. Im Gegensatz dazu, weist das Vorhandensein eines scheibenahnlichen¨ Bulges auf das Auftreten von sakularen¨ Evolutionsprozessen in der Hauptscheibe der Galaxie hin. Galaxienbalken (galaxy bars) - langliche¨ zentrale Sternstrukturen - sind dagegen die Motoren der sakularen¨ Evolution. Eine Untersuchung der Eigenschaften von Balken und Bulges ist der Schlussel¨ um die Hauptprozesse der sakularen¨ Evolution zu verstehen. Die Hauptziele dieser Arbeit sind (1) das Verbessern der Klassifikation von Bulges durch Kombination von photometrischen und spektroskopischen Ansatzen¨ fur¨ eine große Anzahl von Galaxien, (2) das Quantifizieren der Sternentstehung in Balken im Verhaltnis¨ zu den Eigenschaften von deren Galaxien und (3) das Analysieren der Sternpopulationen in Balken, um das Verstandnis¨ der Entstehung und Entwicklung von Balken zu erweitern. Integrale Feldspektroskopie (integral field spectroscopy) ist grundlegend fur¨ die vorliegende Arbeit, die aus drei verschiedenen Projekten besteht. Sie wurde im Rahmen von drei verschiedenen Galaxien Surveys – Durchmusterungen von Galaxien – angefertigt: der CALIFA-Survey, der CARS-Survey und das TIMER-Projekt. Der erste Teil dieser Arbeit befasst sich mit der Charakterisierung von Bulgetypen in Scheibengalaxien. Wir analysieren 45 Galaxien vom CALIFA-Survey unter Benutzung von photometrischer und spektroskopischer Methoden um Eigenschaften von Struktur und Kinematik der Bulges zu identifizieren. Basierend auf den Resultaten prasentieren¨ wir ein Rezept zur Klassifizierung von Bulges, das vier verschiedene Parameter aus Photometrie und Kinematik kombiniert: Der Bulge-Sersic-Index,