@phdthesis{Jonic2021,
  author    = {Jonic, Sanja},
  title     = {Constraining black hole growth across cosmic time},
  doi       = {10.25932/publishup-50975},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-509753},
  school      = {Universit{\"a}t Potsdam},
  pages     = {viii, 175},
  year      = {2021},
  abstract  = {Active Galactic Nuclei (AGN) are considered to be the main powering source of active galaxies, where central Super Massive Black Holes (SMBHs), with masses between 106 and 109 M⊙ gravitationally pull the surrounding material via accre- tion. AGN phenomenon expands over a very wide range of luminosities, from the most luminous high-redshift quasars (QSOs), to the local Low-Luminosity AGN (LLAGN), with significantly weaker luminosities. While "typical" luminous AGNs distinguish themselves by their characteristical blue featureless continuum, the Broad Emission Lines (BELs) with Full Widths at Half Maximum (FWHM) in order of few thousands km s1, arising from the so-called Broad Line Region (BLR), and strong radio and/or X-ray emission, detection of LLAGNs on the other hand is quite chal- lenging due to their extremely weak emission lines, and absence of the power-law continuum. In order to fully understand AGN evolution and their duty-cycles across cosmic history, we need a proper knowledge of AGN phenomenon at all luminosi- ties and redshifts, as well as perspectives from different wavelength bands. In this thesis I present a search for AGN signatures in central spectra of 542 local (0.005 < z < 0.03) galaxies from the Calar Alto Legacy Integral Field Area (CALIFA) survey. The adopted aperture of 3′′ × 3′′ corresponds to central ∼ 100 - 500 pc for the redshift range of CALIFA. Using the standard emission-line ratio diagnostic diagrams, we initially classified all CALIFA emission-line galaxies (526) into star- forming, LINER-like, Seyfert 2 and intermediates. We further detected signatures of the broad Hα component in 89 spectra from the sample, of which more than 60\% are present in the central spectra of LINER-like galaxies. These BELs are very weak, with luminosities in range 1038 - 1041 erg s-1, but with FWHMs between 1000 km s-1 and 6000 km s-1, comparable to those of luminous high-z AGN. This result implies that type 1 AGN are in fact quite frequent in the local Universe. We also identified additional 29 Seyfert 2 galaxies using the emission-line ratio diagnostic diagrams. Using the MBH - σ∗ correlation, we estimated black hole masses of 55 type 1 AGN from CALIFA, a sample for which we had estimates of bulge stellar velocity dispersions σ∗. We compared these masses to the ones that we estimated from the virial method and found large discrepancies. We analyzed the validity of both meth- ods for black hole mass estimation of local LLAGN, and concluded that most likely virial scaling relations can no longer be applied as a valid MBH estimator in such low-luminosity regime. These black holes accrete at very low rate, having Edding- ton ratios in range 4.1 × 10-5 - 2.4 × 10-3. Detection of BELs with such low lumi- nosities and at such low Eddington rates implies that these LLAGN are still able to form the BLR, although with probably modified structure of the central engine. In order to obtain full picture of black hole growth across cosmic time, it is es- sential that we study them in different stages of their activity. For that purpose, we estimated the broad AGN Luminosity Function (AGNLF) of our entire type 1 AGN sample using the 1/Vmax method. The shape of AGNLF indicates an apparent flattening below luminosities LHα ∼ 1039 erg s-1. Correspondingly we estimated ac- tive Black Hole Mass Function (BHMF) and Eddington Ration Distribution Function (ERDF) for a sub-sample of type 1 AGN for which we have MBH and λ estimates. The flattening is also present in both BHMF and ERDF, around log(MBH) ∼ 7.7 and log(λ) < 3, respectively. We estimated the fraction of active SMBHs in CALIFA by comparing our active BHMF to the one of the local quiescent SMBHs. The shape of the active fraction which decreases with increasing MBH, as well as the flattening of AGNLF, BHMF and ERDF is consistent with scenario of AGN cosmic downsizing. To complete AGN census in the CALIFA galaxy sample, it is necessary to search for them in various wavelength bands. For the purpose of completing the census we performed cross-correlations between all 542 CALIFA galaxies and multiwavelength surveys, Swift - BAT 105 month catalogue (in hard 15 - 195 keV X-ray band), and NRAO VLA Sky Survey (NVSS, in 1.4 GHz radio domain). This added 1 new AGN candidate in X-ray, and 7 in radio wavelength band to our local LLAGN count. It is possible to detect AGN emission signatures within 10 - 20 kpc outside of the central galactic regions. This may happen when the central AGN has recently switched off and the photoionized material is spread across the galaxy within the light-travel-time, or the photoionized material is blown away from the nucleus by outflows. In order to detect these extended AGN regions we constructed spatially resolved emission-line ratio diagnostic diagrams of all emission-line galaxies from the CALIFA, and found 1 new object that was previously not identified as AGN. Obtaining the complete AGN census in CALIFA, with five different AGN types, showed that LLAGN contribute a significant fraction of 24\% of the emission-line galaxies in the CALIFA sample. This result implies that AGN are quite common in the local Universe, and although being in very low activity stage, they contribute to large fraction of all local SMBHs. Within this thesis we approached the upper limit of AGN fraction in the local Universe and gained some deeper understanding of the LLAGN phenomenon.},
  language  = {en}
}
@phdthesis{Neumann2020,
  author    = {Neumann, Justus},
  title     = {Secular evolution in galaxies},
  doi       = {10.25932/publishup-48270},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-482701},
  school      = {Universit{\"a}t Potsdam},
  pages     = {viii, 97},
  year      = {2020},
  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 ∇σ. 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.},
  language  = {en}
}
@phdthesis{Thater2019,
  author    = {Thater, Sabine},
  title     = {The interplay between supermassive black holes and their host galaxies},
  doi       = {10.25932/publishup-43757},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-437570},
  school      = {Universit{\"a}t Potsdam},
  pages     = {iv, 186},
  year      = {2019},
  abstract  = {Supermassive black holes reside in the hearts of almost all massive galaxies. Their evolutionary path seems to be strongly linked to the evolution of their host galaxies, as implied by several empirical relations between the black hole mass (M BH ) and different host galaxy properties. The physical driver of this co-evolution is, however, still not understood. More mass measurements over homogeneous samples and a detailed understanding of systematic uncertainties are required to fathom the origin of the scaling relations. In this thesis, I present the mass estimations of supermassive black holes in the nuclei of one late-type and thirteen early-type galaxies. Our SMASHING sample extends from the intermediate to the massive galaxy mass regime and was selected to fill in gaps in number of galaxies along the scaling relations. All galaxies were observed at high spatial resolution, making use of the adaptive-optics mode of integral field unit (IFU) instruments on state-of-the-art telescopes (SINFONI, NIFS, MUSE). I extracted the stellar kinematics from these observations and constructed dynamical Jeans and Schwarzschild models to estimate the mass of the central black holes robustly. My new mass estimates increase the number of early-type galaxies with measured black hole masses by 15\%. The seven measured galaxies with nuclear light deficits ('cores') augment the sample of cored galaxies with measured black holes by 40\%. Next to determining massive black hole masses, evaluating the accuracy of black hole masses is crucial for understanding the intrinsic scatter of the black hole- host galaxy scaling relations. I tested various sources of systematic uncertainty on my derived mass estimates. The M BH estimate of the single late-type galaxy of the sample yielded an upper limit, which I could constrain very robustly. I tested the effects of dust, mass-to-light ratio (M/L) variation, and dark matter on my measured M BH . Based on these tests, the typically assumed constant M/L ratio can be an adequate assumption to account for the small amounts of dark matter in the center of that galaxy. I also tested the effect of a variable M/L variation on the M BH measurement on a second galaxy. By considering stellar M/L variations in the dynamical modeling, the measured M BH decreased by 30\%. In the future, this test should be performed on additional galaxies to learn how an as constant assumed M/L flaws the estimated black hole masses. Based on our upper limit mass measurement, I confirm previous suggestions that resolving the predicted BH sphere-of-influence is not a strict condition to measure black hole masses. Instead, it is only a rough guide for the detection of the black hole if high-quality, and high signal-to-noise IFU data are used for the measurement. About half of our sample consists of massive early-type galaxies which show nuclear surface brightness cores and signs of triaxiality. While these types of galaxies are typically modeled with axisymmetric modeling methods, the effects on M BH are not well studied yet. The massive galaxies of our presented galaxy sample are well suited to test the effect of different stellar dynamical models on the measured black hole mass in evidently triaxial galaxies. I have compared spherical Jeans and axisymmetric Schwarzschild models and will add triaxial Schwarzschild models to this comparison in the future. The constructed Jeans and Schwarzschild models mostly disagree with each other and cannot reproduce many of the triaxial features of the galaxies (e.g., nuclear sub-components, prolate rotation). The consequence of the axisymmetric-triaxial assumption on the accuracy of M BH and its impact on the black hole - host galaxy relation needs to be carefully examined in the future. In the sample of galaxies with published M BH , we find measurements based on different dynamical tracers, requiring different observations, assumptions, and methods. Crucially, different tracers do not always give consistent results. I have used two independent tracers (cold molecular gas and stars) to estimate M BH in a regular galaxy of our sample. While the two estimates are consistent within their errors, the stellar-based measurement is twice as high as the gas-based. Similar trends have also been found in the literature. Therefore, a rigorous test of the systematics associated with the different modeling methods is required in the future. I caution to take the effects of different tracers (and methods) into account when discussing the scaling relations. I conclude this thesis by comparing my galaxy sample with the compilation of galaxies with measured black holes from the literature, also adding six SMASHING galaxies, which were published outside of this thesis. None of the SMASHING galaxies deviates significantly from the literature measurements. Their inclusion to the published early-type galaxies causes a change towards a shallower slope for the M BH - effective velocity dispersion relation, which is mainly driven by the massive galaxies of our sample. More unbiased and homogenous measurements are needed in the future to determine the shape of the relation and understand its physical origin.},
  language  = {en}
}
@phdthesis{Herenz2016,
  author    = {Herenz, Edmund Christian},
  title     = {Detecting and understanding extragalactic Lyman α emission using 3D spectroscopy},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-102341},
  school      = {Universit{\"a}t Potsdam},
  pages     = {175},
  year      = {2016},
  abstract  = {In this thesis we use integral-field spectroscopy to detect and understand of Lyman α (Lyα) emission from high-redshift galaxies. Intrinsically the Lyα emission at λ = 1216 {\AA} is the strongest recombination line from galaxies. It arises from the 2p → 1s transition in hydrogen. In star-forming galaxies the line is powered by ionisation of the interstellar gas by hot O- and B- stars. Galaxies with star-formation rates of 1 - 10 Msol/year are expected to have Lyα luminosities of 42 dex - 43 dex (erg/s), corresponding to fluxes ~ -17 dex - -18 dex (erg/s/cm²) at redshifts z~3, where Lyα is easily accessible with ground-based telescopes. However, star-forming galaxies do not show these expected Lyα fluxes. Primarily this is a consequence of the high-absorption cross-section of neutral hydrogen for Lyα photons σ ~ -14 dex (cm²). Therefore, in typical interstellar environments Lyα photons have to undergo a complex radiative transfer. The exact conditions under which Lyα photons can escape a galaxy are poorly understood. Here we present results from three observational projects. In Chapter 2, we show integral field spectroscopic observations of 14 nearby star-forming galaxies in Balmer α radiation (Hα, λ = 6562.8 {\AA}). These observations were obtained with the Potsdam Multi Aperture Spectrophotometer at the Calar-Alto 3.5m Telescope}. Hα directly traces the intrinsic Lyα radiation field. We present Hα velocity fields and velocity dispersion maps spatially registered onto Hubble Space Telescope Lyα and Hα images. From our observations, we conjecture a causal connection between spatially resolved Hα kinematics and Lyα photometry for individual galaxies. Statistically, we find that dispersion-dominated galaxies are more likely to emit Lyα photons than galaxies where ordered gas-motions dominate. This result indicates that turbulence in actively star-forming systems favours an escape of Lyα radiation. Not only massive stars can power Lyα radiation, but also non-thermal emission from an accreting super-massive black hole in the galaxy centre. If a galaxy harbours such an active galactic nucleus, the rate of hydrogen-ionising photons can be more than 1000 times higher than that of a typical star-forming galaxy. This radiation can potentially ionise large regions well outside the main stellar body of galaxies. Therefore, it is expected that the neutral hydrogen from these circum-galactic regions shines fluorescently in Lyα. Circum-galactic gas plays a crucial role in galaxy formation. It may act as a reservoir for fuelling star formation, and it is also subject to feedback processes that expel galactic material. If Lyα emission from this circum-galactic medium (CGM) was detected, these important processes could be studied in-situ around high-z galaxies. In Chapter 3, we show observations of five radio-quiet quasars with PMAS to search for possible extended CGM emission in the Lyα line. However, in four of the five objects, we find no significant traces of this emission. In the fifth object, there is evidence for a weak and spatially quite compact Lyα excess at several kpc outside the nucleus. The faintness of these structures is consistent with the idea that radio-quiet quasars typically reside in dark matter haloes of modest masses. While we were not able to detect Lyα CGM emission, our upper limits provide constraints for the new generation of IFS instruments at 8--10m class telescopes. The Multi Unit Spectroscopic Explorer (MUSE) at ESOs Very Large Telescopeis such an unique instrument. One of the main motivating drivers in its construction was the use as a survey instrument for Lyα emitting galaxies at high-z. Currently, we are conducting such a survey that will cover a total area of ~100 square arcminutes with 1 hour exposures for each 1 square arcminute MUSE pointing. As a first result from this survey we present in Chapter 5 a catalogue of 831 emission-line selected galaxies from a 22.2 square arcminute region in the Chandra Deep Field South. In order to construct the catalogue, we developed and implemented a novel source detection algorithm -- LSDCat -- based on matched filtering for line emission in 3D spectroscopic datasets (Chapter 4). Our catalogue contains 237 Lyα emitting galaxies in the redshift range 3 ≲ z ≲ 6. Only four of those previously had spectroscopic redshifts in the literature. We conclude this thesis with an outlook on the construction of a Lyα luminosity function based on this unique sample (Chapter 6).},
  language  = {en}
}
@phdthesis{Kamann2013,
  author    = {Kamann, Sebastian},
  title     = {Crowded field spectroscopy and the search for intermediate-mass black holes in globular clusters},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-67763},
  school      = {Universit{\"a}t Potsdam},
  year      = {2013},
  abstract  = {Globular clusters are dense and massive star clusters that are an integral part of any major galaxy. Careful studies of their stars, a single cluster may contain several millions of them, have revealed that the ages of many globular clusters are comparable to the age of the Universe. These remarkable ages make them valuable probes for the exploration of structure formation in the early universe or the assembly of our own galaxy, the Milky Way. A topic of current research relates to the question whether globular clusters harbour massive black holes in their centres. These black holes would bridge the gap from stellar mass black holes, that represent the final stage in the evolution of massive stars, to supermassive ones that reside in the centres of galaxies. For this reason, they are referred to as intermediate-mass black holes. The most reliable method to detect and to weigh a black hole is to study the motion of stars inside its sphere of influence. The measurement of Doppler shifts via spectroscopy allows one to carry out such dynamical studies. However, spectroscopic observations in dense stellar fields such as Galactic globular clusters are challenging. As a consequence of diffraction processes in the atmosphere and the finite resolution of a telescope, observed stars have a finite width characterized by the point spread function (PSF), hence they appear blended in crowded stellar fields. Classical spectroscopy does not preserve any spatial information, therefore it is impossible to separate the spectra of blended stars and to measure their velocities. Yet methods have been developed to perform imaging spectroscopy. One of those methods is integral field spectroscopy. In the course of this work, the first systematic study on the potential of integral field spectroscopy in the analysis of dense stellar fields is carried out. To this aim, a method is developed to reconstruct the PSF from the observed data and to use this information to extract the stellar spectra. Based on dedicated simulations, predictions are made on the number of stellar spectra that can be extracted from a given data set and the quality of those spectra. Furthermore, the influence of uncertainties in the recovered PSF on the extracted spectra are quantified. The results clearly show that compared to traditional approaches, this method makes a significantly larger number of stars accessible to a spectroscopic analysis. This systematic study goes hand in hand with the development of a software package to automatize the individual steps of the data analysis. It is applied to data of three Galactic globular clusters, M3, M13, and M92. The data have been observed with the PMAS integral field spectrograph at the Calar Alto observatory with the aim to constrain the presence of intermediate-mass black holes in the centres of the clusters. The application of the new analysis method yields samples of about 80 stars per cluster. These are by far the largest spectroscopic samples that have so far been obtained in the centre of any of the three clusters. In the course of the further analysis, Jeans models are calculated for each cluster that predict the velocity dispersion based on an assumed mass distribution inside the cluster. The comparison to the observed velocities of the stars shows that in none of the three clusters, a massive black hole is required to explain the observed kinematics. Instead, the observations rule out any black hole in M13 with a mass higher than 13000 solar masses at the 99.7\% level. For the other two clusters, this limit is at significantly lower masses, namely 2500 solar masses in M3 and 2000 solar masses in M92. In M92, it is possible to lower this limit even further by a combined analysis of the extracted stars and the unresolved stellar component. This component consists of the numerous stars in the cluster that appear unresolved in the integral field data. The final limit of 1300 solar masses is the lowest limit obtained so far for a massive globular cluster.},
  language  = {en}
}