Periodic Reporting for period 1 - GALYKOS (Galactic ArchaeoLoGy based on K-band and Optical Spectroscopy)
Reporting period: 2023-01-09 to 2025-01-08
GALYKOS - Galactic ArchaeoLoGy based on K-band and Optical Spectroscopy - offers an unprecedented view into the central region of spiral galaxies and aims to dissect and discriminate the different stellar populations herein. Its motivation relies on the fact that the typically adopted model describing the stellar disk of spiral galaxies assumes an exponentially increasing stellar surface density, which was never observationally established. This assumption has serious implications, severely affecting the assessment of other stellar components which co-inhabit galactic centers. An appropriate characterization of the various central stellar populations will additionally discriminate between different formation scenarios for this galaxy type. When complete, this project will provide clear observational evidence for the shape of the inner disk in galaxies like our own Milky Way, consequently shedding light on the formation of spiral galaxies.
I have developed a comprehensive pipeline for the automated analysis of integral field spectroscopy (IFS) data, integrating spectral synthesis, kinematic extraction, and gas-phase diagnostics. Leveraging parallel processing for detailed IFS data analysis, this innovative computational tool enables precise structural studies of spiral galaxies, providing insights into the co-evolution of their stellar and gaseous components. By processing MUSE galaxy observations, the pipeline generates detailed maps of stellar age, metallicity, kinematics, emission-line fluxes, and equivalent widths, facilitating the efficient analysis of substantial galaxy samples. The pipeline will be made publicly available upon the project's completion, though it has already been shared with my PhD student for use in her research. Additionally, I have acquired expertise in advanced computational methods through my work with the Vienna Scientific Cluster (VSC), Austria's leading high-performance computing facility. I am proficient in using DYNAMITE, a computationally intensive tool for orbit-based dynamical modeling, and have extensive experience extracting stellar kinematics using conventional techniques like pPXF, as well as the Bayesian-based BayesLOSVD, which offers greater robustness in kinematic analysis. In addition, I have gained proficiency in using BANG which uses analytical potential-density pairs as galactic components. Combining the results obtained with this pipeline with the ones from dynamical modeling, I am currently focusing on uncovering the true shapes of the structural components of disk galaxies. A key aspect of my research involves developing a new formula to accurately describe the morphology of spiral galaxy disks. Once completed, I intend to publish findings that will clarify how the intrinsic disk structure correlates with key galaxy properties, revisiting earlier studies that overlooked the downbending of inner disks. Although the majority of the work plan has been completed, this final phase of the analysis is expected to be finalized over the next six months, in accordance with the timeline and funding provided by the University of Vienna via the Franziska Seidl Funding Program.
Post-processing of exceptionally high-quality IFS data of NGC 4030 with this pipeline reveals a striking grand design spiral pattern in the velocity dispersion map not previously detected. This pattern spatially correlates with HII regions, suggesting that stars currently being born exhibit lower velocity dispersion as compared to surrounding areas where star formation is less active. The complex shape of the uncovered age-velocity-relation supports the hypothesis that stellar populations initially inherit the velocity dispersion of the progenitor cold molecular gas, which depends on formation time and galactocentric distance, subsequently experiencing kinematic heating by cumulative gravitational interactions during their lifetime. These findings offer a new framework for investigating disk heating mechanisms. In addition, upon completing the analysis, I plan to publish a comprehensive article detailing the primary findings. Preliminary results indicate that the central regions of spiral galaxies exhibit a much greater diversity than previously assumed. My ongoing analysis reveals that the dynamical decomposition of a sample of disk galaxies uncovers multiple stellar components coexisting in these central regions, each contributing uniquely to the overall structure and evolution of the galaxy. A key goal of this study is to cross-correlate results from multiple complementary analyses, including spectral synthesis, emission-line diagnostics, dynamical modeling, and structural decomposition. This integrated approach is expected to unravel the underlying causes of the observed diversity and complexity in these regions. By synthesizing information about the ages, metallicities, kinematics, and spatial distributions of the stellar populations with insights into gas dynamics and potential-density structures, we aim to identify the physical mechanisms driving the assembly and co-evolution of these central components. Such findings will not only refine our understanding of the structural and dynamical properties of spiral galaxies but also challenge existing paradigms about their formation and evolution. This work will provide a more nuanced picture of the interplay between stellar and gas components in shaping the intricate morphology of galactic centers and will offer new constraints for theoretical models of disk galaxy evolution.