Summer Term 2022

Pre-stellar cores are starless cores that are gravitationally bound, dynamically evolved and on the verge of gravitational collapse. They evolve towards a higher central condensation leading to formation of the central protostar. There is observational evidence that the chemistry does not undergo a complete reset with the formation of the protostar, and hence pre-stellar cores provide the budget of matter that will eventually be inherited by stars and planets.
The physics and chemistry of pre-stellar core are deeply interconnected. In my talk I will discuss our recent results on using pre-stellar cores as “space laboratory” to study the physics and chemistry in the early stages of star formation. In particular, I will present our observational and modelling efforts to use molecular spectra to dissect the physical and chemical structure of pre-stellar cores.

Image: Molecular emission maps of the pre-stellar core L1544 from IRAM 30m data. The dotted contours show the H2 column density computed from Herschel/SPIRE data. [Spezzano et al. 2017]

Polycyclic Aromatic Hydrocarbons (PAHs) have been implicated as a large reservoir of reactive carbon in the interstellar medium since the 1980s. PAHs have been widely attributed as the carriers of the unidentified infrared bands where their aggregate vibrational emission spectra are extremely well matched to the observed line signals. Only in the last year have individual PAHs been detected in the ISM for the first time, however, allowing us to begin to investigate the detailed chemical pathways for the formation and destruction of these molecules. In this talk, I will discuss our detections of PAH molecules via their rotational transitions using Green Bank Telescope observations of TMC-1 from the GOTHAM collaboration. I will discuss the efforts to model the chemistry of these PAHs, the necessity of complementary laboratory kinetics work, our application of novel machine learning approaches to exploring the chemical inventory in TMC-1, and finally the benefits of unbiased reaction screening studies in the laboratory with Microwave Spectral Taxonomy.

Molecular ions are at the heart of the formation routes of more complex molecules in the ISM. At the low temperatures and densities prevalent there, only binary reactions with no activation barrier are likely to proceed, and ion-molecule reactions fall generally into this category. Molecular ions are also tracers of the physical conditions of their environment, such as the degree of ionization or the fraction of gas in molecular form.
Although most of the identifications of molecules, including ions, in the ISM have been done using observations in the radiofrequency domain, the observations and laboratory experiments in the infrared region provide very valuable information. On the one hand, IR frequency measurements can provide accurate predictions of rotational transitions to be observed in space or in the laboratory, and, furthermore, ground-based observations in the IR are one of the few available means left to study light hydrides in the ISM.
I will describe the experimental approach followed in our laboratory to study the spectrum of molecular ions, i.e. high resolution tunable infrared laser absorption in hollow cathode electrical discharges, together with some contributions of our lab in this field. I will also comment on ongoing work on the implementation of magnetic fields on the experiment and future prospects.

Career self-management is a central demand in academic career paths, since individuals are frequently held responsible for managing their careers by themselves and face high levels of insecurity in the early career phase. In this talk, I will present results of three longitudinal studies that were part of a larger nine-wave research project on the career paths of young STEM scientists. This research is approached from perspectives of inter-individual as well as intra-individual differences. Questionnaire data were analyzed by using the random intercept cross-lagged panel model (RI-CLPM; Hamaker et al., 2015) to separate between-person effects from within-person effects. The first study examined reciprocal relationships between work-related self-management, occupational self-efficacy, and career insecurity (N = 3118 PhD students and PhD holders). Results showed increases in self-management and self-efficacy to predict decreases in career insecurity as well as increases in career insecurity to predict decreases in self-management and self-efficacy. The second study investigated the dynamic relationship between flow experience and career goal clarity (N = 3094 PhD students and PhD holders). Results revealed increases in career goal clarity to be associated with subsequent increases in flow experience, and vice versa. The purpose of the third study was to illuminate the process of disengagement from the goal to obtain a PhD (N = 2,011 PhD students). It was assumed that both the lack of self-directed career management as well as social support fuel the experience of an action crisis with regard to the goal to complete a PhD, which, in turn, mitigates the motivation to engage in career management and seek out social support. Results confirmed these predictions. Practical implications will be discussed.

Ultraviolet photons emitted by O/B stars have profound effects on the evolution of interstellar matter in our Galaxy and throughout the Universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant radiative feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons (E=5.17-13.6 eV) create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study
in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, protoplanetary disks and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions.
In this talk, I will present some recent efforts aiming at the improving our understanding of PDRs.
I will describe how recent results from laboratory astrophysics providing molecular parameters for Polycyclic Aromatic Hydrocarbons (PAHs) can be used to revisit the role and contribution of these species to the most important heating mechanism in PDRs, i.e. the photoelectric heating. I will then describe the PDRs4All project, which is an Early Release Science (ERS) program involving a large community of scientist from astronomy to laboratory astrophysics, aiming to observe the Orion Bar PDR with the James Webb Space Telescope (JWST) in the summer-fall 2022. Important efforts have been developed by the PDRs4All team, in terms of modelling and data processing methods relying on machine learning, to prepare for the analysis of the spectral images that will be obtained with the NIRSpec and MIRI spectrometers. These data in highly processed format as well as some analysis tools will be made available to the community in the months following the observations, and can be used to address key questions regarding PDR physics and chemistry which I will discuss. These efforts will contribute to a better understanding of the interaction of UV radiation with gas and dust, providing tools for the interpretation of JWST spectra which will be dominated by PDR emission throughout the Universe.