Observations

From Molecular Clouds to Dense Cores

From Molecular Clouds to Dense Cores

We have an active and diverse program to study the properties of molecular clouds and their connection with dense cores. Since molecular clouds provide the initial conditions for dense cores, it is important to determine some of their main properties: the amount of turbulence in the molecular cloud and inside dense cores, the amount of energy radiated by turbulent dissipation, and the role of magnetic fields. We have studied distant Infra-Red Dark Clouds (IRDCs) and nearby molecular clouds in dense gas tracers, using both single dish and interferometers, to reveal a large fraction of dense gas (as traced by NH3) present in the intra-core medium and to highlight the presence of subsonic turbulence inside dense cores even in the higher-mass star-forming regions traced by IRDCs. The relation between the kinematics and other physical properties of the dense cores and their parental molecular clouds has been explored. In addition, a systematic study of mid-J to high-J CO transitions in IRDCs provided a possible detection of the energy generated by turbulent dissipation. Finally, a comparison between Planck and polarization of background stars was carried out and it showed small differences between both techniques, confirming the validity of the Planck based polarization measurements in molecular clouds.
Dense Cores

Dense Cores

Dense cores are regions within interstellar molecular clouds where stars like our Sun form. In the CAS group a lot of effort is put into studying dense cores with the aim of deriving more constraints for star and planet formation. The collaboration among observers and modellers, as well as the input from laboratory spectroscopists, are crucial to make progress and have a full understanding of the chemical and physical evolution of dense cores. 
Being the chemical and physical evolution of dense cores deeply interconnected, we use molecular emission lines to derive information on the chemical as well as the physical structure of dense cores.
With the use of full radiative transfer models, and with the observations of different molecules and also different excitation lines, we can get a tomographic view of the physical and chemical structure of pre-stellar cores (e.g. Lin et al. submitted). Furthermore, the observations of emission lines of thick and thin tracers towards dense cores in combination with state-of-the-art chemical models (e.g. Sipilä et al. 2018) allows us to observe the contraction of pre-stellar cores, as well as the envelope that surrounds them (e.g. Ferrer Asensio et al. and Redaelli et al. submitted)
Moreover, we extensively use isotopic fractionation to gain information on the evolution of the chemical budget in the process of star- and planetary systems formation (e.g. Spezzano et al. 2022 and Giers and al. submitted).
The Evolution of Circumstellar Disks

The Evolution of Circumstellar Disks

Young circumstellar disks regulate the accretion of material from protostellar envelopes to protostars and, in later stages, provide the physical conditions for planet formation. The research done in the CAS group spans several stages of disk evolution, from young embedded disks to more evolved protoplanetary disks. We use state-of-the-art instrumentation
including ALMA, NOEMA, and SOFIA which cover a range of observational frequencies and spatial resolutions. Here we present the advancements made by the CAS group using observations of molecular lines, polarization, and dust continuum data.
High-mass Star Formation
High mass stars (M > 8 Msun) play a key role in the energetic budget of the interstellar medium, especially during the last stages of their evolution, when they explode as supernovae. They are rare and short-lived, if compared to low-mass counterparts, and as a consequence on average they are found more distant from the Solar System. They form in dense and crowded environments, known  as infrared dark clouds (IRDCs), heavily obscured by dust extinction. As a result, observational studies of the initial stages of high-mass star formation are challenging. In the CAS group, we exploit state-of-the-art interferometric facilities, such the Atacama Large Millimeter and sub-millimeter Array (ALMA), to characterize the physical properties of these regions, in particular in terms of their fragmentation in cores and their kinematics. more
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