ISM & Star Formation

Title: The physical and chemical signatures of a young protostar

Artur de la Villarmois, Elizabeth

Artur de la Villarmois, Elizabeth (Institute of Astrophysics, Pontificial Catholic University of Chile); Guzmán, Viviana (Institute of Astrophysics, Pontificial Catholic University of Chile)

Abstract: In the process of low-mass star and planet formation, the chemical composition of the early disk is crucial for the content of future planetesimals. At disk scales, some physical processes (such as accretions shocks) might alter the chemistry of the inner regions, forming new molecular species or destroying existing ones. Accretions shocks are predicted by theoretical models but are poorly constrained observationally, and may be essential for the chemical complexity of the disk. In some cases, accretion shocks have been invoked to explain the observed abundances of key species, such as SO and SO2.

I will present the case of IRS 44, a Class I protostar that shows strong, compact, and broad SO2 emission in ALMA data. The emission is associated with warm gas present in the inner-disk regions and may be tracing accretion shocks. In addition, there is evidence of an asymmetric infall of material from the envelope to the disk, and a misalignment between the infalling envelope and the Keplerian disk. IRS 44 is, therefore, an excellent laboratory to trace the dynamical evolution of a forming system and the accretion shock scenario, with its potential chemical complexity.

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Title: Unveiling NH3 Depletion in Pre-stellar Cores

Gaete Espinoza, Daniel

Daniel Gaete & Stefano Bovino, Universidad de Concepcion, Chile. Simon Ferrada, Université Grenoble Alpes, Grenoble, France. Alessandro Lupi, University of Milan Bicocca, Pisa, Italy.

Abstract: Ammonia (NH3) is a fundamental molecule in the interstellar medium, employed as a kinetic gas temperature probe and as tracer within cold high density regions. Under star-forming regions conditions, N-bearing molecules, similarly to CO and other heavy elements, are subject to freeze-out (or depletion), i.e. a decrease in their gas-phase abundance due to adsorption on dust grains surface. However, NH3 has a particular trait that have been under scientific scrutiny for decades: the non-depletion towards the center of pre-stellar cores.

No models have been able to reproduce observed NH3 profiles, and the physical reasons leading to this behaviour are poorly understood. Most of published works that looked over this phenomenon employed low dimensionality models leaving out some important physical processes. Here we present some preliminary results of our chemical post-processing scheme applied to a slow collapse pre-stellar core in a 3D-MHD simulation, aiming to test influence of some parameters over NH3 and its spin isomers and deuterated isotopologues evolution.

Click here to see the full poster (Gaete Espinoza, Daniel)

Title: Shocked Material in Massive Star Forming Regions: SiO as a Bipolar Outflow Tracer and Evolutionary Indicator

Guerra, Nicolás

Guerra, Nicolás; Merello, Manuel; Bronfman, Leonardo (Department of Astronomy, Universidad de Chile)

Abstract: This study aims to characterize molecular outflows associated with massive protostellar objects, through the emission of SiO and HCO+/H13CO+ lines, and to associate the presence of outflows with shocked gas. For this, we present APEX Band5 observations (beamwidth ~36’’) of SiO(4-3) bipolar outflow candidates towards a well selected sample of 32 luminous and dense clumps, which are candidates to harboring Hot Molecular Cores. The clumps properties are characterized using the H13CO+(2-1) line and continuum emission. Results show that 78% of our sources present SiO emission, revealing the presence of shocked material, 9 of which are also found to have wings in the HCO+(2-1) line, indicating outflow activity. The SiO emission of these 9 sources is generally more intense (Ta>1 K) and wider (~61 km/s FWZP) than the rest of the clumps with SiO detections (~42 km/s FWZP), suggesting that the outflows in this group are faster and more collimated. This agrees with the idea that the shocked material gets dispersed as the core evolves and outflow activity decreases. A positive linear correlation is found between the bolometric and SiO luminosities.

Click here to see the full poster (Guerra, Nicolás)