arXiv subjects

Milena Benedettini

Publications and source records attributed to Milena Benedettini.

21 records · Page 2Linked to original sources

arXiv2006

A detailed modelling of the chemically rich clumps along the CB3 outflow

In order to investigate the origin and the structure of the low velocity, chemically rich clumps observed along the lobes of low- and intermediate-mass outflows, we construct a detailed model of the S1 clump along the CB3 outflow. We use a time-dependent chemical model coupled with a radiative transfer model to reproduce the observed line profile for a direct comparison with previous observations of this clump. We find that the simultaneous fitting of multiple species and transitions is a powerful tool in constraining the physical parameters of the gas. Different scenarios for the clump formation have been investigated. The models that better reproduce all the observed lines are those where the clump is formed, at least partially, before the advent of the outflow; with the advent of the outflow the clump undergoes a short period of non-dissociative shock and the consequent release of the icy mantle together with the high temperature chemistry leads to the observed chemical enrichment. Our results also suggest the presence of substructure within the clump: a more extended component traced by CS, SO and the lower energy transitions (3_k-2_k and 2_k-1_k) of CH_3OH, and a more compact component traced by H_2CO, SO_2 and the higher energy transitions (5_k-4_k) of CH_3OH.

astro-ph↗

arXiv2004

The origin and structure of clumps along molecular outflows: the test case of CB3

We investigate the origin of the small, chemically rich molecular clumps observed along the main axis of chemically rich outflows such as CB3 and L1157. We develop a chemical model where we explore the chemical evolution of these clumps, assuming they are partially pre-existing to the outflow, or alternatively newly formed by the impact of the outflow on the surrounding medium. The effects of the impact of the outflow are reproduced by density and temperature changes in the clump. We find that the observed abundances of CH3OH, SO and SO2 are best reproduced by assuming a scenario where the dense molecular gas observed is probably pre-existing in the interstellar medium before the formation of their exciting (proto)stars and that the clumpiness and the rich chemistry of the clumps are a consequence of a pre-existing density enhancement and of its interaction with the outflow.

astro-ph↗

arXiv2003

The ISO-LWS far-infrared spectra of pre-Main Sequence objects

The Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO) satellite has allowed for the first time to investigate the whole far infrared (FIR) part of the spectrum (from 43 to 197 um), inaccessible from the ground. The FIR spectrum is crucial for the study of the early phases of protostellar evolution since the peak of the continuum emission of the protostars falls around 100 um and many molecular species emit in this range. In this paper we review the main results of the spectroscopic observations carried out with the LWS on a sample of pre-Main Sequence objects in different evolutionary stages. The FIR spectra are characterized by a strong continuum with superimposed atomic and molecular emission lines. The fine structure lines emitted by the OI and CII atoms are present in all the objects of our sample while emission from molecular species (CO, H_2O and OH) dominate the spectrum of the younger and more embedded objects; lines of highly ionized atoms (OIII, NIII, NII) are present only in high luminosity sources. We will show how both the FIR continuum and the emission lines are powerful indicators of the evolutionary status of young embedded objects. The analysis of the LWS spectra has allowed to study only the average properties of the young stellar objects, due to the large field of view (~ 80 arcsec), the limited sensitivity and the poor spectral resolution (~ 200) of the instrument in its grating mode. The higher spatial and spectral resolutions of the instruments on board the Herschel satellite will allow to address in deeper detail the scientific problems highlighted by the ISO results.

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