We estimate the mass-loss rates of photoevaporative winds launched from the outer edge of protoplanetary discs impinged by an ambient radiation field. We focus on mild/moderate environments (the number of stars in the group/cluster isN≳50), and explore disc sizes ranging between 20 and 250 au.We evaluate the steady-state structures of the photoevaporative winds by coupling temperature estimates obtained with a photodissociation region code with 1D radial hydrodynamical equations. We also consider the impact of dust dragging and grain growth on the final mass-loss rates. We find that these winds are much more significant than have been appreciated hitherto when grain growth is included in the modelling: in particular, mass-loss rates ≳10-8M⊙ yr-1 are predicted even for modest background field strengths (≳30G0) in the case of discs that extend to R > 150 au. Grain growth significantly affects the final mass-loss rates by reducing the average cross-section at far-ultraviolet wavelengths, and thus allowing a much more vigorous flow. The radial profiles of observable quantities (in particular surface density, temperature and velocity patterns) indicate that these winds have characteristic features that are now potentially observable with ALMA. In particular, such discs should have extended gaseous emission that is dust depleted in the outer regions, characterized by a non-Keplerian rotation curve, and with a radially increasing temperature gradient.

External photoevaporation of protoplanetary discs in sparse stellar groups: The impact of dust growth / S. Facchini, C.J. Clarke, T.G. Bisbas. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 457:4(2016), pp. 3593-3610. [10.1093/mnras/stw240]

External photoevaporation of protoplanetary discs in sparse stellar groups: The impact of dust growth

S. Facchini
;
2016

Abstract

We estimate the mass-loss rates of photoevaporative winds launched from the outer edge of protoplanetary discs impinged by an ambient radiation field. We focus on mild/moderate environments (the number of stars in the group/cluster isN≳50), and explore disc sizes ranging between 20 and 250 au.We evaluate the steady-state structures of the photoevaporative winds by coupling temperature estimates obtained with a photodissociation region code with 1D radial hydrodynamical equations. We also consider the impact of dust dragging and grain growth on the final mass-loss rates. We find that these winds are much more significant than have been appreciated hitherto when grain growth is included in the modelling: in particular, mass-loss rates ≳10-8M⊙ yr-1 are predicted even for modest background field strengths (≳30G0) in the case of discs that extend to R > 150 au. Grain growth significantly affects the final mass-loss rates by reducing the average cross-section at far-ultraviolet wavelengths, and thus allowing a much more vigorous flow. The radial profiles of observable quantities (in particular surface density, temperature and velocity patterns) indicate that these winds have characteristic features that are now potentially observable with ALMA. In particular, such discs should have extended gaseous emission that is dust depleted in the outer regions, characterized by a non-Keplerian rotation curve, and with a radially increasing temperature gradient.
Accretion, accretion discs; Circumstellar matter; Hydrodynamics; Planets and satellites: formation; Protoplanetary discs
Settore FIS/05 - Astronomia e Astrofisica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/866498
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