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James Owen (IoA, Cambridge) 24-11-2009
Observational Diagnostics of Photoevaporative Winds Around Primordial & Inner Hole Sources
James Owen (IoA,Cambridge)Cathie Clarke (IoA,Cambridge)
Barbara Ercolano (IoA Cambridge/UCL)Richard Alexander (Leiden/Leicester)
Emission From Wind= Blue Shift of a few km/s
-6±0.5 km/s
-4±2 km/s
[NeII] 12.8m
Pascucci & Sterzik (2009)
-3±1km/s
James Owen (IoA, Cambridge) 24-11-2009
An Example – TW Hya in [NeII]
Ercolano, Owen & Clarke 2010, in prep
EUV wind model-Massloss Rate 10-10M⊙ /yr
X-ray Model- Massloss Rate=10-8M⊙ /yr
[NeII] doesn't distinguish between photoevaporation models.
James Owen (IoA, Cambridge) 24-11-2009
The [O I] 6300 Problem
km/s
High Velocity Component
Low Velocity Component
Hartigan et al. 1995
Low Velocity Component detected with blue shift of a few Km/s and large luminosities of 10-5-10-4 L
⊙
EUV driven photoevaporative wind cannot reproduce this observation and predicts a line luminosity of <10-6L
⊙ (Font et al. 2004).
Problem: An EUV wind is an ionized wind but [O I] emission requires neutral Oxygen.
Solution:The [O I] LVC component must be produced in a partly neutral wind.
James Owen (IoA, Cambridge) 24-11-2009
The [O I] 6300 ProblemSolved?
Radius (cm)
Ionization Fraction of Owen et al. (2009) X-ray Driven Photoevaporative Wind
Velocity (km/s)
Line Luminosity ~10-4L
⊙
Ercolano, Owen & Clarke (2010) in prep
James Owen (IoA, Cambridge) 24-11-2009
Do We Always Expect to See Blue-Shifted Line Emission
No- Close to Edge on Primordial Discs Will Show No Blue Shift. No- Discs With Inner holes are Optically Thin to red-shifted gas
Inclination =54 degrees
Najita et al. 2009
James Owen (IoA, Cambridge) 24-11-2009
ConclusionsHave good observational evidence for a slow moving ~ few km/s neutral wind from YSO's. Photoevaporation mostly likely cause.
Must have a neutral wind in order to explain observed [O I] line luminosities :- X-ray photoevaporation over EUV photoevaporation?
Predicted line profiles from 'Transition Discs' significantly different from primordial discs for X-ray model allow test of source of emission/photoevaporation model.
Questions Can we use gas diagnostics to learn about the 'Transition' Phase?
Can we use line emmision to distinquish between photoevaporation and planet formation as the cause for a 'transistion' disc?
What observational diagnostics can we use to probe the photoevaporation at different radii?
What observational diagnostics can we use to probe photoevaporation in 'Transition Discs'?