james owen (ioa, cambridge) 24-11-2009 observational diagnostics of photoevaporative winds around...

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


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.


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.


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


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


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'?

james owen (ioa, cambridge) 24-11-2009 observational diagnostics of photoevaporative winds around...

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