Post on 23-Feb-2016
description
Carlo Felice Manara1,2, Massimo Robberto, Nicola Da Rio3
Giuseppe Lodato1, HST Orion Treasury Program Team
HST MEASURES OF MASS ACCRETION RATES IN THE ORION NEBULA CLUSTER
1Università degli Studi di Milano (Italy), 2current address: ESO-Garching (Germany), 3current address: ESA (Netherlands)
From dust to stars and planets
Cloud collapse
104 yr
Disk formation
105 yr
Planetary system
109 yr107 yr
Low-mass binary
106 yr
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Fingerprints of acctretion
UV Excess
Calvet & Gullbring 1998 Gullbring et al. 2000
Muzerolle et al. 2001
Line emission (Hα)
T-Tauri star spectra
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
1*1
m
accacc R
RGMRLM
From tracers and accretion spectrum models
From Teff and Lstar(HRD)
From evolutionary modelsFrom models (~5 R*)
Rm
Camenzind 1990
Free-fall and accretion shock
From Rm to the star matter is in supersonic free-fall.
Material crashes on the star generating a shock.
Free-fall region:Line emission
Accretion Shock: UV excess
Magnetic field ~103 G
Magnetospheric accretion
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Navier-Stokes equations and solutions
2/12/13 R
RR
RRt
R
ttMacc)2/()2/5(
The azimuthal component of the Navier-Stokes equation is a diffusive equation of the surface density Σ:
With the assumption that the viscosity ν scales with the radius with a power law (self-similar solutions):
It is possible to obtain analytically a solution (Lynden-Bell & Pringle,1974) and, fort >> τᵥ, the mass accretion rate Ṁacc decreases with time with this power law:
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc evolution with age and Mass
Hartmann et al. 1998, Robberto et al. 2004, Calvet et al. 2005,2008, Fedele et al. 2010, Sicilia-Aguilar et al. 2010
Calvet et al. 2004,Muzerolle et al. 2003, 2005, Natta et al 2004, 2006, Hartmann et al. 2006, Rigliaco et al. 2011
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
WFPC2 dataset
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
1643 sources
F336W (U) F439W (B) F656N (Ha) F814W (I)
Detected 1021 997 1342 1610
Upper limit 481 521 215 11
Lower limit 5 11 19 19
Not detected 136 114 67 3
For 1131 of the WFPC2 sources Teff from Da Rio et al. (2011) available.
For 439 sources U, B, I band photometry and Teff available. 339 of them are used (corrected for red
leak no proplyds, binaries, big errors…)
For 897 sources U, B, I band photometry available.
Method
UBI Diagram (2CD) with:
Two Colors Diagram
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
•Atmosphere Models (Allard et al.2010)
•Accretion spectrum (Calvet et al.98)•75% optically thick emission (blackbody at 7000K)•25% optically thin emission (HII region with n=104 cm-3)
• Extinction law (Cardelli et al. 1989)
Teff (K)
+ HII region (magnetospheric emission)
Two Colors Diagram – Accretion Spectrum
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Observed 2CD
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Observed 2CD
Two Colors Diagram – Accretion Spectrum
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Two Colors Diagram – Accretion Spectrum
Dereddened 2CD
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Two Colors Diagram – Accretion Spectrum
Calvet & Gullbring 98
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Two Colors Diagram – Accretion Spectrum
C&G+Magnetosphere
Derivation of LACC and AV
The intersection of the reddening line (red) and the accretion curve (blue) determines simultaneously Lacc and AV.
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Estimate of Lacc and AV obtained for 247 sources.
LHa estimation
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
LACC from LHa - calibration
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Linear regression – no errors:
Linear regression – errors on LACC:
)20.027.2(log)05.023.1(log
Sun
H
Sun
accLL
LL a
)05.069.2(log)01.031.1(log
Sun
H
Sun
accLL
LL a
204 sources
LACC from LHa - calibration
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Linear regression – no errors:
Herczeg & Hillenbrand 2008:
)20.027.2(log)05.023.1(log
Sun
H
Sun
accLL
LL a
)70.027.2(log)16.031.1(log
Sun
H
Sun
accLL
LL a
Dahm 2008: )64.019.2(log)26.018.1(log
Sun
H
Sun
accLL
LL a
Linear regression – errors on LACC: )05.069.2(log)01.031.1(log
Sun
H
Sun
accLL
LL a
De Marchi et al. 2010: )47.072.1(loglog
Sun
H
Sun
accLL
LL a
LACC from LHa
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Linear regression – no errors: )20.027.2(log)05.023.1(log
Sun
H
Sun
accLL
LL a
Dahm 2008: )64.019.2(log)26.018.1(log
Sun
H
Sun
accLL
LL a
497 sources with Lacc estimated from LHa
HR Diagram
With evolutionary models(e.g. D’Antona & Mazzitelli 1994)
derivation of M* and ageDerivation of Ṁacc for 743 sources (246 with 2CD and 497 from LHa)
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Results
Final sample
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Lacc vs Lstar
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
All data: b = 1.76 ± 0.01
Natta et al. 2006Clarke & Pringle 2006Tilling et al. 2008
b*LLacc
2CD data: b = 1.60 ± 0.02Ha data: b = 1.77 ± 0.01
Tilling et al. 2008: b = 1.7 if = 1.5 and D’Antona &
Mazzitelli 1994 models are used.
Macc decreases with time
tMaccHartmann et al., 1998: =1.5.
Se si interpreta l’evoluzione del disco con modelli self similar (>1) ~R, i.e. a= costante
Ṁacc ~ t-(1.44±0.02)
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
= 1.14±0.02
tMacc
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc decreases with time
= 1.14±0.02
= 1.33±0.03
tMacc
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc decreases with time
= 1.14±0.02 = 1.33±0.03 = 1.13±0.12
tMacc
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc decreases with time
= 1.13±0.12 = 0.56±0.08
tMacc
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
= 1.14±0.02 = 1.33±0.03
Macc decreases with time
= 0.56±0.08
≈ 0
tMacc
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
= 1.13±0.12
= 1.14±0.02 = 1.33±0.03
Macc decreases with time
Muzerolle et al., 2003: Ṁacc ~ M*2
Natta et al., 2006: Ṁacc ~ M*1.8±0.2
Rigliaco et al., 2011: Ṁacc~ M*1.6±0.4
Ṁacc ~ M*1.545±0.003
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc increases with Mstar
Muzerolle et al., 2003: Ṁacc ~ M*2
Natta et al., 2006: Ṁacc ~ M*1.8±0.2
Rigliaco et al., 2011: Ṁacc~ M*1.6±0.4
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc increases with Mstar
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Macc spatial distribution
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Conclusion
• We derived Lacc in two different ways: 2CD and Ha
• Obtained Macc for 743 sources
• Macc vs age: there is a dependence -> age spread,
hint of slower evolution for higher masses
• Macc vs M*: big spread, partly due to different ages
C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC
Future perspective
• Refine Lacc determination (accretion
spectrum…)
• Macc vs period
• Macc vs Mdisk
• Macc vs molteplicity (binaries)
• Other regions
Thanks