Carlo Felice Manara 1,2, Massimo Robberto, Nicola Da Rio 3 Giuseppe Lodato 1, HST Orion Treasury Program Team HST MEASURES OF MASS ACCRETION RATES IN THE ORION NEBULA CLUSTER 1 Università degli Studi di Milano (Italy), 2 current address: ESO-Garching (Germany), 3 current address: ESA (Netherlands)

From dust to stars and planets Cloud collapse 10 4 yr Disk formation 10 5 yr Planetary system 10 9 yr10 7 yr Low-mass binary 10 6 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 Muzerolle et al Line emission (Hα) T-Tauri star spectra C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC

From tracers and accretion spectrum models From T eff and L star (HRD) From evolutionary models From models (~5 R * ) RmRm Camenzind 1990 Free-fall and accretion shock From R m 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 ~10 3 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 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, for t >> τᵥ, the mass accretion rate Ṁ acc 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 Calvet et al. 2004, Muzerolle et al. 2003, 2005, Natta et al 2004, 2006, Hartmann et al. 2006, Rigliaco et al 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 Upper limit Lower limit51119 Not detected For 1131 of the WFPC2 sources T eff from Da Rio et al. (2011) available. For 439 sources U, B, I band photometry and T eff 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=10 4 cm -3 ) Extinction law (Cardelli et al. 1989) T eff (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 L ACC and A V The intersection of the reddening line (red) and the accretion curve (blue) determines simultaneously L acc and A V. C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC Estimate of L acc and A V obtained for 247 sources.

L H  estimation C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC

L ACC from L H  - 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 L ACC : 204 sources

L ACC from L H  - 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: Dahm 2008: Linear regression – errors on L ACC : De Marchi et al. 2010:

L ACC from L H  C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC Linear regression – no errors: Dahm 2008: 497 sources with L acc estimated from L H 

HR Diagram With evolutionary models (e.g. D’Antona & Mazzitelli 1994) derivation of M * and age Derivation of Ṁ acc for 743 sources (246 with 2CD and 497 from L H  ) 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

L acc vs L star C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC All data:  = 1.76 ± 0.01 Natta et al Clarke & Pringle 2006 Tilling et al CD data:  = 1.60 ± 0.02 H  data:  = 1.77 ± 0.01 Tilling et al. 2008:  = 1.7 if  = 1.5 and D’Antona & Mazzitelli 1994 models are used.

M acc decreases with time Hartmann et al., 1998:  =1.5. Se si interpreta l’evoluzione del disco con modelli self similar (  >1)  R, i.e.  = costante Ṁ acc ~ 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 C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC M acc decreases with time

 = 1.14±0.02  = 1.33±0.03 C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC M acc decreases with time

 = 1.14±0.02  = 1.33±0.03  = 1.13±0.12 C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC M acc decreases with time

 = 1.13±0.12  = 0.56±0.08 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 M acc decreases with time

 = 0.56±0.08  ≈ 0 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 M acc decreases with time

Muzerolle et al., 2003: Ṁ acc ~ M * 2 Natta et al., 2006: Ṁ acc ~ M * 1.8±0.2 Rigliaco et al., 2011: Ṁ acc ~ M * 1.6±0.4 Ṁ acc ~ M * 1.545±0.003 C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC M acc increases with M star

Muzerolle et al., 2003: Ṁ acc ~ M * 2 Natta et al., 2006: Ṁ acc ~ M * 1.8±0.2 Rigliaco et al., 2011: Ṁ acc ~ M * 1.6±0.4 C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC M acc increases with M star

C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC M acc spatial distribution

C.F. Manara, M. Robberto, N. Da Rio et al. – Mass Accretion Rates Measures in the ONC Conclusion We derived L acc in two different ways: 2CD and H  Obtained M acc for 743 sources M acc vs age: there is a dependence -> age spread, hint of slower evolution for higher masses M acc 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 L acc determination (accretion spectrum…) M acc vs period M acc vs M disk M acc vs molteplicity (binaries) Other regions

Thanks