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Nicola Da Rio Department of Astronomy , University of Florida

The Orion Nebula Cluster as a Paradigm of Star Formation Space Telescope Science Institute, October 13-16 2013. The pre-main sequence population of the Orion Nebula Cluster. Optical studies. Nicola Da Rio Department of Astronomy , University of Florida.

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Nicola Da Rio Department of Astronomy , University of Florida

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  1. The Orion Nebula Cluster as a Paradigm of Star Formation Space Telescope Science Institute, October 13-16 2013 The pre-main sequence population of the Orion Nebula Cluster. Optical studies Nicola Da Rio DepartmentofAstronomy,Universityof Florida M. Robberto (STScI) – R. Jeffries (Keele) – J. Tan - L. Hillenbrand (Caltech) – D. Soderblom (STScI) – C. Manara (ESO) – G. Scandariato(INAF Catania) – M. Reggiani(ETH) – F. Palla(INAF Arcetri) – K. Stassun(Vanderbild) – L. Ricci (Caltech)

  2. Censusof the ONC population “Complete” census of the PMS population in the Orion Nebula Cluster. (Da Rio et al, 2009, 2010, 2012) Individual spectral types and AV for >1800 sources. 40’x40’ – 3pc x 3pc 2.2 ESO-MPG/WFI UBVI+Ha+620nm (2005) I + 770nm + 753nm (2010) Survey started as part of the HST Orion Treasury Program Ongoing updates are being carried out.

  3. Spectral types • Collection of spectral types from Hillenbrand (1997) • >200 new spectral types from 620nm narrow band photometry (Da Rio et al 2010)

  4. Spectral types • Collection of spectral types from Hillenbrand (1997) • >200 new spectral types from 620nm narrow band photometry (Da Rio et al 2010) • >500 new spectral types from 770nm narrow band photometry (Da Rio et al 2012)

  5. Empirical calibration of stellar colors what are the intrinsic (photospheric) colors of young PMS stars? do the intrinsic colors depend on age? Intrinsic optical colors in Orion • differ from MS dwarfs • are not reproduced by current atmosphere models MS 2Myr isoch Inaccurate calibration of colors and temperature scale systematic offsets in AV, masses, ages (see also Naylor et al works) Av = 2

  6. Accretion excess in the broad-band optical colors Colors are shifted to the blue due to accretion hot spots on the stellar surface Disentangling accretion and extinction for individual stars: • Simulation of an accretion spectrum, considering optically thick + thin emission. • Computation of the shifts in the colors adding Laccto a star of given temperature • Solution for Laccand AV from multi-band photometry and known spectral type. Better estimate of AV Not a good indicator for the determination of Lacc

  7. Substellar IMF in Orion Chabrier system Kroupa Chabrier stellar Dramatic lack of brown dwarfs in Orion -compared to canonical IMFs -compared to other young stellar clusters

  8. Contaminationof stellar samples and IMF contamination Previous works on BDs / substellar IMF in Orion also included under-luminous sources, likely background contaminants. (e.g. Slesnick et al 2004, Riddick et al 2007) Andersen et al. (2011) NICMOS photometry • no deficiency of BDs • Brown dwarfs segregated

  9. Stellar ages Isochronal ages show a spread of ~0.4 dex around 2.5Myr (model dependent!) This spread is not produced by uncertainties (Reggiani+2012) Several pieces of evidence (Disk-age correlation Jeffries et al 2011, and mass accretion – age biases, Da Rio et al submitted) point to a 0.2 dex real age spread Rob Jeffries’ talk Bayesian estimate of allowed combinations of age spread, uncertainties and diversity of protostellar accretion to reproduce the observed HRD

  10. CTIO ISPI JHK photometry Meyer (1997) Robberto et al. (2010)

  11. CTIO ISPI JHK photometry Meyer (1997) Extinction map (Scandariato et al. 2011)

  12. CTIO ISPI JHK photometry Available Teff and AV + near-infrared photometry • Calibration of intrinsic colors and consequences on the IMF (Scandariato et al 2012) • CTTS NIR locus (Scandariato et al, in prep) Meyer (1997)

  13. Accuracyof stellar parameters The knowledge of the (in)accuracies severely impacts ours understanding of Orion see Reggiani et al. (2011) RMS=1.75 subtypes RMS=2.25 subtypes Hillenbrand (2013) Meyer (1997) Are we overestimating the accuracy of the stellar parameters? How many sources have VERY wrong assigned stellar parameters (see Manara et al 2013)

  14. (Non uniform) incompleteness • Spatially variable extinction • Inhomogeneous detection limits May cause Do cause selection effects when looking for correlations Meyer (1997)

  15. The Orion HST Treasury program Robberto et al (2013) 104 orbits Full coverage ACS BVIZ Ha WFPC2 UBI Ha Partial coverege NICMOS JH WFPC2 ACS NICMOS

  16. The Orion HST Treasury program Ricci et al (2009) catalog of proplyds Robberto et al (2009) evidence for a circumbinaryproplyd Press release, credits NASA/ESA and L. Ricci (ESO) and.. Manara et al. (2012) – accretion rates from WFPC2 U and Ha excess Reggiani et al (2011) – role of stellar parameter uncertainties in age spread Andersen et al (2011) – substellar IMF

  17. The Orion HST Treasury program ACS NICMOS 0.5M 0.5M 0.08M 0.08M 0.02M 0.02M FIELD The HST photometry is deep enough to reach down to planetary masses. The NIR surveys probe into the embedded populations. Lack of memberships or spectral types is limiting.

  18. Wekeep on usingonly a fractionof the information available • Spectral types collected by dozens of works • Multi band and multi-epoch photometry • Pan-Starrs • Membership estimators and other (circum)stellar properties: • Proper motions (Parenago 1954, Jones & Walker 1998, McNamara 1976, Tian et al. 1996) • X-ray emission (Getman+2005) • Disk excess (Megeath+2012, Morales-Caleron+2011) • Accretion tracers (Rebull, Manara, Da Rio, Robberto, …) • Stellar variability and rotation (Rodriguez-Ledesma+2009, Herbst+2002, Jeffries+) • Radial velocity (Furesz+2008, Tobin+2009,.. ) A universal (inspected and reasoned) catalog of all stellar information in the ONC? • Increase the sample • Detect and correct for problems • Improve estimates of stellar properties Black: ACS photometry Meyer (1997)

  19. Extensionof stellar censusto the south • Identical observational setup as in Da Rio et al (2012) • Is NGC1980 a foreground older cluster (Alves & Bouy 2012) • How does average age and age spread vary along the filament? Black: ACS photometry Meyer (1997)

  20. In-SyncOrionsurvey Tobin 2009 APOGEE fiber spectrograph at the SDSS High resolution NIR spectra of 2700 candidate members down to H=12.5 (0.5M) Radial velocities with 0.3-0.5 km s-1 accuracy of nearly all known members Larger coverage than previous works Less limited by extinction Black: ACS photometry Meyer (1997)

  21. Summary We have obtained the “full” census of the ONC stellar population. Unpublished updates are and will be present. The accuracy of derived stellar parameters is un part unclear. Beware of spatially non uniform incompleteness. IMF is deficient of brown dwarfs. Future extension of the sample to the lowest masses is needed to settle the debate. The full potential of the Orion HST Treasury program has not been yet used. We need deep surveys to get memberships and spectral types in the substellar range. A universal catalog of stellar properties in Orion could enable a number of new studies Coming soon: extension of census along the Orion A filament and RV

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