1. Eric Feigelson Penn State University ONC/Paradigm for Star Formation STScI Oct 2013 The ONC and the MYStIX Survey Massive Young Star-Forming Complex Study in Infrared and X-ray

2. Outline Introduction: Orion as a template for rich young clusters The MYStIX Project … a very quick introduction Comparison of ONC with other clusters Conclusion ONC is a good template for young stellar clusters

3. The Orion Nebula: Nearest massive star forming region Orion Nebula Cluster OB-dominated star cluster age ~1-2 Myr Becklin-Neugebauer Small cluster of protostars Protoplanetary disks around Orion stars

4. Orion Molecular Cloud complex (IRAS 60  m, left) + molecular filament in Ori A (SCUBA 850  m, right) 20 pc 1 pc Complexity on many scales

5. Orion Extended Nebula in X-rays Guedel et al. 2008 4-5 Myr 1-2 Myr 0 Myr Alves & Bouy 2012 Multiple star clusters with age gradient

6. Chandra Orion Ultradeep Project All pre-main sequence stars are seen in X-rays

7. COUP: The Movie PMS stars exhibit high levels of magnetic flaring COUP: 22 papers Feigelson, Getman, et al. (2005-07)

8. During the Chandra mission, we increasingly realized that X-ray images were useful for improving the census of young stellar populations. Chandra resolution and FOV is most effective for star forming regions at 0.5<d<3 kpc. A V ~0-20 is not a problem, and penetration to A V ~200 is possible. X-ray selection complements more common H  and infrared-excess selection for PMS stars. Together they give Class I-II-III populations. The X-ray Perspective

9. MYStIX Massive Young stellar complex Study in Infrared and X-ray Multiwavelength surveys of 20 massive star forming regions Data analysis: 2009-12 Papers: 2013-15 Led at Penn State by Eric Feigelson & Leisa Townsley with Michael Kuhn, Kostantin Getman, Patrick Broos, Matthew Povich, Heather Busk, Tim Naylor & others Papers & electronic tables at http://www.astro.psu.edu/mystix

10. The MYStIX Sample

11. The Chandra Data Advanced data analysis gives X-ray source catalog with ~2x more sources than standard wavelet-based procedures. Light contamination (mostly quasars) is easily removed. Typical MYStIX target gives 500-3000 young stars. Kuhn et al. 2013a Townsley et al. 2013

12. X-ray `color-magnitude’ diagram MPCM = MYStIX Probable Complex Member Black = MPCMs Green = AGNs Blue = Unclassified Red/Orange = Field stars

13. The UKIRT Data UKIDSS pipeline improved with smaller apertures and higher sensitivity King, Naylor et al. 2013

14. The Spitzer Data Difficult to detect stars in nebulosity Crowding: lower resolution than UKIRT or Chandra Field star contami- nation can be bad! Sensitivity is spatially inhomogeous Kuhn et al. 2013b 3.6 um 8.0 um W 40 NGC 2264

15. k Black = field stars Red = MIRES (MYStIX IR excess sources) Green = disk- free MPCMs Povich et al 2013

16. Yellow = X- ray selected Red = MIRES Cyan = Published OB MPCMs: MYStIX Probable Complex Members Broos et al. 2013

17. Relative sizes of some MYStIX Clusters ONC W40 NGC 2264 NGC 6334 NGC 6357 Eagle Trifid Tr 15 Tr 14 Tr 16 Greater Carina Nebula South Pillars 30 pc

18. Finite Mixture Model 1.Cluster properties determined through maximum likelihood parameter estimation 2.Number of clusters determined with penalized likelihood criterion (AIC) 3.Membership determined using posteriors of fitted models Cluster 1 Unclustered component Cluster 2 Kuhn et al. 2013a

19. ONC region modeled as multiple subclusters Core-halo structure Stellar Sample Residual map after removal of iso- thermal ellipsoids

20. (Sub)Cluster Sizes Our sample: Mean ~ 0.18 pc SD ~ 0.4 dex Similar to core size of ONC, found by Hillenbrand & Hartmann (1998). Similar to width of molecular filaments found by André et al. (2010). log Core Radius [pc] -1.5 -0.5 0.0 16 0 8 24 Number of Clusters ONC

21. Central Core Density vs. Core Radius The ONC is denser than most OB-dominated clusters but not as dense as smaller clusters Kuhn et al. 2013b, see Pfalzner 2009, 2012 ONC

22. “We seem to be getting a picture of star forming regions with multiple non-coeval subclusters that probably formed with roughly the same physical size, but have expanded like the clusters studied by Pfalzner.” Mike Kuhn In Orion, these non-coeval subclusters are (from north to south): t~ 0.1 Myr OMC 4-3-2, OMC-1 (BN-KL), OMC-1S t~ 1.2 MyrONC core t~ 2.0 MyrONC halo t~ 4-5 MyrNGC 1980 (Alves & Buoy 2012)

23. A new age estimate for young stellar clusters Traditional optical HR diagram are restricted to low-A V stars, and infrared disk classes or fractions are poorly calibrated. Age JX is a new age estimator based on an established empirical calibration between X-ray luminosity and mass  combine with M J  unique location on evolutionary tracks  age. Individual Age JX values are still very uncertain, but median within MYStIX subclusters give low spread. Careful sample selection: strong X-ray, reliable near-IR photometry, median cluster age estimates Getman et al. 2013

24. Age estimates averaged over MYStIX fields 0.5 Myr 5 Myr Youngest: W 40 Flame Nebula RCW 38 ONC: In the middle Oldest: NGC 2362 Carina (mixed) Rosette (mixed) Getman et al. 2013a ONC

25. Getman et al. 2013b (tentatively reported by Reggiani et al 2011) Intracluster age gradient seen in ONC and Flame Nebula cluster Halos have older stars than cores Result for PMS stars, unrelated to mass segregation ONC Age JX sample ONC median Age JX in radial bins

26. Emark: A diagnostic summary function for spatial dependence of a mark variable Orion Nebula Cluster Mean mass (null hypothesis) 99% confidence envelope from bootstrap simulations Large values indicate strong mass segregation [Mo] pc r (parsecs) Kuhn et al., in prep

27. Eagle Nebula No mass segregation Kuhn et al., in prep

28. Conclusion ONC is a good template for clustered star formation Typical isothermal ellipsoid structure Typical core radius Higher than usual density (but on cluster expansion locus) Typical age for clusters ionizing giant HII regions Part of typical SF region age gradient (~10 pc scale) ?Typical? intracluster age gradient (halo forms first) Typical (but not ubiquitous) mass segregation