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Star Formation in the Local Group

Orion Nebula Cluster Workshop 16 October 2012. Star Formation in the Local Group. … as seen by low mass stars. Part 1. Nino Panagia STScI INAF/NA Supernova Ltd. Main Characters in this project. Guido De Marchi (ESA) Nino Panagia (STScI) Martino Romaniello (ESO) Giacomo Beccari (ESO)

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Star Formation in the Local Group

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  1. Orion Nebula Cluster Workshop 16 October 2012 Star Formation in the Local Group … as seen by low mass stars Part 1 Nino Panagia STScI INAF/NA Supernova Ltd Low Mass PMS Stars Nino Panagia

  2. Main Characters in this project Guido De Marchi (ESA) Nino Panagia (STScI) Martino Romaniello (ESO) Giacomo Beccari (ESO) Francesco Paresce (INAF) Loredana Spezzi (ESAESO) Elena Sabbi (ESA/STScI) Marco Sirianni (ESA) Morten Andersen (ESA) Low Mass PMS Stars Nino Panagia

  3. www.starformation.eu Low Mass PMS Stars Nino Panagia

  4. Motivations • Solar mass stars account for most of the star formation in a galaxy • Low mass stars can form in small clouds as well as in big ones • Low mass stars are forming both near massive stars and in isolated groups Low Mass PMS Stars Nino Panagia

  5. In order to understandhow star formation proceeds • We have to study • Many young stars • In diverse environments Low Mass PMS Stars Nino Panagia

  6. Interpreting observations of “resolved” stellar populations Input • Stellar Evolution • Mass-loss/Rotation [Metallicity] • Extinction Output • Stellar Properties • Age [Metallicity] • Initial Mass Function [?] • Star Formation History Low Mass PMS Stars Nino Panagia

  7. Crowding Limits for MS stars stars/ACS PSF area Scaled LF for SN 1987A field s(B) ~ 21 mags/arcsec2 Low Mass PMS Stars Nino Panagia

  8. A novel method to identify and study PMS stars Low Mass PMS Stars Nino Panagia

  9. PMS stars: How to find them? Low-mass stars grow in mass over time through accretion of matter from a circumstellar disc (e.g. Lynden-Bell & Pringle 1974; Bertout 1989) Typical signature: UV, IR and Hα excess emission How to measure it? 1- Spectroscopy 2- Photometry (De Marchi et al. 2010) Low Mass PMS Stars Nino Panagia

  10. Spectroscopy made easy… • New simple method combines broad-band (V, I) and • narrow-band (H ) photometry and allows us to: • identify all objects with H excess emission • derive their accretion luminosity and mass accretion rates • for hundreds of stars simultaneously! (De Marchi, Panagia & Romaniello 2010, ApJ, 715, 1)

  11. PMS stars and photometry V I Hα Low Mass PMS Stars Nino Panagia

  12. givesL(H) H photometry De Marchi, Panagia & Romaniello 2010 De Marchi et al. 2011 LMC(SN 1987A) SMC(NGC 346) ( )0 ( )0 9,300 K 5,000 K 3,500 K 9,300 K 5,000 K 3,500 K ( )0 ( )0

  13. • Free fall equation gives mass accretion rate M Stars physical parameters H luminosity LH gives accretion luminosity Lacc via a relationship based on simple physics and calibrated using spectroscopic data Log (Lacc) = Log (LH) + 1.72 Mass M radius R and age t from PMS isochrones in HR diagram    We can study how star formation has proceeded in space and time Low Mass PMS Stars Nino Panagia

  14. A little history Low Mass PMS Stars Nino Panagia

  15. Our first two regions in the LMC Low Mass PMS Stars Nino Panagia

  16. NGC 1850 Neighborhood

  17. NGC1850A & B Gilmozzi et al. 1994, ApJ 435, L43 The second brightest stellar cluster in the Large Magellanic Cloud NGC 1850A • Globular-like • 50 Myrs old • Flat IMF: 0.4 NGC 1850B • Spatially diffuse • 4 Myrs old • “Normal” IMF: 1.6 A B Low Mass PMS Stars Nino Panagia

  18. NGC 1850 B 4 Myrs First detection of Pre-Main-Sequence stars outside the Milky Way Gilmozzi et al 1994 A 50 Myrs 1 Gyrs PMS PMS

  19. NGC 1850 - H Excess Stars (Romaniello et al. 2013, in preparation) -Weq(H)>10Å 4Myrs 4Myrs 50Myrs 50Myrs Be-Ae Be-Ae T Tau PMS Low Mass PMS Stars Nino Panagia

  20. NGC 1850 - Spatial Distribution Markedly different spatial distributions for O type and PMS stars O type star Be-Ae star PMS star Low Mass PMS Stars Nino Panagia

  21. NGC1850 - Conclusions • Different spatial distributions for massive (>10M) and low mass (<2M) stars of the same generation imply different star formation processes • IMF meaningful only in a statistical sense, i.e. averaged over a large volume and large number of stars • Similar results obtained in the field of SN1987A and other LMC/SMC star forming regions Low Mass PMS Stars Nino Panagia

  22. The Field around SN 1987A Low Mass PMS Stars Nino Panagia

  23. The Field around SN 1987A Stars with Ha excess (-Weq>10A) Panagia et al. 2000

  24. SN 1987A FieldMassive Stars vs PMS Stars Panagia et al. 2000 Low Mass PMS Stars Nino Panagia

  25. PMS Stars in SN 1987A field PMS stars far from UV sources have higher L(Ha) Ha Luminosity L(Ha) > 0.020 L L(Ha) < 0.020 L > 0.008 L oL(Ha) < 0.008 L Evidence for Disk Photo-Evaporation De Marchi et al 2010 Low Mass PMS Stars Nino Panagia

  26. These are our motivationsand our methods… Low Mass PMS Stars Nino Panagia

  27. Guido will talk about our results and our ongoing programs Low Mass PMS Stars Nino Panagia

  28. Next… Low Mass PMS Stars Nino Panagia

  29. Orion Nebula Cluster Workshop 16 October 2012 Star Formation in the Local Group … as seen by low mass stars Part 2 Guido De Marchi ESA Low Mass PMS Stars Nino Panagia

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