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Seeing Stars with Radio Eyes

Seeing Stars with Radio Eyes. Christopher G. De Pree RARE CATS Green Bank, WV June 2002. Overview. Why study star formation? Some unanswered questions in star formation Successes and limitations of optical wavelength studies Advantages of radio wavelength studies

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Seeing Stars with Radio Eyes

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  1. Seeing Stars with Radio Eyes Christopher G. De Pree RARE CATS Green Bank, WV June 2002

  2. Overview • Why study star formation? • Some unanswered questions in star formation • Successes and limitations of optical wavelength studies • Advantages of radio wavelength studies • Recent discoveries in star formation • Conclusions

  3. Why study Star Formation? • We are made of star stuff • Nucleosynthesis creates elements through iron (Fe) • Supernovae create everything else • The death and birth of stars may be linked (triggered star formation) • Complex molecules can form on dust grains near young stars • Young stars “stir up” clouds of gas

  4. Why study Star Formation (cont.)? • Stars have a “life process” • Star Formation • Stellar Evolution • Supernovae, planetary nebulae • Where there are stars, there are planets • Effect on galactic evolution • The Antennae (Arp 224) • Andromeda HST with CO (BIMA)

  5. Giant Molecular Clouds in Andromeda

  6. The Process of Star Formation • Collapsing molecular cloud core • Inside-out collapse produces a protostar plus accretion disk • Bipolar molecular outflow carries away angular momentum • What do we look for to see the earliest stages? • Dense cloud cores • Infalling molecular material • Molecular disks/outflows

  7. Jet Example: Core of NGC 2071

  8. Open questions in star formation • Do all stars form planets? • Are accretion disks common to all star masses? • Do all young stars have outflows? For how long? • Do massive stars (>5 solar mass) form differently than low mass stars? • Do massive star outflows “stir up” molecular clouds?

  9. Optical wavelength studies • Best for studying • Source of ionization (stars) • Ionized gas (if unobscured, e.g. Orion) • Potential problems • Star forming regions are often highly obscured (e.g. NGC 253) • The early stages of star formation are not optically visible (radio, infrared) • Molecular material (fuel tank) best detected at radio frequencies • Deeply embedded ionized material best detected at radio frequencies

  10. Radio wavelength studies (star formation) • Molecular gas (the fuel tank) • Molecular clouds • Protostellar disks • Molecular outflows • Complex molecules

  11. Molecules and Outflows • Molecules in Orion • Distribution of molecules • Abundance of molecules • Source motions (rotations and outflows) • Presence of complex molecules • Potential for pre-life chemistry

  12. Viewing the Milky Way Galaxy • 90 cm image • A different view • Young stars • Dying stars • Magnetic fields • Ted LaRosa (Kennesaw)

  13. My Interests in this Puzzle • HII Regions (regions of ionized gas around massive stars) • High resolution imaging of the ionized gas • Kinematics (motions) of the ionized gas • Understanding the earliest stages of massive star formation

  14. Radio wavelength studies of HII Regions • Obscured ionized gas • High density gas (young regions) • Gas velocities (ionized outflows) • Ionized shells at the centers of outflows (e.g. G5.89 Observed with the VLA) • Disadvantage: resolution • Very Large Array (VLA) • Berkeley Illinois Maryland Association • Owens Valley Radio Observatory • But: VLA at 7 mm—same resolution as the Hubble Space Telescope

  15. Observing with the Very Large Array

  16. W49 Observed with the VLA(2000)

  17. W49A Star Forming Region at 600 A.U. Resolution (2002)

  18. “Bipolar Outflow”

  19. Spectral Lines/Bohr Model of the Atom

  20. “Imaging Spectroscopy”

  21. Recent Discoveries • Optical • Extrasolar planets (Doppler shift) • Protoplanetary disks (Orion) • Bipolar outflows (HH objects)

  22. Recent Discoveries • Radio • Rotating protoplanetary disks • Ionized and molecular outflows • High density regions • Outflows may support clouds

  23. What have we learned? • Some HII regions are much smaller and far brighter than previously thought • “Typical” HII regions were thought to be ~1 pc in diameter • “Typical ultracompact” HII regions that we study are ~0.01 pc in diameter • These new sources are younger and brighter—give us insight into an earlier phase of star formation • Spectral line detections—we see rotation and outflow in many sources

  24. Conclusions • Star formation studies tell us about... • Chemical evolution of the universe • Structure and evolution of galaxies • Enrichment of the space between the stars (the ISM) • Abundance of elements • Prevalence of planets • Radio observations reveal... • Embedded protostars • Rotating molecular disks • Molecular outflows • Complex organic molecules

  25. Future developments • The Millimeter Array (MMA) • 36 10-meter antennas • Llano de Chajnantor, Chile • Elevatation-16,400 feet • VLA Upgrade (EVLA) • Increased resolution • New correlator (spectral line & sensitivity) • Fully equipped at 7 mm

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