Astronomical Observational Techniques and Instrumentation

1. Astronomical Observational Techniques and Instrumentation RIT Course Number 1060-771 Professor Don Figer Energy sources of astronomical objects

2. Aims and outline for this lecture • describe energy sources of astronomical objects • stars: nuclear reactions • protostars: gravitational energy • nebulae/clouds: stellar heating and ionizing radiation • galaxy clusters: shocks • give case studies of using multiwavelength data to analyze two star clusters

3. Stellar Structure

4. Solar Atomic Abundances

5. Solar System Atomic Abundances

6. Stars: energy source: proton-proton chain

7. Stars: energy source: proton-proton chain PPI (85% for Sun): H1 + H1 -> D2 + e+ + nu(1) (1.442 MeV) D2 + H1 -> He3 + gamma (5.493 MeV) He3 + He3 -> He4 + 2H1 (12.859 MeV) PPII (15%): H1 + H1 -> D2 + e+ + nu(1) (1.442 MeV) D2 + H1 -> He3 + gamma (5.493 MeV) He3 + He4 -> Be7 + gamma (1.586 MeV) Be7 + e- -> Li7 + nu(2) (0.861 MeV) Li7 + H1 -> He4 + He4 (17.347 MeV) PPIII (0.01%): H1 + H1 -> D2 + e+ + nu(1) (1.442 MeV) D2 + H1 -> He3 + gamma (5.493 MeV) He3 + He4 -> Be7 + gamma (1.586 MeV) Be7 + H1 -> B8 + gamma (0.135 MeV) B8 -> Be8 + e+ + nu(3) (followed by spontaneous decay...) Be8 -> 2He4 (18.074 MeV)

8. Stars: energy source: pp chain: Gamow Peak • Protons in center of star • have high energies • have the same charge (they repel each other) • At sufficiently high energy, particles will fuse.

9. Stars: energy source: pp chain timescales

10. Stars: energy source: CNO cycle

11. Stars: energy source: CNO cycle

12. Stars: energy source: CNO cycle • The CNO cycle has several branches that are favored based on temperature.

13. Stars: energy source: CNO vs PP • The CNO cycle produces more energy than the PP chain at higher temperatures.

14. Betelguese and Rigel in Orion Betelgeuse: 3,500 K (a red supergiant) Rigel: 11,000 K (a blue supergiant)

15. Blackbody curves for hot and cool stars

16. Two stars • Hotter Star emits MUCH more light per unit area  much brighter at short wavelengths.

17. Stars: energy source: Protostars

18. Stars: energy source: Gravitational Energy • As molecular cloud contracts, gravitational potential energy of particles is converted into kinetic energy. • With higher kinetic energies, the collision rate between particles increases, i.e. temperature and thermal radiation increase. • At sufficiently high density, the gas becomes opaque to escaping radiation at shorter wavelengths, making it difficult to observe the star formation process. • The radiation generated by gravitational energy cannot counterbalance the force of gravity of the overlying material. • Temperature increase until nuclear fusion turns on.

19. Star Formation: Hayashi Track hydrostatic equilibrium gravitational energy nuclear fusion 100,000 years from 4 to 6 10 million years from 6 to 7 timescales depend heavily on mass

20. Stages of Star Formation on the H-R Diagram

21. Arrival on the Main Sequence • The mass of the protostar determines: • how long the protostar phase will last • where the new-born star will land on the MS • i.e., what spectral type the star will have while on the main sequence

22. Protostar Luminosity Derivation

23. Optical Near-Infrared 1.2 mm Dust Continuum C18O N2H+ Star Formation: Gravitational Energy: B68 B68 is thought to be in hydrostatic equilibrium, such that the outward radiation pressure balances the inward force of gravity. The cloud should contract as it cools/radiates gravitational energy converted into kinetic energy.

24. 102 RY Tau x 10 104 Vega 1 DL Tau x 2 102 nFn (10-12 W m-2) 10-2 9700 K 1 10-4 GM Aur / 20 b Pic x 0.1 10-2 0.1 1 10 100 1000 0.1 1 10 100 1000 Wavelength (mm) Wavelength (mm) Disks & infrared emission Beckwith & Sargent 1996, Nature, 383, 139-144.

25. Spectrum of Protoostar McCaughrean et al. 1996

26. Circumstellar Dust Vega Disk Detection l Flux* Contrast (m) (Jy) Star/Disk 11m 2.4 1.5x107 22m 400 2x104 33m 1300 3x103 Reflected & emitted light detected with a simple coronograph. *per Airy disk

27. Star Formation: Debris Disks BD+31643

28. Dust Clouds: energy source • Dust clouds usually emit radiation that they absorb from stars (internal or external). • Young stars are often the internal heat source for star forming dust clouds, e.g. Sgr B2, W49, W51.

29. Dust Clouds: energy source: Sgr B2

30. Dust Clouds: energy source: Sgr B2

31. Dust Clouds: energy source

32. HCHII Regions in Sgr B2 Gaume et al. 1995 • There are ~100 HCHII regions in Sgr B2.

33. HCHII Regions in Sgr B2 De Pree et al. 1998 • The clumps break up into even smaller clumps with sizes ~100 AU and densities >107 cm-3. • Each clump contains an OB star.

34. Dust Clouds: energy source: external heating • M0.20-0.033 molecular cloud is warm (molecular emission in contours) • Notice that its surface is ionized (free-free emission in greyscale). • Pistol nebula is also ionized and heated.

35. Dust Clouds: energy source: external heating • M0.20-0.033 is externally heated by nearby Quintuplet cluster of massive stars. • Notice that its surface is ionized by the nearby hot stars. • Pistol is ejecta that is ionized/heated by Pistol star.

36. Dust Clouds: energy source: external heating: Pa-a

37. Nebulae: energy source: stars 3 um • The Pistol nebula is heated by the Pistol star that resides at its center. • Note in the figure that the dust thermal emission peaks in the mid-infrared, indicating temperature of a few 100 K. • The starlight fades in relative intensity at longer wavelengths. • Ionized gas emission suggest an external energy source (other hot stars in Quintuplet). 17 um

38. Galaxy Clusters: energy source: Shock Heating http://www-astro.physics.ox.ac.uk/~garret/teaching/lecture2.pdf

39. Galaxy Clusters: energy source: Shock Heating • Over last 10 Billion years there have been many galaxy collisions in galaxy clusters. • When two galaxies pass through each other stars will continue on their original path – more or less. • Interstellar gas clouds collide and cannot pass through each other. • They get stripped and pass into the gravitational well of the cluster. • This fills with very hot shocked gas over time. • So hot it emits x-rays. • Shows matter distribution. (Mostly dark matter again.)

40. Galaxy Clusters: energy source: Shock Heating blue=x-ray

42. Multiwavelength View of Energy Sources red=8um green=6 cm blue=20 cm red=8um green=5.8um blue=3.6um

43. Multi-wavelength analysis of star clusters: the cases of GLIMPSE9 and Cl1813-178 Cl1813-178 GLIMPSE9 90 cm

44. Cl 1813-175: Multiwavelength Image Messineo et al. (2008) ApJL, 683, 155 SNR G12.82-0.02 HESS J1813-178 SNR G12.72-0.0 W33 2MASS 3.6 um 8 um 90 cm

45. Cl 1813-175: Multiwavelength Plot 74 Chandra point sources from Helfand et al. (2007)

46. Cl 1813-175: NIR Spectroscopy Red supergiant Blue supergiants Keck/NIRSPEC high– and low–resolution spectroscopy

47. Cl 1813-175: CMD • 4.7 kpc • 6-8 Myr • Ak=0.8 mag • 2000-6000 Msun Chandra data from Helfand et al. (2006)

48. Cl 1813-175: distance • From the radial velocity of star #1, we derive a kinematic heliocentric distance of 4.7±0.4 kpc by using the rotation curve of Brand & Blitz (1993). • We conclude from the CMDs and distance estimates, that the RSG, the WR star, and the BSGs are all part of the same stellar cluster. The average spectrophotometric distance of 3.7 ± 1.7 kpc is consistent with the kinematic distance 4.7±0.4 kpc within uncertainties. We assume the kinematic distance.

49. Cl 1813-175: age and mass • We assume coevality of the evolved objects – 1 WR, 1 RSG, 2 BSGs, and several X–ray emitters. • We conclude that the cluster is 6 − 8 Myr old since this age allows for the coexistence of both WR and RSG stars. • Assuming that the other eight X–ray emitters associated with the cluster, other than the WR star, are BSGs with masses larger than 20 Msun, and by assuming a Salpeter IMF down to 1.0 Msun, we derive a total initial cluster mass of 2000 Msun. Messineo et al. (2008, ApJ 683-155)

50. 24 additional massive stars in CL 11813-178 (Messineo et al. in preparation)