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

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Presentation on theme: "1 Astronomical Observational Techniques and Instrumentation RIT Course Number 1060-771 Professor Don Figer Energy sources of astronomical objects."— Presentation transcript:

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

2 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 3 Stellar Structure

4 4 Solar Atomic Abundances

5 5 Solar System Atomic Abundances

6 6 Stars: energy source: proton-proton chain

7 7 PPI (85% for Sun): H1 + H1 -> D2 + e+ + nu(1) (1.442 MeV) D2 + H1 -> He3 + gamma (5.493 MeV) He3 + He3 -> He4 + 2H1 ( 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 ( 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 ( MeV)

8 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 9 Stars: energy source: pp chain timescales

10 10 Stars: energy source: CNO cycle

11 11 Stars: energy source: CNO cycle 12 C + 1 H→ 13 N + γ+1.95 MeV 13 N→ 13 C + e + + ν e MeV 13 C + 1 H→ 14 N + γ+7.54 MeV 14 N + 1 H→ 15 O + γ+7.35 MeV 15 O→ 15 N + e + + ν e MeV 15 N + 1 H→ 12 C + 4 He+4.96 MeV

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

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

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

15 15 Blackbody curves for hot and cool stars

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

17 17 Stars: energy source: Protostars

18 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 19 Star Formation: Hayashi Track gravitational energy nuclear fusion 100,000 years from 4 to 6 10 million years from 6 to 7 timescales depend heavily on mass hydrostatic equilibrium

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

21 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 22 Protostar Luminosity Derivation

23 23 Star Formation: Gravitational Energy: B mm Dust Continuum C 18 O N 2 H + Optical Near-Infrared 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 24 Beckwith & Sargent 1996, Nature, 383, Disks & infrared emission

25 25 Spectrum of Protoostar McCaughrean et al. 1996

26 26 Vega Disk Detection Flux* Contrast  m) (  Jy) Star/Disk 11  m x  m 400 2x  m x10 3 Reflected & emitted light detected with a simple coronograph. Circumstellar Dust *per Airy disk

27 27 Star Formation: Debris Disks BD+31643

28 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 29 Dust Clouds: energy source: Sgr B2

30 30 Dust Clouds: energy source: Sgr B2

31 31 Dust Clouds: energy source

32 32 HCHII Regions in Sgr B2Gaume et al There are ~100 HCHII regions in Sgr B2.

33 33 HCHII Regions in Sgr B2De Pree et al The clumps break up into even smaller clumps with sizes ~100 AU and densities >10 7 cm -3. Each clump contains an OB star.

34 34 Dust Clouds: energy source: external heating M 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 35 Dust Clouds: energy source: external heating M 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 36 Dust Clouds: energy source: external heating: Pa- 

37 37 Nebulae: energy source: stars 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). 3 um 17 um

38 38 Galaxy Clusters: energy source: Shock Heating

39 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 40 Galaxy Clusters: energy source: Shock Heating blue=x-ray

41 41

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

43 43 Cl GLIMPSE9 Multi-wavelength analysis of star clusters: the cases of GLIMPSE9 and Cl cm

44 44 W33 SNR G SNR G HESS J MASS 3.6 um 8 um 90 cm Messineo et al. (2008) ApJL, 683, 155 Cl : Multiwavelength Image

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

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

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

48 48 Cl : 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 49 Messineo et al. (2008, ApJ ) Cl : 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.

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

51 51 GLIMPSE9: location (l,b)=(22.76°, -0.40°) HST/NICMOS f.o.v. = 51.5”x51.5”; pixel scale = 0.2”; filters = F160W, F222M exptime = 19.94s, 55.94s

52 52 Age = 6-30 Myr (presence of RSGs) Ak = 1.6 ± 0.3 mag #3 4.2 kpc #4 4.7 kpc

53 53 Cluster surroundings Giant Molecular cloud – from CO 10^6 Msun -- 4 SNR remnants Blue = 3.6 um Green = 90 cm Red = 24 um

54 54 REG1 REG3 REG4 REG6 Ongoing ESO observations with SINFONI to observe the brightest stars of REG1, REG3, REG4 and REG6

55 55 GLIMPSE9 and CL Summary GLIMPSE9 and CL are two young clusters. The combination of radio and infrared data allowed us to detect their parental clouds, which appear rich in HII regions and SNRs. With similar studies of other clusters and giant HII regions we will be able to shed light on the initial masses of the supernova progenitors, and therefore on the fate of massive stars.


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