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A Star is Born

Director : Dr Karl Gordon (STScI) ‏ Production Designer : Arpit Gupta (Dept of Physics & Astronomy, JHU) ‏. A Star is Born. Box office collection : 10. Outline. Judy Garland Star Formation & its Indicators Summer of 2008 Speculations & Expectations. Judy Garland.

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A Star is Born

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  1. Director : Dr Karl Gordon (STScI)‏ Production Designer : Arpit Gupta (Dept of Physics & Astronomy, JHU)‏ A Star is Born Box office collection : 10

  2. Outline • Judy Garland • Star Formation & its Indicators • Summer of 2008 • Speculations & Expectations

  3. Judy Garland • Frances Ethel Gumm, b. June 10, 1922 • Won oscar, Golden Globe, Tony & Grammies. • Married 5 times • d. June 22, 1969

  4. Star Formation • Giant Molecular Cloud – Molecular hydrogen • H II region – ionized atomic hydrogen • Emit large amounts of UV radiation (hot, young stars)‏ • Obscured by inter-stellar dust * Picture courtesy of NASA/ESA

  5. Why study star formation ? • Galaxy classification • Galaxy evolution • Physical nature of galaxies

  6. Star Formation Indicators • Spectrum Analysis -- UV, optical & IR • Initial Mass Function --- Star formation rate (in terms of mass) determined from luminosities. • SFR (solar mass/year) = Constant x L (ergs/s)‏ * Kennicutt Jr, Annu Rev Astron Astrophys 1998.36:189-231

  7. UV & optical SFTs • UV is obscured by dust. • Hα line : n = 3 →2 ; 656.3 nm; red • Optical wavelengths also suffer dust extinction. • Dust obscuration -- • depends on geometrical distribution of emitters wrt dust. • unknown fraction of star formation obscured by dust. * Calzetti et al, ApJ 633:871-893, 2005

  8. Infra Red SFTs • Absorption cross-section peaks in UV. • TIR & 24 micron accepted as good tracers. • Old stars also contribute to IR emission. • Spitzer Space Telescope (2003- )‏ • InfraRed Array Camera (3.6,4.5,5.8 & 8 micron)‏ • Multiband Imaging for Spitzer (24,70 & 160 micron)‏ * Calzetti et al, ApJ, 666:870-895, 2007

  9. M33-Triangulum Galaxy • Spiral galaxy • 840kpc or 3m light -years away • Lacks a blackhole at the center • Sufficiently close & face-on * Hinz et al, ApJ supplement series, 154:259-265, 2004

  10. Data • MIPS & IRAC images • Resolution – 160 micron • Photometry -- • Aperture (extended regions)‏ • Point Spread Function (compact regions)‏

  11. Apeture Photometry

  12. PSF Photometry • PSF corresponding to 160 micron • Matching the List – Aperture + PSF • 8, 24, 70 & 160 micron • Total Infra-Red flux (TIR) defined appropriately.

  13. Independent of Aperture Size

  14. Warm dust component

  15. Cold dust component

  16. Speculations & Expectations • 70 micron may be better • 8 micron – SFT or PAH emission • Fits to different dust models ( Ka-Hei Law's Presentation)‏ • 24 micron may not be a good tracer

  17. 92 = 81 32 = 09 62 = 36 12 = 1 992 = 9801 332 = 1089662 = 4356 112 = 121 9992 = 998001 3332 = 110889 6662 = 443556 1112 = 12321 99992 =99980001 33332 = 1110888966662 =44435556 11112 = 1234321 Divisibility Tests if divisor is -- 3 – sum of digits (of dividend) should be a multiple of 3 6 – dividend should be even and satisfy the divisibility test for 3 9 – sum of digits (of dividend) should be a multiple of 9 7 – remove the last digit and subtract from the number thus left. The answer should be a multiple of 7. The process can be repeated more than once to easily see whether the number thus left is a multiple of 7 or not. 11 – sum the alternate digits. Difference of the two sums should be zero. 43 x47 2021 5272 = 277729 = ( 52 +2 = 27, 7,272 = 729)‏ (4x5) (7x3)‏

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