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Super star clusters and star-formation in interacting galaxies

Super star clusters and star-formation in interacting galaxies. Zara RANDRIAMANAKOTO. Supervisors : Petri Vaisanen (SAAO) ‏ Sarah Blyth (UCT) ‏. SA SKA Annual Bursary Conference December, 2009. Objectives.

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Super star clusters and star-formation in interacting galaxies

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  1. Super star clusters and star-formation in interacting galaxies Zara RANDRIAMANAKOTO Supervisors: Petri Vaisanen (SAAO)‏ Sarah Blyth (UCT)‏ SA SKA Annual Bursary Conference December, 2009

  2. Objectives • Derive the first ever significant sample of K-band luminosity • functions (LFs) of extragalactic super star clusters (SSCs)‏ • Estimate star formation rate (SFR) in interacting luminous infrared galaxies (LIRGs) from a study of SSCs LFs • Establish a spatial distribution of star formation (SF)‏ • over the whole galaxy 2

  3. Relevances of the project Key science in Astronomy: Understand the Universe 3

  4. Relevances of the project Galaxy evolution (LIRGs)‏ 4

  5. Relevances of the project SF via SSCs 5

  6. Why LIRGs ? LIRGs • Generally, an interacting system • High SFR • Large number of SSCs • Good laboratory for probing galaxy evolution and SF Elmegreen et al., 2006, ApJ 642, 158 6

  7. Why SSCs ? • Characteristics: SSCs • Massive • Young • Luminous Whitmore et al., 2000; Elmegreen, 2002 • Location: Found whenever there is vigorous SF such as interacting LIRGs (Whitmore et al., 2000)‏ 7

  8. Why SSCs ? • Characteristics: SSCs • Massive • Young • Luminous Whitmore et al., 2000; Elmegreen, 2002 • Location: Found whenever there is vigorous SF such as interacting LIRGs (Whitmore et al., 2000)‏ SSCs provide insight to the mechanisms of SF 8

  9. Challenges: • SSCs are located in the obscured optical region of the galaxies • It is difficult to differentiate individual SSCs to its surrounding dusty regions 9

  10. Challenges: • SSCs are located in the obscured optical region of the galaxies • It is difficult to differentiate individual SSCs to its surrounding dusty regions Solution: Observe in K-band using near infrared adaptive optics imaging K-band : observation suffers less of the dust effect AO : will resolve individual SSCs to large distances than before (a small field with high resolution) 10

  11. Solution: Observe in K-band using NIR adaptive optics imaging HST/ACS VLT/NACO 2” 4.5” A region of IRAS 18293-3413, close to the nucleus ( Vaisanen et al., 2009). 11

  12. Solution: Observe in K-band using NIR adaptive optics imaging HST/ACS VLT/NACO 2” 4.5” A region of IRAS 18293-3413, close to the nucleus ( Vaisanen et al., 2009). 12

  13. Methodology Data reduction of a ten local LIRGs from VLT/NACO and GEMINI/ALTAIR (using K-band NIR AO, survey in progress)‏ Imaging archival data for optical (HST/ACS)‏ mid- and far-infrared(MIPS and IRAC) radio (VLA) wavelengths SSCs LFs Multi-wavelength observations SFR Spatial distribution of SF 13

  14. Achievements GEMINI/ALTAIR Individual frames Data reduction (IRAF)‏ Final combined image 14

  15. MCG +08-11-002 IRAS F16516-0948 IC 694 Gemini co-added images NGC 3690 IRAS F17578-0400 15 CGCG 049-057 IRAS F17138-1017 UGC 8387

  16. Achievements GEMINI/ALTAIR Individual frames Data reduction (IRAF)‏ • Photometry calibration • Mag_zeropoint • Aperture correction Astrometry calibration (IRAF)‏ Final combined image Objects detection (Sextractor)‏ Aperture photometry (IRAF)‏ SSCs LFs 16 Selection criteria

  17. Preliminary results K-band SSCs LFs 17

  18. Preliminary results K-band SSCs LFs • LFs exhibit a turnover at the faint end: • Observational incompleteness (Anders et al., 2007)‏ • Small number of SSCs with lower luminosity 18

  19. Preliminary results K-band SSCs LFs • LFs exhibit a turnover at the faint end: • Observational incompleteness (Anders et al., 2007)‏ • Small number of SSCs with lower luminosity Solution: Use Monte-Carlo simulation to determine the completeness fraction 19

  20. Preliminary results K-band SSCs LFs Theoretical observations: LFs shape follow a power-law distribution (de Grijs et al., 2003)‏ 20

  21. Preliminary results K-band SSCs LFs • Slope slightly deviates from 2 • Effect from photometric uncertainties or some statistical fluctuations • It can be real (the goal of the project)‏ 21

  22. Preliminary results K-band SSCs LFs • Slope slightly deviates from 2 • Effect from photometric uncertainties or some statistical fluctuations • It can be real (the goal of the project)‏ • SSCs LFs systematic variations: • Steeper at higher luminosities (Whitmore et al., 1999; Larsen, 2002)‏ • Steeper in redder filters (Elmegreen et al., 2002; Haas et al., 2008)‏ 22

  23. Preliminary results K-band SSCs LFs: shift of the peak Larsen, 2002; Bastian, 2008 The fainter the brightest star cluster, the lower its SFR 23

  24. Preliminary results K-band SSCs LFs: shift of the peak Larsen, 2002; Bastian, 2008 The fainter the brightest star cluster, the lower its SFR 24 Expect that

  25. Future outlook Data reduction of a ten local LIRGs from VLT/NACO and GEMINI/ALTAIR (using K-band NIR AO, survey in progress)‏ Imaging archival data for optical (HST/ACS)‏ mid- and far-infrared(MIPS and IRAC) radio (VLA) wavelengths SSCs LFs Multi-wavelength observations SFR Spatial distribution of SF 25

  26. Future outlook Data reduction of a ten local LIRGs from VLT/NACO and GEMINI/ALTAIR (using K-band NIR AO, survey in progress)‏ Imaging archival data for optical (HST/ACS)‏ mid- and far-infrared(MIPS and IRAC) radio (VLA) wavelengths SSCs LFs GMRT/ATCA observations Multi-wavelength observations SFR Spatial distribution of SF 26

  27. Expectations • Reason of the turnover in LF at the faint end • In the local Universe, only a small fraction of the global SF • density is contributed by LIRGs. However, at higher redshift, • the fraction becomes dominant (Iono et al., 2009). 27

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