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

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

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

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

5. 5 SF via SSCs SF via SSCs Relevances of the project

6. 6 LIRGs Why 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

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

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

9. 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

10. 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 Solution: Observe in K-band using near infrared adaptive optics imaging 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) (a small field with high resolution)

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

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

13. 13 Methodology SSCs LFs Multi-wavelength observations 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 Spatial distribution of SF SFR

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

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

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

17. 17 Preliminary results K-band SSCs LFs

18. 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

19. 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: Solution: Use Monte-Carlo simulation to determine the completeness fraction

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

21. 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)‏

22. 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)‏

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

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

25. 25 SSCs LFs Multi-wavelength observations 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 Spatial distribution of SF SFR Future outlook

26. 26 SSCs LFs Multi-wavelength observations 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 Spatial distribution of SF SFR Future outlook GMRT/ATCA observations

27. 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).