1. AN UNUSUAL T TAURI ABUNDANCE IN THE SOUTHERN HIGH MASS STAR FORMING REGION RCW 34 Lientjie de Villiers M.Sc. PROJECT SUPERVISOR: Prof. D.J. van der Walt

2. CONTENTS Star-formation T Tauri star? Results: Colour-colour diagram Two-point correlation analysis Colour-magnitude diagram Colour Cut K-band luminosity function Conclusions Future prospects & Relavance to Meerkat

3. STAR FORMATION Molecular cloud Pre-stellar core Infrared protostar T Tauri  Pre-main sequence star

4. STAR FORMATION CLASS 0: Main accretion phase Age  10 4 yr M  0.5 M o CLASS I: Late accretion phase Age ~10 5 yr M  0.1 M o CLASS II: Optically thick disk Age ~10 6 yr M disk  0.01 M o

5. T TAURI STAR? PMS stars near Molecular Clouds < 2 M o ; 1-4 Myr R TTauri > R MS for same mass  more luminous No H-fusion; Powered by gravitational energy Accretion  Optical & UV excess emission IR excess  circumstellar disk Magnetic field  starspots & excess X-ray & Radio emission Hartmann (1998); Appenzeller & Mundt (1989)

6. RESULTS: Two-colour diagram “Clustering” 10 < A v < 15 Not MS – too massive CTT locus  lower boundary

7. RESULTS: Two-colour diagram

8. Appears to be T Tauri stars on 2CD BUT background stars on coordinate plot. VERIFY!! Two-point correlation function Colour-magnitude diagram Slope of KLF

9. RESULTS: Two-point correlation analysis Definition: Two-point correlation function  (r 1 2): the probability that points appear in each of the volume elements dV 1 and dV 2 at separation r 12, Poisson process:  = 0 Significant clustering:  > 0 9 Peebles (1976) Numerical formula:

10. RESULTS: Two-point correlation analysis Significant clustering until 260 pixels (~ 2’) Clustering shows for T Tauri’s too  spatial correlation

11. RESULTS: Two-point correlation analysis As for galaxies, with highly non-linear clustering: TPCF ~ declining power-law for Taurus-Auriga (Gomez et al., 1993) (r 0 = correlation length). Fitted a power-law on TPCF of RCW 34 too. (5 pix binning i.s.o. 20 pix  reveal trends on small scales)

12. RESULTS: Two-point correlation analysis Twice-broken power- law for Taurus 1 2 of the 3 parts seen for RCW 34 Correspondence between slopes & transitions (knees) 2 nd “knee”: between random distribution of ass. members  primordial structure 2 nd knee  indicate Jeans length for ~1M o core formation 2  agree with T Tauri distribution TAURUSRCW 34 SLOPE – INTERM. 0.12-0.95 SLOPE – LARGE0.10-0.84 2 nd KNEE0.18 pc0.26 pc 1 Krauss & Hillenbrand (2008), 2 Larson (1995)

13. RESULTS: Colour-Magnitude diagram Similar to HR-diagram. Verify T Tauri location.

14. RESULTS: Colour-Magnitude diagram Reddening too much for MS – must be PMO’s T Tauri’s located where expected: M * < 2M o

15. RESULTS: Color-Cut No control fields observed – needed for KLF. Different method: colorcut 4 Take all stars bluer than a combined isochrone as a statistical “control field” 3 Harayama (2008)

16. RESULTS: K-band Luminosity Function KLF is given by Slope of logarithmic KLF for RCW 34:  = 0.31 About 50% of the members of the young cluster NGC 2264 are CTTs. KLF slope of NGC 2264 is 0.32 ± 0.04 Relation between CTT abundance and  ? Need Spec. 4 Lada et al. (1993)

17. RESULTS: KLF and age NGC 2264 ~ 5 Myr 4  serve as an estimate for the age of RCW 34, providing the apparent similar stellar populations in both clusters. IC 348, showed a population of emission-line stars, with an age representing a star formation duration of 3Myr, centered on the cluster core 5,6. Herbig (1998) suggested that this very young cluster is superimposed on a more broadly distributed non- emission-line population that permeates the region of IC 348, with an age representing star formation of 1 − 10 Myr ago. 4 Lada et al. (1993), 5 Herbig (1998), 6 Luhman (1998)

18. CONCLUSIONS Two different stages of star formation in RCW 34: 1 st stage: originated from a surrounding MC with dimensions > image frame that lower mass star formation  the older population of T Tauri stars separated by Jeans length of dense cores. T Tauri ages are around 1 - 4 Myr  parts of the cloud had already been destroyed  leave the T Tauri’s exposed 2 nd stage: H II region appears to be part of the remaining core of the larger MC star formation was triggered a 2 nd time at a later stage  formation of the central young massive star shock formed by this exciting, high mass star  trigger for on-going star formation at the ionization front young stars  sources that show a NIR excess on the 2CD. It appears as if star formation in RCW 34 is not coeval.

19. FUTURE PROSPECTS Confirm results with: Spectroscopy. Surrounding fields obtained from sky surveys (2MASS / VISTA?(deeper)): are cluster borders detected? Analyze optical data  multi wavelength info on RCW 34. Construct IMF – number of low mass stars expected? Collaboration with Dr. Lucas – use Synthetic Besançon Stellar Population Models to model this field. Preliminary result: T Tauri cluster on 2CD is indeed due to a mixture of cluster members and field dwarfs.

20. RELEVANCE TO MEERKAT Confirm the nature of the possible T Tauri stars with the deeper survey of MeerKAT. Radio-mapping of RCW 34’s molecular cloud  obtain its real shape and dimensions? With better angular- & spatial resolution of SKA  distinguish between binary & multiple systems at small spatial scales – fill in the missing first part of TPCF power law. ROSAT discovered 91 T Tauri stars in the vicinity of the Taurus- Auriga star-forming region. 17-29 of them were also detected by an 8.4 GHz VLA survey with a sensitivity limit of ~ 0.15 mJy 7. 7 Mamajek et al. (1996)

21. THANK YOU! Ps. 147:4 “He determines and counts the number of the stars; He calls them all by their names”

23. RCW 34 (G264.29+1.47) Ionization front with bright point source: 12 th mag PMS O-star L = 5 x 10 5 L  and R  23 R  2. Large IR excess  dust around exciting star. 1 Deharveng et al. (2005) & Heydari-Malayeri (1988); 2 Vittone et. Al. (1987) Cometary shaped H II region 3 kpc in the region of Vela R2 with A V = 4.2 mag 1.

24. METHOD DATA REDUCTION SIRIUS pipeline 10 ditherings of telescope

25. RESULTS CMD - COLORCUT No control fields – needed for KLF. Different method: colorcut (Harayama, 2008) Combined isochrone: smooth turnover points between: 0.7 Myr PMS 1 Myr low-mass (1.2 M o ) PMS 2.5 Myr MS Take all stars bluer than isochrone as “control field”