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A NEAR-INFRARED STUDY OF THE SOUTHERN STAR FORMING REGION RCW 34 Lientjie de Villiers M.Sc. PROJECT SUPERVISOR: Prof. D.J. van der Walt CONTENTS Star-formation The region RCW 34 M.Sc. Objectives Method Preliminary results Future objectives Relevance to SKA STAR-FORMATION From the Virial theorem, if U 2K gravitational collapse of molecular cloud. From above the Jeans criterion can be derived as M c M J where the Jeans mass MJ is given by the RHS of 3 2 5kT 3 Mc G mH 40 Molecular cloud T Tauri Pre-main sequence star 1 2 (1). Pre-stellar core Infrared protostar RCW 34 ~ 3 kpc L = 5 x 105 L and R 23 R. Cometary shaped H II region. Bright point source in front of ionization front. Large IR excess dust around exciting star. Near-IR observations star formation at border of ionization front (Zavagno et al.) Source OBJECTIVES Study stars associated with high mass star in NIR Ks band (extinction less at 2.2 m) Stack images Long integration times obtain deep (~18th –19th mag) JHKs images sub-solar – solar mass stars. Error vs magnitude graphs (reliability of data) Magnitude distribution histograms 2-Color diagram, dereddening 2-point correlation analysis of spatial clustering Ks luminosity function (KLF) Initial Mass Function (IMF) METHOD OBSERVATIONS & DATA REDUCTION JHKs-bands on 1.4 m IRSF. 30s exposure Reduction with the SIRIUS pipeline in IRAF (Image Reduction & Analysis facility) Stacked images ~ 60min integration times. METHOD SELECTION OF STARS Crowded field Initially: Source Extractor Problem: fixed apertures in crowded field – wrong photometry. Solution 1: Aperture corrected photometry – no optimal aperture radius (graph of mag. vs. aperture radius) Solution 2: PSF photometry: In IRAF Perform PSF fitting photometry using ALLSTAR Extract stars with DAOFIND in Daophot (5 detection) Compute PSF with PSF task, using 20 stars selected by PSTSELECT 18.500 J band METHOD Chart Title 18.000 y = 0.948x + 4.7947 R2 = 0.9967 17.500 IRSF magnitude 18.000 17.000 PHOTOMETRY Ks band 16.500 17.500 2 15.500 17.000 15.000 17.400 16.500 14.500 17.200 14.000 17.000 10.000 y = 0.9691x + 4.396 R2 = 0.9968 10.500 11.000 11.500 12.000 16.000 16.800 IRSF magnitude IRSF magnitude y = 1.0299x + 4.7561 Calibrate by subtracting R = 0.9973 Used 2MASS (2 Micron All Sky Stacked all images ofthe one night obtained constant Survey) all-sky point source no specific airmass need Avg: 4.121 catalog 40 of brightest stars from magnitudes of different calibration method H-band Stddev: 0.066 with coordinates corresponding than standard stars all IRSF stars with results of Daofind found by Daofind Apparent magnitude. 16.000 12.500 13.000 13.500 14.000 14.500 2MASS magnitude 16.600 Avg: 5.102 Stddev: 0.035 Get average offset between 16.400 15.500 16.200 EXTREMELY close linear 15.000correlation between 10.000 10.500 2MASS and IRSF 11.000 magnitudes – confirmed by a very small standard deviation on the offsets. 16.000 15.800 15.600 15.400 15.200 11.000 11.500 2MASS and IRSF for each of the 12.000 12.500 13.000 Avg: 4.010 standard 40 stars & calculate 2MASS magnitude Stddev: 0.036 deviation. 11.500 12.000 12.500 2MASS magnitude 13.000 13.500 PRELIMINARY RESULTS RELIABILITY OF DATA Relative error for N counts = N 1 N N Therefore as N , the relative error Magnitude = 2.5log N N thus Trend of relative error in counts v.s. counts 1 N Error on magnitude 1.2 Plot of magnitude-error vs magnitude inverse x-axis (minus sign). 1 1 N vs. N with 1/sqrt(N) 0.8 0.6 0.4 0.2 0 0 50 100 150 N counts 200 250 300 PRELIMINARY RESULTS RELIABILITY OF DATA J-BAND PRELIMINARY RESULTS RELIABILITY OF DATA H-BAND PRELIMINARY RESULTS RELIABILITY OF DATA Ks-BAND PRELIMINARY RESULTS APPARENT MAGNITUDE DISTRIBUTIONS Out of deep images & with the detection 20 of stars on 5 level Succeeded to detected very faint (low mass) stars 18.0 20.0 PRELIMINARY RESULTS APPARENT MAGNITUDE DISTRIBUTIONS 17.0 19.5 PRELIMINARY RESULTS APPARENT MAGNITUDE DISTRIBUTIONS 17.0 18.5 PRELIMINARY RESULTS INTERSTELLAR REDDENING Difference in magnitude due to dust: m(0) = m - A (1) Reddening law (difference in intrinsic color due to reddening) E(J - H) = 0.107Av (2) [J - H] = [J – H]0 + 0.107 AV Rieke & Lebofsky E(H - K) = 0.063Av [H - K] = [H – K]0 + 0.063 AV (3) Slope of reddening lines: E(J-H) / E(H-K) PRELIMINARY RESULTS TWO-COLOR DIAGRAMS MS & Giant branches from Koorneef. T Tauri Locus (Meyer et. Al) Reddening: || to reddening vector (T Tauri due to disk) Suggestions: 5 Av • Maybe some stars are real: MS not infinitely narrow; Lada et al. (1993) found ~50% 20% of cluster shows NIR excess. Left – photometric err. • New calibration constant for 5 detection level. Problem: • Remove “bad-pixels” detected as “faint stars” 5accuracy. vs 15 2CD • Investigate errors on color terms – indication of Tauri: (J-H) = 0.580.11 (H-K) + 0.52 0.06lengths from center. •T Two point correlation – field stars > 1-2 correlation PRELIMINARY RESULTS TWO-COLOR DIAGRAMS Infrared excess Embedded stars – accretion disk / dust shell FUTURE OBJECTIVES Investigate strange T Tauri clustering on 2CD. Determine location of T Tauri’s and IR excess stars on image (dusty regions ?). Two-point correlation. Characterize population of stars: KLS IMF RELEVANCE TO SKA YSO & T Tauris still embedded circumstellar matter radiate in IR – distinguish b.m.o. IR excess in 2CD Need to investigate star formation in IR at first to characterize population Expand to multi-wavelength Radio complements IR: Mapping Some stars with IR excess have hotspots of ~ 7000K can get information about their rotation. With better angular- & spatial resolution of SKA distinct between binary systems & stars currently indistinguishable get thermal radiation of individual T Tauris. THANK YOU!! Ps. 19:1 “The heavens declare the glory of God; And the firament shows His handiwork.” STAR-FORMATION Virial theorem: 2K U 0 (1) condition for stable, gravitationally bound system. If U 2K gravitational collapse of molecular cloud Gravitational potential energy: Kinetic energy (monatomic gas): Radius i.t.o. density: 3M c Rc 4 0 1 3 3 GM c2 Ug ~ 5 Rc (2) 3 K NkT 2 (3) (4) Ug, K and Rc into (1) with N M c / mH gives: ( = mean molecular weight) 40 3M c kT 3 GM c2 mH 5 3 M c 1 3 (5) RCW 34 Cometary shaped H II region G264.29+1.47 3.1 kpc Excited by O 9.5 Ib (O 8.5V) star (Vittone et al. & Heydari-Malayeri) L = 5 x 105 L and R 23 R. RCW 34 ~ 3 kpc L = 5 x 105 L and R 23 R. Cometary shaped H II region. Bright MSX & IRAS point source (O 9.5 Ib) in front of ionization front excites H II region. Molecular bar divided region into 3 regions: Dense, less dense & diffuse. Large IR excess dust around exciting star Near-IR observations star formation at border of ionization front (Zavagno et al.) Source RCW 34 Bright MSX (Midcourse Space Experiment) & IRAS point source in front of bright ionization front (Deharveng et al.). Large IR excess dust around exciting star Molecular bar divided into 3 regions: Source Dense, heated post shock Cold less dense besides Diffuse in front of dense parts (~102 per cm3 & 30-60K) Near-IR observations star formation at border of ionization front (Zavagno et al.) METHOD TELESCOPE 1.4 m Infrared telescope at Sutherland NIR camera SIRIUS Designed for deep & wide JHKs-bands simultaneous surveys (1.25, 1.65, 2.2 m). Images with 30s exposure time & total of 60 min integration time per night. METHOD DATA REDUCTION 10 ditherings of telescope PRELIMINARY RESULTS RELIABILITY OF DATA of relative errorNin counts Relative error for N Trend counts = N 1 v.s. counts 1.2 N Therefore as N , the relative error 1 Magnitude = 2.5log N N thus 1/sqrt(N) 0.8 0.6 Error on magnitude 0.4 1 N Plot of magnitude-error vs magnitude inverse x-axis (minus sign). 0.2 1 N vs. N with 0 0 50 100 150 200 250 300 N counts Got “weird” stars with high error value at bright magnitudes Extracted “weird” stars’ coordinates Plot on image Bad pixels / dust explanation PRELIMINARY RESULTS INTERSTELLAR REDDENING Difference in magnitude due to dust: m(0) = m - A (1) change in intrinsic color due to reddening: A1 A 2 m1 (0) m 2 (0) (m1 m 2 ) AV A A V V E(J – H) = 0.107Av Known ratio: Rieke & Lebofsky [J - H] = [J – H]0 + 0.107 [H - K] = [H – K]0 + 0.063 AV AV FUTURE OBJECTIVES Stellar clusters important in determination of IMF equidistant & co-eval populations of stars instantaneous sampling of IMF at different epochs in Galactic history.