AN UNUSUAL T TAURI ABUNDANCE IN THE SOUTHERN HIGH MASS STAR FORMING REGION RCW 34
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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. CONTENTS. Star-formation T Tauri star? Results: Colour-colour diagram Two-point correlation analysis

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AN UNUSUAL T TAURI ABUNDANCE IN THE SOUTHERN HIGH MASS STAR FORMING REGION RCW 34

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An unusual t tauri abundance in the southern high mass star forming region rcw 34

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


An unusual t tauri abundance in the southern high mass star forming region rcw 34

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


  • An unusual t tauri abundance in the southern high mass star forming region rcw 34

    T Tauri Pre-main sequence star

    Pre-stellar core

    Molecular cloud

    Infrared protostar

    STAR FORMATION


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    CLASS 0:

    Main accretion phase

    Age 104 yr

    M  0.5 Mo

    CLASS I:

    Late accretion phase

    Age ~105 yr

    M  0.1 Mo

    CLASS II:

    Optically thick disk

    Age ~106 yr

    Mdisk  0.01 Mo

    STAR FORMATION


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    T TAURI STAR?

    • PMS stars near Molecular Clouds

    • < 2 Mo; 1-4 Myr

    • RTTauri > RMS 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)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-colour diagram

    • “Clustering”

    • 10 < Av < 15

    • Not MS – too massive

    • CTT locus  lower boundary


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-colour diagram


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-colour diagram

    • 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


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-point correlation analysis

    Definition:

    Two-point correlation function (r12): the probability that points appear in each of the volume elements dV1 and dV2 at separation r12,

    • Poisson process:  = 0

    • Significant clustering:  > 0

    Numerical formula:

    9Peebles (1976)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-point correlation analysis

    • Significant clustering until 260 pixels (~ 2’)

    • Clustering shows for T Tauri’s too  spatial correlation


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-point correlation analysis

    • As for galaxies, with highly non-linear clustering:

    • TPCF ~ declining power-law for Taurus-Auriga (Gomez et al., 1993)

    • (r0 = 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)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Two-point correlation analysis

    • Twice-broken power- law for Taurus1

    • 2 of the 3 parts seen for RCW 34

    • Correspondence between slopes & transitions (knees)

    • 2nd “knee”: between random distribution of ass. members  primordial structure

    • 2nd knee  indicate Jeans length for ~1Mo core formation2  agree with T Tauri distribution

    1 Krauss & Hillenbrand (2008), 2Larson (1995)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Colour-Magnitude diagram

    • Similar to HR-diagram. Verify

    • T Tauri location.


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Colour-Magnitude diagram

    • Reddening too much for MS – must be PMO’s

    • T Tauri’s located where expected: M* < 2Mo


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: Color-Cut

    • No control fields observed – needed for KLF.

    • Different method: colorcut4

    • Take all stars bluer than a combined isochrone as a statistical “control field”

    3 Harayama (2008)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    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)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RESULTS: KLF and age

    • NGC 2264 ~ 5 Myr4 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 core5,6.

    • 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), 5Herbig (1998), 6Luhman (1998)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    CONCLUSIONS

    • Two different stages of star formation in RCW 34:

    • 1st 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

    • 2nd stage:

    • H II region appears to be part of the remaining core of the larger MC

    • star formation was triggered a 2nd 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.


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    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.


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    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 mJy7.

    7Mamajek et al. (1996)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    THANK YOU!

    Ps. 147:4

    “He determines and counts the number of the stars;

    He calls them all by their names”


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    RCW 34

    (G264.29+1.47)

    • Cometary shaped H II region3 kpc in the region of Vela R2 with AV = 4.2 mag1.

    • Ionization front with bright point source: 12th mag PMS O-starL = 5 x 105 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)


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    10 ditherings

    of telescope

    METHOD

    DATA REDUCTION

    SIRIUS pipeline


    An unusual t tauri abundance in the southern high mass star forming region rcw 34

    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 Mo) PMS 2.5 Myr MS

    • Take all stars bluer than isochrone as “control field”


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