an unusual t tauri abundance in the southern high mass star forming region rcw 34
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
AN UNUSUAL T TAURI ABUNDANCE IN THE SOUTHERN HIGH MASS STAR FORMING REGION
RCW 34Lientjie 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 Colour-magnitude diagram Colour Cut K-band luminosity function
Conclusions
Future prospects & Relavance to Meerkat
STAR FORMATION
Molecular cloud
Pre-stellar core
Infrared protostar
T Tauri Pre-main
sequence star
STAR FORMATION
CLASS 0:Main accretion phase
Age 104 yrM 0.5 Mo
CLASS I:Late accretion phase
Age ~105 yrM 0.1 Mo
CLASS II:Optically thick disk
Age ~106 yrMdisk 0.01 Mo
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)
RESULTS: Two-colour diagram
“Clustering”
10 < Av < 15
Not MS – too massive
CTT locus lower boundary
RESULTS: Two-colour diagram
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
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
9Peebles (1976)
Numerical formula:
RESULTS: Two-point correlation analysis
Significant clustering until 260 pixels (~ 2’)
Clustering shows for T Tauri’s too spatial correlation
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)
0
( )r
rr
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
TAURUS RCW 34
SLOPE – INTERM.
0.12 -0.95
SLOPE – LARGE 0.10 -0.84
2nd KNEE 0.18 pc 0.26 pc
1 Krauss & Hillenbrand (2008), 2Larson (1995)
RESULTS: Colour-Magnitude diagram
Similar to HR-diagram. Verify T Tauri location.
RESULTS: Colour-Magnitude diagram
Reddening too much for MS – must be PMO’s
T Tauri’s located where expected: M* < 2Mo
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)
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)
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)
CONCLUSIONSTwo 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.
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.
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)
THANK YOU!
Ps. 147:4
“He determines and counts the number of the stars;
He calls them all by their names”
RCW 34 (G264.29+1.47)
Ionization front with bright point source: 12th mag PMS O-star L = 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)
Cometary shaped H II region
3 kpc in the region of Vela R2 with AV = 4.2 mag1.
METHOD
DATA REDUCTION
SIRIUS pipeline
10 ditherings of telescope
RESULTSCMD - 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”