Hugues Sana


NWO postdoc @ Amsterdam University


A MAD view of Trumpler 14

H. Sana, Y. Momany, M. Gieles, G. Carraro, Y. Beletsky, V.D. Ivanov, G. De Silva, G. James


Abstract

We present adaptive optics (AO) near-infrared observations of the Tr 14 cluster in the Carina region obtained using the ESO multi-conjugate AO demonstrator, MAD. Our campaign yields AO-corrected observations with an image quality of about 0.2" across the 2' field of view, which is the widest AO campaign towards a young open cluster. We detected about 2000 sources spanning a dynamic range of 10 mag. The pre-main sequence (PMS) locus in the colour-magnitude diagram is well reproduced by Palla & Stahler isochrones with an age of 3 to 5x105 yr, confirming the very young age of the cluster. We derive a very high (deprojected) central density n0~4x104 pc-3 and we estimate the mass in the cluster core to be about 4x103 Msun, although contamination of the field of view might significantly contribute to the mass. We show that the pairing process is largely dominated by chance alignment so that physical pairs are difficult to disentangle from spurious ones based on our single epoch observation. Yet, we identify 150 likely bound pairs, 30% of these with a separation smaller than 0.5". We further show that, at the 2 sigma level, massive stars have more solar-mass companions than solar-mass PMS stars and that those companions are brighter on average, thus more massive. Finally, we find some hints of mass segregation for stars heavier than about 10 Msun. If confirmed, the observed degree of mass segregation could be explained by dynamical evolution, despite the young age of the cluster.



Highlights


Images



Tr14 MAD image
False colour image of the 2' field of view of the MAD observations (blue  is H band; red, Ks band).   North is to the top and East, to the left.

FWHM map
Average FWHM map computed over the full field of view. The x-axis is inverted compare to the left-hand image.
PSF view
Close-up view of the Ks image around selected massive stars. The image size is 200x200 pixels, corresponding to approximately 5.5"x5.5" on the sky.
Close pairs in Tr14
Close-up view, in the Ks band, of the four closest pairs detected. The displayed regions are 6"x6" and the separations are all in the range 0.24-0.30". The measured positions of the sources in the field have been  overlaid.

Color-magnitude diagram (CMD)


Left:  Tr14 CMD for #1 (see paper). Middle: CMD for DP #4.  Right: complete Tr 14 CMD (DP#1 to 4). The red plain lines show the main sequence from Le Jeune & Schaerer (M>6 Msun) and from Palla & Staller (M<6 Msun) respectively. Symbols indicate, from top to bottom, masses of 120, 70, 40, 20, 10, 6, 4, 2, 1, 0.6 and 0.2 Msun. The green line give the log(age/yr)=5.5 PMS isochrone from Palla & Staller for objects down to 0.1 Msun. Symbols indicate masses of 2.6, 0.6, 0.2 and 0.1 Msun.
Tr14 color-magnitude diagram


Companion distribution functions


Magnitude distribution functions
Average number of companions per star as a function of the companion brightness.  The central stars are taken in four ranges as indicated in the upper left-hand legend. A moving average with a 2mag bin has been used and the considered separation range is 0.5-2.5". The various envelopes give the 1sigma serror bars.
Companion cumulative distribution functions
Left: Average number of companions per star for a given maximum companion magnitude. Right: Cumulative distribution functions (CDF) of the companion brightness.  The central stars are taken in four ranges as indicated in the upper left-hand legend. Only pairs with separations in the range 0.5-2.5" have been considered.

ESO Press release ; Dowload full paper @ arXiv:1003.2208