J/A+A/602/A56 R136 JKs photometry from VLT/SPHERE EAO (Khorrami+, 2017)
Uncrowding R 136 from VLT/SPHERE extreme adaptive optics.
Khorrami Z., Vakili F., Lanz T., Langlois M., Lagadec E., Meyer M.R.,
Robbe-Dubois S., Abe L., Avenhaus H., Beuzit J.L., Gratton R.,
Mouillet D., Origne A., Petit C., Ramos J.
<Astron. Astrophys. 602, A56 (2017)>
=2017A&A...602A..56K 2017A&A...602A..56K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Photometry, infrared
Keywords: open clusters and associations: individual: RMC 136 -
stars: luminosity function, mass function - stars: massive -
instrumentation: adaptive optics
Abstract:
This paper presents the sharpest near-IR images of the massive cluster
R 136 to date, based on the extreme adaptive optics of the SPHERE
focal instrument implemented on the ESO Very Large Telescope and
operated in its IRDIS imaging mode.
The crowded stellar population in the core of the R 136 starburst
compact cluster remains still to be characterized in terms of
individual luminosities, age, mass and multiplicity. SPHERE/VLT and
its high contrast imaging possibilities open new windows to make
progress on these questions.
Stacking-up a few hundreds of short exposures in J and Ks spectral
bands over a Field of View (FoV) of 10.9"x12.3" centered on the
R136a1 stellar component, enabled us to carry a refined photometric
analysis of the core of R136. We detected 1110 and 1059 sources in J
and Ks images respectively with 818 common sources. Thanks to better
angular resolution and dynamic range for 818 common sources being
detected, we found that more than 62.6% (16.5%) of the stars, detected
both in J and Ks data, have neighbours closer than 0.2" (0.1"). The
closest stars are resolved down to the full width at half maximum
(FWHM) of the point spread function (PSF) measured by Starfinder.
Among newly resolved and/or detected sources R136a1 and R136c are
found to have optical companions and R136a3 is resolved as two stars
(PSF fitting) separated by 59±2mas. This new companion of R136a3
presents a correlation coefficient of 86% in J and 75% in Ks. The new
set of detected sources were used to re-assess the age and extinction
of R 136 based on 54 spectroscopically stars that have been recently
studied with HST slit-spectroscopy (Crowther et al.,
2016MNRAS.458..624C 2016MNRAS.458..624C) of the core of this cluster.
Over 90% of these 54 sources identified visual companions (closer than
0.2"). We found the most probable age and extinction for these sources
are 1.8+1.2-0.8Myr, AJ=(0.45±0.5)mag and AK=(0.2±0.5)
mag within the photometric and spectroscopic error-bars. Additionally,
using PARSEC evolutionary isochrones and tracks, we estimated the
stellar mass range for each detected source (common in J and K data)
and plotted the generalized histogram of mass (MF with error-bars).
Using SPHERE data, we have gone one step further and partially
resolved and studied the IMF covering mass range of (3-300)M☉
at the age of 1 and 1.5Myr. The density in the core of R 136
(0.1-1.4pc) is estimated and extrapolated in 3D and larger radii (up
to 6pc). We show that the stars in the core are still unresolved due
to crowding, and the results we obtained are upper limits. Higher
angular resolution is mandatory to overcome these difficulties.
Description:
The SPHERE/IRDIS catalog of the common sources between J and Ks-band
data on R136. The ID, Xpix and Ypix are the identification and pixel
position in the IRDIS K and J image. σK and σJ are the
total error (combination of PSF-fitting error, residual errors and the
calibration error) in Ks and J images. CK and CJ are the Correlation
coefficients between the input PSF and the star, in Ks and J data.
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------------
05 38 42.40 -69 06 03.4 R136 = RMC 136
05 38 42.43 -69 06 02.2 R136a1 = RMC 136a1
-----------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 69 818 List of detected common sources between J and Ks
IRDIS images
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See also:
J/AJ/113/1691 : Stars in R136 (Hunter+ 1997)
J/AJ/131/2164 : X-ray sources in RMC 136 (Townsley+, 2006)
J/ApJ/448/179 : HST photometry in R136 (Hunter+ 1995)
J/ApJ/466/254 : NIR Imaging of R136 in 30 Dor (Brandl+ 1996)
J/ApJ/707/1347 : HST F160W photometry in RMC 136 (Andersen+, 2009)
J/ApJ/746/15 : Runaway massive stars from R136 (Banerjee+, 2012)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- SeqKs Sequential number of the source in Ks
6- 11 F6.2 pix XpixKs X pixel position in Ks (1)
13- 18 F6.2 pix YpixKs ?=- Y pixel position in Ks (1)
20- 24 F5.2 mag Ksmag Ks magnitude
26- 29 F4.2 mag e_Ksmag Total error on Ksmag (3)
31- 34 F4.2 --- Kscorr Ks Correlation coefficient between the
input PSF and the star
36- 39 I4 --- SeqJ Sequential number of the source in J
41- 46 F6.2 pix XpixJ X pixel position in J (2)
48- 53 F6.2 pix YpixJ ?=- Y pixel position in J (2)
55- 59 F5.2 mag Jmag J magnitude
61- 64 F4.2 mag e_Jmag Total error on Jmag (3)
66- 69 F4.2 --- Jcorr J Correlation coefficient between the
input PSF and the star
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Note (1): The position of detected stellar sources in IRDIS-Ks-Pixel in Fig. 1
bottom-right of the paper.
R136a1 has [478.27, 522.47] position in Ks IRDIS data
Note (2): The position of detected stellar sources in IRDIS-J-Pixel in Fig. 1
bottom-left of the paper.
R136a1 has [478.12, 522.39] position in J IRDIS data
Note (3): combination of PSF-fitting error, residual errors and the
calibration error.
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Acknowledgements:
Zeinab Khorrami, khorramiz(at)cardiff.ac.uk
(End) Patricia Vannier [CDS] 08-Mar-2017