J/AJ/145/46 UBVIc photometry in Westerlund 1 (Lim+, 2013)
The starburst cluster Westerlund 1: the initial mass function and mass
segregation.
Lim B., Chun M.-Y., Sung H., Park B.-G., Lee J.-J., Sohn S.T., Hur H.,
Bessell M.S.
<Astron. J., 145, 46 (2013)>
=2013AJ....145...46L 2013AJ....145...46L
ADC_Keywords: X-ray sources ; Clusters, open ; Photometry, UBVRI ;
Spectral types
Keywords: open clusters and associations: individual: Westerlund 1 -
stars: luminosity function, mass function
Abstract:
Westerlund 1 is the most important starburst cluster in the Galaxy due
to its massive star content. We have performed BVIC and JKS
photometry to investigate the initial mass function (IMF). By
comparing the observed color with the spectral-type-intrinsic-color
relation, we obtain the mean interstellar reddening of
<E(B-V)≥4.19±0.23 and <E(J-KS)≥1.70±0.21. Due to the heavy
extinction toward the cluster, the zero-age main sequence fitting
method based on optical photometry proved to be inappropriate for the
distance determination, while the near-infrared photometry gave a
reliable distance to the cluster, 3.8kpc from the empirical relation.
Using the recent theoretical stellar evolution models with rotation,
the age of the cluster is estimated to be 5.0±1.0Myr. We derived the
IMF in the massive part and obtained a fairly shallow slope of
Γ=-0.8±0.1. The integration of the IMF gave a total mass for
the cluster in excess of 5.0x104M☉. The IMF shows a clear
radial variation indicating the presence of mass segregation. We also
discuss the possible star formation history of Westerlund 1 from the
presence of red supergiants and relatively low luminosity yellow
hypergiants.
Description:
The observations of Westerlund 1 were carried out on 2009 March 28 at
the Cerro Tololo Inter-American Observatory (CTIO) in Chile. All the
images were taken with the Mosaic II CCD (36'*36') attached to the
Blanco 4m telescope. The seeing was about 0.8". Harris BVIC and
Sloan Digital Sky Survey (SDSS) u filters were used.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 132 27529 Photometric data in Westerlund 1
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See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2013)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
II/221 : The LF Survey (McCuskey+ 1949-1959)
J/A+A/477/147 : X-ray sources in Westerlund 1 (Clark+, 2008)
J/AJ/135/441 : VRIHα photometry in NGC 2264 (Sung+, 2008)
J/AJ/133/2696 : BVRI light curves of Westerlund 1 stars (Bonanos, 2007)
J/ApJ/646/269 : Multiwavelength analysis of NGC 2362 (Delgado+, 2006)
J/AJ/127/1014 : CCD UBVRIHa photometry in NGC 3603 (Sung+, 2004)
J/AJ/120/333 : UBVRI and Hα in NGC 6530 (Sung+, 2000)
J/MNRAS/310/982 : UBVI CCD Photometry of M11 - II. (Sung+ 1999)
J/MNRAS/306/361 : UBVI CCD photometry of M35 (NGC 2168) (Sung+ 1999)
J/A+AS/127/423 : VI photometry of Westerlund 1 and 2 (Piatti+ 1998)
J/AJ/115/734 : NGC 6231 UBVRI and Hα photometry (Sung+ 1998)
J/AJ/114/2644 : UBVRIHa photometry of NGC2264 (Sung+, 1997)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Star [-8/27521] Star running number
<[LCS2013] NNNNN> in Simbad (1)
7- 8 I2 h RAh Hour of Right Ascension (J2000)
10- 11 I2 min RAm Minute of Right Ascension (J2000)
13- 17 F5.2 s RAs Second of Right Ascension (J2000)
19 A1 --- DE- Sign of the Declination (J2000)
20- 21 I2 deg DEd Degree of Declination (J2000)
23- 24 I2 arcmin DEm Arcminute of Declination (J2000)
26- 29 F4.1 arcsec DEs Arcsecond of Declination (J2000)
31- 36 F6.3 mag Vmag [14.88/24.271]? The V-band (Harris) magnitude
38- 43 F6.3 mag Imag [9.776/22.564]? The Ic band (Harris) magnitude
45- 49 F5.3 mag V-I [0.191/8.378]? The (V-Ic) color index
51- 55 F5.3 mag B-V [0.077/5.053]? The (B-V) color index
57- 62 F6.3 mag U-B [-8.03/1.737]? The (U-B) color index
64- 68 F5.3 mag e_Vmag ? Uncertainty in Vmag
70- 74 F5.3 mag e_Imag ? Uncertainty in Imag
76- 80 F5.3 mag e_V-I ? Uncertainty in V-I
82- 86 F5.3 mag e_B-V ? Uncertainty in B-V
88- 92 F5.3 mag e_U-B ? Uncertainty in U-B
94 I1 --- o_Vmag Number of Vmag observations
96 I1 --- o_Imag Number of Imag observations
98 I1 --- o_V-I Number of V-I observations
100 I1 --- o_B-V Number of B-V observations
102 I1 --- o_U-B Number of U-B observations
104-119 A16 --- 2MASS The 2MASS identifier (HHMMSSss+DDMMSSs, J2000)
121 A1 --- X [X] X=X-ray emission star
123-132 A10 --- SpT MK Spectral type (2)
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Note (1): The negative numbered ID represents the calibrated data from
Clark et al. (2005A&A...434..949C 2005A&A...434..949C), Negueruela et al.
(2010A&A...516A..78N 2010A&A...516A..78N), Piatti et al. (1998, cat. J/A+AS/127/423).
Note (2): From Clark & Negueruela (2002A&A...396L..25C 2002A&A...396L..25C, 2004A&A...413L..15C 2004A&A...413L..15C),
Clark et al. (2005A&A...434..949C 2005A&A...434..949C),
Crowther et al. (2006MNRAS.372.1407C 2006MNRAS.372.1407C),
Mengel & Tacconi-Garman (2007A&A...466..151M 2007A&A...466..151M),
Negueruela et al. (2010A&A...516A..78N 2010A&A...516A..78N),
Clark et al. (2010A&A...514A..87C 2010A&A...514A..87C),
Dougherty et al. (2010A&A...511A..58D 2010A&A...511A..58D).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 24-Mar-2014