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J/A+A/540/A57       Mass function of Quintuplet cluster      (Hussmann+, 2012)

The present-day mass function of the Quintuplet cluster based on proper motion membership. Hussmann B., Stolte A., Brandner W., Gennaro M., Liermann A. <Astron. Astrophys. 540, A57 (2012)> =2012A&A...540A..57H
ADC_Keywords: Clusters, open ; Stars, early-type ; Proper motions ; Photometry, infrared ; Stars, masses Keywords: Galaxy: center - open clusters and associations: individual: Quintuplet cluster - stars: early-type - infrared: stars - stars: luminosity function, mass function - stars: kinematics and dynamics Abstract: The stellar mass function is a probe for a potential dependence of star formation on the environment. Only a few young clusters are known to reside within the central molecular zone and can serve as test-beds for star formation under the extreme conditions in this region. We determine the present-day mass function of the Quintuplet cluster, a young massive cluster in the vicinity of the Galactic centre. We use two epochs of high resolution near infrared imaging data obtained with NAOS/CONICA at the ESO VLT to measure the individual proper motions of stars in the Quintuplet cluster in the cluster reference frame. An unbiased sample of cluster members within a radius of 0.5pc from the cluster centre was established based on their common motion with respect to the field and a subsequent colour-cut. Initial stellar masses were inferred from four isochrones covering ages from 3 to 5Myr and two sets of stellar evolution models. For each isochrone, the present-day mass function of stars was determined for the full sample of main sequence cluster members using an equal number binning scheme. We find the slope of the present-day mass function in the central part of the Quintuplet cluster to be alpha=-1.68+0.13-0.09 for an approximate mass range from 5 to 40M, which is significantly flatter than the Salpeter slope of alpha=-2.35. The flattening of the present-day mass function may be caused by rapid dynamical evolution of the cluster in the strong Galactic centre tidal field. The derived mass function slope is compared to the values found in other young massive clusters in the Galaxy. Description: All sources in this catalogue are located within a radius of 0.5pc from the centre of the observed field of view (near source No. 394). The table contains all sources with measured H-, and Ks-band magnitudes and proper motions, i.e. all sources which appear in the colour-magnitude- diagrams of cluster and field (Fig. 8). For stars with magnitudes above the linearity limits, i.e. Ks<11.3mag and H<12.0mag, the stated magnitude and proper motion errors might be underestimated. For each source the cluster membership was assessed based on 1.) its measured proper motion, 2.) its colour and 3.) its spectral type (if contained in the K-band spectral catalogue of Liermann et al. (2009, Cat. J/A+A/494/1137). For designated cluster members initial masses have been determined from 3, 4, 5Myr Padova isochrones (Marigo et al. 2008A&A...482..883M) and a 4Myr Geneva isochrone with enhanced mass loss (Lejeune & Schaerer 2001, Cat. VI/102). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table4.dat 144 1221 Catalog of stars
See also: J/A+A/494/1137 : Quintuplet cluster K-band spectral catalog (Liermann+, 2009) Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 4 I4 --- Seq Sequential number 6- 10 F5.2 arcsec dRA Right ascension offset (1) 12- 16 F5.2 arcsec dDE Declination offset (1) 18- 22 F5.2 mag Ksmag NACO VLT/CONICA Ks band magnitude 24- 27 F4.2 mag e_Ksmag Uncertainty of the Ks band magnitude 29- 33 F5.2 mag Hmag NACO VLT/CONICA H band magnitude 35- 38 F4.2 mag e_Hmag Uncertainty of the H band magnitude 40- 43 F4.2 mag AKs ? Individual extinction (2) 45- 48 F4.2 --- Compl Individual combined completeness (3) 49- 54 F6.2 mas/yr pmRA Proper motion in RA*cos(DE) 56- 61 F6.2 mas/yr pmDE Proper motion in DE 63- 66 F4.2 mas/yr e_pmRA Uncertainty of pmRA 68- 71 F4.2 mas/yr e_pmDE Uncertainty of pmDE 73- 76 F4.2 mas/yr e_pm Uncertainty of the absolute proper motion 78- 79 A2 --- Seg Segment in the proper motion diagram (4) 81- 83 I3 --- LHO ? Identifier in the LHO catalogue (5) 84 A1 --- n_LHO [*] * for sources in the LHO catalogue which have more than one counterpart 87-103 A17 --- SpType MK spectral type from the LHO catalogue 105-107 A3 --- Mmb Cluster membership flag, 'y' for member (6) 109-113 F5.2 Msun MP3 ? Initial mass or interval (85-100M) derived from a 3Myr Padova isochrone (7) 114 A1 --- --- [-] 115-117 I3 Msun MP3u ? Upper value when interval (8) 119-123 F5.2 Msun MP4 ? Initial mass or interval (51-65M) derived from a 4Myr Padova Isochrone (7) 124 A1 --- --- [-] 125-126 I2 Msun MP4u ? Upper value when interval (8) 128-132 F5.2 Msun MP5 ? Initial mass or interval (37-40M) derived from a 5Myr Padova isochrone (7) 133 A1 --- --- [-] 134-135 I2 Msun MP5u ? Upper value when interval (8) 137-141 F5.2 Msun MG4 ? Initial mass or interval (48-60M) derived from a 4Myr Geneva isochrone (7) 142 A1 --- --- [-] 143-144 I2 Msun MG4u ? Upper value when interval (8)
Note (1): Positions measured relative to Q2 (LHO 42) at 17:46:14.690-28:49:40.71 (J2000) Note (2): The extinction A_Ks for cluster members was determined by individual dereddening using the 4Myr Padova isochrone (Marigo, 2008A&A...482..883M) and the extinction law by Nishiyama et al. (2009ApJ...696.1407N). The individual extinction AKs are only derived for cluster members on the main-sequence of the respective isochrone. Note (3): Product of the completeness values of the Ks-band data, the H-band data (both from 2003) and the second epoch Ks-band data from 2008 determined at the position of each individual star Note (4): The proper motion diagram is split into two segments, the NE (north-east) and the SW (south-west) segment. As the cluster and field population overlap in the south-west segment of the proper motion diagram, the cluster members with proper motions residing in the north-east segment comprise the cleanest sample of cluster stars. Note (5): K-band spectral catalogue by Liermann et al. (2009, Cat. J/A+A/494/1137) Note (6): Cluster membership flag is: y = cluster member n = non-member according to the proper motion ncc = non-member according to the colour nst = non-member according to the spectral type (i.e. M,K supergiant are rejected) Note (7): The initial masses have been inferred adopting solar metallicity and a distance of 8kpc to the cluster (distance modulus 14.52). The initial masses are only derived for cluster members on the main-sequence of the respective isochrone. Note (8): For WR stars mass ranges instead of masses were inferred from the underlying stellar models of the respective isochrone (Bressan et al. 1993, Cat. J/A+AS/100/647) for the Padova isochrones, et al., Meynet et al. (1994, Cat. J/A+AS/103/97) and Schaller et al. (1992, Cat. J/A+AS/96/269) for the Geneva isochrone)
Acknowledgements: Benjamin Hussmann, hussmann(at) History: * 27-Mar-2012: on-line version * 28-Oct-2013: LHO cross-identification numbers corrected (from author)
(End) Benjamin Hussmann [Bonn Univ.], Patricia Vannier [CDS] 20-Feb-2012
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