J/ApJ/789/115 The Quintuplet cluster astrometry and photometry (Stolte+, 2014)
The orbital motion of the Quintuplet cluster - A common origin for the Arches and Quintuplet clusters? Stolte A., Hussmann B., Morris M.R., Ghez A.M., Brandner W., Lu J.R., Clarkson W.I., Habibi M., Matthews K. <Astrophys. J., 789, 115 (2014)> =2014ApJ...789..115S (SIMBAD/NED BibCode)
ADC_Keywords: Positional data ; Photometry ; Milky Way ; Clusters, open Keywords: astrometry - Galaxy: center - Galaxy: kinematics and dynamics - open clusters and associations: individual (Quintuplet) - techniques: high angular resolution Abstract: We investigate the orbital motion of the Quintuplet cluster near the Galactic center with the aim of constraining formation scenarios of young, massive star clusters in nuclear environments. Three epochs of adaptive optics high-angular resolution imaging with the Keck/NIRC2 and Very Large Telescope/NAOS-CONICA systems were obtained over a time baseline of 5.8 yr, delivering an astrometric accuracy of 0.5-1 mas/yr. Proper motions were derived in the cluster reference frame and were used to distinguish cluster members from the majority of the dense field star population toward the inner bulge. Fitting the cluster and field proper motion distributions with two-dimensional (2D) Gaussian models, we derive the orbital motion of the cluster for the first time. The Quintuplet is moving with a 2D velocity of 132±15 km/s with respect to the field along the Galactic plane, which yields a three-dimensional orbital velocity of 167±15 km/s when combined with the previously known radial velocity. From a sample of 119 stars measured in three epochs, we derive an upper limit to the velocity dispersion of σ1D< 10 km/s in the core of the Quintuplet cluster. Knowledge of the three velocity components of the Quintuplet allows us to model the cluster orbit in the potential of the inner Galaxy. Under the assumption that the Quintuplet is located in the central 200 pc at the present time, these simulations exclude the possibility that the cluster is moving on a circular orbit. Comparing the Quintuplet's orbit with our earlier measurements of the Arches' orbit, we discuss the possibility that both clusters originated in the same area of the central molecular zone (CMZ). According to the model of Binney et al., two families of stable cloud orbits are located along the major and minor axes of the Galactic bar, named x1 and x2 orbits, respectively. The formation locus of these clusters is consistent with the outermost x2 orbit and might hint at cloud collisions at the transition region between the x1 and x2 orbital families located at the tip of the minor axis of the Galactic bar. The formation of young, massive star clusters in circumnuclear rings is discussed in the framework of the channeling in of dense gas by the bar potential. We conclude that the existence of a large-scale bar plays a major role in supporting ongoing star and cluster formation, not only in nearby spiral galaxies with circumnuclear rings, but also in the Milky Way's CMZ. Description: For the proper motion analysis of the central region of the Quintuplet, data from the ESO Very Large Telescope (VLT) taken in 2003 were combined with Keck observations obtained in 2008 and 2009. A second epoch of NACO observations obtained in 2008 July was used to constrain the two-dimensional (2D) cluster motion from a sample of stars at larger radii from the cluster center. All positions are approximately centered on the central Quintuplet star Q12 (Glass et al. 1990MNRAS.242p..55G) at RA 17:46:15.12, DE -28:49:35.06. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 17 46 15.12 -28 49 36.06 Quintuplet cluster = MGM 5 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 97 226 Astrometry & photometry of NACO 2003 & NIRC2 2008 & 2009 sources table4.dat 82 2137 Astrometry & photometry of NACO 2003 & NACO 2008 sources
See also: J/A+A/578/A4 : Photometry and motions in Arches and Quintuplet (Stolte+, 2015) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq Sequential number 5- 10 F6.3 arcsec dRA Right Ascension offset (J2000) (G1) 12- 17 F6.3 arcsec dDE Declination offset (J2000) (G1) 19- 25 F7.4 mas/yr pmRA Proper motion in RA; milliarcsec/yr 27- 32 F6.4 mas/yr e_pmRA Uncertainty in pmRA 34- 40 F7.4 mas/yr pmDE Proper motion in Declination; milliarcsec/yr 42- 47 F6.4 mas/yr e_pmDE Uncertainty in pmDE 49- 54 F6.3 mag Kmag09 The 2009 Keck/NIRC2 K' band magnitude (G2) 56- 60 F5.3 mag e_Kmag09 Uncertainty in Kmag09 62- 68 F7.3 mag Kmag08 ?=-99.99 The 2008 Keck/NIRC2 K' band magnitude (G2) 70- 76 F7.3 mag e_Kmag08 ?=-99.99 Uncertainty in Kmag08 78- 83 F6.3 mag Kmag03 The 2003 VLT/NAOS-CONICA Ks band magnitude (G2) 85- 89 F5.3 mag e_Kmag03 Uncertainty in Kmag03 91- 97 F7.3 --- pclus ?=-99.99 Membership probability indicator (3)
Note (3): For stars deviating significantly from the cluster and field distributions, the membership probability could not be determined. pclus has a value of -99.99 in these cases. Monte Carlo simulations of the proper motion plane for one of the outer cluster fields (the Pistol field, Field 2 in Hussmann 2014, PhD thesis, Univ. Bonn, http://www.astro.uni-bonn.de/~hussmann/thesis/) suggest that cluster and field stars are most efficiently separated with a formal probability threshold of pclus > 0.4 (see Sections 126.96.36.199 to 188.8.131.52 in Hussmann (2014) for details).
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 4 I4 --- Seq Sequential number 6- 12 F7.3 arcsec dRA Right Ascension offset (J2000) (G1) 14- 20 F7.3 arcsec dDE Declination offset (J2000) (G1) 22- 28 F7.3 mas/yr pmRA Proper motion in RA; milliarcsec/yr 30- 34 F5.3 mas/yr e_pmRA Uncertainty in pmRA 36- 42 F7.3 mas/yr pmDE Proper motion in Declination; milliarcsec/yr 44- 48 F5.3 mas/yr e_pmDE Uncertainty in pmDE 50- 55 F6.3 mag Kmag03 The 2003 VLT/NACO Ks band magnitude (G2) 57- 61 F5.3 mag e_Kmag03 Uncertainty in Kmag03 63- 68 F6.3 mag Kmag08 The 2008 VLT/NACO KS band magnitude (G2) 70- 74 F5.3 mag e_Kmag08 Uncertainty in Kmag08 76- 82 F7.3 --- pclus ?=-99.99 Membership probability indicator (3)
Note (3): For stars deviating significantly from the cluster and field distributions, the membership probability could not be determined. pclus has a value of -99.99 in these cases.
Global notes: Note (G1): Positional offsets in Right Ascension and Declination are calculated with respect to the central star Q12: RA = 17:46:15.13 DEC = -28:49:35.07 Note (G2): Photometry is provided for both NACO epochs, with photometry of stars with Ks < 14 mag taken from the NACO 2003 2s exposures, while fainter photometry is supplemented from the deep 20s integrations.
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 08-Mar-2017
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