J/ApJ/769/107 RVs and [Fe/H] of star members of NGC 6388 (Lanzoni+, 2013)
The velocity dispersion profile of NGC 6388 from resolved-star spectroscopy:
no evidence of a central cusp and new constraints on the black hole mass.
Lanzoni B., Mucciarelli A., Origlia L., Bellazzini M., Ferraro F.R.,
Valenti E., Miocchi P., Dalessandro E., Pallanca C., Massari D.
<Astrophys. J., 769, 107 (2013)>
=2013ApJ...769..107L 2013ApJ...769..107L
ADC_Keywords: Abundances, [Fe/H] ; Radial velocities ; Photometry, HST ;
Clusters, globular
Keywords: black hole physics; globular clusters: individual: NGC 6388;
stars: evolution
Abstract:
By combining high spatial resolution and wide-field spectroscopy
performed, respectively, with SINFONI and FLAMES at the ESO/VLT we
measured the radial velocities of more than 600 stars in the direction
of NGC 6388, a Galactic globular cluster which is suspected to host an
intermediate-mass black hole. Approximately 55% of the observed
targets turned out to be cluster members. The cluster velocity
dispersion has been derived from the radial velocity of individual
stars: 52 measurements in the innermost 2", and 276 stars located
between 18" and 600". The velocity dispersion profile shows a central
value of ∼13km/s, a flat behavior out to ∼60" and a decreasing trend
outward. The comparison with spherical and isotropic models shows that
the observed density and velocity dispersion profiles are inconsistent
with the presence of a central black hole more massive than
∼2000M☉. These findings are at odds with recent results obtained
from integrated light spectra, showing a velocity dispersion profile
with a steep central cusp of 23-25km/s at r<2" and suggesting the
presence of a black hole with a mass of ∼1.7x104M☉. We also
found some evidence of systemic rotation with amplitude Arot∼8km/s
in the innermost 2" (0.13pc), decreasing to Arot=3.2km/s at
18"<r<160".
Description:
In order to acquire spectra of individual stars in the center of
NGC6388, we exploited the high spatial resolution capabilities of
SINFONI, a near-IR (1.1-2.45um) integral field spectrograph fed by an
adaptive optics module and mounted on the YEPUN (VLT-UT4) telescope at
the ESO Paranal Observatory. The observations were performed in
service mode between 2008 April and June (ESO proposal ID:381.D-0329(A);
PI: Lanzoni), under an average seeing of ∼0.8" (FWHM).
The spectra of individual stars beyond the cluster core were acquired
using the ESO VLT multi-object spectrograph FLAMES, in the MEDUSA
UVES+GIRAFFE combined mode. Under proposal 381.D-0329(B) (PI:Lanzoni),
4 pointings of 2320s each were performed in 2008 June and July with
the GIRAFFE grating HR21 (which samples the CaII triplet spectral
range at a resolution R=16200) and the UVES setup Red Arm 580,
covering the wavelength range 4800<λ<6800Å at a resolution
R=47000.
The targets were selected from the combined HST/ACS-WFC and ESO/WFI
photometric catalog already discussed in Lanzoni et al.
(2007ApJ...668L.139L 2007ApJ...668L.139L) and Dalessandro et al. (2008, J/ApJ/677/1069).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 68 328 Parameters for all the stars selected as cluster
members and used to compute the rotational
velocity and velocity dispersion of NGC 6388
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See also:
B/eso : ESO Science Archive Catalog (ESO, 1991-2014)
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/A+A/563/A80 : WFI ground-based astrometry. V. (Libralato+, 2014)
J/A+A/533/A36 : VI phot. and velocity map of NGC 6388 (Luetzgendorf+, 2011)
J/ApJ/677/1069 : Blue stragglers in NGC 6388 (Dalessandro+, 2008)
J/AJ/134/1298 : CaII EWs in 29 Galactic clusters (Carrera+, 2007)
J/AJ/134/229 : CT1T2 Photometry of red giants in 2 globulars (Hughes+, 2007)
J/A+A/464/967 : Abundances of red giants in NGC 6388 (Carretta+, 2007)
J/AJ/132/447 : Surface Brightness of 38 Gal. GCs (Noyola+, 2006)
J/ApJS/161/304 : Clusters in the Milky Way & satellites (McLaughlin+, 2005)
J/A+A/391/945 : HST phot. of 74 galactic globular clusters (Piotto+, 2002)
J/A+A/324/505 : Core velocity dispersions of globular clusters (Dubath+ 1997)
J/AJ/109/218 : Catalogue of globular cluster profiles (Trager+ 1995)
J/AJ/107/1764 : RR Lyrae and CMD of NGC 6388 (Silbermann+, 1994)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- ID [20354/10000357] Identification number
10- 20 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
22- 32 F11.7 deg DEdeg Declination in decimal degrees (J2000)
34- 38 F5.2 mag Bmag ? The B band magnitude
40- 44 F5.2 mag Vmag [14.8/19.3] The V band magnitude
46- 50 F5.2 mag Imag ? The I band magnitude
52- 56 F5.1 km/s RVel [-27.6/40.7] Radial velocity
58- 60 F3.1 km/s e_RVel [0.1/6] Uncertainty in RVel
62- 66 F5.2 [Sun] [Fe/H] [-0.7/-0.1]? Metallicity
68 I1 --- Inst [1/2] Instrument: 1=SINFONI (no metallicity),
2=FLAMES
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-Dec-2014