J/A+A/695/A156 The Bulge globular cluster Terzan 6 (Loriga+, 2025)
The bulge globular cluster Terzan 6 as seen from multi-conjugate adaptive optics
and HST.
Loriga M., Pallanca C., Ferraro F.R., Dalessandro E., Lanzoni B.,
Cadelano M., Origlia L., Fanelli C., Geisler D., Villanova S.
<Astron. Astrophys. 695, A156 (2025)>
=2025A&A...695A.156L 2025A&A...695A.156L (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Photometry, HST ;
Photometry, infrared
Keywords: Hertzsprung-Russell and C-M diagrams - stars: Population II -
globular clusters: general - Galaxy: stellar content
Abstract:
This work consists of the first detailed photometric study of
Terzan 6, one of the least known globular clusters in the Galactic
bulge. Through the analysis of high angular resolution and
multi-wavelength data obtained from adaptive optics corrected and
space observations, we built deep, optical and near-infrared
color-magnitude diagrams reaching ∼4 magnitudes below the
main-sequence turnoff. Taking advantage of 4 different epochs of
observations, we measured precise relative proper motions for a large
sample of stars, from which cluster members have been solidly
distinguished from Galactic field interlopers. A non-canonical
reddening law (with RV=2.85) and high-resolution differential
reddening map, with color excess variations up to
δE(B-V)∼0.8mag, have been derived in the direction of the
system. According to these findings, new values of the extinction and
distance modulus have been obtained: respectively, E(B-V)=2.36±0.05
and (m-M)0=14.46±0.10 (corresponding to d=7.8±0.3kpc). We also
provide the first determinations of the cluster center and projected
density profile from resolved star counts. The center is offset by
more than 7-arcsec to the east from the literature value, and the
structural parameters obtained from the King model fitting to the
density profile indicate that Terzan 6 is in an advanced stage of its
dynamical evolution, with a large value of the concentration parameter
(c=1.94-0.26+0.24) and a small core radius
(rc=2.6-0.7+0.9-arcsec). We also determined the absolute age of
the system, finding t=13±1Gyr, in agreement with the old ages found
for the globular clusters in the Galactic bulge. From the
re-determination of the absolute magnitude of the red giant branch
bump and the recent estimate of the cluster global metallicity, we
find that Terzan 6 nicely matches the tight relation between these two
parameters drawn by the Galactic globular cluster population.
Description:
The table contains the catalogue of the Bulge globular cluster
Terzan 6.
The table includes the stars ID, the right ascension and declination,
the relative proper motions along the x- and y-directions, the
calibrated magnitudes and relative errors in the F606W, F814W, J, and
Ks filters the chi and the sharpness parameters, a flag to identify
member stars (fpm=1), non-member stars (fpm=0), and stars with no
PM measure (fpm=9), the differential reddening dE(B-V) values.
99.999 stands for no measured data.
Objects:
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RA (2000) DE Designation(s)
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17 50 46.39 -31 16 31.0 Terzan 6 = ESO 455-49
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 126 250350 Catalogue of the bulge globular cluster Terzan 6
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See also:
J/A+AS/122/483 : Terzan 6 NTT VI photometry (Barbuy+ 1997)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- ID [1/250350] Star ID
8- 17 F10.6 deg RAdeg Right ascension (J2000)
19- 28 F10.6 deg DEdeg Declination (J2000)
30- 38 F9.6 mas/yr pmx ?=100 Relative proper motion in x-direction
40- 48 F9.6 mas/yr pmy ?=100 Relative proper motion in y-direction
50- 55 F6.3 mag F606W ?=99.999 Magnitude in F606W filter
57- 62 F6.3 mag e_F606W ?=99.999 Uncertainty on the F606W magnitude
64- 69 F6.3 mag F814W ?=99.999 Magnitude in F814W filter
71- 76 F6.3 mag e_F814W ?=99.999 Uncertainty on the F814W magnitude
78- 83 F6.3 mag Jmag ?=99.999 Magnitude in J filter
85- 90 F6.3 mag e_Jmag ?=99.999 Uncertainty on the J magnitude
92- 97 F6.3 mag Ksmag ?=99.999 Magnitude in K_s filter
99-104 F6.3 mag e_Ksmag ?=99.999 Uncertainty on the K_s magnitude
106-111 F6.3 --- chi Chi parameter
113-118 F6.3 --- sh ?=99.999 Sharpness parameter
120 I1 --- f_pm [0/1]?=9 Flag for member and
non-member stars (1)
122-126 F5.2 mag dE(B-V) ?=99.99 Differential reddening values
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Note (1): Flag as follows:
0 = non-member star
1 = member star
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Acknowledgements:
Martina Loriga, martina.loriga2(at)unibo.it
(End) Patricia Vannier [CDS] 14-Feb-2025