J/MNRAS/450/2692 Parameters of galactic globular clusters (Vanderbeke+, 2015)
G2C2.
III. Structural parameters for Galactic globular clusters in SDSS passbands.
Vanderbeke J, De Propris R., De Rijcke S., Baes M., West M.J.,
Blakeslee J.P.
<Mon. Not. R. Astron. Soc. 450, 2692 (2015)>
=2015MNRAS.450.2692V 2015MNRAS.450.2692V
ADC_Keywords: Clusters, globular ; Photometry, SDSS ; Morphology
Keywords: globular clusters: general
Abstract:
We use our Galactic Globular Cluster Catalog (G2C2) photometry for 111
Galactic globular clusters (GCs) in g and z, as well as r and i
photometry for a subset of 60 GCs and u photometry for 22 GCs, to
determine the structural parameters assuming King models. In general,
the resulting core radii are in good comparison with the current
literature values. However, our half-light radii are slightly lower
than the literature. The concentrations (and therefore also the tidal
radii) are poorly constrained mostly because of the limited radial
extent of our imaging. Therefore, we extensively discuss the effects
of a limited field of view on the derived parameters using mosaicked
Sloan Digital Sky Survey data, which do not suffer from this
restriction. We also illustrate how red giant branch (RGB) stars in
cluster cores can stochastically induce artificial peaks in the
surface brightness profiles. The issues related to these bright stars
are scrutinized based on both our photometry and simulated clusters.
We also examine colour gradients and find that the strongest central
colour gradients are caused by central RGB stars and thus not
representative for the cluster light or colour distribution. We
recover the known relation between the half-light radius and the
Galactocentric distance in the g band, but find a lower slope for
redder filters. We did not find a correlation between the scatter on
this relation and other cluster properties. We find tentative evidence
for a correlation between the half-light radii and the [Fe/H], with
metal-poor GCs being larger than metal-rich GCs. However, we conclude
that this trend is caused by the position of the clusters in the
Galaxy, with metal-rich clusters being more centrally located.
Description:
The data set for this paper is based on the Galactic Globular Cluster
Catalog (G2C2): a homogeneous imaging survey of a large fraction of
the Galactic GC system in the SDSS passbands. Paper I (Vanderbeke et
al., 2014MNRAS.437.1725V 2014MNRAS.437.1725V, Cat. J/MNRAS/437/1725) details the data
acquisition process and describes how these data were reduced.
We provide the tables 1 and 2 from G2C2-III, which list the structural
King parameters. Table 1 lists parameters based on CTIO 0.9m telescope
data, Table 2 presents parameters based on SDSS data. Systematic
errors, dominating the error budget, are given in Table 3.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
sources.dat 44 98 List of studied globular clusters
table1.dat 78 235 Structural King parameters based on CTIO data
for 84 sources
table2.dat 78 89 Globular cluster King parameters based on SDSS data
for 19 sources
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See also:
J/MNRAS/437/1725 : G2C2. I. Galactic globular clusters SDSS photometry
(Vanderbeke+, 2014)
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Globular cluster name
12- 13 I2 h RAh Simbad Right ascension (J2000)
15- 16 I2 min RAm Simbad Right ascension (J2000)
18- 22 F5.2 s RAs Simbad Right ascension (J2000)
24 A1 --- DE- Simbad Declination sign (J2000)
25- 26 I2 deg DEd Simbad Declination (J2000)
28- 29 I2 arcmin DEm Simbad Declination (J2000)
31- 34 F4.1 arcsec DEs Simbad Declination (J2000)
36- 39 A4 --- CTIO "CTIO" origin (in table1)
41- 44 A4 --- SDSS "SDSS" origin (in table2)
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Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Globular cluster name
10 A1 --- Filt [ugriz] Filter for parameters
12- 17 F6.3 mag/arcsec2 mu0 [12.8/25.1] Surface brightness in Filt (1)
19- 23 F5.3 mag/arcsec2 e_mu0 [0.001/2.3] rms uncertainty on mu0 (1)
25- 29 F5.3 arcmin rc [0.08/4] Core radius in Filt band (1)
31- 35 F5.3 arcmin e_rc [0/6.3] rms uncertainty on rc (1)
37- 41 F5.3 arcmin rh [0.09/4] Half-light radius in Filt band (1)
43- 47 F5.3 arcmin e_rh [0/0.6] rms uncertainty on rh (1)
49- 54 F6.3 mag mag Model magnitude in Filt band computed
within the listed rh
56- 61 F6.3 mag mag.r Aperture magnitude in Filt band computed
within the listed rh
63- 67 F5.1 s texp [60/410]? CTIO exposure time in Filt band
69- 73 F5.3 --- chi2 [0/3.5] Reduced χ2 value in Filt band
75- 76 I2 --- dof [4/63] Degrees of freedom in Filt band
78 I1 --- fit [0/1] Flag indicates if the central SB
point was included by the final fit
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Note (1): Systematic errors for the structural parameters due to the
stochastically distributed RGB stars and the uncertainty on the centre
determination are (table 3):
--------------------------------------------------------
Filter e_syst(mu0) e_syst(rc) e_syst(rh)
mag/arcsec2 arcmin arcmin
--------------------------------------------------------
g 0.228 0.077 0.101
z 0.289 0.118 0.191
--------------------------------------------------------
For the ri parameters, the systematic uncertainties for the z band should be
adopted for all parameters.
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Acknowledgements:
Joachim Vanderbeke, joachimvanderbeke(at)gmail.com
References:
Vanderbeke et al., Paper I 2014MNRAS.437.1725V 2014MNRAS.437.1725V, Cat. J/MNRAS/437/1725
Vanderbeke et al., Paper II 2014MNRAS.437.1734V 2014MNRAS.437.1734V
Vanderbeke et al., Paper IV 2015MNRAS.451.4794V 2015MNRAS.451.4794V
(End) J. Vanderbeke [Ghent Univ., Belgium], P. Vannier [CDS] 08-Jun-2015