J/ApJ/750/91 Ages and metallicities of old stellar systems (Chattopadhyay+ 2012)
Uncovering the formation of ultracompact dwarf galaxies by multivariate
statistical analysis.
Chattopadhyay T., Sharina M., Davoust E., De T., Chattopadhyay A.K.
<Astrophys. J., 750, 91 (2012)>
=2012ApJ...750...91C 2012ApJ...750...91C
ADC_Keywords: Clusters, globular ; Galaxies, optical ; Morphology ;
Abundances, [Fe/H]
Keywords: galaxies: general, methods: data analysis, methods: statistical
Abstract:
We present a statistical analysis of the properties of a large sample
of dynamically hot old stellar systems, from globular clusters (GCs)
to giant ellipticals, which was performed in order to investigate the
origin of ultracompact dwarf galaxies (UCDs). The data were mostly
drawn from Forbes et al. (2008, Cat. J/MNRAS/389/1924). We
recalculated some of the effective radii, computed mean surface
brightnesses and mass-to-light ratios, and estimated ages and
metallicities. We completed the sample with GCs of M31. We used a
multivariate statistical technique (K-Means clustering), together with
a new algorithm (Gap Statistics) for finding the optimum number of
homogeneous sub-groups in the sample, using a total of six parameters
(absolute magnitude, effective radius, virial mass-to-light ratio,
stellar mass-to-light ratio, and metallicity). We found six groups.
FK1 and FK5 are composed of high- and low-mass elliptical galaxies,
respectively. FK3 and FK6 are composed of high-metallicity and
low-metallicity objects, respectively, and both include GCs and UCDs.
Two very small groups, FK2 and FK4, are composed of Local Group dwarf
spheroidals. Our groups differ in their mean masses and virial
mass-to-light ratios. The relations between these two parameters are
also different for the various groups. The probability density
distributions of metallicity for the four groups of galaxies are
similar to those of the GCs and UCDs. The brightest low-metallicity
GCs and UCDs tend to follow the mass-metallicity relation like
elliptical galaxies. The objects of FK3 are more metal-rich per unit
effective luminosity density than high-mass ellipticals.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 105 389 Photometric and structural parameters of the
objects of the sample studied.
refs.dat 173 24 References
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/549/A60 : Ages and [Fe/H] of M31 globular clusters (Cezario+, 2013)
J/AJ/143/14 : Lick indices of M31 globular clusters (Schiavon+, 2012)
J/AJ/141/61 : Star clusters in M31. II. (Caldwell+, 2011)
J/A+A/508/1285 : Metallicities of M31 globular clusters (Galleti+, 2009)
J/MNRAS/389/1924 : Old stellar systems (globulars to ellipticals)
(Forbes+, 2008)
J/A+A/463/455 : Nearby gal. with ionized gas. III. (Annibali+, 2007)
J/A+A/450/105 : Properties of 153 Galactic globular clusters (Bica+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Name
16- 22 F7.5 [pc] logRh [0.1/4.8] Log of half light radius
24- 29 F6.2 mag KMag [-26.5/-6.8] Absolute K band magnitude
31- 35 F5.2 mag/arcsec2 muhK [11.2/26.1] K band surface brightness
37- 43 F7.3 Msun/Lsun Mv/LK [0.2/141] Virial mass to K band luminosity
ratio
45- 49 F5.2 Msun/Lsun M/LV [0.1/84] Baryonic mass to K band
luminosity ratio
51- 55 F5.2 mag U-B [-0.2/0.7]? The (U-B) color index
57- 60 F4.2 mag B-V [0.4/1.3]? The (B-V) color index
62- 65 F4.2 mag V-I [0.6/1.4]? The (V-I) color index
67- 70 F4.2 mag B-K [0.1/6.5]? The (B-K) color index
72- 76 F5.2 [Sun] [Fe/H] [-1.9/0.3]? Metallicity from this work
78- 82 F5.2 Gyr Age [0.1/14]? Age from this work
83 A1 --- u_Age Uncertainty flag on Age
85- 89 F5.2 [Sun] [Fe/H]l [-2.3/0.7]? Metallicity in literature
90 A1 --- u_[Fe/H]l Uncertainty flag on [Fe/H]l
92- 97 F6.3 Gyr Agel [0.4/19]? Age in literature
98 A1 --- u_Agel Uncertainty flag on Agel
100-103 A4 --- Ref Reference(s) for [Fe/H]l and Agel
(see refs.dat file)
105 I1 --- Group [1/6] Group number (1)
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Note (1): Groups #1 and #5 are composed of high- and low-mass elliptical
galaxies, respectively. #3 and #6 are composed of high-metallicity
and low-metallicity objects, respectively, and both include globular
clusters and ultra-compact dwarf galaxies. Two very small groups, #2
and #4, are composed of Local Group dwarf spheroidals. Our groups
differ in their mean masses and virial mass-to-light ratios. The
relations between these two parameters are also different for the
various groups. See table 3 for the average properties of groups #1,
3, 5 and 6.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode Bibcode
24- 46 A23 --- Aut Author's name(s)
48-173 A126 --- Comm Comment
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 04-Dec-2013