J/AJ/138/1667 HST survey of young clusters in M31. III. (Barmby+, 2009)
A Hubble Space Telescope/WFPC2 survey of bright young clusters in M31.
III. Structural parameters.
Barmby P., Perina S., Bellazzini M., Cohen J.G., Hodge P.W., Huchra J.P.,
Kissler-Patig M., Puzia T.H., Strader J.
<Astron. J., 138, 1667-1680 (2009)>
=2009AJ....138.1667B 2009AJ....138.1667B
ADC_Keywords: Clusters, globular ; Photometry, HST ; Models ;
Photometry, surface
Keywords: galaxies: individual (Messier: Number M31) - galaxies: star clusters -
globular clusters: general
Abstract:
Surface brightness profiles for 23 M31 star clusters were measured
using images from the Wide Field Planetary Camera 2 on the Hubble
Space Telescope, and fitted to two types of models to determine the
clusters' structural properties. The clusters are primarily young
(∼108yr) and massive (∼104.5M☉), with median half-light radius
7pc and dissolution times of a few Gyr. The properties of the M31
clusters are comparable to those of clusters of similar age in the
Magellanic Clouds. Simulated star clusters are used to derive a
conversion from statistical measures of cluster size to half-light
radius so that the extragalactic clusters can be compared to young
massive clusters in the Milky Way. All three sets of star clusters
fall approximately on the same age-size relation. The young M31
clusters are expected to dissolve within a few Gyr and will not
survive to become old, globular clusters. However, they do appear to
follow the same fundamental plane (FP) relations as old clusters; if
confirmed with velocity dispersion measurements, this would be a
strong indication that the star cluster FP reflects universal cluster
formation conditions.
Description:
The main sample of clusters studied here is described in detail by the
companion papers by Perina et al. (2009A&A...494..933P 2009A&A...494..933P,
2009A&A...507.1375P 2009A&A...507.1375P). HST program GO-10818 was aimed at imaging all of
the "class A" clusters proposed by Fusi Pecci et al.
(2005AJ....130..554F 2005AJ....130..554F) which did not already have HST imaging, a total
of 19 objects. We augmented the GO-10818 data with archival data on
the four clusters studied by Williams & Hodge (2001ApJ...548..190W 2001ApJ...548..190W) to
bring the total number of clusters to 23. All objects were observed
with HST/WFPC2 in two 400s dithered images in each of two filters:
F450W and F814W. The GO-8296 program was also carried out with WFPC2
and involved two 800s images in F439W and two 600s images in F555W.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 23 Data sets for M31 young clusters
table3.dat 126 92 Basic parameters of fits to profiles of M31
young clusters
table4.dat 190 92 Derived structural and photometric parameters
for M31 young clusters
table5.dat 182 92 Derived dynamical parameters for M31 young clusters
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See also:
J/A+A/531/A155 : HST photometry in six M31 globular clusters (Perina+, 2011)
J/A+A/507/1375 : HST/ACS VI data of M31 globular clusters (Perina+, 2009)
J/AJ/138/770 : HST/WFPC survey of M31 bright young clusters (Hodge+, 2009)
J/AJ/137/94 : Star clusters in M31 (Caldwell+, 2009)
J/A+A/483/769 : HST VI photometry of 3 globulars in M31 (Fuentes-Carrera+,
2008)
J/A+A/471/127 : New globular clusters in M31 (Galleti+, 2007)
J/A+A/416/917 : Revised Bologna Catalog of M31 globular clusters (Galleti+,
2004)
J/ApJ/559/851 : Young star cluster candidates in M31 (Williams+, 2001)
J/AJ/122/2458 : M31 globular clusters from HST (Barmby+, 2001)
J/AJ/114/1488 : Globulars in M31 (Holland+ 1997)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Cluster name (G1)
6 A1 --- f_Name [*] *: B195D = VDB0 (in table 1 of the paper)
8- 18 A11 --- Set1 Data set 1
20- 30 A11 --- Set2 Data set 2
32- 36 A5 --- Filt1 [F439W/F450W] Filter 1
38- 41 I4 s Exp1 Exposure time 1
43- 47 A5 --- Filt2 [F555W/F814W] Filter 2
49- 52 I4 s Exp2 Exposure time 2
54- 57 F4.2 mag E(B-V) Color excess
59- 63 F5.2 [yr] logAge Assumed age (1)
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Note (1): Assumed ages for all clusters: those given by Perina et al.
(2009A&A...507.1375P 2009A&A...507.1375P) for the young clusters from GO-10818, by
Williams & Hodge (2001ApJ...548..190W 2001ApJ...548..190W) for the clusters from GO-8296,
and assumed ages of 13Gyr for the clusters B083, B222, B347, B374 and NB16.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Source name (G1)
7- 11 A5 --- Filt Filter (F439W, F450W, F555W or F814W)
13- 14 I2 --- Npts Number of points
16- 18 A3 --- Model [K66/W ] Model code (G2)
20- 26 F7.2 --- chi2 Unreduced χ2 of best-fitting model
28- 34 F7.2 Lsun/pc2 Ibkg Model-fit background intensity (1)
36- 40 F5.2 Lsun/pc2 e_Ibkg ?=0.00 Error in Ibkg
42- 46 F5.2 --- W0 Model-fit central potential (dimensionless,
measures degree of central concentration)
48- 52 F5.2 --- E_W0 Upper 68% confidence interval in W0
54- 57 F4.2 --- e_W0 Lower 68% confidence interval in W0
59- 62 F4.2 --- c Model-fit concentration (2)
64- 67 F4.2 --- E_c Upper 68% confidence interval in c
69- 72 F4.2 --- e_c Lower 68% confidence interval in c
74- 78 F5.2 mag/arcsec2 mu0 Model-fit central surface brightness
80- 83 F4.2 mag/arcsec2 E_mu0 Upper 68% confidence interval in mu0
85- 88 F4.2 mag/arcsec2 e_mu0 Lower 68% confidence interval in mu0
90- 95 F6.3 [arcsec] logAr0 Log of model-fit angular scale radius
97-101 F5.3 [arcsec] E_logAr0 Upper 68% confidence interval in logAr0
103-107 F5.3 [arcsec] e_logAr0 Lower 68% confidence interval in logAr0
109-114 F6.3 [pc] logPr0 Log of model-fit physical scale radius
116-120 F5.3 [pc] E_logPr0 Upper 68% confidence interval in logPr0
122-126 F5.3 [pc] e_logPr0 Lower 68% confidence interval in logPr0
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Note (1): Values without uncertainties indicate clusters for which the
background was fixed manually.
Note (2): c=log(rt/r0) where rt is the tidal radius given in Table 4.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Source name (G1)
7- 11 A5 --- Filt Filter (F439W, F450W, F555W or F814W)
13- 18 F6.3 mag V-X The (V-Filt) color index
20- 24 F5.3 mag e_V-X Error in V-X
26- 28 A3 --- Model [K66/W ] Model code (G2)
30- 33 F4.2 [pc] logrt Log of model tidal radius
35- 38 F4.2 [pc] E_logrt Upper 68% confidence interval in logrt
40- 43 F4.2 [pc] e_logrt Lower 68% confidence interval in logrt
45- 50 F6.3 [pc] logRc Log of model projected core radius (1)
52- 56 F5.3 [pc] E_logRc Upper 68% confidence interval in logRc
58- 62 F5.3 [pc] e_logRc Lower 68% confidence interval in logRc
64- 68 F5.3 [pc] logRh Log of model projected half-light radius
70- 74 F5.3 [pc] E_logRh Upper 68% confidence interval in logRh
76- 80 F5.3 [pc] e_logRh Lower 68% confidence interval in logRh
82- 86 F5.3 [-] logRh/Rc Log of half-light to projected core
radii (2)
88- 92 F5.3 [-] E_logRh/Rc Upper 68% confidence interval in logRh/Rc
94- 98 F5.3 [-] e_logRh/Rc Lower 68% confidence interval in logRh/Rc
100-103 F4.2 [Lsun/pc2] logI0 Log of model central luminosity surface
density in the V band
105-108 F4.2 [Lsun/pc2] E_logI0 Upper 68% confidence interval in logI0
110-113 F4.2 [Lsun/pc2] e_logI0 Lower 68% confidence interval in logI0
115-118 F4.2 [Lsun/pc3] logj0 Log of central luminosity volume
density in the V band
120-123 F4.2 [Lsun/pc3] E_logj0 Upper 68% confidence interval in logj0
125-128 F4.2 [Lsun/pc3] e_logj0 Lower 68% confidence interval in logj0
130-133 F4.2 [Lsun] logL Log of total integrated model
luminosity in the V band
135-138 F4.2 [Lsun] E_logL Upper 68% confidence interval in logL
140-143 F4.2 [Lsun] e_logL Lower 68% confidence interval in logL
145-149 F5.2 mag Vmag Total extinction-corrected apparent V
band magnitude (3)
151-154 F4.2 mag E_Vmag Upper 68% confidence interval in Vmag
156-159 F4.2 mag e_Vmag Lower 68% confidence interval in Vmag
161-164 F4.2 [Lsun/pc2] logIh Log surface density averaged over
half-light radius (4)
166-169 F4.2 [Lsun/pc2] E_logIh Upper 68% confidence interval in logIh
171-174 F4.2 [Lsun/pc2] e_logIh Lower 68% confidence interval in logIh
176-180 F5.2 mag/arcsec2 muh Average surface brightness within
half-light radius in the V band
182-185 F4.2 mag/arcsec2 E_muh Upper 68% confidence interval in muh
187-190 F4.2 mag/arcsec2 e_muh Lower 68% confidence interval in muh
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Note (1): At which intensity is half the central value.
Note (2): A measure of cluster concentration.
Note (3): Vmag=4.83-2.5log(LV/LSun)+5log(D/10pc).
Note (4): Ih=LV/2πRh2.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Name Source name (G1)
7- 11 A5 --- Filt Filter (F439W, F450W, F555W or F814W)
13- 17 F5.3 Msun/Lsun M/L Assumed mass-to-light ratio in the
V-band
19- 23 F5.3 Msun/Lsun E_M/L Upper 68% confidence interval in M/L
25- 29 F5.3 Msun/Lsun e_M/L Lower 68% confidence interval in M/L
31- 33 A3 --- Model [K66/W ] Model code (G2)
35- 38 F4.2 [Msun] logMt Log of integrated model mass
40- 43 F4.2 [Msun] E_logMt Upper 68% confidence interval in logMt
45- 48 F4.2 [Msun] e_logMt Lower 68% confidence interval in logMt
50- 54 F5.2 [10-7J] logEb Log of integrated binding energy
56- 59 F4.2 [10-7J] E_logEb Upper 68% confidence interval in logEb
61- 64 F4.2 [10-7J] e_logEb Lower 68% confidence interval in logEb
66- 69 F4.2 [Msun/pc2] logS0 Log of central surface mass density
71- 74 F4.2 [Msun/pc2] E_logS0 Upper 68% confidence interval in logS0
76- 79 F4.2 [Msun/pc2] e_logS0 Lower 68% confidence interval in logS0
81- 84 F4.2 [Msun/pc3] logrho Log of central volume density
86- 89 F4.2 [Msun/pc3] E_logrho Upper 68% confidence interval in
logrho
91- 94 F4.2 [Msun/pc3] e_logrho Lower 68% confidence interval in
logrho
96-100 F5.2 [Msun/pc2] logSh Log of surface mass density
averaged over half-light radius
102-105 F4.2 [Msun/pc2] E_logSh Upper 68% confidence interval in logSh
107-110 F4.2 [Msun/pc2] e_logSh Lower 68% confidence interval in logSh
112-117 F6.3 [km/s] logsp0 Log of predicted line-of-sight
velocity dispersion at cluster center
119-123 F5.3 [km/s] E_logsp0 Upper 68% confidence interval in
logsp0
125-129 F5.3 [km/s] e_logsp0 Lower 68% confidence interval in
logsp0
131-135 F5.3 [km/s] logv Log of predicted central escape
velocity
137-141 F5.3 [km/s] E_logv Upper 68% confidence interval in logv
143-147 F5.3 [km/s] e_logv Lower 68% confidence interval in logv
149-153 F5.2 [yr] logt Log of two-body relaxation time (1)
155-158 F4.2 [yr] E_logt Upper 68% confidence interval in logt
160-163 F4.2 [yr] e_logt Lower 68% confidence interval in logt
165-170 F6.3 [Msun.s3/pc3/km3] logf0 Log of model's relaxation time (2)
172-176 F5.3 [Msun.s3/pc3/km3] E_logf0 Upper 68% confidence interval in logf0
178-182 F5.3 [Msun.s3/pc3/km3] e_logf0 Lower 68% confidence interval in logf0
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Note (1): At model projected half-mass radius
Note (2): A measure of the model's central phase-space density.
log(f0)=log[ρ0/(2πσc2)3/2]
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Global notes:
Note (G1): Naming convention of the Revised Bologna Catalog (Galleti et al.
2004, Cat. J/A+A/416/917; <M31GC JHHMMSS+DDMMSS> in SIMBAD) is used.
Note (G2): Star cluster density profiles from model as follows:
K66 = King (1966AJ.....71...64K 1966AJ.....71...64K)
W = Wilson (1975AJ.....80..175W 1975AJ.....80..175W).
Unlike other types of model profile, the King and Wilson models have
no analytic expressions for density or surface brightness as a
function of projected radius; profiles are obtained by integrating
phase-space distribution functions over all velocities and then along
the line of sight, assuming spherical symmetry (for a review, see
McLaughlin 2003ASPC..296..101M 2003ASPC..296..101M). See section 2.3.
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History:
From electronic version of the journal
References:
Perina et al. Paper I. 2009A&A...494..933P 2009A&A...494..933P
Hodge et al. Paper II. 2009AJ....138..770H 2009AJ....138..770H Cat. J/AJ/138/770
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Jan-2012