J/AJ/138/1667HST 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....138.1667BADC_Keywords: Clusters, globular ; Photometry, HST ; Models ; Photometry, surfaceKeywords: galaxies: individual (Messier: Number M31) - galaxies: star clusters - globular clusters: generalAbstract: 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...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) 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) 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:

FileName Lrecl Records Explanations

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

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

Bytes Format Units Label Explanations

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)

Note (1): Assumed ages for all clusters: those given by Perina et al. (2009A&A...507.1375P) for the young clusters from GO-10818, by Williams & Hodge (2001ApJ...548..190W) for the clusters from GO-8296, and assumed ages of 13Gyr for the clusters B083, B222, B347, B374 and NB16.

Byte-by-byte Description of file: table3.dat

Bytes Format Units Label Explanations

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 χ^{2}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

Note (1): Values without uncertainties indicate clusters for which the background was fixed manually.Note (2): c=log(r_{t}/r_{0}) where r_{t}is the tidal radius given in Table 4.

Byte-by-byte Description of file: table4.dat

Bytes Format Units Label Explanations

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

Note (1): At which intensity is half the central value.Note (2): A measure of cluster concentration.Note (3): Vmag=4.83-2.5log(L_{V}/L_{Sun})+5log(D/10pc).Note (4): I_{h}=L_{V}/2πR_{h}^{2}.

Byte-by-byte Description of file: table5.dat

Bytes Format Units Label Explanations

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

Note (1): At model projected half-mass radiusNote (2): A measure of the model's central phase-space density. log(f_{0})=log[ρ_{0}/(2πσ_{c}^{2})^{3/2}]

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) W = Wilson (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). See section 2.3.

History: From electronic version of the journalReferences: Perina et al. Paper I. 2009A&A...494..933P Hodge et al. Paper II. 2009AJ....138..770H Cat. J/AJ/138/770(End)Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Jan-2012

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