J/AJ/146/135 Physical parameters of 29 M31 globular clusters (Agar+, 2013) ================================================================================ M31 globular cluster structures and the presence of X-ray binaries. Agar J.R.R., Barmby P. =2013AJ....146..135A ================================================================================ ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Binaries, X-ray Keywords: galaxies: individual: M31 - galaxies: star clusters: general - X-rays: binaries Abstract: The Andromeda galaxy, M31, has several times the number of globular clusters found in the Milky Way. It contains a correspondingly larger number of low-mass X-ray binaries (LMXBs) associated with globular clusters, and as such can be used to investigate the cluster properties that lead to X-ray binary formation. The best tracer of the spatial structure of M31 globulars is the high-resolution imaging available from the Hubble Space Telescope (HST), and we have used HST data to derive structural parameters for 29 LMXB-hosting M31 globular clusters. These measurements are combined with structural parameters from the literature for a total of 41 (of 50 known) LMXB clusters and a comparison sample of 65 non-LMXB clusters. Structural parameters measured in blue bandpasses are found to be slightly different (smaller core radii and higher concentrations) than those measured in red bandpasses; this difference is enhanced in LMXB clusters and could be related to stellar population differences. Clusters with LMXBs show higher collision rates for their mass compared to clusters without LMXBs, and collision rates estimated at the core radius show larger offsets than rates estimated at the half-light radius. These results are consistent with the dynamical formation scenario for LMXBs. A logistic regression analysis finds that, as expected, the probability of a cluster hosting an LMXB increases with increasing collision rate and proximity to the galaxy center. The same analysis finds that probability of a cluster hosting an LMXB decreases with increasing cluster mass at a fixed collision rate, although we caution that this could be due to sample selection effects. Metallicity is found to be a less important predictor of LMXB probability than collision rate, mass, or distance, even though LMXB clusters have a higher metallicity on average. This may be due to the interaction of location and metallicity: a sample of M31 LMXBs with a greater range in galactocentric distance would likely contain more metal-poor clusters and make it possible to disentangle the two effects. Description: A search of the Hubble Legacy Archive (HLA) in 2012 June for WFPC2 or Advanced Camera for Surveys (ACS) images yielded 29 M31 globular clusters for which structural parameters had not previously been analyzed in the context of Low-Mass X-ray Binaries (LMXBs) association. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 50 51 New HST data for 29 globular clusters with Low-Mass X-ray Binaries (LMXB) table3.dat 136 204 Model-fitting results -------------------------------------------------------------------------------- See also: J/AJ/146/20 : Structural parameters for 79 GCs in M31 (Wang+, 2013) J/A+A/531/A155 : HST photometry in six M31 globular clusters (Perina+, 2011) J/AJ/141/61 : Star clusters in M31. II. (Caldwell+, 2011) J/ApJ/725/200 : An updated catalog of M31 globular-like clusters (Fan+, 2010) J/AJ/137/94 : Star clusters in M31 (Caldwell+, 2009) J/MNRAS/392/L55 : GCs in M31 from K-band photometry (Peacock+, 2009) J/A+A/471/127 : New globular clusters in M 31 (Galleti+, 2007) J/AJ/133/2764 : M31 globular clusters structural parameters (Barmby+, 2007) J/ApJS/161/304 : Star clusters in the MW and satellites (McLaughlin+, 2005) J/A+A/373/63 : M31 second ROSAT PSPC survey (Supper+, 2001) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Globular cluster name (G1) 12- 16 A5 --- Cam Camera (ACS or WFPC2) 18- 22 A5 --- Flt Filter (F336W, F435W, F475W, F555W, F606W, F814W) 24- 28 I5 s Exp Exposure time 30- 33 F4.2 mag E(B-V) Reddening (1) 35- 39 F5.2 mag (V-m)0 Extinction-corrected color (2) 41- 45 F5.2 [Sun] [Fe/H] Metallicity (3) 47- 50 F4.2 Msun/Lsun M/Lv Ratio of total mass to visual luminosity (4) -------------------------------------------------------------------------------- Note (1): From Fan et al. (2010, cat. J/ApJ/725/200), except for B091D, BH16, and NB21 from Caldwell et al. (2011, cat. J/AJ/141/61), and B159 from Fan et al. (2008MNRAS.385.1973F). Note (2): Where m is the observed-band magnitude. Used to convert measurements to the V band (see Section 2.1). Note (3): From Caldwell et al. (2011, cat. J/AJ/141/61). Note (4): Computed using metallicity-dependent M/Lv for an age of 13Gyr (see Section 2.1). -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 --- Name Globular cluster name (G1) 12- 15 A4 --- Cam Camera (WFC or WFPC) 17- 20 A4 --- Flt Filter (F336, F435, F475, F555, F606, F814) 22- 23 I2 --- Np Number of points 25- 27 A3 --- Mod Model code (1) 29- 35 F7.2 --- chi2 Unreduced {Chi}^2^ of best-fitting model 37- 43 F7.2 Lsun/pc2 Ibkg Model-fit background intensity 45- 50 F6.2 Lsun/pc2 e_Ibkg Uncertainty in Ibkg 52- 56 F5.2 --- W0 ? Model-fit central potential 58- 61 F4.2 --- E_W0 ? Upper 68% confidence interval in W0 63- 66 F4.2 --- e_W0 ? Lower 68% confidence interval in W0 68- 72 F5.2 --- c Model-fit concentration (2) 74- 77 F4.2 --- E_c Upper 68% confidence interval in c 79- 82 F4.2 --- e_c Lower 68% confidence interval in c 84- 88 F5.2 mag/arcsec2 mu0 Model-fit central surface brightness (3) 90- 93 F4.2 mag/arcsec2 E_mu0 Upper 68% confidence interval in mu0 95- 98 F4.2 mag/arcsec2 e_mu0 Lower 68% confidence interval in mu0 100-105 F6.3 [arcsec] logr0 Log of fitted angular scale radius 107-111 F5.3 [arcsec] E_logr0 Upper 68% confidence interval in logr0 113-117 F5.3 [arcsec] e_logr0 Lower 68% confidence interval in logr0 119-124 F6.3 pc logR0 Log of physical scale radius 126-130 F5.3 pc E_logR0 Upper 68% confidence interval in logR0 132-136 F5.3 pc e_logR0 Lower 68% confidence interval in logR0 -------------------------------------------------------------------------------- Note (1): Model code defined as follows: K66 = King (1966AJ.....71...64K) model. This is the "standard" model used when describing globular clusters and is characterized by a single-mass, isotropic, isothermal sphere; W = The Wilson (1975AJ.....80..175W) model is a slight modification of the K66 model with an extra term in the distribution function that causes Wilson models to be more spatially extended; PL = The "Power-Law with core" model of Elson et al. (1987ApJ...323...54E) is often used to describe young clusters; K62 = The King (1962AJ.....67..471K) model is an analytical parameterization of the surface brightness profile sometimes used in studies of marginally resolved clusters. Note (2): c=log(r_t_/r_0_) (r_0_=fitted scale radius, r_t_|I(r_t_)= 0). Note (3): Extinction-corrected in the native bandpass of the data. -------------------------------------------------------------------------------- Global notes: Note (G1): B091D-D057 is a probable misprint for B091D-D058 (note from CDS). History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 21-Jul-2014