J/ApJ/827/12 HSTPROMO catalogs of GCs. IV. Blue straggler stars (Baldwin+, 2016)
Hubble Space Telescope proper motion (HSTPROMO) catalogs of galactic globular
clusters.
IV. Kinematic profiles and average masses of blue straggler stars.
Baldwin A.T., Watkins L.L., van der Marel R.P., Bianchini P., Bellini A.,
Anderson J.
<Astrophys. J., 827, 12-12 (2016)>
=2016ApJ...827...12B 2016ApJ...827...12B (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Velocity dispersion ; Stars, masses ;
Abundances, [Fe/H]
Keywords: blue stragglers; globular clusters: individual;
proper motions; stars: kinematics and dynamics
Abstract:
We make use of the Hubble Space Telescope proper-motion catalogs
derived by Bellini et al. (Paper I, 2014, J/ApJ/797/115) to produce
the first radial velocity dispersion profiles σ(R) for blue
straggler stars (BSSs) in Galactic globular clusters (GCs), as well as
the first dynamical estimates for the average mass of the entire BSS
population. We show that BSSs typically have lower velocity
dispersions than stars with mass equal to the main-sequence turnoff
mass, as one would expect for a more massive population of stars.
Since GCs are expected to experience some degree of energy
equipartition, we use the relation σ∝M-η, where
η is related to the degree of energy equipartition, along with our
velocity dispersion profiles to estimate BSS masses. We estimate η
as a function of cluster relaxation from recent Monte Carlo cluster
simulations by Bianchini+ (2016MNRAS.458.3644B 2016MNRAS.458.3644B) and then derive an
average mass ratio MBSS/MMSTO=1.50±0.14 and an average mass
MBSS=1.22±0.12M☉ from 598 BSSs across 19 GCs. The final
error bars include any systematic errors that are random between
different clusters, but not any potential biases inherent to our
methodology. Our results are in good agreement with the average mass
of MBSS=1.22±0.06M☉ for the 35 BSSs in Galactic GCs in the
literature with properties that have allowed individual mass
determination.
Description:
Although Paper I (Bellini+, 2014, J/ApJ/797/115) presented HST
proper-motion catalogs for 22 Galactic globular clusters (GCs), in
this paper we make use of the catalogs for only 19 of these clusters.
NGC6535 and NGC7099 (M30) are excluded from our analysis as our
catalogs contain relatively few stars for these clusters and we do not
detect enough blue straggler stars (BSSs) in either cluster to make a
meaningful estimate of their velocity dispersion. We also exclude
NGC6715 (M54) due to the risk of contamination from the Sagittarius
dwarf spheroidal galaxy.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 41 65 Blue straggler radial dispersion profiles
table3.dat 91 19 Properties and results for Galactic globular clusters
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/ApJ/816/70 : Spectra of 3 NGC104 member stars (Ferraro+, 2016)
J/ApJ/812/149 : HSTPROMO. III. Dynamical distances (Watkins+, 2015)
J/ApJ/803/29 : HSTPROMO catalogs. II. Kinematic profiles (Watkins+, 2015)
J/ApJ/801/67 : Grid of binary colors in M30 (NGC7099) (Xin+, 2015)
J/ApJ/797/115 : HSTPROMO I. Observations and NGC7078 results (Bellini+, 2014)
J/ApJ/754/91 : Abundances and velocities of NGC 6397 stars (Lovisi+, 2012)
J/ApJ/732/108 : Abundances of 92 giants in Plaut's window (Johnson+, 2011)
J/ApJ/710/1032 : Proper motions in ω Cen (Anderson+, 2010)
J/AJ/137/3743 : Spectroscopic binary orbits in NGC 188 (Geller+, 2009)
J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)
J/ApJ/677/1069 : Blue stragglers in NGC 6388 (Dalessandro+, 2008)
J/ApJ/663/267 : Blue straggler population of M5 (Lanzoni+, 2007)
J/ApJS/166/249 : Stellar dynamics & proper motions in 47Tuc (McLaughlin+, 2006)
J/ApJ/648/1026 : HST photometry of M5 blue stragglers (Warren+, 2006)
J/ApJ/632/894 : Blue stragglers, HB & turnoff stars in 4 GC (De Marco+, 2005)
J/ApJ/625/156 : FUV-NUV observations of NGC 2808 (Dieball+, 2005)
J/A+A/324/915 : Blue stragglers in M3 (Ferraro+ 1997)
J/AJ/108/1786 : Blue stragglers and variable stars in M3 (Guhathakurta+, 1994)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
4- 7 I4 --- NGC Cluster name
9- 10 I2 --- NBSS [6/14] Number of blue straggler stars in the bin
12- 19 F8.4 arcsec Rad [7/148] Mean radius of the bin
21- 27 F7.4 arcsec e_Rad [1/17] Uncertainty in Rad
29- 34 F6.4 mas/yr sigma [0.04/0.9] Binned velocity dispersion
36- 41 F6.4 mas/yr e_sigma [0.01/0.2] Uncertainty in σ
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [NGC]
4- 7 I4 --- NGC Cluster name
9- 13 F5.2 [Sun] [Fe/H] [-2.4/-0.4] Metallicity (1)
15- 19 F5.2 Gyr Tage [10.7/13] Cluster age (2)
21- 25 F5.1 arcsec cRad [1/143] Core radius (1)
27- 31 F5.2 [Gyr] logTrc [-4.1/0.6] Core relaxation time, log (1)
33- 36 F4.2 [-] lognrel [0.5/5.2] Number of relaxation times,
Tage/Trc, log
38- 41 F4.2 Msun Meq [1.5/3.1] Equipartition mass (3)
43- 46 F4.2 --- eta [0.2/0.4] Equipartition parameter η
48- 51 F4.2 Msun MMSTO [0.7/0.9] Main-sequence turnoff (MSTO) mass
53- 56 F4.2 --- alpha [0.6/1.2] Scale factor α,
α=(MBSS/MMSTO)-η
58- 61 F4.2 --- e_alpha [0.04/0.2] Uncertainty in alpha
63- 66 F4.2 --- f [0.7/2.8] Average blue straggler star mass
(MBSS) as a multiple of MMSTO,
f=MBSS/MMSTO
68- 71 F4.2 --- E_f Upper error on f
73- 76 F4.2 --- e_f Lower error on f
78- 81 F4.2 Msun MBSS [0.5/2.2] Average blue straggler star (BSS)
mass, in solar masses
83- 86 F4.2 Msun E_MBSS Upper error on MBSS
88- 91 F4.2 Msun e_MBSS Lower error on MBSS
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Note (1): From Harris (1996AJ....112.1487H 1996AJ....112.1487H), 2010 edition (2010arXiv1012.3224H 2010arXiv1012.3224H)
found at http://physwww.physics.mcmaster.ca/~harris/mwgc.dat
Note (2): Mostly taken from VandenBerg et al. (2013ApJ...775..134V 2013ApJ...775..134V),
others derived from average VandenBerg et al. (2013ApJ...775..134V 2013ApJ...775..134V)
values and [Fe/H] metallicity; see text for details.
Note (3): Equipartition mass, Meq, above which stars are in complete energy
equipartition (see Bianchini et al. 2016MNRAS.458.3644B 2016MNRAS.458.3644B);
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History:
From electronic version of the journal
References:
Bellini et al. Paper I. 2014ApJ...797..115B 2014ApJ...797..115B Cat. J/ApJ/797/115
Watkins et al. Paper II. 2015ApJ...803...29W 2015ApJ...803...29W Cat. J/ApJ/803/29
Watkins et al. Paper III. 2015ApJ...812..149W 2015ApJ...812..149W Cat. J/ApJ/812/149
Baldwin et al. Paper IV. 2016ApJ...827...12B 2016ApJ...827...12B This catalog
Bellini et al. Paper V. 2017ApJ...844..167B 2017ApJ...844..167B
Libralato et al. Paper VI. 2018ApJ...861...99L 2018ApJ...861...99L Cat. J/ApJ/861/99
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Nov-2016