J/ApJ/760/87 Globular clusters of M60 with HST (Strader+, 2012)
Deep Chandra monitoring observations of NGC 4649.
II. Wide-field Hubble Space Telescope imaging of the globular clusters.
Strader J., Fabbiano G., Luo B., Kim D.-W., Brodie J.P., Fragos T.,
Gallagher J.S., Kalogera V., King A., Zezas A.
<Astrophys. J., 760, 87 (2012)>
=2012ApJ...760...87S 2012ApJ...760...87S
ADC_Keywords: Photometry, HST ; Galaxies, nearby ; Clusters, globular ;
Morphology
Keywords: galaxies: individual (NGC 4649) - galaxies: star clusters: general -
globular clusters: general
Abstract:
We present g and z photometry and size estimates for globular clusters
(GCs) in the massive Virgo elliptical NGC 4649 (M60) using a
five-pointing Hubble Space Telescope/Advanced Camera for Surveys
mosaic. The metal-poor GCs show a monotonic negative metallicity
gradient of -0.43±0.10dex per dex in radius over the full radial
range of the data, out to ∼24kpc. There is evidence for substantial
color substructure among the metal-rich GCs. The metal-poor GCs have
typical sizes ∼0.4pc larger than the metal-rich GCs out to large
galactocentric distances (≳20kpc), favoring an intrinsic explanation
for the size difference rather than projection effects. There is no
clear relation between half-light radius and galactocentric distance
beyond ∼15kpc, suggesting that the sizes of GCs are not generically
set by tidal limitation. Finally, we identify ∼20 candidate
ultracompact dwarfs that extend down to surprisingly faint absolute
magnitudes (Mz~-8.5), and may bridge the gap between this class and
"extended clusters" in the Local Group. Three of the brighter
candidates have published radial velocities and can be confirmed as
bona fide ultracompact dwarfs; follow-up spectroscopy will determine
the nature of the remainder of the candidates.
Description:
The ACS observations were arranged in a five-pointing mosaic with
slight overlap around a central archival pointing from the ACS Virgo
Cluster Survey (Cote et al. 2004, Cat. J/ApJS/153/223). Together,
these data cover the sensitive portion of the Chandra ACIS field of
view. Each pointing consists of 888s of total exposure time in F475W
and 1278s in F850LP (henceforth called g and z).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 1603 Globular cluster candidates in NGC 4649
table2.dat 28 23 Candidate ultracompact dwarf galaxies in NGC 4649
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
J/ApJS/204/14 : Deep Chandra observations of NGC 4649. Paper I. (Luo+, 2013)
J/A+A/525/A19 : Phot. of globulars in early galaxies (Chies-Santos+, 2011)
J/MNRAS/416/155 : GCs in five early-type galaxies (Faifer+, 2011)
J/ApJ/690/512 : LMXBs & globulars in early-type galaxies (Humphrey, 2009)
J/ApJS/180/54 : GC candidates in ACS Virgo survey. (Jordan+, 2009)
J/ApJ/674/857 : RVs and CT1 magnitudes in M60 galaxy (Lee+, 2008)
J/ApJS/171/101 : GCs in the ACS Virgo cluster survey (Jordan+, 2007)
J/ApJ/662/525 : LMXBs in globular clusters of 5 galaxies (Kundu+, 2007)
J/MNRAS/355/608 : NGC 4649 (M60) globular clusters (Forbes+, 2004)
J/ApJS/153/223 : ACS Virgo Cluster Survey. I. (Cote+, 2004)
J/AJ/90/1681 : The Virgo Cluster Catalog (VCC) (Binggeli+, 1985)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Globular cluster candidate identifier
(<[SFL2012] ANNN> in Simbad)
6- 16 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
18- 27 F10.7 deg DEdeg Declination in decimal degrees (J2000)
29- 34 F6.3 mag gmag The g band AB magnitude (HST/ACS F475W)
36- 40 F5.3 mag e_gmag Error in gmag
42- 47 F6.3 mag zmag The z band AB magnitude (HST/ACS F850LP)
49- 53 F5.3 mag e_zmag Error in zmag
55- 59 F5.3 mag g-z The (g-z) color index
61- 65 F5.3 mag e_g-z Error in g-z
67- 71 F5.2 pc rhg ? Cluster g band measured radius
73- 76 F4.2 pc e_rhg ? Random measurement error in rhg
78- 82 F5.2 pc rhz ? Cluster z band measured radius
84- 87 F4.2 pc e_rhz ? Random measurement error in rhz
89- 93 F5.2 pc rhavg ? Weighted average g and z band radius
95- 98 F4.2 pc e_rhavg ? Random measurement error in rhavg
100 A1 --- J? [Y ] In Jordan et al. catalog? (1)
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Note (1): Whether the object is present in the catalog of globular cluster
candidates in Vorgo survey (Jordan et al. 2009, Cat. J/ApJS/180/54),
<[JPB2009] DDD.ddddddd+DD.ddddddd> in Simbad
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- f_ID [s] s: spectroscopically confirmed object
3- 6 A4 --- ID Ultra compact dwarf galaxy candidate identifier
8- 13 F6.2 mag zMag Absolute z-band magnitude
15- 18 F4.2 mag g-z The (g-z) color index
20- 23 F4.1 pc rh Half-light radius
25- 28 F4.1 kpc Dist Projected galactocentric distance
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History:
From electronic version of the journal
References:
Luo et al. Paper I. 2013ApJS..204...14L 2013ApJS..204...14L Cat. J/ApJS/204/14
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 25-Apr-2013