J/AJ/148/32 Globular cluster candidates in NGC 3115 (Jennings+, 2014)
The SLUGGS survey: HST/ACS mosaic imaging of the NGC 3115 globular cluster
system.
Jennings Z.G., Strader J., Romanowsky A.J., Brodie J.P., Arnold J.A.,
Lin D., Irwin J.A., Sivakoff G.R., Wong K.-W.
<Astron. J., 148, 32 (2014)>
=2014AJ....148...32J 2014AJ....148...32J
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Photometry, ugriz
Keywords: galaxies: individual: NGC 3115 - galaxies: star clusters: general -
globular clusters: general
Abstract:
We present Hubble Space Telescope/Advanced Camera for Surveys
(HST/ACS) g and z photometry and half-light radii Rh measurements of
360 globular cluster (GC) candidates around the nearby S0 galaxy NGC
3115. We also include Subaru/Suprime-Cam g, r, and i photometry of 421
additional candidates. The well-established color bimodality of the GC
system is obvious in the HST/ACS photometry. We find evidence for a
"blue tilt" in the blue GC subpopulation, wherein the GCs in the blue
subpopulation get redder as luminosity increases, indicative of a
mass-metallicity relationship. We find a color gradient in both the
red and blue subpopulations, with each group of clusters becoming
bluer at larger distances from NGC 3115. The gradient is of similar
strength in both subpopulations, but is monotonic and more significant
for the blue clusters. On average, the blue clusters have ∼10% larger
Rhthan the red clusters. This average difference is less than is
typically observed for early-type galaxies but does match that
measured in the literature for the Sombrero Galaxy (M104), suggesting
that morphology and inclination may affect the measured size
difference between the red and blue clusters. However, the scatter on
the Rh measurements is large. We also identify 31 clusters more
extended than typical GCs, which we term ultra-compact dwarf (UCD)
candidates. Many of these objects are actually considerably fainter
than typical UCDs. While it is likely that a significant number will
be background contaminants, six of these UCD candidates are
spectroscopically confirmed as NGC 3115 members. To explore the
prevalence of low-mass X-ray binaries in the GC system, we match our
ACS and Suprime-Cam detections to corresponding Chandra X-ray sources.
We identify 45 X-ray-GC matches: 16 among the blue subpopulation and
29 among the red subpopulation. These X-ray/GC coincidence fractions
are larger than is typical for most GC systems, probably due to the
increased depth of the X-ray data compared to previous studies of GC
systems.
Description:
We have performed photometry and size measurements for 360 globular
cluster candidates in Hubble Space Telescope/Advanced Camera for
Surveys (HST/ACS) imaging of NGC 3115. We have also presented
Suprime-Cam photometry for 421 additional candidates.
The primary data set analyzed in this work is the ACS/WFC mosaic of
NGC 3115 from HST Program 12759 (PI: Jimmy Irwin).
NGC 3115 was imaged in g-, r- and i-band filters on 2008 January 4
using Suprime-Cam on the 8.2m Subaru telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 127 781 Advanced Camera for Surveys (ACS) and SuprimeCam
globular cluster candidate catalog (2017-11-06 version)
table3.dat 66 31 Ultra-compact dwarf candidates in ACS data
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See also:
J/A+A/564/L3 : JHK photometry of NGC 3115 GCs (Cantiello+, 2014)
J/MNRAS/428/389 : SLUGGS globular clusters in early-type galaxies (Pota+, 2013)
J/MNRAS/416/155 : Globular clusters in five early-type galaxies (Faifer+, 2011)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- r_Cluster [AS] A=HST/ACS imaging, S=Suprime-Cam photometry
2- 4 I3 --- Cluster [1/781] Number of the globular cluster candidate
<[JSR2014] ANNN> in Simbad
6- 15 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 26 F10.7 deg DEdeg Declination in decimal degrees (J2000)
28- 34 F7.3 mag F475 ?=-99.99 HST/ACS F475W band magnitude (G1)
36- 42 F7.3 mag e_F475 ?=-99.99 Uncertainty in F475 (G2)
44- 50 F7.3 mag F850 ?=-99.99 HST/ACS F850LP band magnitude (G1)
52- 58 F7.3 mag e_F850 ?=-99.99 Uncertainty in F850 (G2)
60- 66 F7.3 mag gmag ?=-99.99 Subaru/Suprime-Cam g band magnitude
68- 74 F7.3 mag e_gmag ?=-99.99 Uncertainty in gmag
76- 82 F7.3 mag rmag ?=-99.99 Subaru/Suprime-Cam r band magnitude
84- 90 F7.3 mag e_rmag ?=-99.99 Uncertainty in rmag
92- 98 F7.3 mag imag ?=-99.99 Subaru/Suprime-Cam i band magnitude
100-106 F7.3 mag e_imag ?=-99.99 Uncertainty in imag
108-113 F6.2 pc Rad [0/7.2]?=-99.99 Half-light radius
114-117 A4 --- --- [000 ]
119-125 F7.2 km/s HV [71/1192]?=-99.99 Heliocentric velocity (G3)
127 A1 --- X [YN] Indicates whether or not the globular
cluster candidate hosts an X-ray source
(Yes or No)
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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- 3 A3 --- --- [UCD]
4- 5 I2 --- UCD [1/31] Number of the Ultra-Compact Dwarf candidate
<[JSR2014] UCDNNN> in Simbad
7- 15 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
17- 26 F10.7 deg DEdeg Declination in decimal degrees (J2000)
28- 34 F7.3 mag F475 HST/ACS F475W band magnitude (G1)
36- 40 F5.3 mag e_F475 Uncertainty in F475 (G2)
42- 48 F7.3 mag F850 HST/ACS F850LP band magnitude (G1)
50- 54 F5.3 mag e_F850 Uncertainty in F850 (G2)
56- 60 F5.2 pc Rad [8/81] Half-light radius
62- 64 I3 km/s HV [393/878]? Heliocentric velocity (G3)
66 A1 --- X [YN] Indicates whether or not the globular cluster
candidate hosts an X-ray source (Yes or No)
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Global notes:
Note (G1): HST/ACS=Hubble Space Telescope/Advanced Camera for Surveys.
Note (G2): Errors on ACS photometry measurements only include statistical
uncertainties on the initial photometry, and neglect systematic
uncertainties from size-dependent aperture corrections.
Note (G3): If available, from Pota et al. 2013 (cat. J/MNRAS/428/389).
History:
* 15-Oct-2014: From electronic version of the journal, missing negative sign
of declination for the globular cluster candidates observed
with Suprime-Cam in the MRT version of Table2
* 06-Nov-2017: Sign of the declination added at CDS for the Suprime-Cam
observations in Table2
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 15-Oct-2014