J/MNRAS/436/1172 Globular Clusters of NGC 4278 in SLUGGS (Usher+, 2013)
The SLUGGS survey: wide field imaging of the globular cluster system
of NGC 4278.
Usher C., Forbes D.A., Spitler L.R., Brodie J.P., Romanowsky A.J.,
Strader J., Woodley K.A.
<Mon. Not. R. Astron. Soc., 436, 1172-1190 (2013)>
=2013MNRAS.436.1172U 2013MNRAS.436.1172U
ADC_Keywords: Clusters, globular ; Photometry ; Radial velocities
Keywords: Globular cluster: general - galaxies: individual: NGC 4278 -
galaxies: star clusters: general
Abstract:
We use multipointing Hubble Space Telescope Advanced Camera for
Surveys and wide field Subaru Suprime-Cam imaging to study the
globular cluster system of the L* elliptical galaxy NGC 4278. We have
also obtained a handful of new globular cluster spectra with the Keck
Deep Imaging Multi-Object Spectrograph. We determine the globular
cluster surface density profile and use it to calculate the total
number of globular clusters, finding the system to be slightly more
populous than average for galaxies of its luminosity. We find clear
evidence for bimodality in the globular cluster colour distribution
and for a colour-magnitude relation in the blue subpopulation (a 'blue
tilt'). We also find negative radial colour gradients in both colour
subpopulations of equal strength which are similar in strength to
those reported in other galaxies. The sizes of NGC 4278's globular
clusters decrease with redder colours and increase with galactocentric
radius. The ratio of the sizes of blue to red globular clusters is
independent of galactocentric radius demonstrating that internal
effects are responsible for the size difference with colour.
Description:
As part of the SLUGGS (sluggs.swin.edu.au) survey of globular clusters
(GCs) around early-type galaxies we have used archival HST ACS and
Subaru Suprime-Cam imaging to study the GC system of the giant
elliptical galaxy NGC 4278. We used magnitude, colour and size cuts to
select candidate GCs from the ACS imaging and used magnitude and
colour-colour cuts to select candidates from from the Suprime-Cam
imaging. We study the spatial, colour and size distributions of the
candidates. We also obtained a number of spectra of GC candidates with
DEIMOS on Keck adding a handful of confirmed GCs and ultra compact
dwarfs to the sample of Pota et al. (2013MNRAS.428..389P 2013MNRAS.428..389P, Cat.
J/MNRAS/428/389). Metallicities were measured using the technique of
Usher et al. (2012MNRAS.426.1475U 2012MNRAS.426.1475U, Cat. J/MNRAS/426/1475).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 114 716 ACS globular cluster candidates
table5.dat 115 1146 Suprime-Cam globular cluster candidates
tablea1.dat 127 360 Spectroscopically confirmed objects
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See also:
J/MNRAS/426/1475 : CaT in 903 globular clusters (Usher+, 2012)
J/MNRAS/428/389 : SLUGGS globular clusters in early-type galaxies (Pota+ 2013)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [acs_]
5- 8 I04 --- ACS [11/2507] ACS designation (NNNN)
10- 19 F10.6 deg RAdeg Right Ascension in degrees (J2000)
21- 29 F9.6 deg DEdeg Declination in degrees (J2000)
31- 34 F4.2 mag g-z ACS g-z (F475W-F850LP) colour index
36- 39 F4.2 mag e_g-z rms uncertainty on g-z
41- 45 F5.2 mag zmag HST/ACS F850LP (z band) magnitude
47- 50 F4.2 mag e_zmag rms uncertainty on zmag
52- 55 F4.1 pc rhl ACS half light radius
57- 59 F3.1 pc e_rhl rms uncertainty on rhl
61- 67 F7.2 km/s RV ? Radial velocity, or redshift (G2)
69- 70 I2 km/s e_RV ? rms uncertainty on RV
72- 76 F5.2 [Sun] [Z/H] ? Metallicity based on Calcium triplet
78- 81 F4.2 [Sun] e_[Z/H] ? Error on [Z/H] (lower value)
83- 86 F4.2 [Sun] E_[Z/H] ? Error on [Z/H] (upper value)
88- 95 A8 --- --- [NGC4278_]
96-102 A7 --- Name Spectroscopic designation (G1)
104-107 A4 --- --- [sub_]
108-112 I05 --- SuName [1224/57791]? If Suprime-Cam candidate,
Suprime-Cam designation (NNNNN)
114 A1 --- Cl [G] G = spectroscopically confirmed galaxy
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [sub_]
5- 9 I05 --- SuName [1224/57791] Suprime-Cam designation (NNNNN)
11- 20 F10.6 deg RAdeg Right Ascension in degrees (J2000)
22- 30 F9.6 deg DEdeg Declination in degrees (J2000)
32- 35 F4.2 mag B-V ? Suprime-Cam B-V colour index
37- 40 F4.2 mag e_B-V ? rms uncertainty on B-V
42- 45 F4.2 mag V-I ? Suprime-Cam V-I colour index
47- 50 F4.2 mag e_V-I ? rms uncertainty on V-I
52- 56 F5.2 mag Imag ? Suprime-Cam I band magnitude
58- 61 F4.2 mag e_Imag ? rms uncertainty on Imag
63- 69 F7.2 km/s RV ? Radial velocity (G2)
71- 72 I2 km/s e_RV ? rms uncertainty on RV
74- 78 F5.2 --- [Z/H] ? Calcium triplet based metallicity
80- 83 F4.2 --- e_[Z/H] ? Error on [Z/H] (lower value)
85- 88 F4.2 --- E_[Z/H] ? Error on [Z/H] (upper value)
90- 97 A8 --- --- [NGC4278_]
98-104 A7 --- Name Spectroscopic designation (G1)
106-109 A4 --- --- [acs_]
110-113 I04 --- ACS [11/2507]? if ACS candidate,
ACS designation (NNNN)
115 A1 --- Cl [GS] G = spectroscopically confirmed galaxy,
S = spectroscopically confirmed star
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- --- [NGC4278_]
9- 15 A7 --- Name Designation (G1)
17- 26 F10.6 deg RAdeg Right Ascension in degrees (J2000)
28- 36 F9.6 deg DEdeg Declination in degrees (J2000)
38- 41 F4.2 mag g-z ? ACS g-z colour index
43- 46 F4.2 mag e_g-z ? rms uncertainty on g-z
48- 52 F5.2 mag zmag ? ACS z band magnitude
54- 57 F4.2 mag e_zmag ? rms uncertainty on zmag
59- 62 F4.1 pc rhl ? ACS half light radius if the object was at
our adopted distance of 15.6Mpc
64- 67 F4.1 pc e_rhl ? rms uncertainty in ACS half light radius
69- 73 F5.2 mag B-V ? Suprime-Cam B-V colour index
75- 78 F4.2 mag e_B-V ? rms uncertainty on B-V
80- 84 F5.2 mag V-I ? Suprime-Cam V-I colour index
86- 89 F4.2 mag e_V-I ? rms uncertainty on V-I
91- 95 F5.2 mag Imag ? Suprime-Cam I band magnitude
97-100 F4.2 mag e_Imag ? rms uncertainty on Imag
102-108 F7.2 km/s RV Radial velocity (G2)
110-111 I2 km/s e_RV ? rms uncertainty on RV
113-117 F5.2 [Sun] [Z/H] ? Calcium triplet based metallicity
119-122 F4.2 [Sun] e_[Z/H] ? Error on [Z/H] (lower value)
124-127 F4.2 [Sun] E_[Z/H] ? Error on [Z/H] (upper value)
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Global notes:
Note (G1): Continuation of designations from Pota et al. 2013 (J/MNRAS/428/389):
* NGC4278_GCNNN for globular cluster,
* NGC4278_galNN for galaxy and
* NGC4278_starsNN for stars.
Note (G2): For galaxies rather than the radial velocity, the estimated
redshift is given.
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Acknowledgements:
Christopher Usher, cusher(at)astro.swin.edu.au
(End) Christopher Usher [Swinburne], Patricia Vannier [CDS] 22-Oct-2014