J/AJ/150/176 JK photometry of 12 galactic globular clusters (Cohen+, 2015)
Wide field near-infrared photometry of 12 galactic globular clusters:
observations versus models on the red giant branch.
Cohen R.E., Hempel M., Mauro F., Geisler D., Alonso-Garcia J., Kinemuchi K.
<Astron. J., 150, 176 (2015)>
=2015AJ....150..176C 2015AJ....150..176C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry, infrared
Keywords: globular clusters: general -
globular clusters: individual: (NGC 104,NGC 288,NGC 362,NGC 1261,
NGC 1851,NGC 2808,NGC 4833,NGC 5927,NGC 6304,NGC 6496,NGC 6584,
NGC 7099) - infrared: stars
Abstract:
We present wide field near-infrared (near-IR) photometry of 12
Galactic globular clusters, typically extending from the tip of the
cluster red giant branch (RGB) to the main sequence turnoff. Using
recent homogenous values of cluster distance, reddening and
metallicity, the resulting photometry is directly compared to the
predictions of several recent libraries of stellar evolutionary
models. Of the sets of models investigated, Dartmouth and
Victoria-Regina models best reproduce the observed RGB morphology,
albeit with offsets in J-KS color which vary in their significance
in light of all sources of observational uncertainty. Therefore, we
also present newly recalibrated relations between near-IR photometric
indices describing the upper RGB versus cluster iron abundance as well
as global metallicity. The influence of enhancements in alpha elements
and helium are analyzed, and we find that the former affect the
morphology of the upper RGB in accord with model predictions.
Meanwhile, the empirical relations we derive are in good agreement
with previous results, and minor discrepancies can likely be
attributed to differences in the assumed cluster distances and
reddenings. In addition, we present measurements of the horizontal
branch (HB) and RGB bump magnitudes, finding a non-negligible
dependence of the near-IR HB magnitude on cluster metallicity. Lastly,
we discuss the influence of assumed cluster distances, reddenings and
metallicities on our results, finding that our empirical relations are
generally insensitive to these factors to within their uncertainties.
Description:
Observations of our 12 target clusters were obtained with the Infrared
Side Port Imager (ISPI) mounted on the 4m Blanco telescope at Cerro
Tololo Inter-American Observatory. The HAWAII-2 2048*2048 pixel
detector has 0.305''/pixel, giving a field of view 10.25arcmin per
side. Imaging was obtained in the J and KS filters over the course
of three runs between 2008 and 2010 (NGC 104 and NGC 6496 on 2008 Aug
13; NGC 1851 and NGC 288 on 2009 Sep 30; NGC 362, NGC 1261, and NGC
7099 on 2009 Oct 01; NGC 2808 and NGC 6304 on 2010 Apr 28; NGC 4833 on
2010 Apr 29; NGC 5927 and NGC 6584 on 2010 Apr 30), with median seeing
ranging between 0.8'' and 1.4''.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 60 100576 Clusters photometric catalog
table4.dat 91 12 Cluster parameters
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/A+A/563/A76 : CaII triplet EWs in 30 globulars (Mauro+, 2014)
J/A+A/534/A123 : Horizontal branch stars in NGC 2808 (Gratton+, 2011)
J/MNRAS/402/1729 : JHK photometry of 36 GGCs (Valenti+ 2010)
J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/MNRAS/361/272 : JHKs photometry of 4 Bulge GCs (Valenti+, 2005)
J/MNRAS/351/1204 : IR Photometry of 10 GGCs (Valenti+, 2004)
J/A+A/391/945 : HST photometry of 74 GGCs (Piotto+, 2002)
J/A+AS/121/95 : Giant stars abundances in 24 clusters (Carretta+ 1997)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC NGC number of cluster
10- 19 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
21- 30 F10.6 deg DEdeg Declination in decimal degrees (J2000)
32- 38 F7.4 mag Jmag The J band magnitude in 2MASS photometric system
40- 45 F6.4 mag e_Jmag The 1σ uncertainty in Jmag
47- 53 F7.4 mag Ksmag The Ks band magnitude in 2MASS photometric system
55- 60 F6.4 mag e_Ksmag The 1σ uncertainty in Ksmag
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [NGC]
5- 8 I4 --- NGC NGC number of cluster
10- 11 I2 h RAh Hour of Right Ascension (J2000) (1)
13- 14 I2 min RAm Minute of Right Ascension (J2000) (1)
16- 20 F5.2 s RAs Second of Right Ascension (J2000) (1)
22 A1 --- DE- Sign of the Declination (J2000) (1)
23- 24 I2 deg DEd Degree of Declination (J2000) (1)
26- 27 I2 arcmin DEm Arcminute of Declination (J2000) (1)
29- 32 F4.1 arcsec DEs Arcsecond of Declination (J2000) (1)
34- 38 F5.2 mag (m-M)0 Cluster distance modulus (2)
40- 44 F5.3 mag E(B-V) Reddening (2)
46- 50 F5.2 [Sun] [Fe/H] Metallicity from Carretta et al.
(2009A&A...508..695C 2009A&A...508..695C)
52- 55 F4.2 [Sun] e_[Fe/H] Error in [Fe/H]
57- 60 F4.2 [Sun] [a/Fe]1 ? Observed [α/Fe] abundance (3)
62- 64 F3.1 [Sun] [a/Fe]2 Assumed [α/Fe] abundance (4)
66- 68 F3.1 [Sun] e_[a/Fe]2 Error in [a/Fe]2
70- 74 F5.2 [Sun] [M/H] Global metallicity (5)
76- 79 F4.2 [Sun] e_[M/H] Error in [M/H]
81- 85 F5.3 mag V-I The Δ(V-I) index (2)
87- 91 F5.3 mag e_V-I Error in V-I
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Note (1): From Goldsbury et al. (2010AJ....140.1830G 2010AJ....140.1830G).
Note (2): From Dotter et al. (2010ApJ...708..698D 2010ApJ...708..698D).
Note (3): From Carretta et al. (2010A&A...516A..55C 2010A&A...516A..55C).
Note (4): The [α/Fe] value we assume for our isochrone comparison
(discussed below in Section 4.1).
Note (5): Calculated using [M/H]=[Fe/H]+Log(0.638fα+0.362), where
[α/Fe]=[α/Fe] (assumed).
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 20-Apr-2016