J/AJ/143/87 IRAC photometry of massive M31 globular clusters (Barmby+, 2012)
Comparing mid-infrared globular cluster colors with population synthesis models.
Barmby P., Jalilian F.F.
<Astron. J., 143, 87 (2012)>
=2012AJ....143...87B 2012AJ....143...87B
ADC_Keywords: Galaxies, nearby ; Clusters, globular ; Photometry, infrared ;
Abundances, [Fe/H]
Keywords: galaxies: individual: M31 - galaxies: star clusters: general -
infrared: stars - stars: Population II
Abstract:
Several population synthesis models now predict integrated colors of
simple stellar populations in the mid-infrared bands. To date, the
models have not been extensively tested in this wavelength range. In a
comparison of the predictions of several recent population synthesis
models, the integrated colors are found to cover approximately the
same range but to disagree in detail, for example, on the effects of
metallicity. To test against observational data, globular clusters
(GCs) are used as the closest objects to idealized groups of stars
with a single age and single metallicity. Using recent mass estimates,
we have compiled a sample of massive, old GCs in M31 which contain
enough stars to guard against the stochastic effects of small-number
statistics, and measured their integrated colors in the Spitzer/IRAC
bands. Comparison of the cluster photometry in the IRAC bands with the
model predictions shows that the models reproduce the cluster colors
reasonably well, except for a small (not statistically significant)
offset in [4.5]-[5.8]. In this color, models without circumstellar
dust emission predict bluer values than are observed. Model
predictions of colors formed from the V band and the IRAC 3.6 and
4.5{micro}m bands are redder than the observed data at high
metallicities and we discuss several possible explanations. In
agreement with model predictions, V-[3.6] and V-[4.5] colors are found
to have metallicity sensitivity similar to or slightly better than
V-Ks.
Description:
The M31 bulge and some of the brightest M31 clusters had individual
deep Spitzer Space Telescope/IRAC observations as part of PID 3400
(PI: M. Rich). These images also include a number of additional
clusters fortuitously located near the target clusters. We retrieved
the data from the Spitzer Heritage Archive. The main observational
data set for the M31 clusters comprises the IRAC mosaics taken as part
of PID 3126 (described in Barmby et al., 2006ApJ...650L..45B 2006ApJ...650L..45B).
The final sample of massive M31 globulars analyzed here has a total of
52 members. 11 clusters were imaged in all four bands in the deep PID
3400 data, 41 were imaged only on the shallow M31 mosaics.
We also measure the M31 GC magnitudes on the 2MASS "6x" Atlas images
(Cat. II/281). We retrieved 2MASS images of the M31 GCs and used these
to measure aperture magnitudes with the same large photometric and
background apertures used for the IRAC data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 96 52 IRAC photometry for massive M31 globular clusters
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See also:
II/281 : 2MASS 6X Point Source Working Database / Catalog (Cutri+ 2006)
J/A+A/531/A155 : HST photometry in six M31 globular clusters (Perina+, 2011)
J/AJ/141/61 : Star clusters in M31. II. (Caldwell+, 2011)
J/PASP/122/745 : HST WFPC2 star clusters in M31. III. (Hodge+, 2010)
J/ApJ/725/200 : An updated catalog of M31 globular-like clusters (Fan+, 2010)
J/AJ/139/1438 : SED and age estimates of 104 M31 globulars (Wang+, 2010)
J/MNRAS/402/803 : M31 globular cluster system (Peacock+, 2010)
J/MNRAS/392/L55 : Globulars in M31 from K-band photometry (Peacock+, 2009)
J/A+A/507/1375 : HST/ACS VI data of M31 globular clusters (Perina+, 2009)
J/ApJ/707/89 : Variation of mid-IR extinction (Gao+, 2009)
J/AJ/137/94 : Star clusters in M31 (Caldwell+, 2009)
J/ApJ/687/230 : Survey of M31 with Spitzer (Mould+, 2008)
J/ApJS/177/174 : Star clusters in M31 (Narbutis+, 2008)
J/ApJS/173/643 : GALEX UV photometry of M31 Globular Clusters (Rey+, 2007)
J/AJ/133/2764 : M31 globular clusters structural parameters (Barmby+, 2007)
J/A+A/471/127 : New globular clusters in M 31 (Galleti+, 2007)
J/A+A/449/143 : Photometry of M31 globular cluster candidates (Ma+, 2006)
J/AJ/131/1416 : IR Photometry of nearby globular clusters (Nantais+, 2006)
J/A+A/416/917 : Revised Bologna Catalog of M31 globulars (Galleti+, 2004)
J/AJ/123/2490 : RV and [Fe/H] of M31 globular cluster system (Perrett+, 2002)
J/ApJ/559/851 : Young star cluster candidates in M31 (Williams+, 2001)
J/AJ/122/2458 : M31 globular clusters from HST (Barmby+, 2001)
J/AJ/119/727 : M31 globular clusters photometry (Barmby+, 2000)
J/AcA/48/455 : Globular Clusters in M31 and M33 (Mochejska+, 1998)
J/AJ/114/1488 : Globulars in M31 (Holland+ 1997)
http://www.bo.astro.it/M31 : M31 Globular Clusters Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name Globular cluster name (1)
9- 13 F5.2 mag [3.6] [11.03/13.72] Spitzer/IRAC 3.6µm 3.66" aperture
flux in Vega system, extinction corrected (2) (4)
15- 18 F4.2 mag e_[3.6] Uncertainty on [3.6]
20- 24 F5.2 mag [4.5] [11.11/13.74] Spitzer/IRAC 4.5µm 3.66" aperture
flux in Vega system, extinction corrected (4) (2)
26- 29 F4.2 mag e_[4.5] Uncertainty on [4.5]
31- 35 F5.2 mag [5.8] [10.95/13.73] Spitzer/IRAC 5.8µm 3.66" aperture
flux in Vega system, extinction corrected (2) (4)
37- 40 F4.2 mag e_[5.8] Uncertainty on [5.8]
42- 46 F5.2 mag [8.0] [10.67/13.74] Spitzer/IRAC 8.0µm 3.66" aperture
flux in Vega system, extinction corrected (2) (4)
48- 51 F4.2 mag e_[8.0] Uncertainty on [8.0]
53- 57 F5.2 mag Ks [10.61/13.16]? 2MASS Ks photometry (3) (5)
59 A1 --- f_Ks [cd] globular near a bright source (6)
61- 64 F4.2 mag e_Ks ? Uncertainty on FKs
66- 70 F5.2 mag [3.6]a [10.55/12.98]? Spitzer/IRAC 3.6µm 12.2" aperture
flux in Vega system, extinction corrected (4) (3)
72- 75 F4.2 mag e_[3.6]a ? Uncertainty on [3.6]a
77- 81 F5.2 mag [4.5]a [10.57/12.95]? Spitzer/IRAC 4.5µm 12.2" aperture
flux in Vega system, extinction corrected (3) (4)
83- 86 F4.2 mag e_[4.5]a ? Uncertainty on [4.5]a
88- 91 F4.1 [Sun] [Fe/H] Metallicity
93- 96 F4.2 mag E(B-V) The E(B-V) color excess (7)
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Note (1): Following the convention of Galleti et al. (2004, Cat. J/A+A/416/917).
Note (2): Flux measured in circular apertures of radii 3.66".
Note (3): Flux measured in circular apertures of radii 12.2".
Note (4): For the four IRAC bands, we correct for extinction using the
bandpass-averaged extinction values of Indebetouw et al.
(2005ApJ...619..931I 2005ApJ...619..931I), as tabulated in Gao et al. 2009 (J/ApJ/707/89).
Note (5): For the 2MASS Ks band, we assume the extinction value from
Cambresy et al. (2002AJ....123.2559C 2002AJ....123.2559C).
Note (6): Flag as follows:
c = Cluster B091D is located near a much brighter star; adequate
large-aperture photometry was not possible.
d = Clusters B124 and B131 are located near the bright bulge of M31;
adequate large-aperture photometry was not possible.
Note (7): Values from Caldwell et al. (2011, Cat. J/AJ/141/61).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 27-May-2013