J/AJ/141/61 Star clusters in M31. II. (Caldwell+, 2011)
Star clusters in M31.
II. Old cluster metallicities and ages from Hectospec data.
Caldwell N., Schiavon R., Morrison H., Rose J.A., Harding P.
<Astron. J., 141, 61 (2011)>
=2011AJ....141...61C 2011AJ....141...61C
ADC_Keywords: Galaxies, nearby; Associations, stellar ; Abundances, [Fe/H] ;
Radial velocities
Keywords: catalogs - galaxies: individual (M31) -
galaxies: star clusters: general - globular clusters: general
Abstract:
We present new high signal-to-noise spectroscopic data on the M31
globular cluster (GC) system, obtained with the Hectospec multifiber
spectrograph on the 6.5m MMT. More than 300 clusters have been
observed at a resolution of 5Å and with a median S/N of 75 perÅ,
providing velocities with a median uncertainty of 6km/s. The primary
focus of this paper is the determination of mean cluster
metallicities, ages, and reddenings. Metallicities were estimated
using a calibration of Lick indices with [Fe/H] provided by Galactic
GCs.
Description:
Subsequent to the publication of Paper I, more HST images of M31
clusters became available, which were inspected closely to further
aid in the classification of objects in the cluster catalog.
The Web site
http://www.cfa.harvard.edu/oir/eg/m31clusters/M31_Hectospec.html
contains images for all old clusters, young clusters, stars and
background galaxies in the catalog of Paper I and may be profitably
used to view individual cluster images as an adjunct to the
spectroscopy of this paper.
The data were all taken at the MMT with the Hectospec multifiber
spectrograph during the years 2004-2007.
Subsequent to the Hectospec project, a HectoChelle project of many of
these same targets was initiated (J. Strader & N. Caldwell 2011, in
preparation), resulting in more precise velocities which allowed us to
refine the Hectospec velocity zero points.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 323 Results from the spectra of old M31 clusters
table2.dat 66 37 Young and intermediate age clusters called "old"
in Paper I
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See also:
J/AJ/137/94 : Star clusters in M31 (Caldwell+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Object name
11 A1 --- n_Name Individual notes (1)
13 I1 h RAh Right Ascension (J2000)
15- 16 I2 min RAm Right Ascension (J2000)
18- 22 F5.2 s RAs Right Ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 33 F4.1 arcsec DEs Declination (J2000)
35- 38 F4.2 mag E(B-V) The (B-V) color excess
39 A1 --- f_E(B-V) [)] E(B-V) value from other sources (2)
41- 46 F6.1 km/s Vel Velocity from Hectospec
48- 49 I2 km/s e_Vel Uncertainty in Vel
51- 53 F3.1 [Msun] logM ? log of the mass
55- 58 F4.1 [Sun] [Fe/H] ? Metallicity
60- 62 F3.1 [Sun] e_[Fe/H] ? Uncertainty in [Fe/H]
64- 67 F4.1 Gyr Age ? Age (3)
69- 81 A13 --- Notes Additional notes (4)
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Note (1): Flags as follows:
d = The HectoChelle velocity for B070-G133 is significantly different, -222.9
f = The HectoChelle velocity for B132-NB15 is significantly different, 70.8
g = The HectoChelle velocity for B262 is significantly different, -340.3
h = The HectoChelle velocity for NB21 is significantly different, -748.1
i = Velocity for this cluster comes from HectoChelle
j = Probably bound to NGC 205
Note (2):
) = Indicates value was not derived here. Such values are either the mode
of all clusters, 0.13, or come from Barmby et al. (2000, Cat. J/AJ/119/727).
Note (3): Uncertainties are 2Gyr for measured ages.
* A value of exactly 14Gyr means the age could not be determined,
either because the metallicity was lower than -0.95 or the data point fell
off of the grids shown in Figure 10.
* A blank entry means that we have no blue spectrum or HST image of the
object to estimate the age, but that the red spectrum or the ground-based
image do indicate an old age.
Note (4): Additional notes as follows:
e = the spectrum shows weak emission
w = the spectrum was weak
r = we have only a red spectrum. For either this or the "w" case, no age
or metallicity was derived, and it is possible some of these are not
in fact old
x = age could not be determined
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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- 17 A17 --- Name Object Name
19 A1 --- n_Name [bcd] Corrections / addition to Paper I (1)
21 I1 h RAh Right ascension (J2000)
23- 24 I2 min RAm Right ascension (J2000)
26- 30 F5.2 s RAs Right ascension (J2000)
32 A1 --- DE- Declination sign (J2000)
33- 34 I2 deg DEd Declination (J2000)
36- 37 I2 arcmin DEm Declination (J2000)
39- 42 F4.1 arcsec DEs Declination (J2000)
44- 47 F4.2 mag E(B-V) ? Reddening
48 A1 --- n_E(B-V) [)] ) when modal reddening of 0.13 (2)
50- 55 F6.1 km/s Vel ? Velocity
57- 58 I2 km/s e_Vel ? rms uncertainty on Vel
60- 63 F4.2 [Msun] logM ? Log of the mass
64- 66 F3.1 Gyr Age ? Age (3)
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Note (1): Notes as follows:
b = New cluster not listed in Paper I (J/AJ/137/94)
c = The coordinates for B257D-D073 have been corrected from
Paper I (J/AJ/137/94)
d = The velocity for DAO84 in Paper I was incorrect due to an automatic
misidentification of emission lines, and thus this young cluster was
erroneously identified as a background galaxy. We thank Paul Hodge for
helping us identify this error. No other object listed in the tables of
Paper I has this particular error.
Note (2): Where we could not determine new reddenings because the spectra could
not be accurately fluxed (some observations were taken with a malfunctioning
ADC), we use the modal reddening of E(B-V)=0.13.
Note (3): Clusters without ages have spectra too poor to determine one, but the
age is expected to be younger than 3Gyr based on the continuum shape or the
cluster's HST image. Uncertainties in age are roughly a factor of 2.
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History:
From electronic version of the journal
References:
Caldwell et al., Paper I 2009AJ....137...94C 2009AJ....137...94C, Cat. J/AJ/137/94
Morrison et al., Paper III 2011ApJ...726L...9M 2011ApJ...726L...9M
Schiavon et al., Paper IV 2012AJ....143...14S 2012AJ....143...14S
Strader et al. Paper V 2011AJ....142....8S 2011AJ....142....8S
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 25-Jul-2012