J/ApJ/743/167 Radial velocities and membership in Pal 13 (Bradford+, 2011)
Structure and dynamics of the globular cluster Palomar 13.
Bradford J.D., Geha M., Munoz R.R., Santana F.A., Simon J.D., Cote P.,
Stetson P.B., Kirby E., Djorgovski S.G.
<Astrophys. J., 743, 167 (2011)>
=2011ApJ...743..167B 2011ApJ...743..167B
ADC_Keywords: Clusters, globular ; Radial velocities ; Photometry
Keywords: dark matter - galaxies: kinematics and dynamics -
globular clusters: individual (Palomar 13)
Abstract:
We present Keck/DEIMOS spectroscopy and Canada-France-Hawaii
Telescope/MegaCam photometry for the Milky Way globular cluster
Palomar 13. We triple the number of spectroscopically confirmed
members, including many repeat velocity measurements. Palomar 13 is
the only known globular cluster with possible evidence for dark
matter, based on a Keck/High Resolution Echelle Spectrometer 21 star
velocity dispersion of σ=2.2±0.4km/s. We reproduce this
measurement, but demonstrate that it is inflated by unresolved binary
stars. For our sample of 61 stars, the velocity dispersion is
σ=0.7+0.6-0.5km/s. Combining our DEIMOS data with literature
values, our final velocity dispersion is σ=0.4+0.4-0.3km/s.
We determine a spectroscopic metallicity of [Fe/H]=-1.6±0.1 dex,
placing a 1σ upper limit of σ[Fe/H]∼0.2dex on any
internal metallicity spread. We determine Palomar 13's total
luminosity to be MV=-2.8±0.4, making it among the least luminous
known globular clusters.
Description:
We select spectroscopic targets in Pal 13 based on CFHT CFH12K and
Keck/Low Resolution Imaging Spectrometer (LRIS) imaging as described
in Cote et al. (2002ApJ...574..783C 2002ApJ...574..783C). We supplement these data at
large radius with wider field photometry from P. Stetson's online
database (http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/community/STETSON/
standards/).
The spectroscopic data were taken with the Keck II 10m telescope and
the DEIMOS spectrograph. Eight multislit masks were observed in Pal 13
in 2008 September, with a ninth mask obtained in 2009 October. The
wavelength region covering 6400-9100Å for a resolution R=6000
(FWHM∼1.37Å).
After our spectroscopic observations, we obtained significantly deeper
images of Pal 13 using the CFHT MegaCam imager. Pal 13 was observed on
the night of UT 2009 July 22 in both the g- and r-bands.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 96 375 Keck/DEIMOS velocity measurements for Palomar 13
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See also:
B/cfht : Log of CFHT Exposures (CADC, 1979-)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
VII/103 : Galactic Globular Clusters (Monella 1985)
J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)
J/ApJS/180/54 : GC candidates in ACS Virgo survey. (Jordan+, 2009)
J/ApJS/161/304 : Star clusters in the MW & satellites (McLaughlin+, 2005)
J/AJ/128/3019 : Pal 13 blue stragglers and MS binaries (Clark+, 2004)
J/A+A/419/533 : Pal 13 UBV, proper motions and RVs (Blecha+, 2004)
J/AJ/121/935 : UBV and proper motions of Palomar 13 (Siegel+, 2001)
J/A+AS/121/499 : BV and rg photometry of Pal 13 (Borissova+ 1997)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [0/299] Index number (1)
5- 17 A13 --- Name Source name
19- 20 I2 h RAh [23] Hour of Right Ascension (J2000)
22- 23 I2 min RAm [5/7] Minute of Right Ascension (J2000)
25- 29 F5.2 s RAs Second of Right Ascension (J2000)
31 A1 --- DE- [+] Sign of the Declination (J2000)
32- 33 I2 deg DEd [12] Degree of Declination (J2000)
35- 36 I2 arcmin DEm [36/56] Arcminute of Declination (J2000)
38- 42 F5.2 arcsec DEs Arcsecond of Declination (J2000)
44- 48 F5.2 mag rmag [14.6/22.87] CFHT/Megacam r band magnitude
50- 54 F5.2 mag g-r CFHT/Megacam (g-r) color index
56- 62 F7.2 km/s [-508.93/112.59] Average heliocentric radial
velocity (2)
64- 67 F4.2 km/s e_ Uncertainty in
69- 75 F7.2 km/s HRVD ? DEIMOS heliocentric radial velocity
77- 80 F4.2 km/s e_HRVD ? Uncertainty in HRVD
82- 87 F6.2 km/s HRVH ? HIRES heliocentric radial velocity (3)
89- 92 F4.2 km/s e_HRVH ? Uncertainty in HRVH
94 A1 --- fM [NY] "full" member status (Y=Yes; N=No) (4)
96 A1 --- cM [NY] "clean" member status (Y=Yes; N=No) (4)
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Note (1): Each sub-row lists the subsequent DEIMOS and HIRES individual
epoch velocity measurements.
Note (2): Weighted average of DEIMOS and HIRES heliocentric velocities.
Note (3): From Cote et al. (2002ApJ...574..783C 2002ApJ...574..783C). Note that the HIRES
velocities have been shifted by +0.5km/s for zero-point alignment to
this study.
Note (4): The color-magnitude selection and velocity cut (±22km/s around
the systemic velocity of 26.2km/s) and metallicity leaves a "full"
sample of 89 candidate members (those having a "Y" in fM).
Another way to identify foreground stars is via proper motions. Proper
motions are available for 69 out of 89 candidate members (78%) from
Siegel et al. (2001, Cat. J/AJ/121/935). This leaves 66 candidate
member stars of Pal 13 in the "cleaned" sample (those having a "Y" in
cM). See Sections 2 and 3 for further explanations.
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History:
* 15-May-2013: From electronic version of the journal
(minutes of declination in error)
* 15-Jul-2013: new version of table3 with corrected declinations
(from Jeremy Bradford)
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-May-2013