J/ApJ/751/6 Radial velocities in ω Cen (Da Costa, 2012)
The dynamics of the outer parts of ω Centauri.
Da Costa G.S.
<Astrophys. J., 751, 6 (2012)>
=2012ApJ...751....6D 2012ApJ...751....6D
ADC_Keywords: Clusters, globular ; Radial velocities ; Equivalent widths ;
Photometry, VRI
Keywords: globular clusters: general - stars: kinematics and dynamics -
globular clusters: individual (ome Centauri,NGC 5139)
Abstract:
The multi-object fiber-fed spectrograph AAOmega at the
Anglo-Australian Telescope has been used to establish and measure
accurate (≤1km/s) radial velocities for a new sample of members in
the outer parts of the stellar system ω Centauri. The new sample
more than doubles the number of known members with precise velocities
that lie between 25' and 45' from the cluster center. Combining this
sample with earlier work confirms that the line-of-sight velocity
dispersion of ω Cen remains approximately constant at ∼6.5km/s
in the outer parts of the cluster, which contain only a small fraction
of the total cluster stellar mass. It is argued that the approximately
constant velocity dispersion in the outer regions is most likely a
consequence of external influences, such as the tidal shock heating
that occurs each time ω Cen crosses the Galactic plane. There is
therefore no requirement to invoke dark matter or non-standard
gravitational theories.
Description:
The list of candidates to be observed consisted first of the 154
probable ω Cen members identified in DC08 (Da Costa & Coleman,
2008, Cat. J/AJ/136/506) with further candidates generated from the
same photometry set as used in DC08 but the selection window was
extended ∼0.5mag fainter parallel to the cluster sequence in the CMD
(see Figure 1 of DC08) and with stars in the original DC08 sample that
lie between 30' and 60' from the cluster center and which were not
observed in DC08.
Five nights in 2008 April were allocated to this program with the
Two-Degree Field (2dF) fiber positioner and the AAOmega spectrograph
on the 3.9m AAT. The spectrograph was configured with the λ5700
dichroic and the 1500V (blue) and 1700D gratings (red). The red
spectra (used in this paper) were centered at λ8600 with
coverage from λ8340 to λ8775 including the CaII triplet
lines at λ8498, 8542, and 8662. The resolution is ∼10000 and
the scale corresponds to 8.5km/s per pixel.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 69 160 *ω Cen probable member data
table2.dat 69 39 *ω Cen probable non-member data
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Note on table1.dat, table2.dat: For stars in common these data supercede those
in Table 2 of Da Costa & Coleman (2008, Cat. J/AJ/136/506).
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See also:
J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011)
J/MNRAS/396/2183 : RVs of red giants in ω Cen (Sollima+ 2009)
J/MNRAS/399/195 : Blue & red spectra of ω Cen HB stars (Van Loon+, 2009)
J/ApJ/698/2048 : Abundances of red giants in ω Cen (Johnson+, 2009)
J/AJ/136/506 : RVs of ω Centauri members (Da Costa+, 2008)
J/ApJ/681/1505 : Abundances of red giants in ω Cen (Johnson+, 2008)
J/ApJ/661/L155 : Radial velocities RGB stars in omega Cen (Pancino+, 2007)
J/A+A/445/503 : Radial velocities in Omega Cen (NGC5139) (Reijns+, 2006)
J/ApJ/647/1075 : Age-metallicity relation of ω Cen (Stanford+, 2006)
J/AJ/114/1087 : Omega Cen radial velocities (Mayor+ 1997)
Byte-by-byte Description of file: table[12].dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID Cluster star identifier;
<[DC2008] NN-N-NNNNN> in Simbad
11- 12 I2 h RAh [13] Hour of Right Ascension (J2000)
14- 15 I2 min RAm [21/32] Minute of Right Ascension (J2000)
17- 21 F5.2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- [-] Sign of the Declination (J2000)
24- 25 I2 deg DEd [46/48] Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000)
35- 39 F5.1 km/s HRV [210/255] Heliocentric radial velocity
41- 43 F3.1 km/s e_HRV [0.1/3] The 1σ error in HRV
45- 48 F4.1 arcmin Dist [20/59] Distance from cluster center
50- 54 F5.2 mag Vmag [15/17.3] The V band magnitude (1)
56- 59 F4.2 mag V-I [0.8/1.2] The (V-I) color index (1)
61- 64 F4.2 0.1nm EW [1.6/4.4] Sum of 8542 and 8662 Ca II triplet
line equivalent widths (Å)
66- 69 F4.2 0.1nm e_EW [0.06/0.3] The 1σ error in EW; Angstroms
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Note (1): From a forthcoming paper, M. G. Coleman & G. S. Da Costa (2008,
in preparation) where V- and I-band photometry was obtained with the
8kx8k CCD mosaic camera mounted on the ANU 1m telescope at Siding
Spring Observatory. See Cat. J/AJ/136/506, section 2.1.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Dec-2013