J/MNRAS/382/1353 Spectral atlas of omega Cen post-MS stars (van Loon+, 2007)
A spectral atlas of post-main-sequence stars in ω Centauri:
kinematics, evolution, enrichment and interstellar medium.
van Loon J.T., Van Leeuwen F., Smalley B., Smith A.W., Lyons N.A.,
McDonald I., Boyer M.L.
<Mon. Not. R. Astron. Soc., 382, 1353-1374 (2007)>
=2007MNRAS.382.1353V 2007MNRAS.382.1353V
ADC_Keywords: Clusters, globular ; Stars, dwarfs ; Spectroscopy
Keywords: stars: AGB and post-AGB - stars: carbon - stars: horizontal branch -
stars: kinematics - stars: oscillations -
globular clusters: individual: omega Cen (NGC 5139)
Abstract:
We present a spectral atlas of the post-main-sequence population of
the most massive Galactic globular cluster, omega Centauri. Spectra
were obtained of more than 1500 stars selected as uniformly as
possible from across the (B, B-V) colour-magnitude diagram of the
proper motion cluster member candidates of van Leeuwen et al. (2000,
Cat. J/A+A/360/472). The spectra were obtained with the 2dF
multifibre spectrograph at the Anglo-Australian Telescope, and cover
the approximate range λ∼3840-3940Å at a resolving power of
λ/Δλ~=2000. This constitutes the most
comprehensible spectroscopic survey of a globular cluster. We measure
the radial velocities, effective temperatures, metallicities and
surface gravities by fitting ATLAS9 stellar atmosphere models. We
analyse the cluster membership and stellar kinematics, interstellar
absorption in the Ca II K line at 3933Å, the RR Lyrae instability
strip and the extreme horizontal branch, the metallicity spread and
bimodal CN abundance distribution of red giants, nitrogen and
s-process enrichment, carbon stars, pulsation-induced Balmer line
emission on the asymptotic giant branch (AGB), and the nature of the
post-AGB and UV-bright stars. Membership is confirmed for the vast
majority of stars, and the radial velocities clearly show the rotation
of the cluster core. We identify long-period RR Lyrae-type variables
with low gravity, and low-amplitude variables coinciding with warm RR
Lyrae stars. A barium enhancement in the coolest red giants indicates
that third dredge-up operates in AGB stars in omega Cen. This is
distinguished from the pre-enrichment by more massive AGB stars, which
is also seen in our data. The properties of the AGB, post-AGB and
UV-bright stars suggest that red giant branch (RGB) mass loss may be
less efficient at very low metallicity, [Fe/H]≪1, increasing the
importance of mass loss on the AGB. The catalogue and spectra are made
available via Centre Donnees de Strasbourg (CDS).
Description:
The 2dF multifibre spectrograph at the Anglo-Australian Telescope
(AAT) was used on the second half of the nights on 2000 February 26
and 27 and March 1 and 2, in combination with the 1200B grating to
obtain spectra in the approximate range λ∼3840-4940Å at a
resolving power of λ/Δλ=2000.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ocen2df.dat 153 1519 2dF catalogue of omega Centauri
table1.dat 61 18 Log of observations
sp/* . 1760 *Individual spectra
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Note on sp/*: For 6 stars, spectra of poor quality were ommited from the
analysis and the catalog but provided. There are:
oCen2dF.8a.LEID47432.dat, oCen2dF.8a.LEID48421.dat, oCen2dF.8b.LEID52037.dat,
oCen2dF.8b.LEID65019.dat, oCen2dF.8b.LEID71043.dat, oCen2dF.9a.LEID78032.dat
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See also:
J/A+A/360/472 : Proper motions in omega Centauri (van Leeuwen+, 2000)
Byte-by-byte Description of file: ocen2df.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- LEID LEID number (van Leeuwen et al., 2000,
Cat. J/A+A/360/472),
Cl* NGC 5139 Leid NNNNN in Simbad
7- 8 I2 h RAh Right ascension (J2000)
10- 11 I2 min RAm Right ascension (J2000)
13- 17 F5.2 s RAs [0/60] Right ascension (J2000)
19 A1 --- DE- Declination sign (J2000)
20- 21 I2 deg DEd Declination (J2000)
23- 24 I2 arcmin DEm Declination (J2000)
26- 29 F4.1 arcsec DEs [0/60] Declination (J2000)
31- 39 F9.5 deg GLON Galactic longitude
41- 48 F8.5 deg GLAT Galactic latitude
50- 55 F6.3 mag Bmag B magnitude
57- 62 F6.3 mag B-V ?=- B-V colour index
64- 69 F6.3 mag B'mag Computed B' magnitude (1)
71- 76 F6.3 mag B1-B2 B1-B2 colour index (1)
78- 81 I4 km/s VLSR LSR velocity
83- 87 I5 K Teff Effective temperature
89- 92 F4.2 [cm/s2] log(g) Surface gravity
94- 98 F5.2 [Sun] [Fe/H] Metallicity
100 I1 --- p [0/3] Spectral pecularity (2)
102 I1 --- nS [1/2] Number of spectra taken
104 I1 --- V [0/1] If 1: variable star of RR Lyrae type
106-111 F6.3 --- S3839 ?=- S3839 line strength
113-118 F6.3 --- S3933b S3839[blue] line strength (3)
120-125 F6.3 --- S3933r S3933[red] line strength (3)
127-132 F6.3 mag CH4300 CH4300 line index (4)
134-139 F6.3 mag Ba4554 Ba4554 line index (4)
141-146 F6.3 mag TiO4620 TiO4620 line index (4)
148-153 F6.3 mag TiO4760 TiO4760 line index (4)
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Note (1): As an indication of, respectively, the total flux collected on
the CCD and the recorded spectral slope, we define a magnitude and
colour that we compute from the observed spectrum. The magnitude is
broadly similar to the B band, and is defined as
B'=25-2.5log[∑{i=1toN}f(i)]
while the colour is defined in relation to the blue and red halves
within this band is defined as
B1-B2=-2.5log[(∑{i=1toN/2}f(i))/(∑{j=N/2toN}f(j)]
Note (2): Flag as follows:
1 = if the maximum difference between the observed spectrum and the
best model spectrum was in excess of both 20 per cent of the
continuum and three times the standard deviation determined
outside of the line profiles, then the model fitting procedure
was repeated excluding those points and the two points at
either side of them
2 = if Ca H+K line emission detected
3 = if both Ca H+K and hydrogen lines showed signs of possible emission
Note (3): Strength of the blue- and redshifted CaII K ISM components from
the average flux levels, F(L1-L2) (between wavelengths L1 and L2 in
Å) in the normalized spectrum after subtracting the best model fit:
S3839[blue] = F(3921-3932)-[F(3916-3921)+F(3932-3934)]/2
S3839[red] = F(3934-3939)-[F(3932-3934)+F(3939-3950)]/2
Note (4): Line indexes are defined as:
CH4300 = -2.5log[2F(4285-4315)/(F(4240-4280)-F(4390-4460))]
Ba4554 = -2.5log[2F(4553-4555)/(F4542-4544)+F(4560-4562))]
TiO4620 = -2.5log[F(4764-4766)/F(4754-4756)]
TiO4760 = -2.5log[(F(4590-4592)+F(4640-4642))/2F(4616-4620)]
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- ObsID Observation ID
4- 16 A13 --- Obs.date Observation UT date (YYYY MM DD.dd)
18- 21 F4.2 --- AirMass Air mass
23- 25 F3.1 arcsec Seeing Seeing
27 I1 --- Plate Plate number
29 I1 --- CCD [1/2] CCD number
31- 36 A6 s Texp Exposure time (NxNNNN in s)
38- 40 I3 --- Ncl Number of probable cluster members
42 I1 --- Nf ?=- Number of probable field stars
44- 46 I3 --- Nsky Number of all sources
48- 54 A7 --- Sel Selection criteria
56- 58 I3 km/s VLSR Mean LSR velocity
60- 61 I2 km/s e_VLSR rms uncertainty on VLSR
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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2- 8 F7.2 0.1nm lambda Wavelength
10- 18 F9.2 ct Counts ?=* Reduced 2dF spectrum counts
20- 27 F8.4 --- Nsp ?=* Normalized 2dF spectrum
31- 36 F6.4 --- A9sp Best-fitting ATLAS9/SYNTHE spectrum
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Acknowledgements:
Jacco van Loon, jacco(at)astro.keele.ac.uk
History:
* 12-Feb-2008: table1
* 17-Sep-2009: Spectra added
(End) Patricia Vannier [CDS] 12-Feb-2008