J/AJ/100/1191 Giants DDO photometry (Morrison+, 1990)
Where does the disk stop and the halo begin? Kinematics in a rotation field.
Morrison H.L., Flynn C., Freeman K.C.
<Astron. J. 100, 1191 (1990)>
=1990AJ....100.1191M 1990AJ....100.1191M
ADC_Keywords: Stars, giant ; Photometry, DDO
Abstract:
A sample of G and K giants approximately 4kpc from the Sun, covering
the abundance range from solar to extreme halo has been selected
without kinematic bias in a field aligned to measure galactic
rotation. Accurate abundances, distances, and radial velocities have
been measured. This sample has been combined with nonkinematically
selected solar neighborhood objects taken from the literature, in
order to examine the kinematics of the transition from disk to "thick
disk" to halo. The metal-rich objects in the sample, with
0>[Fe/H]>-0.8, rotate rapidly around the galactic center and have low
azimuthal velocity dispersion, σφ=40±10km/s. For objects
in the range -0.5>[Fe/H]>-0.8, we find a small value for the
asymmetric drift of 35±10km/s. We associate these objects with the
thick disk, confirming the kinematical results of Ratnatunga and
Freeman (1989, Cat.V/65) and others. In the abundance range
-1.0>[Fe/H]≥-1.6 we find, in addition to objects with normal halo
kinematics, objects in a disk configuration, confirming the results of
Norris, Bessell, and Pickles (1985ApJS...58..463N 1985ApJS...58..463N). This disk is
rotating rapidly, Vrot=170±15km/s, and has a scale height of
1.4±0.7kpc, these kinematical and spatial properties are similar to
those of the thick disk. We show that these objects have different
kinematics from that of the globular clusters and a sample of local RR
Lyraes in the same abundance range. This suggests to us that these
objects are better associated with the thick disk than the halo, and
we refer to them as "metal-weak thick-disk stars". Hence we suggest
that the conventional chemical description of the thick disk (Gilmore
and Wyse, 1985AJ.....90.2015G 1985AJ.....90.2015G) be widened to include stars with
abundances as low as [Fe/H]=-1.6. At the galactic plane, the density
of these metal-weak thick-disk stars is similar to that of halo stars,
so they significantly affect the measurement, from samples selected on
abundance, of the components of the velocity ellipsoid for the halo in
the solar neighborhood. For the halo giants in our sample we measure
σφ=102±24 and Vrot=17±24km/s. The rotation velocity
and velocity ellipsoid for the metal-weak halo in the solar
neighborhood have been rederived for objects with [Fe/H]≤-1.6 from
the large sample of Norris (1986ApJS...61..667N 1986ApJS...61..667N), thus removing the
possibility of contamination by metal-weak thick-disk stars. We derive
Vrot=25±15km/s and (σr, σφ,
σθ)=(133±8, 98±13, 94±6)km/s. These values are
more consistent with other information about the shape of the halo.
For a description of the DDO photometric system, see e.g. GCPD/12
Description:
The CCO measurement were made during the period 1986-1988, on the 2.3m
telescope at Siding Spring Observatory. The spectroscopic observations
were obtained with the Mount Stromlo 1.9m telescope during 1986 and 1987.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 67 169 DDO photometry of 169 K giant candidates
table2.dat 52 113 Spectroscopic results of the giants
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See also:
II/164 : Catalogue of DDO photometry 88 (Mermilliod+ 1989)
II/80 : Catalogue of homogeneous DDO photometry of bright stars (McLure+ 1981)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- [MFF90] Object designation
13- 18 A6 --- Lum Luminosity class derived from DDO photometry
20- 21 I2 h RAh Right ascension (1950)
23- 24 I2 min RAm Right ascension (1950)
26- 29 F4.1 s RAs Right ascension (1950)
31 A1 --- DE- Declination sign (1950)
32- 33 I2 deg DEd Declination (1950)
35- 36 I2 arcmin DEm Declination (1950)
38- 39 I2 arcsec DEs Declination (1950)
41- 45 F5.3 mag C45-48 45-48 DDO colour index (σ=0.009)
47- 51 F5.3 mag C42-45 42-45 DDO colour index (σ=0.013)
53- 58 F6.3 mag C41-42 41-42 DDO colour index (σ=0.013)
60- 65 F6.3 mag C38-42 38-42 DDO colour index (σ=0.017)
67 I1 --- Nobs Number of DDO measurements
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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- 12 A12 --- [MFF90] Star designation
14- 18 F5.2 mag Vmag V magnitude (no reddening correction applied)
20- 23 F4.2 mag B-V B-V colour index (no reddening correction
applied)
25- 26 I2 --- o_Vmag Number of BV observations
28- 31 I4 km/s RV ? Radial velocity (single measurement mean
error σ=10km/s)
33- 34 I2 --- o_RV ? number of RV measurements
36- 40 F5.2 [Sun] [Fe/H] Metallicity
42- 46 F5.2 mag VMAG Absolute V magnitude
48- 52 I5 pc Dist Distance
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer, Francois Ochsenbein [CDS] 30-Aug-1999