J/ApJ/725/L186 Orbital eccentricities of 31535 G-dwarfs (Dierickx+, 2010)
Observational evidence from SDSS for a merger origin of the Milky Way's thick
disk.
Dierickx M., Klement R., Rix H.-W., Liu C.
<Astrophys. J., 725, L186-L190 (2010)>
=2010ApJ...725L.186D 2010ApJ...725L.186D
ADC_Keywords: Milky Way ; Photometry, SDSS ; Abundances, [Fe/H] ;
Proper motions ; Radial velocities ; Stars, G-type
Keywords: galaxies: individual (Milky Way) - Galaxy: evolution -
Galaxy: kinematics and dynamics - Galaxy: structure
Abstract:
We test four competing models that aim to explain the nature of stars
in spiral galaxies that are well away (>1kpc) from the midplane, the
so-called thick disk: the stars may have gotten there through orbital
migration, through satellite mergers and accretion, or through heating
of pre-existing thin disk stars. The eccentricity distribution of
thick disk stars has recently been proposed as a diagnostic to
differentiate between these mechanisms. Drawing on SDSS-DR7, we have
assembled a sample of 31535 G-dwarfs with six-dimensional phase-space
information and metallicities and have derived the orbital
eccentricities for them.
Description:
Here, we draw observations mostly from the conical volume (with the
Sun at its apex) that is naturally provided by the Sloan Digital Sky
Survey (SDSS) North Galactic Cap survey area. Specifically, we drew up
a sample of 31535 G-dwarf candidate stars from SDSS DR7 (Abazajian et
al. 2009, Cat. II/294), for which spectra were taken and spectral
parameters had been devised. G-dwarfs are the best-sampled
spectroscopic target category in SEGUE (Yanny et al. 2009, Cat.
J/AJ/137/4377), and a good fraction of these spectroscopic targets
falls into the distance range of 0.8-6kpc that is of particular
interest here.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 382 31535 Observed and derived properties of our SEGUE stars
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJ/714/663 : Stellar density map of the Milky Way (de Jong+, 2010)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/698/865 : Halo streams in the SDSS-DR7 (Klement+, 2009)
J/AJ/136/2070 : SEGUE stellar parameter pipeline. III. (Allende Prieto+, 2008)
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- MJD MJD of observation
7- 10 I4 --- Plate Plate ID
12- 14 I3 --- Fiber Fiber ID
16- 29 F14.10 deg RAdeg Right Ascension in decimal degrees (J2000)
31- 44 F14.10 deg DEdeg Declination in decimal degrees (J2000)
46- 59 F14.10 deg GLON Galactic longitude
61- 70 F10.6 deg GLAT Galactic latitude
72- 78 F7.4 mag g0mag [13.952/20.2843] Dereddened g magnitude
80- 89 F10.8 mag e_g0mag Error in g0mag
91- 98 F8.6 mag (g-r)0 Dereddened (g-r) magnitude
100-109 F10.8 mag e_(g-r)0 Error in (g-r)0
111-121 F11.6 km/s HRV [-527.3/443.6] Heliocentric radial velocity
123-131 F9.6 km/s e_HRV Error in HRV
133-146 F14.9 mas/yr pmRA [-192.2/158] Proper motion in Right Ascension
148-155 F8.5 mas/yr e_pmRA Error in pmRA
157-169 E13.6 mas/yr pmDE Proper motion in Declination
171-178 F8.5 mas/yr e_pmDE Error in pmDE
180-188 F9.3 pc Dist [371.21/10790] Ivezic et al.
(2008ApJ...684..287I 2008ApJ...684..287I) distance estimate
190-199 F10.5 pc e_Dist Error in Dist
201-215 F15.10 km/s Vx X-direction Galactocentric velocity component
217-227 F11.7 km/s e_Vx Error in Vx
229-242 F14.9 km/s Vy Y-direction Galactocentric velocity component
244-254 F11.7 km/s e_Vy Error in Vy
256-271 F16.11 km/s Vz Z-direction Galactocentric velocity component
273-284 F12.8 km/s e_Vz Error in Vz
286-299 F14.9 km/s Vphi Rotational velocity in cylindrical coordinates
301-311 F11.9 --- e [0,1] Eccentricity
313-316 I4 K Teff Effective Temperature
318-320 I3 K e_Teff Effective Temperature error
322-328 F7.5 [cm/s2] logg Surface gravity
330-339 F10.8 [cm/s2] e_logg Surface gravity error
341-351 F11.8 [Sun] [Fe/H] [-2.81/0.15] Iron abundance
353-362 F10.8 [Sun] e_[Fe/H] Iron abundance error
364-372 F9.7 [Sun] [a/Fe] α elements abundance
374-382 F9.7 [Sun] e_[a/Fe] α elements abundance error
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Aug-2012