J/ApJ/749/77 MW halo. III. Statistical chemical abundances (Schlaufman+, 2012)
Insight into the formation of the Milky Way through cold halo substructure.
III. Statistical chemical tagging in the smooth halo.
Schlaufman K.C., Rockosi C.M., Lee Y.S., Beers T.C., Allende Prieto C.,
Rashkov V., Madau P., Bizyaev D.
<Astrophys. J., 749, 77 (2012)>
=2012ApJ...749...77S 2012ApJ...749...77S
ADC_Keywords: Abundances, [Fe/H] ; Stars, halo ; Milky Way
Keywords: Galaxy: abundances - Galaxy: formation - Galaxy: halo -
Galaxy: kinematics and dynamics
Abstract:
We find that the relative contribution of satellite galaxies accreted
at high redshift to the stellar population of the Milky Way's smooth
halo increases with distance, becoming observable relative to the
classical smooth halo about 15 kpc from the Galactic center. In
particular, we determine line-of-sight-averaged [Fe/H] and
[α/Fe] in the metal-poor main-sequence turnoff (MPMSTO)
population along every Sloan Extension for Galactic Understanding and
Exploration (SEGUE) spectroscopic line of sight. Restricting our
sample to those lines of sight along which we do not detect elements
of cold halo substructure (ECHOS), we compile the largest
spectroscopic sample of stars in the smooth component of the halo ever
observed in situ beyond 10 kpc. We find significant spatial
autocorrelation in [Fe/H] in the MPMSTO population in the distant half
of our sample beyond about 15 kpc from the Galactic center. Inside of
15 kpc however, we find no significant spatial autocorrelation in
[Fe/H]. At the same time, we perform SEGUE-like observations of N-body
simulations of Milky Way analog formation. While we find that halos
formed entirely by accreted satellite galaxies provide a poor match to
our observations of the halo within 15 kpc of the Galactic center, we
do observe spatial autocorrelation in [Fe/H] in the simulations at
larger distances. This observation is an example of statistical
chemical tagging and indicates that spatial autocorrelation in
metallicity is a generic feature of stellar halos formed from accreted
satellite galaxies.
Description:
In this third paper of the series, we quantify the degree of spatial
chemical inhomogeneity and spatial variation in chemical abundance in
the smooth component of the halo, using the substructure-cleaned
sample of metal-poor main-sequence turnoff (MPMSTO) stars produced in
Schlaufman et al., 2009, Cat. J/ApJ/703/2177, and the chemical
abundance technique developed in Schlaufman et al. 2011ApJ...734...49S 2011ApJ...734...49S.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 103 118 Spatial and radial distribution of [Fe/H] in the
smooth component of the halo
table2.dat 103 118 Spatial and radial distribution of [α/Fe] in
the smooth component of the halo
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See also:
J/A+A/522/A26 : Fe Abundances in metal-poor stars (Sbordone+ 2010)
J/ApJ/706/1095 : Chemical compositions of 26 outer halo stars (Zhang+, 2009)
J/ApJ/703/2177 : Pap. I. Metal-poor MS turnoff stars (Schlaufman+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/A+A/501/519 : Metal-poor turnoff stars abundances (Bonifacio+, 2009)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/AJ/126/1362 : Century Survey Galactic Halo Project. I. (Brown+, 2003)
J/AJ/125/2502 : Spectral indices of Galactic halo (Morrison+, 2003)
J/AJ/117/2329 : Spectroscopy of hot stars in the halo. III (Wilhelm+, 1999)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.2 deg RAdeg Right ascension (J2000)
8- 13 F6.2 deg DEdeg Declination (J2000)
15- 20 F6.2 deg GLON [3.16/358.72] Galactic longitude
22- 27 F6.2 deg GLAT [-71.74/87.02] Galactic latitude
29- 32 I4 --- bplate [1880/2963]? SEGUE bplate (Cat. J/AJ/137/4377)
34- 37 I4 --- fplate [1881/2965] SEGUE fplate (Cat. J/AJ/137/4377)
39- 43 F5.2 [Sun] Fe12i [-2.2/-0.9]? [Fe/H]in split at d=12.1kpc
45- 48 F4.2 [Sun] e_Fe12i [0.08/0.3]? Fe12i uncertainty
50- 54 F5.2 [Sun] Fe12o [-2.1/-0.6]? [Fe/H]out split at d=12.1kpc
56- 59 F4.2 [Sun] e_Fe12o [0.07/0.3]? Fe12o uncertainty
61- 65 F5.2 [Sun] Fe14i [-2.5/-0.9]? [Fe/H]in split at d=14.1kpc
67- 70 F4.2 [Sun] e_Fe14i [0.07/0.2]? Fe14i uncertainty
72- 76 F5.2 [Sun] Fe14o [-2/-0.6]? [Fe/H]out split at d=14.1kpc
78- 81 F4.2 [Sun] e_Fe14o [0.07/0.3]? Fe14o uncertainty
83- 87 F5.2 [Sun] Fe16i [-2.2/-0.9]? [Fe/H]in split at d=16.8kpc
89- 92 F4.2 [Sun] e_Fe16i [0.07/0.2]? Fe16i uncertainty
94- 98 F5.2 [Sun] Fe16o [-2.6/-0.6]? [Fe/H]out split at d=16.8kpc
100-103 F4.2 [Sun] e_Fe16o [0.07/0.3]? Fe16o uncertainty
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.2 deg RAdeg Right ascension (J2000)
8- 13 F6.2 deg DEdeg Declination (J2000)
15- 20 F6.2 deg GLON [3.16/358.72] Galactic longitude
22- 27 F6.2 deg GLAT [-71.74/87.02] Galactic latitude
29- 32 I4 --- bplate [1880/2963]? SEGUE bplate (Cat. J/AJ/137/4377)
34- 37 I4 --- fplate [1881/2965] SEGUE fplate (Cat. J/AJ/137/4377)
39- 43 F5.2 [Sun] a12i [0.1/0.5]? [α/Fe]in at d=12.1kpc
45- 48 F4.2 [Sun] e_a12i [0.06/0.3]? a12i uncertainty
50- 54 F5.2 [Sun] a12o [0.02/0.6]? [α/Fe]out at d=12.1kpc
56- 59 F4.2 [Sun] e_a12o [0.05/0.3]? a12o uncertainty
61- 65 F5.2 [Sun] a14i [0.1/0.6]? [α/Fe]in at d=14.1kpc
67- 70 F4.2 [Sun] e_a14i [0.06/0.3]? a14i uncertainty
72- 76 F5.2 [Sun] a14o [0/0.6]? [α/Fe]out at d=14.1kpc
78- 81 F4.2 [Sun] e_a14o [0.06/0.3]? a14o uncertainty
83- 87 F5.2 [Sun] a16i [0.04/0.5]? [α/Fe]in at d=16.8kpc
89- 92 F4.2 [Sun] e_a16i [0.06/0.3]? a16i uncertainty
94- 98 F5.2 [Sun] a16o [-0.02/0.6]? [α/Fe]out at d=16.8kpc
100-103 F4.2 [Sun] e_a16o [0.1/0.3]? a16o uncertainty
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History:
From electronic version of the journal
References:
Schlaufman et al. Paper I. 2009ApJ...703.2177S 2009ApJ...703.2177S Cat. J/ApJ/703/2177
Schlaufman et al. Paper II. 2011ApJ...734...49S 2011ApJ...734...49S
(End) Emmanuelle Perret [CDS] 14-Nov-2013