A Blueprint for the Milky Way’s Stellar Populations. III. Spatial Distributions and Population Fractions of Local Halo Stars

Starcounts remain one of the most effective methods of probing the structure of the Galactic stellar populations. However, studies of the distribution at large distances above the Plane demand accurate photometry extending to faint magnitudes (V > 20), and such datasets are still rare. We (Reid & Majewski 1993) have analyzed data from one field — Majewski's (1992) UJF observations of SA57, the North Galactic Pole field. Our results revealed significant discrepancies with the standard model of the Galaxy (see refs. in Reid & Majewski), notably a paucity in the number of halo stars by a factor of two and the presence of a factor of two more disk stars than predicted — sufficient stars that the disk is the majority stellar population, outnumbering halo stars 2:1 even at V = 21. Majewski et al. (1993) has obtained UJFN photographic data for several other fields, and Fig. 1 shows a preliminary comparison of these observations with the predictions of the best-fitting SA57 model. Given that none of the parameters have been modified, the agreement is surprisingly good.

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A spectroscopic survey of late-type giants in the Milky Way disk and local halo substructure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308019972 ◽

2007 ◽

Vol 3 (S248) ◽

pp. 506-507

Author(s):

A. A. Sheffield ◽

S. R. Majewski ◽

A. M. Cheung ◽

C. M. Hampton ◽

J. D. Crane ◽

...

Keyword(s):

High Velocity ◽

Milky Way ◽

Stellar Populations ◽

Radial Velocities ◽

Solar Neighborhood ◽

Proper Motions ◽

Late Type ◽

Halo Stars ◽

Medium Resolution ◽

Galactic Stellar Populations

AbstractWe report the results of a survey of late-type giants aimed at understanding the nature of the disk and nearby halo Galactic stellar populations. We have obtained medium resolution (2–4 Å) spectra for 749 late K and early M giants at mid-latitudes selected from the 2MASS catalog with the FOBOS system at Fan Mountain Observatory. These spectra provide radial velocities (RVs) at the 5 km s−1 level, spectroscopic [Fe/H] good to σ[Fe/H] = 0.25 dex, and information on the relative abundances of Mg/Fe and Na/Fe in these stars. Proper motions from UCAC2 are used to search for local substructures, in particular the leading arm of the Sagittarius tidal streamer passing through the solar neighborhood. The combined proper motions and RVs yield full 6D stellar space motions. We have, by way of kinematics, relatively cleanly isolated the thick disk from the typically high velocity substructures that compose the nearby halo.We find evidence for substructure in the kinematics and metallicities of local halo stars.

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The evolution of C and O abundances in stellar populations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313006212 ◽

2013 ◽

Vol 9 (S298) ◽

pp. 65-70 ◽

Cited By ~ 1

Author(s):

Poul E. Nissen ◽

William J. Schuster

Keyword(s):

High Resolution ◽

Time Scale ◽

Main Sequence ◽

Stellar Populations ◽

Thin Disk ◽

Main Sequence Stars ◽

Chemical Enrichment ◽

Halo Stars ◽

New Information ◽

Atomic Lines

AbstractCarbon and oxygen abundances in F and G main-sequence stars ranging in metallicity from [Fe/H] = −1.6 to +0.5 are determined from a non-LTE analysis of C i and O i atomic lines in high-resolution spectra. Both C and O are good tracers of stellar populations; distinct trends of [C/Fe] and [O/Fe] as a function of [Fe/H] are found for high- and low-alpha halo stars and for thick- and thin-disk stars. These trends and that of [C/O] provide new information on the nucleosynthesis sites of carbon and the time-scale for the chemical enrichment of the various Galactic components.

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Distribution of R- and S-Process Elements in the Galactic Halo

Symposium - International Astronomical Union ◽

10.1017/s0074180900035555 ◽

1988 ◽

Vol 132 ◽

pp. 501-506

Author(s):

C. Sneden ◽

C. A. Pilachowski ◽

K. K. Gilroy ◽

J. J. Cowan

Keyword(s):

Heavy Element ◽

Galactic Halo ◽

Low Noise ◽

Heavy Elements ◽

Process Synthesis ◽

Element Abundances ◽

Halo Stars ◽

Abundance Patterns ◽

R Process ◽

Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

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Reaction couples of ceramic thin films prepared by CVD

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106053 ◽

1988 ◽

Vol 46 ◽

pp. 798-799

Author(s):

D.W. Susnitzky ◽

S.R. Summerfelt ◽

C.B. Carter

Keyword(s):

Thin Film ◽

Vapor Deposition ◽

Chemical Vapor ◽

Deposition Process ◽

Solid State Reactions ◽

Spatial Distributions ◽

Diffusion Couples ◽

Kinetics Studies ◽

Ceramic Thin Films ◽

Initial Stage

Solid-state reactions have traditionally been studied in the form of diffusion couples. This ‘bulk’ approach has been modified, for the specific case of the reaction between NiO and Al2O3, by growing NiAl2O4 (spinel) from electron-transparent Al2O3 TEM foils which had been exposed to NiO vapor at 1415°C. This latter ‘thin-film’ approach has been used to characterize the initial stage of spinel formation and to produce clean phase boundaries since further TEM preparation is not required after the reaction is completed. The present study demonstrates that chemical-vapor deposition (CVD) can be used to deposit NiO particles, with controlled size and spatial distributions, onto Al2O3 TEM specimens. Chemical reactions do not occur during the deposition process, since CVD is a relatively low-temperature technique, and thus the NiO-Al2O3 interface can be characterized. Moreover, a series of annealing treatments can be performed on the same sample which allows both Ni0-NiAl2O4 and NiAl2O4-Al2O3 interfaces to be characterized and which therefore makes this technique amenable to kinetics studies of thin-film reactions.

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Application of high-resolution field-emission LVSEM, backscatter imaging, immunogold staining to definition of the spatial distributions of two human neutrophil adherence receptors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146023 ◽

1993 ◽

Vol 51 ◽

pp. 36-37

Author(s):

Robert D. Nelson ◽

Sharon R. Hasslen ◽

Stanley L. Erlandsen

Keyword(s):

Cell Surface ◽

Surface Membrane ◽

Three Dimensional ◽

Human Neutrophils ◽

Spatial Distributions ◽

Immunogold Staining ◽

Functional Control ◽

Neutrophil Adherence ◽

Definition Of ◽

Mode Of Attachment

Receptors are commonly defined in terms of number per cell, affinity for ligand, chemical structure, mode of attachment to the cell surface, and mechanism of signal transduction. We propose to show that knowledge of spatial distribution of receptors on the cell surface can provide additional clues to their function and components of functional control.L-selectin and Mac-1 denote two receptor populations on the neutrophil surface that mediate neutrophil-endothelial cell adherence interactions and provide for targeting of neutrophil recruitment to sites of inflammation. We have studied the spatial distributions of these receptors using LVSEM and backscatter imaging of isolated human neutrophils stained with mouse anti-receptor (primary) antibody and goat anti-mouse (secondary) antibody conjugated to 12 nm colloidal gold. This combination of techniques provides for three-dimensional analysis of the expression of these receptors on different surface membrane domains of the neutrophil: the ruffles and microvilli that project from the cell surface, and the cell body between these projecting structures.

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