Radial velocities of blue horizontal branch field stars

Sommer–Larsen, Jesper; Christensen, P. R.

doi:10.1093/mnras/212.4.851

Cited by 2 publications

(2 citation statements)

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“…• Blue horizontal-branch (BHB) star surveys. The BHB stars are identified either from their unusually blue color (Sommer-Larsen and Christensen 1985;Norris & Hawkins 1991) or by using objective prism spectra near the Ca K line (Pier 1982(Pier , 1984Beers et al 1985). BHB stars are almost as rare as RR Lyrae variables, and their identification is complicated by the presence of halo blue stragglers, which have the same broadband colors as BHB stars but higher gravity.…”

Section: Tracersmentioning

confidence: 99%

“…We also need to be able to discriminate between halo blue stragglers (with main sequence gravities) and blue horizontal branch stars. Our followup spectroscopy allows us this via Balmer line profiles (Pier 1983;Sommer-Larsen and Christensen 1985;Norris & Hawkins 1991;Kinman et al 1994). In cases where we are able to obtain spectra which reach below the Balmer jump, its size can also be used as a discriminator.…”

Section: Blue Horizontal-branch Starsmentioning

confidence: 99%

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Mapping the Galactic Halo. I. The “Spaghetti” Survey

Morrison

Mateo

Olszewski

et al. 2000

The Astronomical Journal

130

142

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We describe a major survey of the Milky Way halo designed to test for kinematic substructure caused by destruction of accreted satellites. We use the Washington photometric system to identify halo stars efficiently for spectroscopic followup. Tracers include halo giants (detectable out to more than 100 kpc), blue horizontal branch stars, halo stars near the main sequence turnoff, and the "blue metal-poor stars" of Preston et al. (1994). We demonstrate the success of our survey by showing spectra of stars we have identified in all these categories, including giants as distant as 75 kpc. We discuss the problem of identifying the most distant halo giants. In particular, extremely metal-poor halo K dwarfs are present in approximately equal numbers to the distant giants for V > 18, and we show that our method will distinguish reliably between these two groups of metal-poor stars.We plan to survey 100 square degrees at high galactic latitude, and expect to increase the numbers of known halo giants, BHB stars and turnoff stars by more than an order of magnitude. In addition to the strong test that this large sample will provide for the question "was the Milky Way halo accreted from satellite galaxies?", we will improve the accuracy of mass measurements of the Milky Way beyond 50 kpc via the kinematics of the many distant giants and BHB stars we will find.We show that one of our first datasets constrains the halo density law over galactocentric radii of 5-20 kpc and z heights of 2-15 kpc. The data support a flattened power-law halo with b/a of 0.6 and exponent -3.0. More complex models with a varying axial ratio may be needed with a larger dataset.

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