Mapping the galactic halo. VI. Spectroscopic measures of luminosity and metallicity

Heather L. Morrison, John Norris, Mario Mateo, Paul Harding, Edward W Olszewski, Stephen A. Shectman, R. C. Dohm-Palmer, Amina Helmi, Kenneth C. Freeman

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

We present our calibration of spectroscopic measures of luminosity and metallicity for halo giant candidates and give metallicities and distances for our first sample of spectroscopically confirmed giants. These giants have distances ranging from 15 to 83 kpc. As surveys reach farther into the Galaxy's halo with K giant samples, identification of giants becomes more difficult. This is because the numbers of foreground halo K dwarfs rise for V magnitudes of 19-20, typical for halo giants at ∼ 100 kpc. Our photometric survey uses the strength of the Mg b/H feature near 5170 Å to weed K dwarfs out of the disk and thick disk, but we need spectroscopic measures of the strength of the Ca II K, Ca I λ4227, and Mg b/H features to distinguish between the very metal-poor dwarfs and halo giants. Using a full error analysis of our spectroscopic measures, we show why a signal-to-noise ratio of ∼15 pixel-1 at Ca I λ4227 and ∼10 at Ca II K is needed for reliable luminosity discrimination. We use the Ca II K and Mg b features to measure metallicity in our halo giants, with typical errors (random plus systematic) of 0.3 dex for [Fe/H] values from -0.8 to -3.0.

Original languageEnglish (US)
Pages (from-to)2502-2520
Number of pages19
JournalAstronomical Journal
Volume125
Issue number5 1769
DOIs
StatePublished - May 2003

Fingerprint

galactic halos
metallicity
halos
luminosity
error analysis
signal-to-noise ratio
weed
pixel
calibration
metal
random errors
discrimination
signal to noise ratios
pixels
galaxies
metals

Keywords

  • Galaxy: evolution
  • Galaxy: halo
  • Galaxy: kinematics and dynamics

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Morrison, H. L., Norris, J., Mateo, M., Harding, P., Olszewski, E. W., Shectman, S. A., ... Freeman, K. C. (2003). Mapping the galactic halo. VI. Spectroscopic measures of luminosity and metallicity. Astronomical Journal, 125(5 1769), 2502-2520. https://doi.org/10.1086/374231

Mapping the galactic halo. VI. Spectroscopic measures of luminosity and metallicity. / Morrison, Heather L.; Norris, John; Mateo, Mario; Harding, Paul; Olszewski, Edward W; Shectman, Stephen A.; Dohm-Palmer, R. C.; Helmi, Amina; Freeman, Kenneth C.

In: Astronomical Journal, Vol. 125, No. 5 1769, 05.2003, p. 2502-2520.

Research output: Contribution to journalArticle

Morrison, HL, Norris, J, Mateo, M, Harding, P, Olszewski, EW, Shectman, SA, Dohm-Palmer, RC, Helmi, A & Freeman, KC 2003, 'Mapping the galactic halo. VI. Spectroscopic measures of luminosity and metallicity', Astronomical Journal, vol. 125, no. 5 1769, pp. 2502-2520. https://doi.org/10.1086/374231
Morrison HL, Norris J, Mateo M, Harding P, Olszewski EW, Shectman SA et al. Mapping the galactic halo. VI. Spectroscopic measures of luminosity and metallicity. Astronomical Journal. 2003 May;125(5 1769):2502-2520. https://doi.org/10.1086/374231
Morrison, Heather L. ; Norris, John ; Mateo, Mario ; Harding, Paul ; Olszewski, Edward W ; Shectman, Stephen A. ; Dohm-Palmer, R. C. ; Helmi, Amina ; Freeman, Kenneth C. / Mapping the galactic halo. VI. Spectroscopic measures of luminosity and metallicity. In: Astronomical Journal. 2003 ; Vol. 125, No. 5 1769. pp. 2502-2520.
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