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Title: MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. I. THE SCULPTOR DWARF SPHEROIDAL GALAXY

Abstract

We present measurements of Fe, Mg, Si, Ca, and Ti abundances for 388 radial velocity member stars in the Sculptor dwarf spheroidal galaxy (dSph), a satellite of the Milky Way (MW). This is the largest sample of individual alpha element (Mg, Si, Ca, and Ti) abundance measurements in any single dSph. The measurements are made from Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectra (6400-9000 A, R approx 6500). Based on comparisons to published high-resolution (R approx> 20,000) spectroscopic measurements, our measurements have uncertainties of sigma[Fe/H] = 0.14 and sigma[alpha/Fe] = 0.13. The Sculptor [Fe/H] distribution has a mean ([Fe/H]) = -1.58 and is asymmetric with a long, metal-poor tail, indicative of a history of extended star formation. Sculptor has a larger fraction of stars with [Fe/H] < -2 than the MW halo. We have discovered one star with [Fe/H] = -3.80 +- 0.28, which is the most metal-poor star known anywhere except the MW halo, but high-resolution spectroscopy is needed to measure this star's detailed abundances. As has been previously reported based on high-resolution spectroscopy, [alpha/Fe] in Sculptor falls as [Fe/H] increases. The metal-rich stars ([Fe/H] approx -1.5) have lower [alpha/Fe] than Galactic halo field stars of comparable metallicity. This indicatesmore » that star formation proceeded more gradually in Sculptor than in the Galactic halo. We also observe radial abundance gradients of -0.030 +- 0.003 dex arcmin{sup -1} in [Fe/H] and +0.013 +- 0.003 dex arcmin{sup -1} in [alpha/Fe] out to 11 arcmin (275 pc). Together, these measurements cast Sculptor and possibly other surviving dSphs as representative of the dwarf galaxies from which the metal-poor tail of the Galactic halo formed.« less

Authors:
; ;  [1];  [2];  [3]
  1. University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  2. McDonald Observatory, University of Texas, Austin, TX 78712 (United States)
  3. Astronomy Department, Yale University, New Haven, CT 06520 (United States)
Publication Date:
OSTI Identifier:
21378402
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 705; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/705/1/328; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; ELEMENT ABUNDANCE; GALACTIC EVOLUTION; IRON-ALPHA; MILKY WAY; RADIAL VELOCITY; SATELLITES; SPECTRA; SPECTROMETERS; SPECTROSCOPY; STARS; ABUNDANCE; ELEMENTS; EVOLUTION; GALAXIES; IRON; MEASURING INSTRUMENTS; METALS; TRANSITION ELEMENTS; VELOCITY

Citation Formats

Kirby, Evan N, Guhathakurta, Puragra, Bolte, Michael, Sneden, Christopher, and Geha, Marla C. MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. I. THE SCULPTOR DWARF SPHEROIDAL GALAXY. United States: N. p., 2009. Web. doi:10.1088/0004-637X/705/1/328.
Kirby, Evan N, Guhathakurta, Puragra, Bolte, Michael, Sneden, Christopher, & Geha, Marla C. MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. I. THE SCULPTOR DWARF SPHEROIDAL GALAXY. United States. https://doi.org/10.1088/0004-637X/705/1/328
Kirby, Evan N, Guhathakurta, Puragra, Bolte, Michael, Sneden, Christopher, and Geha, Marla C. Sun . "MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. I. THE SCULPTOR DWARF SPHEROIDAL GALAXY". United States. https://doi.org/10.1088/0004-637X/705/1/328.
@article{osti_21378402,
title = {MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. I. THE SCULPTOR DWARF SPHEROIDAL GALAXY},
author = {Kirby, Evan N and Guhathakurta, Puragra and Bolte, Michael and Sneden, Christopher and Geha, Marla C},
abstractNote = {We present measurements of Fe, Mg, Si, Ca, and Ti abundances for 388 radial velocity member stars in the Sculptor dwarf spheroidal galaxy (dSph), a satellite of the Milky Way (MW). This is the largest sample of individual alpha element (Mg, Si, Ca, and Ti) abundance measurements in any single dSph. The measurements are made from Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectra (6400-9000 A, R approx 6500). Based on comparisons to published high-resolution (R approx> 20,000) spectroscopic measurements, our measurements have uncertainties of sigma[Fe/H] = 0.14 and sigma[alpha/Fe] = 0.13. The Sculptor [Fe/H] distribution has a mean ([Fe/H]) = -1.58 and is asymmetric with a long, metal-poor tail, indicative of a history of extended star formation. Sculptor has a larger fraction of stars with [Fe/H] < -2 than the MW halo. We have discovered one star with [Fe/H] = -3.80 +- 0.28, which is the most metal-poor star known anywhere except the MW halo, but high-resolution spectroscopy is needed to measure this star's detailed abundances. As has been previously reported based on high-resolution spectroscopy, [alpha/Fe] in Sculptor falls as [Fe/H] increases. The metal-rich stars ([Fe/H] approx -1.5) have lower [alpha/Fe] than Galactic halo field stars of comparable metallicity. This indicates that star formation proceeded more gradually in Sculptor than in the Galactic halo. We also observe radial abundance gradients of -0.030 +- 0.003 dex arcmin{sup -1} in [Fe/H] and +0.013 +- 0.003 dex arcmin{sup -1} in [alpha/Fe] out to 11 arcmin (275 pc). Together, these measurements cast Sculptor and possibly other surviving dSphs as representative of the dwarf galaxies from which the metal-poor tail of the Galactic halo formed.},
doi = {10.1088/0004-637X/705/1/328},
url = {https://www.osti.gov/biblio/21378402}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 705,
place = {United States},
year = {2009},
month = {11}
}