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Detailed Elemental Abundances in the M31 Stellar Halo: Low-Resolution Resolved Stellar Spectroscopy

Escala, Ivanna and Kirby, Evan N. and Gilbert, Karoline M. and Cunningham, Emily C. and Wojno, Jennifer (2018) Detailed Elemental Abundances in the M31 Stellar Halo: Low-Resolution Resolved Stellar Spectroscopy. . (Unpublished)

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While measurements of [α/Fe] have been made in the stellar halo of the Milky Way, little is known about detailed chemical abundances in the stellar halo of M31. To make progress with existing telescopes, we apply spectral synthesis to low-resolution DEIMOS spectroscopy (R ∼ 2500 at 7000 \AA) across a wide spectral range (4500 \AA < λ < 9100 \AA). By applying our technique to low-resolution spectra of 135 red giant branch (RGB) stars in 4 MW globular clusters, we demonstrate that our technique reproduces previous measurements from higher resolution spectroscopy. Based on the intrinsic dispersion in [Fe/H] and [α/Fe] of individual stars in our combined cluster sample, we estimate systematic uncertainties of ∼0.11 dex and ∼0.04 dex in [Fe/H] and [α/Fe], respectively. We apply our method to deep, low-resolution spectra of 14 RGB stars in the smooth halo of M31, resulting in higher signal-to-noise per spectral resolution element compared to DEIMOS medium-resolution spectroscopy, given the same exposure time and conditions. We find ⟨[α/Fe]⟩ = 0.49 ± 0.31 dex and ⟨[Fe/H]⟩ = −1.53 ± 0.52 dex for our sample. This implies that the smooth halo field is likely composed of disrupted dwarf galaxies with truncated star formation histories that were accreted early in the formation history of M31.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Escala, Ivanna0000-0002-9933-9551
Kirby, Evan N.0000-0001-6196-5162
Gilbert, Karoline M.0000-0003-0394-8377
Cunningham, Emily C.0000-0002-6993-0826
Wojno, Jennifer0000-0002-3233-3032
Additional Information:The authors thank Alis Deason for assistance in line list vetting, Gina Duggan for useful discussions on generating grids of synthetic spectra, Raja Guha Thakurta for help with observations and insightful conversations, and Luis Vargas and Marla Geha for sharing their data for M31 outer halo RGB stars. IE acknowledges support from a Ford Foundation Predoctoral Fellowship and the NSF Graduate Research Fellowship under Grant No. DGE-1745301, as well as the NSF under Grant No. AST-1614081, along with ENK. KMG. and JW acknowledge support from NSF grant AST-1614569. ECC was supported by a NSF Graduate Research Fellowship as well as NSF Grant No. AST-1616540. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST-0071048.
Group:Astronomy Department
Funding AgencyGrant Number
Ford FoundationUNSPECIFIED
NSF Graduate Research FellowshipDGE-1745301
Subject Keywords:stars: abundances – galaxies: abundances – galaxies: halos – galaxies: formation – Local Group
Record Number:CaltechAUTHORS:20190514-104816487
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95483
Deposited By: Tony Diaz
Deposited On:14 May 2019 20:50
Last Modified:06 Feb 2020 23:39

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