J/ApJ/895/78 [Fe/H] and [α/Fe] in M31 dwarf galaxies (Wojno+, 2020)
Elemental Abundances in M31: [Fe/H] and [α/Fe] in M31 Dwarf Galaxies
Using Coadded Spectra.
Wojno J., Gilbert K.M., Kirby E.N., Escala I., Beaton R.L., Tollerud E.J.,
Majewski S.R., Guhathakurta P.
<Astrophys. J., 895, 78 (2020)>
=2020ApJ...895...78W 2020ApJ...895...78W
ADC_Keywords: Stars, giant; Galaxies; Abundances, [Fe/H]; Spectra, optical
Keywords: Andromeda Galaxy ; Chemical abundances ; Dwarf galaxies
Abstract:
We present chemical abundances of red giant branch (RGB) stars in the
dwarf spheroidal (dSph) satellite system of Andromeda (M31), using
spectral synthesis of medium-resolution (R∼6000) spectra obtained with
the KeckII telescope and Deep Imaging Multi-Object Spectrometer
spectrograph via the Spectroscopic and Photometric Landscape of
Andromeda's Stellar Halo survey. We coadd stars according to their
similarity in photometric metallicity or effective temperature to
obtain a signal-to-noise ratio (S/N) high enough to measure average
[Fe/H] and [α/Fe] abundances. We validate our method using high
S/N spectra of RGB stars in Milky Way globular clusters, as well as
deep observations for a subset of the M31 dSphs in our sample. For
this set of validation coadds, we compare the weighted average
abundance of the individual stars with the abundance determined from
the coadd. We present individual and coadded measurements of [Fe/H]
and [α/Fe] for stars in 10 M31 dSphs, including the first
[α/Fe] measurements for And IX, XIV, XV, and XVIII. These
fainter, less massive dSphs show declining [α/Fe] relative to
[Fe/H], implying an extended star formation history (SFH). In
addition, these dSphs also follow the same mass-metallicity relation
found in other Local Group satellites. The conclusions we infer from
coadded spectra agree with those from previous measurements in
brighter M31 dSphs with individual abundance measurements, as well as
conclusions from photometric studies. These abundances greatly
increase the number of spectroscopic measurements of the chemical
composition of M31's less massive dwarf satellites, which are crucial
to understanding their SFH and interaction with the M31 system.
Description:
We used spectral synthesis of medium-resolution spectra obtained with
the KeckII telescope and Deep Imaging Multi-Object Spectrometer
spectrograph via the Spectroscopic and Photometric Landscape of
Andromeda's Stellar Halo survey. The observed spectra cover a spectral
range of ∼6300Å<λ<9100Å, with a resolution of ∼6000 at
the central wavelength of ∼7800Å.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
00 42 44.33 +41 16 07.5 M31 = M31
-----------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 82 259 Excerpt of measured [Fe/H] and [α/Fe] from
our coadded spectra
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See also:
II/267 : The SDSS Photometric Catalog, Release 4 (Adelman-McCarthy+, 2006)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/364/102 : Abundances of field BHB star candidates (Kinman+, 2000)
J/AJ/125/1352 : Ursa Minor dSph M,T2, DDO51 photometry (Palma+, 2003)
J/ApJ/663/960 : Radial velocities of Leo I stars (Sohn+, 2007)
J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/ApJS/191/352 : Abundances in stars Milky Way dwarf satellites (Kirby+, 2010)
J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010)
J/ApJ/753/64 : Detailed abundances for 97 metal-poor stars (Ishigaki+, 2012)
J/AJ/144/4 : Properties dwarf galaxies in Local Group (McConnachie+, 2012)
J/ApJ/752/45 : SPLASH: Stellar spectroscopy M31 satellites (Tollerud+, 2012)
J/ApJ/768/172 : Kinematic analysis of red giant in M31 dSphs (Collins+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/AJ/146/86 : Cosmicflows-2 catalog (Tully+, 2013)
J/ApJ/767/134 : Abundances of red giant stars in UFD galaxies (Vargas+, 2013)
J/ApJ/790/73 : Fe & alpha abundance of RGBs in M31 satellites (Vargas+, 2014)
J/ApJ/819/135 : Lithium-rich giants in globular clusters (Kirby+, 2016)
J/ApJ/883/128 : alpha & Fe abundances in giant stellar stream (Gilbert+, 2019)
J/ApJ/889/177 : RGB abundances in disk, stream & halo of M31 (Escala+, 2020)
J/AJ/159/46 : Elemental abund. of 416 stars in 5 dSphs of M31 (Kirby+,2020)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Bin Bin type; [Fe/H] or Teff
6- 15 A10 --- Coadd Coadd type; science or validation
17- 22 A6 --- Mask Mask name
24- 60 A37 --- Slit Slit list
62- 66 F5.2 [Sun] [Fe/H] [-4.4/-0.92] Metallicity
68- 71 F4.2 [Sun] e_[Fe/H] [0.1/0.35] Uncertainty in [Fe/H]
73- 77 F5.2 [Sun] [a/H] [-0.78/1.2] log α/Fe abundance ratio
79- 82 F4.2 [Sun] e_[a/H] [0.09/0.9] Uncertainty in [a/H]
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 21-Sep-2021