J/ApJ/798/77 Metallicity of RGB stars in 6 M31 dwarf galaxies (Ho+, 2015)
Metallicity evolution of the six most luminous M31 dwarf satellites.
Ho N., Geha M., Tollerud E.J., Zinn R., Guhathakurta P., Vargas L.C.
<Astrophys. J., 798, 77 (2015)>
=2015ApJ...798...77H 2015ApJ...798...77H
ADC_Keywords: Abundances, [Fe/H] ; Photometry, VRI ; Galaxies, nearby
Keywords: galaxies: abundances; galaxies: dwarf;
galaxies: individual: (M32, NGC 205, NGC 185, NGC 147, And VII,
And II); Local Group
Abstract:
We present global metallicity properties, metallicity distribution
functions (MDFs), and radial metallicity profiles for the six most
luminous M31 dwarf galaxy satellites: M32, NGC 205, NGC 185, NGC 147,
Andromeda VII, and Andromeda II. The results presented are the first
spectroscopic MDFs for dwarf systems surrounding a host galaxy other
than the Milky Way (MW). Our sample consists of individual metallicity
measurements for 1243 red giant branch member stars spread across
these six systems. We determine metallicities based on the strength of
the Ca II triplet lines using the empirical calibration of Carrera et
al. (2013, J/MNRAS/434/1681), which is calibrated over the metallicity
range -4<[Fe/H]<+0.5. We find that these M31 satellites lie on the
same luminosity-metallicity relationship as the MW dwarf satellites.
We do not find a trend between the internal metallicity spread and
galaxy luminosity, contrary to previous studies. The MDF widths of
And II and And VII are similar to the MW dwarf spheroidal (dSph)
satellites of comparable luminosity; however, our four brightest M31
dwarf satellites are more luminous than any of the MW dSphs and have
broader MDFs. The MDFs of our six M31 dwarf satellites are consistent
with the leaky box model of chemical evolution, although our
metallicity errors allow a wide range of evolution models. We find a
significant radial gradient in metallicity in only two of our six
systems, NGC 185 and Andromeda II, and flat radial metallicity
gradients in the rest of our sample with no observed correlation
between rotational support and radial metallicity gradients. Although
the average properties and radial trends of the M31 dwarf galaxies
agree with their MW counterparts at similar luminosity, the detailed
MDFs are different, particularly at the metal-rich end.
Description:
We present individual stellar metallicities for the six brightest M31
dwarf galaxy satellites based on the strength of the calcium triplet
lines near 8550Å. Our data were taken using the Keck II 10m
telescope and the DEIMOS spectrograph (wavelength region
6400-9100Å; R∼6000).
Target selection for NGC 205, NGC 147, and NGC 185 was based on R-band
and I-band photometry from the CFHT12K imager. Target selection for
And II and And VII was based on imaging from the Kitt Peak Mosaic
camera in the Washington System M and T2 filters, as well as the DDO51
intermediate-band filters centered near the surface-gravity-dependent
Mgb and MgH absorption lines.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 6 Summary of M31 dwarf metallicity properties
table2.dat 61 1243 Metallicity of individual stars in each galaxy
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See also:
J/MNRAS/434/1681 : Extremely metal-poor stars CaII triplet (Carrera+, 2013)
J/ApJ/768/172 : Kinematic analysis of RGB in M31 dSphs (Collins+, 2013)
J/ApJ/765/140 : Stacked spectra of SDSS star forming gal. (Andrews+, 2013)
J/ApJ/763/61 : Abundances of red giant members of BootesI (Gilmore+, 2013)
J/A+A/544/A73 : BVI photometry of Fornax dSph galaxy (de Boer+, 2012)
J/AJ/144/4 : Dwarf galaxies data in the Local Group (McConnachie+, 2012)
J/ApJ/752/45 : SPLASH: Stellar spectro. of M31 satellites (Tollerud+, 2012)
J/MNRAS/411/1013 : CaII triplet in Sextans dSph galaxy (Battaglia+, 2011)
J/ApJ/711/361 : Local Group dE galaxies. II. (Geha+, 2010)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/MNRAS/383/183 : CaII triplet of RGB from VLT/FLAMES obs. (Battaglia+, 2008)
J/A+A/467/1025 : JHK photometry of Fornax RGB stars (Gullieuszik+, 2007)
J/AJ/133/270 : Metallicities and ages in Leo II dSph (Koch+, 2007)
J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/AJ/131/895 : Stars in the Carina dwarf spheroidal galaxy (Koch+, 2006)
J/AJ/131/332 : Velocities of individual stars in NGC 205 (Geha+, 2006)
J/AJ/127/840 : VRI photometry of Fornax red giants (Pont+, 2004)
J/AJ/124/234 : M31 outer halo UBVRI photom. & metallicity (Reitzel+, 2002)
J/MNRAS/327/918 : CaII in extragalactic red giants (Tolstoy+, 2001)
J/PASP/110/533 : BR photometry of Fornax bright stars (Stetson+ 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Gal Dwarf galaxy name
8- 10 I3 kpc Dist [617/824] Distance to the galaxy (1)
12- 16 F5.1 mag VMag [-16.5/-12.4] Absolute V-band magnitude (1)
18- 20 I3 --- N* [64/321] Number of stars in the final
metallicity sample
22- 26 F5.2 [Sun] <[Fe/H]> [-1.3/-0.5] Average-weighted mean metallicity
28- 31 F4.2 [Sun] e_<[Fe/H]> [0.04/0.08] <[Fe/H]> uncertainty
33- 36 F4.2 [Sun] s[Fe/H] [0.3/0.6] Internal metallicity dispersion (2)
38- 41 F4.2 [Sun] e_s[Fe/H] [0.04/0.08] s[Fe/H] uncertainty
43- 48 F6.3 --- Skew [-0.9/0.003] Skewness (3)
50- 53 F4.2 --- e_Skew [0.02/0.06] Skew uncertainty
55- 59 F5.2 --- Kurt [-0.7/1.4] Excess kurtosis (4)
61- 64 F4.2 --- e_Kurt [0.1/0.5] Kurt uncertainty
66- 69 I4 pc rh [110/1176] Half-light radius rh (1)
71- 75 F5.2 --- grad [-0.4/0.02] Radial metallicity gradient (5)
77- 80 F4.2 --- e_grad [0.01/0.04] Gradient uncertainty (5)
82- 85 F4.2 --- p.eff [0.07/0.5] Best-fit value of the stellar
effective yield (6)
87- 91 F5.3 --- e_p.eff [0.001/0.005] p.eff uncertainty
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Note (1): From McConnachie (2012, J/AJ/144/4).
Note (2): Internal metallicity dispersion, calculated by taking the second
moment of the distribution and accounting for increased dispersion
from observational errors, along with Monte Carlo errors.
Note (3): The skew, or third moment, of the distribution.
Note (4): The excess kurtosis, or fourth moment minus three, of the
distribution.
Note (5): The radial metallicity gradient d[Fe/H]/d(r/rh)
with associated errors from a least-squares fit.
Note (6): The best-fit value of the stellar yield, expressed as a fraction of
the solar abundance, resulting from fitting the leaky box model to
the metallicity distribution function (MDF) of each dwarf.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 -- Seq [1/321] Internal Star ID number
5- 10 A6 -- Gal Dwarf galaxy name
12- 13 I2 h RAh [0/23] Hour of Right Ascension (J2000)
15- 16 I2 min RAm Minute of Right Ascension (J2000)
18- 22 F5.2 s RAs Second of Right Ascension (J2000)
24 A1 --- DE- [+] Sign of Declination (J2000)
25- 26 I2 deg DEd [33/50] Degree of Declination (J2000)
28- 29 I2 arcmin DEm Arcminute of Declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of Declination (J2000)
36- 40 F5.3 mag V-I [0.6/3.6] Extinction corrected (V-I) color index
42- 47 F6.3 mag Vmag [20.6/24] Extinction corrected V-band magnitude
49- 56 F8.5 [Sun] [Fe/H] [-4/0.5] Iron abundance relative to the Sun
58- 61 F4.2 [Sun] e_[Fe/H] [0.2/1] Uncertainty in [Fe/H]
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-May-2015