J/ApJ/779/102 Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
The universal stellar mass-stellar metallicity relation for dwarf galaxies.
Kirby E.N., Cohen J.G., Guhathakurta P., Cheng L., Bullock J.S.,
Gallazzi A.
<Astrophys. J., 779, 102 (2013)>
=2013ApJ...779..102K 2013ApJ...779..102K
ADC_Keywords: Galaxies, nearby ; Stars, giant ; Abundances, [Fe/H] ;
Spectroscopy
Keywords: galaxies: abundances; galaxies: dwarf;
galaxies: fundamental parameters; galaxies: irregular; Local Group
Abstract:
We present spectroscopic metallicities of individual stars in seven
gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey
the same mass-metallicity relation as the dwarf spheroidal (dSph)
satellites of both the Milky Way and M31:
Z*∝M*0.30±0.02. The uniformity of the
relation is in contradiction to previous estimates of metallicity
based on photometry. This relationship is roughly continuous with the
stellar mass-stellar metallicity relation for galaxies as massive as
M*=1012M☉. Although the average metallicities of dwarf
galaxies depend only on stellar mass, the shapes of their metallicity
distributions depend on galaxy type. The metallicity distributions of
dIrrs resemble simple, leaky box chemical evolution models, whereas
dSphs require an additional parameter, such as gas accretion, to
explain the shapes of their metallicity distributions. Furthermore,
the metallicity distributions of the more luminous dSphs have sharp,
metal-rich cut-offs that are consistent with the sudden truncation of
star formation due to ram pressure stripping.
Description:
We measured metallicities from spectra of individual red giants in
15 Milky Way dwarf spheroidal (dSphs) and seven local group dwarf
irregular galaxies (dIrrs) as well as from coadded spectra of red
giants in 13 M31 dSphs. In order to maintain the homogeneity of the
spectroscopic data by using only Keck/DEIMOS spectroscopy, we observed
only galaxies visible from Mauna Kea. Table 1 lists the galaxies
observed.
We present new spectroscopy of red giants in NGC 6822, IC 1613, the
Pegasus dIrr, Leo A, and Aquarius. These are the first published
results from red giant spectroscopy in all of these galaxies except
NGC 6822, which was studied by Tolstoy et al. (2001, J/MNRAS/327/918).
We observed the new dwarf irregular galaxy slitmasks with Keck/DEIMOS
in the summers of 2010, 2011, and 2013 (see table 2).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 35 Dwarf galaxy sample
table2.dat 74 22 DEIMOS observations of the 7 dwarf irregular
galaxies (dIrrs)
table3.dat 123 3696 Metallicity catalog for all of the individual
member stars in the dIrrs and the MW satellites
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/MNRAS/439/1015 : Velocities of RGB stars in LG dwarf galaxies (Kirby+, 2014)
J/A+A/572/A88 : Measured EWs for Fornax RGB stars (Lemasle+, 2014)
J/ApJ/770/16 : Spectroscopic members of Segue 2 galaxy (Kirby+, 2013)
J/ApJ/768/172 : Kinematic analysis of RGB in M31 dSphs (Collins+, 2013)
J/ApJ/767/134 : Abundances of RGB stars in UFD galaxies (Vargas+, 2013)
J/ApJ/765/140 : Stacked spectra of SDSS star forming gal. (Andrews+, 2013)
J/AJ/144/4 : Properties of dwarf galaxies in the LG (McConnachie+, 2012)
J/ApJ/752/45 : SPLASH: spectroscopy of M31 satellites (Tollerud+, 2012)
J/ApJ/751/46 : Spectroscopic observations in VV124 (Kirby+, 2012)
J/MNRAS/421/2998 : NGC 6822 Cepheids JHKs light curves (Feast+, 2012)
J/MNRAS/414/3492 : JHKs photometry of Sculptor dSph galaxy (Menzies+, 2011)
J/MNRAS/411/1013 : CaII triplet in Sextans dSph galaxy (Battaglia+, 2011)
J/ApJ/726/108 : Dispersion-supported stellar systems (Tollerud+, 2011)
J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)
J/ApJ/718/530 : Leo IV g- and r-band photometry (Sand+, 2010)
J/ApJ/711/361 : Local Group dE galaxies. II. (Geha+, 2010)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/ApJS/182/216 : Surface photometry of Virgo ellipticals (Kormendy+, 2009)
J/AJ/137/3100 : Radial velocities of 4 dSph galaxies (Walker+, 2009)
J/ApJ/682/1217 : Abundances in red giants in globular clusters (Kirby+, 2008)
J/ApJ/657/241 : Spectroscopy of Leo I red giants (Koch+, 2007)
J/A+A/467/1025 : JHK photometry of Fornax RGB stars (Gullieuszik+, 2007)
J/AJ/133/2393 : UBVRI phot. in 7 Local Group dwarfs galaxies (Massey+, 2007)
J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/AJ/131/332 : Velocities of individual stars in NGC 205 (Geha+, 2006)
J/AJ/128/16 : HIPASS Bright Galaxy Catalog (Koribalski+, 2004)
J/AJ/127/840 : VRI photometry of Fornax red giants (Pont+, 2004)
J/A+A/407/423 : Coma cluster early-type galaxies. III. (Mehlert+, 2003)
J/MNRAS/327/918 : CaII in extragalactic red giants (Tolstoy+, 2001)
J/AJ/118/1671 : Fornax cluster 4 VI photometry (Buonanno+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Host Host of dwarf galaxies (MW:Milky Way;
LG:local group or M31)
5- 8 A4 --- Type Galaxy type (dSph/dE or dIrr)
10- 26 A17 --- Name Dwarf galaxy name
28 A1 --- f_Name Controversial galaxy classification (1)
30- 31 I2 h RAh Hour of right ascension (J2000)
33- 34 I2 min RAm Arcminute of right ascension (J2000)
36- 37 I2 s RAs Arcsecond of right ascension (J2000)
39 A1 --- DE- Sign of declination (J2000)
40- 41 I2 deg DEd Degree of declination (J2000)
43- 44 I2 arcmin DEm Arcminute of declination (J2000)
46- 47 I2 arcsec DEs Arcsecond of declination (J2000)
49- 52 F4.2 [Msun] logM* [3/8.7] Log of stellar mass
54- 57 I4 kpc DMW [38/1367]? Distance to Milky Way
59- 62 I4 kpc DM31 [40/1395]? Distance to M31
64 A1 --- l_Vrot/sig Limit flag on Vrot/sig
66- 68 F3.1 --- Vrot/sig [0.3/8.1]? Ratio of rotation velocity to
velocity dispersion
70- 75 F6.4 --- MHI/M* [0/3.7]? HI mass to stellar mass ratio
76 A1 --- f_MHI/M* [b] HI along line of sight only (2)
78- 84 A7 --- Gal Abbreviated name of dwarf galaxy as in table 3
(column added by CDS)
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Note (1): Flag as follows:
c = Transition dwarf galaxies, alternately notated as dTs or dIrr/dSphs.
d = These galaxies are traditionally classified as dEs, but they have the
same properties as high-luminosity dSphs (see Section 2.1).
e = McConnachie et al. (2008ApJ...688.1009M 2008ApJ...688.1009M) and McConnachie (2012,
J/AJ/144/4) classified Andromeda XVIII as an isolated dSph, but we list
it in the M31 system anyway.
Note (2): Some HI has been detected along the line of sight to these galaxies
(Carignan et al. 1998AJ....116.1690C 1998AJ....116.1690C; Bouchard et al. 2006AJ....131.2913B 2006AJ....131.2913B),
but it is probably not associated with these galaxies (Grcevich & Putman
2009ApJ...696..385G 2009ApJ...696..385G).
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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- 12 A12 --- Name Galaxy name
14 A1 --- n_Name [ab] Note about previous observations (1)
16- 21 A6 --- Slit Slitmask
23- 25 I3 --- N [64/199] Number of red giant candidates
27- 30 F4.1 h Exp [1/10.3] Exposure time
32- 42 A11 "YYYY/MMM/DD" Date UT date of observation
44- 46 F3.1 arcsec Seeing [0.4/1.2] Seeing
48- 74 A27 s IExp Individual exposures
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Note (1): Flag as follows:
a = Kirby et al. (2012, J/ApJ/751/46) originally published these observations
of VV124.
b = Simon & Geha (2007ApJ...670..313S 2007ApJ...670..313S) originally published these
observations of Leo T.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Gal Dwarf galaxy abbreviated name
9- 18 A10 --- Name Star name
20- 21 I2 h RAh Hour of Right Ascension (J2000)
23- 24 I2 min RAm Minute of Right Ascension (J2000)
26- 30 F5.2 s RAs Second of Right Ascension (J2000)
32 A1 --- DE- Sign of the Declination (J2000)
33- 34 I2 deg DEd Degree of Declination (J2000)
36- 37 I2 arcmin DEm Arcminute of Declination (J2000)
39- 42 F4.1 arcsec DEs Arcsecond of Declination (J2000)
44 A1 --- n_mag1 ? First filter (B, V, g or M) (1)
46- 51 F6.3 mag mag1 [16.7/26.4]? Extinction-corrected magnitude
in Filt1
53- 57 F5.3 mag e_mag1 [0/0.9]? Uncertainty in mag1
59- 60 A2 --- n_mag2 Second filter (V, R, I, i, r or T2) (1)
62- 67 F6.3 mag mag2 [15.2/23.7] Extinction-corrected magnitude
in Filt2
69- 73 F5.3 mag e_mag2 [0/0.3] Uncertainty in mag2
75 A1 --- n_mag3 ? Third filter (I or i) (1)
77- 82 F6.3 mag mag3 [15.8/22.6]? Extinction-corrected magnitude
in Filt3
84- 88 F5.3 mag e_mag3 [0.001/1.1]? Uncertainty in mag3
90- 93 I4 K Teff [3500/6782] Effective temperature
95- 97 I3 K e_Teff [0/479] Uncertainty in Teff
99-102 F4.2 [cm/s2] log(g) [0/3.6] Log of surface gravity
104-107 F4.2 [cm/s2] e_log(g) [0.02/0.8] Uncertainty in log(g)
109-112 F4.2 km/s vt [1.2/2.2] Microturbulent velocity ξ
114-118 F5.2 [Sun] [Fe/H] [-4/-0.01] Iron abundance relative to the Sun
120-123 F4.2 [Sun] e_[Fe/H] [0.1/1] Uncertainty in [Fe/H]
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Note (1): The photometric filter set varies from galaxy to galaxy; including
Washington M and T2 magnitudes; Johnson/Cousins B, V, R, and I
magnitudes; and SDSS g, r, and i magnitudes. See section 3.2.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Apr-2015