J/A+A/566/A37 Iron abundances for 42 Galactic Cepheids (Genovali+, 2014)
On the fine structure of the Cepheid metallicity gradient in the Galactic
thin disk.
Genovali K., Lemasle B., Bono G., Romaniello M., Fabrizio M., Ferraro I.,
Iannicola G., Laney C.D., Nonino M., Bergemann M., Buonanno R.,
Francois P., Inno L., Kudritzki R.-P., Matsunaga N., Pedicelli S.,
Primas F., Thevenin F.
<Astron. Astrophys., 566, A37-37 (2014)>
=2014A&A...566A..37G 2014A&A...566A..37G
ADC_Keywords: Clusters, open ; Stars, variable ; Abundances
Keywords: stars: abundances - stars: variables: Cepheids - stars: oscillations -
Galaxy: disk - open clusters and associations: general
Abstract:
We present homogeneous and accurate iron abundances for 42 Galactic
Cepheids based on high resolution (R∼38000) high signal-to-noise ratio
(S/N≥100) optical spectra collected with UVES at VLT (128 spectra).
The above abundances were complemented with high-quality iron
abundances provided either by our group (86) or available in the
literature. We were careful to derive a common metallicity scale and
ended up with a sample of 450 Cepheids. We also estimated accurate
individual distances for the entire sample by using homogeneous
near-infrared photometry and the reddening free period-Wesenheit
relations. The new metallicity gradient is linear over a broad range
of Galactocentric distances (RG∼5-19kpc) and agrees quite well with
similar estimates available in the literature (-0.060±0.002dex/kpc).
We also uncover evidence that suggests that the residuals of the
metallicity gradient are tightly correlated with candidate Cepheid
groups (CGs). The candidate CGs have been identified as spatial
overdensities of Cepheids located across the thin disk. They account
for a significant fraction of the residual fluctuations, and also for
the large intrinsic dispersion of the metallicity gradient. We
performed a detailed comparison with metallicity gradients based on
different tracers: OB stars and open clusters. We found very similar
metallicity gradients for ages younger than 3Gyr, while for older ages
we found a shallower slope and an increase in the intrinsic spread.
The above findings rely on homogeneous age, metallicity, and distance
scales. Finally, by using a large sample of Galactic and Magellanic
Cepheids for which accurate iron abundances are available, we found
that the dependence of the luminosity amplitude on metallicity is
vanishing.
Description:
In this investigation we present a spectral analysis based on
high-resolution (R∼38000) spectra collected with the UVES
spectrograph available at the Nasmyth B focus of UT2/VLT Cerro Paranal
telescope. Multi-epoch spectra for eleven Galactic Cepheids were
collected during observing run B (P89). This sample includes 44
high-resolution spectra (from four to six spectra per star) for a
total of eleven Cepheids. The covered spectral range is 4726-5804Å
and 5762-6835Å over the two chips, collected by only using the red
arm configuration and the cross disperser CD 3 (central wavelength at
580nm). The S/N ranges from ∼50 to ∼300 (see Fig. 1). The seeing
during the observations ranged from 0.5-arcsec to 2.5-arcsec, with a
typical mean value of 1.2-arcsec, while the exposure times changed
from 20s to 1400s.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 95 42 Mean NIR magnitudes, mean distances and mean iron
abundances for the current sample of classical
Cepheids
table4.dat 95 375 Galactic Cepheids for which the iron abundance
was available in the literature
table5.dat 77 67 Individual ages, distances, and metallicities
for the current sample of open clusters
table6.dat 81 10 Structural parameters and metallicities of
the candidate Cepheid groups
--------------------------------------------------------------------------------
See also:
J/A+A/511/A56 : Abundances of five open clusters (Pancino+, 2010)
J/AJ/142/51 : Galactic Cepheids abundance variations (Luck+, 2011)
J/AJ/142/136 : Spectroscopy of Cepheids. l=30-250° (Luck+, 2011)
J/A+A/554/A132 : Iron line list (FeI and FeII) (Genovali+, 2013)
Byte-by-byte Description of file: table3.dat table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Variable name
11- 18 A8 --- VType Variable type (from GCVS) (1)
20- 26 F7.4 [d] logPer logarithmic period
28- 33 F6.3 mag <Jmag> Mean J magnitude
35- 40 F6.3 mag <Hmag> Mean H magnitude
42- 47 F6.3 mag <Kmag> Mean K magnitude
49- 53 F5.2 [Sun] [Fe/H]l Iron abundance available in the literature
rescaled to our solar abundance
55- 59 F5.2 [Sun] [Fe/H] Current iron abundance
61- 64 F4.2 [Sun] e_[Fe/H] ? rms uncertainty on [Fe/H] (only in table3)
66 I1 --- Nsp ? Number of spectra used to estimate the mean
iron abundance (only in table3)
68- 72 F5.2 mag Mod True distance modulus
74- 77 F4.2 mag e_Mod rms uncertainty on Mod
79- 83 I5 pc Rgal Galactocentric distance (R☉=7.95±0.37kpc)
85- 87 I3 pc e_Rgal rms uncertainty on Rgal
89- 90 A2 --- Notes Notes on the NIR photometry and distances
for individual objects (2)
92- 95 A4 --- Ref References (3)
--------------------------------------------------------------------------------
Note (1): In table4, we note that V556 Cas and V1397 Cyg are misclassified in
the GCVS since they have been identified as classical Cepheids by
Wils & Greaves (2004IBVS.5512....1W 2004IBVS.5512....1W). Moreover, their nature was confirmed
by Luck & Lambert (2011AJ....142..136L 2011AJ....142..136L, Cat J/AJ/142/136) on the basis of
spectroscopic evidence.
Note (2): Notes as follows:
a = Mean magnitudes provided by Monson & Pierce (2011ApJS..193...12M 2011ApJS..193...12M, Cat.
J/ApJS/193/12) transformed into the 2MASS photometric system using the
zero-points given in their Table 1.
b = Mean magnitudes provided by Laney & Stobie (1992A&AS...93...93L 1992A&AS...93...93L) and by
Laney (priv. comm.) transformed into the 2MASS photometric system using
the zero-points provided by Koen et al. (2007MNRAS.380.1433K 2007MNRAS.380.1433K).
+ = objects marked with a "+" (a+ or b+) (Laney, priv. comm.) do not have a
complete coverage of the light-curve (the number of phase points ranges
from 4 to 14).
c = Mean magnitudes based on single-epoch measurements from the 2MASS catalog
and the NIR template light curves provided by Soszynski et al.
(2005PASP..117..823S 2005PASP..117..823S).
* = An asterisk indicates the use of single-epoch photometry in the distance
determination (see Sect. 3 for details). For these stars the magnitudes
listed are the single-epoch measurements retrieved from the 2MASS catalog.
d = The weighted mean of the three true distance moduli. The errors account
for uncertainties affecting the mean magnitudes and for the intrinsic
dispersion of the adopted NIR PW relations.
e = The weighted mean Galactocentric distances were estimated assuming
Rgal=7.94±0.37±0.26kpc (Groenewegen et al., 2008A&A...481..441G 2008A&A...481..441G).
The errors account for uncertainties affecting both the solar
Galactocentric distance and the heliocentric distances.
Note (3): References for the iron estimate. The priority was given, in the
following order, to evaluations from our group:
G13 = Genovali et al. 2013A&A...554A.132G 2013A&A...554A.132G, Cat. J/A+A/554/132
PED = Pedicelli et al. 2010A&A...511A..56P 2010A&A...511A..56P, Cat. J/A+A/511/A56
LEM = Lemasle et al. 2007A&A...467..283L 2007A&A...467..283L, 2008A&A...490..613L 2008A&A...490..613L
ROM = Romaniello et al. 2008A&A...488..731R 2008A&A...488..731R
and from the literature:
LII = Luck et al. (2011AJ....142...51L 2011AJ....142...51L, Cat. J/AJ/142/51)
LIII = Luck & Lambert (2011AJ....142..136L 2011AJ....142..136L, Cat. J/AJ/142/136)
SZI = Sziladi et al. 2007A&A...473..579S 2007A&A...473..579S
YON = Yong et al. 2006AJ....131.2256Y 2006AJ....131.2256Y
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Cluster Cluster name
12- 16 F5.2 Gyr Age Cluster age
18- 21 F4.1 kpc Rgal Galactocentric distance (R☉=7.94±0.37kpc)
23- 27 F5.2 [Sun] [Fe/H]l Iron abundance available in the literature
29- 33 F5.2 [Sun] [Fe/H]r Metallicity rescaled to current solar
abundance
35- 73 A39 --- r_[Fe/H]l Reference for metallicity
75- 77 A3 --- r_Age Reference for age-dist (1)
--------------------------------------------------------------------------------
Note (1): References as follows:
SF = Salaris et al. 2004A&A...414..163S 2004A&A...414..163S; Friel 1995ARA&A..33..381F 1995ARA&A..33..381F
C = Carraro group: Carraro et al. 2002MNRAS.332..705C 2002MNRAS.332..705C, 2005MNRAS.356..647C 2005MNRAS.356..647C,
2005MNRAS.360..655C 2005MNRAS.360..655C, 2005A&A...442..917C 2005A&A...442..917C;
Moitinho et al. 2006A&A...445..493M 2006A&A...445..493M;
Villanova et al. 2007MNRAS.379.1089V 2007MNRAS.379.1089V, 2009A&A...504..845V 2009A&A...504..845V
B = BOCCE: Gratton & Contarini 1994A&A...283..911G 1994A&A...283..911G; Bragaglia et al.
2001AJ....121..327B 2001AJ....121..327B; Kalirai & Tosi 2004MNRAS.351..649K 2004MNRAS.351..649K;
Bragaglia et al. 2006MNRAS.366.1493B 2006MNRAS.366.1493B; Carretta et al.
2004A&A...422..951C 2004A&A...422..951C, 2005A&A...441..131C 2005A&A...441..131C, 2007A&A...473..129C 2007A&A...473..129C
W = WEBDA
YON = Yong et al. 2012AJ....144...95Y 2012AJ....144...95Y
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- ID Cepheid group identification number (I to X)
6- 11 F6.3 kpc X Galactic coordinate X of the group barycenter
13- 18 F6.3 kpc Y Galactic coordinate Y of the group barycenter
20- 25 F6.3 kpc Z Galactic coordinate Z of the group barycenter
27- 32 F6.3 kpc Rgal Galactocentric radius of the group barycenter
34- 38 F5.3 kpc dRgal- Galactocentric distance of the inner edge
of the Cepheid group
40- 44 F5.3 kpc dRgal+ Galactocentric distance of the outer edge
of the Cepheid group
46- 50 F5.3 kpc Diam Diameter of the Cepheid group
52- 53 I2 --- N [6/52] Number of Cepheids per Cepheid group
55- 58 F4.2 d Per [5.08/8.74] Mean period of Cepheids in group
60- 63 F4.2 d e_Per Intrinsic dispersion of Per
65- 68 F4.1 kpc-3 rho Density of tje Cepheid group
70- 75 F6.3 [Sun] D[Fe/H] Mean residual iron abundance Δ[Fe/H]
77- 81 F5.3 [Sun] e_D[Fe/H] Intrinsic dispersion σ(Δ[Fe/H])
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Lemasle et al., Paper I 2007A&A...467..283L 2007A&A...467..283L
Romaniello et al., Paper II 2008A&A...488..731R 2008A&A...488..731R
Lemasle et al., Paper III 2008A&A...490..613L 2008A&A...490..613L
Pedicelli et al., Paper IV 2009A&A...504...81P 2009A&A...504...81P
Pedicelli et al., Paper V 2010A&A...518A..11P 2010A&A...518A..11P
Genovali et al., Paper VI 2013A&A...554A.132G 2013A&A...554A.132G, Cat. J/A+A/554/A132
Lemasle et al., Paper VII 2013A&A...558A..31L 2013A&A...558A..31L
(End) Patricia Vannier [CDS] 08-Sep-2014