J/A+A/658/A29 LMC classical Cepheids Fe and O content (Romaniello+, 2022)
The iron and oxygen content of LMC classical Cepheids and its implications for
the extragalactic distance scale and Hubble constant.
Equivalent width analysis with Kurucz stellar atmosphere models.
Romaniello M., Riess A., S. Mancino S., Anderson R.I., Freudling W.,
Kudritzki R.-P., Macri L., Mucciarelli A., Yuan W.
<Astron. Astrophys. 658, A29 (2022)>
=2022A&A...658A..29R 2022A&A...658A..29R (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Abundances ; Optical
Keywords: techniques: spectroscopic - stars: variables: Cepheids -
Magellanic Clouds - dark energy - distance scale
Abstract:
Classical Cepheids are primary distance indicators and a crucial
stepping stone to determining the present-day value of the Hubble
constant Ho to the precision and accuracy required to constrain
apparent deviations from the LCDM Concordance Cosmological Model. We
have measured the iron and oxygen abundances of a statistically
significant sample of 89 Cepheids in the LMC, one of the anchors of
the local Distance Scale, quadrupling the prior sample and including
68 of the 70 Cepheids used to constrain Ho by the SH0ES program. The
goal is to constrain the extent to which the Cepheid luminosity is
influenced by their chemical composition, which is an important
contributor to the uncertainty on the determination of the Hubble
Constant itself and a critical factor in the internal consistency of
the distance ladder. We have derived stellar parameters and chemical
abundances from a self-consistent spectroscopic analysis based on
Equivalent Width of absorption lines. The iron distribution of
Cepheids in the LMC can be very accurately described by a single
Gaussian with a mean [Fe/H]=-0.409±0.003dex and
sigma=0.076±0.003dex. We estimate a systematic uncertainty on the
absolute mean values of 0.1dex. The width of the distribution is fully
compatible with the measurement error and supports the low dispersion
of 0.069 mag seen in the NIR HST LMC period-luminosity relation. The
uniformity of the abundance has the important consequence that the LMC
Cepheids alone cannot provide any meaningful constraint on the
dependence of the Cepheid Period-Luminosity relation on chemical
composition at any wavelength. This revises a prior claim based on a
small sample of 22 LMC Cepheids that there was little dependence (or
uncertainty) between composition and NIR luminosity, a conclusion
which would produce an apparent conflict between anchors of the
distance ladder with different mean abundance. The chemical
homogeneity of the LMC Cepheid population makes it an ideal
environment to calibrate the metallicity dependence between the more
metal poor SMC and metal rich Milky Way and NGC 4258.
Description:
We assembled our sample of 89 Classical Cepheids in the LMC by
combining proprietary data for 67 out of the 70 stars that define the
SH0ES fiducial PL relation (Riess et al., 2019ApJ...876...85R 2019ApJ...876...85R, Cat.
J/ApJ/876/85) with 22 archival spectra observed in the same
instrumental setup. For the mentioned sample of 67 stars, this is the
first measurement of their chemical composition. Iron abundances for
the other ones were published by Romaniello et al.
(2008A&A...488..731R 2008A&A...488..731R, OGLE510/HV879 is in common between the two
samples and is considered here only once).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 82 Log of the spectroscopic observations of
the 68 SH0ES Cepheids (updated version,
24-May-2022, from erratum 2022A&A...662C...1R 2022A&A...662C...1R)
table2.dat 27 219 List of the 189 FeI, 28 FeII and 2 OI lines
used as input in the analysis
table3.dat 42 68 Stellar parameters as derived in the abundance
analysis for the SH0ES sample
table4.dat 41 21 Stellar parameters as re-derived here in the
abundance analysis for the archival sample
table5.dat 48 68 Stellar iron abundances for the SH0ES sample
table6.dat 48 21 Stellar iron abundances from the re-analysis
of the archival sample
table7.dat 22 68 Stellar oxygen abundances for the SH0ES sample
table8.dat 22 21 Stellar oxygen abundances from the re-analysis
of the archival sample
tablea1.dat 79 35 Content of the GALA configuration file
autofl.param
appenb/* . 89 Appendix B individual GALA input files
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See also:
J/AcA/65/297 : OGLE4 LMC and SMC Cepheids (Soszynski+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name, OGLENNNN for OGLE-LMC-CEP-XXXX
10- 32 A23 --- FileName Timestamp ESO archive file name: UVES.timestamp
34- 44 F11.5 d MJD [51828.19/59170.33] Modified Julian date
(JD-2400000.5)
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.3 0.1nm lambda [4892.85/6400.32] Line wavelength
10- 13 A4 --- Ion Ion
15- 21 F7.3 [-] log(gf) [-10.26/0.78] Oscillator strength (1)
23- 27 F5.2 eV EP Excitation Potential (1)
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Note (1): https://wwwuser.oats.inaf.it/castelli/linelists.html .
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Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Star name, OGLENNNN for OGLE-LMC-CEP-XXXX (1)
10- 13 I4 K Teff [4830/6420] effective temperature
15- 17 I3 K e_Teff [36/322] Uncertainty on effective temperature
19- 21 F3.1 [cm/s2] logg Log surface gravity
23- 26 F4.2 [cm/s2] e_logg [0.04/0.26] Uncertainty on log surface gravity
28- 30 F3.1 km/s vturb [2.6/4.0] Microturbulent velocity
32- 35 F4.2 km/s e_vturb [0.06/1.04] Uncertainty on microturbulent
velocity
37- 42 F6.4 --- Phase [0.0/0.99] Pulsational phase at observation
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Note (1): OGLE510/HV879 is common to both samples and is considered here
only in Table 3.
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Byte-by-byte Description of file: table[56].dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name, OGLENNNN for OGLE-LMC-CEP-XXXX
10- 14 F5.2 --- [FeI/H] [-0.79/-0.13] [FeI/H]=A(FeI)-7.50 (1)
16- 19 F4.2 --- s_[FeI/H] [0.07/0.16] Standard deviation [FeI/H]
21- 24 F4.2 --- e_[FeI/H] [0.03/0.23] Uncertainty [FeI/H] (2)
26- 28 I3 --- o_FeI [52/108] Number of FeI lines used
30- 34 F5.2 --- [FeII/H] [-0.82/-0.13] [FeII/H]=A(FeII)-7.50 (1)
36- 39 F4.2 --- s_[FeII/H] [0.02/0.21] Standard deviation [FeII/H]
41- 45 F5.2 --- e_[FeII/H] [-0.02/0.17] Uncertainty [FeII/H] (2)
47- 48 I2 --- o_FeII [6/18] Number of FeII lines used
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Note (1): Asplund et al 2009ARA&A..47..481A 2009ARA&A..47..481A
Note (2): Cayrel et al. 2004A&A...416.1117C 2004A&A...416.1117C
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Byte-by-byte Description of file: table[78].dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Star name, OGLENNNN for OGLE-LMC-CEP-XXXX
10- 14 F5.2 --- [OI/H] [-0.61/0.43]? [OI/H]=A(OI)-8.69 (1)
16- 20 F5.2 --- e_[OI/H] [0.02/0.27]? Uncertainty [OI/H] (2)
22 I1 --- o_OI [1/2]? Number of OI lines used
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Note (1): Asplund et al 2009ARA&A..47..481A 2009ARA&A..47..481A
Note (2): Cayrel et al. 2004A&A...416.1117C 2004A&A...416.1117C
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Param Parameter name
10- 15 A6 --- Value Value as used in the analysis
17- 79 A63 --- Description Parameter description
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Byte-by-byte Description of file: appenb/*
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Bytes Format Units Label Explanations
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1- 8 F8.3 0.1nm lambda Line wavelength
10- 16 F7.3 0.0001nm EW Onserved equivalent Width
18- 23 F6.3 0.0001nm e_EW Uncertainty on EW
25- 29 F5.2 --- El Element code (1)
31- 37 F7.3 --- log(gf) Log oscillator strength
39- 44 F6.3 eV EP Excitation potential
46- 50 F5.2 --- log(gamma-rad) Log radial damping constant
52- 56 F5.2 --- log(gamma-stark) Log Stark damping constant
58- 62 F5.2 --- log(gamma-WdV) Log Van der Waals damping constant
64- 66 F3.1 --- alphaBarklem Velocity parameter alpha (2)
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Note (1): Kurucz notation, e.g. 26.00=FeI, 26.01=FeII
Note (2): Barklem, Piskunov, & O'Mara, 2000A&AS..142..467B 2000A&AS..142..467B, Cat. J/A+AS/142/467
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Acknowledgements:
Martino Romaniello, martino.romaniello(at)gmail.com
History:
27-Jan-2022: on-line version
24-May-2022: updated table1
(End) Patricia Vannier [CDS] 20-Nov-2021