J/ApJ/908/20 On use of field RR Lyrae as galactic probes. II. (Crestani+, 2021)
On the Use of Field RR Lyrae as Galactic Probes.
II. A New ΔS Calibration to Estimate Their Metallicity
Crestani J., Fabrizio M., Braga V.F., Sneden C., Preston G., Ferraro I.,
Iannicola G., Bono G., Alves-Brito A., Nonino M., D'Orazi V., Inno L.,
Monelli M., Storm J., Altavilla G., Chaboyer B., Dall'Ora M., Fiorentino G.,
Gilligan C., Grebel E.K., Lala H., Lemasle B., Marengo M., Marinoni S.,
Marrese P.M., Martinez-Vazquez C.E., Matsunaga N., Mullen J.P., Neeley J.,
Prudil Z., da Silva R., Stetson P.B., Thevenin F., Valenti E., Walker A.,
Zoccali M.
<Astrophys. J., 908, 20 (2021)>
=2021ApJ...908...20C 2021ApJ...908...20C
ADC_Keywords: Stars, variable; Spectra, optical; Spectra, infrared;
Abundances, [Fe/H] ; Effective temperatures
Keywords: RR Lyrae variable stars ; Milky Way stellar halo ; High
resolution spectroscopy ; Metallicity
Abstract:
We performed the largest and most homogeneous spectroscopic survey of
field RR Lyraes (RRLs). We secured ∼6300 high-resolution (HR, R∼35000)
spectra for 143 RRLs (111 fundamental, RRab; 32 first-overtone, RRc).
The atmospheric parameters were estimated by using the traditional
approach and the iron abundances were measured by using an LTE line
analysis. The resulting iron distribution shows a well-defined
metal-rich tail approaching solar iron abundance. This suggests that
field RRLs experienced a complex chemical enrichment in the early halo
formation. We used these data to develop a new calibration of the
ΔS method. This diagnostic, based on the equivalent widths of
CaIIK and three Balmer (Hδ,γ,β) lines, traces the
metallicity of RRLs. For the first time, the new empirical
calibration: (I) includes spectra collected over the entire pulsation
cycle; (II) includes RRc variables; (III) relies on spectroscopic
calibrators covering more than three dex in iron abundance; and (IV)
provides independent calibrations based on one/two/three Balmer lines.
The new calibrations were applied to a data set of both SEGUE-SDSS and
degraded HR spectra totalling 6451 low-resolution (R∼2000) spectra for
5001 RRLs (3439 RRab, 1562 RRc). This resulted in an iron distribution
with a median η=-1.55±0.01 and σ=0.51dex, in good
agreement with literature values. We also found that RRc are 0.10dex
more metal-poor than RRab variables, and have a distribution with a
smoother metal-poor tail. This finding supports theoretical
prescriptions suggesting a steady decrease in the RRc number when
moving from metal-poor to metal-rich stellar environments.
Description:
We have collected a sample of 6631 spectra for 266 stars (173 RRab, 92
RRc, and 1 RRd) across the pulsation phase from multiple medium and
high-resolution spectrographs. The largest and most homogeneous
subsample was collected with the echelle spectrograph at du Pont (Las
Campanas Observatory) and includes 6070 (R=35000) spectra of 186 RRL
(107 RRab, 79 RRc). It typically covers wavelengths from 3600 to
9300Å.
These data were complemented with 530 optical spectra from the ESO
Archive. We included spectra from UVES and X-shooter at Very Large
Telescope (VLT; Cerro Paranal Observatory), High Accuracy Radial
velocity Planet Searcher (HARPS) at the 3.6m telescope (La Silla
Observatory), and Fiber-fed Extended Range Optical Spectrograph
(FEROS) at the 2.2m telescope (La Silla Observatory). An additional
ten spectra were added from HARPS-N at the Telescopio Nazionale
Galileo (Roque de Los Muchachos Observatory), along with four from
High Resolution Spectrograph (HRS) at South African Astronomical
Observatory (SALT), six from the High Dispersion Spectrograph (HDS) at
Subaru National Astronomical Observatory of Japan, and eleven from the
echelle spectrograph at STELLA.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 132 143 Identification, photometric characteristics,
classification, and number of spectra for the CHR
table2.dat 167 171 Atmospheric parameters derived in this work for
each individual measurement
table3.dat 36 471 List of FeI and FeII lines adopted in this work
for the determination of atmospheric parameters
table5.dat 59 143 Adopted metallicities and uncertainties for each
individual star in the CHR sample.
table7.dat 125 6327 Individual measurements of the equivalent widths of
interest for the CHR sample
table9.dat 324 143 The [Fe/H]ΔS measurements for the CHR sample
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See also:
II/264 : ASAS Variable Stars in Southern hemisphere (Pojmanski+, 2002-2005)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/AJ/108/1016 : Kinematics of local RR lyrae stars. I. (Layden, 1994)
J/AJ/110/2319 : Abundances in RR Lyr variables (Clementini+ 1995)
J/A+AS/121/327 : RR Lyr pulsational model (Bono+ 1997)
J/A+A/421/937 : Metal abundances of LMC RR Lyrae (Gratton+, 2004)
J/MNRAS/396/553 : Galactic RR Lyrae data (Dambis, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJS/197/29 : Chemical compositions of 11 RR Lyrae (For+, 2011)
J/MNRAS/435/3206 : Properties of field RR Lyrae variables (Dambis+, 2013)
J/ApJ/763/32 : Galactic halo RRab stars from CSS (Drake+, 2013)
J/ApJ/765/154 : RR Lyrae stars in the Catalina Sky Survey (Drake+, 2013)
J/ApJS/215/23 : FeI radiative lifetime & branching fractions (Den Hartog+,2014)
J/ApJ/782/59 : Abundances 8 RR Lyrae subclass C variable stars (Govea+, 2014)
J/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/MNRAS/447/2404 : Equivalent width of 21 RR Lyrae stars (Pancino+, 2015)
J/MNRAS/446/2251 : Southern Catalina Survey type-ab RR Lyrae (Torrealba+, 2015)
J/AJ/152/170 : RRLs in globulars. IV. UBVRI photometry OmegaCen (Braga+, 2016)
J/MNRAS/469/3688 : CSS Periodic Variable Star Catalogue (Drake+, 2017)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
J/ApJ/848/68 : Abundances & RVs of stable & Blazhko RRc stars (Sneden+, 2017)
J/AJ/155/137 : RRLs in globulars. V.ω Centauri NIR photo. (Braga+, 2018)
J/ApJ/864/57 : Abundances of field & GC RR Lyrae. I. NGC3201 (Magurno+, 2018)
J/ApJ/870/115 : Reddening, distance modulus & Fe/H RRLs in wCen (Bono+, 2019)
J/ApJ/881/104 : Spectroscopic obs. of RR Lyrae in NGC5139 (Magurno+, 2019)
J/AJ/158/16 : Identification of RR Lyrae stars from the DES (Stringer+, 2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR2 identification
21- 40 A20 --- Name Object name
42- 61 F20.16 deg RAdeg [0.7/355] Right ascension (J2000)
63- 83 F21.17 deg DEdeg [-85/57] Declination (J2000)
85- 91 F7.4 mag Vmag [8.96/17.3] Mean V-band magnitude
93- 98 F6.4 mag Vamp [0.25/1.84] V-band amplitude
100-117 F18.16 d Per [0.21/0.96] Period
119-122 A4 --- Class Pulsation mode
124-126 A3 --- Blazhko Blazhko modulation
128-132 F5.1 --- N [1/365] Number of spectra
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR2 identification
21- 40 A20 --- Name Object name
42- 45 A4 --- Class Pulsation mode
47- 54 A8 --- Spect Spectrograph identification
56- 59 I4 K Teff [5750/8210] Effective temperature
61- 63 I3 K e_Teff [0/940] Uncertainty in Teff
65- 68 F4.2 --- logg [0.79/4] Surface gravity
70- 89 F20.18 --- e_logg [0.04/0.5] Uncertainty in logg
91- 94 F4.2 km/s Vt [1.19/5.82] Microturbulent velocity
96-106 F11.9 km/s e_Vt [0.05/2.5] Uncertainty in Vt
108-127 F20.17 --- [FeI/H] [-3.12/0.18] Median Solar-scaled FeI abundance
of neutral iron lines
129-133 F5.3 --- e_[FeI/H] [0.06/0.3] Uncertainty in [FeI/H]
135-137 I3 --- NFeI [9/234] Number of neutral FeI lines
139-158 F20.17 --- [FeII/H] [-3.12/0.18] Median Solar-scaled FeII abundance
of singly ionized iron lines
160-164 F5.3 --- e_[FeII/H] [0.01/0.9] Uncertainty [FeII/H]
166-167 I2 --- NFeII [2/39] Number of singly ionized FeII lines
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.2 0.1nm Wave [3763/8847] Vacuum wavelength
9- 12 F4.1 --- Species [26/27] Species
14- 18 F5.3 eV EP [0/6.23] Excitation potential
20- 25 F6.3 [-] loggf [-6.48/0.65] Oscillator strength
27- 36 A10 --- Ref Line parameters reference (1)
--------------------------------------------------------------------------------
Note (1): The prefix NIST denotes the line had its transition
parameters updated by NIST. References as follows:
BAR91 = Bard+, 1991A&A...248..315B 1991A&A...248..315B
BAR94 = Bard & Kock, 1994A&A...282.1014B 1994A&A...282.1014B
BEL17 = Belmonte+, 2017ApJ...848..125B 2017ApJ...848..125B
BLA79 = Blackwell+, 1979MNRAS.186..657B 1979MNRAS.186..657B
BLA82 = Blackwell+, 1982MNRAS.199...43B 1982MNRAS.199...43B
BLA86 = Blackwell+, 1986MNRAS.220..549B 1986MNRAS.220..549B
BRI74 = Bridges & Kornblith, 1974ApJ...192..793B 1974ApJ...192..793B
DEN14 = Den Hartog+, 2014, J/ApJS/215/23
KOC84 = Kock+, 1984PhST....8...84K 1984PhST....8...84K
LAWLER = Den Hartog+, 2019ApJS..243...33D 2019ApJS..243...33D
MAY74 = May+, 1974A+AS...18..405M 1974A+AS...18..405M
MELBAR = Melendez & Barbuy, 2009A+A...497..611M 2009A+A...497..611M
OBR91 = O'Brian+, 1991JOSAB...8.1185O 1991JOSAB...8.1185O
RUF14 = Ruffoni+, 2014, J/MNRAS/441/3127
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR2 identification
21- 40 A20 --- Name Object name
42- 45 A4 --- Class Pulsation mode
47- 51 F5.2 --- [Fe/H] [-3.06/0.13] Solar-scaled metallicity
53- 56 F4.2 --- e_[Fe/H] [0/0.3] Uncertainty in [Fe/H]
58- 59 A2 --- Ref Reference code for [Fe/H] (1)
--------------------------------------------------------------------------------
Note (1): An asterisk denotes that the value was derived from a single
measurement, and the uncertainty from the typical instrumental
uncertainty. See text for details. References as follows:
1 = this work
2 = For+, 2011, J/ApJS/197/29
3 = Sneden+, J/ApJ/848/68S
4 = Chadid+, J/ApJ/835/187
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR identification
21- 33 F13.5 d HJD [2452007/2458743] Heliocentric Julian Date
35- 43 F9.7 0.1nm CaIIK [0.01/7.71] Equivalent width of CaII K line
45- 57 F13.7 0.1nm e_CaIIK [0/14688] Uncertainty in CaIIK
59- 68 F10.7 0.1nm Hd [-9.01/9.71] Equivalent width of Hδ line
70- 80 F11.7 0.1nm e_Hd [0.05/261] Uncertainty in Hd
82- 90 F9.7 0.1nm Hg [0.07/9.57] Equivalent width of Hγ line
92-103 F12.7 0.1nm e_Hg [0.05/1592] Uncertainty in Hg
105-113 F9.7 0.1nm Hb [0.09/8.17] Equivalent width of Hβ line
115-125 F11.7 0.1nm e_Hb [0.02/594] Uncertainty in Hb
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 I19 --- Gaia Gaia DR2 identification
21- 24 A4 --- Class Pulsation mode
26- 30 F5.1 --- Nspec [1/365] Number of spectra
32- 51 F20.17 --- dS(HdHgHb) [-2.74/0.08] Median dS considering
Hδ, Hγ, Hβ
53- 72 F20.18 --- e_dS(HdHgHb) [0/0.63] Uncertainty indS(Hd,Hg,Hb)
74- 93 F20.17 --- dS(HdHg) [-2.45/-0.2] Median dS considering
Hδ, Hγ
95-114 F20.18 --- e_dS(HdHg) [0/0.59] Uncertainty in dS(Hd,Hg)
116-135 F20.17 --- dS(HdHb) [-2.74/0.08] Median dS considering
Hδ, Hβ
137-156 F20.18 --- e_dS(HdHb) [0/0.63] Uncertainty in dS(Hd,Hb)
158-177 F20.17 --- dS(HgHb) [-2.73/-0.04] Median dS considering
Hγ, Hβ
179-198 F20.18 --- e_dS(HgHb) [0/0.61] Uncertainty in dS(Hg,Hb)
200-219 F20.17 --- dS(Hd) [-2.44/-0.21] Median dS considering
Hδ
221-240 F20.18 --- e_dS(Hd) [0/0.45] Uncertainty in dS(Hd)
242-261 F20.17 --- dS(Hg) [-2.46/-0.18] Median dS considering Hg
263-282 F20.18 --- e_dS(Hg) [0/0.48] Uncertainty in dS(Hg)
284-303 F20.17 --- dS(Hb) [-2.62/-0.14] Median dS considering Hb
305-324 F20.18 --- e_dS(Hb) [0/0.48] Uncertainty in dS(Hb)
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History:
From electronic version of the journal
References:
Fabrizio et al. Paper I : 2019ApJ...882..169F 2019ApJ...882..169F
Crestani et al. Paper III : 2021ApJ...914...10C 2021ApJ...914...10C
Fabrizio et al. Paper VI : 2021ApJ...919..118F 2021ApJ...919..118F
Braga et al. Paper V : 2021ApJ...919...85B 2021ApJ...919...85B
(End) Prepared by [AAS], Coralie Fix [CDS], 24-Jun-2022