J/ApJ/914/10  Field RR Lyrae as Gal. probes. III. Abundances  (Crestani+, 2021)

On the use of field RR Lyrae as Galactic probes. III. The α-element abundances. Crestani J., Braga V.F., Fabrizio M., Bono G., Sneden C., Preston G., Ferraro I., Iannicola G., Nonino M., Fiorentino G., Thevenin F., Lemasle B., Prudil Z., Alves-Brito A., Altavilla G., Chaboyer B., Dall'Ora M., D'Orazi V., Gilligan C., Grebel E.K., Koch-Hansen A.J., Lala H., Marengo M., Marinoni S., Marrese P.M., Martinez-Vazquez C., Matsunaga N., Monelli M., Mullen J.P., Neeley J., da Silva R., Stetson P.B., Salaris M., Storm J., Valenti E., Zoccali M. <Astrophys. J., 914, 10 (2021)> =2021ApJ...914...10C 2021ApJ...914...10C
ADC_Keywords: Abundances; Stars, variable; Spectra, optical Keywords: RR Lyrae variable stars ; Pulsating variable stars ; Milky Way stellar halo ; High resolution spectroscopy ; Spectroscopy Abstract: We provide the largest and most homogeneous sample of α-element (Mg, Ca, Ti) and iron abundances for field RR Lyrae (RRLs; 162 variables) by using high-resolution spectra. The current measurements were complemented with similar abundances available in the literature for 46 field RRLs brought to our metallicity scale. We ended up with a sample of old (t≥10Gyr), low-mass stellar tracers (208 RRLs: 169 fundamental, 38 first overtone, and 1 mixed mode) covering 3dex in iron abundance (-3.00≤[Fe/H]≤0.24). We found that field RRLs are ∼0.3dex more α poor than typical halo tracers in the metal-rich regime ([Fe/H]≥-1.2), while in the metal-poor regime ([Fe/H]≤-2.2) they seem to be on average ∼0.1dex more α enhanced. This is the first time that the depletion in α elements for solar iron abundances is detected on the basis of a large, homogeneous, and coeval sample of old stellar tracers. Interestingly, we also detected a close similarity in the [α/Fe] trend between α-poor, metal-rich RRLs and red giants (RGs) in the Sagittarius dwarf galaxy as well as between α-enhanced, metal-poor RRLs and RGs in ultrafaint dwarf galaxies. These results are supported by similar elemental abundances for 46 field horizontal branch stars. These stars share with RRLs the same evolutionary phase and the same progenitors. This evidence further supports the key role that old stellar tracers play in constraining the early chemical enrichment of the halo and, in particular, in investigating the impact that dwarf galaxies have had in the mass assembly of the Galaxy. Description: We collected a sample of 407 high-resolution (HR; R≳18400) spectra for 162 field RR Lyrae (RRLs: 138 RRab, 23 RRc, 1 RRd). In order to obtain a high-enough S/N (≳50 per pixel) for chemical abundance analysis, we stacked low-S/N spectra of the same star acquired at the same phase and with the same spectrograph, as described in more detail in Section 2. This process resulted in 243 spectra that were analyzed individually. Among them, 51 were acquired with the echelle spectrograph at du Pont (Las Campanas Observatory), 74 with UVES, and 16 with X-shooter at VLT (ESO, Cerro Paranal Observatory); 18 with HARPS at the 3.6m telescope and 2 with FEROS at the 2.2m MPG telescope (ESO, La Silla Observatory); 5 with HARPS-N at the Telescopio Nazionale Galileo (Roque de Los Muchachos Observatory); 47 with HRS at SALT (South African Astronomical Observatory); 28 with the High Dispersion Spectrograph (HDS) at Subaru (National Astronomical Observatory of Japan); and 2 with the echelle spectrograph at STELLA (Izana Observatory, Tenerife, Spain). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 121 208 Basic information of the entire RR Lyrae sample table3.dat 68 33 RRL abundances adopted from the literature table4.dat 89 243 Atmospheric parameters derived in this work for each individual measurement table5.dat 33 86 List of α-element transitions adopted in this work table6.dat 86 254 Final abundances for all the RR Lyrae and "Lit-HB" samples in our metallicity and α-element abundance scale -------------------------------------------------------------------------------- See also: VII/195 : Globular Clusters in the Milky Way (Harris, 1996) VII/202 : Globular Clusters in the Milky Way (Harris, 1997) J/AJ/110/2319 : Abundances in RR Lyr variables (Clementini+ 1995) J/MNRAS/340/304 : [X/Fe] of Galactic disc F and G dwarfs (Reddy+, 2003) J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004) J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004) J/AJ/130/2140 : Abundances & velocities in globular clusters (Pritzl+, 2005) J/MNRAS/367/1329 : Elemental abundances for 176 stars (Reddy+, 2006) J/A+A/465/815 : Abundances of Sgr dSph stars (Sbordone+, 2007) J/AJ/135/1580 : Abundances in 10 red giants of Car dSph (Koch+, 2008) J/A+A/505/139 : Abundances of red giants in 17 GCs (Carretta+, 2009) J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009) J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009) J/ApJ/712/L21 : Calcium abundances in 17 globular clusters (Carretta+, 2010) J/A+A/520/A95 : Abundances of red giants in M54 & Sgr dSph (Carretta+, 2010) J/AJ/140/1694 : Abundances of non-variable red & blue HB stars (For+, 2010) J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010) J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010) J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010) J/A+A/511/L10 : Abundances and space velocities of 94 stars (Nissen+, 2010) J/A+A/511/A56 : Abundances of five open clusters (Pancino+, 2010) J/ApJS/197/29 : Chemical compositions of 11 RR Lyrae (For+, 2011) J/A+A/530/A54 : Abundances of 650 bulge red giants (Gonzalez+, 2011) J/ApJ/778/149 : Abundances for 3 stars in Sgr dSph (McWilliam+, 2013) J/ApJ/767/134 : Abundances of red giant stars in UFD gal. (Vargas+, 2013) J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013) J/A+A/562/A71 : Abundances of solar neighbourhood dwarfs (Bensby+, 2014) J/ApJ/782/59 : Abundances of RR Lyrae subclass C var. stars (Govea+, 2014) J/A+A/572/A82 : Abundances in outer parts of Fornax dSph (Hendricks+, 2014) J/A+A/572/A88 : Equivalent widths for Fornax RGB stars (Lemasle+, 2014) J/A+A/580/A18 : Carina Project VIII. α-element abund (Fabrizio+, 2015) J/A+A/584/A46 : GIRAFFE Inner Bulge Survey (GIBS). II. (Gonzalez+, 2015) J/MNRAS/447/2404 : Equivalent width of 21 RR Lyrae stars (Pancino+, 2015) J/A+A/587/A124 : Metal-poor stars towards the Galactic bulge (Koch+, 2016) J/ApJ/848/68 : Abund. & RVs of stable and Blazhko RRc stars (Sneden+, 2017) J/AJ/155/240 : A spectroscopic survey of field RHB stars (Afsar+, 2018) J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018) J/ApJS/237/13 : Yields of 13-120M massive stars (Limongi+, 2018) J/ApJ/870/2 : CCSN to explosions in spheric symmetry. III. (Curtis+, 2019) J/A+A/623/A116 : Gal. Cepheids & RR Lyrae multiplicity. I. (Kervella+, 2019) J/MNRAS/492/3408 : Galactic disc RR Lyrae stars (Prudil+, 2020) J/A+A/641/A127 : 13 dsph and ultra-faint galaxies analysis (Reichert+, 2020) J/ApJ/908/20 : Field RR Lyrae as gal. probes. II. (Crestani+, 2021) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 I19 --- GaiaDR2 Gaia DR2 identification 21- 40 A20 --- OName Other name for the star 42- 61 F20.16 deg RAdeg Right ascension (ICRS) at Epoch=2015.5 63- 83 F21.17 deg DEdeg [-84.41/69.52] Declination (ICRS) at Epoch=2015.5 85- 91 F7.4 mag Vmag [7.78/17.24] Mean V-band magnitude 93- 98 F6.4 mag Vamp [0.25/1.31] V-band amplitude 100-108 F9.7 d Per [0.2/0.81] Period 110-113 A4 -- Class Pulsation mode ("RRab", "RRc" or "RRd") 115-121 A7 -- Sample Sample ("Lit-RRL" or "TW-RRL"=this work; 162 occurrences) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 I19 --- GaiaDR2 Gaia DR2 identification 21- 26 F6.3 [-] [Fe/H]o [-2.9/-0.21] Solar-scaled metallicity in the literature source (1) 28- 31 F4.2 [-] [Mg/Fe]o [0.21/0.63]? Solar-scaled magnesium abundance in the literature source (1) 33- 37 F5.2 [-] [Ca/Fe]o [-0.11/0.52]? Solar-scaled calcium abundance in the literature source (1) 39- 42 F4.2 [-] [Ti/Fe]o [0.18/0.8]? Solar-scaled titanium abundance in the literature source (1) 44- 48 F5.2 [-] [Fe/H] [-2.83/-0.21] Solar-scaled metallicity transformed to our scale (1) 50- 53 F4.2 [-] [Mg/Fe] [0/0.6]? Solar-scaled magnesium abundance transformed to our scale (1) 55- 59 F5.2 [-] [Ca/Fe] [-0/0.54]? Solar-scaled calcium abundance transformed to our scale (1) 61- 64 F4.2 [-] [Ti/Fe] [0.28/0.91]? Solar-scaled titanium abundance transformed to our scale (1) 66- 68 A3 --- Ref Literature source (2) -------------------------------------------------------------------------------- Note (1): Iron and α-element abundances in both their original (subscript o) scale and in our scale for the Lit-RRL sample. Note that the values adopted from For & Sneden (2010, J/AJ/140/1694), For et al. (2011, J/ApJS/197/29), Chadid et al. (2017ApJ...835..187C 2017ApJ...835..187C), and Sneden et al. (2017, J/ApJ/848/68) require no shifts to be in our metallicity and α-element abundance scale, and therefore are not included in this table. Note (2): References as follows: C95 = Clementini et al. (1995, J/AJ/110/2319); 8 stars in common with this work (TW-RRL sample); F96 = Fernley & Barnes (1996A&A...312..957F 1996A&A...312..957F); 4 tars in common with this work G14 = Govea et al. (2014, J/ApJ/782/59); 2 stars in common with this work L96 = Lambert et al. (1996ApJS..103..183L 1996ApJS..103..183L); 8 stars in common with this work P15 = Pancino et al. (2015, J/MNRAS/447/2404); 8 stars in common with this work -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 I19 --- GaiaDR2 Gaia DR2 identification 21- 28 A8 --- Inst Spectrograph identification 30- 33 I4 K Teff [5750/8220] Effective temperature 35- 37 I3 K e_Teff [0/940] Uncertainty in Teff 39- 42 F4.2 [cm/s2] log(g) [0.79/4] Log, Surface gravity 44- 47 F4.2 [cm/s2] e_log(g) [0.04/0.42] Uncertainty in log (g) 49- 52 F4.2 km/s Vt [1.19/5.82] Microturbulent velocity, ξt 54- 57 F4.2 km/s e_Vt [0.05/2.5] Uncertainty in Vt 59- 63 F5.2 [-] [FeI/H] [-3.11/0.23] Median Solar-scaled iron abundance of neutral iron lines 65- 68 F4.2 [-] e_[FeI/H] [0.06/0.28] Uncertainty in [FeI/H] 70- 72 I3 --- NFeI [9/234] Number of adopted neutral iron lines 74- 78 F5.2 [-] [FeII/H] [-3.11/0.23] Median Solar-scaled iron abundance of singly ionized iron lines 80- 83 F4.2 [-] e_[FeII/H] [0.01/0.83] Uncertainty [FeII/H] 85- 86 I2 --- NFeII [2/39] Number of adopted singly ionized iron line 89 I1 --- Nstack [1/8] Number of individual spectra stacked for this measurement -------------------------------------------------------------------------------- Byte-by-byte Description of file: table5.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.2 0.1nm lambda [3729.81/8717.83] Vacuum wavelength 9- 12 F4.1 --- Ion [12/22.1] Species 14- 18 F5.3 eV EP [0/5.932] Excitation potential 20- 25 F6.3 [-] log(gf) [-5.62/0.57] log, statistical weight*oscillator strength 27- 33 A7 --- Ref Line parameters reference (1) -------------------------------------------------------------------------------- Note (1): References as follows: NIST = http://www.nist.gov/ LAW2013 = Lawler et al. (2013ApJS..205...11L 2013ApJS..205...11L); WOO2013 = Wood et al. (2013, J/ApJS/208/27). -------------------------------------------------------------------------------- Byte-by-byte Description of file: table6.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 I19 --- GaiaDR2 Gaia DR2 identification 21- 25 F5.2 [-] [Fe/H] [-3.16/0.23] Median Solar-scaled iron abundance 27- 30 F4.2 [-] e_[Fe/H] [0/0.21] Uncertainty in [Fe/H] 32- 36 F5.2 [-] [Mg/Fe] [-0.22/0.79]? Median Solar-scaled magnesium abundance 38- 41 F4.2 [-] e_[Mg/Fe] [0/0.28]? Uncertainty in [Mg/Fe] 43- 47 F5.2 [-] [Ca/Fe] [-0.3/0.62]? Median Solar-scaled calcium abundance 49- 52 F4.2 [-] e_[Ca/Fe] [0.01/0.28]? Uncertainty in [Ca/Fe] 54- 58 F5.2 [-] [Ti/Fe] [-0.45/0.71]? Median Solar-scaled titanium abundance 60- 63 F4.2 [-] e_[Ti/Fe] [0/0.32]? Uncertainty in [Ti/Fe] 65- 69 F5.2 [-] [a/Fe] [-0.2/0.71] Median Solar-scaled α-element abundance 71- 74 F4.2 [-] e_[a/Fe] [0/0.23] Uncertainty in [alpha/Fe] 76- 82 A7 --- Sample Sample ("Lit-HB", "Lit-RRL" or "TW-RRL"=this work RRL) 84- 86 A3 --- Ref Source (1) -------------------------------------------------------------------------------- Note (1): The stars with Fe, Mg, Ca, and Ti abundances adopted directly (i.e. without averaging with values from multiple sources and without the application of any scale shifts) from the references as follows: F10 = For & Sneden (2010, J/AJ/140/1694); F11 = For et al. (2011, J/ApJS/197/29); C17 = Chadid et al. (2017ApJ...835..187C 2017ApJ...835..187C); S17 = Sneden et al. (2017, J/ApJ/848/68) -------------------------------------------------------------------------------- History: From electronic version of the journal References: Fabrizio et al. Paper I. 2019ApJ...882..169F 2019ApJ...882..169F Crestani et al. Paper II. 2021ApJ...908...20C 2021ApJ...908...20C Cat. J/ApJ/908/20 Crestani et al. Paper III. 2021ApJ...914...10C 2021ApJ...914...10C This catalog Fabrizio et al. Paper IV. 2021ApJ...919..118F 2021ApJ...919..118F Braga et al. Paper V. 2021ApJ...919...85B 2021ApJ...919...85B
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Dec-2022
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