J/MNRAS/501/4596 Temperature and metallicity scale of cool giants (Ghosh+, 2021)
New temperature and metallicity scale of cool giants from K-band spectra.
Ghosh S., Ojha D.K., Ninan J.P.
<Mon. Not. R. Astron. Soc., 501, 4596-4609 (2021)>
=2021MNRAS.501.4596G 2021MNRAS.501.4596G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Effective temperatures ; Abundances, [Fe/H] ;
Equivalent widths ; Milky Way ; Magellanic Clouds ;
Spectra, infrared
Keywords: methods: observational - techniques: spectroscopic -
stars: fundamental parameters - infrared: stars
Abstract:
We present here quantitative diagnostic tools for cool giants that
employ low-resolution near-infrared spectroscopy in the K band for
stellar population studies. In this study, a total of 260 cool giants
(177 stars observed with X-shooter and 83 stars observed with NIFS)
are used covering a wider metallicity range than in earlier works. We
measure equivalent widths of some of the selected important K-band
spectral features like NaI, FeI, and 12CO after degrading the
spectral resolution (R∼1200) to investigate the spectral behaviour
with fundamental parameters (e.g. effective temperature and
metallicity). We derive empirical relations to measure effective
temperature using the 12CO first-overtone band at 2.29 and 2.32µm
and show a detailed quantitative metallicity dependence of these
correlations. We find that the empirical relations based on
solar-neighborhood stars can incorporate large uncertainty in
evaluating Teff for metal-poor or metal-rich stars. Furthermore, we
explore all the spectral lines to establish the empirical relation
with metallicity and find that the quadratic fit of the combination of
NaI and 12CO at 2.29µm lines yields a reliable empirical relation
at [Fe/H]~←0.4dex, while a linear fit of any line offers a good
metallicity scale for stars having [Fe/H]≳0.0dex.
Description:
In this work, we obtain NIR K-band spectra of 83 late-type giants,
observed with the medium spectral resolution (R∼5400) Near-Infrared
Facility Spectrograph (NIFS) on Gemini North within the central 1pc of
the Milky Way nuclear star cluster (Stostad et al.
2015ApJ...808..106S 2015ApJ...808..106S, Cat. J/ApJ/808/106; Do et al.
2015ApJ...809..143D 2015ApJ...809..143D, Cat. J/ApJ/809/143) and 381 giants having an
effective temperature less than 5000K from the X-shooter Spectral
Library (R∼10000, the second data release; Gonneau et al.
2020A&A...634A.133G 2020A&A...634A.133G, Cat. J/A+A/634/A133) located in star clusters, in
the field, in the Galactic bulge, and in the Magellanic Clouds (we
refer to Gonneau et al. 2020A&A...634A.133G 2020A&A...634A.133G, Cat. J/A+A/634/A133 for
details). The details about the instruments, observations, and data
reduction can be found in Do et al. (2015ApJ...809..143D 2015ApJ...809..143D, Cat.
J/ApJ/809/143) and Stostad et al. (Stostad et al. 2015ApJ...808..106S 2015ApJ...808..106S,
Cat. J/ApJ/808/106) for NIFS, and Vernet et al. (2011A&A...536A.105V 2011A&A...536A.105V)
and Gonneau et al. (2020A&A...634A.133G 2020A&A...634A.133G, Cat. J/A+A/634/A133) for
X-shooter. We use SIMBAD to remove known supergiants, Mira variables,
and OH/IR stars of the X-shooter library from our study as they behave
differently than normal giants (Lancon & Wood 2000A&AS..146..217L 2000A&AS..146..217L,
Cat. J/A+AS/146/217; Ghosh et al. 2018AJ....155..216G 2018AJ....155..216G). The sample
size reduces to 240 stars. Among them, 33 stars are observed more than
once. Thus, our sample further reduces with 177 stars. We have
obtained spectra of a total 260 (177 X-shooter, 83 NIFS) cool giants
for this study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 109 260 Fundamental parameters and measured EWs of the
sample
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See also:
J/ApJ/808/106 : NIR spectroscopic obs. in the Galactic Center
(Stostad+, 2015)
J/ApJ/809/143 : K-band spectra of stars within central 1pc of the MW
(Do+, 2015)
J/A+A/634/A133 : X-Shooter Spectral Library (XSL). DR2 (Gonneau+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star name
27- 35 A9 --- Spectra Origin of the spectra (X-shooter or NIFS)
37- 40 I4 K Teff Effective temperature
42- 44 I3 K e_Teff Error on Teff
46- 51 F6.3 [-] [Fe/H] Fe/H abundance ratio
53- 57 F5.3 [-] e_[Fe/H] Error on [Fe/H]
59- 64 F6.3 0.1nm EWNaI Equivalent width of the NaI line
66- 70 F5.3 0.1nm e_EWNaI Error on EWNaI
72- 77 F6.3 0.1nm EWFeI Equivalent width of the FeI line
79- 83 F5.3 0.1nm e_EWFeI Error on EWFeI
85- 90 F6.3 0.1nm EWCO229 Equivalent width of the CO 2.29um line
92- 96 F5.3 0.1nm e_EWCO229 Error on EWCO229
98-103 F6.3 0.1nm EWCO232 Equivalent width of the CO 2.32um line
105-109 F5.3 0.1nm e_EWCO232 Error on EWCO232
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 19-Oct-2023