GALAH survey: chemically tagging the thick disk

Bland-Hawthorn, Joss; Sharma, Sanjib; Freeman, K. C.

doi:10.1051/eas/1567039

Cited by 7 publications

(9 citation statements)

References 14 publications

(13 reference statements)

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“…The top panel of Fig. 1 shows the previous calibration, the middle panel shows the new calibration and the bottom panel shows the 2 The GeTCal code and the T eff and [Fe/H] calibrations are available at http://www.astro.up.pt/exoearths/tools.html. [19].…”

Section: Getcalmentioning

confidence: 99%

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A new spectroscopic calibration to determineT_effand [Fe/H] of FGK dwarfs and giants

et al. 2017

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Abstract. We present a new spectroscopic calibration for a fast estimate of T eff and [Fe/H] for FGK dwarfs and GK giant stars. We used spectra from a joint sample of 708 stars, composed by 451 FGK dwarfs and 257 GK-giant stars with homogeneously determined spectroscopic stellar parameters. We have derived 322 EW line-ratios and 100 FeI lines that can be used to compute T eff and [Fe/H], respectively. We show that these calibrations are effective for FGK dwarfs and GK-giant stars in the following ranges: 4500 K < T eff < 6500 K, 2.5 < log g < 4.9 dex, and −0.8 < [Fe/H] < 0.5 dex. The new calibration has a standard deviation of 74 K for T eff and 0.07 dex for [Fe/H]. We use four independent samples of stars to test and verify the new calibration, a sample of giant stars, a sample composed of Gaia FGK benchmark stars, a sample of GK-giant stars from the DR1 of the Gaia-ESO survey, and a sample of FGK-dwarf stars. We present a new computer code, GeTCal, for automatically producing new calibration files based on any new sample of stars.

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Section: Getcalmentioning

confidence: 99%

“…The volume of data being produced by large-survey observational programs [2,4] requires the existence of quick methods to obtain stellar parameters for a diverse range of stellar spectral types.…”

Section: Introductionmentioning

confidence: 99%

A new spectroscopic calibration to determineT_effand [Fe/H] of FGK dwarfs and giants

et al. 2017

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“…Large-survey observational programs such as GES (Gilmore et al 2012), GALAH (Bland-Hawthorn et al 2014), and RAVE (Steinmetz et al 2006) are quickly becoming the new paradigm of stellar observations and characterization. Given the volume of data involved, the success of these programs relies on the existence of methods that rapidly ascertain stellar parameters for a diverse range of stellar spectral types.…”

Section: Introductionmentioning

confidence: 99%

NewT_effand [Fe/H] spectroscopic calibration for FGK dwarfs and GK giants

Teixeira

Sousa

Tsantaki

et al. 2016

A&A

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Context. The ever-growing number of large spectroscopic survey programs has increased the importance of fast and reliable methods with which to determine precise stellar parameters. Some of these methods are highly dependent on correct spectroscopic calibrations. Aims. The goal of this work is to obtain a new spectroscopic calibration for a fast estimate of T eff and [Fe/H] for a wide range of stellar spectral types. Methods. We used spectra from a joint sample of 708 stars, compiled from 451 FGK dwarfs and 257 GK-giant stars. We used homogeneously determined spectroscopic stellar parameters to derive temperature calibrations using a set of selected EW line-ratios, and [Fe/H] calibrations using a set of selected Fe i lines. Results. We have derived 322 EW line-ratios and 100 Fe i lines that can be used to compute T eff and [Fe/H], respectively. We show that these calibrations are effective for FGK dwarfs and GK-giant stars in the following ranges: 4500 K < T eff < 6500 K, 2.5 < log g < 4.9 dex, and −0.8 < [Fe/H] < 0.5 dex. The new calibration has a standard deviation of 74 K for T eff and 0.07 dex for [Fe/H]. We use four independent samples of stars to test and verify the new calibration, a sample of 56 giant stars, a sample composed of Gaia FGK benchmark stars, a sample of 36 GK-giant stars of the DR1 of the Gaia-ESO survey, and a sample of 582 FGK-dwarf stars. We also provide a new computer code, GeTCal, for automatically producing new calibration files based on any new sample of stars.

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“…This information is crucial as studies (e.g., Escala & Larson 2008;Kruijssen 2012) have shown that the maximum aggregate size that stars form might depend on the star formation rate and the gas mass in the past. Since most of the clusters are soon disrupted (Lada & Lada 2003), constraining the past cluster mass function through chemical tagging may be the best option (Bland-Hawthorn et al 2014;Ting et al 2015b).…”

Section: Introductionmentioning

confidence: 99%

Accelerated Fitting of Stellar Spectra

Ting

Conroy

Rix

2016

ApJ

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Stellar spectra are often modeled and fitted by interpolating within a rectilinear grid of synthetic spectra to derive the stars' labels: stellar parameters and elemental abundances. However, the number of synthetic spectra needed for a rectilinear grid grows exponentially with the label space dimensions, precluding the simultaneous and selfconsistent fitting of more than a few elemental abundances. Shortcuts such as fitting subsets of labels separately can introduce unknown systematics and do not produce correct error covariances in the derived labels. In this paper we present a new approach-Convex Hull Adaptive Tessellation (CHAT)-which includes several new ideas for inexpensively generating a sufficient stellar synthetic library, using linear algebra and the concept of an adaptive, data-driven grid. A convex hull approximates the region where the data lie in the label space. A variety of tests with mock data sets demonstrate that CHAT can reduce the number of required synthetic model calculations by three orders of magnitude in an eight-dimensional label space. The reduction will be even larger for higher dimensional label spaces. In CHAT the computational effort increases only linearly with the number of labels that are fit simultaneously. Around each of these grid points in the label space an approximate synthetic spectrum can be generated through linear expansion using a set of "gradient spectra" that represent flux derivatives at every wavelength point with respect to all labels. These techniques provide new opportunities to fit the full stellar spectra from large surveys with 15-30 labels simultaneously.

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GALAH survey: chemically tagging the thick disk

Cited by 7 publications

References 14 publications

A new spectroscopic calibration to determineT_effand [Fe/H] of FGK dwarfs and giants

A new spectroscopic calibration to determineT_effand [Fe/H] of FGK dwarfs and giants

NewT_effand [Fe/H] spectroscopic calibration for FGK dwarfs and GK giants

Accelerated Fitting of Stellar Spectra

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GALAH survey: chemically tagging the thick disk

Cited by 7 publications

References 14 publications

A new spectroscopic calibration to determineTeffand [Fe/H] of FGK dwarfs and giants

A new spectroscopic calibration to determineTeffand [Fe/H] of FGK dwarfs and giants

NewTeffand [Fe/H] spectroscopic calibration for FGK dwarfs and GK giants

Accelerated Fitting of Stellar Spectra

Contact Info

Product

Resources

About

A new spectroscopic calibration to determineT_effand [Fe/H] of FGK dwarfs and giants

A new spectroscopic calibration to determineT_effand [Fe/H] of FGK dwarfs and giants

NewT_effand [Fe/H] spectroscopic calibration for FGK dwarfs and GK giants