Chemical abundances in six nearby star-forming regions

Santos, N. C.; Melo, C.; James, D. J.; Gameiro, J. F.; Bouvier, J.; Gomes, Jorge

doi:10.1051/0004-6361:20079083

Cited by 71 publications

(107 citation statements)

References 53 publications

(71 reference statements)

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“…This also agrees with existing studies of metallicity in other nearby star-formation regions (Padgett 1996;Santos et al 2008;D'Orazi et al 2009a;Biazzo et al 2011). Many stars in the stellar sample considered here are however not cluster members, and are therefore of unknown metallicity.…”

Section: Introductionsupporting

confidence: 91%

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Damiani

Prisinzano

Micela

et al. 2014

A&A

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We present a study of spectral diagnostics available from optical spectra with R = 17 000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the γ Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the Hα line core and wings, and temperature-and gravity-sensitive sets of lines, each useful as a T eff or log g indicator over a limited range of stellar spectral types. Hα line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global T eff -and log g-sensitive indices τ and γ, valid for the entire range of types in the observed sample. We find a clear difference between gravity indices of main-sequence and premain-sequence stars, as well as a much larger difference between these and giant stars. The potentially great usefulness of the (γ, τ) diagram as a distance-independent age measurement tool for young clusters is discussed. We discuss the effect on the defined indices of classical T Tauri star veiling, which is however detected in only a few stars in the present sample. Then, we present tests and calibrations of these indices, on the basis of both photometry and literature reference spectra, from the UVES Paranal Observatory Project and the ELODIE 3.1 Library. The known properties of these stars, spanning a wide range of stellar parameters, enable us to obtain a good understanding of the performances of our new spectral indices. For non-peculiar stars with known temperature, gravity, and metallicity, we are able to calibrate quantitatively our indices, and derive stellar parameters for a wide range of stellar types. To this aim, a new composite index is defined, providing a good metallicity indicator. The ability of our indices to select peculiar, or otherwise rare classes of stars is also established. For pre-main-sequence stars outside the parameter range of the ELODIE dataset, index calibration relies on model isochrones. We check our calibrations against current Gaia-ESO UVES results, plus a number of Survey benchmark stars, and also against Gaia-ESO observations of young clusters, which contribute to establishing the good performance of our method across a wide range of stellar parameters. Our gravity determination for late-type PMS stars is found to be accurate enough to let us obtain gravity-based age estimates for PMS clusters. Finally, our gravity determinations support the existence of an older premain-sequence population in the γ Vel sky region, in agreement with evidence obtained from the lithium depletion pattern of the same stars.

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Section: Introductionsupporting

confidence: 91%

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Damiani

Prisinzano

Micela

et al. 2014

A&A

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“…Indeed, recent determination of photospheric [Fe/H] for young stars in Taurus are compatible with solar abundance (Santos et al 2008;D'Orazi et al 2011). Lower [Fe/H] ratios ( 0.2 solar) have been derived in X-rays tracing coronal material but in these observations the [Fe/O] abundance ratio is 0.4−0.8 solar (Scelsi et al 2007;Günther et al 2007).…”

Section: Implications For Jet Launching Modelsmentioning

confidence: 84%

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

Agra-Amboage

Dougados

Cabrit

et al. 2011

A&A

111

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Context. The origin of protostellar jets as well as their impact on the regulation of angular momentum and the inner disk physics are still crucial open questions in star formation. Aims. We aim to test the different proposed ejection processes in T Tauri stars through high-angular resolution observations of forbidden-line emission from the inner DG Tauri microjet. Methods. We present spectro-imaging observations of the DG Tauri jet obtained with SINFONI/VLT in the lines of [Fe ii]λ1.64 μm, 1.53 μm with 0. 15 angular resolution and R = 3000 spectral resolution. We analyze the morphology and kinematics, derive electronic densities and mass-flux rates and discuss the implications for proposed jet launching models. Results. (1) We observe an onion-like velocity structure in [Fe ii] in the blueshifted jet, similar to that observed in optical lines. Highvelocity (HV) gas at -200 km s −1 is collimated inside a half-opening angle of 4 • and medium-velocity (MV) gas at -100 km s −1 in a cone with an half-opening angle 14.• (2) Two new axial jet knots are detected in the blue jet, as well as a more distant bubble with corresponding counter-bubble. The periodic knot ejection timescale is revised downward to 2.5 yrs. (3) The redshifted jet is detected only beyond 0. 7 from the star, yielding revised constraints on the disk surface density. (4) From comparison to [O i] data we infer iron depletion of a factor 3 at high velocities and a factor 10 at speeds below -100 km s −1 . (5) The mass-fluxes in each of the medium and high-velocity components of the blueshifted lobe are 1.6 ± 0.8 × 10 −8 M yr −1 , representing 0.02−0.2 of the disk accretion rate. Conclusions. The medium-velocity conical [Fe ii] flow in the DG Tau jet is too fast and too narrow to trace photo-evaporated matter from the disk atmosphere. Both its kinematics and collimation cannot be reproduced by the X-wind, nor can the "conical magnetospheric wind". The level of Fe gas phase depletion in the DG Tau medium-velocity component also rules out a stellar wind and a cocoon ejected sideways from the high-velocity beam. A quasi-steady centrifugal MHD disk wind ejected over 0.25−1.5 AU and/or episodic magnetic tower cavities launched from the disk appear as the most plausible origins for the [Fe ii] medium velocity component in the DG Tau jet. The same disk wind model can also account for the properties of the high-velocity [Fe ii] flow, although alternative origins in magnetospheric and/or stellar winds cannot be excluded for this component.

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“…It has been proposed that metal-rich stars found in the solar vicinity may have been formed in the inner Galactic disk regions(e.g. Grenon 1999;Ecuvillon et al 2007;Famaey et al 2007;Santos et al 2008;Schönrich & Binney 2009b). Nevertheless, the origin and nature of these stars remains unclear and needs to be clarified.…”

Section: Discussionmentioning

confidence: 99%

A newα-enhanced super-solar metallicity population

Adibekyan¹,

Santos²,

Sousa³

et al. 2011

A&A

Self Cite

154

214

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We performed a uniform and detailed analysis of 1112 high-resolution spectra of FGK dwarfs obtained with the HARPS spectrograph at the ESO 3.6 m telescope (La Silla, Chile). Most stars have effective temperatures 4700 K ≤ T eff ≤ 6300 K and lie in the metallicity range of −1.39 ≤ [Fe/H] ≤ 0.55. Our main goal is to investigate whether there are any differences between the elemental abundance trends (especially [α/Fe] ratio) for stars of different subpopulations. The equivalent widths of spectral lines are automatically measured from HARPS spectra with the ARES code. The abundances of three α elements are determined using a differential LTE analysis relative to the Sun, with the 2010 revised version of the spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. The stars of our sample fall into two populations, clearly separated in terms of The metal-poor high-α stars (thick disk) and metal-rich high-α stars are on average older than chemically defined thin disk stars (low-α stars). The two α-enhanced families have different kinematics and orbital parameters. The metal-rich α-enhanced stars, such as thin disk stars have nearly circular orbits, close to the Galactic plane. We put forward the idea that these stars may have been formed in the inner Galactic disk, but their exact nature still remains to be clarified.

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Chemical abundances in six nearby star-forming regions

Cited by 71 publications

References 53 publications

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Sub-arcsecond [Fe ii] spectro-imaging of the DG Tauri jet

A newα-enhanced super-solar metallicity population

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