| 1. |
- de Jong, R. S., et al.
(författare)
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4MOST : Project overview and information for the First Call for Proposals
- 2019
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Ingår i: The Messenger. - : European Southern Observatory. - 0722-6691. ; 175, s. 3-11
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs (R = λ/Δλ ~ 6500), and 812 fibres transferring light to the high-resolution spectrograph (R ~ 20 000). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.
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| 2. |
- Garcia-Benito, R., et al.
(författare)
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CALIFA, the Calar Alto Legacy Integral Field Area survey III. Second public data release
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 576:A135
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the Second Public Data Release (DR2) of the Calar Alto Legacy Integral Field Area (CALIFA) survey. The data for 200 objects are made public, including the 100 galaxies of the First Public Data Release (DR1). Data were obtained with the integral-field spectrograph PMAS /PPak mounted on the 3.5 m telescope at the Calar Alto observatory. Two different spectral setups are available for each galaxy, (i) a low-resolution V500 setup covering the wavelength range 3745-7500 angstrom with a spectral resolution of 6.0 angstrom (FWHM); and (ii) a medium-resolution V1200 setup covering the wavelength range 3650-4840 angstrom with a spectral resolution of 2.3 angstrom (FWHM). The sample covers a redshift range between 0.005 and 0.03, with a wide range of properties in the color-magnitude diagram, stellar mass, ionization conditions, and morphological types. All the cubes in the data release were reduced with the latest pipeline, which includes improved spectrophotometric calibration, spatial registration, and spatial resolution. The spectrophotometric calibration is better than 6% and the median spatial resolution is 2 4. In total, the second data release contains over 1.5 million spectra.
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| 3. |
- Martell, S. L., et al.
(författare)
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The GALAH survey : observational overview and Gaia DR1 companion
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 465:3, s. 3203-3219
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Tidskriftsartikel (refereegranskat)abstract
- The Galactic Archaeology with HERMES (GALAH) survey is amassive observational project to trace the MilkyWay's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R similar or equal to 28 000) spectra, taken with the High Efficiency and Resolution Multi- Element Spectrograph (HERMES) instrument at the Anglo-Australian Telescope, GALAH will determine stellar parameters and abundances of up to 29 elements for up to one million stars. Selecting targets from a colour-unbiased catalogue built from 2MASS, APASS and UCAC4 data, we expect to observe dwarfs at 0.3-3 kpc and giants at 1-10 kpc. This enables a thorough local chemical inventory of the Galactic thin and thick discs, and also captures smaller samples of the bulge and halo. In this paper, we present the plan, process and progress as of early 2016 for GALAH survey observations. In our first two years of survey observing we have accumulated the largest high-quality spectroscopic data set at this resolution, over 200 000 stars. We also present the first public GALAH data catalogue: stellar parameters (T-eff, log(g), [ Fe/ H], [ alpha/ Fe]), radial velocity, distance modulus and reddening for 10 680 observations of 9860 Tycho-2 stars, 7894 of which are included in the first Gaia data release.
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| 4. |
- Martell, S., et al.
(författare)
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The GALAH survey : Scientific motivation
- 2015
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 449:3
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Tidskriftsartikel (refereegranskat)abstract
- The Galactic Archaeology with HERMES (GALAH) survey is a large high-resolution spectroscopic survey using the newly commissioned High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. The HERMES spectrograph provides high-resolution (R ~ 28 000) spectra in four passbands for 392 stars simultaneously over a 2 deg field of view. The goal of the survey is to unravel the formation and evolutionary history of the Milky Way, using fossil remnants of ancient star formation events which have been disrupted and are now dispersed throughout the Galaxy. Chemical tagging seeks to identify such dispersed remnants solely from their common and unique chemical signatures; these groups are unidentifiable from their spatial, photometric or kinematic properties. To carry out chemical tagging, the GALAH survey will acquire spectra for a million stars down to V ~ 14. The HERMES spectra of FGK stars contain absorption lines from 29 elements including light proton-capture elements, α-elements, odd-Z elements, iron-peak elements and n-capture elements from the light and heavy s-process and the r-process. This paper describes the motivation and planned execution of the GALAH survey, and presents some results on the first-light performance of HERMES.
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| 5. |
- Miglio, A., et al.
(författare)
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PLATO as it is : A legacy mission for Galactic archaeology
- 2017
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Ingår i: Astronomical Notes - Astronomische Nachrichten. - : WILEY-V C H VERLAG GMBH. - 0004-6337 .- 1521-3994. ; 338:6, s. 644-661
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Tidskriftsartikel (refereegranskat)abstract
- Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but it will only enable a blurred view on the temporal sequence that led to the present-day Galaxy. As demonstrated by the (ongoing) exploitation of data from the pioneering photometric missions CoRoT, Kepler, and K2, asteroseismology provides the way forward: solar-like oscillating giants are excellent evolutionary clocks thanks to the availability of seismic constraints on their mass and to the tight age-initial mass relation they adhere to. In this paper we identify five key outstanding questions relating to the formation and evolution of the Milky Way that will need precise and accurate ages for large samples of stars to be addressed, and we identify the requirements in terms of number of targets and the precision on the stellar properties that are needed to tackle such questions. By quantifying the asteroseismic yields expected from PLATO for red giant stars, we demonstrate that these requirements are within the capabilities of the current instrument design, provided that observations are sufficiently long to identify the evolutionary state and allow robust and precise determination of acoustic-mode frequencies. This will allow us to harvest data of sufficient quality to reach a 10% precision in age. This is a fundamental prerequisite to then reach the more ambitious goal of a similar level of accuracy, which will be possible only if we have at hand a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics, a goal that conveniently falls within the main aims of PLATO's core science. We therefore strongly endorse PLATO's current design and proposed observational strategy, and conclude that PLATO, as it is, will be a legacy mission for Galactic archaeology.
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| 6. |
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| 7. |
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| 8. |
- Buder, S., et al.
(författare)
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The GALAH survey : An abundance, age, and kinematic inventory of the solar neighbourhood made with TGAS
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 624
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Tidskriftsartikel (refereegranskat)abstract
- The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey and Gaia provides a high-dimensional chemodynamical space of unprecedented size. We present a first analysis of a subset of this overlap, of 7066 dwarf, turn-off, and subgiant stars. These stars have spectra from the GALAH survey and high parallax precision from the Gaia DR1 Tycho-Gaia Astrometric Solution. We investigate correlations between chemical compositions, ages, and kinematics for this sample. Stellar parameters and elemental abundances are derived from the GALAH spectra with the spectral synthesis code SPECTROSCOPY MADE EASY. We determine kinematics and dynamics, including action angles, from the Gaia astrometry and GALAH radial velocities. Stellar masses and ages are determined with Bayesian isochrone matching, using our derived stellar parameters and absolute magnitudes. We report measurements of Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, as well as Ba and we note that we have employed non-LTE calculations for Li, O, Al, and Fe. We show that the use of astrometric and photometric data improves the accuracy of the derived spectroscopic parameters, especially log g. Focusing our investigation on the correlations between stellar age, iron abundance [Fe/H], and mean alpha-enhancement [alpha/Fe] of the magnitude-selected sample, we recover the result that stars of the high-a sequence are typically older than stars in the low-a sequence, the latter spanning iron abundances of -0.7 < [Fe/H] < +0.5. While these two sequences become indistinguishable in [alpha/Fe] vs. [Fe/H] at the metal-rich regime, we find that age can be used to separate stars from the extended high-a and the low-a sequence even in this regime. When dissecting the sample by stellar age, we find that the old stars (>8 Gyr) have lower angular momenta L-z than the Sun, which implies that they are on eccentric orbits and originate from the inner disc. Contrary to some previous smaller scale studies we find a continuous evolution in the high-alpha-sequence up to super-solar [Fe/H] rather than a gap, which has been interpreted as a separate "high-alpha metal-rich" population. Stars in our sample that are younger than 10 Gyr, are mainly found on the low alpha-sequence and show a gradient in L-z from low [Fe/H] > (L-z > L-z,L-circle dot) towards higher [Fe/H] (L-z < L-z,L-circle dot), which implies that the stars at the ends of this sequence are likely not originating from the close solar vicinity.
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| 9. |
- Duong, L., et al.
(författare)
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The GALAH survey : properties of the Galactic disc(s) in the solar neighbourhood
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 476:4, s. 5216-5232
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Tidskriftsartikel (refereegranskat)abstract
- Using data from the GALAH pilot survey, we determine properties of the Galactic thin and thick discs near the solar neighbourhood. The data cover a small range of Galactocentric radius (7.9 less than or similar to R-GC less than or similar to 9.5 kpc), but extend up to 4 kpc in height from the Galactic plane, and several kpc in the direction of Galactic anti-rotation (at longitude 260 degrees <= l <= 280 degrees). This allows us to reliably measure the vertical density and abundance profiles of the chemically and kinematically defined 'thick' and 'thin' discs of the Galaxy. The thin disc (low-alpha population) exhibits a steep negative vertical metallicity gradient, at d[M/H]/dz = -0.18 +/- 0.01 dex kpc(-1), which is broadly consistent with previous studies. In contrast, its vertical alpha-abundance profile is almost flat, with a gradient of d[alpha/M]/dz = 0.008 +/- 0.002 dex kpc(-1). The steep vertical metallicity gradient of the low-a population is in agreement with models where radial migration has a major role in the evolution of the thin disc. The thick disc (high-alpha population) has a weaker vertical metallicity gradient d[M/H]/dz = -0.058 +/- 0.003 dex kpc(-1). The aabundance of the thick disc is nearly constant with height, d[alpha/M]/dz = 0.007 +/- 0.002 dex kpc(-1). The negative gradient in metallicity and the small gradient in [alpha/M] indicate that the high-alpha population experienced a settling phase, but also formed prior to the onset of major Type I alpha supernova enrichment. We explore the implications of the distinct alpha-enrichments and narrow [alpha/M] range of the sub-populations in the context of thick disc formation.
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| 10. |
- Spina, L., et al.
(författare)
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The GALAH survey : tracing the Galactic disc with open clusters
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 503:3, s. 3279-3296
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Tidskriftsartikel (refereegranskat)abstract
- Open clusters are unique tracers of the history of our own Galaxy's disc. According to our membership analysis based on Gala astrometry, out of the 226 potential clusters falling in the footprint of the GALactic Archaeology with HERMES (GALAH) survey or the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey, we find that 205 have secure members that were observed by at least one of the surveys. Furthermore, members of 134 clusters have high-quality spectroscopic data that we use to determine their chemical composition. We leverage this information to study the chemical distribution throughout the Galactic disc of 21 elements, from C to Eu. The radial metallicity gradient obtained from our analysis is -0.076 +/- 0.009 dex kpc(-1), which is in agreement with previous works based on smaller samples. Furthermore, the gradient in the (Fe/Hi-guiding radius (r(guid)) plane is -0.073 +/- 0.008 dex kpc(-1). We show consistently that open clusters trace the distribution of chemical elements throughout the Galactic disc differently than field stars. In particular, at the given radius, open clusters show an age-metallicity relation that has less scatter than field stars. As such scatter is often interpreted as an effect of radial migration, we suggest that these differences are due to the physical selection effect imposed by our Galaxy: clusters that would have migrated significantly also had higher chances to get destroyed. Finally, our results reveal trends in the [X/Fe]-r(guid)-age space, which are important to understand production rates of different elements as a function of space and time.
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