Low speed maneuvering flight of the rose-breasted cockatoo (Eolophus roseicapillus). II. Inertial and aerodynamic reorientation.

PubMed

Hedrick, T L; Usherwood, J R; Biewener, A A

2007-06-01

The reconfigurable, flapping wings of birds allow for both inertial and aerodynamic modes of reorientation. We found evidence that both these modes play important roles in the low speed turning flight of the rose-breasted cockatoo Eolophus roseicapillus. Using three-dimensional kinematics recorded from six cockatoos making a 90 degrees turn in a flight corridor, we developed predictions of inertial and aerodynamic reorientation from estimates of wing moments of inertia and flapping arcs, and a blade-element aerodynamic model. The blade-element model successfully predicted weight support (predicted was 88+/-17% of observed, N=6) and centripetal force (predicted was 79+/-29% of observed, N=6) for the maneuvering cockatoos and provided a reasonable estimate of mechanical power. The estimated torque from the model was a significant predictor of roll acceleration (r(2)=0.55, P<0.00001), but greatly overestimated roll magnitude when applied with no roll damping. Non-dimensional roll damping coefficients of approximately -1.5, 2-6 times greater than those typical of airplane flight dynamics (approximately -0.45), were required to bring our estimates of reorientation due to aerodynamic torque back into conjunction with the measured changes in orientation. Our estimates of inertial reorientation were statistically significant predictors of the measured reorientation within wingbeats (r(2) from 0.2 to 0.37, P<0.0005). Components of both our inertial reorientation and aerodynamic torque estimates correlated, significantly, with asymmetries in the activation profile of four flight muscles: the pectoralis, supracoracoideus, biceps brachii and extensor metacarpi radialis (r(2) from 0.27 to 0.45, P<0.005). Thus, avian flight maneuvers rely on production of asymmetries throughout the flight apparatus rather than in a specific set of control or turning muscles.

The GALAH Survey: Second Data Release

NASA Astrophysics Data System (ADS)

Buder, Sven; Asplund, Martin; Duong, Ly; Kos, Janez; Lind, Karin; Ness, Melissa K.; Sharma, Sanjib; Bland-Hawthorn, Joss; Casey, Andrew R.; De Silva, Gayandhi M.; D'Orazi, Valentina; Freeman, Ken C.; Lewis, Geraint F.; Lin, Jane; Martell, Sarah L.; Schlesinger, Katharine J.; Simpson, Jeffrey D.; Zucker, Daniel B.; Zwitter, Tomaž; Amarsi, Anish M.; Anguiano, Borja; Carollo, Daniela; Casagrande, Luca; Čotar, Klemen; Cottrell, Peter L.; Da Costa, Gary; Gao, Xudong D.; Hayden, Michael R.; Horner, Jonathan; Ireland, Michael J.; Kafle, Prajwal R.; Munari, Ulisse; Nataf, David M.; Nordlander, Thomas; Stello, Dennis; Ting, Yuan-Sen; Traven, Gregor; Watson, Fred; Wittenmyer, Robert A.; Wyse, Rosemary F. G.; Yong, David; Zinn, Joel C.; Žerjal, Maruša

2018-05-01

The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342,682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multi-step approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (Teff, log g, [Fe/H], [X/Fe], vmic, vsin i, A_{K_S}) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D MARCS stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.

The GALAH survey: scientific motivation

NASA Astrophysics Data System (ADS)

De Silva, G. M.; Freeman, K. C.; Bland-Hawthorn, J.; Martell, S.; de Boer, E. Wylie; Asplund, M.; Keller, S.; Sharma, S.; Zucker, D. B.; Zwitter, T.; Anguiano, B.; Bacigalupo, C.; Bayliss, D.; Beavis, M. A.; Bergemann, M.; Campbell, S.; Cannon, R.; Carollo, D.; Casagrande, L.; Casey, A. R.; Da Costa, G.; D'Orazi, V.; Dotter, A.; Duong, L.; Heger, A.; Ireland, M. J.; Kafle, P. R.; Kos, J.; Lattanzio, J.; Lewis, G. F.; Lin, J.; Lind, K.; Munari, U.; Nataf, D. M.; O'Toole, S.; Parker, Q.; Reid, W.; Schlesinger, K. J.; Sheinis, A.; Simpson, J. D.; Stello, D.; Ting, Y.-S.; Traven, G.; Watson, F.; Wittenmyer, R.; Yong, D.; Žerjal, M.

2015-05-01

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.

The GALAH survey: observational overview and Gaia DR1 companion

NASA Astrophysics Data System (ADS)

Martell, S. L.; Sharma, S.; Buder, S.; Duong, L.; Schlesinger, K. J.; Simpson, J.; Lind, K.; Ness, M.; Marshall, J. P.; Asplund, M.; Bland-Hawthorn, J.; Casey, A. R.; De Silva, G.; Freeman, K. C.; Kos, J.; Lin, J.; Zucker, D. B.; Zwitter, T.; Anguiano, B.; Bacigalupo, C.; Carollo, D.; Casagrande, L.; Da Costa, G. S.; Horner, J.; Huber, D.; Hyde, E. A.; Kafle, P. R.; Lewis, G. F.; Nataf, D.; Navin, C. A.; Stello, D.; Tinney, C. G.; Watson, F. G.; Wittenmyer, R.

2017-03-01

The Galactic Archaeology with HERMES (GALAH) survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R ≃ 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 (Teff, log(g), [Fe/H], [α/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.

The evolutionary history of cockatoos (Aves: Psittaciformes: Cacatuidae).

PubMed

White, Nicole E; Phillips, Matthew J; Gilbert, M Thomas P; Alfaro-Núñez, Alonzo; Willerslev, Eske; Mawson, Peter R; Spencer, Peter B S; Bunce, Michael

2011-06-01

Cockatoos are the distinctive family Cacatuidae, a major lineage of the order of parrots (Psittaciformes) and distributed throughout the Australasian region of the world. However, the evolutionary history of cockatoos is not well understood. We investigated the phylogeny of cockatoos based on three mitochondrial and three nuclear DNA genes obtained from 16 of 21 species of Cacatuidae. In addition, five novel mitochondrial genomes were used to estimate time of divergence and our estimates indicate Cacatuidae diverged from Psittacidae approximately 40.7 million years ago (95% CI 51.6-30.3 Ma) during the Eocene. Our data shows Cacatuidae began to diversify approximately 27.9 Ma (95% CI 38.1-18.3 Ma) during the Oligocene. The early to middle Miocene (20-10 Ma) was a significant period in the evolution of modern Australian environments and vegetation, in which a transformation from mainly mesic to xeric habitats (e.g., fire-adapted sclerophyll vegetation and grasslands) occurred. We hypothesize that this environmental transformation was a driving force behind the diversification of cockatoos. A detailed multi-locus molecular phylogeny enabled us to resolve the phylogenetic placements of the Palm Cockatoo (Probosciger aterrimus), Galah (Eolophus roseicapillus), Gang-gang Cockatoo (Callocephalon fimbriatum) and Cockatiel (Nymphicus hollandicus), which have historically been difficult to place within Cacatuidae. When the molecular evidence is analysed in concert with morphology, it is clear that many of the cockatoo species' diagnostic phenotypic traits such as plumage colour, body size, wing shape and bill morphology have evolved in parallel or convergently across lineages. Copyright © 2011 Elsevier Inc. All rights reserved.

Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds?

PubMed Central

Steiger, Silke S; Fidler, Andrew E; Valcu, Mihai; Kempenaers, Bart

2008-01-01

Among vertebrates, the sense of smell is mediated by olfactory receptors (ORs) expressed in sensory neurons within the olfactory epithelium. Comparative genomic studies suggest that the olfactory acuity of mammalian species correlates positively with both the total number and the proportion of functional OR genes encoded in their genomes. In contrast to mammals, avian olfaction is poorly understood, with birds widely regarded as relying primarily on visual and auditory inputs. Here, we show that in nine bird species from seven orders (blue tit, Cyanistes caeruleus; black coucal, Centropus grillii; brown kiwi, Apteryx australis; canary, Serinus canaria; galah, Eolophus roseicapillus; red jungle fowl, Gallus gallus; kakapo, Strigops habroptilus; mallard, Anas platyrhynchos; snow petrel, Pagodroma nivea), the majority of amplified OR sequences are predicted to be from potentially functional genes. This finding is somewhat surprising as one previous report suggested that the majority of OR genes in an avian (red jungle fowl) genomic sequence are non-functional pseudogenes. We also show that it is not the estimated proportion of potentially functional OR genes, but rather the estimated total number of OR genes that correlates positively with relative olfactory bulb size, an anatomical correlate of olfactory capability. We further demonstrate that all the nine bird genomes examined encode OR genes belonging to a large gene clade, termed γ-c, the expansion of which appears to be a shared characteristic of class Aves. In summary, our findings suggest that olfaction in birds may be a more important sense than generally believed. PMID:18628122

The GALAH Survey and Galactic Archaeology in the Next Decade

NASA Astrophysics Data System (ADS)

Martell, S. L.

2016-10-01

The field of Galactic Archaeology aims to understand the origins and evolution of the stellar populations in the Milky Way, as a way to understand galaxy formation and evolution in general. The GALAH (Galactic Archaeology with HERMES) Survey is an ambitious Australian-led project to explore the Galactic history of star formation, chemical evolution, minor mergers and stellar migration. GALAH is using the HERMES spectrograph, a novel, highly multiplexed, four-channel high-resolution optical spectrograph, to collect high-quality R˜28,000 spectra for one million stars in the Milky Way. From these data we will determine stellar parameters, radial velocities and abundances for up to 29 elements per star, and carry out a thorough chemical tagging study of the nearby Galaxy. There are clear complementarities between GALAH and other ongoing and planned Galactic Archaeology surveys, and also with ancillary stellar data collected by major cosmological surveys. Combined, these data sets will provide a revolutionary view of the structure and history of the Milky Way.

Patterned-string tasks: relation between fine motor skills and visual-spatial abilities in parrots.

PubMed

Krasheninnikova, Anastasia

2013-01-01

String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla) and the cockatiel (Nymphicus hollandicus), forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.

The Galah Survey: Classification and Diagnostics with t-SNE Reduction of Spectral Information

NASA Astrophysics Data System (ADS)

Traven, G.; Matijevič, G.; Zwitter, T.; Žerjal, M.; Kos, J.; Asplund, M.; Bland-Hawthorn, J.; Casey, A. R.; De Silva, G.; Freeman, K.; Lin, J.; Martell, S. L.; Schlesinger, K. J.; Sharma, S.; Simpson, J. D.; Zucker, D. B.; Anguiano, B.; Da Costa, G.; Duong, L.; Horner, J.; Hyde, E. A.; Kafle, P. R.; Munari, U.; Nataf, D.; Navin, C. A.; Reid, W.; Ting, Y.-S.

2017-02-01

Galah is an ongoing high-resolution spectroscopic survey with the goal of disentangling the formation history of the Milky Way using the fossil remnants of disrupted star formation sites that are now dispersed around the Galaxy. It is targeting a randomly selected magnitude-limited (V ≤ 14) sample of stars, with the goal of observing one million objects. To date, 300,000 spectra have been obtained. Not all of them are correctly processed by parameter estimation pipelines, and we need to know about them. We present a semi-automated classification scheme that identifies different types of peculiar spectral morphologies in an effort to discover and flag potentially problematic spectra and thus help to preserve the integrity of the survey results. To this end, we employ the recently developed dimensionality reduction technique t-SNE (t-distributed stochastic neighbor embedding), which enables us to represent the complex spectral morphology in a two-dimensional projection map while still preserving the properties of the local neighborhoods of spectra. We find that the majority (178,483) of the 209,533 Galah spectra considered in this study represents normal single stars, whereas 31,050 peculiar and problematic spectra with very diverse spectral features pertaining to 28,579 stars are distributed into 10 classification categories: hot stars, cool metal-poor giants, molecular absorption bands, binary stars, Hα/Hβ emission, Hα/Hβ emission superimposed on absorption, Hα/Hβ P-Cygni, Hα/Hβ inverted P-Cygni, lithium absorption, and problematic. Classified spectra with supplementary information are presented in the catalog, indicating candidates for follow-up observations and population studies of the short-lived phases of stellar evolution.

The GALAH survey: chemical tagging of star clusters and new members in the Pleiades

NASA Astrophysics Data System (ADS)

Kos, Janez; Bland-Hawthorn, Joss; Freeman, Ken; Buder, Sven; Traven, Gregor; De Silva, Gayandhi M.; Sharma, Sanjib; Asplund, Martin; Duong, Ly; Lin, Jane; Lind, Karin; Martell, Sarah; Simpson, Jeffrey D.; Stello, Dennis; Zucker, Daniel B.; Zwitter, Tomaž; Anguiano, Borja; Da Costa, Gary; D'Orazi, Valentina; Horner, Jonathan; Kafle, Prajwal R.; Lewis, Geraint; Munari, Ulisse; Nataf, David M.; Ness, Melissa; Reid, Warren; Schlesinger, Katie; Ting, Yuan-Sen; Wyse, Rosemary

2018-02-01

The technique of chemical tagging uses the elemental abundances of stellar atmospheres to 'reconstruct' chemically homogeneous star clusters that have long since dispersed. The GALAH spectroscopic survey - which aims to observe one million stars using the Anglo-Australian Telescope - allows us to measure up to 30 elements or dimensions in the stellar chemical abundance space, many of which are not independent. How to find clustering reliably in a noisy high-dimensional space is a difficult problem that remains largely unsolved. Here, we explore t-distributed stochastic neighbour embedding (t-SNE) - which identifies an optimal mapping of a high-dimensional space into fewer dimensions - whilst conserving the original clustering information. Typically, the projection is made to a 2D space to aid recognition of clusters by eye. We show that this method is a reliable tool for chemical tagging because it can: (i) resolve clustering in chemical space alone, (ii) recover known open and globular clusters with high efficiency and low contamination, and (iii) relate field stars to known clusters. t-SNE also provides a useful visualization of a high-dimensional space. We demonstrate the method on a data set of 13 abundances measured in the spectra of 187 000 stars by the GALAH survey. We recover seven of the nine observed clusters (six globular and three open clusters) in chemical space with minimal contamination from field stars and low numbers of outliers. With chemical tagging, we also identify two Pleiades supercluster members (which we confirm kinematically), one as far as 6° - one tidal radius away from the cluster centre.

The Galah Survey: Classification and Diagnostics with t-SNE Reduction of Spectral Information

DOE Office of Scientific and Technical Information (OSTI.GOV)

Traven, G.; Zwitter, T.; Žerjal, M.

Galah is an ongoing high-resolution spectroscopic survey with the goal of disentangling the formation history of the Milky Way using the fossil remnants of disrupted star formation sites that are now dispersed around the Galaxy. It is targeting a randomly selected magnitude-limited ( V ≤ 14) sample of stars, with the goal of observing one million objects. To date, 300,000 spectra have been obtained. Not all of them are correctly processed by parameter estimation pipelines, and we need to know about them. We present a semi-automated classification scheme that identifies different types of peculiar spectral morphologies in an effort tomore » discover and flag potentially problematic spectra and thus help to preserve the integrity of the survey results. To this end, we employ the recently developed dimensionality reduction technique t-SNE ( t -distributed stochastic neighbor embedding), which enables us to represent the complex spectral morphology in a two-dimensional projection map while still preserving the properties of the local neighborhoods of spectra. We find that the majority (178,483) of the 209,533 Galah spectra considered in this study represents normal single stars, whereas 31,050 peculiar and problematic spectra with very diverse spectral features pertaining to 28,579 stars are distributed into 10 classification categories: hot stars, cool metal-poor giants, molecular absorption bands, binary stars, H α /H β emission, H α /H β emission superimposed on absorption, H α /H β P-Cygni, H α /H β inverted P-Cygni, lithium absorption, and problematic. Classified spectra with supplementary information are presented in the catalog, indicating candidates for follow-up observations and population studies of the short-lived phases of stellar evolution.« less

VizieR Online Data Catalog: GALAH semi-automated classification scheme (Traven+, 2017)

NASA Astrophysics Data System (ADS)

Traven, G.; Matijevic, G.; Zwitter, T.; Zerjal, M.; Kos, J.; Asplund, M.; Bland-Hawthorn, J.; Casey, A. R.; de Silva, G.; Freeman, K.; Lin, J.; Martell, S. L.; Schlesinger, K. J.; Sharma, S.; Simpson, J. D.; Zucker, D. B.; Anguiano, B.; da Costa, G.; Duong, L.; Horner, J.; Hyde, E. A.; Kafle, P. R.; Munari, U.; Nataf, D.; Navin, C. A.; Reid, W.; Ting, Y.-S.

2017-04-01

The GALactic Archaeology with HERMES (GALAH) survey was the main driver for the construction of Hermes (High Efficiency and Resolution Multi-Element Spectrograph), a fiber-fed multi-object spectrograph on the 3.9m Anglo-Australian Telescope. Its spectral resolving power (R) is about 28000, and there is also an R=45000 mode using a slit mask. Hermes has four simultaneous non-contiguous spectral arms centered at 4800, 5761, 6610, and 7740Å, covering about 1000Å in total, including Hα and Hβ lines. About 300000 spectra have been taken to date, including various calibration exposures. However, we concentrate on ~210000 spectra recorded before 2016 January 30. We devise a custom classification procedure which is based on two independently developed methods, the novel dimensionality reduction technique t-SNE (t-distributed stochastic neighbor embedding; van der Maaten & Hinton 2008, Journal of Machine Learning Research 9, 2579) and the renowned clustering algorithm DBSCAN (Ester+ 1996, Proc. 2nd Int. Conf. on KDD, 226 ed. E. Simoudis, J. Han, and U. Fayyad). (4 data files).

The GALAH Survey: Stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere and metallicity

NASA Astrophysics Data System (ADS)

Quillen, Alice C.; De Silva, Gayandhi; Sharma, Sanjib; Hayden, Michael; Freeman, Ken; Bland-Hawthorn, Joss; Žerjal, Maruša; Asplund, Martin; Buder, Sven; D'Orazi, Valentina; Duong, Ly; Kos, Janez; Lin, Jane; Lind, Karin; Martell, Sarah; Schlesinger, Katharine; Simpson, Jeffrey D.; Zucker, Daniel B.; Zwitter, Tomaz; Anguiano, Borja; Carollo, Daniela; Casagrande, Luca; Cotar, Klemen; Cottrell, Peter L.; Ireland, Michael; Kafle, Prajwal R.; Horner, Jonathan; Lewis, Geraint F.; Nataf, David M.; Ting, Yuan-Sen; Watson, Fred; Wittenmyer, Rob; Wyse, Rosemary

2018-04-01

Using GALAH survey data of nearby stars, we look at how structure in the planar (u, v) velocity distribution depends on metallicity and on viewing direction within the Galaxy. In nearby stars with distance d ≲ 1 kpc, the Hercules stream is most strongly seen in higher metallicity stars [Fe/H]>0.2. The Hercules stream peak v value depends on viewed galactic longitude, which we interpret as due to the gap between the stellar stream and more circular orbits being associated with a specific angular momentum value of about 1640 km s-1 kpc. The association of the gap with a particular angular momentum value supports a bar resonant model for the Hercules stream. Moving groups previously identified in Hipparcos observations are easiest to see in stars nearer than 250 pc, and their visibility and peak velocities in the velocity distributions depends on both viewing direction (galactic longitude and hemisphere) and metallicity. We infer that there is fine structure in local velocity distributions that varies over distances of a few hundred pc in the Galaxy.

The GALAH survey: stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere, and metallicity

NASA Astrophysics Data System (ADS)

Quillen, Alice C.; De Silva, Gayandhi; Sharma, Sanjib; Hayden, Michael; Freeman, Ken; Bland-Hawthorn, Joss; Žerjal, Maruša; Asplund, Martin; Buder, Sven; D'Orazi, Valentina; Duong, Ly; Kos, Janez; Lin, Jane; Lind, Karin; Martell, Sarah; Schlesinger, Katharine; Simpson, Jeffrey D.; Zucker, Daniel B.; Zwitter, Tomaz; Anguiano, Borja; Carollo, Daniela; Casagrande, Luca; Cotar, Klemen; Cottrell, Peter L.; Ireland, Michael; Kafle, Prajwal R.; Horner, Jonathan; Lewis, Geraint F.; Nataf, David M.; Ting, Yuan-Sen; Watson, Fred; Wittenmyer, Rob; Wyse, Rosemary

2018-07-01

Using GALAH (GALactic Archaeology with HERMES) survey data of nearby stars, we look at how structure in the planar (u, v) velocity distribution depends on metallicity and on viewing direction within the Galaxy. In nearby stars with distance d ≲ 1 kpc, the Hercules stream is most strongly seen in higher metallicity stars [Fe/H] > 0.2. The Hercules stream peak v value depends on viewed galactic longitude, which we interpret as due to the gap between the stellar stream and more circular orbits being associated with a specific angular momentum value of about 1640 km s-1 kpc. The association of the gap with a particular angular momentum value supports a bar resonant model for the Hercules stream. Moving groups previously identified in Hipparcos(HIgh Precision Parallax COllecting Satellite) observations are easiest to see in stars nearer than 250 pc, and their visibility and peak velocities in the velocity distributions depends on both viewing direction (galactic longitude and hemisphere) and metallicity. We infer that there is fine structure in local velocity distributions that varies over distances of a few hundred pc in the Galaxy.

The GALAH survey: properties of the Galactic disc(s) in the solar neighbourhood

NASA Astrophysics Data System (ADS)

Duong, L.; Freeman, K. C.; Asplund, M.; Casagrande, L.; Buder, S.; Lind, K.; Ness, M.; Bland-Hawthorn, J.; De Silva, G. M.; D'Orazi, V.; Kos, J.; Lewis, G. F.; Lin, J.; Martell, S. L.; Schlesinger, K.; Sharma, S.; Simpson, J. D.; Zucker, D. B.; Zwitter, T.; Anguiano, B.; Da Costa, G. S.; Hyde, E.; Horner, J.; Kafle, P. R.; Nataf, D. M.; Reid, W.; Stello, D.; Ting, Y.-S.; Wyse, R. F. G.

2018-06-01

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 ≲ R_GC ≲ 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° ≤ ℓ ≤ 280°). 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-α 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 α-abundance profile is almost flat, with a gradient of d[α/M]/dz = 0.008 ± 0.002 dex kpc-1. The steep vertical metallicity gradient of the low-α population is in agreement with models where radial migration has a major role in the evolution of the thin disc. The thick disc (high-α population) has a weaker vertical metallicity gradient d[M/H]/dz = -0.058 ± 0.003 dex kpc-1. The α-abundance of the thick disc is nearly constant with height, d[α/M]/dz = 0.007 ± 0.002 dex kpc-1. The negative gradient in metallicity and the small gradient in [α/M] indicate that the high-α population experienced a settling phase, but also formed prior to the onset of major Type Ia supernova enrichment. We explore the implications of the distinct α-enrichments and narrow [α/M] range of the sub-populations in the context of thick disc formation.

First light results from the HERMES spectrograph at the AAT

NASA Astrophysics Data System (ADS)

Sheinis, Andrew I.

2016-08-01

The High Efficiency and Resolution Multi Element Spectrograph, HERMES is a facility-class optical spectrograph for the AAT. It is designed primarily for Galactic Archeology, the first major attempt to create a detailed understanding of galaxy formation and evolution by studying the history of our own galaxy, the Milky Way. The goal of the Galactic Archeology with Hermes (GALAH) survey is to reconstruct the mass assembly history of the Milky Way, through a detailed spatially tagged abundance study of one million stars. The spectrograph is based at the Anglo Australian Telescope (AAT) and is fed by the existing 2dF robotic fiber positioning system. The spectrograph uses VPH-gratings to achieve a spectral resolving power of 28,000 in standard mode and also provides a high-resolution mode ranging between 40,000 to 50,000 using a slit mask. The GALAH survey requires a SNR greater than 100 for a star brightness of V=14. The total spectral coverage of the four channels is about 100nm between 370 and 1000nm for up to 392 simultaneous targets within the 2- degree field of view. Hermes was commissioned in late 2013, with the GALAH Pilot starting in parallel with the commissioning. The GALAH survey started in early 2014 is currently about 33% complete. We present a description of the motivating science; an overview the instrument; and a status report on GALAH Survey.

First light results from the Hermes spectrograph at the AAT

NASA Astrophysics Data System (ADS)

Sheinis, Andrew; Barden, Sam; Birchall, Michael; Carollo, Daniela; Bland-Hawthorn, Joss; Brzeski, Jurek; Case, Scott; Cannon, Russell; Churilov, Vladimir; Couch, Warrick; Dean, Robert; De Silva, Gayandhi; D'Orazi, Valentina; Farrell, Tony; Fiegert, Kristin; Freeman, Kenneth; Frost, Gabriella; Gers, Luke; Goodwin, Michael; Gray, Doug; Heald, Ron; Heijmans, Jeroen; Jones, Damien; Keller, Stephan; Klauser, Urs; Kondrat, Yuriy; Lawrence, Jon; Lee, Steve; Mali, Slavko; Martell, Sarah; Mathews, Darren; Mayfield, Don; Miziarski, Stan; Muller, Rolf; Pai, Naveen; Patterson, Robert; Penny, Ed; Orr, David; Shortridge, Keith; Simpson, Jeffrey; Smedley, Scott; Smith, Greg; Stafford, Darren; Staszak, Nicholas; Vuong, Minh; Waller, Lewis; Wylie de Boer, Elizabeth; Xavier, Pascal; Zheng, Jessica; Zhelem, Ross; Zucker, Daniel

2014-07-01

The High Efficiency and Resolution Multi Element Spectrograph, HERMES is an facility-class optical spectrograph for the AAT. It is designed primarily for Galactic Archeology [21], the first major attempt to create a detailed understanding of galaxy formation and evolution by studying the history of our own galaxy, the Milky Way. The goal of the GALAH survey is to reconstruct the mass assembly history of the of the Milky Way, through a detailed spatially tagged abundance study of one million stars. The spectrograph is based at the Anglo Australian Telescope (AAT) and is fed by the existing 2dF robotic fiber positioning system. The spectrograph uses VPH-gratings to achieve a spectral resolving power of 28,000 in standard mode and also provides a high-resolution mode ranging between 40,000 to 50,000 using a slit mask. The GALAH survey requires a SNR greater than 100 for a star brightness of V=14. The total spectral coverage of the four channels is about 100nm between 370 and 1000nm for up to 392 simultaneous targets within the 2 degree field of view. Hermes has been commissioned over 3 runs, during bright time in October, November and December 2013, in parallel with the beginning of the GALAH Pilot survey starting in November 2013. In this paper we present the first-light results from the commissioning run and the beginning of the GALAH Survey, including performance results such as throughput and resolution, as well as instrument reliability. We compare the abundance calculations from the pilot survey to those in the literature.

Interstellar Medium, Young Stars, and Astrometric Binaries in Galactic Archaeology Spectroscopic Surveys

NASA Astrophysics Data System (ADS)

Zwitter, T.; Kos, J.; Žerjal, M.; Traven, G.

2016-10-01

Current ongoing stellar spectroscopic surveys (RAVE, GALAH, Gaia-ESO, LAMOST, APOGEE, Gaia) are mostly devoted to studying Galactic archaeology and the structure of the Galaxy. But they allow also for important auxiliary science: (i) the Galactic interstellar medium can be studied in four dimensions (position in space plus radial velocity) through weak but numerous diffuse interstellar bands and atomic absorptions seen in spectra of background stars, (ii) emission spectra which are quite frequent even in field stars can serve as a good indicator of their youth, pointing e.g. to stars recently ejected from young stellar environments, (iii) an astrometric solution of the photocenter of a binary to be obtained by Gaia can yield accurate masses when joined by spectroscopic information obtained serendipitously during a survey. These points are illustrated by first results from the first three surveys mentioned above. These hint at the near future: spectroscopic studies of the dynamics of the interstellar medium can identify and quantify Galactic fountains which may sustain star formation in the disk by entraining fresh gas from the halo; RAVE already provided a list of ˜ 14,000 field stars with chromospheric emission in Ca II lines, to be supplemented by many more observations by Gaia in the same band, and by GALAH and Gaia-ESO observations of Balmer lines; several millions of astrometric binaries with periods up to a few years which are being observed by Gaia can yield accurate masses when supplemented with measurements from only a few high-quality ground based spectra.

Coma Berenices: The First Evidence for Incomplete Vertical Phase-mixing in Local Velocity Space with RAVE—Confirmed with Gaia DR2

NASA Astrophysics Data System (ADS)

Monari, G.; Famaey, B.; Minchev, I.; Antoja, T.; Bienaymé, O.; Gibson, B. K.; Grebel, E. K.; Kordopatis, G.; McMillan, P.; Navarro, J.; Parker, Q. A.; Quillen, A. C.; Reid, W.; Seabroke, G.; Siebert, A.; Steinmetz, M.; Wyse, R. F. G.; Zwitter, T.

2018-05-01

Before the publication of the Gaia DR2 we confirmed with RAVE and TGAS an observation recently made with the GALAH survey by Quillen ey al. concerning the Coma Berenices moving group in the Solar neighbourhood, namely that it is only present at negative Galactic latitudes. This allowed us to show that it is coherent in vertical velocity, providing a first evidence for incomplete vertical phase-mixing. We estimated for the first time from dynamical arguments that the moving group must have formed at most ~ 1.5 Gyr ago, and related this to a pericentric passage of the Sagittarius dwarf satellite galaxy. The present note is a rewritten version of the original arXiv post on this result now also including a confirmation of our finding with Gaia DR2.

Quantitative chemical tagging, stellar ages and the chemo-dynamical evolution of the Galactic disc

NASA Astrophysics Data System (ADS)

Mitschang, A. W.; De Silva, G.; Zucker, D. B.; Anguiano, B.; Bensby, T.; Feltzing, S.

2014-03-01

The early science results from the new generation of high-resolution stellar spectroscopic surveys, such as Galactic Archaeology with HERMES (GALAH) and the Gaia European Southern Observatory survey (Gaia-ESO), will represent major milestones in the quest to chemically tag the Galaxy. Yet this technique to reconstruct dispersed coeval stellar groups has remained largely untested until recently. We build on previous work that developed an empirical chemical tagging probability function, which describes the likelihood that two field stars are conatal, that is, they were formed in the same cluster environment. In this work, we perform the first ever blind chemical tagging experiment, i.e. tagging stars with no known or otherwise discernible associations, on a sample of 714 disc field stars with a number of high-quality high-resolution homogeneous metal abundance measurements. We present evidence that chemical tagging of field stars does identify coeval groups of stars, yet these groups may not represent distinct formation sites, e.g. as in dissolved open clusters, as previously thought. Our results point to several important conclusions, among them that group finding will be limited strictly to chemical abundance space, e.g. stellar ages, kinematics, colours, temperature and surface gravity do not enhance the detectability of groups. We also demonstrate that in addition to its role in probing the chemical enrichment and kinematic history of the Galactic disc, chemical tagging represents a powerful new stellar age determination technique.