The Galaxy in Context: Structural, Kinematic, and Integrated Properties

Bland-Hawthorn, Joss; Gerhard, Ortwin

doi:10.1146/annurev-astro-081915-023441

Cited by 1,435 publications

(972 citation statements)

References 500 publications

(691 reference statements)

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“…This "Galactic archaeology" remains the principal basis by which models for the formation and chemodynamical evolution of the Milky Way and analogous systems are formulated and refined. The vast literature on Milky Way stellar populations as tools for understanding Galactic evolution has been reviewed in the past by, e.g., Gilmore et al (1989), Majewski (1993), and Freeman & Bland-Hawthorn (2002), and more recently by Ivezić et al (2012), Rix & Bovy (2013), and Bland-Hawthorn & Gerhard (2016).…”

Section: Galactic Archaeology Surveysmentioning

confidence: 99%

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

et al. 2017

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The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R ∼ 22,500), high signal-to-noise ratio (>100), infrared (1.51–1.70 μm) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design—hardware, field placement, target selection, operations—and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available.

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Section: Galactic Archaeology Surveysmentioning

confidence: 99%

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

et al. 2017

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“…Our choice for the mass of the bulge is significantly higher compared to the latest observational constraints (Bland-Hawthorn & Gerhard 2016;McMillan 2017), therefore we integrate each candidate assuming a bulge mass equal to half the previous adopted value: M b = 1.7 × 10 10 M , keeping fixed all the other parameters. As a second test, we adopt the potential in Kenyon et al (2014), commonly adopted in HVS papers, which has a less massive bulge and stellar disc (but different scale parameters).…”

Section: −30mentioning

confidence: 99%

An artificial neural network to discover hypervelocity stars: candidates in Gaia DR1/TGAS

Marchetti

Rossi

Kordopatis

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The paucity of hypervelocity stars (HVSs) known to date has severely hampered their potential to investigate the stellar population of the Galactic Centre and the Galactic Potential. The first Gaia data release (DR1, 2016 September 14) gives an opportunity to increase the current sample. The challenge is the disparity between the expected number of hypervelocity stars and that of bound background stars. We have applied a novel data mining algorithm based on machine learning techniques, an artificial neural network, to the Tycho-Gaia astrometric solution (TGAS) catalogue. With no pre-selection of data, we could exclude immediately ∼ 99% of the stars in the catalogue and find 80 candidates with more than 90% predicted probability to be HVSs, based only on their position, proper motions, and parallax. We have cross-checked our findings with other spectroscopic surveys, determining radial velocities for 30 and spectroscopic distances for 5 candidates. In addition, follow-up observations have been carried out at the Isaac Newton Telescope for 22 stars, for which we obtained radial velocities and distance estimates. We discover 14 stars with a total velocity in the Galactic rest frame > 400 km s −1 , and 5 of these have a probability > 50% of being unbound from the Milky Way. Tracing back their orbits in different Galactic potential models we find one possible unbound HVS with v ∼ 520 km s −1 , 5 bound HVSs, and, notably, 5 runaway stars with median velocity between 400 and 780 km s −1 . At the moment, uncertainties in the distance estimates and ages are too large to confirm the nature of our candidates by narrowing down their ejection location, and we wait for future Gaia releases to validate the quality of our sample. This test successfully demonstrates the feasibility of our new data mining routine.

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“…Eri II is most likely located just beyond the virial radius of the Milky Way, which is typically estimated to be ∼300 kpc (Bland-Hawthorn & Gerhard 2016;Taylor et al 2016). This places Eri II in a sharp transition region between the gas-free dwarf spheroidals (with D250 kpc) and the more distant gas-rich star-forming dwarfs (Einasto et al 1974;Blitz & Robishaw 2000;Grcevich & Putman 2009;Spekkens et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Farthest Neighbor: The Distant Milky Way Satellite Eridanus II*

Simon

Drlica-Wagner

et al. 2017

ApJ

153

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We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite EridanusII (Eri II).We identify 28 member stars in EriII, from which we measure a systemic radial velocity of () 1 the bright blue stars previously suggested to be a young stellar population are not associated with EriII. The lack of gas and recent star formation in EriII is surprising given its mass and distance from the Milky Way, and may place constraints on models of quenching in dwarf galaxies and on the distribution of hot gas in the Milky Way halo. Furthermore, the large velocity dispersion of Eri II can be combined with the existence of a central star cluster to constrain massive compact halo object dark matter with mass 10  M .

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The Galaxy in Context: Structural, Kinematic, and Integrated Properties

Cited by 1,435 publications

References 500 publications

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

An artificial neural network to discover hypervelocity stars: candidates in Gaia DR1/TGAS

Farthest Neighbor: The Distant Milky Way Satellite Eridanus II*

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