The Hercules-Aquila Cloud

Belokurov, V.; Evans, N. W.; Bell, Eric F.; Irwin, M. J.; Hewett, Paul C.; Koposov, S. E.; Rockosi, C. M.; Gilmore, G.; Zucker, D. B.; Fellhauer, M.; Wilkinson, M. I.; Bramich, D. M.; Vidrih, S.; Rix, Hans─Walter; Beers, Timothy C.; Schneider, Donald P.; Barentine, John C.; Brewington, H.; Brinkmann, J.; Harvanek, Michael; Krzesiński, Jurek; Long, D.; Pan, K.; Snedden, Stephanie A.; Malanushenko, O.; Malanushenko, V. P.

doi:10.1086/513144

Cited by 167 publications

(173 citation statements)

References 20 publications

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“…The random errors increase from ∼3 mas yr −1 at the bright end to ∼6 mas yr −1 at r ∼ 20 (the sample completeness limit), with systematic errors that are typically an order of magnitude smaller, and with very small variation across the sky (for a discussion of deviations from Gaussian error behavior, see Dong et al 2011). Even for stars at distances of 1 kpc, the implied tangential velocity errors are as small as [10][11][12][13][14][15][16][17][18][19][20] km s −1 , and well matched to the SDSS radial velocity accuracy. This catalog represents a major improvement over previously available data sets both in size …”

Section: The Sdss-poss Proper-motion Surveymentioning

confidence: 53%

Galactic Stellar Populations in the Era of the Sloan Digital Sky Survey and Other Large Surveys

Ivezić

Beers

Jurić

2012

Annu. Rev. Astron. Astrophys.

143

128

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Studies of stellar populations, understood to mean collections of stars with common spatial, 2 Ivezić, Beers & Jurić kinematic, chemical, and/or age distributions, have been reinvigorated during the last decade by the advent of large-area sky surveys such as SDSS, 2MASS, RAVE, and others. We review recent analyses of these data that, together with theoretical and modeling advances, are revolutionizing our understanding of the nature of the Milky Way, and galaxy formation and evolution in general.The formation of galaxies like the Milky Way was long thought to be a steady process leading to a smooth distribution of stars. However, the abundance of substructure in the multi-dimensional space of various observables, such as position, kinematics, and metallicity, is by now proven beyond doubt, and demonstrates the importance of mergers in the growth of galaxies. Unlike smooth models that involve simple components, the new data reviewed here clearly exhibit many irregular structures, such as the Sagittarius dwarf tidal stream and the Virgo and Pisces overdensities in the halo, and the Monoceros stream closer to the Galactic plane. These recent developments have made it clear that the Milky Way is a complex and dynamic structure, one that is still being shaped by the merging of neighboring smaller galaxies. We also briefly discuss the next generation of wide-field sky surveys, such as SkyMapper, Pan-STARRS, Gaia, and LSST, which will improve measurement precision manyfold, and comprise billions of individual stars. The ultimate goal, development of a coherent and detailed story of the assembly and evolutionary history of the Milky Way and other large spirals like it, now appears well within reach.

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Section: The Sdss-poss Proper-motion Surveymentioning

confidence: 53%

Galactic Stellar Populations in the Era of the Sloan Digital Sky Survey and Other Large Surveys

Ivezić

Beers

Jurić

2012

Annu. Rev. Astron. Astrophys.

143

128

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“…We fit an isochrone with fixed age and metallicity (t = 13.0 Gyr, Z=0.0004) and find a best-fit distance modulus of -= m M 16.1, which is indistinguishable from that of EriPhe and the nearby globular cluster NGC 1261. Li et al (2016) suggest that EriPhe may have a common origin with the Virgo overdensity (Jurić et al 2008) and the HerculesAquila cloud (Belokurov et al 2007a). However, the orientation of Turbio is nearly perpendicular with the orbit necessary to connect these three diffuse structures.…”

Section: Turbio Streammentioning

confidence: 99%

Stellar Streams Discovered in the Dark Energy Survey

Shipp

Drlica-Wagner

Balbinot

et al. 2018

ApJ

Self Cite

257

254

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We perform a search for stellar streams around the Milky Way using the first 3 yr of multiband optical imaging data from the Dark Energy Survey (DES). We use DES data covering ∼5000 deg 2 to a depth of g>23.5 with a relative photometric calibration uncertainty of <1%. This data set yields unprecedented sensitivity to the stellar density field in the southern celestial hemisphere, enabling the detection of faint stellar streams to a heliocentric distance of ∼50 kpc. We search for stellar streams using a matched filter in color-magnitude space derived from a synthetic isochrone of an old, metal-poor stellar population. Our detection technique recovers four previously known thin stellar streams: Phoenix, ATLAS, Tucana III, and a possible extension of Molonglo. In addition, we report the discovery of 11 new stellar streams. In general, the new streams detected by DES are fainter, more distant, and lower surface brightness than streams detected by similar techniques in previous photometric surveys. As a by-product of our stellar stream search, we find evidence for extratidal stellar structure associated with four globular clusters: NGC 288, NGC 1261, NGC 1851, and NGC 1904. The ever-growing sample of stellar streams will provide insight into the formation of the Galactic stellar halo, the Milky Way gravitational potential, and the large-and small-scale distribution of dark matter around the Milky Way.

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“…The first evidence of accretion came from studies of globular clusters (Searle & Zinn 1978), but in recent years, deep photometric surveys on large scales have revealed a plethora of systems undergoing tidal disruption in the Milky Way halo, with progenitors ranging from dwarf galaxies (e.g., Ibata et al 1994;Belokurov et al 2007aBelokurov et al , 2007bJurić et al 2008;Bonaca et al 2012b) to disrupted globular clusters (e.g., Rockosi et al 2002;Grillmair & Dionatos 2006;Grillmair 2009;Bonaca et al 2012a;Bernard et al 2016). A complete list of tidal structures identified in the Milky Way has recently been compiled by Grillmair & Carlin (2016).…”

Section: Introductionmentioning

confidence: 99%

Gaia Reveals a Metal-rich, in situ Component of the Local Stellar Halo

Bonaca

Conroy

Wetzel

et al. 2017

ApJ

204

203

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We use the first Gaia data release, combined with the RAVE and APOGEE spectroscopic surveys, to investigate the origin of halo stars within 3 kpc from the Sun. We identify halo stars kinematically as moving at a relative speed of at least 220 km s −1 with respect to the local standard of rest. These stars are generally less metal-rich than the disk, but surprisingly, half of our halo sample is comprised of stars withThe orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation, in sharp contrast with the intrinsically isotropic orbital distribution of the metal-poor halo stars. We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project. In Latte, metal-rich halo stars formed primarily inside of the solar circle, whereas lower-metallicity halo stars preferentially formed at larger distances (extending beyond the virial radius). This suggests that metal-rich halo stars in the solar neighborhood actually formed in situ within the Galactic disk, rather than having been accreted from satellite systems. These stars, currently on halo-like orbits, therefore have likely undergone substantial radial migration/heating.

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The Hercules-Aquila Cloud

Cited by 167 publications

References 20 publications

Galactic Stellar Populations in the Era of the Sloan Digital Sky Survey and Other Large Surveys

Galactic Stellar Populations in the Era of the Sloan Digital Sky Survey and Other Large Surveys

Stellar Streams Discovered in the Dark Energy Survey

Gaia Reveals a Metal-rich, in situ Component of the Local Stellar Halo

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