The QUEST RR Lyrae Survey: Confirmation of the Clump at 50 Kiloparsecs and Other Overdensities in the Outer Halo

Vivas, A. Katherina; Zinn, R.; Andrews, P.; Bailyn, Charles D.; Baltay, C.; Coppi, P.; Ellman, N.; Girard, Terrence M.; Rabinowitz, D.; Schaefer, Bradley E.; Shin, Jihye; Snyder, J.; Sofia, S.; Altena, W. van; Abad, C.; Bongiovanni, Á.; Briceño, César; Bruzual, G.; Prugna, F. Della; Herrera, David; Magris, G.; Mateu, J.; Pacheco, R.; Sánchez, G.; Sánchez, Gu.; Schenner, H.; Stock, J.; Vicente, B.; Vieira, K.; Ferrin, Ignacio; Hernández, Jesús; Gebhard, M.; Honeycutt, R. K.; Mufson, S.; Musser, J.; Rengstorf, A. W.

doi:10.1086/320915

Cited by 216 publications

(170 citation statements)

References 26 publications

(20 reference statements)

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“…The multiple globular cluster visits also make it possible to increase the number of cluster stars to be sampled, given the limitations posed by fiber collisions ( Table 2). Additional high-latitude deep pointings were placed in fields traversed by halo substructures, such as the Sagittarius stream (with field placement guided, e.g., by the results of Majewski et al 2003) or the Virgo Overdensity (e.g., Vivas et al 2001;Newberg et al 2007;Jurić et al 2008).…”

Section: Field Selection Evolutionmentioning

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: Field Selection Evolutionmentioning

confidence: 99%

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

et al. 2017

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“…In both cases the interpretation of an extra-galactic origin for these features is not clear and their possible relationship with the galactic disk is still under investigation (see Price-Whelan et al 2015;Xu et al 2015). At high galactic latitudes and far from the disk, there are several other structures: the Virgo overdensity (VOD, Vivas et al 2001;Newberg et al 2002;Duffau et al 2006;Jurić et al 2008;Bonaca et al 2012;Duffau et al 2014), the Hercules-Aquila cloud (Belokurov et al 2007;Watkins et al 2009;Simion et al 2014), the Pisces overdensity (Sesar et al 2007;Watkins et al 2009;Kollmeier et al 2009;Sesar et al 2010) and the Eridanus-Phoenix overdensity (Li et al 2016). Although their interpretation as merger event, or events, is less ambiguous, the specific merging history is still unknown.…”

Section: Introductionmentioning

confidence: 99%

“…RRLS are abundant in the VOD, and indeed, this type of stars provided the first indication of an overdensity (Vivas et al 2001). The main advantage of using RRLS as tracers of the old population of halo sub-structures is that they are excellent standard candles.…”

Section: Introductionmentioning

confidence: 99%

Disentangling the Virgo Overdensity With Rr Lyrae Stars

Vivas

Zinn

Farmer

et al. 2016

ApJ

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We use a combination of spatial distribution and radial velocity to search for halo sub-structures in a sample of 412 RR Lyrae stars (RRLS) that covers a ∼ 525 square degrees region of the Virgo Overdensity (VOD) and spans distances from the Sun from 4 to 75 kpc. With a friends-of-friends algorithm we identified six high significance groups of RRLS in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high significance and 3 lower significance groups have distances between ∼ 10 and 20 kpc, which places them with the distance range attributed by others to the VOD. The largest of these is the Virgo Stellar Stream (VSS) at 19 kpc, which has 18 RRLS, a factor of 2 increase over the number known previously. While these VOD groups are distinct according to our selection cirteria, their overlap in position and distance, and, in a few cases, similarity in radial velocity are suggestive that they may not all stem separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sgr stream is a very obvious feature in the background of the VOD at a mean distance of 44 kpc. Two additional high significant groups were detected at distances > 40 kpc. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.

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“…Majewski et al 2003), the Virgo region contains the most obvious overdensity of stars in the sky explored so far by large scale surveys. Discovered as an overdensity of RR Lyrae stars (RRLS) in the QUEST survey (Vivas et al 2001;Vivas 2002;Duffau et al 2006) and of main-sequence turn-off stars (Newberg et al 2002) in the SDSS, it is one of the most noticeable features in the Field of Streams (Belokurov et al 2006). Based in main sequence stars from SDSS, Jurić et al (2008) estimated that the substructure, covers ∼1000 sq deg of the sky.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive view of the Virgo stellar stream

Duffau

Vivas

Zinn

et al. 2014

A&A

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To explore the complex halo substructure that has been reported in the direction of the Virgo constellation, radial velocities and metallicities have been measured for 82 RR Lyrae stars (RRLS) that were identified by the QUEST survey. These stars are distributed over 90 square degrees of the sky, and lie from 4 to 23 kpc from the Sun. Using an algorithm for finding groups in phase space and modeling the smooth halo component in the region, we identified the 5 most significant RRLS groups, some of which were previously known or suspected. We have examined the SEKBO and the Catalina catalog of RRLS (with available spectroscopic measurements), as well as the bright QUEST RRLS sample, the catalog of Red Giant stars from the Spaghetti survey, and three recent catalogs of blue horizontal branch (BHB) stars, for stars that may be related to the QUEST RRLS groups. The most significant group of RRLS is the Virgo stellar stream (VSS) identified here as group A, which is composed of at least 10 RRLS and 3 BHB stars. It has a mean distance of 19.6 kpc and a mean radial velocity V gsr = 128 km s −1 , as estimated from its RRLS members. With the revised velocities reported here, there is no longer an offset in velocity between the RRLS in the VSS and the prominent peak in the velocities of main-sequence turnoff stars reported by other researchers in the same direction and at a similar distance (known as S297+63-20.5). The location in phase space of two other groups (F and H) suggests a possible connection with the VSS, which cannot be discarded at this point, although the turnoff colors of the VSS and group H, as identified from other works, suggest they might be composed of different populations. Two more groups, B and D, are found at mean distances of 19.0 and 5.7 kpc, and mean radial velocities of V gsr = −94 and 32 km s −1 . The latter is the more numerous in terms of total members, as well as the more extended in RA. A comparison with the latest model of the disruption of the Sagittarius dwarf, indicates that none of the above groups is related to it. Rather than being the result of a single accretion event, the excess of stars observed in Virgo appears to be composed of several halo substructures along the same line of sight.

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The QUEST RR Lyrae Survey: Confirmation of the Clump at 50 Kiloparsecs and Other Overdensities in the Outer Halo

Cited by 216 publications

References 26 publications

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

Disentangling the Virgo Overdensity With Rr Lyrae Stars

A comprehensive view of the Virgo stellar stream

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