The Geometry of the Sagittarius Stream from Pan-STARRS1 3π RR Lyrae

Hernitschek, Nina; Sesar, Branimir; Rix, Hans─Walter; Belokurov, V.; Martínez–Delgado, David; Martín, Nicolás F.; Kaiser, Nick; Hodapp, Klaus W.; Chambers, K.; Wainscoat, R. J.; Magnier, E. A.; Kudritzki, Rolf‐Peter; Metcalfe, N.; Draper, P. W.

doi:10.3847/1538-4357/aa960c

Cited by 70 publications

(112 citation statements)

References 60 publications

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“…Variable stars, and particularly RR Lyrae stars, are excellent tracers of extra-tidal material around disrupting galaxies. RR Lyrae stars, for example, trace the tidal tails of the Sagittarius dSph galaxy (e.g., Hernitschek et al 2017). Extra-tidal RR Lyrae stars have also been found in other satellites such as Carina (Vivas & Mateo 2013) and the Hercules UFD (Garling et al 2018).…”

Section: Discussionmentioning

confidence: 99%

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

Vivas

Walker

Martı́nez-Vázquez

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Time series observations of a single dithered field centered on the diffuse dwarf satellite galaxy Crater II were obtained with the Dark Energy Camera (DECam) at the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile, uniformly covering up to two half-light radii. Analysis of the g and i time series results in the identification and characterization of 130 periodic variable stars, including 98 RR Lyrae stars, 7 anomalous Cepheids, and 1 SX Phoenicis star belonging to the Crater II population, and 24 foreground variables of different types. Using the large number of ab-type RR Lyrae stars present in the galaxy, we obtained a distance modulus to Crater II of (m − M) 0 = 20.333 ± 0.004 (stat) ±0.07 (sys). The distribution of the RR Lyrae stars suggests an elliptical shape for Crater II, with an ellipticity of 0.24 and a position angle of 153 • . From the RR Lyrae stars we infer a small metallicity dispersion for the old population of Crater II of only 0.17 dex. There are hints that the most metal-poor stars in that narrow distribution have a wider distribution across the galaxy, while the slightly more metal rich part of the population is more centrally concentrated. Given the features in the color-magnitude diagram of Crater II, the anomalous Cepheids in this galaxy must have formed through a binary evolution channel of an old population.

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Section: Discussionmentioning

confidence: 99%

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

Vivas

Walker

Martı́nez-Vázquez

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…By comparing the FoF groups with observations and simulations of Sgr (Law & Majewski 2010;Koposov et al 2012;Belokurov et al 2014;Dierickx & Loeb 2017;Hernitschek et al 2017), X19 identified 3028 Sgr stream members, including 2626 K-giants (including 102 suspected duplicate stars), 158 M-giants, and 224 BHBs, which is the largest spectroscopic sample obtained in the Sgr stream yet. In the next section, we will exhibit the Sgr members in detail, including spatial, kinematic, and abundance features.…”

Section: Integrals Of Motion and Friends-of-friends Algorithmmentioning

confidence: 99%

Tracing Kinematic and Chemical Properties of Sagittarius Stream by K-Giants, M-Giants, and BHB stars

Yang

Xue²,

et al. 2019

ApJ

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We characterize the kinematic and chemical properties of ∼3,000 Sagittarius (Sgr) stream stars, including K-giants, M-giants, and BHBs, select from SEGUE-2, LAMOST, and SDSS separately in Integrals-of-Motion space. The orbit of Sgr stream is quite clear from the velocity vector in X-Z plane. Stars traced by K-giants and M-giants present the apogalacticon of trailing steam is ∼ 100 kpc. The metallicity distributions of Sgr K-, M-giants, and BHBs present that the M-giants are on average the most metal-rich population, followed by K-giants and BHBs. All of the K-, M-giants, and BHBs indicate that the trailing arm is on average more metal-rich than leading arm, and the K-giants show that the Sgr debris is the most metal-poor part. The α-abundance of Sgr stars exhibits a similar trend with the Galactic halo stars at lower metallicity ([Fe/H] <∼ −1.0 dex), and then evolve down to lower [α/Fe] than disk stars at higher metallicity, which is close to the evolution pattern of α-element of Milky Way dwarf galaxies. We find V Y and metallicity of K-giants have gradients along the direction of line-of-sight from the Galactic center in X-Z plane, and the K-giants show that V Y increases with metallicity at [Fe/H] >∼ −1.5 dex. After dividing the Sgr stream into bright and faint stream according to their locations in equatorial coordinate, the K-giants and BHBs show that the bright and faint stream present different V Y and metallicities, the bright stream is on average higher in V Y and metallicity than the faint stream.

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“…To do so, we apply the selection cuts described in Section 3.2, to geometrically excise such overdensities. The largest overdensities removed are the Sagittarius stream (we remove sources associated with the Sgr stream according to Hernitschek et al 2017), as well as the thick disk (we remove sources within <  | | b 10 ) and close to the Galactic center and the bulge (we remove sources within R gc 20 kpc). Showing the source density in three different distance bins shows major overdensities, as well as how excising such overdense regions affects the cleaned sample.…”

Section: Rrlmentioning

confidence: 99%

The Profile of the Galactic Halo from Pan-STARRS1 3π RR Lyrae

Hernitschek

Cohen

Rix

et al. 2018

ApJ

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We characterize the spatial density of the Pan-STARRS1 (PS1) sample of Rrab stars to study the properties of the old Galactic stellar halo. This sample, containing 44,403 sources, spans galactocentric radii of 0.55 kpcR gc 141 kpc with a distance precision of 3% and thus is able to trace the halo out to larger distances than most previous studies. After excising stars that are attributed to dense regions such as stellar streams, the Galactic disk and bulge, and halo globular clusters, the sample contains ∼11,000 sources within 20 kpcR gc 131 kpc. We then apply forward modeling using Galactic halo profile models with a sample selection function. Specifically, we use ellipsoidal stellar density models ρ(l, b, R gc ) with a constant and a radiusdependent halo flattening q(R gc ). Assuming constant flattening q, the distribution of the sources is reasonably well fit by a single power law with = 0.27 , an effective radius r eff =1.07±0.10 kpc, and a halo flattening of q=0.923±0.007. If we allow for a radius-dependent flattening q(R gc ), we find evidence for a distinct flattening of q∼0.8 of the inner halo at ∼25 kpc. Additionally, we find that the south Galactic hemisphere is more flattened than the north Galactic hemisphere. The results of our work are largely consistent with many earlier results (e.g., Watkins et al.; Iorio et al.). We find that the stellar halo, as traced in RR Lyrae stars, exhibits a substantial number of further significant over-and underdensities, even after masking all known overdensities.

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The Geometry of the Sagittarius Stream from Pan-STARRS1 3π RR Lyrae

Cited by 70 publications

References 60 publications

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

A DECam view of the diffuse dwarf galaxy Crater II – Variable stars

Tracing Kinematic and Chemical Properties of Sagittarius Stream by K-Giants, M-Giants, and BHB stars

The Profile of the Galactic Halo from Pan-STARRS1 3π RR Lyrae

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