Piercing the Milky Way: an all-sky view of the Orphan Stream

Koposov, S. E.; Belokurov, Vasily; Li, T. S.; Mateu, C.; Erkal, Denis; Grillmair, Carl J.; Hendel, David; Price-Whelan, Adrian M.; Laporte, Chervin F. P.; Hawkins, Keith; Sohn, Sangmo Tony; Pino, Andrés del; Evans, N. W.; Slater, Colin T.; Kallivayalil, Nitya; Navarro, Julio F.

doi:10.1093/mnras/stz457

Cited by 128 publications

(217 citation statements)

References 100 publications

(141 reference statements)

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“…Equipped with this data set, we also showed that the stars in GD-1 are moving along the stream and do not have a significant velocity perpendicular to the stream. This is in contrast to the Orphan stream which shows a significant offset due to the effect of the LMC Koposov et al 2019).…”

Section: Discussionmentioning

confidence: 65%

A closer look at the spur, blob, wiggle, and gaps in GD-1

Boer

Erkal

Gieles

2020

Monthly Notices of the Royal Astronomical Society

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The GD-1 stream is one of the longest and coldest stellar streams discovered to date, and one of the best objects for constraining the dark matter properties of the Milky Way. Using data from Gaia DR2 we study the proper motions, distance, morphology and density of the stream to uncover small scale perturbations. The proper motion cleaned data shows a clear distance gradient across the stream, ranging from 7 to 12 kpc. However, unlike earlier studies that found a continuous gradient, we uncover a distance minimum at ϕ 1 ≈-50 deg, after which the distance increases again. We can reliably trace the stream between -85< ϕ 1 <15 deg, showing an even further extent to GD-1 beyond the earlier extension of Price-Whelan & Bonaca (2018). We constrain the stream track and density using a Boolean matched filter approach and find three large under densities and find significant residuals in the stream track lining up with these gaps. In particular, a gap is visible at ϕ 1 =-3 deg, surrounded by a clear sinusoidal wiggle. We argue that this wiggle is due to a perturbation since it has the wrong orientation to come from a progenitor. We compute a total initial stellar mass of the stream segment of 1.58±0.07×10 4 M . With the extended view of the spur in this work, we argue that the spur may be unrelated to the adjacent gap in the stream. Finally, we show that an interaction with the Sagittarius dwarf can create features similar to the spur.

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Section: Discussionmentioning

confidence: 65%

A closer look at the spur, blob, wiggle, and gaps in GD-1

Boer

Erkal

Gieles

2020

Monthly Notices of the Royal Astronomical Society

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“…In particular, two streams, the ATLAS stream and the Aliqa Uma stream (at δ 2000 ∼ −35 • to −20 • in Figure 10), which were previously thought to be independent, are in fact a single stream from phase space information (S 5 et al in prep). 17 Here we treat Chenab and Orphan Stream separately although Koposov et al (2019) have shown that they are essentially one stream. We only show the stream targets in Chenab that are inside the DES footprint.…”

Section: Stream Resultsmentioning

confidence: 99%

“…This is to ensure that in the case that the proper motion of a stream was measured incorrectly, our target selection would still include some of the stream members. We choose a smaller range in µ φ 2 because the transverse motion of the stream (after solar reflex motion correction) is expected to be small except for cases where the streams have suffered large gravitational perturbations (see, e.g., the Orphan Stream; Koposov et al 2019;Erkal et al 2019).…”

Section: Stream Targets (P9-p7)mentioning

confidence: 99%

The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science

Koposov

Zucker

et al. 2019

Monthly Notices of the Royal Astronomical Society

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107

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We introduce the Southern Stellar Stream Spectroscopy Survey (S 5 ), an on-going program to map the kinematics and chemistry of stellar streams in the Southern Hemisphere. The initial focus of S 5 has been spectroscopic observations of recently identified streams within the footprint of the Dark Energy Survey (DES), with the eventual goal of surveying streams across the entire southern sky. Stellar streams are composed of material that has been tidally striped from dwarf galaxies and globular clusters and hence are excellent dynamical probes of the gravitational potential of the Milky Way, as well as providing a detailed snapshot of its accretion history. Observing with the 3.9-m Anglo-Australian Telescope's 2-degree-Field fibre positioner and AAOmega spectrograph, and combining the precise photometry of DES DR1 with the superb proper motions from Gaia DR2, allows us to conduct an efficient spectroscopic survey to map these stellar streams. So far S 5 has mapped 9 DES streams and 3 streams outside of DES; the former are the first spectroscopic observations of these recently discovered streams. In addition to the stream survey, we use spare fibres to undertake a Milky Way halo survey and a low-redshift galaxy survey. This paper presents an overview of the S 5 program, describing the scientific motivation for the survey, target selection, observation strategy, data reduction and survey validation. Finally, we describe early science results on stellar streams and Milky Way halo stars drawn from the survey. Updates on S 5 , including future public data release, can be found at http://s5collab.github.io.

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“…They discovered that the recently discovered Chenab Stream in the DES footprint (Shipp et al 2018) is actually part of the Southern extension of the Stream. The Chenab Stream and Grus II satellite are coincident in projection and proper motion coordinates (Koposov et al 2019, suggest there is a connection between the two substructures), however, Grus II is ∼10 kpc more distant than the Stream. The two brighter RRLs (V2 and V4) are at the correct distance to be Stream members and, in fact, they were pointed as likely Orphan Stream RRLs by Koposov et al (2019).…”

Section: Grus IImentioning

confidence: 91%

Search for RR Lyrae stars in DES ultrafaint systems: Grus I, Kim 2, Phoenix II, and Grus II

Martı́nez-Vázquez

Vivas

Gurevich

et al. 2019

Monthly Notices of the Royal Astronomical Society

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This work presents the first search for RR Lyrae stars (RRLs) in four of the ultra-faint systems imaged by the Dark Energy Survey (DES) using SOAR/Goodman and Blanco/DECam imagers. We have detected two RRLs in the field of Grus I, none in Kim 2, one in Phoenix II, and four in Grus II. With the detection of these stars, we accurately determine the distance moduli for these ultra-faint dwarf satellite galaxies; µ 0 =20.51±0.10 mag (D =127±6 kpc) for Grus I and µ 0 =20.01±0.10 mag (D =100±5 kpc) for Phoenix II. These measurements are larger than previous estimations by Koposov et al. 2015 andBechtol et al. 2015, implying larger physical sizes; 5% for Grus I and 33% for Phoenix II. For Grus II, out of the four RRLs detected, one is consistent with being a member of the galactic halo (D =24±1 kpc, µ 0 =16.86±0.10 mag), another is at D =55±2 kpc (µ 0 =18.71±0.10 mag), which we associate with Grus II, and the two remaining at D =43±2 kpc (µ 0 =18.17±0.10 mag). Moreover, the appearance of a subtle red horizontal branch in the color-magnitude diagram of Grus II at the same brightness level of the latter two RRLs, which are at the same distance and in the same region, suggests that a more metal-rich system may be located in front of Grus II. The most plausible scenario is the association of these stars with the Chenab/Orphan Stream. Finally, we performed a comprehensive and updated analysis of the number of RRLs in dwarf galaxies. This allows us to predict that the method of finding new ultra-faint dwarf galaxies by using two or more clumped RRLs will work only for systems brighter than M V ∼ −6 mag.

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Piercing the Milky Way: an all-sky view of the Orphan Stream

Cited by 128 publications

References 100 publications

A closer look at the spur, blob, wiggle, and gaps in GD-1

A closer look at the spur, blob, wiggle, and gaps in GD-1

The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science

Search for RR Lyrae stars in DES ultrafaint systems: Grus I, Kim 2, Phoenix II, and Grus II

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