TriAnd and its siblings: satellites of satellites in the Milky Way halo

Deason, Alis J.; Belokurov, V.; Hamren, Katherine; Koposov, S. E.; Gilbert, Karoline M.; Beaton, Rachael L.; Dorman, Claire E.; Guhathakurta, Puragra; Majewski, Steven R.; Cunningham, Emily C.

doi:10.1093/mnras/stu1764

Cited by 57 publications

(76 citation statements)

References 52 publications

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“…In contrast, as an example of substructure that is dynamically cold in LOS velocity, an approximate CDF for the Triangulum-Andromeda Stream (TriAnd; located along the LOS toward M31) is shown in red (v 0 ∼50 km s −1 , σ∼15 km s −1 ; e.g., Deason et al 2014;Sheffield et al 2014). D13 suggested that the presence of a cold stream or TriAnd could be the reason for the relative increase in tangential pressure seen in this sample.…”

Section: And Emsellem (2004)mentioning

confidence: 87%

Isotropic at the Break? 3d Kinematics of Milky Way Halo Stars in the Foreground of M31

Cunningham

Deason

Guhathakurta

et al. 2016

ApJ

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We present the line-of-sight (LOS) velocities for 13 distant main sequence Milky Way halo stars with published proper motions (PMs). The PMs were measured using long baseline (5-7 years) multi-epoch Hubble Space Telescope/Advanced Camera for Surveys photometry, and the LOS velocities were extracted from deep (5-6 hr integrations) Keck II/DEIMOS spectra. We estimate the parameters of the velocity ellipsoid of the stellar halo using a Markov chain Monte Carlo ensembler sampler method. The velocity second moments in the directions of the Galactic (l, b, LOS) coordinate system are v 138 We use these ellipsoid parameters to constrain the velocity anisotropy of the stellar halo. Ours is the first measurement of the anisotropy parameter β using 3D kinematics outside of the solar neighborhood. We find 0.3 0.9 0.4 b = --+ , consistent with isotropy and lower than solar neighborhood β measurements by 2σ (β SN ∼0.5-0.7). We identify two stars in our sample that are likely members of the known TriAnd substructure, and excluding these objects from our sample increases our estimate of the anisotropy to 0.1 1.0which is still lower than solar neighborhood measurements by 1σ. The potential decrease in β with Galactocentric radius is inconsistent with theoretical predictions, though consistent with recent observational studies, and may indicate the presence of large, shell-type structure (or structures) at r∼25 kpc. The methods described in this paper will be applied to a much larger sample of stars with 3D kinematics observed through the ongoing HALO7D program.

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Section: And Emsellem (2004)mentioning

confidence: 87%

Isotropic at the Break? 3d Kinematics of Milky Way Halo Stars in the Foreground of M31

Cunningham

Deason

Guhathakurta

et al. 2016

ApJ

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“…This suggests that there may actually be an association between the MW stream and TriAnd1 and/or TriAnd2. The recent work of Deason et al (2014) further suggests a common origin between the TriAnd1/TriAnd2 features and the PAndAS MW stream.…”

Section: The Pandas "Field Of Streams"mentioning

confidence: 90%

Exploring Halo Substructure With Giant Stars. Xiv. The Nature of the Triangulum-Andromeda Stellar Features

Sheffield

Johnston

Majewski

et al. 2014

ApJ

112

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As large-scale stellar surveys have become available over the past decade, the ability to detect and characterize substructures in the Galaxy has increased dramatically. These surveys have revealed the Triangulum-Andromeda (TriAnd) region to be rich with substructures in the distance range 20-30 kpc, and the relation of these features to each other, if any, remains unclear. An exploration using Two Micron All Sky Survey (2MASS) photometry reveals not only the faint sequence in M giants detected by Rocha-Pinto et al. spanning the range 100 • < l < 160 • and −50 • < b < −15 • , but, in addition, a second, brighter and more densely populated sequence. These sequences are likely associated with the distinct main sequences (MSs) discovered (and labeled TriAnd1 and TriAnd2) by Martin et al. in an optical survey in the direction of M31, where TriAnd2 is the optical counterpart of the fainter red giant branch (RGB)/asymptotic giant branch sequence of Rocha-Pinto et al. Here, the age, distance, and metallicity ranges for TriAnd1 and TriAnd2 are estimated by simultaneously fitting isochrones to the 2MASS RGB tracks and the optical MS/MS turn-off features. The two populations are clearly distinct in age and distance: the brighter sequence (TriAnd1) is younger (6-10 Gyr) and closer (distance of ∼15-21 kpc), whereas the fainter sequence (TriAnd2) is older (10-12 Gyr) and at an estimated distance of ∼24-32 kpc. A comparison with simulations demonstrates that the differences and similarities between TriAnd1 and TriAnd2 can simultaneously be explained if they represent debris originating from the disruption of the same dwarf galaxy, but torn off during two distinct pericentric passages.

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“…The properties of the individual satellites are also interesting in their own right as they could hold important clues on the group preprocessing that most dwarf galaxies are thought to have experienced before being accreted onto a more massive host (e.g., Deason et al 2014;Wetzel et al 2015 for the massscale relevant here). Work has only just started to better characterize the new systems (e.g., Kirby et al 2015;Simon et al 2015;Walker et al 2015aWalker et al , 2015b and, in particular, to understand which are dark-matter-dominated dwarf galaxies, which are globular clusters, and how the dynamical LMC-SMC group environment has affected them.…”

Section: Introductionmentioning

confidence: 99%

Smash 1: A Very Faint Globular Cluster Disrupting in the Outer Reaches of the Lmc?

Martín

Jungbluth

Nidever

et al. 2016

ApJL

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We present the discovery of a very faint stellar system, SMASH 1, that is potentially a satellite of the Large Magellanic Cloud. Found within the Survey of the MAgellanic Stellar History (SMASH), SMASH 1 is a compact ( r 9.1 pc h 3.4 5.9) and very low luminosity ( M) stellar system that is revealed by its sparsely populated main sequence and a handful of red giant branch candidate member stars. The photometric properties of these stars are compatible with a metal-poor ( Fe H 2.2 [ ] ) and old (13 Gyr) isochrone located at a distance modulus of ∼18.8, i.e., a distance of 57 kpc. Situated at 11°. 3 from the LMC in projection, its three-dimensional distance from the Cloud is 13 kpc, consistent with a connection to the LMC, whose tidal radius is at least 16 kpc. Although the nature of SMASH 1 remains uncertain, its compactness favors it being a stellar cluster and hence dark-matter free. If this is the case, its dynamical tidal radius is only 19 pc at this distance from the LMC, and smaller than the system's extent on the sky. Its low luminosity and apparent high ellipticity ( 0.62 0.21 0.17 ) with its major axis pointing toward the LMC may well be the tell-tale sign of its imminent tidal demise.

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TriAnd and its siblings: satellites of satellites in the Milky Way halo

Cited by 57 publications

References 52 publications

Isotropic at the Break? 3d Kinematics of Milky Way Halo Stars in the Foreground of M31

Isotropic at the Break? 3d Kinematics of Milky Way Halo Stars in the Foreground of M31

Exploring Halo Substructure With Giant Stars. Xiv. The Nature of the Triangulum-Andromeda Stellar Features

Smash 1: A Very Faint Globular Cluster Disrupting in the Outer Reaches of the Lmc?

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