Constraining the Milky Way mass with hypervelocity stars

Fragione, Giacomo; Loeb, Abraham

doi:10.1016/j.newast.2017.03.002

Cited by 46 publications

(33 citation statements)

References 54 publications

(96 reference statements)

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“…In fact, estimates based on v Gibbons et al (2014), and lying on the lower end of the intervals provided by McMillan (2011); Fragione & Loeb (2016);McMillan (2016). This is largely independent of the choice of vtan.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Constraining the mass of the Local Group

Carlesi¹,

Hoffman²,

Sorce

et al. 2016

Mon. Not. R. Astron. Soc.

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The mass of the Local Group (LG) is a crucial parameter for galaxy formation theories. However, its observational determination is challenging -its mass budget is dominated by dark matter which cannot be directly observed. To meet this end the posterior distributions of the LG and its massive constituents have been constructed by means of constrained and random cosmological simulations. Two priors are assumed -the ΛCDM model that is used to set up the simulations and a LG model, which encodes the observational knowledge of the LG and is used to select LG-like objects from the simulations. The constrained simulations are designed to reproduce the local cosmography as it is imprinted onto the Cosmicflows-2 database of velocities. Several prescriptions are used to define the LG model, focusing in particular on different recent estimates of the tangential velocity of M31. It is found that (a) different v tan choices affect the peak mass values up to a factor of 2, and change mass ratios of M M31 to M MW by up to 20%; (b) constrained simulations yield more sharply peaked posterior distributions compared with the random ones; (c) LG mass estimates are found to be smaller than those found using the timing argument; (d) preferred MW masses lie in the range of (0.6 − 0.8) × 10 12 M whereas (e) M M31 is found to vary between (1.0 − 2.0) × 10 12 M , with a strong dependence on the v tan values used.

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Section: Discussionmentioning

confidence: 99%

“…This is true in particular in the CS case, for which v McMillan (2011McMillan ( , 2016 modelling the mass distribution of the Galaxy, as well as the 1.2 − 1.7 × 10 12 M constraints of Fragione & Loeb (2016) obtained using ultra high velocity stars. Moreover, such a light mass would in turn disfavour a bound orbit for Leo I.…”

Section: Individual Massesmentioning

confidence: 92%

Constraining the mass of the Local Group

Carlesi¹,

Hoffman²,

Sorce

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Eadie & Harris 2016;Posti & Helmi 2019;Watkins et al 2019) and satellite galaxies (e.g. Watkins et al 2010;Li et al 2017;Patel et al 2017;Callingham et al 2019b), high velocity stars (e,g, Smith et al 2007;Piffl et al 2014;Fragione & Loeb 2017;Rossi et al 2017;Deason et al 2019b), the orbits of tidal streams (e.g. Gibbons et al 2014;Bowden et al 2015), the luminosity function of the MW satellites (e.g.…”

Section: Introductionmentioning

confidence: 99%

The milky way total mass profile as inferred from Gaia DR2

Cautun

Benítez-Llambay

Deason

et al. 2020

Monthly Notices of the Royal Astronomical Society

319

271

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We determine the Milky Way (MW) mass profile inferred from fitting physically motivated models to the Gaia DR2 Galactic rotation curve and other data. Using various hydrodynamical simulations of MW-mass haloes, we show that the presence of baryons induces a contraction of the dark matter (DM) distribution in the inner regions, r 20 kpc. We provide an analytic expression that relates the baryonic distribution to the change in the DM halo profile. For our galaxy, the contraction increases the enclosed DM halo mass by factors of roughly 1.3, 2 and 4 at radial distances of 20, 8 and 1 kpc, respectively compared to an uncontracted halo. Ignoring this contraction results in systematic biases in the inferred halo mass and concentration. We provide a best-fitting contracted NFW halo model to the MW rotation curve that matches the data very well. The best-fit has a DM halo mass, M DM 200 = 0.99 +0.18 −0.20 ×10 12 M , and concentration before baryon contraction of 8.2 +1.7 −1.5 , which lie close to the median halo mass-concentration relation predicted in ΛCDM. The inferred total mass, M total 200 = 1.12 +0.20 −0.22 × 10 12 M , is in good agreement with recent measurements. The model gives a MW stellar mass of 4.99 +0.34 −0.50 × 10 10 M , of which 60% is contained in the thin stellar disc, with a bulge-to-total ratio of 0.2. We infer that the DM density at the Solar position is ρ DM = 9.0 +0.5 −0.4 × 10 −3 M pc −3 ≡ 0.34 +0.02 −0.02 GeV cm −3 . The rotation curve data can also be fitted with an uncontracted NFW halo model, but with very different DM and stellar parameters. The observations prefer the physically motivated contracted NFW halo, but the measurement uncertainties are too large to rule out the uncontracted NFW halo.

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“…For 1 M stars, the velocity distribution is peaked at ∼ 200 km s −1 independently of the cluster orbit, while the velocity distribution is peaked at ∼ 200 km s −1 and ∼ 500 km s −1 for 4 M stars in the cases a cl = 5 kpc and a cl = 50 kpc, respectively. The dependence on stellar mass may be interpreted both in terms of the ejection velocities and in terms of the main-sequence lifetimes, computed as (Fragione & Loeb 2017) tms = m 1 M −2.5 10 10 yr .…”

Section: Ejecting Hypervelocity Stars From Star Clustersmentioning

confidence: 99%

Hypervelocity stars from star clusters hosting intermediate-mass black holes

Fragione

Gualandris

2019

Monthly Notices of the Royal Astronomical Society

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Hypervelocity stars (HVSs) represent a unique population of stars in the Galaxy reflecting properties of the whole Galactic potential, from the centre to the halo. Determining their origin is of fundamental importance to constrain the shape and mass of the dark halo. The leading scenario for the ejection of HVSs is an encounter with the supermassive black hole in the Galactic Centre (GC). However, new proper motions from the Gaia mission indicate that only the fastest HVSs can be traced back to the GC and the remaining stars originate in the disc or halo. In this paper, we study HVSs generated by encounters of stellar binaries with an intermediate-mass black hole (IMBH) in the core of a star cluster. We constrain the dependence of the spatial and velocity distribution of ejected stars on the binary mass, binary semi-major axis and IMBH mass. For the first time, we model the effect of the cluster orbit in the Galactic potential on the observable properties of the ejected population, which can contribute both to the Galactic runaway star and HVS populations. We show that HVSs generated by this mechanism do not travel on radial orbits consistent with a GC origin, but rather point back to the core of their parent cluster, thus providing observational evidence for the presence of an IMBH.

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Constraining the Milky Way mass with hypervelocity stars

Cited by 46 publications

References 54 publications

Constraining the mass of the Local Group

Constraining the mass of the Local Group

The milky way total mass profile as inferred from Gaia DR2

Hypervelocity stars from star clusters hosting intermediate-mass black holes

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