Proper Motion of the Large Magellanic Cloud using [CLC]QSOs[/CLC] as an Inertial Reference System

Anguita, C.; Loyola, P.; Pedreros, Mario H.

doi:10.1086/301499

Cited by 28 publications

(30 citation statements)

References 12 publications

(9 reference statements)

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“…It is also worth noting that, if we fix the mass of the Galaxy equal to our most likely mass estimate, there is insufficient matter present to gravitationally bind the LMC, if we adopt the recent proper-motion measurement by Anguita et al (2000). These authors reported rather high proper motions, (µ α cos δ, µ δ ) = (+1.7 ± 0.2, +2.9 ± 0.2), compared to previous measurements, (µ α cos δ, µ δ ) = (+1.94 ± 0.29, −0.14 ± 0.36) (Kroupa & Bastian 1997).…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

The mass of the Milky Way: Limits from a newly assembled set of halo objects

Sakamoto

Chiba

Beers

2003

A&A

177

170

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Abstract. We set new limits on the mass of the Milky Way, making use of the latest kinematic information for Galactic satellites and halo objects. Our sample consists of 11 satellite galaxies, 137 globular clusters, and 413 field horizontal-branch (FHB) stars up to distances of 10 kpc from the Sun. Roughly half of the objects in this sample have measured proper motions, permitting the use of their full space motions in our analysis. In order to bind these sample objects to the Galaxy, their rest-frame velocities must be lower than their escape velocities at their estimated distances. This constraint enables us to show that the mass estimate of the Galaxy is largely affected by several high-velocity objects (Leo I, Pal 3, Draco, and a few FHB stars), not by a single object alone (such as Leo I), as has often been the case in past analyses. We also find that a gravitational potential that gives rise to a declining rotation curve is insufficient to bind many of our sample objects to the Galaxy; a possible lower limit on the mass of the Galaxy is about 2.2 × 10 12 M . To be more quantitative, we adopt a Bayesian likelihood approach to reproduce the observed distribution of the current positions and motions of the sample, in a prescribed Galactic potential that yields a flat rotation curve. This method enables a search for the most likely total mass of the Galaxy, without undue influence in the final result arising from the presence or absence of Leo I, provided that both radial velocities and proper motions are used. Although the best mass estimate depends somewhat on the model assumptions, such as the unknown prior probabilities for the model parameters, the resultant systematic change in the mass estimate is confined to a relatively narrow range of a few times 10 11 M , owing to our consideration of many FHB stars. The most likely total mass derived from this method is 2.5 11 M (excluding Leo I). Implications for the origin of halo microlensing events (e.g., the possibility of brown dwarfs as the origin of the microlensing events toward the LMC, may be excluded by our lower mass limit) and prospects for more accurate estimates of the total mass are also discussed.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

The mass of the Milky Way: Limits from a newly assembled set of halo objects

Sakamoto

Chiba

Beers

2003

A&A

177

170

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“…In addition, two QSOs used by Anguita et al (2000) and one by Pedreros et al (2002) to study the proper motion of the LMC are attributed to a private communication by Maza in 1989 and/or do not appear in previous studies. More recently, 1 QSO was confirmed by Hony et al (2011) and 145 QSOs by Kozłowski et al (2012), the latter identified from OGLE-III light-curves.…”

Section: Appendix A: Known Qsos Behind the Magellanic Systemmentioning

confidence: 99%

The VMC Survey

Cioni¹,

Kamath²,

Rubele³

et al. 2012

A&A

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Context. The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects for different types of studies. Aims. We have searched for criteria to identify candidate QSOs using observations from the VISTA survey of the Magellanic Clouds system (VMC) that provides photometry in the Y JK s bands and 12 epochs in the K s band. Methods. The (Y − J) versus (J − K s ) diagram has been used to distinguish QSO candidates from Milky Way stars and stars of the Magellanic Clouds. Then, the slope of variation in the K s band has been used to identify a sample of high confidence candidates. These criteria were developed based on the properties of 117 known QSOs presently observed by the VMC survey. Results. VMC Y JK s magnitudes and K s light-curves of known QSOs behind the Magellanic system are presented. About 75% of them show a slope of variation in K s > 10 −4 mag/day and the shape of the light-curve is in general irregular and without any clear periodicity. The number of QSO candidates found in tiles including the south ecliptic pole and the 30 Doradus regions is 22 and 26, respectively, with a ∼20% contamination by young stellar objects, planetary nebulae, stars and normal galaxies. Conclusions. By extrapolating the number of QSO candidates to the entire VMC survey area we expect to find about 1200 QSOs behind the LMC, 400 behind the SMC, 200 behind the Bridge and 30 behind the Stream areas, but not all will be suitable for astrometry. Further, the K s band light-curves can help support investigations of the mechanism responsible for the variations.

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“…In alphabetical order, the list now contains Draco (Scholtz & Irwin 1993), Canis Major (Dinescu et al 2005b), Carina (Piatek et al 2003), Fornax (Piatek et al 2002;Dinescu et al 2004), the LMC (Jones et al 1994;Kroupa et al 1994;Kroupa & Bastian 1997;Anguita et al 2000;Drake et al 2001;Pedreros et al 2002;Kallivayalil et al 2006b), M33 ( Brunthaler et al 2005), Sagittarius ( Dinescu et al 2005a), Sculptor (Schweitzer et al 1995;Piatek et al 2006), the SMC (Irwin et al 1996;Kallivayalil et al 2006a), and Ursa Minor (Scholtz & Irwin 1993;Schweitzer et al 1997;Piatek et al 2005). This sample is becoming large enough to reveal the three-dimensional nature of motions in the Local Group.…”

Section: Introductionmentioning

confidence: 99%

Proper Motions of Dwarf Spheroidal Galaxies fromHubble Space TelescopeImaging. V. Final Measurement for Fornax

Piatek¹,

Pryor²,

Bristow³

et al. 2007

100

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The measured proper motion of Fornax, expressed in the equatorial coordinate system, is ( ; ) ¼ (47:6 AE 4:6; À36:0 AE 4:1) mas century À1 . This proper motion is a weighted mean of four independent measurements for three distinct fields. Each measurement uses a quasi-stellar object as a reference point. Removing the contribution of the motion of the Sun and of the local standard of rest to the measured proper motion produces a Galactic restframe proper motion of ( Grf ; Grf ) ¼ (24:4 AE 4:6; À14:3 AE 4:1) mas century À1 . The implied space velocity with respect to the Galactic center has a radial component of V r ¼ À31:8 AE 1:7 km s À1 and a tangential component of V t ¼ 196 AE 29 km s À1 . Integrating the motion of Fornax in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 118 (66, 137) and 152 (144, 242) kpc, respectively, where the values in the parentheses represent the 95% confidence intervals derived from Monte Carlo experiments. The eccentricity of the orbit is 0.13 (0.11, 0.38), and the orbital period is 3.2 (2.5, 4.6) Gyr. The orbit is retrograde and inclined by 101 (94 , 107 ) to the Galactic plane. Fornax could be a member of a proposed ''stream'' of galaxies and globular clusters; however, the membership of another proposed galaxy in the stream, Sculptor, has been previously ruled out. Fornax is in the Kroupa-Theis-Boily plane, which contains 11 of the Galactic satellite galaxies, but its orbit will take it out of that plane.

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Proper Motion of the Large Magellanic Cloud using [CLC]QSOs[/CLC] as an Inertial Reference System

Cited by 28 publications

References 12 publications

The mass of the Milky Way: Limits from a newly assembled set of halo objects

The mass of the Milky Way: Limits from a newly assembled set of halo objects

The VMC Survey

Proper Motions of Dwarf Spheroidal Galaxies fromHubble Space TelescopeImaging. V. Final Measurement for Fornax

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