Tycho-Gaia Astrometric Solution Parallaxes and Proper Motions for Five Galactic Globular Clusters

Watkins, Laura L.; Marel, Roeland P. van der

doi:10.3847/1538-4357/aa696f

Cited by 25 publications

(25 citation statements)

References 77 publications

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“…This is of the order of one-fifth of an AL/AC-average pixel and in addition this offset would have to be consistent for the different scan angles, which seems rather unlikely. In this context we also note that very good agreement is found between proper motions derived from the HST and TGAS for the Magellanic Clouds (vdMS) and Globular Clusters in the Milky Way (Watkins & van der Marel 2017). We conclude that Sk-67 2 is a candidate hypervelocity star that if confirmed, by for example Gaia Data Release 2 (DR2), would warrant further investigation as to the nature of its origin.…”

Section: Sk-67 2 (=Hde 270754 =Hip 22237)supporting

confidence: 55%

Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars

Lennon

Marel

Lerate

et al. 2017

A&A

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Aims. Our research aims to search for runaway stars in the Large Magellanic Cloud (LMC) among the bright Hipparcos supergiant stars included in the Gaia DR1 Tycho-Gaia astrometric solution (TGAS) catalogue. Methods. We compute the space velocities of the visually brightest stars in the Large Magellanic Cloud that are included in the TGAS proper motion catalogue. This sample of 31 stars contains a luminous blue variable (LBV), emission line stars, blue and yellow supergiants, and an SgB[e] star. We combine these results with published radial velocities to derive their space velocities, and by comparing with predictions from stellar dynamical models we obtain each star's (peculiar) velocity relative to its local stellar environment. Results. Two of the 31 stars have unusually high proper motions. Of the remaining 29 stars we find that most objects in this sample have velocities that are inconsistent with a runaway nature, being in very good agreement with model predictions of a circularly rotating disk model. Indeed the excellent fit to the model implies that the TGAS uncertainty estimates are likely overestimated. The fastest outliers in this subsample contain the LBV R 71 and a few other well known emission line objects though in no case do we derive velocities consistent with fast (∼100 km s −1) runaways. On the contrary our results imply that R 71 in particular has a moderate deviation from the local stellar velocity field (40 km s −1) lending support to the proposition that this object cannot have evolved as a normal single star since it lies too far from massive star forming complexes to have arrived at its current position during its lifetime. Our findings therefore strengthen the case for this LBV being the result of binary evolution. Of the two stars with unusually high proper motions we find that one, the isolated B1.5 Ia + supergiant Sk-67 2 (HIP 22237), is a candidate hypervelocity star, the TGAS proper motion implying a very large peculiar transverse velocity (∼360 km s −1) directed radially away from the LMC centre. If confirmed, for example by Gaia Data Release 2, it would imply that this massive supergiant, on the periphery of the LMC, is leaving the galaxy where it will explode as a supernova.

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Section: Sk-67 2 (=Hde 270754 =Hip 22237)supporting

confidence: 55%

Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars

Lennon

Marel

Lerate

et al. 2017

A&A

Self Cite

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“…Dinescu et al (1999) listed eight GGCs (NGC 288,5139,6121,6144,6362,6712,6769 and Pal 5) with similar dynamics supporting the existence of tidal tails; only Pal 5 having been confirmed. According to recent works, NGC 5139 (Fernández-Trincado et al 2015), NGC 6121 (Watkins & van der Marel 2017), NGC 4166, 6362, 6712 and 6779 (Chen & Chen 2010) do not show evidence of tidal tails. NGC 288, studied here, must now be included in this list, since the present outcomes suggest that Galactic tidal interaction has been a relatively inefficient process for stripping stars off the cluster.…”

Section: Analysis and Discussionmentioning

confidence: 87%

On the extended stellar structure around NGC 288

Piatti

2017

Monthly Notices of the Royal Astronomical Society

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We report on observational evidence of an extra-tidal clumpy structure around NGC 288 from an homogeneous coverage of a large area with the Pan-STARRS PS1 database. The extra-tidal star population has been disentangled from that of the Milky Way field by using a cleaning technique that successfully reproduced the stellar density, luminosity function and colour distributions of MW field stars. We have produced the cluster stellar density radial profile and a stellar density map from independent approaches, from which we found results in excellent agreement : the feature extends up to 3.5 times the cluster tidal radius. Previous works based on shallower photometric data sets have speculated on the existence of several long tidal tails, similar to that found in Pal 5. The present outcome shows that NGC 288 could hardly have such tails, but favours the notion that interactions with the MW tidal field has been a relatively inefficient process for stripping stars off the cluster. These results point to the need of a renewed overall study of the external regions of Galactic globular clusters (GGCs) in order to reliably characterise them. Hence, it will be possible to investigate whether there is any connection between detected tidal tails, extra-tidal stellar populations, extent diffuse halo-like structures with the GGCs' dynamical histories in the Galaxy.

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“…This is then used to compute possible orbits in a realistic Galactic mass distribution. An analysis that is similar in spirit has been performed on five nearby globular clusters by Watkins & van der Marel (2016) who exploited the Tycho-Gaia solution (TGAS, see Lindegren et al 2016) rather than using HST. However, since TGAS PMs are available only for bright stars, no such measurements exist for NGC 2419 members.…”

Section: Introductionmentioning

confidence: 99%

The power of teaming up HST andGaia: the first proper motion measurement of the distant cluster NGC 2419

Massari

Posti

Helmi

et al. 2017

A&A

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Aims. We present the first measurement of the proper motion and orbit of the very distant and intriguing globular cluster NCG 2419. Methods. We have combined data from HST and Gaia DR1 to derive the relative proper motions of stars in the direction of the cluster. To tie these to an absolute reference frame, we have used a background galaxy located in the field. Results. We find the absolute proper motion of NGC 2419 to be (µ α cos(δ), µ δ ) = (−0.17 ± 0.26, −0.49 ± 0.17) mas yr −1 . We have integrated the orbit of the cluster in a Galactic potential and found it to oscillate between ∼53 kpc and ∼98 kpc on an almost polar orbit. This, and the fact that it shares the same sense of rotation around the Milky Way, make it very likely that NGC 2419 is a former cluster of the Sagittarius dwarf spheroidal galaxy.

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Tycho-Gaia Astrometric Solution Parallaxes and Proper Motions for Five Galactic Globular Clusters

Cited by 25 publications

References 77 publications

Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars

Gaia TGAS search for Large Magellanic Cloud runaway supergiant stars

On the extended stellar structure around NGC 288

The power of teaming up HST andGaia: the first proper motion measurement of the distant cluster NGC 2419

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