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Article: Constraints on the Galactic bar from the Hercules stream as traced with RAVE across the Galaxy â&dagger
Title  Constraints on the Galactic bar from the Hercules stream as traced with RAVE across the Galaxy â&dagger 

Authors  Antoja, TeresaHelmi, AminaDehnen, WalterBienaymé, OlivierBlandHawthorn, Joss BlandFamaey, BenoîtFreeman, Kenneth C.Gibson, Brad K.Gilmore, Gerard F.Grebel, Eva K.Kordopatis, GeorgesKunder, Andrea M.Minchev, IvanMunari, UlisseNavarro, Julio F.Parker, Quentin A.Reid, Warren A.Seabroke, George M.Siebert, ArnaudSteinmetz, MatthiasWatson, Fred G.Wyse, Rosemary F GZwitter, Tomaž 
Keywords  Galaxy: structure Galaxy: disk Galaxy: evolution Galaxy: kinematics and dynamics 
Issue Date  2014 
Citation  Astronomy and Astrophysics, 2014, v. 563 How to Cite? 
Abstract  Nonaxisymmetries in the Galactic potential (spiral arms and bar) induce kinematic groups such as the Hercules stream. Assuming that Hercules is caused by the effects of the outer Lindblad resonance of the Galactic bar, we model analytically its properties as a function of position in the Galaxy and its dependence on the bar's pattern speed and orientation. Using data from the RAVE survey we find that the azimuthal velocity of the Hercules structure decreases as a function of Galactocentric radius, in a manner consistent with our analytical model. This allows us to obtain new estimates of the parameters of the Milky Way's bar. The combined likelihood function of the bar's pattern speed and angle has its maximum for a pattern speed of Ωb = (1.89 ± 0.08) × Ω0, where Ω0 is the local circular frequency. Assuming a solar radius of 8.05 kpc and a local circular velocity of 238 km s1, this corresponds to Ωb = 56 ± 2 km s1 kpc1. On the other hand, the bar's orientation φb cannot be constrained with the available data. In fact, the likelihood function shows that a tight correlation exists between the pattern speed and the orientation, implying that a better description of our best fit results is given by the linear relation Ωb/Ω0 = 1.91 + 0.0044(φb(deg) 48), with standard deviation of 0.02. For example, for an angle of φb = 30 deg the pattern speed is 54.0 ± 0.5 km s 1 kpc1. These results are not very sensitive to the other Galactic parameters such as the circular velocity curve or the peculiar motion of the Sun, and are robust to biases in distance. © 2014 ESO. 
Persistent Identifier  http://hdl.handle.net/10722/209025 
ISSN  2014 Impact Factor: 4.378 2015 SCImago Journal Rankings: 2.446 
DC Field  Value  Language 

dc.contributor.author  Antoja, Teresa   
dc.contributor.author  Helmi, Amina   
dc.contributor.author  Dehnen, Walter   
dc.contributor.author  Bienaymé, Olivier   
dc.contributor.author  BlandHawthorn, Joss Bland   
dc.contributor.author  Famaey, Benoît   
dc.contributor.author  Freeman, Kenneth C.   
dc.contributor.author  Gibson, Brad K.   
dc.contributor.author  Gilmore, Gerard F.   
dc.contributor.author  Grebel, Eva K.   
dc.contributor.author  Kordopatis, Georges   
dc.contributor.author  Kunder, Andrea M.   
dc.contributor.author  Minchev, Ivan   
dc.contributor.author  Munari, Ulisse   
dc.contributor.author  Navarro, Julio F.   
dc.contributor.author  Parker, Quentin A.   
dc.contributor.author  Reid, Warren A.   
dc.contributor.author  Seabroke, George M.   
dc.contributor.author  Siebert, Arnaud   
dc.contributor.author  Steinmetz, Matthias   
dc.contributor.author  Watson, Fred G.   
dc.contributor.author  Wyse, Rosemary F G   
dc.contributor.author  Zwitter, Tomaž   
dc.date.accessioned  20150323T02:31:12Z   
dc.date.available  20150323T02:31:12Z   
dc.date.issued  2014   
dc.identifier.citation  Astronomy and Astrophysics, 2014, v. 563   
dc.identifier.issn  00046361   
dc.identifier.uri  http://hdl.handle.net/10722/209025   
dc.description.abstract  Nonaxisymmetries in the Galactic potential (spiral arms and bar) induce kinematic groups such as the Hercules stream. Assuming that Hercules is caused by the effects of the outer Lindblad resonance of the Galactic bar, we model analytically its properties as a function of position in the Galaxy and its dependence on the bar's pattern speed and orientation. Using data from the RAVE survey we find that the azimuthal velocity of the Hercules structure decreases as a function of Galactocentric radius, in a manner consistent with our analytical model. This allows us to obtain new estimates of the parameters of the Milky Way's bar. The combined likelihood function of the bar's pattern speed and angle has its maximum for a pattern speed of Ωb = (1.89 ± 0.08) × Ω0, where Ω0 is the local circular frequency. Assuming a solar radius of 8.05 kpc and a local circular velocity of 238 km s1, this corresponds to Ωb = 56 ± 2 km s1 kpc1. On the other hand, the bar's orientation φb cannot be constrained with the available data. In fact, the likelihood function shows that a tight correlation exists between the pattern speed and the orientation, implying that a better description of our best fit results is given by the linear relation Ωb/Ω0 = 1.91 + 0.0044(φb(deg) 48), with standard deviation of 0.02. For example, for an angle of φb = 30 deg the pattern speed is 54.0 ± 0.5 km s 1 kpc1. These results are not very sensitive to the other Galactic parameters such as the circular velocity curve or the peculiar motion of the Sun, and are robust to biases in distance. © 2014 ESO.   
dc.language  eng   
dc.relation.ispartof  Astronomy and Astrophysics   
dc.subject  Galaxy: structure   
dc.subject  Galaxy: disk   
dc.subject  Galaxy: evolution   
dc.subject  Galaxy: kinematics and dynamics   
dc.title  Constraints on the Galactic bar from the Hercules stream as traced with RAVE across the Galaxy â&dagger   
dc.type  Article   
dc.description.nature  link_to_subscribed_fulltext   
dc.identifier.doi  10.1051/00046361/201322623   
dc.identifier.scopus  eid_2s2.084896796123   
dc.identifier.volume  563   
dc.identifier.eissn  14320746   