Constraints on the Galactic Centre environment from Gaia hypervelocity stars. (arXiv:2110.06813v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Evans_F/0/1/0/all/0/1">F. A. Evans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marchetti_T/0/1/0/all/0/1">T. Marchetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rossi_E/0/1/0/all/0/1">E. M. Rossi</a>

Following a dynamical encounter with Sgr A*, binaries in the Galactic Centre
(GC) can be tidally separated and one member star ejected as a hyper-velocity
star (HVS) with a velocity beyond the escape speed of the Milky Way. As GC-born
objects located in more observationally accessible regions of the sky, HVSs
offer insight into the stellar population in the inner parsecs of the Milky
Way. We perform a suite of simulations ejecting HVSs from the GC, exploring how
detectable HVS populations depend on assumptions concerning the GC stellar
population, focusing on those that are both gravitationally unbound from the
Galaxy and which would appear in current and/or future data releases from the
textit{Gaia} space mission with precise astrometry and measured radial
velocities. We show that predictions are sensitive to two parameters in
particular: the shape of the stellar initial mass function (IMF) in the GC and
the ejection rate of HVSs. The absence of confident HVS candidates in
textit{Gaia} Data Release 2 excludes scenarios in which the HVS ejection rate
is $gtrsim3times10^{-2} , mathrm{yr^{-1}}$. Stricter constraints will be
placed on these parameters when more HVS candidates are unearthed in future
textit{Gaia} data releases — assuming recent determinations of the GC IMF
shape, one confident HVS textit{at minimum} is expected in textit{Gaia} DR3
and DR4 as long as the HVS ejection rate is greater than $sim 10^{-3} ,
mathrm{yr^{-1}}$ and $sim10^{-5} , mathrm{yr^{-1}}$, respectively.

Following a dynamical encounter with Sgr A*, binaries in the Galactic Centre
(GC) can be tidally separated and one member star ejected as a hyper-velocity
star (HVS) with a velocity beyond the escape speed of the Milky Way. As GC-born
objects located in more observationally accessible regions of the sky, HVSs
offer insight into the stellar population in the inner parsecs of the Milky
Way. We perform a suite of simulations ejecting HVSs from the GC, exploring how
detectable HVS populations depend on assumptions concerning the GC stellar
population, focusing on those that are both gravitationally unbound from the
Galaxy and which would appear in current and/or future data releases from the
textit{Gaia} space mission with precise astrometry and measured radial
velocities. We show that predictions are sensitive to two parameters in
particular: the shape of the stellar initial mass function (IMF) in the GC and
the ejection rate of HVSs. The absence of confident HVS candidates in
textit{Gaia} Data Release 2 excludes scenarios in which the HVS ejection rate
is $gtrsim3times10^{-2} , mathrm{yr^{-1}}$. Stricter constraints will be
placed on these parameters when more HVS candidates are unearthed in future
textit{Gaia} data releases — assuming recent determinations of the GC IMF
shape, one confident HVS textit{at minimum} is expected in textit{Gaia} DR3
and DR4 as long as the HVS ejection rate is greater than $sim 10^{-3} ,
mathrm{yr^{-1}}$ and $sim10^{-5} , mathrm{yr^{-1}}$, respectively.

http://arxiv.org/icons/sfx.gif

Comments are closed, but trackbacks and pingbacks are open.