论文标题
银河地震学：射手座矮人影响后不断发展的“相螺旋”
Galactic seismology: the evolving "phase spiral" after the Sagittarius dwarf impact
论文作者
论文摘要
在2018年，ESA \ Gaia \卫星在整个太阳能社区的$ z-v_z $相位平面中发现了一个显着的螺旋模式（“相螺旋”），那里的$ z $和$ v_z $是垂直于银河盘的恒星的位移和速度。响应Binney \＆Schönrich的盘状卫星分析模型以解释\ Gaia \数据，我们进行了一个高分辨率的，N $ \：\：\：\：\ 10^8 $粒子）的脉冲质量（$ 2 \ times 10^times 10^{10} $ \ msun），与disce coods coods coilds相互作用。光盘响应很复杂，因为冲动会触发两个不同的双压（$ m = 2 $）模式$ - $ a密度波和瓦楞纸弯曲波$ - $ - 以不同速度结束的叠加。 {\ it更快}密度波和时间$ t $根据$ ϕ_d（r，t）=（ω_d（r） +ω_ {\ rm o}）\：t $其中$ ϕ_d $描述螺旋模式和$ω_d=ω（r）-cle频率，epcerd $ c的频率，虽然模式速度$ω_ {\ rm o} $很小，但它不是零。 {\ it慢}弯曲波根据$ω_b\ oft octing gounce_d/2 $产生波纹波。密度波的束效应在弯曲波上上下滚动时触发相位螺旋（“过山车”模型）。撞击后，相螺旋慢慢出现约$ΔT\约400美元。它似乎是一种长期寿命的圆度现象，在2个GYR模拟的大部分模拟中都继续发展。因此，鉴于射手座（SGR）（sgr）今天的低总质量（$ m _ {\ rm tot} \ sim 3 \ times 10^8 $ \ msun \在10 kpc直径内），我们相信阶段螺旋式的螺旋式激动了圆盘杂交矮人矮人矮人少数$ 1-2 $ gyr {\ IT}最近的过渡。为此，SGR必须在每个轨道循环时以0.5-1 DEX损失质量。
In 2018, the ESA \Gaia\ satellite discovered a remarkable spiral pattern ("phase spiral") in the $z-V_z$ phase plane throughout the solar neighbourhood, where $z$ and $V_z$ are the displacement and velocity of a star perpendicular to the Galactic disc. In response to Binney \& Schönrich's analytic model of a disc-crossing satellite to explain the \Gaia\ data, we carry out a high-resolution, N-body simulation (N$\:\approx 10^8$ particles) of an impulsive mass ($2\times 10^{10}$ \Msun) that interacts with a cold stellar disc at a single transit point. The disc response is complex since the impulse triggers a superposition of two distinct bisymmetric ($m=2$) modes $-$ a density wave and a corrugated bending wave $-$ that wrap up at different rates. Stars in the {\it faster} density wave wrap up with time $T$ according to $ϕ_D(R,T)=(Ω_D(R) + Ω_{\rm o})\:T$ where $ϕ_D$ describes the spiral pattern and $Ω_D =Ω(R) -κ(R)/2$, where $κ$ is the epicyclic frequency. While the pattern speed $Ω_{\rm o}$ is small, it is non-zero. The {\it slower} bending wave wraps up according to $Ω_B\approxΩ_D/2$ producing a corrugated wave. The bunching effect of the density wave triggers the phase spiral as it rolls up and down on the bending wave ("rollercoaster" model). The phase spiral emerges slowly about $ΔT \approx 400$ Myr after impact. It appears to be a long-lived, disc-wide phenomenon that continues to evolve over most of the 2~Gyr simulation. Thus, given Sagittarius' (Sgr) low total mass today ($M_{\rm tot}\sim 3\times 10^8$ \Msun\ within 10 kpc diameter), we believe the phase spiral was excited by the disc-crossing dwarf some $1-2$ Gyr {\it before} the recent transit. For this to be true, Sgr must be losing mass at 0.5-1 dex per orbit loop.
