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arXiv 2109.08439astro-ph.HEastro-ph.GA
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银河系毫秒脉冲星群:银河系中心过剩的意义

The Galactic Millisecond Pulsar Population: Implications for the Galactic Center Excess

Harrison Ploeg

摘要:

银河系中心过剩(Galactic Center Excess,GCE)是费米大天区望远镜(Fermi Large Area Telescope)数据中发现的银河系中心区域的扩展伽马射线源。近年来,人们已经清楚地看到,GCE可能不是球对称的,但可能与银河系隆起中恒星质量的分布在空间上相关,这可能有利于未解决的毫秒双星(MSP)的情况。在这篇论文中,我们对银河系MSP人口进行了详细的建模。在我们的模型中包括形成和观测之间的自旋下降,我们发现一个模型,其中光度$L \propto E_{\rm cut}^{1.2 \pm 0.3} B^{0.1 \pm 0.4} \dot{E}^{0.5 \pm 0.1}$提供了最好的拟合数据,其中$E_{\rm cut}$是光谱能量截止,$B$是磁场强度,和$\dot{E}$是自旋下降的功率。由于不同的恒星形成历史,预计银河系球核中的MSP比银河系盘中的MSP更古老,因此更暗。我们的研究结果表明,我们不需要有什么系统的不同,内部星系MSP解释GCE。在MSP形成的“再循环”通道中,中子星是从一个核心坍缩超新星形成的,由于爆炸的不对称性,超新星经历了一个随机的“踢”。这将意味着平滑MSP的空间分布。我们使用N体模拟来模拟MSP空间分布的变化。我们估计出生踢速度的概率分布,使用解决伽马射线MSP自行,其中MSP有速度相对于圆周运动的77 +/- 6公里/秒,作为我们的银河系MSP人口模型的一部分确定。我们发现,由于出生踢,有一个大约10%的增加,在每个凸起MSP空间分布尺寸和凸起MSP分布变得不那么四四方方的,但仍然是远离球形。

英文摘要:

The Galactic Center Excess (GCE) is an extended gamma-ray source in the central region of the Galaxy found in Fermi Large Area Telescope data. In recent years it has become apparent that the GCE may not be spherically symmetric, but may be spatially correlated with the distribution of stellar mass in the Galactic bulge, potentially favoring an unresolved population of millisecond pulsars (MSPs) scenario. In this thesis, we perform detailed modelling of the Galactic MSP population. Including in our model the spin down between formation and observation, we find a model in which luminosity $L \propto E_{\rm cut}^{1.2 \pm 0.3} B^{0.1 \pm 0.4} \dot{E}^{0.5 \pm 0.1}$ provides the best fit to the data, where $E_{\rm cut}$ is spectral energy cutoff, $B$ is magnetic field strength, and $\dot{E}$ is the spin-down power. Due to differing star formation histories it is expected that the MSPs in the Galactic bulge are older and therefore dimmer than those in the Galactic disk. Our results demonstrate that we do not require that there is anything systematically different about the inner Galaxy MSPs to explain the GCE. In the "recycling" channel of MSP formation the neutron star forms from a core collapse supernovae that undergoes a random "kick" due to the asymmetry of the explosion. This would imply a smoothing out of the spatial distribution of the MSPs. We use N-body simulations to model how the MSP spatial distribution changes. We estimate the probability distribution of natal kick velocities using the resolved gamma-ray MSP proper motions, where MSPs have velocities relative to circular motion of 77 +/- 6 km/s, as determined as part of our Galactic MSP population model. We find that, due to the natal kicks, there is an approximately 10% increase in each of the bulge MSP spatial distribution dimensions and also the bulge MSP distribution becomes less boxy but is still far from being spherical.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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