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There are two spectacular structures in our Milky Way: the {it Fermi} bubbles in gamma-ray observations and the North Polar Spur (NPS) structure in X-ray observations. Because of their morphological similarities, they may share the same origin, i.e., related to the past activity of Galactic center (GC). Besides, those structures show significant bending feature toward the west in Galactic coordinates. This inspires us to consider the possibility that the bending may be caused by a presumed global horizontal galactic wind (HGW) blowing from the east to the west. Under this assumption, we adopt a toy shock expansion model to understand two observational features: (1) the relative thickness of the NPS; (2) the bending of the {it Fermi} bubbles and NPS. In this model, the contact discontinuity (CD) marks the boundary of the {it Fermi} bubbles, and the shocked interstellar medium (ISM) marks the NPS X-ray structure. We find that the Mach number of the forward shock in the east is $sim$ 1.9-2.3, and the velocity of the HGW is ~ 0.7-0.9 $c_{s}$. Depending on the temperature of the pre-shock ISM, the velocity of the expanding NPS in Galactic coordinates is around 180-290 km/s, and the HGW is ~ 110-190 km/s. We argue that, the age of the NPS and the {it Fermi} bubbles is about 18-34 Myr. This is a novel method, independent of injection theories and radiative mechanisms, for the estimation on the age of the {it Fermi} bubble/NPS.
Using hydrodynamical simulations, we show for the first time that an episode of star formation in the center of the Milky Way, with a star-formation-rate (SFR) $sim 0.5$ M$_odot$ yr$^{-1}$ for $sim 30$ Myr, can produce bubbles that resemble the Fermi
Initial results are presented from 3D MHD modelling of stellar-wind bubbles around O stars moving supersonically through the ISM. We describe algorithm updates that enable high-resolution 3D MHD simulations at reasonable computational cost. We apply
We investigate roles of magnetic activity in the Galactic bulge region in driving large-scale outflows of size $sim 10$ kpc. Magnetic buoyancy and breakups of channel flows formed by magnetorotational instability excite Poynting flux by the magnetic
Fermi LAT has discovered two extended gamma-ray bubbles above and below the galactic plane. We propose that their origin is due to the energy release in the Galactic center (GC) as a result of quasi-periodic star accretion onto the central black hole
Two giant plasma lobes, known as the Fermi Bubbles, extend 10 kpc above and below the Galactic Center. Since their discovery in X-rays in 2003 (and in gamma-rays in 2010), the Bubbles have been recognized as a new morphological feature of our Galaxy