Galaxy inner

Fig. 3. Scuba map of the inner Galaxy the central regions of old spheroids host the majority reservoir of molecular gas for current and future star formation. This figure is from Pierce-Price et al. 2000.

Fig. 3.31. X-ray spectrum taken from the XMM-Newton and Chandra X-ray observatories of the inner part of the Centaurus cluster of galaxies, where the metallicity is roughly twice solar, showing the iron L- and K-shell features at energies of 1.2 and 6.8 keV repectively. The curve is a two-component fit to the continuum with temperatures of 0.7 and 1.5 keV. After Sanders and Fabian (2006). Courtesy Andy Fabian.

Fig. 8.17. Age-metallicity relation for disk stars using data from Edvardsson et al. (1993). Open circles, filled circles and crosses represent respectively stars with mean Galactocentric distances 7 to 9 kpc (like the Sun), stars from the inner Galaxy (under 7 kpc) and from the outer Galaxy (over 9 kpc). Model curves assume linear star-formation laws with

Figure 3.9. Left (1) Bright end of the Coma GLF we clearly see the bump at bright magnitudes and the whole just after. This is interpreted as the accretion or the merging of moderatly faint galaxies in order to form brighter galaxies (Lobo et al. 1997). (2) Right solid line Coma inner core GLF, short dashed line Global Coma GLF we clearly see the cut-off with magnitude in the Coma cluster inner core.

Figure 5.1. Left. The DM density profile in the inner parts of the galaxy NGC 6822 does not reveal a density cusp (Weldrake et al. 2003). The case of NGC2976 confirms that r] = 0.27 at r < 1.8 Kpc (Simon et al. 2003). Right. The total gravitating mass (open circles) in the cluster A2029 (see the recent review by Buote 2003) overlaid with different models NFW (solid), power-law (dashed) and Moore et al. (dotted). The gas mass (triangles) is also shown for comparison.

Observations of galaxy duster do not help in this respect since the available data stop our understanding of the DM density profile at distances r 10 kpc from their centres (see Fig.5.1). Down to these scales the NFW is still allowed and at smaller scales the inner slope remains quite uncertain even when the combined analysis of X-ray, gravitational lensing and galaxy dynamics data are taken into account (Dalai Keeton 2003). 

The implication of Eq. 17 is that for E1 70 MeV the diffuse gamma-ray spectrum should have the same power law behavior as the proton spectrum, a ss 2.7. What is observed, however, is that the spectrum of gamma-rays from the inner galaxy is harder than this, having a power-law behavior of approximately E 2A (Hunter et al., 1997). This is currently not fully understood. One possibility is that the cosmic-ray spectrum producing the gamma rays is harder than observed locally near Earth (Hunter et al., 1997). 

Three of six early-type galaxies observed exhibit dust emission that is organized into spiral arm or inner disk-like structures,... 

How early could someone have compiled the sort of M/L trends reported in (3) and (4) and shown in Table 1 In principle, shortly before the outbreak of World War II, using the work of Jeans and Kapteyn, or Oort a decade later for the solar neighborhood, Hubble s 1934 discussion of the inner parts of galaxies (16), a rotation curve for the outer parts of M31 that formed part of the PhD dissertation of the late Horace W. Babcock (17), the binary galaxies presented by Holmberg in 1937 (18), also part of his PhD dissertation, and a 1936 study of the Virgo cluster by Sinclair Smith (19), in case you happened not to like Fritz Zwicky, as indeed some of his contemporaries did not. 

Figure 4. Latitude and Longitude for the inner galaxy as seen from Milagro.

The disk of the Galaxy formed mostly by infall of primordial or very metal poor gas accumulating faster in the inner than in the outer regions (inside-out scenario, i.e. td(R) decreases with decreasing R). 

Inside-out formation of the Galaxy is suggested also by the fact that the globular clusters of the inner halo are coeval (At 0.5 Gyr, Rosenberg et al. 1999), whereas the age difference seems to increase in the outer halo. 

Let us now have a physical point of view. In our galaxy a majority of stars are binary stars. If then a weak binary star meets a strong binary star, an ordinary motion of exchange type can easily disrupt the weak binary and lead to the formation of a triple system with the strong binary. That new-born triple system has generally a Hill-type stability and if its motion is of the second oscillating type (which usually requires a large inclination) it will lead to a collision of the two stars of the binary... The probability of this phenomenon is of the order of the ratio of the inner period (that of the close binary) to the outer period (that of the third body). 

---