Symmetry And Group

The galaxies of the local group by Sidney van den Bergh

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By Sidney van den Bergh

The neighborhood workforce is a small cluster of galaxies of which thirty-five individuals are presently identified, together with the Milky approach. With attribute readability of expression, Sidney van den Bergh offers a whole evaluation of all that's recognized concerning the galaxies of the neighborhood team and their evolution. He additionally locations this data within the wider context of continuous reports of galaxy formation and evolution, the cosmic distance scale, and the stipulations within the early Universe. This quantity completely info our present realizing of every of the thirty-five participants of the neighborhood staff, in addition to these galaxies formerly considered as attainable individuals. The publication is going directly to research the mass, balance and evolution of the neighborhood staff as an entire and comprises many vital, formerly unpublished effects and conclusions.

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P1: MRM CB240-03 November 20, 1999 24 12:55 Char Count= 0 The Andromeda galaxy (M31) Neininger et al. (1998) have used carbon monoxide emission to trace the spiral arms in the Andromeda galaxy. They find a tight correlation between CO emission and dust extinction, from which they conclude that CO traces the molecular gas. Because so much gas is in molecular form, they find a poor correlation between I(CO) and I(HI). However, a tight correlation is found between I(CO) and I(HI) + 2N (H2 ). From color diagrams obtained with the IRAS satellite Xu & Helou (1994) conclude that very small grains (but not polycyclic aromatic hydrocarbons) are only half as abundant in M31 as they are in high-latitude Galactic “cirrus” clouds.

Furthermore, the NH feature at λ 3360 in M31 globulars is greatly enhanced relative to its strength in Galactic globulars. This shows that the M31 globulars must be overabundant in nitrogen. ) A detailed discussion of the differences among the spectra of the M31 halo, disk, and bulge is given by Worthey (1998). He concludes that the nucleosynthetic history of the Andromeda galaxy must have been quite different from that of the Milky Way system: (1) M31 has substantially more N in its center, and (2) the metal-rich globulars in M31 have scaled-solar Fe, Mg, and Na but are significantly enhanced in N.

1999) have used the Hubble Space Telescope to study the absorption silhouette of the remnant of S And in the H&K lines of calcium. 3 pc. From the decrease of the intensity of M31 bulge light in the remnant Fesen et al. find that it lies ∼64 pc in front of the midpoint of the bulge. The spectrum of this remnant yields an average expansion velocity of ˚ 11,000 ± 2,000 km s−1 . Puzzlingly the center of the Ca I absorption feature at 4,227 A appears to be redshifted by 1,100 km s−1 . The remnants of supernovae exhibit larger [S II]/Hα line intensity ratios than do H II regions.

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