Galaxies satellite

Based on currently available elemental abundance data and age determinations, the thick disk could have formed either through a violent, heating merger or through accretion of (substantial) satellites in a hierarchical galaxy formation scenario. The fast monolithic-like collapse is getting more and more problematic as data are gathered. It would be especially crucial to establish if there is an age-metallicity relation in the thick disk or not as in that case the thick disk could not have formed in that way (since the models indicate that the formation time-scale for the stars in the thick disk would be very short, see [7]). 

Monaco L., 2004 in Chemical Abundances and Mixing in Stars in the Milky Way Galaxy and its Satellites, L. Pasquini S. Randich eds., Springer-Verlag, Berlin, P-... 

The halo globular cluster system also provides valuable information, since accurate distances, and hence reliable ages, can be derived. Mackey Gilmore (2004) recently acquired and compiled a new, nearly complete, internally consistent set of photometric studies of the globular cluster population in both the Milky Way and its satellite galaxies they deduce, from analysis of HB morphol-ogy, age, abundance and structural information, somewhat more relaxed limits... 

Chemical Connections Between Stars in the Galaxy and its Satellites... 

Detailed elemental abundances are now available for several individual stars in the Galaxy s dwarf satellites (Shetrone et a1. 2001, 2003 Geisler et al. 2005 also see the reviews in this proceedings). A comparison of these abundance ratios to those of stars in the Galaxy can be used to address several questions related to galaxy formation and evolution, as well as stellar nucleosynthesis. 

The accretion history of a parent galaxy is constructed using a semi-analytical code. The full phase-space evolution during each accretion event is then followed separately with numerical simulations [2]. Star-formation and chemical evolution models are implemented within each satellite. The star formation prescription matches the number and luminosity of present-day galaxies in the Local Group, whereas the chemical evolution model takes into account the metal enrichment of successive stellar populations as well as feedback processes. Below we present results of a sample of four such simulated galaxy halos, denoted as Halos HI, H2, H3 and H4. 

Future work [7] will include a modeling of phase-space variations of a elements in galaxy halos and their satellites, using the chemical enrichment code of [10]. 

Adding to this general context the fact that the FLAMES facility at the VLT was offered to the community one year earlier, and that it was starting to produce an impressive wealth of abundance data of stars in the Galaxy and in our neighborhoods, the broad concept of the ESO-Arcetri workshop on Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites was built. 

The IRAS satellite mission, launched in 1983, provided a more complete survey of disk and active galaxies containing dust than had been possible from optical observations. Follow-up measurements of redshifts and other properties led to significant results for cosmology and the discovery of many luminous star-forming and active galaxies enshrouded by dust. A typical spiral galaxy like our own... 

The search for titanium-44 was undertaken by the gamma spectrometer aboard the Gamma-Ray Observatory (GRO). The 1.15 MeV line was detected in the direction of Cassiopeia A and Vela, two recent supernova remnants. Mapping the Galaxy in the 1.15 MeV line will undoubtedly be one of the main objectives of the European satellite INTEGRAL, a unique space-borne experiment in which Erance is deeply involved. ... 

Recent computer simulations suggest the existence of vast filamentary networks of ionized gas, or plasma—a cosmic cobweb that now links galaxies and galaxy clusters. These warm cobwebs may be difficult to detect with current satellites. [For more information, see Glanz, J. (1998) Cosmic web captures lost matter. Science. June 26, 280(5372) 2049-50.]... 

The sun, the planets and satellites like the moon were formed 4.5 Gyr ago as a consequence of gravitational instability in a part of a dense interstellar cloud. This particular dense insterstellar cloud no longer exists for obvious reasons, but other dense interstellar clouds can still be observed in our galaxy. Some of these dense... 

Precision of X-ray observations. X-rays do not penetrate the Earth s atmosphere and so all X-ray observations are performed from satellites (or balloons for hard X-rays). However, compared to optical observations, X-ray studies are not intrinsically limited by the number of cluster member galaxies. As an X-ray observation is made longer and longer, more and more X-ray photons are detected and measurements made from the observation can be made more and more precise (up to the systematic calibration of the detectors). 

Several galaxy clusters show also an emission of extreme UV (Lieu et al. 1996, Durret et al. 2002) and soft X-ray (Bonamente et al. 2002, Kaastra et al. 2002) radiation in excess w.r.t. the thermal bremsstrahlung emission. This EUV emission excess may be consistent with both ICS of CMB photons off a non-thermal electron population (e.g., Lieu et al. 1999, Bowyer 2000) with Ee = 608.5 MeV (hv/keV)1/2 149 MeV for hv 60 eV, and with thermal emission from a warm gas at ksTe V 1 keV (Bonamente et al. 2002). In the case of Coma, the simple extrapolation of the ICS spectrum which fits the HXR excess down to energies 0.25 keV does not fit the EUV excess measured in Coma because it is too steep and yields a too high flux compared to the measured flux by the EUV satellite in the 0.065 — 0.245 keV band (Ensslin Biermann 1998). Thus, under the assumption that the HXR and the EUV emission of Coma is produced by ICS of CMB photons, the minimal requirement is that a break in the electron spectrum should be present in the range 0.3 — 2.8 GeV in order to avoid an excessive EUV contribution by the ICS emission and to be consistent with the radio halo spectrum. 

---