Rubin-LSST

Abstract:

We seek to understand whether the stellar populations of galactic bulges show evidence of secular evolution triggered by the presence of the disc. To this end we re-analyse the sample of Proctor & Sansom (2002), deriving stellar population ages and element abundances from absorption line indices as functions of central velocity dispersion and Hubble type. In agreement with other studies in the literature, we find that bulges have relatively low luminosity weighted ages, the lowest age derived being 1.3 Gyr. Hence bulges are not generally old, but actually rejuvenated systems. We discuss evidence that this might be true also for the bulge of the Milky Way. The smallest bulges are the youngest with the lowest /Fe ratios indicating the presence of significant star formation events involving 10 30 per cent of their total mass in the past 1 2 Gyr. No significant correlations of the stellar population parameters with Hubble Type are found. We show that the above relationships with coincide perfectly with those of early-type galaxies. At a given velocity dispersion, bulges and elliptical galaxies are indistinguishable as far as their stellar populations are concerned. These results favour an inside-out formation scenario and indicate that the discs in spiral galaxies of Hubble types Sbc and earlier cannot have a significant influence on the evolution of the stellar populations in the bulge component. The phenomenon of pseudobulge formation must be restricted to spirals of types later than Sbc. © 2008 Copyright International Astronomical Union 2008.

Abstract:

We discuss some recent integral field spectroscopy using the SAURON instrument of a sample consisting of 24 early-type spirals, part of the SAURON Survey, and 18 late-type spirals. Using 2-dimensional maps of their stellar radial velocity, velocity dispersion, and absorption line strength, it is now much easier to understand the nature of nearby galactic bulges. We discuss a few highlights of this work, and point out some new ideas about the formation of galactic bulges. © 2008 Copyright International Astronomical Union 2008.

Abstract:

Supermassive black holes are a key element in our understanding of how galaxies form. Most of the progress in this very active field of research is based on just ~30 determination of black hole masses, accumulated over the past decade. We illustrate how integral-field spectroscopy, and in particular our OASIS modeling effort can help improve the current situation. © 2008 Copyright International Astronomical Union 2008.

Abstract:

We present a measurement of the top-quark mass in pp̄ collisions at s=1.96TeV which uses events with an inclusive signature of missing transverse energy and jets. The event selection is sensitive to tt̄→W+bW- b̄→lνbqq′b̄ independent of the lepton flavor and results in a large acceptance for W→τν decays. All-hadronic tt̄ decays and events with identified electrons or muons are vetoed to provide a statistically independent sample with respect to all previous measurements. The top-quark mass is inferred from the distribution of the scalar sum of all jet transverse energies and the missing transverse energy. Using 311pb-1 of integrated luminosity recorded by the Collider Detector at Fermilab, we measure a top-quark mass mt=172.3-9.6+10.8(stat)±10.8(syst)GeV/c2. While the uncertainty on mt is larger than that of other measurements, the result is statistically uncorrelated with those of other methods and thus can help to reduce the overall mt uncertainty when combined with other existing measurements. © 2007 The American Physical Society.