20,460 research outputs found
Ultraviolet absorption lines in cosmic ray heated H I regions
Ultraviolet absorption lines in cosmic ray heated H I region
On breaking the age-metallicity degeneracy in early-type galaxies: Outflows versus Star Formation Efficiency
A simple model of chemical enrichment in cluster early-type galaxies is
presented where the main parameters driving the formation of the stellar
component are reduced to four: infall timescale (tf), formation epoch (zF),
star formation efficiency (Ceff) and fraction of gas ejected in outflows
(Bout). We find that only variations in Bout or Ceff can account for the
colour-magnitude relation, so that the most luminous galaxies had low values of
ejected gas and high efficiencies. The combination of chemical enrichment
tracks with population synthesis models is used to explore the correlation
between mass-to-light ratios and masses. A significant slope mismatch is found
between stellar and total M/L ratios, which cannot be explained by an age
spread and implies a non-linear correlation between total and stellar mass. The
sequences driven by star formation efficiency and outflows are shown to predict
different trends at high redshift. Measurement of the dependence of the tilt of
the fundamental plane on redshift will break the degeneracy between outflows
and star formation efficiency, which will enable us to determine whether the
colour-magnitude relation is controlled by age or metallicity.Comment: 8 pages, 5 figures. To be published in MNRA
The Impact of Galaxy Formation on the Diffuse Background Radiation
The far infrared background is a sink for the hidden aspects of galaxy
formation. At optical wavelengths, ellipticals and spheroids are old, even at
Neither the luminous formation phase nor their early evolution is
seen in the visible. We infer that ellipticals and, more generally, most
spheroids must have formed in dust-shrouded starbursts. In this article, we
show how separate tracking of disk and spheroid star formation enables us to
infer that disks dominate near the peak in the cosmic star formation rate at z
\lapproxeq 2 and in the diffuse ultraviolet/optical/infrared background,
whereas spheroid formation dominates the submillimetre background.Comment: 12 pages, 5 figures, to appear in proceedings of IAU symp.204, "The
Extragalactic Infrared Background and its Cosmological Implications", Martin
Harwit and Michael G. Hauser, ed
On the Fueling of Massive Black Holes and the Properties of their Host Spheroids
We study the relation between nuclear massive black holes and their host
spheroid gravitational potential. Using simple models, we analyze how gas is
expected to be transported in the nuclear regions of galaxies. When we couple
it with the expected gas lifetime given by the Kennicutt-Schmidt Law, this
naturally leads to the `M_BH - M_virial' and `M_BH - sigma' relations. We also
numerically test, using AMR simulations, our simple models for the mass
transport with satisfactory results.Comment: Reduced version that fit the 4-page limit. In press ApJ Letter
AGN feedback from Jet-ISM/IGM interactions
We study the propagation of relativistic jets originating from AGNs within
the Interstellar/Intergalactic Medium of their host galaxies, and use it to
build a model for the suppression of stellar formation within the expanding
cocoon.Comment: 2 pages, 3 figures. Poster presented at IAU Symp. no. 245 ("Formation
and Evolution of Galaxy Bulges"), Oxford, July 16-20, 200
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