69 research outputs found
Trends for Outer Disk Profiles
The surface-brightness profiles of galaxy disks fall into three main classes,
based on whether they are simple exponentials (Type I), bend down at large
radii (Type II, "truncations") or bend up at large radii (Type III,
"antitruncations"). Here, we discuss how the frequency of these different
profiles depends on Hubble type, environment, and the presence or absence of
bars; these trends may herald important new tests for disk formation models.Comment: LaTeX, 2 pages, 1 EPS figure, uses modified newpasp.sty (included).
To appear in Formation and Evlution of Galaxy Disks, eds. J.G. Funes and E.M.
Corsin
Photometric scaling relations of antitruncated stellar discs in S0-Scd galaxies
It has been recently found that the characteristic photometric parameters of
antitruncated discs in S0 galaxies follow tight scaling relations. We
investigate if similar scaling relations are satisfied by galaxies of other
morphological types. We have analysed the trends in several photometric planes
relating the characteristic surface brightness and scalelengths of the breaks
and the inner and outer discs of local antitruncated S0-Scd galaxies, using
published data and fits performed to the surface brightness profiles of two
samples of Type-III galaxies in the R and Spitzer 3.6 microns bands. We have
performed linear fits to the correlations followed by different galaxy types in
each plane, as well as several statistical tests to determine their
significance. We have found that: 1) the antitruncated discs of all galaxy
types from Sa to Scd obey tight scaling relations both in R and 3.6 microns, as
observed in S0s; 2) the majority of these correlations are significant
accounting for the numbers of the available data samples; 3) the trends are
clearly linear when the characteristic scalelengths are plotted on a
logarithmic scale; and 4) the correlations relating the characteristic surface
brightnesses of the inner and outer discs and the breaks with the various
characteristic scalelengths significantly improve when the latter are
normalized to the optical radius of the galaxy. The results suggest that the
scaling relations of Type-III discs are independent of the morphological type
and the presence (or absence) of bars within the observational uncertainties of
the available datasets, although larger and deeper samples are required to
confirm this. The tight structural coupling implied by these scaling relations
impose strong constraints on the mechanisms proposed for explaining the
formation of antitruncated stellar discs in the galaxies across the whole
Hubble Sequence (Abridged).Comment: Accepted for publication in Astronomy & Astrophysics, 18 pages, 12
figures, 7 table
The Outer Structure of Galactic Disks: Connections Between Bars, Disks, and Environments
Surface-brightness profiles for early-type (S0-Sb) disks exhibit three main
classes (Type I, II, and III). Type II profiles are more common in barred
galaxies, and most of the time appear to be related to the bar's Outer Lindblad
Resonance. Roughly half of barred galaxies in the field have Type II profiles,
but almost none in the Virgo Cluster do; this might be related to ram-pressure
stripping in clusters. A strong \textit{anti}correlation is found between Type
III profiles ("antitruncations") and bars: Type III profiles are most common
when there is no bar, and least common when there is a strong bar.Comment: LaTeX, 4 pages, 2 EPS figures, uses modified newpasp.sty (included).
To appear in Pathways through an Eclectic Universe, eds. J. H. Knapen, T. J.
Mahoney, & A. Vazdeki
On the influence of environment on star forming galaxies
We use our state-of-the-art semi analytic model for GAlaxy Evolution and
Assembly (GAEA), and observational measurements of nearby galaxies to study the
influence of the environment on the gas content and gaseous/stellar disc sizes
of star-forming galaxies. We analyse the origin of differences between physical
properties of satellites and those of their central counterparts, identified by
matching the Vmax of their host haloes at the accretion time of the satellites.
Our model reproduces nicely the differences between centrals and satellites
measured for the HI mass, size of the star-forming region, and stellar radii.
In contrast, our model predicts larger differences with respect to data for the
molecular gas mass and star formation rate. By analysing the progenitors of
central and satellite model galaxies, we find that differences in the gas
content arise after accretion, and can be entirely ascribed to the
instantaneous stripping of the hot gas reservoir. The suppression of cold gas
replenishment via cooling and star formation leads to a reduction of the cold
gas and of its density. Therefore, more molecular gas is lost than lower
density HI gas, and model satellites have less molecular gas and lower star
formation rates than observed satellites. We argue that these disagreements
could be largely resolved with the inclusion of a proper treatment for
ram-pressure stripping of cold gas and a more gradual stripping of the hot gas
reservoir. A more sophisticated treatment of angular momentum exchanges,
accounting for the multi-phase nature of the gaseous disc is also required.Comment: 15 pages, 9 figures, accepted for publication in MNRA
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