21 research outputs found
A local infrared perspective to deeper ISO surveys
We present new techniques to produce IRAS 12 micron samples of galaxies andstars. We show that previous IRAS 12 micron samples are incompatible fordetailed comparison with ISO surveys and review their problems. We provide astellar infrared diagnostic diagram to distinguish galaxies from stars withoutusing longer wavelength IRAS colour criteria and produce complete 12 micronsamples of galaxies and stars. This new technique allows us to estimate thecontribution of non-dusty galaxies to the IRAS 12 micron counts and produce atrue local mid-infrared extragalactic sample compatible with ISO surveys. Wepresent our initial analysis and results
Non-minimally coupled dark matter: effective pressure and structure formation
We propose a phenomenological model in which a non-minimal coupling between
gravity and dark matter is present in order to address some of the apparent
small scales issues of \lcdm model. When described in a frame in which gravity
dynamics is given by the standard Einstein-Hilbert action, the non-minimal
coupling translates into an effective pressure for the dark matter component.
We consider some phenomenological examples and describe both background and
linear perturbations. We show that the presence of an effective pressure may
lead these scenarios to differ from \lcdm at the scales where the non-minimal
coupling (and therefore the pressure) is active. In particular two effects are
present: a pressure term for the dark matter component that is able to reduce
the growth of structures at galactic scales, possibly reconciling simulations
and observations; an effective interaction term between dark matter and baryons
that could explain observed correlations between the two components of the
cosmic fluid within Tully-Fisher analysis.Comment: 18 pages, 6 figures, references added. Published in JCA
A new method to constrain the appearance and disappearance of observed jellyfish galaxy tails
Galaxie
Near-infrared template spectra of normal galaxies: k-corrections, galaxy models and stellar populations
We have observed 28 local galaxies in the wavelength range between 1 and 2.4
mic in order to define template spectra of the normal galaxies along the Hubble
sequence. Five galaxies per morphological type were observed in most cases, and
the resulting RMS spread of the normalized spectra of each class, including
both intrinsic differences and observational uncertainties, is about 1% in K,
2% in H and 3% in J. Many absorption features can be accurately measured. The
target galaxies and the spectroscopic aperture (7"x53") were chosen to be
similar to those used by Kinney et al. (1996) to define template UV and optical
spectra. The two data sets are matched in order to build representative spectra
between 0.1 and 2.4 mic. The continuum shape of the optical spectra and the
relative normalization of the near-IR ones were set to fit the average
effective colours of the galaxies of the various Hubble classes. The resulting
spectra are used to compute the k-corrections of the normal galaxies in the
near-IR bands and to check the predictions of various spectral synthesis
models: while the shape of the continuum is generally well predicted, large
discrepancies are found in the absorption lines. Among the other possible
applications, here we also show how these spectra can be used to place
constraints on the dominant stellar population in local galaxies. Spectra and
k-corrections are publicly available and can be downloaded from the web site
http://www.arcetri.astro.it/~filippo/spectra.Comment: 15 pages including figures, MNRAS, in pres
Walk on the low side: LOFAR explores the low-frequency radio emission of GASP jellyfish galaxies
Galaxie