12,992 research outputs found
A mid-IR study of Hickson Compact Groups II. Multi-wavelength analysis of the complete GALEX-Spitzer Sample
We present a comprehensive study on the impact of the environment of compact
galaxy groups on the evolution of their members using a multi-wavelength
analysis, from the UV to the infrared, for a sample of 32 Hickson compact
groups (HCGs) containing 135 galaxies. Fitting the SEDs of all galaxies with
the state-of-the-art model of da Cunha (2008) we can accurately calculate their
mass, SFR, and extinction, as well as estimate their infrared luminosity and
dust content. We compare our findings with samples of field galaxies,
early-stage interacting pairs, and cluster galaxies with similar data. We find
that classifying the groups as dynamically "old" or "young", depending on
whether or not at least one quarter of their members are early-type systems, is
physical and consistent with past classifications of HCGs based on their atomic
gas content. [...ABRIDGED...] We also examine their SF properties, UV-optical
and mid-IR colors, and we conclude that all the evidence point to an
evolutionary scenario in which the effects of the group environment and the
properties of the galaxy members are not instantaneous. Early on, the influence
of close companions to group galaxies is similar to the one of galaxy pairs in
the field. However, as the time progresses, the effects of tidal torques and
minor merging, shape the morphology and star formation history of the group
galaxies, leading to an increase of the fraction of early-type members and a
rapid built up of the stellar mass in the remaining late-type galaxies.Comment: Accepted for publication in A&A. Figure resolution degraded for arXiv
limits, full resolution paper available at
http://www.physics.uoc.gr/~bitsakis/paperII_bitsakis.pd
Dynamic modeling of three-phase upflow fixed-bed reactor including pore diffusion
The dynamics of a three-phase upflow fixed-bed reactor are investigated using a non-isothermal heterogeneous model including gas–liquid and liquid–solid mass transfer and diffusion/reaction phenomena inside the catalyst. The partial differential and algebraic equations involving three integration variables (time and two space coordinates) are solved via discretization of the spatial coordinates coupled with the Gear method. For a multistep hydrogenation on a shell catalyst, the model exhibits significant effects of the external and above all internal resistance to hydrogen transfer but also non-trivial internal hydrocarbons concentration profiles. A simplified model is compared with the extended one and with experimental data in transient regime. In the investigated conditions—hydrocarbons in large excess—the diffusion of hydrocarbons appears to be actually not limiting, so that the simplest model predicts accurately the transient reactor behavior
Morphological Classification of Local Luminous Infrared Galaxies
We present an analysis of the morphological classification of 89 luminous
infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey
(GOALS) sample using non-parametric coefficients and compare their morphology
as a function of wavelength. We rely on images obtained in the optical (B- and
I-band) as well as in the infrared (H-band and 5.8m). Our classification
is based on the calculation of and the second order of light ()
non-parametric coefficients which we explore as a function of stellar mass
(), infrared luminosity () and star formation rate (SFR). We
investigate the relation between , the specific SFR (sSFR) and the dust
temperature () in our galaxy sample. We find that is a
better morphological tracer than , as it allows to distinguish systems
formed by double systems from isolated and post-merger LIRGs. The
multi-wavelength analysis allows us to identify a region in the -
parameter space where ongoing mergers reside, regardless of the band used to
calculate the coefficients. In particular when measured in the H-band, this
region can be used to identify ongoing mergers, with a minimal contamination
from LIRGs in other stages. We also find that while the sSFR is positively
correlated with when measured in the mid-infrared, i.e. star-bursting
galaxies show more compact emission, it is anti-correlated with the B-band
based . We interpret this as the spatial decoupling between obscured
and un-obscured star formation, whereby the ultraviolet/optical size of a LIRGs
experience an intense dust enshrouded central starburst is larger than in the
one in the mid-infrared since the contrast between the nuclear to the extended
disk emission is smaller in the mid-infrared. This has important implications
for high redshift surveys of dusty sources. [abridged]Comment: ( 18 pages, 12 figures, Accepted for publication in A&A
Raman and quantitative-phase microscope with counter-propagating beams demonstrated on HeLa cells
Raman spectroscopy probes the chemical composition of biological samples with sub-micron resolution, rendering it a powerful tool in the diagnosis of several diseases and the study unstained biological samples. However, the weak Raman signal leads to long acquisition times, unsuited to study dynamical processes or large samples. Quantitative phase microscopy can speed up the diagnosis, provide complementary data, and potentially link the Raman fingerprint of the sample with corresponding refractive indices. Here we demonstrate a 4Pi microscope that records both the Raman and quantitative phase information from the same sample spot
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