1,016 research outputs found
Tracking the impact of environment on the galaxy stellar mass function up to z ~ 1 in the 10 k zCOSMOS sample
We study the impact of the environment on the evolution of galaxies in the zCOSMOS 10 k sample in the redshift range 0.1 †z †1.0 over an area of ~1.5âdeg^2. The considered sample of secure spectroscopic redshifts contains about 8500 galaxies, with their stellar masses estimated by SED fitting of the multiwavelength optical to near-infrared (NIR) photometry. The evolution of the galaxy stellar mass function (GSMF) in high and low density regions provides a tool to study the mass assembly evolution in different environments; moreover, the contributions to the GSMF from different galaxy types, as defined by their SEDs and their morphologies, can be quantified. At redshift z ~ 1, the GSMF is only slightly dependent on environment, but at lower redshifts the shapes of the GSMFs in high- and low-density environments become extremely different, with high density regions exhibiting a marked bimodality, not reproducible by a single Schechter function. As a result of this analysis, we infer that galaxy evolution depends on both the stellar mass and the environment, the latter setting the probability of a galaxy to have a given mass: all the galaxy properties related to the stellar mass show a dependence on environment, reflecting the difference observed in the mass functions. The shapes of the GSMFs of early- and late-type galaxies are almost identical for the extremes of the density contrast we consider, ranging from isolated galaxies to rich group members. The evolution toward z = 0 of the transition mass M_(cross), i.e., the mass at which the early- and late-type GSMFs match each other, is more rapid in high density environments, because of a difference in the evolution of the normalisation of GSMFs compared to the total one in the considered environment. The same result is found by studying the relative contributions of different galaxy types, implying that there is a more rapid evolution in overdense regions, in particular for intermediate stellar masses. The rate of evolution is different for sets of galaxy types divided on the basis of their SEDs or their morphologies, tentatively suggesting that the migration from the blue cloud to the red sequence occurs on a shorter timescale than the transformation from disc-like morphologies to ellipticals. Our analysis suggests that environmental mechanisms of galaxy transformation start to be more effective at z < 1. The comparison of the observed GSMFs to the same quantities derived from a set of mock catalogues based on semi-analytical models shows disagreement, in both low and high density environments: in particular, blue galaxies in sparse environments are overproduced in the semi-analytical models at intermediate and high masses, because of a deficit of star formation suppression, while at z < 0.5 an excess of red galaxies is present in dense environments at intermediate and low masses, because of the overquenching of satellites
Failure Analysis of the Method of Adjoint Systems to Determine Optimal Trajectories
Failure analysis of adjoint systems method for determining optimal trajectorie
Specific star formation rates to redshift 5 from the FORS Deep Field and the GOODS-S Field
We explore the build-up of stellar mass in galaxies over a wide redshift
range 0.4 < z < 5.0 by studying the evolution of the specific star formation
rate (SSFR), defined as the star formation rate per unit stellar mass, as a
function of stellar mass and age. Our work is based on a combined sample of ~
9000 galaxies from the FORS Deep Field and the GOODS-S field, providing high
statistical accuracy and relative insensitivity against cosmic variance. As at
lower redshifts, we find that lower-mass galaxies show higher SSFRs than higher
mass galaxies, although highly obscured galaxies remain undetected in our
sample. Furthermore, the highest mass galaxies contain the oldest stellar
populations at all redshifts, in principle agreement with the existence of
evolved, massive galaxies at 1 < z < 3. It is remarkable, however, that this
trend continues to very high redshifts of z ~ 4. We also show that with
increasing redshift the SSFR for massive galaxies increases by a factor of ~
10, reaching the era of their formation at z ~ 2 and beyond. These findings can
be interpreted as evidence for an early epoch of star formation in the most
massive galaxies, and ongoing star-formation activity in lower mass galaxies.Comment: Accepted for publication in ApJL; 4 pages, 2 color figures, uses
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Treatment of hepatitis C in injecting drug users in the Perth metropolitan area
This study used a sequential exploratory mixed methods research to develop a better understanding of the context of treatment intentions of IDUs living with HCV in Perth Metropolitan area. Sixty three percent of participants expressed that they had intention to uptake HCV treatment. Characteristics of treatment, stigma and lack of support emerged as factors influencing intention to uptake HCV treatment. The findings will help to make the world a better place by scaling up HCV treatment for IDUs in the community setting
The clustering properties of radio-selected AGN and star-forming galaxies up to redshifts z~3
We present the clustering properties of a complete sample of 968 radio
sources detected at 1.4 GHz by the VLA-COSMOS survey with radio fluxes brighter
than 0.15 mJy. 92% have redshift determinations from the Laigle et al. (2016)
catalogue. Based on their radio-luminosity, these objects have been divided
into two populations of 644 AGN and 247 star-forming galaxies. By fixing the
slope of the auto-correlation function to gamma=2, we find
r_0=11.7^{+1.0}_{-1.1} Mpc for the clustering length of the whole sample, while
r_0=11.2^{+2.5}_{-3.3} Mpc and r_0=7.8^{+1.6}_{-2.1} Mpc (r_0=6.8^{+1.4}_{-1.8}
Mpc if we restrict our analysis to z<0.9) are respectively obtained for AGN and
star-forming galaxies. These values correspond to minimum masses for dark
matter haloes of M_min=10^[13.6^{+0.3}_{-0.6}] M_sun for radio-selected AGN and
M_min=10^[13.1^{+0.4}_{-1.6}] M_sun for radio-emitting star-forming galaxies
(M_min=10^[12.7^{+0.7}_{-2.2}] M_sun for z<0.9). Comparisons with previous
works imply an independence of the clustering properties of the AGN population
with respect to both radio luminosity and redshift. We also investigate the
relationship between dark and luminous matter in both populations. We obtain
/M_halo/M_halo<~10^{-2.4} in the case of
star-forming galaxies. Furthermore, if we restrict to z<~0.9 star-forming
galaxies, we derive /M_halo<~10^{-2.1}, result which clearly indicates the
cosmic process of stellar build-up as one moves towards the more local
universe. Comparisons between the observed space density of radio-selected AGN
and that of dark matter haloes shows that about one in two haloes is associated
with a black hole in its radio-active phase. This suggests that the
radio-active phase is a recurrent phenomenon.Comment: 11 pages, 7 figures, minor changes to match published version on
MNRA
Integrating Superconductive and Optical Circuits
We have integrated on oxidized silicon wafers superconductive films and
Josephson junctions along with sol-gel optical channel waveguides. The
fabrication process is carried out in two steps that result to be solid and
non-invasive. It is demonstrated that 660 nm light, coupled from an optical
fibre into the channel sol-gel waveguide, can be directed toward
superconducting tunnel junctions whose current-voltage characteristics are
affected by the presence of the radiation. The dependence of the change in the
superconducting energy gap under optical pumping is discussed in terms of a
non-equilibrium superconductivity model.Comment: Document composed of 7 pages of text and 3 figure
The environmental properties of radio-emitting AGN
We study the environmental properties of z<1.2 radio-selected AGN belonging
to the ~2 square degrees of the COSMOS field, finding that about 20% of them
appear within overdense structures. AGN with are twice more likely to be found in clusters with respect to fainter
sources (~38% vs ~15%), just as radio-selected AGN with stellar masses
are twice more likely to be found in overdense
environments with respect to objects of lower mass (~24% vs ~11%). Comparisons
with galaxy samples further suggest that radio-selected AGN of large stellar
mass tend to avoid underdense environments more than normal galaxies with the
same stellar content. Stellar masses also seem to determine the location of
radio-active AGN within clusters: ~100% of the sources found as satellite
galaxies have , while ~100% of the AGN coinciding with a
cluster central galaxy have . No different location within
the cluster is instead observed for AGN of various radio luminosities. Radio
AGN which also emit in the MIR show a marked preference to be found as isolated
galaxies (~70%) at variance with those also active in the X-ray which all seem
to reside within overdensities. What emerges from our work is a scenario
whereby physical processes on sub-pc and kpc scales (e.g. emission respectively
related to the AGN and to star formation) are strongly interconnected with the
large-scale environment of the AGN itself.Comment: 8 pages, 6 figures, to appear on MNRA
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