24 research outputs found
Evolution of the infrared luminosity density and star formation history up to z~1: preliminary results from MIPS
Using deep observations of the Chandra Deep Field South obtained with MIPS at
24mic, we present our preliminary estimates on the evolution of the infrared
(IR) luminosity density of the Universe from z=0 to z~1. We find that a pure
density evolution of the IR luminosity function is clearly excluded by the
data. The characteristic luminosity L_IR* evolves at least by (1+z)^3.5 with
lookback time, but our monochromatic approach does not allow us to break the
degeneracy between a pure evolution in luminosity or an evolution in both
density and luminosity. Our results imply that IR luminous systems (L_IR >
10^11 L_sol) become the dominant population contributing to the comoving IR
energy density beyond z~0.5-0.6. The uncertainties affecting our measurements
are largely dominated by the poor constraints on the spectral energy
distributions that are used to translate the observed 24mic flux into
luminosities.Comment: 4 pages, 2 figures. To be published in "Starbursts: From 30 Doradus
to Lyman Break Galaxies", held in Cambridge, 6-10 September 2004, Ed. R. de
Grijs & R. M. Gonzalez Delgad
The antibacterial, anti-biofilm, anti-inflammatory and virulence inhibition properties of Portuguese honeys
In Portugal, beekeeping activity has a significant weight among livestock production. The antimicrobial activities of Portuguese honeys have been reported, but the anti-biofilm formation and anti-virulence abilities have not been investigated. The main goal of this work was to study the impact of three monofloral honeys (citrus, lavender and strawberry tree) honeys on adherence of Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Pseudomonas aeruginosa, as well as the influence of the same honeys on virulence using Galleria mellonella as a model. In addition, the general physico-chemical characterization of these honeys and the microbial quality were also performed. The anti-inflammatory activity was also estimated by analyzing the activity of the enzymes hyaluronidase and lipoxygenase. The tested honeys complied with European legislation and no microbial contamination was observed. Of all the honeys at 12.5 and 25%, w/v the citrus honey caused the highest inhibitory activity against P. aeruginosa. Strawberry tree honey at 25% w/v was able to significantly inhibit the MRSA strains. Anti-biofilm formation and anti-inflammatory activities were observed. The different honeys impaired the virulence of S. aureus and MRSA strains. The Portuguese honeys were capable of combating the tested bacterial pathogens not only by inhibiting their growth but also by affecting important pathogenicity properties, such as adherence and virulence
Hyperspectral Sensing Techniques Applied to Bio-masses Characterization: The Olive Husk Case
Olive husk (OH) quality, in respect of constituting particles characteristics (olive stones and pulp residues as result after pressing), represents an important issue. OH particles size class distribution and composition play, in fact, an important role for OH utilization as: organic amendment, bio-mass, food ingredient, plastic filler, abrasive, raw material in the cosmetic sector, dietary animal supplementation, etc. . OH is characterised by a strong variability according to olive characteristics and olive oil production process. Actually it does not exist any strategy able to quantify OH chemical-physical attributes versus its correct utilisation adopting simple, efficient and low costs analytical tools. Furthermore the possibility to perform its continuous monitoring, without any samples collection and analysis at laboratory scale, could strongly enhance OH utilization, with a great economic and environmental benefits. In this paper an analytical approach, based on HyperSpectral Imaging (HSI) is presented. HSI allows to perform, also on-line, a full quantification of OH characteristics in order to qualify this product for its further re-use, with particular reference as bio-mass. HSI was applied to different samples of OH, characterized by different moisture, different residual pulp content and different size class distributions. Results are presented and critically evaluated. © 2011 IFIP International Federation for Information Processing
SPACE: the spectroscopic all-sky cosmic explorer
We describe the scientific motivations, the mission concept and the instrumentation of SPACE, a class-M mission proposed for concept study at the first call of the ESA Cosmic-Vision 2015â2025 planning cycle. SPACE aims to produce the largest three-dimensional evolutionary map of the Universe over the past 10 billion years by taking near-IR spectra and measuring redshifts for more than half a billion galaxies at 0 < z < 2 down to AB ⌠23 over 3Ï sr of the sky. In addition, SPACE will also target a smaller sky field, performing a deep spectroscopic survey of millions of galaxies to AB ⌠26 and at 2 < z < 10+. These goals are unreachable with ground-based observations due to the â500 times higher sky background (see e.g. Aldering, LBNL report number LBNL-51157, 2001). To achieve the main science objectives, SPACE will use a 1.5 m diameter Ritchey- Chretien telescope equipped with a set of arrays of Digital Micro-mirror Devices covering a total field of view of 0.4 deg2, and will perform large-multiplexing multi-object spectroscopy (e.g. â6000 targets per pointing) at a spectral resolution of RâŒ400 as well as diffraction-limited imaging with continuous coverage from 0.8 to 1.8 ÎŒm. Owing to the depth, redshift range, volume coverage and quality of its spectra, SPACE will reveal with unique sensitivity most of the fundamental cosmological signatures, including the power spectrum of density fluctuations and its turnover. SPACE will also place high accuracy constraints on the dark energy equation of state parameter and its evolution by measuring the baryonic acoustic oscillations imprinted when matter and radiation decoupled, the distanceluminosity relation of cosmological supernovae, the evolution of the cosmic expansion rate, the growth rate of cosmic large-scale structure, and high-z galaxy clusters. The datasets from the SPACE mission will represent a long lasting legacy for the whole astronomical community whose data will be mined for many years to come
The clustering of Hα emitters at z = 2.23 from HiZELS
We present a clustering analysis of 370 high-confidence Hα emitters (HAEs) at z = 2.23. The HAEs are detected in the Hi-Z Emission Line Survey (HiZELS), a large-area blank field 2.121 ÎŒm narrow-band survey using the United Kingdom Infrared Telescope Wide Field Camera (WFCAM). Averaging the two-point correlation function of HAEs in two Ë1° scale fields [United Kingdom Infrared Deep Sky Survey/Ultra Deep Survey (UDS) and Cosmological Evolution Survey (COSMOS) fields] we find a clustering amplitude equivalent to a correlation length of r0 = 3.7 ± 0.3 h-1 Mpc for galaxies with star formation rates of âł7 Mâ yr-1. The data are also well-fitted by the expected correlation function of cold dark matter (CDM), scaled by a bias factor: ÏHAE = b2ÏDM where b=2.4-0.2+0.1. The corresponding 'characteristic' mass for the haloes hosting HAEs is log (Mh/[h-1 Mâ]) = 11.7 ± 0.1. Comparing to the latest semi-analytic GALFORM predictions for the evolution of HAEs in a ÎCDM cosmology, we find broad agreement with the observations, with GALFORM predicting an HAE correlation length of Ë4 h-1 Mpc. Motivated by this agreement, we exploit the simulations to construct a parametric model of the halo occupation distribution (HOD) of HAEs, and use this to fit the observed clustering. Our best-fitting HOD can adequately reproduce the observed angular clustering of HAEs, yielding an effective halo mass and bias in agreement with that derived from the scaled ÏDM fit, but with the relatively small sample size the current data provide a poor constraint on the HOD. However, we argue that this approach provides interesting hints into the nature of the relationship between star-forming galaxies and the matter field, including insights into the efficiency of star formation in massive haloes. Our results support the broad picture that 'typical' (âČLâ
) star-forming galaxies have been hosted by dark matter haloes with Mh âČ 1012 h-1 Mâ since z â 2, but with a broad occupation distribution and clustering that is likely to be a strong function of luminosity
Observational Limits on the Gas Mass of a z = 4.9 Galaxy
We present the results of a search for molecular gas emission from a star-forming galaxy at z = 4.9. The galaxy benefits from magnification of 22 +/- 5x due to strong gravitational lensing by the foreground cluster MS1358+62. We target the CO(5-4) emission at a known position and redshift from existing Hubble Space Telescope/Advanced Camera for Surveys imaging and Gemini/NIFS [O Pi]3727 imaging spectroscopy, and obtain a tentative detection at the 4.3 sigma level with a flux of 0.104 +/- 0.024 Jy km s(-1). From the CO line luminosity and assuming a CO-to-H-2 conversion factor alpha = 2, we derive a gas mass M-gas similar to 1(-0.6)(+1) x 10(9) M-circle dot. Combined with the existing data, we derive a gas fraction M-gas/(M-gas + M-*) = 0.59+(+0.11)(-0.06). The faint line flux of this galaxy highlights the difficulty of observing molecular gas in representative galaxies at this epoch, and suggests that routine detections of similar galaxies in the absence of gravitational lensing will remain challenging even with ALMA in full science operations.Peer reviewe
Resolved spectroscopy of gravitationally lensed galaxies: global dynamics and star-forming clumps on âŒ100 pc scales at 1 < z < 4
We present adaptive optics-assisted integral field spectroscopy around the Hα or HÎČ lines of 12 gravitationally lensed galaxies obtained with VLT/SINFONI, Keck/OSIRIS and Gemini/NIFS. We combine these data with previous observations and investigate the dynamics and star formation properties of 17 lensed galaxies at 1 < z < 4. Thanks to gravitational magnification of 1.4â90 times by foreground clusters, effective spatial resolutions of 40â700 pc are achieved. The magnification also allows us to probe lower star formation rates (SFRs) and stellar masses than unlensed samples; our target galaxies feature dust-corrected SFRs derived from Hα or HÎČ emission of âŒ0.8â40 Mâ yrâ1, and stellar masses M* ⌠4 Ă 108â6 Ă 1010 Mâ. All of the galaxies show velocity gradients, with 59âperâcent consistent with being rotating discs and a likely merger fraction of 29âperâcent, with the remaining 12âperâcent classed as âundeterminedâ. We extract 50 star-forming clumps with sizes in the range 60 pcâ1 kpc from the Hα (or HÎČ) maps, and find that their surface brightnesses, ÎŁclump and their characteristic luminosities, L0, evolve to higher luminosities with redshift. We show that this evolution can be described by fragmentation on larger scales in gas-rich discs, and is likely to be driven by evolving gas fractions
Hubble Space Telescope Hα imaging of star-forming galaxies at z â 1â1.5 : evolution in the size and luminosity of giant Hâii regions
We present Hubble Space Telescope/Wide Field Camera 3 narrow-band imaging of the Hα emission in a sample of eight gravitationally lensed galaxies at z = 1â1.5. The magnification caused by the foreground clusters enables us to obtain a median source plane spatial resolution of 360âpc, as well as providing magnifications in flux ranging from âŒ10Ă to âŒ50Ă. This enables us to identify resolved star-forming Hâii regions at this epoch and therefore study their Hα luminosity distributions for comparisons with equivalent samples at z ⌠2 and in the local Universe. We find evolution in the both luminosity and surface brightness of Hâii regions with redshift. The distribution of clump properties can be quantified with an Hâii region luminosity function, which can be fit by a power law with an exponential break at some cut-off, and we find that the cut-off evolves with redshift. We therefore conclude that âclumpyâ galaxies are seen at high redshift because of the evolution of the cut-off mass; the galaxies themselves follow similar scaling relations to those at z = 0, but their Hâii regions are larger and brighter and thus appear as clumps which dominate the morphology of the galaxy. A simple theoretical argument based on gas collapsing on scales of the Jeans mass in a marginally unstable disc shows that the clumpy morphologies of high-z galaxies are driven by the competing effects of higher gas fractions causing perturbations on larger scales, partially compensated by higher epicyclic frequencies which stabilize the disc
Energetic galaxy-wide outflows in high-redshift ultraluminous infrared galaxies hosting AGN activity
We present integral field spectroscopy observations, covering the [O
III]4959,5007 emission-line doublet of eight high-redshift (z=1.4-3.4)
ultra-luminous infrared galaxies (ULIRGs) that host Active Galactic Nuclei
(AGN) activity, including known sub-millimetre luminous galaxies (SMGs). The
targets have moderate radio luminosities that are typical of high-redshift
ULIRGs (L(1.4GHz)=10^(24)-10^(25)W/Hz) and therefore are not radio-loud AGN. We
de-couple kinematic components due to the galaxy dynamics and mergers from
those due to outflows. We find evidence in the four most luminous systems (L([O
III])>~10^(43)erg/s) for the signatures of large-scale energetic outflows:
extremely broad [O III] emission (FWHM ~ 700-1400km/s) across ~4-15kpc, with
high velocity offsets from the systemic redshifts (up to ~850km/s). The four
less luminous systems have lower quality data displaying weaker evidence for
spatially extended outflows. We estimate that these outflows are potentially
depositing energy into their host galaxies at considerable rates
(~10^(43)-10^(45)erg/s); however, due to the lack of constraints on the density
of the outflowing material and the structure of the outflow, these estimates
should be taken as illustrative only. Based on the measured maximum velocities
(v(max)~400-1400km/s) the outflows observed are likely to unbind some fraction
of the gas from their host galaxies, but are unlikely to completely remove gas
from the galaxy haloes. By using a combination of energetic arguments and a
comparison to ULIRGs without clear evidence for AGN activity, we show that the
AGN activity could be the dominant power source for driving all of the observed
outflows, although star formation may also play a significant role in some of
the sources.Comment: 25 pages, 11 figures, accepted by MNRA
The LABOCA survey of the Extended Chandra Deep Field-South: clustering of submillimetre galaxies
We present a measurement of the spatial clustering of submillimetre galaxies (SMGs) at z= 1â3. Using data from the 870âÎŒm Large APEX Bolometer Camera (LABOCA) submillimetre survey of the Extended Chandra Deep Field-South, we employ a novel technique to measure the cross-correlation between SMGs and galaxies, accounting for the full probability distributions for photometric redshifts of the galaxies. From the observed projected two-point cross-correlation function we derive the linear bias and characteristic dark matter halo masses for the SMGs. We detect clustering in the cross-correlation between SMGs and galaxies at the >4Ï level. Accounting for the clustering of galaxies from their autocorrelation function, we estimate an autocorrelation length for SMGs of GraphicâMpc assuming a power-law slope Îł= 1.8, and derive a corresponding dark matter halo mass of Graphic. Based on the evolution of dark matter haloes derived from simulations, we show that that the z= 0 descendants of SMGs are typically massive (âŒ2â3L*) elliptical galaxies residing in moderate- to high-mass groups (Graphic). From the observed clustering we estimate an SMG lifetime of âŒ100âMyr, consistent with lifetimes derived from gas consumption times and star formation time-scales, although with considerable uncertainties. The clustering of SMGs at z⌠2 is consistent with measurements for optically selected quasi-stellar objects (QSOs), supporting evolutionary scenarios in which powerful starbursts and QSOs occur in the same systems. Given that SMGs reside in haloes of characteristic mass âŒ6 Ă 1012âhâ1âMâ, we demonstrate that the redshift distribution of SMGs can be described remarkably well by the combination of two effects: the cosmological growth of structure and the evolution of the molecular gas fraction in galaxies. We conclude that the powerful starbursts in SMGs likely represent a short-lived but universal phase in massive galaxy evolution, associated with the transition between cold gas-rich, star-forming galaxies and passively evolving systems