3,583 research outputs found
Finding bright <i>z</i> ≥ 6.6 Ly <i>α</i> emitters with lensing: prospects for <i>Euclid</i>
We model the Ly luminosity function to estimate the
number of lensed high Ly emitters that may be detected by the
Euclid Deep Survey. To span the whole range of possible predictions we exploit
two Ly luminosity function models and two strong gravitational lensing
models from the literature. We show that the planned Euclid Deep Survey
observing 40 deg over the 920-1850 nm wavelength range down to a flux limit
of erg scm will enable us to find
between and deg lensed Ly emitters at depending on the adopted Ly luminosity function and strong
gravitational lensing model. The obvious [OII], [OIII] and H
contaminants of the Ly lensed population will be identified with the
help of Euclid's spectral resolving power, while the SKA will enable the
identification of the interloper population of H emitters. By combining
Euclid and the SKA, we will thus be able to identify, for the first time, a
sample of to lensed Ly emitters at .Comment: Accepted for publication in MNRAS on 20 June 2017. (NEW: Amended
Latex
A population of extreme mid-to-near-infrared sources: obscured AGN and dusty starbursts
We present a sample of mid-infrared detected sources from the European Large
Area ISO Survey (ELAIS) regions characterised by strong mid-IR radiation with
faint near-IR and optical counterparts. These extreme mid-to-near-IR objects
(EMNOs) are defined here by a flux ratio of f_15um / f_2.2um > 25. This
population is not obvious in deeper small area ISO surveys, though it produces
more than 20% of the observed cosmic IR background radiation (CIRB) at 15um
above 1 mJy. Near-future large area deep mid-IR surveys with the Spitzer Space
Telescope, however, are bound to uncover large amounts of these objects, which
we argue to most likely be obscured AGN, based on SED shapes and X-ray data.
Very strong dusty starbursts at z>1 may also have high mid-to-near-IR flux
ratios, but using the MIR/NIR and FIR/MIR ratios these may be separated. Most
of our EMNOs appear to be ULIRGs, half are also extremely red objects (ERO). A
curious case of a low redshift, less luminous object with a very young stellar
population is also found. We predict that the simple broad band selection
method makes EMNOs a useful window into high-redshift obscured nuclear activity
and its sought after relation to star-formation, in a similar way that EROs
have been used to define samples of high-redshift early type galaxies.Comment: 8 pages, 3 figures. A&A accepted version. Results unchanged but
discussion is significantly expande
A Simplified Model for Estimating Household Air Pollution in Challenging Contexts: A Case Study from Ghana
Almost three billion people rely primarily on inefficient and polluting cooking systems worldwide. Household air pollution is a direct consequence of this practice, and it is annually associated with millions of premature deaths and diseases, mainly in low- and lower-middle-income countries. The use of improved cookstoves often represents an appropriate solution to reduce such health risks. However, in the distribution of such units, it can be necessary to prioritize the beneficiaries. Thus, in this study, we conducted field research involving five rural villages in the Northern part of Ghana, where using three-stone fires or rural stoves was common. Concentrations of PM2.5, PM10, and carbon monoxide (CO) were measured indoors and outdoors. Considering each field mission lasted less than 24 h, assumptions were made so as to calculate the average pollutant concentrations in 24 h through a new, simplified equation that combined efficiency and cost-savings by shortening field assessments. The obtained values were compared with international guidelines. The results showed that PM2.5 and PM10 limits were overstepped in two villages, which should thus be prioritized. However, further research will be necessary to strengthen and validate our proposed equation, which must be seen as a starting point
Solid Waste Management in Rural Communities of Developing Countries: An Overview of Challenges and Opportunities
Solid waste management (SWM) in rural areas of many low- and middle-income countries (LMICs) represents a critical and underrated topic. However, almost half of the world's population still lives in rural areas and an adequate SWM is crucial in reducing environmental and health threats. A lack of knowledge and appropriate tools often leads to inappropriate practices such as waste dumping and uncontrolled burning. However, appropriate methods can transform waste into resources and even guarantee a revenue source. This manuscript provides an overview of the state of the knowledge characterising SWM in rural communities of LMICs, analysing common practices and principal issues. Different solid waste fractions are considered. Virtuous approaches are presented, taking into account recent sustainable solutions. Considering that a relevant part of the world population is still living in rural areas, the benefits associated with an appropriate SWM may be enormous. Such activities may improve local conditions from social, environmental and health perspectives; furthermore, they may have a global impact on facing climate change and environmental pollution
The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic
This paper is part of a series discussing the results obtained in the
framework of a wide international collaboration - the Lockman Hole Project -
aimed at improving the extensive multiband coverage available in the Lockman
Hole region, through novel deep, wide-area, multifrequency (60, 150, 350 MHz,
and 1.4 GHz) radio surveys. This multifrequency, multi-band information will be
exploited to get a comprehensive view of star formation and active galactic
nucleus activities in the high-redshift Universe from a radio perspective. In
this paper, we present novel 1.4 GHz mosaic observations obtained with the
Westerbork Synthesis Radio Telescope. With an area coverage of 6.6 deg2, this
is the largest survey reaching an rms noise of 11 uJy/beam. In this paper, we
present the source catalogue (~6000 sources with flux densities S>55 uJy
(5sigma), and we discuss the 1.4 GHz source counts derived from it. Our source
counts provide very robust statistics in the flux range 0.1<S<1 mJy, and are in
excellent agreement with other robust determinations obtained at lower and
higher flux densities. A clear excess is found with respect to the counts
predicted by the semi-empirical radio sky simulations developed in the
framework of the Square Kilometre Array Simulated Skies project. A preliminary
analysis of the identified (and classified) sources suggests this excess is to
be ascribed to star-forming galaxies, which seem to show a steeper evolution
than predicted.Comment: accepted for publication on MNRAS. New version that corrects latex
errors and contain the correct version of figure 1
Evolution of the far-infrared luminosity functions in the Spitzer Wide-area Infrared Extragalactic Legacy Survey
We present new observational determination of the evolution of the rest-frame
70 and 160 micron and total infrared (TIR) galaxy luminosity functions (LFs)
using 70 micron data from the Spitzer Wide-area Infrared Extragalactic Legacy
Survey (SWIRE). The LFs were constructed for sources with spectroscopic
redshifts only in the XMM-LSS and Lockman Hole fields from the SWIRE
photometric redshift catalogue. The 70 micron and TIR LFs were constructed in
the redshift range 0<z<1.2 and the 160 micron LF was constructed in the
redshift range 0<z<0.5 using a parametric Bayesian and the vmax methods. We
assume in our models, that the faint-end power-law index of the LF does not
evolve with redshifts. We find the the double power-law model is a better
representation of the IR LF than the more commonly used power-law and Gaussian
model. We model the evolution of the FIR LFs as a function of redshift where
where the characteristic luminosity, evolve as
\propto(1+z)^{\alpha_\textsc{l}}. The rest-frame 70 micron LF shows a strong
luminosity evolution out to z=1.2 with alpha_l=3.41^{+0.18}_{-0.25}. The
rest-frame 160 micron LF also showed rapid luminosity evolution with
alpha_l=5.53^{+0.28}_{-0.23} out to z=0.5. The rate of evolution in luminosity
is consistent with values estimated from previous studies using data from IRAS,
ISO and Spitzer. The TIR LF evolves in luminosity with
alpha_l=3.82^{+0.28}_{-0.16} which is in agreement with previous results from
Spitzer 24 micron which find strong luminosity evolution. By integrating the LF
we calculated the co-moving IR luminosity density out to z=1.2, which confirm
the rapid evolution in number density of LIRGs and ULIRGs which contribute
~68^{+10}_{-07} % to the co-moving star formation rate density at z=1.2. Our
results based on 70 micron data confirms that the bulk of the star formation at
z=1 takes place in dust obscured objects.Comment: 17 pages, 14 figure
The Stripe 82 1-2 GHz Very Large Array Snapshot Survey: Multiwavelength Counterparts
We have combined spectrosopic and photometric data from the Sloan Digital Sky
Survey (SDSS) with GHz radio observations, conducted as part of the
Stripe 82 GHz Snapshot Survey using the Karl G. Jansky Very Large Array
(VLA), which covers sq degrees, to a flux limit of 88 Jy rms.
Cross-matching the radio source components with optical data via
visual inspection results in a final sample of cross-matched objects,
of which have spectroscopic redshifts and objects have
photometric redshifts. Three previously undiscovered Giant Radio Galaxies
(GRGs) were found during the cross-matching process, which would have been
missed using automated techniques. For the objects with spectroscopy we
separate radio-loud Active Galactic Nuclei (AGN) and star-forming galaxies
(SFGs) using three diagnostics and then further divide our radio-loud AGN into
the HERG and LERG populations. A control matched sample of HERGs and LERGs,
matched on stellar mass, redshift and radio luminosity, reveals that the host
galaxies of LERGs are redder and more concentrated than HERGs. By combining
with near-infrared data, we demonstrate that LERGs also follow a tight
relationship. These results imply the LERG population are hosted by population
of massive, passively evolving early-type galaxies. We go on to show that
HERGs, LERGs, QSOs and star-forming galaxies in our sample all reside in
different regions of a WISE colour-colour diagram. This cross-matched sample
bridges the gap between previous `wide but shallow' and `deep but narrow'
samples and will be useful for a number of future investigations.Comment: 17 pages, 19 figures. Resubmitted to MNRAS after the initial comment
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