2,538 research outputs found
FIRBACK: II. Data Reduction and Calibration of the 170 micron ISO Deep Cosmological Survey
We present the final reduction and calibration of the FIRBACK ISOPHOT data.
FIRBACK is a deep cosmological survey performed at 170 microns. This paper
deals with the ISOPHOT C200 camera with the C160 filter. We review the whole
data reduction process and compare our final calibration with DIRBE (for the
extended emission) and IRAS (for point sources). The FIRBACK source extraction
and galaxy counts is discussed in a companion paper (Dole et al., 2001).Comment: Accepted for publication in A&A. 9 pages, includes new aa.cls. Also
available (with better quality figures) at http://wwwfirback.ias.u-psud.fr
and http://mips.as.arizona.edu/~hdole/firback (new aa.cls is here
Field theoretic calculation of the surface tension for a model electrolyte system
We carry out the calculation of the surface tension for a model electrolyte
to first order in a cumulant expansion about a free field theory equivalent to
the Debye-H\"uckel approximation. In contrast with previous calculations, the
surface tension is calculated directly without recourse to integrating
thermodynamic relations. The system considered is a monovalent electrolyte with
a region at the interface, of width h, from which the ionic species are
excluded. In the case where the external dielectric constant epsilon_0 is
smaller than the electrolyte solution's dielectric constant epsilon we show
that the calculation at this order can be fully regularized. In the case where
h is taken to be zero the Onsager-Samaras limiting law for the excess surface
tension of dilute electrolyte solutions is recovered, with corrections coming
from a non-zero value of epsilon_0/epsilon.Comment: LaTeX, 14 pages, 3 figures, 1 tabl
Proportional Reasoning as Essential Numeracy
This paper reports an aspect of a large research and development project that aimed to promote middle years school teachersâ understanding and awareness of the pervasiveness of proportional reasoning as integral to numeracy. Teacher survey data of proportional reasoning across the curriculum were mapped on to a rich model of numeracy. Results provided evidence of extensive and creative teaching of proportional reasoning in all learning areas. The capacity of such tasks and activities for promoting student numeracy is theorised
Promoting middle school studentsâ proportional reasoning skills through an ongoing professional development programme for teachers
© 2016, Springer Science+Business Media Dordrecht. Proportional reasoning, the ability to use ratios in situations involving comparison of quantities, is essential for mathematical competence, especially in the middle school years, and is an important determinant of success beyond school. Research shows students find proportional reasoning and its foundational concepts difficult. Proportional reasoning does not always develop naturally, however some research suggests that with targeted teaching, its development can be promoted. This paper reports on a large Australian study involving over 130 teachers and their students. A major goal of the study was to investigate the efficacy of ongoing teacher professional development for promoting middle years studentsâ proportional reasoning. A series of professional development workshops was designed to enhance the teachersâ understanding of proportional reasoning and to extend their repertoire of teaching strategies to promote their studentsâ proportional reasoning skills. The workshop design was informed by research literature on proportional reasoning teaching and learning as well as the results of a diagnostic instrument administered to over 2500 middle years students prior to the professional development. Between workshops, the teachers implemented a variety of targeted teaching activities. This paper reports on pre- and post- instrument student data collected at the beginning and end of the first year of the project (i.e., after completion of half of the workshops). The findings suggest that targeted professional development and explicit teaching can make a difference to studentsâ proportional reasoning
Linking stellar mass and star formation in Spitzer/MIPS 24 micron galaxies
We present deep Ks<21.5 (Vega) identifications, redshifts and stellar masses
for most of the sources composing the bulk of the 24 micron background in the
GOODS/CDFS. Our identified sample consists of 747 Spitzer/MIPS 24 micron
objects, and includes ~94% of all the 24 micron sources in the GOODS-South
field which have fluxes Snu(24)>83 microJy (the 80% completeness limit of the
Spitzer/GTO 24 micron catalog). 36% of our galaxies have spectroscopic
redshifts (mostly at z<1.5) and the remaining ones have photometric redshifts
of very good quality, with a median of |dz|=|zspec-zphot|/(1+zspec)=0.02. We
find that MIPS 24 micron galaxies span the redshift range z~0-4, and that a
substantial fraction (28%) lie at high redshifts z>1.5. We determine the
existence of a bump in the redshift distribution at z~1.9, indicating the
presence of a significant population of galaxies with PAH emission at these
redshifts. Massive (M>10^11 Msun) star-forming galaxies at redshifts 2<z<3 are
characterized by very high star-formation rates (SFR>500 Msun/yr), and some of
them are able to construct a mass of 10^10-10^11 Msun in a single burst
lifetime (~0.01-0.1 Gyr). At lower redshifts z<2, massive star-forming galaxies
are also present, but appear to be building their stars on long timescales,
either quiescently or in multiple modest burst-like episodes. At redshifts
z~1-2, the ability of the burst-like mode to produce entire galaxies in a
single event is limited to some lower (M<7x10^10 Msun) mass systems, and it is
basically negligible at z<1. Our results support a scenario where
star-formation activity is differential with assembled stellar mass and
redshift, and where the relative importance of the burst-like mode proceeds in
a down-sizing way from high to low redshifts. (abridged)Comment: Accepted for publication in the ApJ. 19 pages, 10 figures. Uses
emulateap
Multi-wavelength characterisation of z~2 clustered, dusty star forming galaxies discovered by Planck
(abridged) We report the discovery of PHz G95.5-61.6, a complex structure
detected in emission in the Planck all-sky survey that corresponds to two
over-densities of high-redshift galaxies. This is the first source from the
Planck catalogue of high-z candidates that has been completely characterised
with follow-up observations from the optical to the sub-millimetre domain.
Herschel/SPIRE observations at 250, 350 and 500 microns reveal the existence of
five sources producing a 500 microns emission excess that spatially corresponds
to the candidate proto-clusters discovered by Planck. Further observations at
CFHT in the optical bands (g and i) and in the near infrared (J, H and K_s),
plus mid infrared observations with IRAC/Spitzer (at 3.6 and 4.5 microns)
confirm that the sub-mm red excess is associated with an over-density of
colour-selected galaxies. Follow-up spectroscopy of 13 galaxies with
VLT/X-Shooter establishes the existence of two high-z structures: one at z~1.7
(three confirmed member galaxies), the other at z~2.0 (six confirmed members).
This double structure is also seen in the photometric redshift analysis of a
sample of 127 galaxies located inside a circular region of 1'-radius containing
the five Herschel/SPIRE sources, where we found a double-peaked excess of
galaxies at z~1.7 and z~2.0 with respect to the surrounding region. These
results suggest that PHz G95.5-61.6 corresponds to two accreting nodes, not
physically linked to one another, embedded in the large scale structure of the
Universe at z~2 and along the same line-of-sight. In conclusion, the data,
methods and results illustrated in this pilot project confirm that Planck data
can be used to detect the emission from clustered, dusty star forming galaxies
at high-z, and, thus, to pierce through the early growth of cluster-scale
structures.Comment: 15 pages, 13 figures. Accepted for publication in Astronomy and
Astrophysic
Correlated Anisotropies in the Cosmic Far-Infrared Background Detected by MIPS/Spitzer: Constraint on the Bias
We report the detection of correlated anisotropies in the Cosmic Far-Infrared
Background at 160 microns. We measure the power spectrum in the Spitzer/SWIRE
Lockman Hole field. It reveals unambiguously a strong excess above cirrus and
Poisson contributions, at spatial scales between 5 and 30 arcminutes,
interpreted as the signature of infrared galaxy clustering. Using our model of
infrared galaxy evolution we derive a linear bias b=1.74 \pm 0.16. It is a
factor 2 higher than the bias measured for the local IRAS galaxies. Our model
indicates that galaxies dominating the 160 microns correlated anisotropies are
at z~1. This implies that infrared galaxies at high redshifts are biased
tracers of mass, unlike in the local Universe.Comment: ApJ Letters, in pres
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