1,435 research outputs found
Spitzer 70 and 160-micron Observations of the COSMOS Field
We present Spitzer 70 and 160 micron observations of the COSMOS Spitzer
survey (S-COSMOS). The data processing techniques are discussed for the
publicly released products consisting of images and source catalogs. We present
accurate 70 and 160 micron source counts of the COSMOS field and find
reasonable agreement with measurements in other fields and with model
predictions. The previously reported counts for GOODS-North and the
extragalactic First Look Survey are updated with the latest calibration, and
counts are measured based on the large area SWIRE survey to constrain the
bright source counts. We measure an extragalactic confusion noise level of
sigma_c = 9.4+/-3.3 mJy (q=5) for the MIPS 160-micron band based on the deep
S-COSMOS data and report an updated confusion noise level of sigma_c =
0.35+/-0.15 mJy (q=5) for the MIPS 70-micron band.Comment: Accepted AJ, 15 Aug. 2009. Data available at
http://spider.ipac.caltech.edu/staff/frayer/mycosmos/ until released by IRS
Habitable Climates: The Influence of Eccentricity
In the outer regions of the habitable zone, the risk of transitioning into a
globally frozen "snowball" state poses a threat to the habitability of planets
with the capacity to host water-based life. We use a one-dimensional energy
balance climate model (EBM) to examine how obliquity, spin rate, orbital
eccentricity, and ocean coverage might influence the onset of such a snowball
state. For an exoplanet, these parameters may be strikingly different from the
values observed for Earth. Since, for constant semimajor axis, the annual mean
stellar irradiation scales with (1-e^2)^(-1/2), one might expect the greatest
habitable semimajor axis (for fixed atmospheric composition) to scale as
(1-e^2)^(-1/4). We find that this standard ansatz provides a reasonable lower
bound on the outer boundary of the habitable zone, but the influence of
obliquity and ocean fraction can be profound in the context of planets on
eccentric orbits. For planets with eccentricity 0.5, our EBM suggests that the
greatest habitable semimajor axis can vary by more than 0.8 AU (78%!) depending
on obliquity, with higher obliquity worlds generally more stable against
snowball transitions. One might also expect that the long winter at an
eccentric planet's apoastron would render it more susceptible to global
freezing. Our models suggest that this is not a significant risk for Earth-like
planets around Sun-like stars since such planets are buffered by the thermal
inertia provided by oceans covering at least 10% of their surface. Since
planets on eccentric orbits spend much of their year particularly far from the
star, such worlds might turn out to be especially good targets for direct
observations with missions such as TPF-Darwin. Nevertheless, the extreme
temperature variations achieved on highly eccentric exo-Earths raise questions
about the adaptability of life to marginally or transiently habitable
conditions.Comment: References added, text and figures updated, accepted by Ap
Planck's Dusty GEMS: Gravitationally lensed high-redshift galaxies discovered with the Planck survey
We present an analysis of 11 bright far-IR/submm sources discovered through a
combination of the Planck survey and follow-up Herschel-SPIRE imaging. Each
source has a redshift z=2.2-3.6 obtained through a blind redshift search with
EMIR at the IRAM 30-m telescope. Interferometry obtained at IRAM and the SMA,
and optical/near-infrared imaging obtained at the CFHT and the VLT reveal
morphologies consistent with strongly gravitationally lensed sources.
Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 um
and 2 mm, respectively. All objects are bright, isolated point sources in the
18 arcsec beam of SPIRE at 250 um, with spectral energy distributions peaking
either near the 350 um or the 500 um bands of SPIRE, and with apparent
far-infrared luminosities of up to 3x10^14 L_sun. Their morphologies and sizes,
CO line widths and luminosities, dust temperatures, and far-infrared
luminosities provide additional empirical evidence that these are strongly
gravitationally lensed high-redshift galaxies. We discuss their dust masses and
temperatures, and use additional WISE 22-um photometry and template fitting to
rule out a significant contribution of AGN heating to the total infrared
luminosity. Six sources are detected in FIRST at 1.4 GHz. Four have flux
densities brighter than expected from the local far-infrared-radio correlation,
but in the range previously found for high-z submm galaxies, one has a deficit
of FIR emission, and 6 are consistent with the local correlation. The global
dust-to-gas ratios and star-formation efficiencies of our sources are
predominantly in the range expected from massive, metal-rich, intense,
high-redshift starbursts. An extensive multi-wavelength follow-up programme is
being carried out to further characterize these sources and the intense
star-formation within them.Comment: A&A accepte
Far-Infrared Properties of Spitzer-selected Luminous Starbursts
We present SHARC-2 350 micron data on 20 luminous z ~ 2 starbursts with
S(1.2mm) > 2 mJy from the Spitzer-selected samples of Lonsdale et al. and
Fiolet et al. All the sources were detected, with S(350um) > 25 mJy for 18 of
them. With the data, we determine precise dust temperatures and luminosities
for these galaxies using both single-temperature fits and models with power-law
mass--temperature distributions. We derive appropriate formulae to use when
optical depths are non-negligible. Our models provide an excellent fit to the
6um--2mm measurements of local starbursts. We find characteristic
single-component temperatures T1 ~ 35.5+-2.2 K and integrated infrared (IR)
luminosities around 10^(12.9+-0.1) Lsun for the SWIRE-selected sources.
Molecular gas masses are estimated at 4 x 10^(10) Msun, assuming
kappa(850um)=0.15 m^2/kg and a submillimeter-selected galaxy (SMG)-like
gas-to-dust mass ratio. The best-fit models imply >~2 kpc emission scales. We
also note a tight correlation between rest-frame 1.4 GHz radio and IR
luminosities confirming star formation as the predominant power source. The
far-IR properties of our sample are indistinguishable from the purely
submillimeter-selected populations from current surveys. We therefore conclude
that our original selection criteria, based on mid-IR colors and 24 um flux
densities, provides an effective means for the study of SMGs at z ~ 1.5--2.5.Comment: 13 pages, 4 figures, edited to match published version in ApJ 717,
29-39 (2010
The politics of the teaching of reading
Historically, political debates have broken out over how to teach reading in primary schools and infant classrooms. These debates and âreading warsâ have often resulted from public concerns and media reportage of a fall in reading standards. They also reflect the importance placed on learning to read by parents, teachers, employers, and politicians. Public and media-driven controversies over the teaching of reading have resulted in intense public and professional debates over which specific methods and materials to use with beginning readers and with children who have reading difficulties. Recently, such debates have led to a renewed emphasis on reading proficiency and âstandardizedâ approaches to teaching reading and engaging with literacy. The universal acceptance of the importance of learning to read has also led to vested interests in specific methods, reading programmes, and early literacy assessments amongst professional, business, commercial, and parental lobbying groups. This article traces these debates and the resulting growing support for a quantitative reductionist approach to early-reading programmes
PACS Evolutionary Probe (PEP) - A Herschel Key Program
Deep far-infrared photometric surveys studying galaxy evolution and the
nature of the cosmic infrared background are a key strength of the Herschel
mission. We describe the scientific motivation for the PACS Evolutionary Probe
(PEP) guaranteed time key program and its role in the complement of Herschel
surveys, and the field selection which includes popular multiwavelength fields
such as GOODS, COSMOS, Lockman Hole, ECDFS, EGS. We provide an account of the
observing strategies and data reduction methods used. An overview of first
science results illustrates the potential of PEP in providing calorimetric star
formation rates for high redshift galaxy populations, thus testing and
superseeding previous extrapolations from other wavelengths, and enabling a
wide range of galaxy evolution studies.Comment: 13 pages, 12 figures, accepted for publication in A&
Habitable Zones in the Universe
Habitability varies dramatically with location and time in the universe. This
was recognized centuries ago, but it was only in the last few decades that
astronomers began to systematize the study of habitability. The introduction of
the concept of the habitable zone was key to progress in this area. The
habitable zone concept was first applied to the space around a star, now called
the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable
zones have been proposed. We review the historical development of the concept
of habitable zones and the present state of the research. We also suggest ways
to make progress on each of the habitable zones and to unify them into a single
concept encompassing the entire universe.Comment: 71 pages, 3 figures, 1 table; to be published in Origins of Life and
Evolution of Biospheres; table slightly revise
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