2,634 research outputs found
A Biographical Sketch of John Greenleaf Whittier from The Early Poems of John Greenleaf Whittier
Biographical sketch from The Early Poems of John Greenleaf Whittier. Spine title Whittier\u27s Poetical Works. Biographical sketch written by N. H. Dole. Pages ix-xxxii. Portrait of Whittier included.https://digitalcommons.georgefox.edu/quakerbooks/1040/thumbnail.jp
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
Infrared Spectral Energy Distributions of z~0.7 Star-Forming Galaxies
We analyze the infrared (IR) spectral energy distributions (SEDs) for
10micron < lambda(rest) < 100micron for ~600 galaxies at z~0.7 in the extended
Chandra Deep Field South by stacking their Spitzer 24, 70 and 160micron images.
We place interesting constraints on the average IR SED shape in two bins: the
brightest 25% of z~0.7 galaxies detected at 24micron, and the remaining 75% of
individually-detected galaxies. Galaxies without individual detections at
24micron were not well-detected at 70micron and 160micron even through
stacking. We find that the average IR SEDs of z~0.7 star-forming galaxies fall
within the diversity of z~0 templates. While dust obscuration Lir/Luv seems to
be only a function of star formation rate (SFR; ~ Lir+Luv), not of redshift,
the dust temperature of star-forming galaxies (with SFR ~ 10 solar mass per
year) at a given IR luminosity was lower at z~0.7 than today. We suggest an
interpretation of this phenomenology in terms of dust geometry: intensely
star-forming galaxies at z~0 are typically interacting, and host dense
centrally-concentrated bursts of star formation and warm dust temperatures. At
z~0.7, the bulk of intensely star-forming galaxies are relatively undisturbed
spirals and irregulars, and we postulate that they have large amounts of
widespread lower-density star formation, yielding lower dust temperatures for a
given IR luminosity. We recommend what IR SEDs are most suitable for modeling
intermediate redshift galaxies with different SFRs.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in Ap
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
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
325-MHz observations of the ELAIS-N1 field using the Giant Metrewave Radio Telescope
We present observations of the European Large-Area {\it ISO} Survey-North 1
(ELAIS-N1) at 325 MHz using the Giant Metrewave Radio Telescope (GMRT), with
the ultimate objective of identifying active galactic nuclei and starburst
galaxies and examining their evolution with cosmic epoch. After combining the
data from two different days we have achieved a median rms noise of Jy beam, which is the lowest that has been achieved at this
frequency. We detect 1286 sources with a total flux density above Jy. In this paper, we use our deep radio image to examine the spectral
indices of these sources by comparing our flux density estimates with those of
Garn et al. at 610 MHz with the GMRT, and surveys with the Very Large Array at
1400 MHz. We attempt to identify very steep spectrum sources which are likely
to be either relic sources or high-redshift objects as well as inverted-spectra
objects which could be Giga-Hertz Peaked Spectrum objects. We present the
source counts, and report the possibility of a flattening in the normalized
differential counts at low flux densities which has so far been reported at
higher radio frequencies.Comment: The paper contains 15 figures and 5 tables. Accepted for publication
in MNRA
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