912 research outputs found
Letter from C. O. Mailloux to E. E. Gilbert, General Electric Company
https://digitalcommons.salve.edu/ochre-court/1168/thumbnail.jp
A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images. I Method description
We present a new non-parametric method to quantify morphologies of galaxies
based on a particular family of learning machines called support vector
machines. The method, that can be seen as a generalization of the classical CAS
classification but with an unlimited number of dimensions and non-linear
boundaries between decision regions, is fully automated and thus particularly
well adapted to large cosmological surveys. The source code is available for
download at http://www.lesia.obspm.fr/~huertas/galsvm.html To test the method,
we use a seeing limited near-infrared ( band, ) sample observed
with WIRCam at CFHT at a median redshift of . The machine is trained
with a simulated sample built from a local visually classified sample from the
SDSS chosen in the high-redshift sample's rest-frame (i band, ) and
artificially redshifted to match the observing conditions. We use a
12-dimensional volume, including 5 morphological parameters and other
caracteristics of galaxies such as luminosity and redshift. We show that a
qualitative separation in two main morphological types (late type and early
type) can be obtained with an error lower than 20% up to the completeness limit
of the sample () which is more than 2 times better that what would
be obtained with a classical C/A classification on the same sample and indeed
comparable to space data. The method is optimized to solve a specific problem,
offering an objective and automated estimate of errors that enables a
straightforward comparison with other surveys.Comment: 11 pages, 7 figures, 3 tables. Submitted to A&A. High resolution
images are available on reques
Property Maps Wilton Maine
Property maps of the Town of Wilton, Maine. Originally mapped by James W. Sewall Company of Old Town, Maine, April 1953. Revised in 2000 by John E. O\u27Donnell & Associates
A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images. II. Quantifying morphological k-correction in the COSMOS field at 1<z<2: Ks band vs. I band
We quantify the effects of \emph{morphological k-correction} at by
comparing morphologies measured in the K and I-bands in the COSMOS area.
Ks-band data have indeed the advantage of probing old stellar populations for
, enabling a determination of galaxy morphological types unaffected by
recent star formation. In paper I we presented a new non-parametric method to
quantify morphologies of galaxies on seeing limited images based on support
vector machines. Here we use this method to classify
selected galaxies in the COSMOS area observed with WIRCam at CFHT. The obtained
classification is used to investigate the redshift distributions and number
counts per morphological type up to and to compare to the results
obtained with HST/ACS in the I-band on the same objects from other works. We
associate to every galaxy with and a probability between 0 and
1 of being late-type or early-type. The classification is found to be reliable
up to . The mean probability is . It decreases with redshift
and with size, especially for the early-type population but remains above
. The classification is globally in good agreement with the one
obtained using HST/ACS for . Above , the I-band classification
tends to find less early-type galaxies than the Ks-band one by a factor
1.5 which might be a consequence of morphological k-correction effects.
We argue therefore that studies based on I-band HST/ACS classifications at
could be underestimating the elliptical population. [abridged]Comment: accepted for publication in A&A, updated with referee comments, 12
pages, 10 figure
Morphological evolution of z~1 galaxies from deep K-band AO imaging in the COSMOS deep field
We present the results of an imaging programme of distant galaxies (z~0.8) at
high spatial resolution (~0.1").We observed 7 fields of 1'*1' with the NACO
Adaptive Optics system (VLT) in Ks (2.16um) band with typical V ~ 14 guide
stars and 3h integration time per field. Observed fields are selected within
the COSMOS survey area. High angular resolution K-band data have the advantage
to probe old stellar populations in the rest-frame, enabling to determine
galaxy morphological types unaffected by recent star formation, better linked
to the underlying mass than classical optical morphology studies (HST).
Adaptive optics on ground based telescopes is the only method today to obtain
such high resolution in the K-band. In this paper we show that reliable results
can be obtained and establish a first basis for larger observing programmes. We
analyze the morphologies by means of B/D (Bulge/Disk) decomposition with GIM2D
and CAS (Concentration-Asymmetry) estimators for 79 galaxies with magnitudes
between Ks = 17-23 and classify them in three main morphological types (Late
Type, Early Type and Irregulars). We obtain for the first time an estimate of
the distribution of galaxy types at redshift z ~ 1 as measured from the near
infrared at high spatial resolution. We show that galactic parameters (disk
scale length, bulge effective radius and bulge fraction) can be estimated with
a random error lower than 20% for the bulge fraction up to Ks = 19 (AB = 21)
and that classification into the three main morphological types can be done up
to Ks = 20 (AB = 22) with at least 70% of correct identifications. We used the
known photometric redshifts to obtain a redshift distribution over 2 redshift
bins (z < 0.8, 0.8 < z < 1.5) for each morphological type.Comment: 19 pages, 19 figures, 5 tables, Accepted for publication in A&A,
typos corrected, referee's suggestions added, figure 3 has been strongly
degrade
Erratic fruit set in almond under warm climates
The cause for the erratic yields of the two main almond cultivars grown in Morocco has been searched in order to recommend possible solutions for a high and stable production. The lack of sufficient bloom overlap between âMarconaâ and âFournat de BrĂ©zenaudâ in many years may be one of the reasons of this erratic behavior, but not the only one, as the same behaviour may be observed in two simultaneously blooming cultivars, âFerragnĂšsâ and âFerraduelâ. The relatively high temperatures observed during the blooming periodsignificantly reduced the stigma receptivity of these cultivars and, as a consequence, their effective pollination period, showing that stigmatic receptivity is a limiting factor for fruit set in âMarconaâ and âFerragnĂšsâ and their subsequent yield reduction under warm conditions. Thus, in the present context of global warming, the search for cultivars tolerant to heat stress during flowering will acquire a special interest, as well as the combination of cultivars with the same chilling and heat requirements to ensure a simultaneous bloom
Erratic fruit set in almond under warm climates
The cause for the erratic yields of the two main almond cultivars grown in Morocco has been searched in order to recommendpossible solutions for a high and stable production. The lack of sufficient bloom overlap between âMarconaâ and âFournat de BrĂ©zenaudâin many years may be one of the reasons of this erratic behavior, but not the only one, as the same behaviour may be observed in twosimultaneously blooming cultivars, âFerragnĂšsâ and âFerraduelâ. The relatively high temperatures observed during the blooming periodsignificantly reduced the stigma receptivity of these cultivars and, as a consequence, their effective pollination period, showing that stigmaticreceptivity is a limiting factor for fruit set in âMarconaâ and âFerragnĂšsâ and their subsequent yield reduction under warm conditions. Thus, inthe present context of global warming, the search for cultivars tolerant to heat stress during flowering will acquire a special interest, as wellas the combination of cultivars with the same chilling and heat requirements to ensure a simultaneous bloom
Stiffness modelling of parallelogram-based parallel manipulators
International audienceThe paper presents a methodology to enhance the stiffness analysis of parallel manipulators with parallelogram-based linkage. It directly takes into account the influence of the external loading and allows computing both the non-linear ``load-deflection" relation and relevant rank-deficient stiffness matrix. An equivalent bar-type pseudo-rigid model is also proposed to describe the parallelogram stiffness by means of five mutually coupled virtual springs. The contributions of this paper are highlighted with a parallelogram-type linkage used in a manipulator from the Orthoglide family
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