3,775 research outputs found
Multiwavelength Observations of one Galaxy in Marano Field
We report the multiwavelength observations of one intermediate redshift
(z=0.3884) galaxy in the Marano Field. These data include ISOCAM middle
infrared, VLT/FORS2 spectroscopic and photometric data, associated with the
ATCA 1.4 GHz radio and ROSAT PSPC X-ray observations from literature. The
Spectral Energy Distribution obtained by VLT spectroscopy exhibits its
early-type galaxy property, while, in the same time, it has obvious [OIII]5007
emission line. The diagnostic diagram from the optical emission line ratios
shows its Seyfert galaxy property. Its infrared-radio relation follows the
correlation of sources detected at 15 \mu and radio. It has a high X-ray
luminosity of 1.26*10^{43} ergs/s, which is much higher than the general
elliptical galaxies s with the similar B band luminosity, and is about 2 orders
of magnitude higher than the derived value from the star forming tracer, the
FIR luminosity. This means that the X-ray sources of this galaxy are not
stellar components, but the AGN is the dominant component.Comment: 6 pages, 1 PS figure and 4 tables. Publication in ChJAA, Suppl., the
Special Issue for The Fifth Microquasar Workshop 2004:
http://chjaa.bao.ac.cn/, 2005, Vol.5, 335-34
Deep Galaxy survey at 6.75 micron with the ISO satellite
Deep 6.75um mid-IR ISOCAM observations were obtained of the Canada-France
Redshift Survey (CFRS) 1415+52 field with the Infrared Space Observatory. The
identification of the sources with optical counterparts is described in detail,
and a classification scheme is devised which depends on the S/N of the
detection and the inverse probability of chance coincidence. 83% of the 54
ISOCAM sources are identified with Iab<23.5 counterparts. The (I-K)ab colors,
radio properties, spectrophotometric properties and frequency of nuclear
activity of these counterparts differ on average from those of typical CFRS
galaxies. CFRS spectra are available for 21 of the sources which have Iab <=
22.5 (including 7 stars). Most of the strongest sources are stars or AGN. Among
the non--stellar counterparts with spectra, 40% are AGNs, and 53% are galaxies
that display star formation activity and/or significant contributions of A
stars. The ISOCAM sources also display an IR excess, even when compared with
heavily-reddened local starburst galaxies. An upper limit of 30% of
extragalactic ISO sources could be at z>1 of the 44 S6.75um > 150uJy sources
which are non-stellar (7 "spectroscopic" and 3 "photometric" stars excluded)Comment: 13 pages, 12 figures. Accepted for publication in A
HST/WFPC2 morphologies and color maps of distant luminous infrared galaxies
Using HST/WFPC2 imaging in F606W (or F450W) and F814W filters, we obtained
the color maps in observed frame for 36 distant (0.4<z<1.2) luminous infrared
galaxies (LIRGs), with average star formation rates of ~100 M_sun/yr. Stars and
compact sources are taken as references to align images after correction of
geometric distortion. This leads to an alignment accuracy of 0.15 pixel, which
is a prerequisite for studying the detailed color properties of galaxies with
complex morphologies. A new method is developed to quantify the reliability of
each pixel in the color map without any bias against very red or blue color
regions.Based on analyses of two-dimensional structure and spatially resolved
color distribution, we carried out morphological classification for LIRGs.
About 36% of the LIRGs were classified as disk galaxies and 22% as irregulars.
Only 6 (17%) systems are obvious ongoing major mergers. An upper limit of 58%
was found for the fraction of mergers in LIRGs with all the possible
merging/interacting systems included. Strikingly, the fraction of compact
sources is as high as 25%, similar to that found in optically selected samples.
From their K band luminosities, LIRGs are relatively massive systems, with an
average stellar mass of about 1.1x10^11 solar mass. They are related to the
formation of massive and large disks, from their morphologies and also from the
fact that they represent a significant fraction of distant disks selected by
their sizes. The compact LIRGs show blue cores, which could be associated with
the formation of the central region of these galaxies. We suggest that there
are many massive disks still forming a large fraction of their stellar mass
since z=1. For most of them, their central parts (bulge?) were formed prior to
the formation of their disks.Comment: 20 pages, 14 figures, accepted for publication in A&
531 new spectroscopic redshifts from the CDFS and a test on the cosmological relevance of the GOODS-South field
(Abbrev.) This paper prepares a series of papers analysing the Intermediate
MAss Galaxy Evolution Sequence (IMAGES) up to z=1. Intermediate mass galaxies
(MJ <=-20.3) are selected from the Chandra Deep Field South (CDFS) for which we
identify a serious lack of spectroscopically determined redshifts..... We have
spectroscopically identified 691 objects including 580 gal., 7 QSOs, and 104
stars. This study provides 531 new redshifts in the CDFS. It confirms the
presence of several large scale structures in the CDFS. To test the impact of
these structures in the GOODS-South field, we ... compare the evolution of
rest-frame U, B, V and K galaxy luminosity densities to that derived from the
CFRS. The CDFS field shows a significant excess of luminosity densities in the
z=0.5-0.75 range, which increases with the wavelength, reaching up to 0.5 dex
at 2.1 um. Stellar mass and specific star formation evolutions might be
significantly affected by the presence of the peculiar large scale structures
at z= 0.668 and at z= 0.735, that contain a significant excess of evolved,
massive galaxies when compared to other fields. This leads to a clear warning
to results based on the CDFS/GOODS South fields, especially those related to
the evolution of red luminosity densities, i.e. stellar mass density and
specific star formation rate. Photometric redshift techniques, when applied to
that field, are producing quantities which are apparently less affected by
cosmic variance (0.25 dex at 2.1 um), however at the cost of the difficulty in
disentangling between evolutionary and cosmic variance effects.Comment: Accepted for publication in A&A, 19 pages, 13 figure
Using resource graphs to represent conceptual change
We introduce resource graphs, a representation of linked ideas used when
reasoning about specific contexts in physics. Our model is consistent with
previous descriptions of resources and coordination classes. It can represent
mesoscopic scales that are neither knowledge-in-pieces or large-scale concepts.
We use resource graphs to describe several forms of conceptual change:
incremental, cascade, wholesale, and dual construction. For each, we give
evidence from the physics education research literature to show examples of
each form of conceptual change. Where possible, we compare our representation
to models used by other researchers. Building on our representation, we
introduce a new form of conceptual change, differentiation, and suggest several
experimental studies that would help understand the differences between
reform-based curricula.Comment: 27 pages, 14 figures, no tables. Submitted for publication to the
Physical Review Special Topics Physics Education Research on March 8, 200
The radiation of cynodonts and the ground plan of mammalian morphological diversity
Cynodont therapsids diversified extensively after the Permo-Triassic mass extinction event, and gave rise to mammals in the Jurassic. We use an enlarged and revised dataset of discrete skeletal characters to build a new phylogeny for all main cynodont clades from the Late Permian to the Early Jurassic, and we analyse models of morphological diversification in the group. Basal taxa and epicynodonts are paraphyletic relative to eucynodonts, and the latter are divided into cynognathians and probainognathians, with tritylodonts and mammals forming sister groups. Disparity analyses reveal a heterogeneous distribution of cynodonts in a morphospace derived from cladistic characters. Pairwise morphological distances are weakly correlated with phylogenetic distances. Comparisons of disparity by groups and through time are non-significant, especially after the data are rarefied. A disparity peak occurs in the Early/Middle Triassic, after which period the mean disparity fluctuates little. Cynognathians were characterized by high evolutionary rates and high diversity early in their history, whereas probainognathian rates were low. Community structure may have been instrumental in imposing different rates on the two clades
Pseudopotential study of binding properties of solids within generalized gradient approximations: The role of core-valence exchange-correlation
In ab initio pseudopotential calculations within density-functional theory
the nonlinear exchange-correlation interaction between valence and core
electrons is often treated linearly through the pseudopotential. We discuss the
accuracy and limitations of this approximation regarding a comparison of the
local density approximation (LDA) and generalized gradient approximations
(GGA), which we find to describe core-valence exchange-correlation markedly
different. (1) Evaluating the binding properties of a number of typical solids
we demonstrate that the pseudopotential approach and namely the linearization
of core-valence exchange-correlation are both accurate and limited in the same
way in GGA as in LDA. (2) Examining the practice to carry out GGA calculations
using pseudopotentials derived within LDA we show that the ensuing results
differ significantly from those obtained using pseudopotentials derived within
GGA. As principal source of these differences we identify the distinct behavior
of core-valence exchange-correlation in LDA and GGA which, accordingly,
contributes substantially to the GGA induced changes of calculated binding
properties.Comment: 13 pages, 6 figures, submitted to Phys. Rev. B, other related
publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm
The skull evolution of oviraptorosaurian dinosaurs: the role of niche-partitioning in diversification
Oviraptorosaurs are bird-like theropod dinosaurs that thrived in the final pre-extinction ecosystems during the latest Cretaceous, and the beaked, toothless skulls of derived species are regarded as some of the most peculiar among dinosaurs. Their aberrant morphologies are hypothesized to have been caused by rapid evolution triggered by an ecological/biological driver, but little is known about how their skull shapes and functional abilities diversified. Here, we use quantitative techniques to study oviraptorosaur skull form and mandibular function. We demonstrate that the snout is particularly variable, that mandibular and upper/lower beak form are significantly correlated with phylogeny, and that there is a strong and significant correlation between mandibular function and mandible/lower beak shape, suggesting a form-function association. The form-function relationship and phylogenetic signals, along with a moderate allometric signal in lower beak form, indicate that similar mechanisms governed beak shape in oviraptorosaurs and extant birds. The two derived oviraptorosaur clades, oviraptorids and caenagnathids, are significantly separated in morphospace and functional space, indicating that they partitioned niches. Oviraptorids coexisting in the same ecosystem are also widely spread in morphological and functional space, suggesting that they finely partitioned feeding niches, whereas caenagnathids exhibit extreme disparity in beak size. The diversity of skull form and function was likely key to the diversification and evolutionary success of oviraptorosaurs in the latest Cretaceous. [Abstract copyright: © 2019 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2019 European Society For Evolutionary Biology.
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