3,096 research outputs found
Galaxy Morphological Segregation in Clusters: Local vs. Global Conditions
We study the relative fraction of galaxy morphological types in clusters, as
a function of the projected local galaxy density and different global
parameters: cluster projected gas density, cluster projected total mass density
, and reduced clustercentric distance. Since local and global densities are
correlated, we have considered different tests to search for the parameters to
which segregation show the strongest dependence. Also, we have explored the
results of our analysis applied to the central regions of the clusters and
their outskirts. We consider a sample of clusters of galaxies with temperature
estimates to derive the projected mass density profile and the 500 density
contrast radius () using the NFW model and the scaling relation
respectively. The X-ray surface brightness profiles are used to obtain the
projected gas density assuming the hydrostatic equilibrium model. Our results
suggest that the morphological segregation in clusters is controlled by the
local galaxy density in the outskirts. On the other hand, the global projected
mass density, shows the strongest correlation with the fraction of
morphological types in the central high density region, with a marginal
dependence on the local galaxy density.Comment: 10 pages, 8 figures, Accepted AJ (February 2001 issue
On the relation between standard and -symmetries for PDEs
We give a geometrical interpretation of the notion of -prolongations of
vector fields and of the related concept of -symmetry for partial
differential equations (extending to PDEs the notion of -symmetry for
ODEs). We give in particular a result concerning the relationship between
-symmetries and standard exact symmetries. The notion is also extended to
the case of conditional and partial symmetries, and we analyze the relation
between local -symmetries and nonlocal standard symmetries.Comment: 25 pages, no figures, latex. to be published in J. Phys.
Developmental Changes in Conflict Resolution Styles in Parent–Adolescent Relationships: A Four-Wave Longitudinal Study
In this study, changes in three conflict resolution styles in parent–adolescent relationships were investigated: positive problem solving, conflict engagement, and withdrawal. Questionnaires about these conflict resolution styles were completed by 314 early adolescents (M = 13.3 years; 50.6% girls) and both parents for four consecutive years. Adolescents’ reported use of positive problem solving increased with mothers, but did not change with fathers. Fathers reported an increase of positive problem solving with adolescents, whereas mothers reported no change. Adolescents’ use of conflict engagement was found to temporarily increase with mothers, but showed no change with fathers. Mothers and fathers reported a decrease in conflict engagement with adolescents. Adolescents’ use of withdrawal with parents increased, although this increase was temporarily with mothers. Mothers reported no change in withdrawal, whereas fathers’ use of withdrawal increased. Generally, we found that both adolescents and their parents changed in their use of conflict resolution from early to middle adolescence. These results show that conflict resolution in parent–adolescent relationships gradually change in favor of a more horizontal relationship
Redshifts in the Southern Abell Redshift Survey Clusters. I. The Data
The Southern Abell Redshift Survey contains 39 clusters of galaxies with
redshifts in the range 0.0 < z < 0.31 and a median redshift depth of z =
0.0845. SARS covers the region 0 21h (while
avoiding the LMC and SMC) with b > 40. Cluster locations were chosen from the
Abell and Abell-Corwin-Olowin catalogs while galaxy positions were selected
from the Automatic Plate Measuring Facility galaxy catalog with
extinction-corrected magnitudes in the range 15 <= b_j < 19. SARS utilized the
Las Campanas 2.5 m duPont telescope, observing either 65 or 128 objects
concurrently over a 1.5 sq deg field. New redshifts for 3440 galaxies are
reported in the fields of these 39 clusters of galaxies.Comment: 20 pages, 5 figures, accepted for publication in the Astronomical
Journal, Table 2 can be downloaded in its entirety from
http://trotsky.arc.nasa.gov/~mway/SARS1/sars1-table2.cs
Galaxy groups in the 2dF redshift survey: Galaxy Spectral Type Segregation in Groups
The behaviour of the relative fraction of galaxies with different spectral
types in groups is analysed as a function of projected local galaxy density and
the group-centric distance. The group sample was taken from the 2dF Group
Galaxy Calatogue constructed by Merch\'an & Zandivarez. Our group sample was
constrained to have a homogeneous virial mass distribution with redshift.
Galaxies belonging to this group sample were selected in order to minimize
possible biases such as preferential selection of high luminosity objects. We
find a clear distinction between high virial mass groups (M_V\gsim 10^{13.5}
M_{\odot}) and the less massive ones. While the massive groups show a
significant dependence of the relative fraction of low star formation galaxies
on local galaxy density and group-centric radius,groups with lower masses show
no significant trends. We also cross-correlate our group subsample with the
previously identified clusters finding that this sample shows a very similar
behaviour as observed in the high virial mass group subsample.Comment: 3 figures replaced, accepted for publication in MNRA
Chaos and Universality in a Four-Dimensional Spin Glass
We present a finite size scaling analysis of Monte Carlo simulation results
on a four dimensional Ising spin glass. We study chaos with both coupling and
temperature perturbations, and find the same chaos exponent in each case. Chaos
is investigated both at the critical temperature and below where it seems to be
more efficient (larger exponent). Dimension four seems to be above the critical
dimension where chaos with temperature is no more present in the critical
region. Our results are consistent with the Gaussian and bimodal coupling
distributions being in the same universality class.Comment: 11 pages, including 6 postscript figures. Latex with revtex macro
Nonlocal aspects of -symmetries and ODEs reduction
A reduction method of ODEs not possessing Lie point symmetries makes use of
the so called -symmetries (C. Muriel and J. L. Romero, \emph{IMA J.
Appl. Math.} \textbf{66}, 111-125, 2001). The notion of covering for an ODE
is used here to recover -symmetries of as
nonlocal symmetries. In this framework, by embedding into a
suitable system determined by the function ,
any -symmetry of can be recovered by a local symmetry of
. As a consequence, the reduction method of Muriel and
Romero follows from the standard method of reduction by differential invariants
applied to .Comment: 13 page
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