156 research outputs found
Follow-up of victims of one terrorist attack
Abstract The first aim of the study was to examine the relationships between acute stress reactions and post-traumatic reactions following exposure to a terrorist attack. The second was to examine whether exposure to a terrorist attack increases the perceived threat and fear of renewed Iraqi missile attacks. Data were collected at two points in time: during the first month after the exposure to a terrorist attack (N = 54), and four months later (N = 44). Twenty-four percent of the exposed group had acute stress disorder (ASD), and a similar percentage had PTSD. Among participants who had ASD, the chances of developing PTSD were three times greater than among those who had never experienced ASD. Among participants who had been exposed to a terrorist attack and developed PTSD, the perceived threat of an Iraqi missile attack was greater than among those who had been exposed to a terrorist attack but did not develop PTSD, or among the participants in the control group. The discussion deals with the findings in light of the current controversy regarding ASD and the current situation in Israel
Cosmological Implications of Lyman-Break Galaxy Clustering
We review our analysis of the clustering properties of ``Lyman-break''
galaxies (LBGs) at redshift z~3, previously discussed in Wechsler et al (1998).
We examine the likelihood of spikes found by Steidel et al (1998) in the
redshift distribution of LBGs, within a suite of models for the evolution of
structure in the Universe. Using high-resolution dissipationless N-body
simulations, we analyze deep pencil-beam surveys from these models in the same
way that they are actually observed, identifying LBGs with the most massive
dark matter halos. We find that all the models (with SCDM as a marginal
exception) have a substantial probability of producing spikes similar to those
observed, because the massive halos are much more clumped than the underlying
matter -- i.e., they are biased. Therefore, the likelihood of such a spike is
not a good discriminator among these models. The LBG correlation functions are
less steep than galaxies today (gamma~1.4), but show similar or slightly longer
correlation lengths. We have extened this analysis and include a preliminary
comparison to the new data presented in Adelberger et al (1998). We also
discuss work in progress, in which we use semi-analytic models to identify
Lyman-break galaxies within dark-matter halos.Comment: 4 pages, 2 figures, Latex, uses aipproc.sty; to appear in the
proceedings of the 9th Annual October Maryland Astrophysics Conference,
"After the Dark Ages: When the Galaxies Were Young (the Universe at 2<z<5)
Strong Evolution in the Luminosity-Velocity Relation at z>1?
We present a method for constraining the evolution of the galaxy
luminosity-velocity (LV) relation in hierarchical scenarios of structure
formation. The comoving number density of dark-matter halos with circular
velocity of 200 km/s is predicted in favored CDM cosmologies to be nearly
constant over the redshift range 0<z<5. Any observed evolution in the density
of bright galaxies implies in turn a corresponding evolution in the LV
relation. We consider several possible forms of evolution for the zero-point of
the LV relation and predict the corresponding evolution in galaxy number
density. The Hubble Deep Field suggests a large deficit of bright (M_V < -19)
galaxies at 1.4 < z < 2. If taken at face value, this implies a dimming of the
LV zero-point by roughly 2 magnitudes. Deep, wide-field, near-IR selected
surveys will provide more secure measurements to compare with our predictions.Comment: 4 pages, 2 figures. Submitted to ApJ Letter
Long-term adjustment among Israeli war veterans: The role of attachment style
This study examines the role of attachment in the long-term adjustment of Israeli veterans. The sample of participants comprised three groups of Israeli veterans who fought in the 1973 Yom Kippur War: 112 combat stress reaction (CSR) casualties, 98 veterans who received medals for bravery, and 189 controls. The CSR casualties reported higher levels of emotional distress than did participants in the two other groups. CSR veterans also showed the lowest levels of secure attachment characteristics. Additionally, the findings revealed different relationships between the avoidant style of attachment and emotional distress measures across the research groups. The implications of these findings are discussed according to two theoretical models of attachment
Linking galaxy structural properties and star formation activity to black hole activity with IllustrisTNG
We study the connection between active galactic nuclei (AGN) and their host
galaxies through cosmic time in the large-scale cosmological IllustrisTNG
simulations. We first compare BH properties, i.e. the hard X-ray BH luminosity
function, AGN galaxy occupation fraction, and distribution of Eddington ratios,
to available observational constraints. The simulations produce a population of
BHs in good agreement with observations, but we note an excess of faint AGN in
hard X-ray (L_x ~ 10^{43-44} erg/s), and a lower number of bright AGN
(L_x>10^{44} erg/s), a conclusion that varies quantitatively but not
qualitatively with BH luminosity estimation method. The lower Eddington ratios
of the 10^{9} Msun BHs compared to observations suggest that AGN feedback may
be too efficient in this regime. We study galaxy star formation activity and
structural properties, and design sample-dependent criteria to identify
different galaxy types (star-forming/quiescent, extended/compact) that we apply
both to the simulations and observations from the candels fields. We analyze
how the simulated and observed galaxies populate the specific star formation
rate - stellar mass surface density diagram. A large fraction of the z=0
M_{star}>10^{11} Msun quiescent galaxies first experienced a compaction phase
(i.e. reduction of galaxy size) while still forming stars, and then a quenching
event. We measure the dependence of AGN fraction on galaxies' locations in this
diagram. After correcting the simulations with a redshift and AGN
luminosity-dependent model for AGN obscuration, we find good qualitative and
quantitative agreement with observations. The AGN fraction is the highest among
compact star-forming galaxies (16-20% at z~1.5-2), and the lowest among compact
quiescent galaxies (6-10% at z~1.5-2).Comment: 35 pages, 22 figures, accepted for publication in MNRA
The relationship between galaxy and dark matter halo size from z ∼ 3 to the present
We explore empirical constraints on the statistical relationship between the radial size of galaxies and the radius of their host dark matter haloes from z similar to 0.1-3 using the Galaxy And Mass Assembly (GAMA) and Cosmic Assembly Near Infrared Deep Extragalactic Legacy Survey (CANDELS) surveys. We map dark matter halo mass to galaxy stellar mass using relationships from abundance matching, applied to the Bolshoi-Planck dissipationless N-body simulation. We define SRHR equivalent to r(e)/R-h as the ratio of galaxy radius to halo virial radius, and SRHR lambda equivalent to r(e)/(lambda R-h) as the ratio of galaxy radius to halo spin parameter times halo radius. At z similar to 0.1, we find an average value of SRHR similar or equal to 0.018 and SRHR. similar or equal to 0.5 with very little dependence on stellar mass. Stellar radius-halo radius (SRHR) and SRHR lambda have a weak dependence on cosmic time since z similar to 3. SRHR shows a mild decrease over cosmic time for low-mass galaxies, but increases slightly or does not evolve formoremassive galaxies. We find hints that at high redshift (z similar to 2-3), SRHR. is lower for more massive galaxies, while it shows no significant dependence on stellar mass at z less than or similar to 0.5. We find that for both the GAMA and CANDELS samples, at all redshifts from z similar to 0.1-3, the observed conditional size distribution in stellar mass bins is remarkably similar to the conditional distribution of lambda R-h. We discuss the physical interpretation and implications of these results
Evaluating Semi-Analytic Halo Merging Histories
We evaluate the accuracy of semi-analytic merger-trees by comparing them with
the merging histories of dark-matter halos in N-body simulations, focusing on
the joint distribution of the number of progenitors and their masses. We first
confirm that the halo mass function as predicted directly by the
Press-Schechter (PS) model deviates from the simulations by up to 50% depending
on the mass scale and redshift, while the means of the projected distributions
of progenitor number and mass for a halo of a given mass are more accurately
predicted by the Extended PS model. We then use the full merger trees to study
the joint distribution as a function of redshift and parent-halo mass. We find
that while the deviation of the mean quantities due to the inaccuracy of the
Extended PS model partly propagates into the higher moments of the
distribution, the merger-tree procedure does not introduce a significant
additional source of error. In particular, certain properties of the merging
history such as the mass ratio of the progenitors and the total accretion rate
are reproduced quite accurately for galaxy sized halos (\sim 10^{12}\msun),
and less so for larger masses. We conclude that although there could be deviations in the absolute numbers and masses of progenitors and in the
higher order moment of these distributions, the relative properties of
progenitors for a given halo are reproduced fairly well by the merger trees.
They can thus provide a useful framework for modelling galaxy formation once
the above-mentioned limitations are taken into account.Comment: 10 pages including 9 figures, submitted to MNRA
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