351 research outputs found
Clinicians\u27 diagnostic evaluation of chronic childhood trauma disorder : an examination of the clinical utility of developmental trauma : a project based upon an independent investigation
In this study licensed mental health clinicians working with traumatized children and adolescents participated in a mixed method web survey examining professional opinions on the provisional Developmental Trauma Disorder diagnosis submitted for inclusion in the DSM-V. It was found that 88.3% of participating clinicians agreed that the diagnostic criteria for Developmental Trauma Disorder adequately described the symptomatology displayed by their clients with histories of complex trauma. Eighty-six percent of clinicians reported that they would assign their clients a diagnosis of DTD were it available in the current DSM-IV, and 75.5% of those clinicians said they would use DTD in place of one or more of the client\u27s current diagnoses. Interestingly it was also found that symptoms described exclusively by DTD were among the most commonly reported symptoms for chronically traumatized clients. Affect dysregulation, impulsivity, anxious mood, lack of focus and attention, social and relational impairments, physical aggression, and hyperarousal and hypervigilance are all crucial aspects of DTD\u27s diagnostic criteria and were most frequently observed in the traumatized client sample. The results of this study imply that DTD may in fact describe the symptomatology presented by chronically traumatized children and adolescents and may serve as a potentially useful assessment tool in the field of childhood trauma. The inclusion of Developmental Trauma Disorder in the DSM-V is supported by this study\u27s clinical sample and has the potential to lead to more effective treatment interventions and outcomes with this population
Testing Reionization with Gamma Ray Burst Absorption Spectra
We propose to study cosmic reionization using absorption line spectra of
high-redshift Gamma Ray Burst (GRB) afterglows. We show that the statistics of
the dark portions (gaps) in GRB absorption spectra represent exquisite tools to
discriminate among different reionization models. We then compute the
probability to find the largest gap in a given width range [Wmax, Wmax + dW] at
a flux threshold Fth for burst afterglows at redshifts 6.3 < z < 6.7. We show
that different reionization scenarios populate the (Wmax, Fth) plane in a very
different way, allowing to distinguish among different reionization histories.
We provide here useful plots that allow a very simple and direct comparison
between observations and model results. Finally, we apply our methods to GRB
050904 detected at z = 6.29. We show that the observation of this burst
strongly favors reionization models which predict a highly ionized
intergalactic medium at z~6, with an estimated mean neutral hydrogen fraction
xHI = 6.4 \pm 0.3 \times 10^-5 along the line of sight towards GRB 050904.Comment: 5 pages, 3 figures, revised to match the accepted version; major
change: gap statistics is now studied in terms of the flux threshold Fth,
instead of the observed J-band flux FJ; MNRAS in pres
Lyalpha versus X-ray heating in the high-z IGM
In this paper we examine the effect of X-ray and Lyalpha photons on the
intergalactic medium temperature. We calculate the photon production from a
population of stars and micro-quasars in a set of cosmological hydrodynamic
simulations which self-consistently follow the dark matter dynamics, radiative
processes as well as star formation, black hole growth and associated feedback
processes. We find that, (i) IGM heating is always dominated by X-rays unless
the Lyalpha photon contribution from stars in objects with mass M<10^8 Msun
becomes significantly enhanced with respect to the X-ray contribution from BHs
in the same halo (which we do not directly model). (ii) Without overproducing
the unresolved X-ray background, the gas temperature becomes larger than the
CMB temperature, and thus an associated 21 cm signal should be expected in
emission, at z<11.5. We discuss how in such a scenario the transition redshift
between a 21 cm signal in absorption and in emission could be used to
constraint BHs accretion and associated feedback processes.Comment: 7 pages, 3 figures, accepted for publication in MNRA
Measuring Star Formation in Local and Distant Galaxies
I review measurements of star formation in nearby galaxies in the UV-to-FIR
wavelength range, and discuss their impact on SFR determinations in
intermediate and high redshift galaxy populations. Existing and upcoming
facilities will enable precise cross-calibrations among the various indicators,
thus bringing them onto a common scale.Comment: 6 pages, 1 figure; to appear in the Proceedings `A Century of
Cosmology', San Servolo (Venezia, Italy), August 2007, to be published by `Il
Nuovo Cimento
The afterglow and host galaxy of GRB 090205: evidence for a Ly-alpha emitter at z=4.65
Gamma-ray bursts have been proved to be detectable up to distances much
larger than any other astrophysical object, providing the most effective way,
complementary to ordinary surveys, to study the high redshift universe. To this
end, we present here the results of an observational campaign devoted to the
study of the high-z GRB 090205. We carried out optical/NIR spectroscopy and
imaging of GRB 090205 with the ESO-VLT starting from hours after the event up
to several days later to detect the host galaxy. We compared the results
obtained from our optical/NIR observations with the available Swift high-energy
data of this burst. Our observational campaign led to the detection of the
optical afterglow and host galaxy of GRB 090205 and to the first measure of its
redshift, z=4.65. Similar to other, recent high-z GRBs, GRB 090205 has a short
duration in the rest-frame with T_{90,rf}=1.6 s, which suggests the possibility
that it might belong to the short GRBs class. The X-ray afterglow of GRB 090205
shows a complex and interesting behaviour with a possible rebrightening at
500-1000s from the trigger time and late flaring activity. Photometric
observations of the GRB 090205 host galaxy argue in favor of a starburst galaxy
with a stellar population younger than ~ 150 Myr. Moreover, the metallicity of
Z > 0.27 Z_Sun derived from the GRB afterglow spectrum is among the highest
derived from GRB afterglow measurement at high-z, suggesting that the burst
occurred in a rather enriched envirorment. Finally, a detailed analysis of the
afterglow spectrum shows the existence of a line corresponding to Lyman-alpha
emission at the redshift of the burst. GRB 090205 is thus hosted in a typical
Lyman-alpha emitter (LAE) at z=4.65. This makes the GRB 090205 host the
farthest GRB host galaxy, spectroscopically confirmed, detected to date.Comment: Accepted for publication in Astronomy and Astrophysics; 8 pages, 7
figure
Astrophysics: Most distant cosmic blast seen
The most distant -ray burst yet sighted is the earliest astronomical object
ever observed in cosmic history. This ancient beacon offers a glimpse of the
little-known cosmic dark ages.Comment: Published in Nature News & View
Detectable Signatures of Cosmic Radiative Feedback
We use a semi-analytical model to study the impact of reionization, and the
associated radiative feedback, on galaxy formation. Two feedback models have
been considered: (i) a standard prescription, according to which star formation
is totally suppressed in galaxies with circular velocity below a critical
threshold (model CF06) and (ii) a characterization based on the filtering scale
(model G00), allowing for a gradual reduction of the gas available for star
formation in low-mass galaxies. In model CF06 reionization starts at z ~ 15-20,
is 85% complete by z ~ 10; at the same z, the ionized fraction is 16% in model
G00. The models match SDSS constraints on the evolution of the neutral hydrogen
fraction at z < 7, but predict different Thomson optical depths, tau_e = 0.1017
(CF06), and 0.0631 (G00); such values are within 1 sigma of the WMAP 3-yr
determination. Both models are in remarkable good agreement with additional
existing data (evolution of Lyman-limit systems, cosmic star formation history,
high-z galaxy counts, IGM thermal history), which therefore cannot be used to
discriminate among different feedback models. Deviations among radiative
feedback prescriptions emerge when considering the expected HI 21 cm background
signal, where a ~ 15 mK absorption feature in the range 75-100 MHz is present
in model G00 and a global shift of the emission feature preceding reionization
towards larger frequencies occurs in the same model. Single dish observations
with existing or forthcoming low-frequency radio telescopes can achieve mK
sensitivity, allowing the identification of these features provided that
foregrounds can be accurately subtracted.Comment: 9 pages, 7 figures, accepted for publication in MNRA
GRB orphan afterglows in present and future radio transient surveys
Orphan Afterglows (OA) are slow transients produced by Gamma Ray Bursts seen
off-axis that become visible on timescales of days/years at optical/NIR and
radio frequencies, when the prompt emission at high energies (X and gamma rays)
has already ceased. Given the typically estimated jet opening angle of GRBs
theta_jet ~ 3 deg, for each burst pointing to the Earth there should be a
factor ~ 700 more GRBs pointing in other directions. Despite this, no secure
OAs have been detected so far. Through a population synthesis code we study the
emission properties of the population of OA at radio frequencies. OAs reach
their emission peak on year-timescales and they last for a comparable amount of
time. The typical peak fluxes (which depend on the observing frequency) are of
few micro Jy in the radio band with only a few OA reaching the mJy level. These
values are consistent with the upper limits on the radio flux of SN Ib/c
observed at late times. We find that the OA radio number count distribution has
a typical slope -1.7 at high fluxes and a flatter (-0.4) slope at low fluxes
with a break at a frequency-dependent flux. Our predictions of the OA rates are
consistent with the (upper) limits of recent radio surveys and archive searches
for radio transients. Future radio surveys like VAST/ASKAP at 1.4 GHz should
detect ~ 3x10^-3 OA deg^-2 yr-1, MeerKAT and EVLA at 8.4 GHz should see ~
3x10^-1 OA deg-2 yr-1. The SKA, reaching the micro Jy flux limit, could see up
to ~ 0.2-1.5 OA deg^-2 yr^-1. These rates also depend on the duration of the OA
above a certain flux limit and we discuss this effect with respect to the
survey cadence.Comment: (10 pages, 5 figures, 1 table) Accepted for publication by PAS
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