35 research outputs found
Resolving Subhaloes' Lives with the Hierarchical Bound-Tracing Algorithm
We develop a new code, the Hierarchical Bound-Tracing (HBT for short) code,
to find and trace dark matter subhaloes in simulations based on the merger
hierarchy of dark matter haloes. Application of this code to a recent benchmark
test of finding subhaloes demonstrates that HBT stands as one of the best codes
to trace the evolutionary history of subhaloes. The success of the code lies in
its careful treatment of the complex physical processes associated with the
evolution of subhaloes and in its robust unbinding algorithm with an adaptive
source subhalo management. We keep a full record of the merger hierarchy of
haloes and subhaloes, and allow growth of satellite subhaloes through accretion
from its "satellite-of-satellites", hence allowing mergers among satellites.
Local accretion of background mass is omitted, while rebinding of stripped mass
is allowed. The justification of these treatments is provided by case studies
of the lives of individual subhaloes and by the success in finding the complete
subhalo catalogue. We compare our result to other popular subhalo finders and
show that HBT is able to well resolve subhaloes in high density environment and
keep strict physical track of subhaloes' merger history. This code is fully
parallelized and freely available upon request to the authors.Comment: 15 pages; accepted for publication by MNRA
A halo approach to the evaluation of the cross-correlation between the SZ sky and galaxy survey
Using a purely analytic approach to gaseous and dark matter halos, we study
the cross-correlation between the Sunyaev-Zel'dovich (SZ) sky and galaxy survey
under flat sky approximation, in an attempt to acquire the redshift information
of the SZ map. The problem can be greatly simplified when it is noticed that
the signals of the SZ-galaxy correlation arise only from hot gas and galaxies
inside the same massive halos (i.e. clusters), and field galaxies make almost
no contribution to the cross-correlation. Under the assumption that both the
hot gas and galaxies trace the common gravitational potential of dark halos, we
calculate the expected cross SZ-galaxy power spectra for the WMAP/Planck SZ
maps and the SDSS galaxy sample at small scales . It turns out,
however, that it is not presently feasible to measure such small angular cross
power spectra because of the high noise levels at with the WMAP/Planck
experiments. Future SZ observations with better angular resolutions and
sufficiently wide sky coverages will be needed if this technique is applied for
the statistical measurement of redshift distribution of the SZ sources.Comment: 6 pages, 4 figures, accepted for publication in A&
Quantifying the effect of baryon physics on weak lensing tomography
We use matter power spectra from cosmological hydrodynamic simulations to
quantify the effect of baryon physics on the weak gravitational lensing shear
signal. The simulations consider a number of processes, such as radiative
cooling, star formation, supernovae and feedback from active galactic nuclei
(AGN). Van Daalen et al. (2011) used the same simulations to show that baryon
physics, in particular the strong feedback that is required to solve the
overcooling problem, modifies the matter power spectrum on scales relevant for
cosmological weak lensing studies. As a result, the use of power spectra from
dark matter simulations can lead to significant biases in the inferred
cosmological parameters. We show that the typical biases are much larger than
the precision with which future missions aim to constrain the dark energy
equation of state, w_0. For instance, the simulation with AGN feedback, which
reproduces X-ray and optical properties of groups of galaxies, gives rise to a
~40% bias in w_0. We demonstrate that the modification of the power spectrum is
dominated by groups and clusters of galaxies, the effect of which can be
modelled. We consider an approach based on the popular halo model and show that
simple modifications can capture the main features of baryonic feedback.
Despite its simplicity, we find that our model, when calibrated on the
simulations, is able to reduce the bias in w_0 to a level comparable to the
size of the statistical uncertainties for a Euclid-like mission. While
observations of the gas and stellar fractions as a function of halo mass can be
used to calibrate the model, hydrodynamic simulations will likely still be
needed to extend the observed scaling relations down to halo masses of 10 ^12
M_sun/h.Comment: 17 pages, 14 Figures, MNRAS accepted. Small changes to the published
version: typos in Eq. 4 corrected, Figure 2 updated (y-ticks of the previous
version were wrong). Bibliography updated with published papers when possibl
Comparison of the Metabolic Effects of Ritonavir-Boosted Darunavir or Atazanavir Versus Raltegravir, and the Impact of Ritonavir Plasma Exposure: ACTG 5257
Background. Metabolic effects following combination antiretroviral therapy (cART) vary by regimen type. Changes in metabolic effects were assessed following cART in the AIDS Clinical Trials Group (ACTG) A5257 study, and correlated with plasma ritonavir trough concentrations (C24)
Comparison of the Metabolic Effects of Ritonavir-Boosted Darunavir or Atazanavir Versus Raltegravir, and the Impact of Ritonavir Plasma Exposure: ACTG 5257
Background. Metabolic effects following combination antiretroviral therapy (cART) vary by regimen type. Changes in metabolic effects were assessed following cART in the AIDS Clinical Trials Group (ACTG) A5257 study, and correlated with plasma ritonavir trough concentrations (C24)
Week 48 resistance analyses of the once-daily, single-tablet regimen darunavir/cobicistat/emtricitabine/tenofovir alafenamide (D/C/F/TAF) in adults living with HIV-1 from the Phase III Randomized AMBER and EMERALD Trials
Darunavir/cobicistat/emtricitabine/tenofovir alafenamide (D/C/F/TAF) 800/150/200/10 mg is being investigated in two Phase III trials, AMBER (NCT02431247; treatment-naive adults) and EMERALD (NCT02269917; treatment-experienced, virologically suppressed adults). Week 48 AMBER and EMERALD resistance analyses are presented. Postbaseline samples for genotyping/phenotyping were analyzed from protocol-defined virologic failures (PDVFs) with viral load (VL) >= 400 copies/mL at failure/later time points. Post hoc analyses were deep sequencing in AMBER, and HIV-1 proviral DNA from baseline samples (VL = 3 thymidine analog-associated mutations (24% not fully susceptible to tenofovir) detected at screening. All achieved VL <50 copies/mL at week 48 or prior discontinuation. D/C/F/TAF has a high genetic barrier to resistance; no darunavir, primary PI, or tenofovir RAMs were observed through 48 weeks in AMBER and EMERALD. Only one postbaseline M184I/V RAM was observed in HIV-1 of an AMBER participant. In EMERALD, baseline archived RAMs to darunavir, emtricitabine, and tenofovir in participants with prior VF did not preclude virologic response
The origin of the atomic and molecular gas contents of early-type galaxies – II. Misaligned gas accretion
Less Bone Loss With Maraviroc- Versus Tenofovir-Containing Antiretroviral Therapy in the AIDS Clinical Trials Group A5303 Study
Background. There is a need to prevent or minimize bone loss associated with antiretroviral treatment (ART) initiation. We compared maraviroc (MVC)- to tenofovir disoproxil fumarate (TDF)–containing ART