35 research outputs found
On the shape of dark matter halos from MultiDark Planck simulations
The halo shape plays a central role in determining important observational
properties of the haloes such as mass, concentration and lensing
cross-sections. The triaxiality of lensing galaxy clusters has a substantial
impact on the distribution of the largest Einstein radii, while weak lensing
techniques are sensitive to the intrinsic halo ellipticity. In this work, we
provide scaling relations for the shapes of dark matter haloes as a function of
mass (peak height) and redshift over more than four orders of magnitude in halo
masses, namely from to M. We have
analysed four dark matter only simulations from the MultiDark cosmological
simulation suite with more than 56 billion particles within boxes of 4.0, 2.5,
1.0 and 0.4 Gpc size assuming \textit{Planck} cosmology. The dark
matter haloes have been identified in the simulations using the {\sc rockstar}
halo finder, which also determines the axis ratios in terms of the
diagonalization of the inertia tensor. In order to infer the shape for a
hypothetical halo of a given mass at a given redshift, we provide fitting
functions to the minor-to-major and intermediate-to-major axis ratios as a
function of the peak height.Comment: Accepted for publication in MNRAS (14 pages, 13 figures). The
ROCKSTAR outputs used in this paper are available at
https://www.cosmosim.org/cms/simulations/data
CLUMP-3D. Testing CDM with galaxy cluster shapes
The CDM model of structure formation makes strong predictions on
concentration and shape of DM (dark matter) halos, which are determined by mass
accretion processes. Comparison between predicted shapes and observations
provides a geometric test of the CDM model. Accurate and precise
measurements needs a full three-dimensional analysis of the cluster mass
distribution. We accomplish this with a multi-probe 3D analysis of the X-ray
regular CLASH (Cluster Lensing And Supernova survey with Hubble) clusters
combining strong and weak lensing, X-ray photometry and spectroscopy, and the
Sunyaev-Zel'dovich effect. The cluster shapes and concentrations are consistent
with CDM predictions. The CLASH clusters are randomly oriented, as
expected given the sample selection criteria. Shapes agree with numerical
results for DM-only halos, which hints at baryonic physics being not so
effective in making halos rounder.Comment: v2: 8 pages, in press on ApJL. Extended discussion on regularity. One
of three new companion papers of the CLUMP-3D project (Keiichi Umetsu et al.,
arxiv:1804.00664; I-Non Chiu et al., arXiv:1804.00676
Shocks in the Stacked Sunyaev-Zel'dovich Profiles of Clusters I: Analysis with the Three Hundred Simulations
Gas infalling into the gravitational potential wells of massive galaxy
clusters is expected to experience one or more shocks on its journey to
becoming part of the intracluster medium (ICM). These shocks are important for
setting the thermodynamic properties of the ICM and can therefore impact
cluster observables such as X-ray emission and the Sunyaev-Zel'dovich (SZ)
effect. We investigate the possibility of detecting signals from cluster shocks
in the averaged thermal SZ profiles of galaxy clusters. Using zoom-in
hydrodynamic simulations of massive clusters from the Three Hundred Project, we
show that if cluster SZ profiles are stacked as a function of ,
shock-induced features appear in the averaged SZ profile. These features are
not accounted for in standard fitting formulae for the SZ profiles of galaxy
clusters. We show that the shock features should be detectable with samples of
clusters from ongoing and future SZ surveys. We also demonstrate that the
location of these features is correlated with the cluster accretion rate, as
well as the location of the cluster splashback radius. Analyses of ongoing and
future surveys, such as SPT-3G, AdvACT, Simons Observatory and CMB-S4, that
include gas shocks will gain a new handle on the properties and dynamics of the
outskirts of massive halos, both in gas and in mass.Comment: 13 pages, 8 figures; matches version accepted by MNRA
Micro Gas Turbine and Solar Parabolic Dish for distributed generation
[EN]A thermodynamic model for a Brayton-like microturbine
in combination with a solar parabolic dish is analyzed in
order to evaluate its efficiency under any ambient condition. The
thermodynamic cycle is a recuperative Brayton cycle with
internal irreversibilities in the recuperator, compressor and
turbine and external losses associated to the heat transfers in the
solar receiver, the combustion chamber, and the environment.
All the irreversibilities have been taken into account in the
model with home-software elaborated using MathematicaĂą.
The model validation is done by comparison with results
provided by Semprini et al. [1]. An analysis of hybrid and
sunless performance is carried out for four different microturbine
power outlets (30, 23, 15 and 7 kWe) and for four days
of the year (corresponding to each season). The greenhouse
emissions are also calculated for both off-design performance
and for the four power output levels
CLUMP-3D: Testing ÎCDM with Galaxy Cluster Shapes
The ÎCDM model of structure formation makes strong predictions on the concentration and shape of dark matter (DM) halos, which are determined by mass accretion processes. Comparison between predicted shapes and observations provides a geometric test of the ÎCDM model. Accurate and precise measurements needs a full three-dimensional (3D) analysis of the cluster mass distribution. We accomplish this with a multi-probe 3D analysis of the X-ray regular Cluster Lensing and Supernova survey with Hubble (CLASH) clusters combining strong and weak lensing, X-ray photometry and spectroscopy, and the SunyaevâZel'dovich effect (SZe). The cluster shapes and concentrations are consistent with ÎCDM predictions. The CLASH clusters are randomly oriented, as expected given the sample selection criteria. Shapes agree with numerical results for DM-only halos, which hints at baryonic physics being less effective in making halos rounder
Expectations of the size evolution of massive galaxies at from the TNG50 simulation: the CEERS/JWST view
We present a catalog of about 25,000 images of massive () galaxies at redshift from the TNG50 cosmological
simulation, tailored for observations at multiple wavelengths carried out with
JWST. The synthetic images were created with the SKIRT radiative transfer code,
including the effects of dust attenuation and scattering. The noiseless images
were processed with the mirage simulator to mimic the Near Infrared Camera
(NIRCam) observational strategy (e.g., noise, dithering pattern, etc.) of the
Cosmic Evolution Early Release Science (CEERS) survey. In this paper, we
analyze the predictions of the TNG50 simulation for the size evolution of
galaxies at and the expectations for CEERS to probe that
evolution. In particular, we investigate how sizes depend on wavelength,
redshift, mass, and angular resolution of the images. We find that the
effective radius accurately describes the three-dimensional half-mass radius of
TNG50 galaxies. Sizes observed at 2~m are consistent with those measured
at 3.56~m at all redshifts and masses. At all masses, the population of
higher- galaxies is more compact than their lower- counterparts. However,
the intrinsic sizes are smaller than the mock observed sizes for the most
massive galaxies, especially at . This discrepancy between the
mass and light distribution may point to a transition in the galaxy morphology
at =4-5, where massive compact systems start to develop more extended
stellar structures.Comment: Accepted for publication in ApJ (20 pages, 12 figures). Data publicly
released at https://www.tng-project.org/costantin22 and at
https://www.lucacostantin.com/OMEG
A Milky Way-like barred spiral galaxy at a redshift of 3
International audienceThe majority of massive disk galaxies in the local Universe show a stellar barred structure in their central regions, including our Milky Way. Bars are supposed to develop in dynamically cold stellar disks at low redshift, as the strong gas turbulence typical of disk galaxies at high redshift suppresses or delays bar formation. Moreover, simulations predict bars to be almost absent beyond in the progenitors of Milky Way-like galaxies. Here we report observations of ceers-2112, a barred spiral galaxy at redshift , which was already mature when the Universe was only 2 Gyr old. The stellar mass () and barred morphology mean that ceers-2112 can be considered a progenitor of the Milky Way, in terms of both structure and mass-assembly history in the first 2 Gyr of the Universe, and was the closest in mass in the first 4 Gyr. We infer that baryons in galaxies could have already dominated over dark matter at , that high-redshift bars could form in approximately 400 Myr and that dynamically cold stellar disks could have been in place by redshift (more than 12 Gyrs ago)
First Look at z > 1 Bars in the Rest-Frame Near-Infrared with JWST Early CEERS Imaging
Stellar bars are key drivers of secular evolution in galaxies and can be
effectively studied using rest-frame near-infrared (NIR) images, which trace
the underlying stellar mass and are less impacted by dust and star formation
than rest-frame UV or optical images. We leverage the power of {\it{JWST}}
CEERS NIRCam images to present the first quantitative identification and
characterization of stellar bars at based on rest-frame NIR F444W images
of high resolution (~1.3 kpc at z ~ 1-3). We identify stellar bars in these
images using quantitative criteria based on ellipse fits. For this pilot study,
we present six examples of robustly identified bars at with spectroscopic
redshifts, including the two highest redshift bars at ~2.136 and 2.312
quantitatively identified and characterized to date. The stellar bars at ~
1.1-2.3 presented in our study have projected semi-major axes of ~2.9-4.3 kpc
and projected ellipticities of ~0.41-0.53 in the rest-frame NIR. The barred
host galaxies have stellar masses ~ to
, star formation rates of ~ 21-295 yr, and
several have potential nearby companions. Our finding of bars at ~1.1-2.3
demonstrates the early onset of such instabilities and supports simulations
where bars form early in massive dynamically cold disks. It also suggests that
if these bars at lookback times of 8-10 Gyr survive out to present epochs,
bar-driven secular processes may operate over a long time and have a
significant impact on some galaxies by z ~ 0.Comment: 16 pages, 5 figures. Accepted for Publication in Astrophysical
Journal Letter