716 research outputs found
Lyman Alpha Emitter Evolution in the Reionization Epoch
Combining cosmological SPH simulations with a previously developed Lyman
Alpha production/transmission model and the Early Reionization Model (ERM,
reionization ends at redshift z~7), we obtain Lyman Alpha and UV Luminosity
Functions (LFs) for Lyman Alpha Emitters (LAEs) for redshifts between 5.7 and
7.6. Matching model results to observations at z~5.7 requires escape fractions
of Lyman Alpha, f_alpha=0.3, and UV (non-ionizing) continuum photons, f_c=0.22,
corresponding to a color excess, E(B-V)=0.15. We find that (i) f_c increases
towards higher redshifts, due the decreasing mean dust content of galaxies,
(ii) the evolution of f_alpha/f_c hints at the dust content of the ISM becoming
progressively inhomogeneous/clumped with decreasing redshift. The clustering
photoionization boost is important during the initial reionization phases but
has little effect on the Lyman Alpha LF for a highly ionized IGM. Halo
(stellar) masses are in the range 10.0 < \log M_h < 11.8 (8.1 < \log M_* <
10.4) with M_h \propto M_*^{0.64}. The star formation rates are between 3-120
solar masses per year, mass-weighted mean ages are greater than 20 Myr at all
redshifts, while the mean stellar metallicity increases from Z=0.12 to 0.22
solar metallicity from z~7.6 to z~5.7; both age and metallicity positively
correlate with stellar mass. The brightest LAEs are all characterized by large
star formation rates and intermediate ages (~200 Myr), while objects in the
faint end of the Lyman Alpha LF show large age and star formation rate spreads.
With no more free parameters, the Spectral Energy Distributions of three LAE at
z~5.7 observed by Lai et al. (2007) are well reproduced by an intermediate age
(182-220 Myr) stellar population and the above E(B-V) value.Comment: 13 pages, 9 figures, accepted to MNRA
Quantifying Tensions between CMB and Distance Datasets in Models with Free Curvature or Lensing Amplitude
Recent measurements of the Cosmic Microwave Background (CMB) by the Planck
Collaboration have produced arguably the most powerful observational evidence
in support of the standard model of cosmology, i.e. the spatially flat
CDM paradigm. In this work, we perform model selection tests to
examine whether the base CMB temperature and large scale polarization
anisotropy data from Planck 2015 (P15) prefer any of eight commonly used
one-parameter model extensions with respect to flat CDM. We find a
clear preference for models with free curvature, , or free
amplitude of the CMB lensing potential, . We also further develop
statistical tools to measure tension between datasets. We use a Gaussianization
scheme to compute tensions directly from the posterior samples using an
entropy-based method, the surprise, as well as a calibrated evidence ratio
presented here for the first time. We then proceed to investigate the
consistency between the base P15~CMB data and six other CMB and distance
datasets. In flat CDM we find a tension between the base
P15~CMB data and a distance ladder measurement, whereas the former are
consistent with the other datasets. In the curved CDM model we find
significant tensions in most of the cases, arising from the well-known low
power of the low- multipoles of the CMB data. In the flat CDM
model, however, all datasets are consistent with the base
P15~CMB observations except for the CMB lensing measurement, which remains in
significant tension. This tension is driven by the increased power of the CMB
lensing potential derived from the base P15~CMB constraints in both models,
pointing at either potentially unresolved systematic effects or the need for
new physics beyond the standard flat CDM model.Comment: 16 pages, 8 figures, 6 table
Simulating the formation of a proto-cluster at z~2
We present results from two high-resolution hydrodynamical simulations of
proto-cluster regions at z~2.1. The simulations have been compared to
observational results for the socalled Spiderweb galaxy system, the core of a
putative proto-cluster region at z = 2.16, found around a radio galaxy. The
simulated regions have been chosen so as to form a poor cluster with M200~10^14
h-1 Msun (C1) and a rich cluster with M200~2x10^15 h-1 Msun (C2) at z = 0. The
simulated proto-clusters show evidence of ongoing assembly of a dominating
central galaxy. The stellar mass of the brightest cluster galaxy (BCG) of the
C2 system is in excess with respect to observational estimates for the
Spiderweb galaxy, with a total star formation rate which is also larger than
indicated by observations. We find that the projected velocities of galaxies in
the C2 cluster are consistent with observations, while those measured for the
poorer cluster C1 are too low compared to the observed velocities. We argue
that the Spiderweb complex resemble the high-redshift progenitor of a rich
galaxy cluster. Our results indicate that the included supernovae feedback is
not enough to suppress star formation in these systems, supporting the need of
introducing AGN feedback. According to our simulations, a diffuse atmosphere of
hot gas in hydrostatic equilibrium should already be present at this redshift,
and enriched at a level comparable to that of nearby galaxy clusters. The
presence of this gas should be detectable with future deep X-ray observations.Comment: 6 pages, 4 figures, accepted for publication in MNRAS (Letters
Properties of the galaxy population in hydrodynamical simulations of clusters
We present a study of the galaxy population predicted by hydrodynamical
simulations for a set of 19 galaxy clusters based on the GADGET-2 Tree+SPH
code. These simulations include gas cooling, star formation, a detailed
treatment of stellar evolution and chemical enrichment, as well as SN energy
feedback in the form of galactic winds. We compute the spectro-photometric
properties of the simulated galaxies. All simulations have been performed for
two choices of the stellar initial mass function: a standard Salpeter IMF, and
a top-heavier IMF. Several of the observational properties of the galaxy
population in nearby clusters are reproduced fairly well by simulations. A
Salpeter IMF is successful in accounting for the slope and the normalization of
the color-magnitude relation for the bulk of the galaxy population. Simulated
clusters have a relation between mass and optical luminosity which generally
agrees with observations, both in normalization and slope. We find that
galaxies are generally bluer, younger and more star forming in the cluster
outskirts, thus reproducing the observational trends. However, simulated
clusters have a total number of galaxies which is significantly smaller than
the observed one, falling short by about a factor 2-3. Finally, the brightest
cluster galaxies are always predicted to be too massive and too blue, when
compared to observations, due to gas overcooling in the core cluster regions,
even in the presence of a rather efficient SN feedback.Comment: 15 pages, 17 figures, to appear in MNRA
Struktur bahasa Besoa
Buku Struktur Bahasa Besoa ini merupakan salah satu
hasil Proyek Penelitian Bahasa dan Sastra Indonesia dan Daerah Sulawesi Tengah tahun 1986 yang pelaksanaannya dipercayakan kepada tim penelitidari Universitas Tadulako. Penelitian struktur bahasa Besoa ini dilaksanakan oleh
satu tim peneliti untuk memperoleh data di desa Rarnpo, salah satu desa yang dihuni oleh suku Besoa. Pemilihan desa ini sebagai daerahsampel ditetapkan berdasarkan beberapa pertimbangan guna kepentingan penelitian. Data yang diperoleh berdasarkan langkah-langkah yang telah ditetapkan dalam instrumen penelitian memungkinkan adanya variasi setelah melihat kepentingan data
yang ada. Pengolahan data itu dimuat dalam bab-bab yang ada
Gas cooling in semi-analytic models and SPH simulations: are results consistent?
We present a detailed comparison between the galaxy populations within a
massive cluster, as predicted by hydrodynamical SPH simulations and by a
semi-analytic model (SAM) of galaxy formation. Both models include gas cooling
and a simple prescription of star formation, which consists in transforming
instantaneously any cold gas available into stars, while neglecting any source
of energy feedback. We find that, in general, galaxy populations from SAMs and
SPH have similar statistical properties, in agreement with previous studies.
However, when comparing galaxies on an object-by-object basis, we find a number
of interesting differences: a) the star formation histories of the brightest
cluster galaxies (BCGs) from SAM and SPH models differ significantly, with the
SPH BCG exhibiting a lower level of star formation activity at low redshift,
and a more intense and shorter initial burst of star formation with respect to
its SAM counterpart; b) while all stars associated with the BCG were formed in
its progenitors in the semi-analytic model used here, this holds true only for
half of the final BCG stellar mass in the SPH simulation, the remaining half
being contributed by tidal stripping of stars from the diffuse stellar
component associated with galaxies accreted on the cluster halo; c) SPH
satellites can loose up to 90 per cent of their stellar mass at the time of
accretion, due to tidal stripping, a process not included in the semi-analytic
model used in this study; d) in the SPH simulation, significant cooling occurs
on the most massive satellite galaxies and this lasts for up to 1 Gyr after
accretion. This physical process is not included in the semi-analytic model
used in our study, as well as in most of the models discussed in the recent
literature.Comment: Revised version submitted to MNRAS, 15 pages, 9 figures. A
High-resolution version of the paper and figures can be found at this
http://adlibitum.oats.inaf.it/saro/SAM2/paper.pd
Stellar Mass to Halo Mass Scaling Relation for X-ray Selected Low Mass Galaxy Clusters and Groups out to Redshift
We present the stellar mass-halo mass scaling relation for 46 X-ray selected
low-mass clusters or groups detected in the XMM-BCS survey with masses
at
redshift . The cluster binding masses are inferred
from the measured X-ray luminosities \Lx, while the stellar masses
of the galaxy populations are estimated using near-infrared imaging from the
SSDF survey and optical imaging from the BCS survey. With the measured \Lx\ and
stellar mass , we determine the best fit stellar mass-halo mass
relation, accounting for selection effects, measurement uncertainties and the
intrinsic scatter in the scaling relation. The resulting mass trend is
, the intrinsic (log-normal) scatter is
, and there is no
significant redshift trend , although
the uncertainties are still large. We also examine within a fixed
projected radius of ~Mpc, showing that it provides a cluster binding mass
proxy with intrinsic scatter of (1 in ). We
compare our scaling relation from the XMM-BCS
clusters with samples of massive, SZE-selected clusters
() and low mass NIR-selected clusters
() at redshift .
After correcting for the known mass measurement systematics in the compared
samples, we find that the scaling relation is in good agreement with the high
redshift samples, suggesting that for both groups and clusters the stellar
content of the galaxy populations within depends strongly on mass but
only weakly on redshift out to .Comment: 15 pages, 10 figures. Accepted for publication in MNRA
Struktur bahasa Besoa
Buku Struktur Bahasa Besoa ini merupakan salah satu
hasil Proyek Penelitian Bahasa dan Sastra Indonesia dan Daerah Sulawesi Tengah tahun 1986 yang pelaksanaannya dipercayakan kepada tim peneliti dari Universitas Tadulako. Untuk itu, kami ingin menyatakan penghargaan dan ucapan terima kasih kepada Pemimpin Proyek Penelitian Bahasa dan Sastra Indonesia dan Darah Sulawesi Tengah tahun 1986 beserta stafnya, dan para peneliti, yaitu Ahmad Saro, Hanafi Sulaiman, Abdillah A. Rahim, Sudarmin Kuruda
- …