171 research outputs found
Using GAMA to probe the impact of small-scale galaxy physics on nonlinear redshift-space distortions
We present improved modelling of the redshift-space distortions of galaxy
clustering that arise from peculiar velocities. We create mock galaxy
catalogues in the framework of the halo model, using data from the Bolshoi
project. These mock galaxy populations are inserted into the haloes with
additional degrees of freedom that govern spatial and kinematical biases of the
galaxy populations relative to the dark matter. We explore this generalised
halo model with an MCMC algorithm, comparing the predictions to data from the
Galaxy And Mass Assembly (GAMA) survey, and thus derive one of the first
constraints on the detailed kinematic degrees of freedom for satellite galaxies
within haloes. With this approach, the distortions of the redshift-space galaxy
autocorrelations can be accounted for down to spatial separations close to 10
kpc, opening the prospect of improved RSD measurements of the perturbation
growth rate by the inclusion of data from nonlinear scales.Comment: 19 pages, 10 figures, comments are welcom
KiDS+VIKING+GAMA: Halo occupation distributions and correlations of satellite numbers with a new halo model of the galaxy-matter bispectrum for galaxy-galaxy-galaxy lensing
Halo models and halo occupation distributions (HODs) are important tools to
model the galaxy and matter distribution. We present and assess a new method
for constraining the parameters of HODs using the gravitational lensing shear
around galaxy pairs, galaxy-galaxy-galaxy-lensing (G3L). In contrast to
galaxy-galaxy-lensing, G3L is sensitive to correlations between the per-halo
numbers of galaxies from different populations. We use G3L to probe these
correlations and test the default hypothesis that they are negligible. We
derive a halo model for G3L and validate it with realistic mock data from the
Millennium Simulation and a semi-analytic galaxy model. Then, we analyse public
data from the Kilo-Degree Survey (KiDS), the VISTA Infrared Kilo-Degree Galaxy
Survey (VIKING) and data from the Galaxy And Mass Assembly Survey (GAMA) to
infer the HODs of galaxies at in five different stellar mass bins
between and and two colours
(red and blue), as well as correlations between satellite numbers. The analysis
recovers the true HODs in the simulated data within the credibility
range. The inferred HODs vary significantly with colour and stellar mass. There
is also strong evidence () for correlations, increasing with halo
mass, between the numbers of red and blue satellites and galaxies with stellar
masses below $10^{10} \Msun. Possible causes of these correlations are the
selection of similar galaxies in different samples, the survey flux limit, or
physical mechanisms like a fixed ratio between the satellite numbers of
distinct populations. The decorrelation for halos with smaller masses is
probably an effect of shot noise by low-occupancy halos. The inferred HODs can
be used to complement galaxy-galaxy-lensing or galaxy clustering HOD studies or
as input to cosmological analyses and improved mock galaxy catalogues.Comment: 20 pages + Appendix, 14 Figures. Submitted to Astronomy &
Astrophysics. Abstract is abridge
Embedded-Cluster Calculations in a Numeric Atomic Orbital Density-Functional Theory Framework
We integrate the all-electron electronic structure code FHI-aims into the
general ChemShell package for solid-state embedding (QM/MM) calculations. A
major undertaking in this integration is the implementation of pseudopotential
functionality into FHI-aims to describe cations at the QM/MM boundary through
effective core potentials and therewith prevent spurious overpolarization of
the electronic density. Based on numeric atomic orbital basis sets, FHI-aims
offers particularly efficient access to exact exchange and second order
perturbation theory, rendering the established QM/MM setup an ideal tool for
hybrid and double-hybrid level DFT calculations of solid systems. We illustrate
this capability by calculating the reduction potential of Fe in the
Fe-substituted ZSM-5 zeolitic framework and the reaction energy profile for
(photo-)catalytic water oxidation at TiO2(110).Comment: 12 pages, 4 figure
Unbiased Cosmological Parameter Estimation from Emission Line Surveys with Interlopers
The galaxy catalogs generated from low-resolution emission line surveys often
contain both foreground and background interlopers due to line
misidentification, which can bias the cosmological parameter estimation. In
this paper, we present a method for correcting the interloper bias by using the
joint-analysis of auto- and cross-power spectra of the main and the interloper
samples. In particular, we can measure the interloper fractions from the
cross-correlation between the interlopers and survey galaxies, because the true
cross-correlation must be negligibly small. The estimated interloper fractions,
in turn, remove the interloper bias in the cosmological parameter estimation.
For example, in the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX)
low-redshift () [O II] {\AA} emitters contaminate
high-redshift () Lyman- line emitters. We demonstrate that
the joint-analysis method yields a high signal-to-noise ratio measurement of
the interloper fractions while only marginally increasing the uncertainties in
the cosmological parameters relative to the case without interlopers. We also
show the same is true for the high-latitude spectroscopic survey of Wide-Field
Infrared Survey Telescope (WFIRST) mission where contamination occurs between
the Balmer- line emitters at lower redshifts () and Oxygen
([O III] {\AA}) line emitters at higher redshifts ().Comment: 36 pages, 26 figure
Supervoid Origin of the Cold Spot in the Cosmic Microwave Background
We use a WISE-2MASS-Pan-STARRS1 galaxy catalog to search for a supervoid in
the direction of the Cosmic Microwave Background Cold Spot. We obtain
photometric redshifts using our multicolor data set to create a tomographic map
of the galaxy distribution. The radial density profile centred on the Cold Spot
shows a large low density region, extending over 10's of degrees. Motivated by
previous Cosmic Microwave Background results, we test for underdensities within
two angular radii, , and . Our data, combined with an
earlier measurement by Granett et al 2010, are consistent with a large supervoid with centered at . Such a supervoid, constituting a
fluctuation in the model, is a plausible cause
for the Cold Spot.Comment: 4 pages, 2 figures, Proceedings of IAU 306 Symposium: Statistical
Challenges in 21st Century Cosmolog
Small-scale galaxy clustering in the eagle simulation
We study present-day galaxy clustering in the EAGLE cosmological hydrodynamical simulation. EAGLE’s galaxy formation parameters were calibrated to reproduce the redshift z = 0.1 galaxy stellar mass function, and the simulation also reproduces galaxy colours well. The simulation volume is too small to correctly sample large-scale fluctuations and we therefore concentrate on scales smaller than a few mega parsecs. We find very good agreement with observed clustering measurements from the Galaxy And Mass Assembly (GAMA) survey, when galaxies are binned by stellar mass, colour or luminosity. However, low-mass red galaxies are clustered too strongly, which is at least partly due to limited numerical resolution. Apart from this limitation, we conclude that EAGLE galaxies inhabit similar dark matter haloes as observed GAMA galaxies, and that the radial distribution of satellite galaxies, as a function of stellar mass and colour, is similar to that observed as well
The dependence of intrinsic alignment of galaxies on wavelength using KiDS and GAMA
The outer regions of galaxies are more susceptible to the tidal interactions that lead to intrinsic alignments of galaxies. The resulting alignment signal may therefore depend on the passband if the colours of galaxies vary spatially. To quantify this, we measured the shapes of galaxies with spectroscopic redshifts from the GAMA survey using deep gri imaging data from the KiloDegree Survey. The performance of the moment-based shape measurement algorithm DEIMOS was assessed using dedicated image simulations, which showed that the ellipticities could be determined with an accuracy better than 1% in all bands. Additional tests for potential systematic errors did not reveal any issues. We measure a significant difference of the alignment signal between the g,r and i-band observations. This difference exceeds the amplitude of the linear alignment model on scales below 2 Mpc h -1 . Separating the sample into central/satellite and red/blue galaxies, we find that the difference is dominated by red satellite galaxies
Searching for Supernovae in HETDEX Data Release 3
We have extracted 636 spectra taken at the positions of 583 transient sources from the third data release of the Hobby-Eberly Telescope Dark Energy eXperiment (HETDEX). The transients were discovered by the Zwicky Transient Facility (ZTF) during 2018-2022. The HETDEX spectra provide a potential means to obtain classifications for a large number of objects found by photometric surveys for free. We attempt to explore and classify the spectra by utilizing several template-matching techniques. We have identified two transient sources, ZTF20aatpoos = AT 2020fiz and ZTF19abdkelq, as supernova (SN) candidates. We classify AT 2020fiz as a Type IIP SN observed ∼10 days after explosion, and we propose ZTF19abdkelq as a likely Type Ia SN caught ∼40 days after maximum light. ZTF photometry of these two sources are consistent with their classifications as SNe. Beside these two objects, we have confirmed several ZTF transients as variable active galactic nuclei based on their spectral appearance, and determined the host galaxy types of several other ZTF transients
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