148 research outputs found
Future CMB tests of dark matter: ultra-light axions and massive neutrinos
Measurements of cosmic microwave background (CMB) anisotropies provide strong
evidence for the existence of dark matter and dark energy. They can also test
its composition, probing the energy density and particle mass of different
dark-matter and dark-energy components. CMB data have already shown that
ultra-light axions (ULAs) with mass in the range compose a fraction of the cosmological critical
density. Here, the sensitivity of a proposed CMB-Stage IV (CMB-S4) experiment
(assuming a 1 arcmin beam and noise levels over a sky
fraction of 0.4) to the density of ULAs and other dark-sector components is
assessed. CMB-S4 data should be times more sensitive to the ULA
energy-density than Planck data alone, across a wide range of ULA masses
, and will probe axion decay constants of
, at the grand unified scale. CMB-S4 could
improve the CMB lower bound on the ULA mass from to
, nearing the mass range probed by dwarf galaxy abundances
and dark-matter halo density profiles. These improvements will allow for a
multi- detection of percent-level departures from CDM over a wide range
of masses. Much of this improvement is driven by the effects of weak
gravitational lensing on the CMB, which breaks degeneracies between ULAs and
neutrinos. We also find that the addition of ULA parameters does not
significantly degrade the sensitivity of the CMB to neutrino masses. These
results were obtained using the axionCAMB code (a modification to the CAMB
Boltzmann code), presented here for public use.Comment: 16 pages, 12 figures. The axionCAMB code will be available online at
http://github.com/dgrin1/axionCAMB from 1 August 201
Cosmological simulations of mixed ultralight dark matter
The era of precision cosmology allows us to test the composition of the dark
matter. Mixed ultralight or fuzzy dark matter (FDM) is a cosmological model
with dark matter composed of a combination of particles of mass , with an astrophysical de Broglie wavelength, and
particles with a negligible wavelength sharing the properties of cold dark
matter (CDM). In this work, we simulate cosmological volumes with a dark matter
wave function for the ultralight component coupled gravitationally to CDM
particles. We investigate the impact of a mixture of CDM and FDM in various
proportions and for ultralight particle
masses ranging over five orders of magnitude . To track the evolution
of density perturbations in the non-linear regime, we adapt the simulation code
AxioNyx to solve the CDM dynamics coupled to a FDM wave function obeying the
Schr\"odinger-Poisson equations. We obtain the non-linear power spectrum and
study the impact of the wave effects on the growth of structure on different
scales. We confirm that the steady-state solution of the Schr\"odinger-Poisson
system holds at the center of halos in the presence of a CDM component when it
composes or less of the dark matter but find no stable density core when
the FDM accounts for or less of the dark matter. We implement a modified
friends-of-friends halo finder and find good agreement between the observed
halo abundance and the predictions from the adapted halo model axionHMCode.Comment: Added reference
Single-object Imaging and Spectroscopy to Enhance Dark Energy Science from LSST
Single-object imaging and spectroscopy on telescopes with apertures ranging
from ~4 m to 40 m have the potential to greatly enhance the cosmological
constraints that can be obtained from LSST. Two major cosmological probes will
benefit greatly from LSST follow-up: accurate spectrophotometry for nearby and
distant Type Ia supernovae will expand the cosmological distance lever arm by
unlocking the constraining power of high-z supernovae; and cosmology with time
delays of strongly-lensed supernovae and quasars will require additional
high-cadence imaging to supplement LSST, adaptive optics imaging or
spectroscopy for accurate lens and source positions, and IFU or slit
spectroscopy to measure detailed properties of lens systems. We highlight the
scientific impact of these two science drivers, and discuss how additional
resources will benefit them. For both science cases, LSST will deliver a large
sample of objects over both the wide and deep fields in the LSST survey, but
additional data to characterize both individual systems and overall systematics
will be key to ensuring robust cosmological inference to high redshifts.
Community access to large amounts of natural-seeing imaging on ~2-4 m
telescopes, adaptive optics imaging and spectroscopy on 8-40 m telescopes, and
high-throughput single-target spectroscopy on 4-40 m telescopes will be
necessary for LSST time domain cosmology to reach its full potential. In two
companion white papers we present the additional gains for LSST cosmology that
will come from deep and from wide-field multi-object spectroscopy.Comment: Submitted to the call for Astro2020 science white paper
Wide-field Multi-object Spectroscopy to Enhance Dark Energy Science from LSST
LSST will open new vistas for cosmology in the next decade, but it cannot
reach its full potential without data from other telescopes. Cosmological
constraints can be greatly enhanced using wide-field ( deg total
survey area), highly-multiplexed optical and near-infrared multi-object
spectroscopy (MOS) on 4-15m telescopes. This could come in the form of
suitably-designed large surveys and/or community access to add new targets to
existing projects. First, photometric redshifts can be calibrated with high
precision using cross-correlations of photometric samples against spectroscopic
samples at that span thousands of sq. deg. Cross-correlations of
faint LSST objects and lensing maps with these spectroscopic samples can also
improve weak lensing cosmology by constraining intrinsic alignment systematics,
and will also provide new tests of modified gravity theories. Large samples of
LSST strong lens systems and supernovae can be studied most efficiently by
piggybacking on spectroscopic surveys covering as much of the LSST
extragalactic footprint as possible (up to square degrees).
Finally, redshifts can be measured efficiently for a high fraction of the
supernovae in the LSST Deep Drilling Fields (DDFs) by targeting their hosts
with wide-field spectrographs. Targeting distant galaxies, supernovae, and
strong lens systems over wide areas in extended surveys with (e.g.) DESI or MSE
in the northern portion of the LSST footprint or 4MOST in the south could
realize many of these gains; DESI, 4MOST, Subaru/PFS, or MSE would all be
well-suited for DDF surveys. The most efficient solution would be a new
wide-field, highly-multiplexed spectroscopic instrument in the southern
hemisphere with m aperture. In two companion white papers we present gains
from deep, small-area MOS and from single-target imaging and spectroscopy.Comment: Submitted to the call for Astro2020 science white papers; tables with
estimates of telescope time needed for a supernova host survey can be seen at
http://d-scholarship.pitt.edu/id/eprint/3604
Ultra-light axions and the tension: joint constraints from the cosmic microwave background and galaxy clustering
We search for ultra-light axions as dark matter (DM) and dark energy particle
candidates, for axion masses , by a joint analysis of cosmic microwave background
(CMB) and galaxy clustering data -- and consider if axions can resolve the
tension in inferred values of the matter clustering parameter . We give
legacy constraints from Planck 2018 CMB data, improving 2015 limits on the
axion density by up to a factor of three; CMB data from
the Atacama Cosmology Telescope and the South Pole Telescope marginally weaken
Planck bounds at , owing to lower (and
theoretically-consistent) gravitational lensing signals. We jointly infer, from
Planck CMB and full-shape galaxy power spectrum and bispectrum data from the
Baryon Oscillation Spectroscopic Survey (BOSS), that axions are, today, of the DM for and for
. BOSS data
strengthen limits, in particular at higher by probing
high-wavenumber modes (). BOSS alone finds a
preference for axions at , for , but Planck disfavours this result. Nonetheless, axions
in a window can improve consistency between CMB and galaxy
clustering data, e.g., reducing the discrepancy from to , since these axions suppress structure growth at the scales to which is sensitive. We expect improved
constraints with upcoming high-resolution CMB and galaxy lensing and future
galaxy clustering data, where we will further assess if axions can restore
cosmic concordance.Comment: 52 pages, 22 figure
Precision Epoch of Reionization studies with next-generation CMB experiments
Future arcminute resolution polarization data from ground-based Cosmic
Microwave Background (CMB) observations can be used to estimate the
contribution to the temperature power spectrum from the primary anisotropies
and to uncover the signature of reionization near in the small
angular-scale temperature measurements. Our projections are based on combining
expected small-scale E-mode polarization measurements from Advanced ACTPol in
the range with simulated temperature data from the full Planck
mission in the low and intermediate region, . We show that
the six basic cosmological parameters determined from this combination of data
will predict the underlying primordial temperature spectrum at high multipoles
to better than accuracy. Assuming an efficient cleaning from
multi-frequency channels of most foregrounds in the temperature data, we
investigate the sensitivity to the only residual secondary component, the
kinematic Sunyaev-Zel'dovich (kSZ) term. The CMB polarization is used to break
degeneracies between primordial and secondary terms present in temperature and,
in effect, to remove from the temperature data all but the residual kSZ term.
We estimate a detection of the diffuse homogeneous kSZ signal from
expected AdvACT temperature data at , leading to a measurement of
the amplitude of matter density fluctuations, , at precision.
Alternatively, by exploring the reionization signal encoded in the patchy kSZ
measurements, we bound the time and duration of the reionization with
and . We find that
these constraints degrade rapidly with large beam sizes, which highlights the
importance of arcminute-scale resolution for future CMB surveys.Comment: 10 pages, 10 figure
Deep Multi-object Spectroscopy to Enhance Dark Energy Science from LSST
Community access to deep (i ~ 25), highly-multiplexed optical and
near-infrared multi-object spectroscopy (MOS) on 8-40m telescopes would greatly
improve measurements of cosmological parameters from LSST. The largest gain
would come from improvements to LSST photometric redshifts, which are employed
directly or indirectly for every major LSST cosmological probe; deep
spectroscopic datasets will enable reduced uncertainties in the redshifts of
individual objects via optimized training. Such spectroscopy will also
determine the relationship of galaxy SEDs to their environments, key
observables for studies of galaxy evolution. The resulting data will also
constrain the impact of blending on photo-z's. Focused spectroscopic campaigns
can also improve weak lensing cosmology by constraining the intrinsic
alignments between the orientations of galaxies. Galaxy cluster studies can be
enhanced by measuring motions of galaxies in and around clusters and by testing
photo-z performance in regions of high density. Photometric redshift and
intrinsic alignment studies are best-suited to instruments on large-aperture
telescopes with wider fields of view (e.g., Subaru/PFS, MSE, or GMT/MANIFEST)
but cluster investigations can be pursued with smaller-field instruments (e.g.,
Gemini/GMOS, Keck/DEIMOS, or TMT/WFOS), so deep MOS work can be distributed
amongst a variety of telescopes. However, community access to large amounts of
nights for surveys will still be needed to accomplish this work. In two
companion white papers we present gains from shallower, wide-area MOS and from
single-target imaging and spectroscopy.Comment: Science white paper submitted to the Astro2020 decadal survey. A
table of time requirements is available at
http://d-scholarship.pitt.edu/36036
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