Prof. Roy Maartenshttp://hdl.handle.net/10566/17122023-11-30T21:06:26Z2023-11-30T21:06:26ZNonlinear modulation of the HI power spectrum on ultra-large scales. IUmeh, ObinnaMaartens, RoySantos, Mario G.http://hdl.handle.net/10566/19112016-08-30T20:05:51Z2015-01-01T00:00:00ZNonlinear modulation of the HI power spectrum on ultra-large scales. I
Umeh, Obinna; Maartens, Roy; Santos, Mario G.
Intensity mapping of the neutral hydrogen brightness temperature promises to provide a three-dimensional view of the universe on very large scales. Nonlinear effects are typically thought to alter only the small-scale power, but we show how they may bias the extraction of cosmological information contained in the power spectrum on ultra-large scales. For linear perturbations to remain valid on large scales, we need to renormalize perturbations at higher order. In the case of intensity mapping, the second-order contribution to clustering from weak lensing dominates the nonlinear contribution at high redshift. Renormalization modifies the mean brightness temperature and therefore the evolution bias. It also introduces a term that mimics white noise. These effects may influence forecasting analysis on ultra-large scales.
2015-01-01T00:00:00ZHunting down horizon-scale effects with multi-wavelength surveysFonseca, JoseCamera, StefanoSantos, Mario G.Maartens, Royhttp://hdl.handle.net/10566/19012016-08-30T20:05:49Z2015-01-01T00:00:00ZHunting down horizon-scale effects with multi-wavelength surveys
Fonseca, Jose; Camera, Stefano; Santos, Mario G.; Maartens, Roy
Next-generation cosmological surveys will probe ever larger volumes of the universe, including the largest scales, near and beyond the horizon. On these scales, the galaxy power spectrum carries signatures of local primordial non-Gaussianity (PNG) and horizon-scale general relativistic (GR) effects. However, cosmic variance limits the detection of horizon-scale effects. Combining different surveys via the multi-tracer method allows us to reduce the effect of cosmic variance. This method benefits from large bias differences between two tracers of the underlying dark matter distribution, which suggests a multi-wavelength combination of large volume surveys that are planned on a similar timescale. We show that the combination of two contemporaneous surveys, a large neutral hydrogen intensity mapping survey in SKA Phase 1 and a Euclid-like photometric survey, will provide unprecedented constraints on PNG as well as detection of the GR effects. We forecast that the error on local PNG will break through the cosmic variance limit on cosmic microwave background surveys, depending on assumed priors, bias, and sky coverage. GR effects are more robust to changes in the assumed fiducial model, and we forecast that they can be detected with a signal-to-noise of about 14.
2015-01-01T00:00:00ZProbing the imprint of interacting dark energy on very large scalesDuniya, Didam, G. A.Bertacca, DanieleMaartens, Royhttp://hdl.handle.net/10566/18942016-08-30T20:05:30Z2015-01-01T00:00:00ZProbing the imprint of interacting dark energy on very large scales
Duniya, Didam, G. A.; Bertacca, Daniele; Maartens, Roy
The observed galaxy power spectrum acquires relativistic corrections from light-cone effects, and these corrections grow on very large scales. Future galaxy surveys in optical, infrared and radio bands will probe increasingly large wavelength modes and reach higher redshifts. In order to exploit the new data on large scales, an accurate analysis requires inclusion of the relativistic effects. This is especially the case for primordial non-Gaussianity and for extending tests of dark energy models to horizon scales. Here we investigate the latter, focusing on models where the dark energy interacts nongravitationally with dark matter. Interaction in the dark sector can also lead to large-scale deviations in the power spectrum. If the relativistic effects are ignored, the imprint of interacting dark energy will be incorrectly identified and thus lead to a bias in constraints on interacting dark energy on very large scales.
2015-01-01T00:00:00ZModel-independent constraints on dark energy and modified gravity with the SKAZhao, Gong-BoBacon, DavidMaartens, RoySantos, Mario G.Raccanelli, Alvisehttp://hdl.handle.net/10566/18222016-08-30T20:05:30Z2014-01-01T00:00:00ZModel-independent constraints on dark energy and modified gravity with the SKA
Zhao, Gong-Bo; Bacon, David; Maartens, Roy; Santos, Mario G.; Raccanelli, Alvise
Employing a nonparametric approach of the principal component analysis (PCA), we forecast
the future constraint on the equation of state w(z) of dark energy, and on the effective Newton
constant m(k; z), which parameterise the effect of modified gravity, using the planned SKA HI
galaxy survey. Combining with the simulated data of Planck and Dark Energy Survey (DES), we
find that SKA Phase 1 (SKA1) and SKA Phase 2 (SKA2) can well constrain 3 and 5 eigenmodes
of w(z) respectively. The errors of the best measured modes can be reduced to 0.04 and 0.023
for SKA1 and SKA2 respectively, making it possible to probe dark energy dynamics. On the
other hand, SKA1 and SKA2 can constrain 7 and 20 eigenmodes of m(k; z) respectively within
10% sensitivity level. Furthermore, 2 and 7 modes can be constrained within sub percent level
using SKA1 and SKA2 respectively. This is a significant improvement compared to the combined
datasets without SKA.
Advancing Astrophysics with the Square Kilometre Array
June 8-13, 2014
Giardini Naxos, Italy
2014-01-01T00:00:00Z