We present a Bayesian analysis of large-scale structure (LSS) and cosmic microwave background data to constrain the form of the primordial power spectrum. We have extended the usual presumption of a ...scale-invariant spectrum to include (i) a running spectral index; (ii) a broken spectrum arising perhaps from an interruption of the potential driving inflation; (iii) a large-scale cut-off in power as the first year Wilkinson Microwave Anisotropy Probe (WMAP) results appear to indicate; (iv) a reconstruction of the spectrum in eight bins in wavenumber; and (v) a spectrum resulting from a cosmological model proposed by Lasenby & Doran, which naturally exhibits an exponential drop in power on very large scales. The result of our complete Bayesian analysis includes not only the posterior probability distribution from which parameter estimates are inferred but also the Bayesian evidence. This evidence value is greater for a model with fewer parameters unless a more complicated model provides a significantly better fit to the data, thus allowing a powerful method of model selection. We find that those models exhibiting any form of cut-off in power on large scales consistently produce higher evidences than either the Harrison–Zel'dovich or single spectral index spectra. In particular, within the best-fitting concordance cosmology, we find the Lasenby & Doran spectrum to show significantly larger evidence as compared to the other models.
ABSTRACT
The Haze is an excess of microwave intensity emission surrounding the Galactic Centre. It is spatially correlated with the γ-ray Fermi bubbles, and with the S-PASS radio polarization plumes, ...suggesting a possible common provenance. The models proposed to explain the origin of the Haze, including energetic events at the Galactic Centre and dark matter decay in the Galactic halo, do not yet provide a clear physical interpretation. In this paper, we present a reanalysis of the Haze including new observations from the Multi-Frequency Instrument (MFI) of the Q-U-I Joint TEnerife (QUIJOTE) experiment, at 11 and 13 GHz. We analyse the Haze in intensity and polarization, characterizing its spectrum. We detect an excess of diffuse intensity signal ascribed to the Haze. The spectrum at frequencies 11 GHz $\, \le \nu \le \,$ 70 GHz is a power law with spectral index βH = −2.79 ± 0.08, which is flatter than the Galactic synchrotron in the same region (βS = −2.98 ± 0.04), but steeper than that obtained from previous works (βH ∼ −2.5 at 23 GHz $\, \le \, \nu \le \,$ 70 GHz). We also observe an excess of polarized signal in the QUIJOTE-MFI maps in the Haze area. This is a first hint detection of polarized Haze, or a consequence of curvature of the synchrotron spectrum in that area. Finally, we show that the spectrum of polarized structures associated with Galactic Centre activity is steep at low frequencies (β ∼ −3.2 at 2.3 GHz ≤ ν ≤ 23 GHz), and becomes flatter above 11 GHz.
We present observations and analysis of a sample of 123 galaxy clusters from the 2013 Planck catalogue of Sunyaev-Zel’dovich sources with the Arcminute Microkelvin Imager (AMI), a ground-based radio ...interferometer. AMI provides an independent measurement with higher angular resolution, 3 arcmin compared to the Planck beams of 5–10 arcmin. The AMI observations thus provide validation of the cluster detections, improved positional estimates, and a consistency check on the fitted size (θs) and flux (Ytot) parameters in the generalised Navarro, Frenk and White (GNFW) model. We detect 99 of the clusters. We use the AMI positional estimates to check the positional estimates and error-bars produced by the Planck algorithms PowellSnakes and MMF3. We find that Ytot values as measured by AMI are biased downwards with respect to the Planck constraints, especially for high Planck-S/N clusters. We perform simulations to show that this can be explained by deviation from the universal pressure profile shape used to model the clusters. We show that AMI data can constrain the α and β parameters describing the shape of the profile in the GNFW model for individual clusters provided careful attention is paid to the degeneracies between parameters, but one requires information on a wider range of angular scales than are present in AMI data alone to correctly constrain all parameters simultaneously.
Comment on Eur. Phys. J. C 77, 412 Barker, W. E. V; Hobson, M. P; Lasenby, A. N
The European physical journal. C, Particles and fields,
07/2023, Letnik:
83, Številka:
7
Journal Article
We present a numerical routine (oscode) with a C++ and Python interface for the efficient solution of one-dimensional, second-order, ordinary differential equations with rapidly oscillating ...solutions. The method is based on a Runge-Kutta-like stepping procedure that makes use of the Wentzel-Kramers-Brillouin approximation to skip regions of integration where the characteristic frequency varies slowly. In regions where this is not the case, the method is able to switch to a made-to-measure Runge-Kutta integrator that minimizes the total number of function evaluations. We demonstrate the effectiveness of the method with example solutions of the Airy equation and an equation exhibiting a burst of oscillations, discussing the error properties of the method in detail. We then show the method applied to physical systems. First, the one-dimensional, time-independent Schrödinger equation is solved as part of a shooting method to search for the energy eigenvalues for a potential with quartic anharmonicity. Then, the method is used to solve the Mukhanov-Sasaki equation describing the evolution of cosmological perturbations, and the primordial power spectrum of the perturbations is computed in different cosmological scenarios. We compare the performance of our solver in calculating a primordial power spectrum of scalar perturbations to that of bingo, an efficient code specifically designed for such applications, and find that our method performs better.
The Arcminute Microkelvin Imager Zwart, J. T. L.; Barker, R. W.; Biddulph, P. ...
Monthly Notices of the Royal Astronomical Society,
12/2008, Letnik:
391, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The Arcminute Microkelvin Imager is a pair of interferometer arrays operating with six frequency channels spanning 13.9–18.2 GHz, for observations on angular scales of 30 arcsec–10 arcmin and for ...declinations greater than −15°; the Small Array has a sensitivity of 30 mJy s−1/2 and the Large Array has a sensitivity of 3 mJy s−1/2. The telescope is aimed principally at Sunyaev–Zel'dovich imaging of clusters of galaxies. We discuss the design of the telescope and describe and explain its electronic and mechanical systems.
ABSTRACT
We present the catalogue of Q-U-I JOint TEnerife (QUIJOTE) Wide Survey radio sources extracted from the maps of the Multi-Frequency Instrument compiled between 2012 and 2018. The catalogue ...contains 786 sources observed in intensity and polarization, and is divided into two separate sub-catalogues: one containing 47 bright sources previously studied by the Planck collaboration and an extended catalogue of 739 sources either selected from the Planck Second Catalogue of Compact Sources or found through a blind search carried out with a Mexican Hat 2 wavelet. A significant fraction of the sources in our catalogue (38.7 per cent) are within the |b| ≤ 20° region of the Galactic plane. We determine statistical properties for those sources that are likely to be extragalactic. We find that these statistical properties are compatible with currently available models, with a ∼1.8 Jy completeness limit at 11 GHz. We provide the polarimetric properties of (38, 33, 31, 23) sources with P detected above the $99.99{{\ \rm per\, cent}}$ significance level at (11, 13, 17, 19) GHz respectively. Median polarization fractions are in the 2.8–4.7 per cent range in the 11–19 GHz frequency interval. We do not distinguish between Galactic and extragalactic sources here. The results presented here are consistent with those reported in the literature for flat- and steep-spectrum radio sources.
WMAP 3-yr primordial power spectrum Bridges, M.; Lasenby, A. N.; Hobson, M. P.
Monthly Notices of the Royal Astronomical Society,
10/2007, Letnik:
381, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We constrain the form of the primordial power spectrum using Wilkinson Microwave Anisotropy Probe (WMAP) 3-yr cosmic microwave background (CMB) data (plus other high resolution CMB experiments) in ...addition to complementary large-scale structure (LSS) data: 2dF, Sloan Digital Sky Survey (SDSS), Ly α forest and luminous red galaxy (LRG) data from the SDSS catalogue. We extend the work of the WMAP team to that of a fully Bayesian approach whereby we compute the comparative Bayesian evidence in addition to parameter estimates for a collection of seven models: (i) a scale-invariant Harrison –Zel'dovich (HZ) spectrum; (ii) a power law; (iii) a running spectral index; (iv) a broken spectrum; (v) a power law with an abrupt cut-off on large scales; (vi) a reconstruction of the spectrum in eight bins in wavenumber and (vii) a spectrum resulting from a cosmological model proposed by Lasenby & Doran (LD). Using a basic data set of WMAP3 + other CMB + 2dF + SDSS, our analysis confirms that a scale-invariant spectrum is disfavoured by between 0.7 and 1.7 units of log evidence (depending on priors chosen) when compared with a power-law tilt. Moreover, a running spectrum is now significantly preferred, but only when using the most constraining set of priors. The addition of both Lyα and LRG data independently suggests much lower values of the running index than with basic data set alone, and interestingly the inclusion of Lyα significantly disfavours a running parametrization by more than a unit in log evidence. Overall, the highest evidences, over all data sets, were obtained with a power-law spectrum containing a cut-off with a significant log evidence difference of roughly 2 units. The natural tilt and exponential cut-off present in the LD spectrum is found to be favoured decisively by a log evidence difference of over 5 units, but only for a limited study within the best-fitting concordance cosmology.
We report new galaxy clusters previously unknown included in the first
Planck
Sunyaev–Zeldovich (SZ) sources catalogue, the PSZ1. The results presented here were achieved during the second year of a ...two-year observational programme, the ITP13, developed at the Roque de los Muchachos Observatory (La Palma, Spain). Using the 2.5 m
Isaac Newton
telescope, the 3.5 m Telescopio Nazionale
Galileo
, the 4.2 m
William Herschel
telescope and the 10.4 m Gran Telescopio Canarias we characterised 75 SZ sources with low SZ significance, SZ
S
/
N
< 5.32. We performed deep optical imaging and spectroscopy in order to associate actual galaxy clusters with the SZ
Planck
source. We adopted robust criteria, based on the 2D spatial distribution, richness, and velocity dispersions to confirm actual optical counterparts up to
z
< 0.85. The selected systems are confirmed only if they are well aligned with respect to the PSZ1 coordinate and show high richness and high velocity dispersion. In addition, we also inspected the Compton
y
-maps and SZ significance in order to identify unrealistic detections. Following this procedure, we identify 26 cluster counterparts associated with the SZ emission, which means that only about 35% of the clusters considered in this low S/N PSZ1 subsample are validated. Forty-nine SZ sources (∼65% of this PSZ1 subset) remain unconfirmed. At the end of the ITP13 observational programme, we have studied 256 SZ sources with Dec ≥ −15° (212 of them completely unknown), finding optical counterparts for 152 SZ sources. The ITP13 validation programme has allowed us to update the PSZ1 purity, which is now more refined, increasing from 72% to 83% in the low SZ S/N regime. Our results are consistent with the predicted purity curve for the full PSZ1 catalogue and with the expected fraction of false detections caused by the non-Gaussian noise of foreground signals. We find a strong correlation between the number of unconfirmed sources and the thermal emission of diffuse galactic dust at 857 GHz, thus increasing the fraction of false
Planck
SZ detections at low galactic latitudes.
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