54 research outputs found
A prescription for the conditional mass function of dark matter haloes
[ABRIDGED] The unconditional mass function (UMF) of dark matter haloes has
been determined accurately in the literature, showing excellent agreement with
high resolution numerical simulations. However, this is not the case for the
conditional mass function (CMF). We propose a simple analytical procedure to
derive the CMF by rescaling the UMF to the constrained environment using the
appropriate mean and variance of the density field at the constrained point.
This method introduces two major modifications with respect to the standard
re-scaling procedure. First of all, rather than using in the scaling procedure
the properties of the environment averaged over all the conditioning region, we
implement the re-scaling locally. We show that for high masses this
modification may lead to substantially different results. Secondly, we modify
the (local) standard re-scaling procedure in such a manner as to force
normalisation, in the sense that when one integrates the CMF over all possible
values of the constraint multiplied by their corresponding probability
distribution, the UMF is recovered. In practise, we do this by replacing in the
standard procedure the value delta_c (the linear density contrast for collapse)
by certain adjustable effective parameter delta_eff. In order to test the
method, we compare our prescription with the results obtained from numerical
simulations in voids (Gottlober et al. 2003), finding a very good agreement.
Based on these results, we finally present a very accurate analytical fit to
the (accumulated) conditional mass function obtained with our procedure, which
may be useful for any theoretical treatment of the large scale structure.Comment: 14 pages, 10 figures. Accepted for publication in MNRA
Experimental measurement of the quality factor of a Fabry-P\'erot open-cavity axion haloscope
The axion is a hypothetical boson arising from the most natural solution to
the problem of charge and parity symmetry in the strong nuclear force.
Moreover, this pseudoscalar emerges as a dark matter candidate in a parameter
space extending several decades in mass. The Dark-photons \& Axion-Like
particles Interferometer (DALI) is a proposal to search for axion dark matter
in a range that remains under-examined. Currently in a design and prototyping
phase, this haloscope is a multilayer Fabry-P\'erot interferometer. A
proof-of-principle experiment is performed to observe the resonance in a
prototype. The test unveils a quality factor per open cavity of a few hundred
over a bandwidth of the order of dozens of megahertz. The result elucidates a
physics potential to find the, so far elusive, axion, in a sector which can
simultaneously solve the symmetry problem in the strong interaction and the
enigma of dark matter.Comment: 5 pages, 6 figure
Cosmic microwave background polarization receivers: QUIJOTE experiment
The QUIJOTE (Q U I JOint TEnerife) Experiment will characterize the polarization of Cosmic Microwave Background radiation and other galactic and extragalactic emissions in the frequency range from 10 to 30 GHz, and at large angular scales. The polarimeter receivers at 11, 13, 17, 19 and 30 GHz are radiometers based on broadband waveguide rotating polar modulators and broadband orthomode transducers. High sensitivity of polarimeters is achieved with very low noise cryogenic amplifiers (Noise temperature < 15 K in 11-19 GHz channels and < 20 K in 30 GHz channel). Subsystems test results and integration measurements of front-end and back-end units show wideband operation in all channels.This work has been funded by the Ministerio de Educación y Ciencia (Spain) under Astronomy and Astrophysics program, reference AYA2007-68058-C03
A Very Small Array search for the extended Sunyaev-Zel'dovich effect in the Corona Borealis supercluster
We present interferometric imaging at 33 GHz of the Corona Borealis supercluster, using the extended configuration of the Very Small Array. A total area of 24 deg² has been imaged, with an angular resolution of 11 arcmin and a sensitivity of 12 mJy beam⁻¹. The aim of these observations is to search for Sunyaev-Zel'dovich (SZ) detections from known clusters of galaxies in this supercluster and for a possible extended SZ decrement due to diffuse warm/hot gas in the intercluster medium. Hydrodynamical simulations suggest that a significant part of the missing baryons in the Local Universe may be located in superclusters.
The maps constructed from these observations have a significant contribution from primordial fluctuations. We measure negative flux values in the positions of the 10 richest clusters in the region. Collectively, this implies a 3.0σ detection of the SZ effect. For two of these clusters, A2061 and A2065, we find decrements of approximately 2σ each.
Our main result is the detection of two strong and resolved negative features at −70 ± 12 mJy beam⁻¹ (−157 ± 27 μK) and −103 ± 10 mJy beam⁻¹ (−230 ± 23 μK), respectively, located in a region with no known clusters, near the centre of the supercluster. We discuss their possible origins in terms of primordial cosmic microwave background (CMB) anisotropies and/or SZ signals related either to unknown clusters or to a diffuse extended warm/hot gas distribution. Our analyses have revealed that a primordial CMB fluctuation is a plausible explanation for the weaker feature (probability of 37.82 per cent). For the stronger one, neither primordial CMB (probability of 0.38 per cent) nor SZ can account alone for its size and total intensity. The most reasonable explanation, then, is a combination of both primordial CMB and SZ signal. Finally, we explore what characteristics would be required for a filamentary structure consisting of warm/hot diffuse gas in order to produce a significant contribution to such a spot taking into account the constraints set by X-ray data
A Very Small Array search for the extended Sunyaev-Zel'dovich effect in the Corona Borealis supercluster
We present interferometric imaging at 33 GHz of the Corona Borealis supercluster, using the extended configuration of the Very Small Array. A total area of 24 deg² has been imaged, with an angular resolution of 11 arcmin and a sensitivity of 12 mJy beam⁻¹. The aim of these observations is to search for Sunyaev-Zel'dovich (SZ) detections from known clusters of galaxies in this supercluster and for a possible extended SZ decrement due to diffuse warm/hot gas in the intercluster medium. Hydrodynamical simulations suggest that a significant part of the missing baryons in the Local Universe may be located in superclusters.
The maps constructed from these observations have a significant contribution from primordial fluctuations. We measure negative flux values in the positions of the 10 richest clusters in the region. Collectively, this implies a 3.0σ detection of the SZ effect. For two of these clusters, A2061 and A2065, we find decrements of approximately 2σ each.
Our main result is the detection of two strong and resolved negative features at −70 ± 12 mJy beam⁻¹ (−157 ± 27 μK) and −103 ± 10 mJy beam⁻¹ (−230 ± 23 μK), respectively, located in a region with no known clusters, near the centre of the supercluster. We discuss their possible origins in terms of primordial cosmic microwave background (CMB) anisotropies and/or SZ signals related either to unknown clusters or to a diffuse extended warm/hot gas distribution. Our analyses have revealed that a primordial CMB fluctuation is a plausible explanation for the weaker feature (probability of 37.82 per cent). For the stronger one, neither primordial CMB (probability of 0.38 per cent) nor SZ can account alone for its size and total intensity. The most reasonable explanation, then, is a combination of both primordial CMB and SZ signal. Finally, we explore what characteristics would be required for a filamentary structure consisting of warm/hot diffuse gas in order to produce a significant contribution to such a spot taking into account the constraints set by X-ray data
The new multi-frequency instrument (MFI2) for the QUIJOTE facility in Tenerife
The QUIJOTE (Q-U-I joint Tenerife) experiment combines the operation of two radio-telescopes and three instruments working in the microwave bands 10?20 GHz, 26-36 GHz and 35-47 GHz at the Teide Observatory, Tenerife, and has already been presented in previous SPIE meetings (Hoyland, R. J. et al, 2012; Rubiño-Martín et al., 2012). The Cosmology group at the IAC have designed a new upgrade to the MFI instrument in the band 10-20 GHz. The aim of the QUIJOTE telescopes is to characterise the polarised emission of the cosmic microwave background (CMB), as well as galactic and extra-galactic sources, at medium and large angular scales. This MFI2 will continue the survey at even higher sensitivity levels. The MFI2 project led by the Instituto de Astrofísica de Canarias (IAC) consists of five polarimeters, three of them operating in the sub-band 10?15 GHz, and two in the sub-band 15-20 GHz. The MFI2 instrument is expected to be a full two-three times more sensitive than the former MFI. The microwave complex correlator design has been replaced by a simple correlator design with a digital back-end based on the latest Xilinx FPGAs (ZCU111). During the first half of 2019 the manufacture of the new cryostat was completed and since then the opto-mechanical components have been designed and manufactured. It is expected that the cryogenic front-end will be completed by the end of 2022 along with the FPGA acquisition and observing system. This digital system has been employed to be more robust against stray ground-based and satellite interference, having a frequency resolution of 1 MHz.The MFI2 instrument is being developed by the Instituto de Astrofisica de Canarias (IAC), with an instrumental participation from the Universidad Politecnica de Cartagena (UPCT). Partial financial support is provided by the Spanish Ministry of Science and Innovation (MICINN), under the projects AYA2017-84185-P, IACA15-BE-3707, EQC2018-004918-P and the FEDER Agreement INSIDE-OOCC (ICTS-2019-03-IAC-12). We also acknowledge
financial support of the Severo Ochoa Programs SEV-2015-0548 and CEX2019-000920-S
Source subtraction for the extended Very Small Array and 33-GHz source count estimates
We describe the source subtraction strategy and observations for the extended
Very Small Array, a CMB interferometer operating at 33 GHz. A total of 453
sources were monitored at 33 GHz using a dedicated source subtraction baseline.
131 sources brighter than 20 mJy were directly subtracted from the VSA
visibility data. Some characteristics of the subtracted sources, such as
spectra and variability, are discussed. The 33-GHz source counts are estimated
from a sample selected at 15 GHz. The selection of VSA fields in order to avoid
bright sources introduces a bias into the observed counts. This bias is
corrected and the resulting source count is estimated to be complete in the
flux-density range 20-114 mJy. The 33-GHz source counts are used to calculate a
correction to the VSA power spectrum for sources below the subtraction limit.Comment: 15 pages, 15 figures, submitted to MNRA
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