Found 27 talks width keyword CMB
I will review the status of the QUIJOTE (Q-U-I JOint TEnerife) experiment, a project led from the IAC with the aim of characterising the polarisation of the Cosmic Microwave Background (CMB) and other galactic or extragalactic physical processes that emit in microwaves in the frequency range 10-42GHz, and at large angular scales (1 degree resolution). QUIJOTE consists of two telescopes and three instruments operating from the Teide Observatory, and started operations about 10 years ago, in November 2012.
I will discuss the status of the project, and I will present the latest scientific results associated with the wide survey carried out with the first QUIJOTE instrument (MFI) at 11, 13, 17 and 19GHz, covering approximately 29000 deg$^2$ with polarisation sensitivities in the range of 35-40 $\mu$K/deg. These MFI maps provide the most accurate description we have of the polarization of the emission of the Milky Way in the microwave range, in a frequency domain previously unexplored by other experiments. These maps provide a unique view of the Galactic
magnetic field as traced by the synchrotron emission. These results have been presented in an initial series of 6 scientific articles published on January 12th, 2023.
Finally, I will describe the prospects for future CMB observations from the Teide Observatory.
Cosmological observations (redshifts, cosmic microwave background radiation, abundance of light elements, formation and evolution of galaxies, large-scale structure) find explanations within the standard Lambda-CDM model, although many times after a number of ad hoc corrections. Nevertheless, the expression ‘crisis in cosmology’ stubbornly reverberates in the scientific literature: the higher the precision with which the standard cosmological model tries to fit the data, the greater the number of tensions that arise. Moreover, there are alternative explanations for most of the observations. Therefore, cosmological hypotheses should be very cautiously proposed and even more cautiously received.
There are also sociological and philosophical arguments to support this scepticism. Only the standard model is considered by most professional cosmologists, while the challenges of the most fundamental ideas of modern cosmology are usually neglected. Funding, research positions, prestige, telescope time, publication in top journals, citations, conferences, and other resources are dedicated almost exclusively to standard cosmology. Moreover, religious, philosophical, economic, and political ideologies in a world dominated by anglophone culture also influence the contents of cosmological ideas.
The search for the primordial B-modes polarization in the cosmic microwave background (CMB) radiation,
carrying the signature of the primordial gravitational waves from the inflation epoch, motivated a significant
technological progress enabling the next generation of CMB instruments (e.g. CMB-S4, LiteBIRD)
to reach an unprecedented sensitivity. However, such a challenging detection demands a very high control
of the instrumental systematics and CMB foreground emissions.
Among those, the galactic dust polarized emission spectral dependence, not yet fully
characterized, could leave a high level of uncertainty in the cosmological polarization data
producing an ambiguous detection of the CMB B-modes.
Characterizing the dust spectral energy distribution (SED) spatial variations became one of
the most critical issues in the quest for primordial B-modes.
In the work that I will present we have used the release of the Planck satellite HFI data
obtained with the software Sroll2 (Delouis+2019, A&A 629, A38), in order to characterize
and compare the SEDs for polarization and total intensity.
The mean SEDs for dust polarization and total intensity from 353 to 100 GHz are confirmed
to be remarkably close. However, the data show evidence for spatial variations of the
polarization SED. These variations are correlated with variations of dust temperature
measured on total intensity data but the correlation is tight only in the Galactic plane.
At higher latitudes, by considering 90% of useful sky fraction and less, the amplitude of the dust
emission residuals in polarization suggests that an additional contribution, coming from
variations of the polarization angle, becomes dominant. Current models, which extrapolate
the SED spatial variations from total intensity to polarization, would be therefore grossly
simplifying and underestimating the foreground signal to CMB polarization.
In cosmology, it is customary to convert observed redshifts into distances in order to study the large scale distribution of matter probes like galaxies and quasars, and to obtain cosmological constraints thereof. In this talk, I describe a new approach which bypasses such conversion and studies the "field of redshifts" as a new cosmological observable, dubbed thereafter as angular redshift fluctuations (ARF). By comparing linear theory predictions to the output of N-body cosmological simulations, I will show how the ARF are actually sensitive to both the underlying density and radial peculiar velocity fields in the universe, and how one can obtain cosmological and astrophysical constraints from them. And since "the prove of the pudding is in the eating", I will demonstrate how ARF provide, under a very simple setup, competitive constraints on the nature of peculiar velocities and gravity from BOSS DR13 data. Furthermore, I will also show that by combining ARF with maps of the cosmic microwave background (CMB), we can unveil the signature of the missing (and moving) baryons, doubling the amount of detected baryons in disparate cosmic epochs ranging from z=0 up to z=5, and providing today's most precise description of the spatial distribution of baryons in the universe.
In this talk, we shall review the impact of the neutrino properties on the different cosmological observables. We shall also present the latest cosmological constraints on the neutrino masses and on the effective number of relativistic species. Special attention would be devoted to the role of neutrinos in solving the present cosmological tensions.
Dr Roger Hoyland has been working at the IAC for the last 21 years on the Cosmic Microwave Background Experiments. He started out as a research assistant at Jodrell Bank, University of Manchester, near his home town. His expertise lies in sensitive microwave radiometer design. He has worked on various projects such as the Tenerife Experiments, The Planck Surveyor Mission and The QUIJOTE project.
This talk is for the general public (even if mostly scientific) and aims to explain some of the misunderstandings and myths about microwave devices that we use in our everyday life. There are many YouTube videos about the effects of microwaves but which do you believe? Does your mobile phone really cause interference in an airplane? Can you really destroy your credit card by carrying it next to your mobile? Does the EMP bomb really exist? All this and more…………….
With the help of several live experiments and some audience participation (be prepared!) you will find out the science behind the myths around mobiles, microwave ovens and other microwave devices.
PS: Please bring along your mobile phone if you have one.
The ``dark flow'' dipole is a statistically significant dipole found at the position of galaxy clusters in filtered maps of Cosmic Microwave Background (CMB) temperature anisotropies. The dipole measured in WMAP 3, 5 and 7 yr data releases was roughly aligned with the all-sky CMB dipole and correlated with cluster X-ray luminosity. We analyzed the final WMAP 9 yr and the first Planck data releases using a catalog of 980 clusters outside the Kp0 mask to test our earlier findings. The dipoles measured on these new data sets are fully compatible with our earlier estimates, being similar in amplitude and direction to our previous results and in disagreement with the results of an earlier study by the Planck Collaboration. Further, in Planck data dipoles are independent of frequency, ruling out the Thermal Sunyaev-Zeldovich as the source of the effect. The signal is dominated by the most massive clusters, with a statistical significance better than 99%, slightly larger than in WMAP. Since both data sets differ in foreground contributions, instrumental noise and other systematics, the agreement between WMAP and Planck dipoles argues against them being due to systematic effects in either of the experiments.
We have learned a great deal about the universe from measurements ofthe cosmic microwave background (CMB). Most of what we have learned so far has been based on the temperature anisotropy combined with measurements of the polarization at angular scales of roughly 10 degrees. We are entering a new era in which the polarization of the CMB will be measured to high accuracy especially at degree angular scales and smaller. With the polarization we can, for example, measure or limit the presence of gravitational radiation from the early universe and determine the sum of the neutrino masses. The polarization will also give us a new way to determine the cosmological parameters. We review recent results on the CMB polarization with anemphasis on those from the Atacama Cosmology Telescope (ACT) project.
On March 17 the team responsible for the BICEP2 experiment, a CMB telescope located in the South Pole, announced the discovery of the primordial B-mode signal in the CMB polarization. This discovery inmediatly had a well-deserved impact in the media world-wide. In fact, it is the first observational confirmation of a prediction from the inflationary model, which was proposed at the beginning of the 80s as a solution for some inconsistencies of the Big Bang model. In this talk I will put this discovery in the context of CMB research, with a historical perspective. I will emphasize the importance of this discovery for Cosmology, and for Fundamental Physics, and will finally comment the prospects for the future, in particular the role of experiments like Quijote that have to confirm this signal.
Next generation of CMB experiments will require a large number of detectors (few tens of thousands) in order to tackle the challenging detection of primordial polarization B modes. Furthermore, high resolution experiments are needed for a detailed study of high redshift objects including clusters of galaxies, proto-clusters and dusty galaxies. Within this context Kinetic Inductance Detectors (KIDs) are a serious alternative to bolometers at millimetre wavelengths. Indeed, KIDs are naturally multiplexed and compact allowing us to construct arrays of thousands of detectors. Furthermore, KIDs present short time constants (below 1 ms) and have been demonstrated to be background limited on ground based observations. The NIKA camera, made of two matrices (200 KIDs each) operated at 140 and 240 GHz, has been installed successfully at the IRAM 30 m telescope in Pico Veleta, Granada. NIKA has provided the first ever scientific quality astrophysical observations with KIDs. In particular RXJ1347.5-1145, a massive intermediate redshift galaxy cluster at z = 0.4516 undergoing a merging event, has been successfully mapped at 12 arcsec resolution by NIKA. NIKA is a general purpose camera and it can be also used for other astrophysical objectives including for example observations of high redshift galaxies and proto-clusters, and detailed intensity and polarisation mapping of star-forming regions in the Galaxy. NIKA is a prototype of the NIKA2 camera that should be installed in 2015 at the IRAM 30 m telescope. NIKA2 should have 2 frequency bands at 150 and 250 GHz with about 5000 detectors in total and polarisation capabilities. NIKA2 will be well-suited for in-depth studies of the Intra Cluster Medium in intermediate to high redshift clusters and the follow-up of clusters and proto-clusters newly discovered by the Planck satellite. Finally, we discuss the possibility of including KIDs in the next generation of CMB satellites as for example PRISM.
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- Ultra-Diffuse Galaxies (UDGs) and the Stellar Mass – Halo Mass Relationship Dr. Jonah GannonTuesday June 6, 2023 - 12:30 GMT+1 (Aula)
- The complex Milky Way historyDr. Cristina ChiappiniThursday June 8, 2023 - 10:30 GMT+1 (Aula)