Archivi tag: Galaxies

IAU 309: Galaxies in 3D across the Universe

A new epoch with unbiased investigations of intrinsic properties of galaxies and their evolution has just started. High performance technology in 3D-spectroscopy in the optical/NIR regime and in radio interferometry allows for the first time the efficient mapping of stars, gas, and dust, in galaxies near and far. Detailed measurements of individual objects are complemented by surveys aiming at a full census of galaxies across the local Universe. Reaching out to the limits of the Universe, the evolution of spatially resolved properties is traced along the whole cosmic history. Likewise to these observational campaigns, new computer technology and highly advanced algorithms are exploited for detailed simulations to probe the underlying physical and cosmological connection.

Continua a leggere IAU 309: Galaxies in 3D across the Universe

The X-ray Universe

The XMM-Newton Science Operations Centre is organising a major astrophysical symposium from Monday 16th to Thursday 19th of June 2014 in Dublin, Ireland. The symposium is the fourth international meeting in the series “The X-ray Universe”. The intention is to gather a general collection of research in high energy astrophysics. The symposium will provide a showcase for results, discoveries and expectations from current and future X-ray missions. Continua a leggere The X-ray Universe

Galaxy formation and evolution from the early universe to today

Understanding how galaxies form in the early universe and how they evolve through cosmic time is one of the main aims of modern cosmology. In the past decade astrophysical research has clearly demonstrated that a panchromatic – X-ray to radio – observational approach is key to developing a consensus on galaxy evolution and formation. Continua a leggere Galaxy formation and evolution from the early universe to today

Simulating the first realistic cosmic web

Un gruppo di ricercatori guidati da Mark Vogelsberger dell’Harvard-Smithsonian Center for Astrophysics, in collaborazione con l’Heidelberg Institute for Theoretical Studies in Germania, hanno realizzato la prima mappa virtuale, alquanto realistica, dell’Universo utilizzando una simulazione numerica denominata “Illustris“. Il modello ha permesso di ricreare uno spazio cubico di lato pari a 350 milioni di anni-luce in un intervallo di tempo di circa 13 miliardi di anni e con una  risoluzione senza precedenti.

Continua a leggere Simulating the first realistic cosmic web

Discovered a new galaxy lens magnifying a distant supernova

Schematic illustration of the magnification by a galaxy. A massive object between us and the supernova bends light rays much as a glass lens can focus light. As more light rays are directed toward the observer than would be without the lens, the supernova appears magnified. (Credit: Kavli IPMU)

A team of researchers led by Robert Quimby at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) has announced the discovery of a galaxy that magnified a background, Type Ia supernova thirtyfold through gravitational lensing. This is the first example of strong gravitational lensing of a supernova confirms the team’s previous explanation for the unusual properties of this supernova.

More at IPMU: COSMIC ILLUSION REVEALED: GRAVITATIONAL LENS MAGNIFIES SUPERNOVA

arXiv: Detection of the Gravitational Lens Magnifying a Type Ia Supernova

Making ‘your own’ Universe at home

An image of a simulated cluster of galaxies captured when the Universe was half its present age, as seen through the TAO virtual telescope module. Credit: TAO

La Swinburne University of Technology ha ideato un programma virtuale di astronomia che permetterà agli scienziati di ricostruire una serie di visualizzazioni complesse, e a piacere, dell’Universo. Tutto ciò si potrà fare da casa con il proprio computer.

The Theoretical Astrophysical Observatory (TAO), funded by the Australian Government’s $48 million NeCTAR project, draws on the power of Swinburne’s gSTAR GPU supercomputer to allow astronomers to simulate the Universe and see how it would look through a wide range of telescopes. “TAO lets researchers take the data from massive cosmological simulations and map it onto an observer’s viewpoint, to test theories of how galaxies and stars form and evolve”, TAO project scientist, Swinburne Associate Professor Darren Croton, said. “TAO makes it easy and efficient for any astronomer to create these virtual universes. It’s the culmination of years of effort that is now at the fingertips of scientists around the world. Using TAO it might take a few minutes to create a mock catalogue of galaxies, versus months or even years of development previously“. Swinburne worked with eResearch company Intersect Australia Ltd, who designed the web interface with simplicity and user-friendliness in mind. Associate Professor Croton said that “it was important to create a service that could be used by any astronomer regardless of their area of expertise, because that accelerates the pace of science and boosts the chance of breakthroughs”. As new survey telescopes and instruments become available, they can be modelled within TAO to maintain an up-to-date set of observatories. “TAO could be especially useful for comparing theoretical predictions against observations coming from next-generation survey telescopes, like the Australian Square Kilometre Array Pathfinder (ASKAP) in Western Australia, and the SkyMapper Telescope run by the Australian National University (ANU). These will cover large chunks of the sky and peer back into the early stages of the Universe and are tasked with answering some of the most fundamental questions know to humankind”.

Swinburne University: Creating virtual universes with Swinburne's Theoretical Astrophysical Observatory

The decay of sterile neutrinos as signal of dark matter presence

Un gruppo di astrofisici dell’Università di Leiden, guidati da Alexey Boyarsky, potrebbero aver identificato alcune tracce della presenza di materia scura attraverso la rivelazione di una nuova particella, il neutrino sterile, un ipotetico tipo di neutrino che non interagisce con nessuna delle interazioni fondamentali. Intanto, qualche giorno fa, un altro gruppo di ricercatori di Harvard hanno riportato risultati simili.

The two groups this week reported that they have found an indirect signal from dark matter in the spectra of galaxies and clusters of galaxies. They made this discovery independent of one another, but came to the same conclusion: a tiny spike is hidden in the X-ray spectra of the Perseus galaxy cluster, at a frequency that cannot be explained by any known atomic transition. The Harvard group see the same spike in many other galaxy clusters, while Boyarsky also finds it in the nearby Andromeda galaxy. The researchers put it down to the decay of a new kind of neutrino, called ‘sterile’ because it has no interaction with other known neutrinos.

A sterile neutrino does have mass, and so could be responsible for the missing dark matter.

The first indications for the existence of dark matter in space were found more than eighty years ago, but there are still many questions surrounding this invisible matter. Sterile neutrinos are a highly attractive candidate for the dark matter particle, because they only call for a minor extension of the already known and extensively tested standard model for elementary particles. Boyarsky and his colleagues have already had this extension of the standard model ready for some time, but were waiting for the first observation of the mysterious particle. Measurements at higher resolution will shed light on the matter, and there is reason to hope that the spectral line just discovered will finally eliminate the problem of the missing mass.

University of Leiden: Glimmer of light in the search for dark matter

arXiv: An unidentified line in X-ray spectra of the Andromeda galaxy and Perseus galaxy cluster 

arXiv: Detection of An Unidentified Emission Line in the Stacked X-ray spectrum of Galaxy Clusters

Tribes of the deep sky

The distribution of galaxies populating the largest scale structures in the Universe today are visible different than the population in lower density environments.  From massive brightest cluster galaxies existing in the cores of groups and clusters to the increasing number of dwarf galaxies with density, multi-wavelength studies of clusters shed light on how these different populations have formed and currently evolving.   In order to understand the evolution of galaxies in these high density environments, it is critical to construct a coherent picture of the different populations between today and the high redshift Universe.
This conference will focus on comparing multi-wavelength observations of populations in clusters and groups to state of the art theoretical predictions. Topics for the conference will include:
  • Brightest Cluster Galaxies
  • Quiescent Populations
  • Star forming galaxies
  • Active Galactic Nuclei
  • Dwarf galaxies
We hope to explore both the interplay between these different types as well as looking at how these populations evolve from clusters seen today to high redshift proto-clusters.

Exploring the properties of the Universe by Doppler lensing

Sappiamo che l’Universo contiene centinaia di miliardi di galassie, basti guardare le spettacolari immagini che ci ha fornito il telescopio spaziale Hubble. Ce ne sono tante di diverse forme e dimensioni, ma quali sono in definitiva quelle più grandi? E poi, quali sono quelle più vicine alla nostra galassia che sembrano apparentemente più grandi delle altre? Naturalmente, non è possibile rispondere a queste domande analizzando semplicemente le immagini astronomiche poichè, di fatto, è necessario conoscere le distanze a cui si trovano le galassie in modo tale da ricavare una stima delle loro dimensioni reali.

Astronomers have their ways to measure a distance to a galaxy which allows them to solve this conundrum. One of the most popular methods, and in most cases, the only method that can be used to measure a distance to a remote galaxy, is to analyse its electromagnetic spectrum which includes the visible light that enables us to see it. Since the Universe is expanding, all distant galaxies are moving away from us. Because of this motion the spectrum of a galaxy is shifting towards its red part, the redshift as it is known to astronomers. The redshift phenomenon is a manifestation of the Doppler effect, the faster the motion, the larger the shift of the frequency. Therefore, the larger the redshift, the greater the distance to the observed galaxy. The exact relation between the redshift and distance follows from the cosmological model of the Universe. So if astronomers can measure a distance in some other way, then by comparing the observed distance and redshift with a prediction, they can measure the properties of our Universe such as for example the amount of dark matter and dark energy. There is, however, one problem here.

If a galaxy is moving on the top of the global expansion of the Universe, then this motion, via the Doppler effect, contributes to the observed redshift. And galaxies move all the time, just as molecules of the air, or bees within a swarm. The contribution from this local motion is not big if compared to a motion that follows from the expansion of the Universe. Still this additional redshift introduces noise to our measurements. This noise then distorts our estimation of the distance, and therefore our estimation of the real size of the observed galaxy. This is what is called the Doppler lensing, “Doppler” because of the Doppler effect involved, and “lensing” because this effect distorts the inferred size, just as the observed size of an object is distorted when observed through an optical lens. How then can we tell what is the real size of a galaxy? If all galaxies are moving and if their motion distorts our measurements then that sounds like a real mess. However, this “mess” or to be precise the amount of “messiness” can give us a very good insight into what our Universe is made of. Astronomers are now in a situation similar to radar operators who during World War II complained about “noise” in returned echoes due to rain, snow, and sleet. Back then it was a nuisance, now we actually look for this “noise” in order to predict weather. Similarly, if astronomers could measure apparent sizes of a very large number of galaxies, and correlations between them, then they could estimate an average amplitude of the “noise”. Using the technique based on the Doppler lensing effect, they can measure properties of our Universe and estimate how much dark matter and dark energy it contains.

With large galaxy surveys such as Dark Energy Survey (DES) and the contribution from the Australian OzDES we will be able to measure this effect. Further, much larger surveys will follow after completion of the Square Kilometre Array (SKA) telescope, currently being built partly in Western Australia and partly in South Africa, and utilise the Doppler lensing effect to get a better insight into properties and mysteries of our Universe. The calculations and the method itself were recently developed by a group of astronomers from Australia, South Africa, and United Kingdom. The method shows how by measuring correlations in the distortion of sizes of galaxies we can learn about the properties of our Universe (such as amount of dark matter and dark energy). This method and predictions that follow from this method will be presented today at the 8th Workshop of the Australian National Institute for Theoretical Astrophysics (ANITA) hosted by the Sydney Institute for Astronomy (SIfA) at the University of Sydney.

The Conversation: The measure of the universe through doppler lensing

arXiv: Cosmology with Doppler Lensing

Massive or massless neutrinos?

Gli scienziati avrebbero risolto uno dei problemi aperti dell’attuale modello cosmologico standard combinando i dati del satellite Planck e quelli ottenuti grazie al fenomeno della lente gravitazionale allo scopo di determinare la massa dei neutrini.

The team, from the universities of Nottingham and Manchester, used observations of the Big Bang and the curvature of spacetime to accurately measure the mass of these elementary particles for the first time. The recent Planck spacecraft observations of the Cosmic Microwave Background (CMB), the fading glow of the Big Bang, highlighted a discrepancy between these cosmological results and the predictions from other types of observations. The CMB is the oldest light in the Universe, and its study has allowed scientists to accurately measure cosmological parameters, such as the amount of matter in the Universe and its age. But an inconsistency arises when large-scale structures of the Universe, such as the distribution of galaxies, are observed. Dr Adam Moss, from The University of Nottingham’s School of Physics and Astronomy said: “We observe fewer galaxy clusters than we would expect from the Planck results and there is a weaker signal from gravitational lensing of galaxies than the CMB would suggest. A possible way of resolving this discrepancy is for neutrinos to have mass. The effect of these massive neutrinos would be to suppress the growth of dense structures that lead to the formation of clusters of galaxies.” Neutrinos interact very weakly with matter and so are extremely hard to study. They were originally thought to be massless but particle physics experiments have shown that neutrinos do indeed have mass and that there are several types, known as flavours by particle physicists. The sum of the masses of these different types has previously been suggested to lie above 0.06 eV (much less than a billionth of the mass of a proton). Dr Moss and Professor Richard Battye from The University of Manchester have combined the data from Planck with gravitational lensing observations in which images of galaxies are warped by the curvature of spacetime.

They conclude that the current discrepancies can be resolved if massive neutrinos are included in the standard cosmological model.

They estimate that the sum of masses of neutrinos is 0.320 +/- 0.081 eV (assuming active neutrinos with three flavours). Professor Battye added: “If this result is borne out by further analysis, it not only adds significantly to our understanding of the sub-atomic world studied by particle physicists, but it would also be an important extension to the standard model of cosmology which has been developed over the last decade”.

Nottingham University: Massive neutrinos solve a cosmological conundrum

arXiv: Evidence for massive neutrinos from CMB and lensing observations