Archivi tag: Galaxies

Science with the Atacama Pathfinder Experiment

After the success of the 2012 Ringberg meeting on APEX science where about 70 participants discussed exciting APEX science ranging from our Solar System to distant galaxies in the Early Universe, time is ripe to review what has been accomplished since then and to look into science opportunities for the next years. Since its inauguration in 2005, the Atacama Pathfinder Experiment (APEX) 12m submillimeter telescope has significantly contributed to a wide variety of submillimeter astronomy science areas, ranging from the discoveries of new molecules to large and deep imaging of the submillimeter sky. Among the partners the extension of APEX operations to 2017 and beyond is being prepared and new instruments are on their way and in the planning, including new wide-field bolometer cameras and new heterodyne instruments highly complementary to ALMA. While Herschel ran out of Helium, the work on its archival data benefits strongly from complementary APEX observations. SOFIA is collecting first exciting results where again lower frequency APEX studies needs to be added. With ALMA ramping up, we see already how important APEX is as a pathfinder for high angular resolution studies.

The conference venue Ringberg Castle will provide a unique setting for in depth discussions on current and future science with APEX. In particular, sessions on new scientific results, on synergies with other observatories and on APEX beyond 2015 are envisioned.

Astrophysical Turbulence: From Galaxies to Planets

In astrophysics and cosmology, fluid flow occurs on a large range of scales and under very different conditions, from the dense interior of stars and planets to the highly rarefied intergalactic medium. These flows share the fact that they are generally turbulent, i.e. highly disordered both in space and time. Turbulence is one of the key processes for the structure and evolution of a large variety of geo- and astrophysical systems. The universality of astrophysical turbulence interlinks the physics of the interior of planets or stars with proto-planetary or galactic disks, as well as the intergalactic gas outside of galaxies. For example, angular momentum transport by turbulence is a central question that must beanswered to understand how galaxies or stars form, how proto-planetary disks evolve, how metals are mixed in the interstellar and intergalactic medium, or how differential rotation is established in stars and planets. Magnetic field amplification through turbulent dynamo processes is ubiquitous in planets, stars, and galaxies. The onset of instabilities due to dust particles or newly formed planets in proto-planetary disks controls the properties of the evolving structures. We can observe a variety of interactions between stars, planets and galaxies with their environment leading to the exchange of energy and (angular-) momentum. This compilation highlights the enormous potential and perspective of a combined workshop/school to discuss and deepen our knowledge in this very rapidly moving field of research.

Multi-Spin Galaxies

Galaxies are the building blocks of the Universe: thus, in order to trace its evolution history one needs to understand how galaxies formed and evolved, in particular which are the main physical processes that have let to the observed structures.  The “classical” disk galaxies are made by stars, gas and dust which are distributed in a plane forming the disk: all these components co-rotating with the angular momentum vectors almost aligned.  A class of “peculiar” objects has also been observed, but significantly more rare than disk galaxies, that show a decoupled component of the angular momentum and so classified as “multi-spin galaxies” by V. Rubin in 1994. Up to date, this class of objects includes all galaxies with a kinematically distinct component of gas and/or stars, with several inclination angles and extensions with respect to the host galaxy: they are galaxies with extended polar rings/disks, inner polar disks, low-inclined rings, kinematically decoupled cores, and extended counter-rotating components. The observed phenomenon of warped gaseous and stellar disks is yet another example of misalignment between rotating components in a galaxy. Finally, recent findings show that even the Galaxy and M31  host a disk of satellites, possibly rationally supported, raising new questions and insights to the Λ-CDM models adopted in the “near-field cosmology.

Given that the decoupling of the angular momentum cannot be explained by the collapse of a single proto-galactic cloud, a “second event” need to be invoked in the formation history of the multi-spin galaxies, which could be galaxy-galaxy or galaxy-environment interactions. In the cold dark matter scenario for galaxy formation, such kind of gravitational interactions have played a fundamental role in defining the morphology of “normal” galaxies, in particular in the building up of spheroids: in this framework, the study of multi-spin galaxies, both at low and high redshift, can shed light on the main processes at work during galaxy interactions and on the influence of the environment. Moreover, the existence of two orthogonal components of the angular momentum in polar ring galaxies and the off-plane of gas in the warped disk galaxies, let these systems the ideal laboratory to study also the intrinsic shape of the dark matter halo. The question of the halo shape is important to constrain the dark matter models, through cosmological simulations which predict the distribution of the halo shapes and the universal radial mass density profile of the dark matter.

The conference will focus on the following topics:

1. PROPERTIES:

  1. -Morphological and photometric properties of multi-spin systems: inner polar disks, polar rings/disks, warped host and inclined rings
  2. -Kinematic signatures of extraplanar rings/disks along the Hubble sequence
  3. -Relative frequency and the impact of environment
  4. -Sizes, luminosities, chemical abundances and masses of the decoupled components
  5. -Correlations of spin component properties
  6. -The Milky Way as a multi-spin galaxy
  7. -High z multi-spin systems

2. STRUCTURE & FORMATION:

  1. -Density waves in counter-rotating stellar and gaseous disks
  2. -Time-scales and evolutionary paths: can we recognise transient features? Can we measure growth rates?
  3. -Warp structure & dynamics
  4. -Extreme warping
  5. -Star formation and stellar population of inclined and host rings/disks
  6. -Constraints on dark halos using extraplanar disks
  7. -Formation and evolution of inclined rings/disks

Dark Energy Survey ready to hunt for distant supernovae

La più grande ‘caccia’ alle supernovae sta per iniziare il prossimo mese di Agosto. Per cinque anni, il programma scientifico denominato Dark Energy Survey avrà lo scopo di esplorare le esplosioni stellari cosmiche che saranno utilizzate come ‘candele standard’ per misurare con una precisione sempre più elevata l’espansione dell’Universo. Lo scopo della survey è quello di ottenere nuovi dati per comprendere gli effetti dell’energia scura, quella enigmatica componente che sta determinando una espansione accelerata del cosmo.

DES is operated by an international collaboration of researchers from 25 institutions and consortia, including six universities in the UK. It will use a massive new 570 Megapixel camera (DECam) installed on the four-meter diameter Blanco telescope, high in the mountains of Chile. The instrument was commissioned in September and October 2012, and this was followed by a period of science verification from November through February 2013. “Thanks to the extreme sensitivity of the camera and to the large area of sky that can be imaged through the telescope at once (about 15 times the size of the full moon), we expect DES to find more supernovae than any previous experiment. During the verification phase, we have already identified at least 200 good candidates“, said Chris D’Andrea, a researcher at the University of Portsmouth’s Institute of Cosmology and Gravitation. More than just numerous, these supernovae are very old, with the light from the most distant having travelled towards Earth for over 8 billion years. Of particular interest are Type Ia supernovae, which all have nearly the same luminosity when they reach their brightest phase.

By comparing the brightness of Type Ia supernovae, scientists in DES will be able to determine accurately the distance to the supernovae and measure how the Universe has expanded over time.

This method was used in the Nobel Prize-winning research that led to the discovery of the accelerated expansion of the universe 15 years ago. While those researchers used a few dozen supernovae in their study, DES will find over 3500 of these objects. This glut of data poses a challenge for the team to analyse. “Traditionally, astronomers have identified supernovae by analysing the spectrum of light from candidates. Because DES will give us so many candidates – we already have hundreds just from the commissioning phase – we don’t have the resources to do this for each individual candidate supernova. We need to use other techniques to confirm which of the objects we observe really are exploding stars“, said D’Andrea. An alternative method for identifying supernovae is to monitor changes in the brightness and colour of their light over time. However, the scientists also need to know how much the Universe has expanded since the star exploded. This information can be gathered by analysing the spectra of light from galaxies in which supernovae have occurred, unlike a supernova, a galaxy does not quickly fade away. “DES is a long-term survey – we may not know whether some of our candidates are ‘real’ supernovae until the end of the project. However, in collaboration with Australian researchers, our team has recently been awarded 100 nights of time on a telescope in Australia over the next five years. The Anglo-Australian Telescope has the ability to take spectra of nearly 400 galaxies at the same time. With the first of these nights scheduled for September, it won’t be that long before we can start to accurately classify the supernovae candidates discovered in DES“, concluded D’Andrea.

RAS: Dark Energy Survey set to seek out supernovae

The New Standard Model of the Universe

The new concordance model in agreement with observations: ΛWDM (Lambda-dark energy- Warm Dark Matter). Recently, Warm (keV scale) Dark Matter emerged impressively over CDM (Cold Dark Matter) as the leading Dark Matter candidate. Astronomical evidence that Cold Dark Matter (LambdaCDM) and its proposed tailored cures do not work at galactic and small scales is staggering. LambdaWDM solves naturally the problems of LambdaCDM and agrees remarkably well with the observations at galactic and small as well as large and cosmological scales. In contrast, LambdaCDM simulations only agree with observations at large scales. In the context of this new Dark Matter situation, which implies novelties in the astrophysical, cosmological and keV particle physics context, this 17th Paris Colloquium 2013 is devoted to the LambdaWDM Standard Model of the Universe.

This Colloquium is within the astrofundamental physics spirit of the Chalonge School, focalised on recent observational and theoretical progress in the CMB, dark matter, dark energy, the new WDM framework to galaxy formation, and the theory of the early universe inflation with predictive power in the context of the LambdaWDM Standard Model of the Universe. The Colloquium addresses as well the theory and experimental search for the WDM particle physics candidates (keV sterile neutrinos). Astrophysical constraints including sterile neutrino decays points the sterile neutrino mass m around 2 keV. WDM predictions for EUCLID and PLANCK start to be available. MARE and an adapted KATRIN experiment could detect a keV sterile neutrino. A formidable WDM work to perform is ahead of us. In summary, the aim of the meeting is to put together real data : cosmological, astrophysical, particle, nuclear physics data, and hard theory predictive approach connected to them in the framework of the LambdaWDM Standard Model of the Universe.

Context, CDM crisis and the CDM decline: On large cosmological scales, CDM agrees in general with observations but CDM does not agree with observations on galaxy scales and small scales. Over most of twenty years, increasing number of cyclic arguments and ad-hoc mechanisms or recipes were-and continue to be- introduced in the CDM galaxy scale simulations, in trying to deal with the CDM small scale crisis: Cusped profiles and overabundance of substructures are predicted by CDM. Too many satellites are predicted by CDM simulations while cored profiles and no such overabundant substructures are seen by astronomical observations. Galaxy formation within CDM is increasingly confusing and in despite of the proposed cures, does not agree with galaxy observations. On the CDM particle physics side, the situation is no less critical: So far, all the dedicated experimental searches after most of twenty years to find the theoretically proposed CDM particle candidate (WIMP) have failed. The CDM indirect searches (invoking CDM annihilation) to explain cosmic ray positron excesses, are in crisis as well, as wimp annihilation models are plagued with growing tailoring or fine tuning, and in any case, such cosmic rays excesses are well explained and reproduced by natural astrophysical process and sources. The so-called and repeatedly invoked ‘wimp miracle’ is nothing but being able to solve one equation with three unknowns (mass, decoupling temperature, and annihilation cross section) within wimp models theoretically motivated by SUSY model building twenty years ago (at that time those models were fashionable and believed for many proposals). After more than twenty years -and as often in big-sized science-, CDM research has by now its own internal inertia: growing CDM galactic simulations involves large super-computers and large number of people working with, without agreement with the observations ; CDM particle wimp search involve large and long-time planned experiments, huge number of people, (and huge budgets) without producing wimp detection; one should not be surprised in principle, if a fast strategic change would not yet operate in the CDM and wimp research, although its interest would progressively decline.

Topics

  • Observational and theoretical progress on the nature of dark matter : keV scale warm dark matter
  • Cored density profiles in agreement with observations.
  • Large and small scale structure formation in agreement with observations at large scales and small (galactic) scales.
  • Warm (keV scale) dark matter from theory and observations.
  • The new quantum mechanical framework to galactic structure. WDM core sizes in agreement with observations.
  • Supermassive Black Holes : Theory and Observations. The clarifing and unifying WDM framework for stars, galaxies and cosmology.
  • Warm (keV scale) dark matter N-body simulations in agreement with observations.
  • Neutrinos in astrophysics and cosmology.
  • The new serious dark matter candidate: Sterile neutrinos at the keV scale.
  • Neutrinos mass bounds from cosmological data and from high precision beta decay experiments.
  • Dark energy: cosmological constant: the quantum energy of the cosmological vacuum.
  • The analysis of the CMB+LSS+SN data with the effective (Ginsburg-Landau) effective theory of inflation: New Inflation (double well inflaton potential) strongly favored by the CMB + LSS + SN data.
  • The presence of the lower bound for the primordial gravitons (non vanishing tensor to scalar ratio r) with the present CMB+LSS+SN data.
  • CMB news and polarization. Forecasts and Planck results.

Feeding, Feedback, and Fireworks

Late in June 2013, the Australian Astronomical Observatory (AAO) will be holding an international astronomy conference which will be hosted in the tropical paradise of Hamilton Island, Queensland, Australia. The meeting, entitled “Feeding, Feedback, and Fireworks: Celebrating Our Cosmic Landscape“, will be the 6th of the Southern Cross Conference Series, jointly supported by the AAO and CSIRO Astronomy and Space Science (CASS). The Southern Cross Astrophysics Conferences are held annually around Australia with the aim of attracting international experts with wide ranging skills to discuss a particular astrophysical topic. This conference will focus on galaxy evolution and how various feedback and feeding processes transfer energy into and out of galaxies. We intend to bring together observations, from radio to X-rays, and the best available theoretical models, to create a more complete picture of our cosmic landscape.

From Exoplanets to Distant Galaxies

The first international conference on the science of SPICA (Space Infrared Telescope for Cosmology and Astrophysics) mission will be held on 18-21 June, 2013. The conference is open to interested scientists from around the world. The primary aims of the conference are to introduce the scientific capabilities of the SPICA mission to the international community, and to foster interactions in the IR community on how to optimally utilise this new facility to further explore the physical processes in formation and evolution of planets, stars and galaxies.

Topics covered:

  • Galaxies formation and evolution as revealed in the infrared
  • The cycling of matter between stars, galaxies and the intergalactic medium
  • Planet formation and detection/Characterization of exoplanets

Cosmology in the Era of Extremely Large Telescopes

The Kavli Institute for Cosmological Physics (KICP) at the University of Chicago and GMTO are planning a joint workshop to be held in Chicago on June 10-12, 2013 (poster). The goal of the conference is to examine the role of galaxies as probes of cosmology, both today and in the future as large galaxy surveys and the next generation of large telescopes, in space and on the ground, come into being. We will bring together theorists and observers to discuss contemporary problems in cosmology and galaxy evolution as well as the opportunities offered by a new generation of facilities and surveys. The conference will be organized into five half-day sessions. Keynote speakers will provide an overview of the state of theory and observation in each subfield. Contributed lectures will delve into the details of front-line research issues. The first session will review relevant surveys and facilities, including the GMT, large imaging surveys such as the Dark Energy SurveyLSST, and Euclid among others, and upcoming missions, such as the James Webb Space Telescope. This will be followed by sessions on First-Light and Reionization of the Universe, Galaxy Formation and Assembly, Intergalactic and Circumgalactic Gas, and Galaxies & the Intergalactic medium as probes of Dark Matter and Dark Energy. The conference will be held in downtown Chicago at the University of Chicago’s Gleacher Center. A gala conference banquet will be held at the Adler Planetarium looking out on to Lake Michigan.

222° Meeting of the American Astronomical Society

One of the largest astronomy meetings of the year will open to the public for the first time in its history. More than 500 astronomers, journalists and guests will bring their cosmic know-how to Indianapolis next week for the 222nd meeting of the American Astronomical Society (AAS). The conference begins on Sunday (June 2) and runs through June 6 at the Indiana Convention Center; it is the second of two meetings held annually by the AAS. New findings about alien worlds, mysterious dark matter and the Milky Way will be discussed, and this year anyone can take part in the cosmic action. Several presentations on Monday and Tuesday will be geared toward amateurs that decide to pay the fee and attend. The presentations include information about the Hubble Space Telescope, nearby exoplanets, Pluto, and the formation of galaxies in the early universe. In addition to those talks, the society will also hold two free public events during the convention. Throughout the course of the conference, scientists will take part in town hall-style meetings about NASA, the National Science Foundation and other agencies. The latest findings from the badly damaged planet hunting Kepler Space Telescope will be presented as well. Twitter users can follow the conference using the hashtag #AAS222.

All the light in the Universe since the Big Bang

Vi siete mai chiesti quanta luce è stata emessa da tutte le galassie da quando è nato l’Universo? Pensate un attimo a ciascun fotone di qualsiasi lunghezza d’onda, dall’ultravioletto all’infrarosso, che sta viaggiano ancora nello spazio fino a raggiungere i nostri rivelatori. Se riuscissimo a misurare in maniera accurata il numero e l’energia di tutti i fotoni, non solo quelli dei nostri giorni ma anche quelli più antichi, potremmo ricavare indizi fondamentali sulla natura e l’evoluzione dell’Universo e comprendere come le galassie più antiche siano differenti rispetto a quelle che vediamo oggi.

That bath of ancient and young photons suffusing the Universe today is called the extragalactic background light (EBL). An accurate measurement of the EBL is as fundamental to cosmology as measuring the heat radiation left over from the Big Bang, the cosmic microwave background, at radio wavelengths. A new paper, called “Detection of the Cosmic γ-Ray Horizon from Multiwavelength Observations of Blazars”, by Alberto Dominguez at University of California at Riverside and six coauthors, based on observations spanning wavelengths from radio waves to very energetic gamma rays, obtained from several NASA spacecraft and several ground-based telescopes, describes the best measurement yet of the evolution of the EBL over the past 5 billion years. Directly measuring the EBL by collecting its photons with a telescope, however, poses towering technical challenges, harder than trying to see the dim band of the Milky Way spanning the heavens at night from midtown Manhattan. Earth is inside a very bright galaxy with billions of stars and glowing gas. Indeed, Earth is inside a very bright Solar System: sunlight scattered by all the dust in the plane of Earth’s orbit creates the zodiacal light radiating across the optical spectrum down to long-wavelength infrared. Therefore ground-based and space-based telescopes have not succeeded in reliably measuring the EBL directly. So, astrophysicists developed an ingenious work-around method: measuring the EBL indirectly through measuring the attenuation of, that is, the absorption of, very high energy gamma rays from distant blazars. Blazars are supermassive black holes in the centers of galaxies with brilliant jets directly pointed at us like a flashlight beam. Not all the high-energy gamma rays emitted by a blazar, however, make it all the way across billions of light-years to Earth; some strike a hapless EBL photon along the way. When a high-energy gamma ray photon from a blazar hits a much lower energy EBL photon, both are annihilated and produce two different particles: an electron and its antiparticle, a positron, which fly off into space and are never heard from again. Different energies of the highest-energy gamma rays are waylaid by different energies of EBL photons. Thus, measuring how much gamma rays of different energies are attenuated or weakened from blazars at different distances from Earth indirectly gives a measurement of how many EBL photons of different wavelengths exist along the line of sight from blazar to Earth over those different distances. Observations of blazars by NASA’s Fermi Gamma Ray Telescope spacecraft for the first time detected that gamma rays from distant blazars are indeed attenuated more than gamma rays from nearby blazars, a result announced on November 30, 2012, in a paper published in Science, as theoretically predicted. Now, the big news is that the evolution of the EBL over the past 5 billion years has been measured for the first time. That’s because looking farther out into the Universe corresponds to looking back in time. Thus, the gamma ray attenuation spectrum from farther distant blazars reveals how the EBL looked at earlier eras. This was a multistep process. First, the coauthors compared the Fermi findings to intensity of X-rays from the same blazars measured by X-ray satellites Chandra, Swift, Rossi X-ray Timing Explorer, and XMM/Newton and lower-energy radiation measured by other spacecraft and ground-based observatories. From these measurements, Dominguez and collaborators were able to calculate the blazars’ original emitted, unattenuated gamma-ray brightnesses at different energies. The coauthors then compared those calculations of unattenuated gamma-ray flux at different energies with direct measurements from special ground-based telescopes of the actual gamma-ray flux received at Earth from those same blazars. When a high-energy gamma ray from a blazar strikes air molecules in the upper regions of Earth’s atmosphere, it produces a cascade of charged subatomic particles. This cascade of particles travels faster than the speed of light in air, which is slower than the speed of light in a vacuum. This causes a visual analogue to a “sonic boom”: bursts of a special light called Čerenkov radiation. This Čerenkov radiation was detected by imaging atmospheric Čerenkov telescopes (IACTs), such as HESS (High Energy Stereoscopic System) in Namibia, MAGIC (Major Atmospheric Gamma Imaging Čerenkov) in the Canary Islands, and VERITAS (Very Energetic Radiation Imaging Telescope Array Systems) in Arizona. Comparing the calculations of the unattenuated gamma rays to actual measurements of the attenuation of gamma rays and X-rays from blazars at different distances allowed Dominquez and colleagues to quantify the evolution of the EBL, that is, to measure how the EBL changed over time as the Universe aged, out to about 5 billion years ago, corresponding to a redshift of about z = 0.5. “Five billion years ago is the maximum distance we are able to probe with our current technology”, Domínguez said. “Sure, there are blazars farther away, but we are not able to detect them because the high-energy gamma rays they are emitting are too attenuated by EBL when they get to us, so weakened that our instruments are not sensitive enough to detect them”. This measurement is the first statistically significant detection of the so-called “Cosmic Gamma Ray Horizon” as a function of gamma-ray energy. The Cosmic Gamma Ray Horizon is defined as the distance at which roughly one-third or, more precisely, 1/e, that is, 1/2.718 where “e” is the base of the natural logarithms, of the gamma rays of a particular energy have been attenuated. This latest result confirms that the kinds of galaxies observed today are responsible for most of the EBL over all time. Moreover, it sets limits on possible contributions from many galaxies too faint to have been included in the galaxy surveys, or on possible contributions from hypothetical additional sources, such as the decay of hypothetical unknown elementary particles.

UC-HiPACC: DETECTION OF THE COSMIC GAMMA RAY HORIZON MEASURES ALL THE LIGHT IN THE UNIVERSE SINCE THE BIG BANG
UCR: Astronomers Measure the Elusive Extragalactic Background Light
arXiv: Detection of the cosmic γ-ray horizon from multiwavelength observations of blazars