Archivi tag: galactic center

Revolution in Astronomy with ALMA

The Atacama Large Millimeter/submillimeter Array (ALMA) has been producing a growing number of impressive and scientifically compelling results as the most powerful mm/submm interferometer in the world. Held in central Tokyo, the aim of this four day conference is to highlight the most recent science results from ALMA obtained during the first three years of science operations, and to motivate future collaboration among researchers around the world. Continua a leggere Revolution in Astronomy with ALMA

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Extreme-Astrophysics in an Ever-Changing Universe

Since ancient times, astronomers’ attention has been drawn to changes in the sky. Today we know that most phenomena observed in “time-domain” astronomy are related to extreme astrophysical events or processes. Whether it is the explosion of stars in supernovae or the observations of flare stars, pulsars, gamma-ray bursts, blazars or active galactic nuclei, time-domain astronomy stretches across the whole electromagnetic spectrum and beyond. With increasing technical capabilities, the 21st century will see corresponding new instruments being developed or coming online, revolutionising our view of the ever-changing Universe. Continua a leggere Extreme-Astrophysics in an Ever-Changing Universe

Uncovering a gamma-ray excess at the galactic center

At left is a map of gamma rays with energies between 1 and 3.16 GeV detected in the galactic center by Fermi’s LAT; red indicates the greatest number. Prominent pulsars are labeled. Removing all known gamma-ray sources (right) reveals excess emission that may arise from dark matter annihilations. Image Credit: T. Linden, Univ. of Chicago
Grazie ad una serie di osservazioni del centro galattico eseguite con il telescopio spaziale Fermi ad opera di un gruppo di ricercatori appartenenti al Fermi National Accelerator Laboratory (Fermilab), all’Harvard-Smithsonian Center for Astrophysics (CfA), al Massachusetts Institute of Technology (MIT) e all’University of Chicago, emerge che l’eccesso di emissione di alta energia visibile di raggi gamma possa essere associato con qualche forma di materia scura, forse l’indizio più forte ad oggi in mano agli astronomi.

The new maps allow us to analyze the excess and test whether more conventional explanations, such as the presence of undiscovered pulsars or cosmic-ray collisions on gas clouds, can account for it“, said Dan Hooper, an astrophysicist at Fermilab in Batavia, Ill., and a lead author of the study. “The signal we find cannot be explained by currently proposed alternatives and is in close agreement with the predictions of very simple dark matter models“.

More at NASA: Fermi Data Tantalize With New Clues To Dark Matter

arXiv: The characterization of the gamma-ray signal from the central Milky Way: A compelling case for annihilating dark matter

 
The following animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray map of the galactic center from NASA’s Fermi. Raw data transitions to a view with all known sources removed, revealing a gamma-ray excess hinting at the presence of dark matter.
 

The Galactic Center Black Hole Laboratory

This event has spawned great activities in observing the Galactic Center covering the entire electromagnetic spectrum from radio, via infrared to X-ray wavelengths using telescopes across the world. Hence, in Granada we look forward to conclude the presumably fruitful research session on SgrA*. While the conference mainly aims at a first attempt to summarize this year’s observational results, matters need to be put into perspective. The nucleus of our Galaxy has an extremely low luminosity.  Although it also demonstrates that violent activities may take place at times. Hence, a comparison between the center of the Milky Way and the nuclei of galaxies hosting Low Luminosity Active Galactic Nuclei appears to be imperative.
In addition, it is time to review the current state of theoretical efforts. Emphasis will be given to the implications for our understanding of the feeding mechanism of Black Holes, the accretion phenomenon and the physical nature of the event horizon. The activity and properties of massive black holes are also intimately related to their surroundings. The conference will therefore also be dedicated to reviewing the most recent findings on star formation, properties of the ISM, magnetic fields, and stellar structure, kinematics, and dynamics near massive black holes. Simulations and theoretical predictions need to be compared to each other and source models for the Galactic Center and the interaction with its immediate environment need to be updated.

X-raying the Gamma-Ray Universe

Exploration of the high-energy Universe has experienced dramatic progress in recent years, spearheaded by the latest generation of X-ray and gamma-ray instruments. This trend looks to continue in the next decades, with a variety of advanced, new facilities being planned. Although the scientific link between the neighboring energy bands of X-rays and gamma rays has been invariably crucial, the growth and diversification of the fields has meant that the inter-communication nowadays among the respective communities is not always ideal. With a special focus on next-generation observatories of the near future such as the Cherenkov Telescope Array and ASTRO-H, this workshop aims to bring together experts in X-ray and gamma-ray astrophysics, in order to overview the latest observational and theoretical developments and intensify the inherently synergistic interplay between these fields.

Topics of the meeting will cover:

  • Gamma-ray universe: HESS, MAGIC, VERITAS, Cherenkov Telescope Array (CTA), etc.
  • X-ray universe: Chandra, XMM-Newton, Suzaku, NuStar, ASTRO-H, MAXI, etc.
  • Theory
  • Galactic sources: Supernova remnant, Pulsar, Pulsar wind nebula, Binary, Galactic center, Fermi bubble
  • Extragalactic sources: Gamma-ray burst, Active galactic nucleus, Star burst galaxy, Cluster, Background, Cosmic ray, Dark matter

IAU Symposium 303: The Galactic Center

Scientists are currently are at a crossroads in Galactic center research. Many recent large-scale surveys and wide-field studies of this unique and unusual region of the Galaxy have been made (using Chandra, HST/NICMOS, Spitzer, Fermi and numerous ground based observatories). Such surveys have provided us with multi-wavelength views of the stellar and interstellar environment in the central few hundred parsecs; additional surveys (filling in the gaps in the electromagnetic spectrum) are underway or being planned (EVLA, ALMA, Herschel, SOFIA, Planck, etc.). At the same time, unprecedented high-resolution views of the very central nuclear region are being constructed using the largest and most powerful telescopes on the ground (VLT-I, Keck, VLBA, EHT) providing us more details than ever before on the stellar population and the immediate environment of the 4 million solar mass black hole, SgrA*.

Many of the large- and small-scale phenomena observed are due to the influx of gas from the outer parts of the Galaxy and the feedback of energetic processes in the interstellar environment. Whereas the gas that resides in the Galactic Center represents about 10% of the the gas involved in star formation in the Galaxy, it only occurs in about 0.001% of the Galaxy’s volume. It is likely that this gas has funneled to its present location during episodes in the lifetime of our Galaxy’s bar. The gas in the Galactic Center is characterized by very high densities and turbulent conditions. The multi-phase gas is subject to strong and weak shocks as well as heating via dust, UV photons, cosmic rays and cloud-cloud collisions, all embedded within a strong and widespread magnetic field. Understanding the details of the interplay between stars and the interstellar medium and the role of cosmic rays in heating/interacting with the interstellar medium is crucial to our understanding of nuclear processes in many normal galaxies and in the cores of very distant galaxies.

During the meeting, we aim to bring together Galactic center researchers who are focused on trying to answer the following outstanding questions:

  • What are the detailed physical properties of the clouds in the Central Molecular Zone and what is the potential for forming stars in this environment?
  • What is the role of stellar feedback in our Galactic center and in starbursts?
  • How well do we understand the accretion processes around Sgr A*, and the inner pc’s of the Galactic center?
  • What tracers do we have of Sgr A*’s prior AGN-like history?   Are the Fermi bubbles related, or due to stellar processes?
  • What are we learning about the Galactic center environment from observations with new facilities such as ALMA, Fermi, NuSTAR, and new multiwavelength campaigns?

Massive Black Holes: Birth, Growth and Impact

During the past decade, massive black holes have become central objects of study in areas of astrophysics that were traditionally not connected. Along with traditional studies of black holes as high energy astrophysical sources, massive black holes have become pivotal to the understanding of galaxy formation and evolution. Similarly, massive black hole binaries have become the main targets of the future generation of gravitational wave experiments, motivating new research on the orbital decay and merging of black holes.  Finally, studies of our own Galactic Center have also undergone tremendous progress and are expected be able to probe general relativistic effects induced by the central supermassive black hole. With this conference, we will bring together experts from the diverse groups involved in the study of massive black holes, producing a novel summary of the status of knowledge and fostering a productive interaction between various research communities that normally operate separately.

Themes that we will focus on will include

(1) Formation mechanisms of massive black hole seeds, confronting weaknesses and strengths of different models and placing them in the context of cosmic structure formation.

(2) Co-evolution of galaxies and massive black holes, in particular the role of black hole feedback on galaxy formation.

(3) Evolution of massive black hole binaries, from the Newtonian to the relativistic regime, including predictions for gravitational wave experiments.

(4) Modeling of accretion discs, especially the latest generation of three-dimensional numerical simulations, addressing the state-of-the art in the field and discussing how to transfer the acquired knowledge to sub-grid models of black hole accretion during galaxy formation.

We expect the conference will generate the most up-to-date synthesis of our current knowledge on massive black holes.