Tagged: Radio galaxies Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 8:40 am on March 30, 2017 Permalink | Reply
    Tags: , , , Radio galaxies, , TXS 0828+193, TXS0211−122   

    From Keck and IAC via phys.org: “Expanding super bubble of gas detected around massive black holes in the early universe” 

    Keck Observatory

    Keck Observatory.
    Keck, with Subaru and IRTF (NASA Infrared Telescope Facility). Vadim Kurland

    Keck Observatory

    2

    Instituto de Astrofísica e Ciências do Espaço

    phys.org

    1
    Left – Composite image of a large gas blob of glowing hydrogen gas, shown by a Lyman-alpha optical image (colored yellow) from the Subaru telescope (NAOJ). A galaxy located in the blob is visible in a broadband optical image (white) from the Hubble Space Telescope and an infrared image from the Spitzer Space Telescope (red). Finally, the Chandra X-ray Observatory image in blue shows evidence for a growing supermassive black hole in the center of the galaxy. Radiation and outflows from this active black hole are powerful enough to light up and heat the gas in the blob.

    In a study led by Sandy Morais, a PhD student at Instituto de Astrofísica e Ciências do Espaço and Faculty of Sciences of the University of Porto (FCUP), researchers found massive super bubbles of gas and dust around two distant radio galaxies about 11.5 billion light years away.

    Andrew Humphrey (IA & University of Porto), the leader of the project, commented: “By studying violent galaxies like these, we have gained a new insight into the way supermassive black holes affect the evolution of the galaxies in which they reside.”

    The researchers used two of the largest observatories available today, the Keck II (Hawaii) and the Gran Telescópio de Canárias (GTC), to observe TXS0211−122 and TXS 0828+193, two powerful radio galaxies, harboring the most energetic type of Active Galactic Nuclei (AGN) known. This type of galaxy houses the most massive black holes and have the most powerful continuous energy ejections known.

    The team discovered expanding super bubbles of gas around each of TXS 0211-122 and TXS 0828+193, most likely caused by “feedback” activity whereby the AGN injects vast quantities of energy into its host galaxy, creating a powerful wind that sweeps up gas and dust into an expanding super bubble.

    Study of the symbiosis between the supermassive black hole and the galaxy is a key to understanding the evolution of the most massive galaxies. Ultraviolet emission from the black hole’s accretion disk can inhibit star formation temporarily, by ionizing the Interstellar medium, and the great outflows of gas towards the black hole can lead to permanent inhibition of star formation.

    1
    Schematic of the expanding gas Bubble, over a radio image of the full field of TXS 0828+193. Credit: Morais et al. 2017

    More information: S. G. Morais et al. Ionization and feedback in Lyα haloes around two radio galaxies at∼ 2.5, Monthly Notices of the Royal Astronomical Society (2017). DOI: 10.1093/mnras/stw2926

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Mission
    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
    Keck UCal

    Institute of Astrophysics and Space Sciences

    Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

     
    • RIcardo Reis 5:49 am on March 31, 2017 Permalink | Reply

      This research was NOT made by Instituto de Astrofisica de Canarias in Spain, but by Instituto de Astrofísica e Ciências do Espaço in Portugal.
      In fact, if you check the paper (https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stw2926), this research has no one from IAC.

      Like

    • richardmitnick 7:47 am on March 31, 2017 Permalink | Reply

      Thank you very much for the correction. I did not read far enough and got myself stuck in the acronym. I believe that I have sufficiently corrected the post. Please look at it again and let me know what you think.

      Thanks again for your help.

      Like

  • richardmitnick 5:43 pm on August 17, 2016 Permalink | Reply
    Tags: , , Radio galaxies   

    From AAS NOVA: “History of a Rare Radio Galaxy Revealed by Its Jets” 

    AASNOVA

    American Astronomical Society

    17 August 2016
    Susanna Kohler

    1
    Artist’s illustration of a radio galaxy with two symmetric jets of highly energetic particles — launched by the supermassive black hole at the galaxy’s center — which inflate giant lobes of radio emission at either end. A recent study has discovered a galaxy that exhibits not just one pair of lobes like the example above, but three pairs. [Adapted from ESA/C. Carreau/ATG medialab]

    Most radio galaxies exhibit a single pair of radio lobes marking the endpoints of their jets. But the unusual three pairs radio lobes of a recently observed radio galaxy may reveal information about this galaxy’s past.

    2
    A 610 MHz image displaying J1216+0709’s three sets of radio lobes: inner, middle, and outer. These were likely caused by three different episodes of AGN activity. [Adapted from Singh et al. 2016]

    Core-Jet-Lobe

    Radio galaxies, a subclass of active galactic nuclei (AGN), typically exhibit what’s known as a “core-jet-lobe” structure. A supermassive black hole accreting matter at the galaxy’s core flings material out at the poles, forming two symmetric jets of highly energetic particles. These jets can travel vast distances before spreading out into giant, radio-emitting lobes.

    Thousands of these double-lobed radio galaxies have been observed, but a few dozen are unique cases that exhibit two pairs of lobes. These different pairs likely formed during two different phases of AGN activity: the jets were activated long enough to inflate the first lobes, then turned off, and then turned back on again and inflated the second lobes.

    Now, the third-ever case of a triple set of lobes has been discovered: the radio galaxy J1216+0709, located roughly 2 billion light-years away.

    2
    A spectral image map between the 325 and 620 MHz GMRT observations. There’s no signature of compact hot-spot structures in the outer lobes, indicating that the supply of jet material to the outer lobes stopped long ago. [Adapted from Singh et al. 2016]

    Clues from Morphology

    J1216+0709 is an early-type elliptical galaxy hosting a supermassive black hole of several billion solar masses at its core. The galaxy’s unusual radio structure was discovered by a team of scientists led by Veeresh Singh (Physical Research Laboratory in Ahmedabad, India), using India’s Giant Metrewave Radio Telescope (GMRT).

    The radio lobes detected in J1216+0709 consist of an inner pair ~310 thousand light-years across, a nearly coaxial middle pair ~770 thousand light-years across, and an outer pair ~2.7 million light-years across. Singh and collaborators note several important observations about the galaxy’s morphology:

    The outer pair of lobes is much fainter than the inner pairs, and it doesn’t contain any hot spots. This makes sense if the outer lobes are the oldest, as expected, and are no longer being actively fed.
    The inner pairs of lobes are both brighter and longer on their eastern sides than on their western sides, suggesting that the jets are intrinsically asymmetric.
    The outer pair of lobes is bent with respect to the inner jets. This could mean that the material is interacting with the surrounding environment, which may have a large-scale density gradient. Alternatively, it could mean that the galaxy moved in between the two cycles of AGN activity.

    Interaction as a Trigger

    What could be triggering the bursts of jet activity? Singh and collaborators reference J1216+0709 against a catalog of galaxies and clusters, and find that the host galaxy is part of a small group of three galaxies.

    Though there’s no visible disturbance in the host galaxy’s morphology, minor interactions with two nearby dwarf galaxies could be triggering the sporadic AGN activity. In the future, more sensitive optical data may be able to confirm this model.

    Citation

    Veeresh Singh et al 2016 ApJ 826 132. doi:10.3847/0004-637X/826/2/132

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 3:44 pm on February 24, 2016 Permalink | Reply
    Tags: , , , , , Radio galaxies   

    From CfA: “Discovering Distant Radio Galaxies via Gravitational Lensing” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 19, 2016
    No writer credit found

    radio galaxies gravitationally lensed by a very large foreground galaxy cluster Hubble
    A Hubble Space Telescope image of distant, bright radio galaxies being gravitationally lensed by a very large foreground galaxy cluster. The red contours show the radio emission of these galaxies, which date from an epoch about three billion years after the big bang. A team of X-ray astronomers used these lensed radio galaxies to identify and study distant galaxies with active supermassive black hole nuclei. NASA HST, and van Weeren et al.
    .

    A lensing cluster is a gravitationally bound collection of galaxies, hundreds or even thousands, whose mass acts as a gravitational lens to collect and reimage the light of more distant objects. These lensing clusters make excellent targets for astronomical research into the early universe because they magnify the faint radiation from more distant galaxies seen behind them, making these remote objects accessible to our telescopes. Most searches in “lensed galaxies” have so far been done at optical, near infrared or submillimeter wavelengths, and the latter have been successful at identifying luminous dusty galaxies from earlier cosmic epochs that are powered by bursts of star formation that were more common back then.

    X-ray astronomers study the powerful jets and high energy particles around supermassive black holes at the nuclei of active [galactic nucelii] (AGN). X-rays are also seen in galaxies dominated by star formation, but they are much dimmer than those seen from AGN and so are difficult to study when these galaxies are at cosmological distances. Even finding distant examples in lensing searches can be challenging, and when the star formation activity is modest they are not even expected to show up in infrared lensing searches. But in galactic nuclei, the same fast-moving particles that emit at X-ray wavelengths also emit at radio wavelengths. A search for lensed radio emission, therefore, is a way to study distant, faint galaxies and their black hole nuclei.

    CfA astronomers Reinout van Weeren, G. Ogrean, Christine Jones, Bill Forman, Felipe Andrade-Santos, E. Bulbul, Lawrence David, Ralph Kraft, Steve Murray (deceased), Paul Nulsen, Scott Randall, and Alexey Vikhlinin and their colleagues have completed a radio survey of the large cluster known as MACS J0717.5+3745.

    Radio galaxy MACS J0717.5+3745 Hubble Chandra composite
    This composite image shows the massive galaxy cluster MACS J0717.5+3745 (MACS J0717, for short), where four separate galaxy clusters have been involved in a collision — the first time such a phenomenon has been documented. Hot gas is shown in an image from NASA’s Chandra X-ray Observatory, and galaxies are shown in an optical image from the NASA/ESA Hubble Space Telescope. The hot gas is colour-coded to show temperature, where the coolest gas is reddish purple, the hottest gas is blue, and the temperatures in between are purple.
    The repeated collisions in MACS J0717 are caused by a 13-million-light-year-long stream of galaxies, gas, and dark matter — known as a filament — pouring into a region already full of matter. A collision between the gas in two or more clusters causes the hot gas to slow down. However, the massive and compact galaxies do not slow down as much as the gas does, and so move ahead of it. Therefore, the speed and direction of each cluster’s motion — perpendicular to the line of sight — can be estimated by studying the offset between the average position of the galaxies and the peak in the hot gas.
    MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen. Other well-known clusters, like the Bullet Cluster and MACS J0025.4-1222, involve the collision of only two galaxy clusters and show much simpler geometry.

    NASA Chandra Telescope
    NASA/Chandra

    NASA Hubble Telescope
    NASA/ESA Hubble

    This group of galaxies, one of the largest and most complex known with the equivalent of over ten thousand Milky Way-sized galaxies, is located about five billion light-years away.

    The astronomers used the Jansky Very Large Array [VLA] to hunt for lensed radio sources in this cluster, and detected fifty-one compact galaxies — seven whose light seems to be magnified by the cluster by more than factor of two and as much as a factor of nine.

    NRAO VLA
    NRAO/Karl V Jansky VLA

    The scientists infer from the radio fluxes that most of these seven are forming new stars at a modest rate, ten to fifty per year, and date from an epoch about three billion years after the big bang. Two are also detected in X-rays by the Chandra X-ray Observatory, and so host AGN, each one radiating about as much light in X-rays as a billion Suns. The two AGN are interesting in themselves, but finding them both in this one region suggests that, like bright star forming galaxies, these AGN were more common back then too.
    Reference(s):

    The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACSJ0717.5+3745 with the JVLA and Chandra, R. J. van Weeren, G. A. Ogrean, C. Jones, W. R. Forman, F. Andrade-Santos, A. Bonafede, M. Brüggen, E. Bulbul, T. E. Clarke, E. Churazov, L. David, W. A. Dawson, M. Donahue, A. Goulding, R. P. Kraft, B. Mason, J. Merten, T. Mroczkowski, S. S. Murray, P. E. J. Nulsen, P. Rosati, E. Roediger, S. W. Randall, J. Sayers, K. Umetsu, A. Vikhlinin, and A. Zitrin, ApJ 817, 98, 2016.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 5:56 pm on January 11, 2016 Permalink | Reply
    Tags: , , , Radio galaxies,   

    From U Oxford: “Exploring spiral-host radio galaxies” 

    U Oxford bloc

    Oxford University

    OUP blog bloc

    Temp 1
    Hercules. A radio galaxy hosted in a massive elliptical galaxy. Radio emission, overplotted on the optical image, is shown in pink highlighting large jet-lobe structure. A Milky Way-sized spiral galaxy is marked by white ellipse. Image adapted from a Hubble Heritage Release. Credit: NASA, ESA, S. Baum and C. O’Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA).

    January 9th 2016
    Veeresh Singh

    Few know exactly what radio galaxies are, much less what factors influence their formation. Even so, new discoveries have brought these astronomical structures into the public eye, and researchers continue to investigate the mysterious conditions of their existence. Below, Veeresh Singh addresses the substance and implications of such discoveries, further elaborating on his research paper, Discovery of rare double-lobe radio galaxies hosted in spiral galaxies, recently published in Monthly Notices of Royal Astronomical Society.

    What are radio galaxies?

    A galaxy is a gigantic system possessing billions of stars, vast amounts of gas, dust, and dark matter held together by gravitational attraction. The typical size of galaxies can be anywhere from a few tens-of-thousands to a few hundreds-of-thousands of light-years. Our own solar system is part of a galaxy named the “Milky Way.” Observations made from telescopes have shown that our universe is full of billions of galaxies that are of different shapes (e.g., spiral, spheroidal, elliptical and irregular).

    Studies on the motion of stars, gas, and dust close to the core of galaxies reveal that almost all galaxies host Super Massive Black Holes(SMBHs), which are millions to billions of times the mass of our Sun in their centres. In simple words, black holes are gravitationally collapsed systems in which gravity is so strong that even light cannot escape from the surface of their sphere of influence. Whenever matter is available in the vicinity of SMBHs, they accrete matter via gravitational pull and also eject a fraction of accreted matter—through outflowing bipolar collimated jets formed via magneto-hydro-dynamical processes.

    Galaxies having accreting SMBH are called “active galaxies.” Some of these active galaxies exhibit radio-emitting overflowing jets extending well beyond the size of host galaxies’ stellar distribution. These active galaxies are called “radio galaxies.” As the name itself suggests, radio galaxies are powerful emitters of radio emissions and show radio morphology that consists of a core producing a pair of bipolar collimated jets terminating in two lobes. The radio core coincides with the centre of the host galaxy seen in optical light but the jet-lobe extends well-beyond the host galaxy and entrenches into the empty space between galaxies, i.e. “intergalactic region.” Radio galaxies are one of the largest structures in the Universe and the total end-to-end radio size can range from thousands to millions of light years.

    What is the shape of hosts of radio galaxies?

    Traditionally, radio galaxies are found to be hosted in massive, gas-poor elliptical galaxies characterised by feeble star formation rates. It is believed that the relativistic jets emanating from the accreting SMBHs at their centres can easily plough through the rarer InterStellar Medium (ISM) of elliptical galaxies and reach scales of up to millions of light years.

    How common are spiral-host radio galaxies?

    Unlike conventional radio galaxies, which are almost always found in elliptical galaxies, we have discovered four radio galaxies (named in astronomical parlance as J0836+0532, J1159+5820, J1352+3126, and J1649+2635) that are found to be hosted in spiral galaxies. These extremely rare and enigmatic galaxies were found in a systematic search that combined a whopping 187,000 optical images of spiral galaxies from the Sloan Digital Sky Survey (SDSS) DR7 with the radio-emitting sources from two radio-surveys viz. ‘Faint Images of the Radio Sky at Twenty-cm (FIRST)’ and ‘NRAO VLA Sky Survey (NVSS)’ both carried out with the Very Large Array (VLA) radio telescope in the United States.

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    NRAO VLA
    NRAO/VLA

    This is the first attempt to carry out an extensive systematic search to find spiral-host radio galaxies using largest existing sky surveys. Before this work, only four examples of spiral-host radio galaxies were known and three of these were discovered serendipitously.

    What causes spiral galaxies to become radio-loud?

    Understanding the formation of these newly discovered spiral-host radio galaxies is a challenge in the present theoretical model. Using current available data on these sources it is speculated that the formation of spiral-host double-lobe radio galaxies can be attributed to more than one factor, such as the occurrence of strong interactions or mergers with other galaxies, and the presence of an unusually massive SMBH, while keeping the spiral structures intact. Notably, all these galaxies contain an SMBH at their centre with a mass of approximately a billion times that of the Sun.

    2
    J083+0532, a spiral galaxy with million-light-years large radio emitting jet-lobe structure. Upper panel shows contours of radio emission overplotted on the optical image from Sloane Digital Sky Survey (SDSS). Lower left panel represents the false colour radio image while lower right panel shows SDSS optical image. Image used with permission.

    Since only one among four was found in a cluster environment, it implies that the large scale environment is not the prime reason for triggering radio emission. Mergers or interactions could be more likely. In fact, two galaxies—J1159+5820 and J1352+3126—in this study show evidence of mergers. However, another two galaxies—J0836+0532 and J1649+2635—are face-on spirals and do not show any detectable signature of disturbance caused by a recent merger with another galaxy.

    How are galaxies currently being studied?

    In order to attain a better understanding of the formation of these galaxies, the research team is observing these galaxies at different frequencies. The team has already acquired low frequency radio observations with the Giant Metrewave Radio Telescope (GMRT) in India.

    Giant Metrewave Radio Telescope
    GMRT

    The multi-frequency radio observations will enable the study of the radio structures at different spatial scales and also in estimating the time elapsed since the radio emitting jets were ejected from the centre of each galaxy.

    What does the discovery of spiral-host radio galaxies mean to upcoming surveys?

    The discovery of these spiral-host radio galaxies can be considered as a test bed to find rare populations of spiral-host double-lobe radio galaxies in the distant universe using more sensitive surveys from upcoming facilities such as the Large Synoptic Survey Telescope (LSST) and the Square Kilometre Array (SKA).

    LSST Exterior
    LSST Interior
    LSST Camera
    LSST, the building which will house it, and the camera being built at SLAC

    SKA ASKAP telescope

    SKA Murchison Widefield Array
    From SKA, ASKAP and part of the Murchison Wide Field Array

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Oxford campus

    Oxford is a collegiate university, consisting of the central University and colleges. The central University is composed of academic departments and research centres, administrative departments, libraries and museums. The 38 colleges are self-governing and financially independent institutions, which are related to the central University in a federal system. There are also six permanent private halls, which were founded by different Christian denominations and which still retain their Christian character.

    The different roles of the colleges and the University have evolved over time.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: