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  • richardmitnick 2:27 pm on November 10, 2020 Permalink | Reply
    Tags: "New extremely variable quasar discovered", , , , , Kyoto University, , SDSS J125809.31+351943.0   

    From Kyoto University via phys.org: “New extremely variable quasar discovered” 

    From Kyoto University



    November 10, 2020
    Tomasz Nowakowski

    Time-series of the photometric data of J1258 in optical and mid-infrared. Credit: Nagoshi et al., 2020.

    By analyzing data from astronomical surveys, Japanese astronomers have detected a new, extremely variable quasi-stellar object (QSO), or quasar. The newly found object, designated SDSS J125809.31+351943.0, brightened in optical band for 4.0 mag over three decades, which means that it was one of the largest quasar brightening events so far recorded. The finding is reported in a paper published November 3 in PASJ.

    Quasars are active galactic nuclei of very high luminosity, emitting electromagnetic radiation observable in radio, infrared, visible, ultraviolet and X-ray wavelengths. They are among the brightest and most distant objects in the known universe, and serve as fundamental tools for numerous studies in astrophysics as well as cosmology. For instance, quasars have been used to investigate the large-scale structure of the universe and the era of reionization. They also improved our understanding of the dynamics of supermassive black holes and the intergalactic medium.

    Some distant quasars exhibit broad emission lines (BELs) that appear or disappear, which is known as a so-called optical “changing-look” phenomenon. Most of these changing-look quasars (CLQ) showcase large optical luminosity variations exceeding 1.0 mag. Besides CLQs, such large luminosity changes have been also observed in hyper-variable quasars (HVQs) and changing-state quasars (CSQs). The classification of HVQs is based on the change of optical brightness, while that of the CSQ is on the change of BELs, optical continuum flux density and mid-infrared luminosities.

    Now, a team of astronomers led by Shumpei Nagoshi of the Kyoto University in Japan reports the finding of a new quasar that exhibits a large amplitude of variability and appears to be a CSQ. The discovery of SDSS J125809.31+351943.0 (or J1258 for short) was based on data from programs including the Survey and All Sky Automated Survey for Super Novae (ASAS-SN), the Sloan Digital Sky Survey (SDSS) and NASA’s Wide-field Infrared Survey Explorer (WISE).

    ASAS-SN Brutus at LCOGT site Hawaii

    LCOGT Las Cumbres Observatory Global Telescope Network, Haleakala Hawaii, USA, Elevation 10,023 ft (3,055 m).

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft).

    Apache Point Observatory, near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft).

    NASA/WISE NEOWISE Telescope.

    “We discovered an extremely variable quasar, SDSS J125809.31+351943.0, brightened for 4.0 mag from 1983 to 2015. We identified this object as a new CSQ on the basis of the significant changes in the mid-infrared luminosity and in the intensity of the broad emission line,” the astronomers wrote in the paper.

    The observational data span the period between 1983 and 2015. It was found that J1258 exhibited a monotonic increase of luminosity for as much as 4 mag over about 30 years. The astronomers noted that this is one of the largest amplitudes of monotonic variations with the longest timescale of any quasar’s variability reported to date.

    Furthermore, the observations revealed significant changes in the mid-infrared luminosity and in the intensity of the broad emission line of J1258. The results also show the weakness of radio emission, which indicates that the variability is not caused by the quasar’s jet. In addition, it was found the flux in mid-infrared changed following the optical band. This supports the assumption that the accretion disk itself changed, rather than the variation of absorption, took place.

    The astronomers therefore concluded that J1258 is a CSQ and also one of the most drastically variable objects so far detected.

    See the full article here.


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    Kyoto University is a national university in Kyoto, Japan. It is the second oldest university in Japan and one of the former Imperial Universities, a Designated National University, and was selected as a Top Type university of the Top Global University Project by the Japanese government. The university is usually ranked among the top two in Japan, top 10 in Asia, and the world’s top thirty institutions of higher education. It is also the birthplace of the well-known Kyoto School.

    Kyoto University has generated 5 prime ministers of Japan to date, and is also famed for producing world-class researchers, including 19 Nobel Prize laureates, 2 Fields medalists, and one Gauss Prize winner. It has the most Nobel laureates of all universities in Asia.

  • richardmitnick 8:20 am on October 2, 2017 Permalink | Reply
    Tags: , , , , , , Kyoto University, , , University of Tübingen, ,   

    From Science: “Sloshing, supersonic gas may have built the baby universe’s biggest black holes” 


    Sep. 28, 2017
    Joshua Sokol

    Supermassive black holes a billion times heavier than the sun are too big to have formed conventionally. NASA Goddard Space Flight Center

    A central mystery surrounds the supermassive black holes that haunt the cores of galaxies: How did they get so big so fast? Now, a new, computer simulation–based study suggests that these giants were formed and fed by massive clouds of gas sloshing around in the aftermath of the big bang.

    “This really is a new pathway,” says Volker Bromm, an astrophysicist at the University of Texas in Austin who was not part of the research team. “But it’s not … the one and only pathway.”

    Astronomers know that, when the universe was just a billion years old, some supermassive black holes were already a billion times heavier than the sun. That’s much too big for them to have been built up through the slow mergers of small black holes formed in the conventional way, from collapsed stars a few dozen times the mass of the sun. Instead, the prevailing idea is that these behemoths had a head start. They could have condensed directly out of seed clouds of hydrogen gas weighing tens of thousands of solar masses, and grown from there by gravitationally swallowing up more gas. But the list of plausible ways for these “direct-collapse” scenarios to happen is short, and each option requires a perfect storm of circumstances.

    For theorists tinkering with computer models, the trouble lies in getting a massive amount of gas to pile up long enough to collapse all at once, into a vortex that feeds a nascent black hole like water down a sink drain. If any parts of the gas cloud cool down or clump up early, they will fragment and coalesce into stars instead. Once formed, radiation from the stars would blow away the rest of the gas cloud.

    Computer models show how supersonic streams of gas coalesce around nuggets of dark matter—forming the seed of a supermassive black hole. Shingo Hirano

    One option, pioneered by Bromm and others, is to bathe a gas cloud in ultraviolet light, perhaps from stars in a next-door galaxy, and keep it warm enough to resist clumping. But having a galaxy close enough to provide that service would be quite the coincidence.

    The new study proposes a different origin. Both the early universe and the current one are composed of familiar matter like hydrogen, plus unseen clumps of dark matter.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington

    Today, these two components move in sync. But very early on, normal matter may have sloshed back and forth at supersonic speeds across a skeleton provided by colder, more sluggish dark matter. In the study, published today in Science, simulations show that where these surges were strong, and crossed the path of heavy clumps of dark matter, the gas resisted premature collapse into stars and instead flowed into the seed of a supermassive black hole. These scenarios would be rare, but would still roughly match the number of supermassive black holes seen today, says Shingo Hirano, an astrophysicist at the University of Texas and lead author of the study.

    Priya Natarajan, an astrophysicist at Yale University, says the new simulation represents important computational progress. But because it would have taken place at a very distant, early moment in the history of the universe, it will be difficult to verify. “I think the mechanism itself in detail is not going to be testable,” she says. “We will never see the gas actually sloshing and falling in.”

    But Bromm is more optimistic, especially if such direct-collapse black hole seeds also formed slightly later in the history of the universe. He, Natarajan, and other astronomers have been looking for these kinds baby black holes, hoping to confirm that they do, indeed, exist and then trying to work out their origins from the downstream consequences.

    In 2016, they found several candidates, which seem to have formed through direct collapse and are now accreting matter from clouds of gas. And earlier this year, astronomers showed that the early, distant universe is missing the glow of x-ray light that would be expected from a multitude of small black holes—another sign favoring the sudden birth of big seeds that go on to be supermassive black holes. Bromm is hopeful that upcoming observations will provide more definite evidence, along with opportunities to evaluate the different origin theories. “We have these predictions, we have the signatures, and then we see what we find,” he says. “So the game is on.”

    See the full article here .

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    STEM Icon

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