A famished black hole masks out a bright galaxy

A famished black hole masks out a bright galaxy
Extrait du Observatoire de Paris centre de recherche et enseignement en astronomie et
astrophysique relevant du Ministère de l'Enseignement supérieur et de la Recherche.
https://www.obspm.fr/a-famished-black-hole-masks.html
A famished black hole masks
out a bright galaxy
Date de mise en ligne : vendredi 16 septembre 2016
Observatoire de Paris centre de recherche et enseignement en astronomie et
astrophysique relevant du Ministère de l'Enseignement supérieur et de la
Recherche.
Copyright © Observatoire de Paris centre de recherche et enseignement en astronomie et astrophysique relevant du Ministère de l'Enseignement
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A famished black hole masks out a bright galaxy
Using ESO's Very Large Telescope, the NASA/ESA consortium's Hubble space telescope,
and NASA's Chandra X-ray telescope, and international team of astronomers which includes
a scientist from the Laboratoire d'étude du rayonnement et de la matière en astrophysique et
atmosphères (Laboratory for the study of radiation of matter in astrophysics and
atmospheres), has finally solved the mystery of the remarkable changes in the behaviour of a
supermassive black hole in the heart of a distant galaxy. Apparently, the black hole has fallen
on hard times and lacks the fuel needed to illuminate its close environment.
Many galaxies possess an extremely bright core due to the presence of a supermassive black hole. Such cores
transform these "active galaxies" into some of the brightest objects in the Universe. Their extreme luminosity is due
to the fall of hot material into the black hole, a process called accretion. This intense radiation varies from active
galaxy to active galaxy, so that the characteristics of the light emitted have led to the classification of these galaxies
into various types+-1.
La galaxie active Markarian 1018. Cette image acquise par l'instrument MUSE qui équipe le Très Grand
Télescope de l'ESO montre la galaxie active Markarian 1018, dont un trou noir supermassif occupe le centre.
Les boucles de faible luminosité qui entourent la galaxie témoignent de sa fusion récente avec une autre
galaxie. © ESO/CARS survey.
Observation has shown that some of these galaxies can undergo spectacular changes over periods of hardly a
decade - a blink on the scale of astronomical time. The active galaxy Markarian 1018, the target of this new study,
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A famished black hole masks out a bright galaxy
has undergone no less than two changes, the second one restoring its original appearance during a period of five
years. For the first time, this entire cycle, which has also been observed in a few other galaxies, has been studied for
the first time in detail.
The discovery of the variable naturre of Markarian 1018 is due to the CARS project, which links ESO with various
other organizations and whose objective is to accumulate information on 40 neighbouring having and active core.
Routine observations of Markarian 1018 carried out with the help of the MUSE (Multi-Unit Spectroscopic Explorer)
instrument on ESO's VLT revelaed this galaxie's strange brightness changes.
The team of scientists exploited this event : their primary priority was to identify the process responsible for the
violent brightness changes of Markarian 1018. Various astrophysical processes could have been responsible for this
event, but the team was able to eliminate the absorption of an ordinary star by the black hole2 and questioned the
posibility of screening by the surrounding gas3. The initial observations have not led to the identification of the
process which is at the heart of the darkening of Markarian 1018.
Le ciel qui entoure la galaxie active Markarian 1018. Sur cette image à grand champ figure le ciel qui entoure
la galaxie active Markarian 1018. Cette image a été constituée à partir de clichés issus du Digitized Sky
Survey 2. La galaxie se situe au centre de l'image et les faibles traces de sa récente fusion figurent sous
l'aspect de queues et de boucles. © ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin
The scientists were able to obtain complementary data, through the the allocation of observing time on ESA/NASA's
Hubble space telescope and on NASA's Chandra X-ray Observatory. This new data obtained with the help of these
instruments, have enabled them to solve the mystery - lacking the accreting material, the black hole becomes
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A famished black hole masks out a bright galaxy
gradually darker.
The processes operating in the centres of active galaxies, such as this one which has led to changes in the
appearance of Markarian 1018, are still the ojbjects of advanced studies.
Localisation de la galaxie Markarian 1018 dans la constellation de la Baleine. Cette carte reproduit la vaste
mais faible constellation de la Baleine (Le Monstre de la Mer). La plupart des étoiles visibles à l'oeil nu y
figurent, et la position de la galaxie active Markarian 1018 est entourée d'un cercle rouge. Cet objet est trop
faiblement lumineux pour pouvoir être facilement observé au moyen de petits télescopes. © ESO/IAU and
Sky & Telescope
The team includes B. Husemann (ESO, Garching, Allemagne), T. Urrutia (Institut Leibniz dédié à l'Astrophysique,
Potsdam, Allemagne), G. R. Tremblay (Centre d'Astronomie et d'Astrophysique de Yale, New Haven, Etats-Unis), M.
Krumpe (Institut Leibniz dédié à l'Astrophysique, Potsdam, Allemagne), J. Dexter (Institut Max Planck dédié à la
Physique Extraterrestre, Garching, Allemagne), V. N. Bennert (Département de Physique, Université d'Etat
Polytechnique de California, Etats-Unis), G. Busch (Institut de Physique, Université de Cologne, Allemagne), F.
Combes (LERMA, Observatoire de Paris, France), S. M. Croom (Institut d'Astronomie de Sydney, Sydney, Australie
& Centre d'Excellence en Astrophysique ARC), T. A. Davis (Ecole de Physique & d'Astronomie, Université de Cardiff,
Royaume-Uni), A. Eckart (Institut de Physique de l'Université de Cologne, Allemagne ; Institut Max Planck dédié à la
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A famished black hole masks out a bright galaxy
Radioastronomie, Bonn, Allemagne), R. E. McElroy (Institut d'Astronomie de Sydney, Sydney, Australie & Centre
d'Excellence en Astrophysique ARC), M. Pérez-Torres (Institut d'Astrophysique d'Andalousie, Grenade, Espagne),
M. Powell (Centre d'Astronomie et d'Astrophysique de Yale, New Haven, Etats-Unis) and J. Scharwächter
(Observatoire Gemini, Centre Opérationnel Nord, Hawaii, Etats-Unis).
Note(s) :
•
•
•
1-The brightest active galaxies are quasars : the brightness of their cores exceeds that of the rest of the galaxy.
Seyfert galaxies constitute another, less bright class. Originally, a method based on the brighness and the
emission spectrum - i.e. the intensity of the radiation emitted at different wavelengths - enabled one to
distinguish between two kinds of Seyfert galaxies - i.e. Type 1and Type 2. Since then extra classifications such
as Type 1.9 have been introduced.
2-A tidal effect of this kind is produced when a star, too close to a supermassive black hole , is stretched by the
intense gravitational field. This leads to an increase in the brightness of the central region, followed by a slow
decline over the years. The brightness variations observed on the surface of Markarian 1018 were not
compatible with such an event.
3-The darkening produced by gas can affect the measurement of the brigthness of an active galaxy as well as
its spectrum - and so its classification. In effect, the gas on the line of sight acts somewhat like a fog darkening
the headlamps of a car.
Source(s) :
This work has resulted in two articles entitled "Mrk 1018 returns to the shadows after 30 years as a Seyfert 1", and
"What is causing Mrk 1018's return to the shadows after 30 years ?", to be published in one and the same journal :
Astronomy & Astrophysics.
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