CAS-CONICYT Postdoc Claudio Ricci Finds that Merging Galaxies Have Enshrouded Black Holes

This illustration compares growing supermassive black holes in two different kinds of galaxies. A growing supermassive black hole in a normal galaxy would have a donut-shaped structure of gas and dust around it (left). In a merging galaxy, a sphere of material obscures the black hole (right).

Credits: National Astronomical Observatory of Japan

Black holes get a bad rap in popular culture for swallowing everything in their environments. In reality, stars, gas and dust can orbit black holes for long periods of time, until a major disruption pushes the material in.

A merger of two galaxies is one such disruption. As the galaxies combine and their central black holes approach each other, gas and dust in the vicinity are pushed onto their respective black holes. An enormous amount of high-energy radiation is released as material spirals rapidly toward the hungry black hole, which becomes what astronomers call an active galactic nucleus (AGN).

A study using NASA’s NuSTAR telescope shows that in the late stages of galaxy mergers, so much gas and dust falls toward a black hole that the extremely bright AGN is enshrouded. The combined effect of the gravity of the two galaxies slows the rotational speeds of gas and dust that would otherwise be orbiting freely. This loss of energy makes the material fall onto the black hole.

“The further along the merger is, the more enshrouded the AGN will be,” said Claudio Ricci, lead author of the study published in the Monthly Notices Royal Astronomical Society. “Galaxies that are far along in the merging process are completely covered in a cocoon of gas and dust.”

Ricci and colleagues observed the penetrating high-energy X-ray emission from 52 galaxies. About half of them were in the later stages of merging. Because NuSTAR is very sensitive to detecting the highest-energy X-rays, it was critical in establishing how much light escapes the sphere of gas and dust covering an AGN.

The study was published in the Monthly Notices of the Royal Astronomical Society. Researchers compared NuSTAR observations of the galaxies with data from NASA’s Swift and Chandra and ESA’s XMM-Newton observatories, which look at lower energy components of the X-ray spectrum. If high-energy X-rays are detected from a galaxy, but low-energy X-rays are not, that is a sign that an AGN is heavily obscured.

The study helps confirm the longstanding idea that an AGN’s black hole does most of its eating while enshrouded during the late stages of a merger.

“A supermassive black hole grows rapidly during these mergers,” Ricci said. “The results further our understanding of the mysterious origins of the relationship between a black hole and its host galaxy.”

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

For more information on NuSTAR, visit:

http://www.nasa.gov/nustar

http://www.nustar.caltech.edu

Reproduced from https://www.nasa.gov/feature/jpl/merging-galaxies-have-enshrouded-black-holes

Chinese President Xi Jinping and Chilean President attend the Signing Ceremony of China-Chile Collaborations to develop Astronomical Observatories in Chile

 

On November 22nd, in Santiago, the capital of Chile, at the witness of Chinese President Xi JinPing and Chilean President Michelle Bachelet, Prof. Jun Yan, Director General of National Astronomical Observatories, Chinese Academy of Sciences (NAOC), and Mr. Jorge Tabilo Álvarez, President of the Catholic University of the North (UCN) signed a Memorandum of Understanding (MOU) to jointly develop an Astronomical Observational base in Chile.

 

Due to its outstanding astronomical climate, and the steady support of its government, Chile is a key site for international astronomy research. Over the last few decades, several foreign interests, such as the U.S.A., Japan, and the E.U., have developed observational facilities in the country. The Ventarrones site (VTRS), which belongs to the Catholic University of the North, has been subject to detailed investigation and comparison by the Chinese Academy of Sciences South America Center for Astronomy (CASSACA) and is considered as an excellent site for astronomic observations. The site is located in the famous Atacama Desert, about 1200 KMs north from Santiago, and is at an altitude of 2900 meters.

 

The VTRS site was previously selected as a candidate site for the European Southern Observatory’s (ESO) 39 meter European Extremely Large Telescope (E-ELT, in construction), and its sky quality and conditions have been evaluated and positively confirmed by world-class institutions. In order to promote scientific developments in the field of observational astronomy and related sciences and technology, and to strengthen the collaboration and communication of scientists, engineers, and students between the two countries, NAOC and UCN have agreed to form a bilateral partnership to develop the VTRS site into a world-class scientific research base for observational astronomy. The site is also expected to play an important role in the scientific outreach and education.

 

This event marks the second time these parties have signed a MOU witnessed by both their respective heads of state, the first being the attendance of Chinese Premier Li Keqiang and the Chilean President in the signing ceremony of China-Chile Joint Astronomical Data Center in 2015. The MOU is also a highlight of and a major milestone in CASSACA’s past three years of work, after its foundation in Chile since 2013. Dr. Jun Yan,the Director General of NAOC, specifically pointed out that developing an observational base in Chile is a strategic step that has been carefully considered by the scientific community, based on the long-term plan for China’s development in the field of astronomy. The official signing of the MOU and its gradual implementation will enable China for the first time to have a world-class site overseas by means of joint development. This will be of great significance to the development of astronomical observation and techniques in China, and it will further promote cooperation and communications between China and Chile in the field.

 

The news that NAOC and UCN will collaborate to develop astronomical observatories in Chile has attracted strong interest in the local community and media. The idea of constructing future observatories in this kind of collaborative way is supported by the Chilean government and local astronomers, who are optimistic in regards to the future development of the project. One major media outlet in Santiago prepared a special report on the signing of the agreement, pointing out that this is a milestone in China’s development of astronomical observations in South America. Dr. Cameron, the director of ESO (Chile), commented in a congratulatory letter that this collaborative approach is an “excellent choice” for China. He also expressed willingness to provide assistance for the future development of the VTRS site.


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China Finishes Construction of World’s Largest Radio Telescope [from CAS newsroom]

 

 

FAST one step from completion. (Image by XIN Ling)

After more than five years of construction, the world’s largest single-dish radio telescope is finally getting ready to open its eye. On July 3, 2016, with the installation of the last of its 4,450 reflecting panels – equivalent to the size of 30 soccer fields – the Five-hundred-meter Aperture Spherical radio Telescope (FAST) is counting down to seeing its first light in two to three months’ time.

A bird view of FAST (Image by NAOC)

Compared with the Arecibo telescope, the previous record holder with a diameter of 300 meters, FAST is not only much bigger and more sensitive, but innovative in several ways: It has a much larger sky coverage thanks to its active main reflector, and a light-weight, adjustable feed cabin to move with high precision, etc.

“Once completed, it will lead the world for at least 10 to 20 years,” said YAN Jun, director general of the telescope’s designer, builder and owner – the National Astronomical Observatories of China (NAOC) under CAS. YAN was on the scene to celebrate the completion of FAST’s main construction work on July 3.

Installation of the reflector started in August 2015. In 11 months’ time, 4,273 triangular segments and 177 special-shaped segments were set into a unique cable-net structure consisting of thousands of steel cables, nodes and corresponding driving cables, which are tied to actuators on the ground to realize the transformation from a spherical to a parabolic surface.

FAST under construction (Image by NAOC)

The idea of building such a telescope was first proposed in 1994. After a decade of site surveying, Chinese scientists found a nearly perfect spot for FAST in Dawodang, Kedu Town in southeastern China’s Guizhou Province, which is famous for its karst landforms and mountains that naturally shield against radio frequency interference.

The project was approved by the Chinese government in 2007 and will be completed 5-1/2 years after the project was formally started – exactly in line with projections. When completed, the total cost is estimated to be 1.15 billion yuan ($180 million US dollars).

“FAST will enable Chinese astronomers to jump-start many scientific goals, such as surveying the neutral hydrogen in the Milky Way, detecting faint pulsars, and listening to possible signals from other civilizations,” said NAN Rendong, the general engineer and chief scientist of FAST.

“It’s time for China to have its own big telescope,” NAN said.

In the next couple of months, the FAST team will focus on testing and debugging to make the telescope work, said WANG Qiming, head of the reflector system and general technologist for the project. The official completion date is set for late September, and the telescope’s first data are expected around the same time. (By XIN Ling)

Night view of FAST (Image by NAOC)

CAS Vice President Tieniu Tan Visits Chile

Dr. Tieniu Tan, Vice President of Chinese Academy of Sciences (CAS), visited Chile from May 6th to 8th, 2016, as invited by the Chilean Comisión Nacional de Investigación Científica y Tecnológica (CONICYT), the University of Chile and the Chinese Academy of Sciences South America Center for Astronomy (CASSACA). Dr. Xiaoyu Hong (Director General of Shanghai Astronomical Observatories, CAS), Xiaoou Chen (Commissioner of Science and Technology, Chinese Embassy in Chile), Zhong Wang (Director of CASSACA), Wei Wang (Deputy Director of CASSACA) and Dr. Meng Su (MIT) accompanied his visit.

 

In the morning of May 6th, Dr. Tan met the new CONICYT director Dr. Mario Hummuy and Chilean Senator Dr. Guido Girardi. They discussed potential collaborations between the two countries in astronomy and other aspects of science and technology. Afterwards, Dr. Tan visited the China-Chile Astronomical Data Center (CCADC) and offered his suggestions for its long-term development. CCADC is the first major collaborative project led by CASSACA. Its aim is to enable Chinese and Chilean astronomers to better process astronomical data obtained from large telescopes.

 

In the afternoon, Dr. Tan visited the Department of Astronomy at the University of Chile. There, he expressed gratitude to director Dr. Guido Garay for the department’s help in the development of CASSACA and discussed future plans for the Center. Dr. Tan then visited the CASSACA office and was introduced to its staff and researchers. Dr. Tan applauded the significant achievements of CASSACA during the past three years, and he encouraged the staff in their efforts to build international scientific cooperation, to drive cutting edge astronomical research, and to develop the Center as a platform for China-Chile collaborations in astronomy and other areas of research. In addition, Dr. Tan met the Chinese Ambassador in Chile, Mr. Baorong Li, and the President of the Chilean Academy of Sciences, Madam Maria Teresa Ruiz, and exchanged ideas with them regarding China-Chile collaborations and CASSACA.

 

On May 7th and 8th, Vice President Tan went to northern Chile to visit the Atacama Large Millimeter/sub-millimeter Array (ALMA), which is assembled on a 5,060 meter-high plateau, as well as three telescopes dedicated to Cosmic Microwave Background (CMB) research. These were the Atacama Cosmology Telescope (ACT), the Cosmology Large Angular Scale Surveyor (CLASS), and the POLARBEAR telescopes, all of which are assembled on a 5,200 site nearby. Together, these facilities represent the state-of-the-art science and technology in radio astronomy and are the results of a wide-range of international collaborations. Dr. Tan’s visit is among the first that CAS leaders made to the 5,000+ meter sites in Chile.

 

ALMA is an astronomical interferometer of radio telescopes built collaboratively by several institutions from Europe, the United States and East Asia. It consists of 66 12-meter and 7-meter diameter radio telescopes, observing at millimeter and submillimeter wavelengths, with a resolution of up to 0.01 arcsec. ALMA is expected to be able to provide insights on star birth during the early universe and detailed imaging of local star and planet formation. ALMA is located in the Atacama Desert of Northern Chile, on the Chajnantor plateau. The location is one of the driest sites in the world and very suitable for mm and submm observations. After about 15 years of construction, costing US$1.4 billion, ALMA began full operation in March 2013. The observatory has since attracted close attention from astronomers from all nations and led to various new scientific discoveries.

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CAS Vice President Tieniu Tan Visits Chile

CASSACA Council Meeting held in Beijing

On December 18, 2015the Council Meeting of the Chinese Academy of Sciences South America Center for Astronomy (CASSACA) was held in  National Astronomical Observatories, Chinese Academy of Sciences (NAOC). Prof. Zhongli Ding, Vice President of CAS & Director of the Council, attended the meeting and gave important suggestions and guidance to CASSACA. There are more than 30 attendees coming from CAS administration divisions, the institutes in CAS Observatory system and Universities. 

Prof. Zhong Wang, Director of CASSACA, reported the overall progress and achievements of the Center obtained in 2015. Prof. Jiasheng Huang, Chief Scientist of CASSACA, specially introduced the progress in research and scientific programs in the past. Then the Council gave full affirmation on the achievements and progress by the Center. The Council gave practical guidance and suggestions to the Center’s development and future plans. Two new members were approved to join the Council.  

CASSACA has achieved remarkable results and progress in the past, over its collaborations with Chilean institutions and scientists, on the scientific researches, programs and projects. Especially, the CASSACA set up the China-Chile astronomical data center with cooperation with Universidad Tecnica Federico Santa Maria of Chile and Huawei company of China. Prime Minister Keqiang Li and Chilean President Michelle Bachelet witnessed the signing ceremony of the data center in May 2015. The system run stably and went into the stage of software debugging and commissioning since November 2015. 

CASSACA was set up in 2013 and has been playing an important role on the international collaborations in Astronomy between China and Chile together with other South America countries. 

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COUNCIL MEETING
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GROUP PHOTO