Author: cassac_wpadmin

Celebrating Chinese New Year 2024: A Fusion of Traditional Culture and Modern Astronomy in Santiago

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As the Chinese New Year of the Dragon approaches in 2024, the Chinese Academy of Sciences South American Center for Astronomy (CASSACA) and the Department of Astronomy of the University of Chile (DAS, UCh) worked together to celebrate it and promote Chinese culture.

On January 26, this event was held in Santiago, Chile. Ms. Chao Zhu, from the Science and Technology Section of the Chinese Embassy in Chile; Ms. Hongjuan Gu, Chinese Director of the Confucius Institute at the Catholic University of Chile; Representatives of the Confucius Institute at the University of Santo Tomas; Prof. Francisco Martínez Concha, Dean of the Faculty of Physical and Mathematical Sciences at the University of Chile, and the Vice Dean, Prof. Marcela Munizaga; Dr. Bruno Días, President of the Astronomical Society of Chile; Prof. Guido Garay, Director of the Center for Excellence in Astrophysics and Associated Technologies (CATA); Representative of La Cisterna Municipality, and representatives of local Chinese enterprises were invited to the event. Members of Department of Astronomy of UCh, together with the CASSACA team and their families, congregated to celebrate the Chinese New Year, with a total of more than 170 participants.

The cultural experience area, highlighted by its Chinese calligraphy demonstrations and tea ceremony, garnered high praise. The lunch with authentic Chinese dishes, received an especially warm welcome, creating long lines of attendees eager to taste it. Additionally, the harmonious performances of the guzheng and erhu, along with the elegant fan dance, the mysterious face-changing, and the vigorous sword dance, received continuous applause from the audience, raising the festive atmosphere of the event to a climax and perfectly showcasing the rich flavor of the Chinese New Year. In this context, as a highlight of the event, the exhibition of Ancient Chinese Astronomy and Modern Astronomical Achievements showcased the glorious history and modern achievements of Chinese astronomy, attracting the attention of many guests, while a solar observation telescope specially set up by the Department of Astronomy of UCh also became the focus of attention of many attendees.

This celebration not only had a warm and joyful atmosphere on-site, fully showcasing the unique charm of traditional Chinese culture, but it also successfully merged traditional cultural celebrations with the exploration of modern astronomical science. As a significant bridge in the cooperation between China and Chile, CASSACA will continue to play its role as a platform, helping to boost cooperation and exchanges between both countries across multiple fields, together writing a new chapter of friendship

This event was funded by the National Astronomical Observatories of the Chinese Academy of Sciences and assisted by the Department of Astronomy of the University of Chile.

Researchers Discover Cosmic Dust Storms from a Type Ia supernova 

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Cosmic dust—like dust on Earth—comprises groupings of molecules that have condensed and stuck together in a grain. But the exact nature of dust creation in the universe has long been a mystery. Now, however, an international team of astronomers from China, the United States, Chile, the United Kingdom, Spain, etc., has made a significant discovery by identifying a previously unknown source of dust in the universe: a Type Ia supernova interacting with gas from its surroundings. 

The study was published in Nature Astronomy on Feb. 9, and was led by Prof. WANG Lingzhi from the South America Center for Astronomy of the Chinese Academy of Sciences. 

Supernovae have been known to play a role in dust formation, and to date, dust formation has only been seen in core-collapse supernovae—the explosion of massive stars. Since core-collapse supernovae do not occur in elliptical galaxies, the nature of dust creation in such galaxies has remained elusive. These galaxies are not organized into a spiral pattern like our Milky Way but are giant swarms of stars. This study shows that thermonuclear Type Ia supernovae, the explosion of white dwarf stars in binary systems with another star, may account for a significant amount of dust in these galaxies. 

The researchers monitored a supernova, SN 2018evt, for over three years using space-based facilities like NASA’s Spitzer Space Telescope and NEOWISE missions, ground-based facilities like the Las Cumbres Observatory’s global network of telescopes, and other facilities in China, South America, and Australia. They found that the supernova was running into material previously cast off by one or both stars in the binary system before the white dwarf star exploded, and the supernova sent a shock wave into this pre-existing gas. 

During more than a thousand days of monitoring the supernova, the researchers noticed that its light began to dim precipitously in the optical wavelengths that our eyes can see and then started glowing brighter in infrared light. This was a telltale sign that dust was being created in the circumstellar gas after it cooled following the supernova shock wave passing through it.

“The origins of cosmic dust have long been a mystery. This study marks the first detection of a significant and rapid dust formation process in the thermonuclear supernova interacting with circumstellar gas,” said Prof. WANG, first author as well as the corresponding author of the study. 

The study estimated that a large amount of dust must have been created by this one supernova event—an amount equal to more than 1% of the Sun’s mass. As the supernova cools, the amount of dust created should increase, perhaps tenfold. While these dust factories are not as numerous or efficient as core-collapse supernovae, there may be enough of these thermonuclear supernovae interacting with their surroundings to be a significant or even dominant source of dust in elliptical galaxies. 

“This study offers insights into the contribution of thermonuclear supernovae to cosmic dust, and more such events may be expected to be found in the era of the James Webb Space Telescope (JWST),” said Prof. WANG Lifan from Texas A&M University, a co-first author of the study. The Webb telescope sees infrared light that is perfect for the detection of dust. 

“The creation of dust is just gas getting cold enough to condense,” said Prof. Andy Howell from Las Cumbres Observatory and the University of California Santa Barbara. Howell is the Principal Investigator of the Global Supernova Project whose data was used in the study. “One day that dust will condense into planetesimals and, ultimately, planets. This is creation starting anew in the wake of stellar death. It is exciting to understand another link in the circle of life and death in the universe.”

Fig. 1, Schematic sketches of SN 2018evt at the different phases a, b, and c. The artwork at the top right presents the dust formation process.  

This paper can be accessed at https://www.nature.com/articles/s41550-024-02197-9

Fig. 2: Temporal evolution of the mass of the newly-formed dust in SNIa-CSM 2018evt with different compositions, together with the dust masses estimated for core-collapse supernovae.  The black line presents the power law fit to the mass of the newly formed dust of SN 2018evt for 0.3 um graphite grains.

The 6th China-Chile Bilateral Conference for Astronomy Held in Chile

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From November 6th to 10th, the 6th China-Chile Bilateral Conference for Astronomy was held in Puerto Varas, Chile. Over 80 experts, young scholars, and students from more than 30 astronomy research institutions, including the Chinese Academy of Sciences, various Chinese universities, and Chilean astronomy institutions, participated in the conference. They engaged in in-depth discussions on research achievements, the latest developments in China-Chile cooperation, and future collaboration opportunities. This conference was jointly organized by the National Astronomical Observatories of the Chinese Academy of Sciences (CAS, NAOC)/Chinese Academy of Sciences South America Center for Astronomy (CASSACA) and the Chilean Astronomical Society (SOCHIAS). The conference was co-chaired by Prof. Jiasheng Huang from NAOC and Prof. Diego Mardones from the University of Chile.

Gongbo Zhao, Deputy Director of NAOC and Director of CASSACA, and Bruno Días, President of SOCHIAS, delivered opening speeches and welcomed the conference attendees. The conference covered the latest research results in various research areas, including solar system objects, protoplanetary disks, star formation, interstellar medium and astrochemistry, extrasolar planets, stars and star clusters, galaxies, active galactic nuclei, and cosmology, as well as theoretical astrophysics, numerical simulations, big data astronomy, astronomical instruments and equipment, and observatory construction. The conference specially invited astronomers to present the astronomical scientific research achievements and the construction of astronomical observatories and equipment in both China and Chile under the cooperation between the two countries. The invitees included professors Licai Deng, Zhaohui Shang, and Jianrong Shi, from NAOC; professor Zhenya Zheng, from the Shanghai Astronomical Observatory, CAS; professor Ezequiel Treister, from the Pontifical Catholic University of Chile; Dr. Daniela Estefanía Olave Rojas, from the University of Talca; Dr. Richard Lane, from Bernardo O’Higgins University; Dr. Denise Riquelme, from La Serena University; and professor Bin Yang from Diego Portales University. Professor Guido Garay from the University of Chile opened the meeting by reviewing the scientific achievements and excellent talents cultivated in the past ten years of astronomical cooperation between China and Chile. Professor Junfeng Wang from Xiamen University provided a summary of the conference and offered a vision for future China-Chile astronomy cooperation.

This bilateral meeting serves to promote the exchange of astronomy between China and Chile, deepen mutual understanding and trust, expand the influence of Chinese astronomy in Chile, and lay the foundation for more effective China-Chile cooperation in the future. During the conference, astronomers from both China and Chile actively explored common ground for collaboration, fostering in-depth discussions and seeking new points of collaboration. This sets the stage for the rational and efficient utilization of research resources from both sides, focused on key research directions, and the preparation for the early production of significant scientific results in the future.

Researchers Make Significant Progress in Characterizing Exoplanet Atmospheres Using 4-meter Ground-based Telescope

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Recent Progress: Researchers Characterize Exoplanet Atmospheres Using a 4-meter Ground-based Telescope and Achieve Significant Advancements

In recent times, researchers from the National Astronomical Observatory utilized a 4-meter aperture ground-based telescope located in Chile to obtain optical wavelength transmission spectra of two hot Jupiters, namely WASP-69b and WASP-121b. Through model analysis, they were able to provide important constraints on the atmospheric properties of these planets. The research findings were published in the Monthly Notices of the Royal Astronomical Society and Astronomy and Astrophysics Research, respectively.

Hot Jupiters are a type of extreme exoplanets that orbit very close to their host stars, with orbital periods generally less than 10 days. Due to long-term and intense stellar radiation, the dayside temperature of these planets typically exceeds 1000K. As a result, their atmospheres are relatively inflated, exhibiting strong spectral signals, making them one of the most important targets for atmospheric studies. Transmission spectra are crucial data used to investigate exoplanet atmospheres. They represent the difference between the spectra during planetary transits and the out-of-transit spectra, carrying information about the temperature structure and chemical composition of the planetary atmospheres. Therefore, transmission spectra can be utilized to characterize the atmospheric properties of these planets.

WASP-69b has a radius of 1.057±0.047 RJup, a mass of 0.260±0.017 MJup, and an orbital period of approximately 3.868 days. In the transmission spectrum, the researchers, including authors Ouyang Qinglin and Wang Wei, observed a slope caused by Rayleigh scattering, inferring that the atmosphere of this planet is primarily composed of hydrogen. Additionally, the transmission spectrum of WASP-69b exhibits significant oscillation signals in the range of 700-900 nm. Combining atmospheric models, the authors suggest that this may be attributed to titanium oxide absorption. Titanium oxide is commonly considered as the main component responsible for generating temperature inversions in hot Jupiter atmospheres. However, its presence has previously only been detected in the atmospheres of ultra-hot Jupiters (Teq > 2000K), as maintaining a gaseous state for titanium oxide requires sufficiently high temperatures (> 1500K). Thus, this is the first evidence of titanium oxide’s existence in a classical hot Jupiter.

Figure 1: Transmission spectrum of WASP-69b and the corresponding best-fit inversion models. The blue and red lines represent the best-fit inversion models for optical transmission spectrum and combined optical + near-infrared transmission spectrum, respectively. The lower panels show the posterior distributions of the parameters for the two inversion models. Both inversion models exhibit relatively high metallicity.

WASP-121b has a radius of 1.865±0.065 RJup, a mass of 1.183±0.064 MJup, and an orbital period of approximately 1.275 days. The authors found that the transmission spectrum they obtained differs from previous spectra, and there are also significant differences among the spectra obtained by different researchers. Through literature research and reanalysis of previous data, they believe that these differences are likely to be real and unlikely to be attributed to data processing procedures or stellar activity. In other words, the atmospheric composition of this planet may vary over time. Inversion analysis reveals the presence of absorption signals from titanium oxide and vanadium oxide in the atmosphere of WASP-121b. However, the abundances of these components are inconsistent with previous results, further supporting the possibility of temporal variations in the atmosphere of this planet.

Figure 2: Similar to Figure 1, the transmission spectrum of WASP-121b and the corresponding best-fit inversion models are shown. The lower panels display clear posterior distributions of the inversion parameters, depicting the posterior distributions of titanium oxide and vanadium oxide abundances, corresponding to the absorption of these components in the atmosphere.

Both studies represent the first observational research on exoplanet atmospheres using the SOAR telescope. The SOAR telescope, whose full name is Southern Astrophysical Research Telescope, is operated jointly by astronomical institutions from Brazil, Chile, and the United States. The relevant observational data were obtained through the application of the lead author, Wang Wei, during their tenure at the South American Astronomical Observatory of the Chinese Academy of Sciences. The authors of the studies point out that, compared to the current mainstream large-aperture ground-based telescopes and space telescopes, 4-meter telescopes such as SOAR have slightly lower precision. However, they can still provide important constraints on the atmospheric properties of exoplanets. Therefore, 4-meter ground-based telescopes like SOAR can be a cost-effective yet reliable option for studying exoplanet atmospheres, facilitating future research on a larger sample of planetary atmospheres.

Figure 3: The SOAR telescope located in Chile, with an aperture of 4.1 meters.

Paper 1 link: https://academic.oup.com/mnras/article/521/4/5860/7091929

Paper 2 link: https://doi.org/10.1088/1674-4527/accbb2

Call for the 2022 China-Chile Joint Research Fund

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Based on the principles established in a 2013 Memorandum of Understanding (MoU) between the Chinese Academy of Sciences (CAS) and the National Commission of Scientific and Technological Research of the Republic of Chile (CONICYT), and the more specific guidelines described in a recent (2015) Agreement between the National Astronomical Observatories of China (NAOC), the Chinese Astronomical Society, the Chilean Astronomical Society (SOCHIAS) and CONICYT (pdf), we are now inviting research proposals that involve China-Chile collaboration in astronomical research, to promote astronomical research collaborations between China and Chile, to advance astronomy in both countries.

These funds are for research projects based on a collaboration between astronomers from China and Chile, and the subject can be in areas such as astronomical research, observations, instrumental development, theory, etc. 

The duration of each project should be two years at maximum, and can request up to 75,000 USD/year. We are aiming to support 3 or 4 projects in this call.


The deadline for applications is now extended to May,31st 2022. Inquiries can be sent to Dr. Jiasheng Huang (Chief Scientist of CASSACA; jhuang#@#nao.cas.cn), or Dr. Lei Zhu (Deputy Director of CASSACA; lzhu#@#nao.cas.cn).

For more details, please read the attached announcement (pdf).

An IFU View of the Active Galactic Nuclei in MaNGA Galaxy Pairs

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The role of active galactic nuclei (AGNs) during galaxy interactions and how they influence the star formation in the system are still under debate. Recently, a research team led by the Chinese Academy of Sciences South America Center for Astronomy (CASSACA) used the integral field unit (IFU) data to study the star-formation distributions of a paired active galactic nuclei (AGN) sample. They found that AGNs are likely follow an inside-out quenching and the merger impact on the star formation in AGNs is less prominent than in star-forming galaxies (SFGs). 


Upper panel: An example of AGN identification using IFU data.
Lower left: Similar distributions of paired AGNs and isolated AGNs in the SFR-Mass diagram.
Lower right: Interaction show different impact on the resolved properties of AGNs and SFGs.

This pair sample of 1156 IFU-covered galaxies were selected by the velocity offset, projected separation, and morphology from SDSS IV-MaNGA survey, and is further classified into four cases along the merger sequence based on morphological signatures. A total of 61 (5.5%) AGNs in pairs were identified based on the emission-line diagnostics. No evolution of the AGN fraction was found, either along the merger sequence or compared to isolated galaxies (5.0%). There was a higher fraction of passive galaxies in galaxy pairs, especially in the pre-merging cases, which was related to a denser environment. The isolated AGN and AGNs in pairs showed similar distributions in their global stellar mass, star-formation rate (SFR), and central [O iii] surface brightness. AGNs in pairs showed radial profiles of increasing specific SFR and declining Dn4000 from center to outskirts, and no significant difference from the isolated AGNs. This was clearly different from SFGs in this pair sample, which showed enhanced central star formation, as reported before. AGNs in pairs had lower Balmer decrements at outer regions, possibly indicating less dust attenuation.

The research paper is recently published in The Astrophysical Journal (https://doi.org/10.3847/1538-4357/ac2901). CASSACA student Gaoxiang Jin and Prof. Y. Sophia Dai are the first author and the corresponding author, respectively.

2021 CASSACA & CBJLSW Joint Council Meeting Held in Bejing

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On October 20, 2021, the Joint Council Meeting of the Chinese Academy of Sciences South America Center for Astronomy (CASSACA) and the China-Brazil Joint Laboratory for Space Weather of CAS (hereinafter referred to as CBJLSW) was held at the headquarter of National Astronomical Observatories, Chinese Academy of Sciences (NAOC). Prof. Zhang Yaping, Vice President of the Chinese Academy of Sciences and the Chairman of CASSACA & CBJLSW Council, attended the meeting. The representatives of the Council members of both centers attended the meeting as well.

The Council reviewed and approved the annual work reports, funding implementations of the year 2021, as well as the work plans and budget arrangements for the next year of both oversea centers. In the meeting, the Council discussed extensively and put forward suggestions on several issues, including the platform operation, scientific research deployment, resource allocation, and international cooperation in the frontier areas such as astronomy, space science, climate and remote sensing observation.

In his concluding speech, Zhang Yaping fully acknowledged the efforts and achievements made by CASSACA and CBJLSW under the current difficult circumstances of COVID-19 pandemic. He pointed out that new requirements should be placed for the oversea centers in the new stage.  “The oversea centers should further refine their work priorities, make full use of the unique advantages of the oversea platform, promote multilateral collaboration, and develop a more open and dynamic system”, said by Zhang Yaping. He also encouraged the scientists to propose major scientific ideas and plans in order to gain more and more influential scientific achievements based on the overseas centers. 

CASSACA and CBJLSW were two oversea centers of Chinese Academy of Sciences. They were set up in October 2013 in Chile and in August 2014 in Brazil separately. They have been playing an important role in the international collaborations in the areas of astronomy and space weather between China and South America countries. 

The First FAST detection of neutral hydrogen emission from extragalactic galaxies

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The Five-hundred-meter Aperture Spherical Radio Telescope (FAST) is the largest telescope with the highest sensitivity in the world. Extragalactic neutral hydrogen detection is one of important scientific goals of FAST.

Recently, an international research team led by Dr. Cheng Cheng from Chinese Academy of Sciences South America Center for Astronomy (CASSACA), successfully detected the neutral hydrogen line emission from three local galaxies using the FAST 19-beam receiver with only five minutes of exposure. The research paper is recently published in Astronomy & Astrophysics Letter. This is the first publication on FAST observation of extragalactic neutral hydrogen.

Fig. 1. The optical color images of the four galaxies for FAST observation. The red contours are the previous CO observation by ALMA. The white spectra in each panel are the results from FAST.

Neutral hydrogen gas is the most extended baryons in galaxies, while cold gas traced by CO is more concentrated to a galaxy center (red contour in Figure 1). With dynamical measurements of neutral hydrogen and CO, we can estimate the mass distribution of galaxies at different radii. Dynamical masses of these four galaxies estimated from the newly observed the neutral hydrogen line are 10 times higher than the observed baryon masses, indicating contribution of dark matter. On the other hand, dynamical masses estimated using previous CO observations were equivalent to their observed baryon masses. Therefore, the new FAST observation illustrates its ability of studying dark matter in galaxies using the neutral hydrogen 21cm emission line.

The FAST observation of these galaxies was an important part of an international research project, the Valparaíso ALMA Line Emission Survey (VALES), led by Prof. Edo Ibar from Valparaiso University in Chile. The VALES is a project of observing star forming galaxies using first-class international facilities such as SDSS, Herschel space observatory, ALMA, APEX and VLT. This international team has been publishing a series of scientific results.

FAST with the unpreceded sensitivity provides a very unique chance to observe the extra-galactic neutral hydrogen, and therefore has been adding to the list modern astronomical facilities used by this international collaboration. The FAST observation time was awarded in the Share-risk Observing call during the FAST Commissioning Phase. The team will apply for FAST time to further study the neutral hydrogen properties of VALES galaxies.

The paper can be accessed at https://www.aanda.org/articles/aa/full_html/2020/06/aa38483-20/aa38483-20.html

The 6th “From AGN to starburst: A multi-wavelength synergy” Meeting Successfully Held in Guiyang, China

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During Aug. 12-16, 2019, the 6th “From AGN to starburst: A multi-wavelength synergy” was successfully held in Guiyang, China. The meeting was organized by National Astronomy Observatory of CAS (NAOC) and CAS South American Center of Astronomy (CASSACA), along with the Purple Mountain Observatory (PMO). Over 100 participants from 13 countries and regions attended this meeting. The AGN-starburst meeting series is a well-known international galaxy physics conference and it keeps focusing on the most advanced scientific researches and challenges in galaxy formation and evolution.

Poster of the meeting

Jiasheng Huang, SOC & Y.Sophia Dai, chair of SOC/LOC, delivered welcome speeches at the meeting

Throughout five days, over fifty reports and 17 poster talks were given by experts, young researchers and students. The presentations have a wide coverage, from the latest multi-wavelength observational results across redshifts, to the state-of-art simulation and theoretical models. Recent ALMA (the Atacama Large Millimeter/submillimeter Array) results are reported in studies of outflows, gas distribution and star formation efficiency in both AGNs and starburst galaxies. As for sky surveys in optical and infrared (IR) wavelength, speakers talked about features in different types of active galaxies and observational evidences related to “galaxy quenching”. These reports gave a detailed physical view of the relationship between supermassive blackhole (SMBH) and galaxy evolution.

(Nick Scoville, Marcia Rieke, Xiaohui Fan, Erin Hicks, Matt Malkan and Lei Hao)

(John Silverman, Luis Ho, Ran Wang, Yu Gao, Jeyhan Kartaltepe and Richard Bower)

Selected photos of experts giving presentations

On Aug. 15th, participants enjoyed a fantastic visit to the FAST (Five-hundred-meter Aperture Spherical Telescope) observatory, organized by LOC members Dr. Qisheng Li and Gaofeng Pan from the FAST observatory. After the introduction report by Dr. Chao-Wei Tsai, people had heated discussion and expressed appreciation as well as intentions for future collaborations with FAST.

Participants at the FAST observatory

Besides presentations, the meeting also sets aside time every day for free discussions. Heated debates and discussions were a common scene during these discussion sessions, over evidences in the connection between AGN and starburst, challenges in linking theoretical and simulations models to observations, as well as topics on large-scale galaxy evolution.

George Rieke, David Rosario, Jiasheng Huang, Yingjie Peng, David Elbaz, Dave Sanders in discussions

The last day of the meeting, a special session was dedicated to the many different future instruments and evolutionary results the new surveys would bring us. Principle Investigators or experts from FAST, JWST (James Webb Space Telescope), EP (Einstein Probe), eXTP (enhanced X-ray Timing and Polarimetry Mission) and CSST (Chinese Space Station Telescope) and other future instruments/surveys introduced the latest progresses and future plans. Final remarks and demand for future series were given by the SOC representatives at the end of the meeting. Participants thanked the organization by the LOC and SOC and looked forward to future international collaborations and the next meeting.

Translated by: Gaoxiang Jin, Y.Sophia Dai

Photo credit: Zijian Li, Gaoxiang Jin, Xu Shao

[Reprinted] Cloaked Black Hole Discovered in Early Universe using NASA’s Chandra

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NASA/CXC

Astronomers have discovered evidence for the farthest “cloaked” black hole found to date, using NASA’s Chandra X-ray Observatory. At only about 6% of the current age of the universe, this is the first indication of a black hole hidden by gas at such an early time in the history of the cosmos.

Supermassive black holes, which are millions to billions of times more massive than our Sun, typically grow by pulling in material from a disk of surrounding matter. Rapid growth generates large amounts of radiation in a very small region around the black hole. Scientists call this extremely bright, compact source a “quasar.”

According to current theories, a dense cloud of gas feeds material into the disk surrounding a supermassive black hole during its period of early growth, which “cloaks” or hides much of the quasar’s bright light from our view. As the black hole consumes material and becomes more massive, the gas in the cloud is depleted, until the black hole and its bright disk are uncovered.

“It’s extraordinarily challenging to find quasars in this cloaked phase because so much of their radiation is absorbed and cannot be detected by current instruments,” said Fabio Vito of the Pontificia Universidad Católica de Chile, in Santiago, Chile, who led the study. “Thanks to Chandra and the ability of X-rays to pierce through the obscuring cloud, we think we’ve finally succeeded.”

The new finding came from observations of a quasar called PSO167-13, which was first discovered by Pan-STARRS, an optical-light telescope in Hawaii. Optical observations from these and other surveys have detected about 180 quasars already shining brightly when the universe was less than a billion years old, or about 8 percent of its present age. These surveys were only considered effective at finding unobscured black holes, because the radiation they detect is suppressed by even thin clouds of gas and dust. Since PSO167-13 was part of those observations, this quasar was expected to be unobscured, too.

Vito’s team were able to test this idea by using Chandra to observe PSO167-13 and nine other quasars discovered with optical surveys. After 16 hours of observation, only three X-ray light particles were detected from PSO167-13, all with relatively high energies. Since low-energy X-rays are more easily absorbed than higher energy ones, the likely explanation is that the quasar is highly obscured by gas, allowing only high-energy X-rays to be detected.

“This was a complete surprise”, said co-author Niel Brandt of Penn State University in University Park, Pennsylvania. “It was like we were expecting a moth but saw a cocoon instead. None of the other nine quasars we observed were cloaked, which is what we anticipated.”

An interesting twist for PSO167-13 is that the galaxy hosting the quasar has a close companion galaxy, visible in data previously obtained with the Atacama Large Millimeter Array (ALMA) of radio dishes in Chile and NASA’s Hubble Space Telescope. Because of their close separation and the faintness of the X-ray source, the team was unable to determine whether the newly-discovered X-ray emission is associated with the quasar PSO167-13 or with the companion galaxy.

If the X-rays come from the known quasar, then astronomers need to develop an explanation for why the quasar appeared highly obscured in X-rays but not in optical light. One possibility is that there has been a large and rapid increase in cloaking of the quasar during the three years between when the optical and the X-ray observations were made.

On the other hand, if instead the X-rays arise from the companion galaxy, then it represents the detection of a new quasar in close proximity to PSO167-13. This quasar pair would be the most distant yet detected.

In either of these two cases, the quasar detected by Chandra would be the most distant cloaked one yet seen, at 850 million years after the Big Bang. The previous record holder has been observed 1.3 billion years after the Big Bang.

The authors plan to follow up with more observations to learn more.

“With a longer Chandra observation we’ll be able to get a better estimate of how obscured this black hole is,” said co-author Franz Bauer, also from the Pontificia Universidad Católica de Chile, “and make a confident identification of the X-ray source with either the known quasar or the companion galaxy.”

The authors also plan to search for more examples of highly obscured black holes.

“We suspect that the majority of supermassive black holes in the early universe are cloaked: it’s then crucial to detect and study them to understand how they could grow to masses of a billion suns so quickly,” said co-author Roberto Gilli of INAF in Bologna, Italy.

A paper describing these results is accepted for publication in Astronomy and Astrophysics and is available online. NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science and flight operations from Cambridge, Massachusetts.
Other materials about the findings are available at:
http://chandra.si.edu

The Fifth China-Chile Bi-lateral Astronomy Science Meeting was successfully held in Kunming during Jan. 23-26, 2019

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Meeting group photo

In order to promote the communication and collaboration between astronomy communities of China and Chile, sponsored by Chinese Academy of Sciences (CAS), National Natural Science Foundation of China (NSFC), National Astronomical Observatories, CAS (NAOC), the “Fifth Chile-China Bi-lateral Astronomy Science Meeting” was successfully held in Kunming during Jan. 23-26, 2019. The meeting was organized by the CAS South American Center for Astronomy (CASSACA), also known as China-Chile Joint Center for Astronomy, along with Yunnan Astronomical Observatory (YNAO).

A glance at the meeting

CASSACA is one of the overseas projects initiated by CAS to develop cooperation in science and technology with foreign countries. In February 2013, CASSACA was inaugurated at NAOC, and its Santiago office was inaugurated in October 2013 at University of Chile. The Center serves as a platform for collaboration in astronomical research and related technologies between China and South America countries. The Center helps to build international scientific teams and joint programs engaging in frontier astronomy research. The China-Chile Astronomy Workshop is a major platform to strengthen communications in astronomical research between the two countries, and has been held alternately in Chile and China. It has been proven to be successful in the past meetings of the series, prompting knowledge and information exchange between astronomers, and initiating collaborative projects and joint programs.

Hui Sun, Director of America and Oceania Department, Bureau of International Co-operation, CAS, addressing the meeting
Suijian Xue, Deputy president of NAOC, addressing the meeting
Jiasheng Huang, Chief Scientist of CASSACA, hosting the meeting
Patricio Rojo , Chairman of SOCHIAS, introducing the astronomy in Chile
Participants discussing

Around 70 participants attended this Meeting, including experts, young scientists and students, coming from more than 20 institutes of China, Chile, and other countries. Professor. Jiasheng Huang, Chief Scientist of CASSACA, and Professor Jinming Bai, president of YNAO, offered their welcome as the hosts; Hui Sun, Director of Division of America and Oceanian Affairs, Bureau of International Cooperation, CAS and Suijian Xue, Deputy Director General of NAOC, both addressed the meeting; Dr. Wei Wang, Deputy Director of CASSACA, introduced the current status and future prospects of the Center; Professor Patricio Rojo, Chairman of Astronomical Society of Chile (SOCHIAS) and other Chilean astronomers expressed high expectations for the Chile-China cooperation, and gave a lot of suggestions and comments. At this Meeting, directors or their representatives of nearly all major astronomical observatories/departments of China and Chile summarized the major research areas and current activities of their institutions, including detailed talks on recent research highlights. During the four-day workshop, astronomers from both countries communicated cordially and comprehensively, reviewing the existing ties and finding opportunities for future collaborations. The bilateral meeting is recognized as an important catalyst for Chile-China astronomy communications, and a useful model for CAS to advance international cooperation widely.

CASSACA scientist reveals the connection between radiation and shape of circum-nuclear materials around super-massive black holes

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[Dr. Claudio Ricci, a CAS-CONICYT Postdoctoral Fellow in astronomy,  led an important paper in《Nature》on September 27th 2017, in which he reported recent major progress regarding how radiation feedback controls the shape of close environment around super-massive black holes, drawn from a multi-band survey of a sample of black holes selected in the hard X-ray band.]

A black hole is a place in space-time where gravity pulls are so strong that even light cannot get out, it is therefore “black” in any bands. The theory of general relativity predicts that a sufficiently large and dense mass would deform space -time and give birth to a black hole. Despite its invisible interior, a black hole can be indirectly inferred and investigated at various wavelengths through its interactions with the surrounding and in-falling materials.

It is known for decades that very heavy black holes inhabit the centers of galaxies (including our own galaxy, the Milky Way), but are hidden by gas and dust. Some of these black holes can “eat” materials from their environment, and emit a lot of light during this process. Most of these “luminous” black holes are surrounded by large amount of gas and dust, distributed in a doughnut-like structure. Such a structure could resemble a pantry, which guarantees that the black hole can keep eating, radiating and growing. However, it is not known where exactly this material is located, and what the relationship is between light produced by the black hole and the dusty gas.

In order to address this long-standing issue, Dr. Claudio Ricci, a postdoc fellow supported by Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and his collaborators made use of observations carried out in the X-ray band, similar to what is typically used for radiographies in hospitals. With each observation performing these “space radiographies”, they could measure the amount of material around the black hole, and then study its evolution.

This project started in 2013, and it took the authors many years to create the large database used for their research, using data from space telescopes as well as ground-based observatories, such as those in Chile. The Chilean telescopes were extremely important for measuring the properties of the black holes, and in particular, for “weighing” their masses. The main X-ray instrument used was the NASA satellite Swift, but also data from the satellites XMM-Newton of ESA, Suzaku of JAXA, and another NASA telescope, Chandra, were used. In the optical band the facilities used include the Sloan Digital Sky Survey, the UK Schmidt telescope, Gemini, CTIO, DuPont and SAAO.

With this work, Ricci and collaborators discovered the process that controls the interaction between light produced by the black hole and the gas that surrounds it, and showed that most of the material around black holes is located close to it. The authors found that, when the black hole emits a lot of light, this light pushes away the material from its vicinity; in other words, the gas can “evaporate” because of the large amount of energy released by the material falling rapidly onto the black hole. This could also mean that, if the black hole “eats” too rapidly, the energy produced could destroy the “food” available for the future.

It is a major step forward to reveal a clear picture of the connection between radiation feedback and the surrounding material’s shape. “The next step will be to further understand the details of this behavior, and what happens to the material that is pushed away from the black hole”, said Dr. Ricci, the leading author of this work.

Figure 1. Artistic impression of the gas and dust surrounding an accreting supermassive black hole. Taken from NASA/JPL/Caltech.

Figure 2. Schematic representation of the material surrounding supermassive black holes for different ranges of Eddington ratio. The Eddington ratio is the ratio between the bolometric and the Eddington luminosity, where the latter is defined as the luminosity at which the radiation pressure from a source, in this case the accreting SMBH, balances the gravitational attraction. Taken from Ricci et al. (2017, Nature Letter).

Young scientist from CASSACA pens review on accreting supermassive black holes in Nature Astronomy

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Dr. Claudio Ricci, a CAS-CONICYT Postdoctoral Fellow in astronomy, recently authored a review paper in 《Nature Astronomy》 with Cristina Ramos Almeida of IAC Tenerife, in which they summarized the most important developments of the past ten years in the fields of accreting black holes and circum-nuclear materials, as revealed by observations in the X-ray and infrared bands.

All massive galaxies host supermassive black holes (SMBH) at their centers, and these objects are often found to be hidden behind large amounts of gas and dust. This circum-nuclear material is what eventually accretes onto the black hole, allowing it to grow, and its structure and evolution have been the subject of intense study in the past decade. Chinese Academy of Sciences South America Center for Astronomy (CASSACA)’s postdoctoral fellow Claudio Ricci and Dr. Cristina Ramos Almeida (IAC Tenerife) were recently invited to write a review for《Nature Astronomy》 on this subject, with the idea of combining results obtained from X-ray and infrared studies of the close environments of supermassive black holes. These two energy bands are highly complementary: while X-rays are produced very close to the supermassive black hole and allow the study of radiation absorbed and reflected, infrared radiation is directly produced by the dust around the black hole.

A black hole is a place in space where gravity pulls so much that even light cannot get out, and therefore itself is “black” in any bands. The theory of general relativity predicts that a sufficiently large and compact mass can deform space time and give birth to a black hole. Black holes of stellar masses are expected to form when very massive stars collapse at the end of their life cycle. After a black hole is formed, it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. The first widely-accepted black hole is Cygnus X-1 discovered in 1964, and it weighs about 15 solar masses (Figure 1). The well-known radio source named Sagittarius A*, sitting at the core of our own Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses.

Despite its invisible interior, the presence of a black hole can be inferred through its interactions with matter. Circum-nuclear materials falls onto a black hole, and forms an AGN (active galactic nucleus), one of the brightest objects in the universe, including an external accretion disk, an X-ray emitting corona, a broad-line region (BLR), a torus and a narrow-line region (NLR) (Figure 2), which have various physical characteristics, and their radiation are widely used to study the black hole and its surroundings.

The review summarizes the most important developments of the past ten years in this field, and particularly in light of the most advanced X-ray and IR facilities. The authors discuss why the circum-nuclear material is anisotropic, clumpy, and connects with the host galaxy via gas inflow/outflows. They also highlight the importance of dust emission from the polar region of the AGN, possibly related to outflows caused by radiation pressure from the accreting supermassive black hole. Future observing facilities will allow a better understanding of the nuclear environment of AGN, and a fuller description on how it links the black hole to its host galaxy. In particular, the upcoming James Webb Space Telescope (JWST) will allow us to probe the structure and evolution of AGN’s polar dust, while high-resolution spectrometers, such as the ones on board XARM and Athena satellites, will shed light on the physical characteristics of the gas and dust.

Dr. Ricci was invited to write this review because of his significant contribution to this field of research, and in particular in the light of his recent studies on the properties of the most heavily obscured accretion events in the Universe, and of the discovery that the merger of two or more galaxies can strongly affect the surroundings of the supermassive black hole, enriching it in gas and dust. Being able to publish review papers in such prestigious scholarly journals is usually an indication of wide acceptance and recognition of the author’s research work.

For young scientists such as Ricci and Almeida, this is an even more remarkable testimonial to their creative contribution to the relevant subject matter.

Figure 1. An artist’s drawing of a black hole named Cygnus X-1. It formed when a large star caved in. This black hole pulls matter from the blue star beside it. Taken from NASA/CXC/M. Weiss.

Figure 2. Sketch of the main AGN structures, seen along the equatorial and polar directions. From the center to host-galaxy scales: SMBH (Super Massive Black Hole), accretion disk and X-ray emitting corona, BLR (Broad-Line Region), torus and NLR (Narrow-Line Region). Different colors indicate different compositions or densities. Taken from Ramos Almeida & Ricci (2017, Nature Astronomy).

For more information about the Nature Astronomy Review, please visit https://www.nature.com/articles/s41550-017-0232-z.

The 2017 China Latin-America Young Scientist Exchange Program

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Ministry of Science and Technology of China announces the 2017 China-Latin-American Young Scientist Exchange Program

To promote the long-term scientific and technological partnership between China and Latin American and Caribbean (LAC) countries, the Ministry of Science and Technology of China (MOST) decides to continue the “China-Latin America Young Scholars Exchange Program” for all institutes, universities and enterprises this year in LAC. Interested researchers are encouraged to submit applications.

Specific requirements are as follows:

  1. Job requirements
    1. Not classified
    2. Not diplomatic education;
    3. Scientific research positions with clear plans and responsibilities;
    4. The young scientists must work with Chinese research team;
    5. Working in China for 6 months or 12 months, and can be extended once when necessary
  2. Appropriate applicants
    1. Young scientists from Latin America and the Caribbean countries, with preferences to those countries with bilateral intergovernmental committees, subcommittees for the cooperation in science and technology (like Cuba, Mexico, Brazil, Chile, Argentina, Uruguay, Colombia, Ecuador, Costa Rica, etc.)
    2. Under the age of 45;
    3. With more than 5 years of scientific research experience, or a doctorate degree;
    4. Good at English or Chinese;
    5. Physical and mental healthy, and capable of conducting scientific research work;
    6. Commitment to full-time work in China during the grant period;
    7. Commitment to comply with relevant Chinese laws during China.

 

  1. Funding methods and standards
    1. MOST will provide 12, 500 yuan per person per month for young scientists included in the Program, to cover their housing subsidy, living allowance and various types of insurance in China. In principle, international travel expenses shall be excluded, to ensure the smooth implementation of the project. However, if buying international air tickets is indeed necessary for the awarded young scientists, the cost will be subtracted from their living allowance;
    2. The funds will be allocated to the Chinese institutions, which will host the awarded young scientist through the China Science and Technology Exchange Center. All the funds shall be only used for the work and living of the young Chinese scientists staying in China, and the host institution shall not deduct or accrue the management fees.
  1. Application and funding procedures
    1. Fill in the 2017 China-LAC Young Scientists Exchange Program Application Form and the recommendation form. The latter form must be stamped and signed by the sending institution of the applicant. Please send the two forms (pdf files) to cassaca@bao.ac.cn.
    2. The China Science and Technology Exchange Center (CSTEC) will review and select of the applications, and submits it to the International Cooperation Department (ICD) of the MOST for final decision, according to the emphasis of the intergovernmental cooperation in science and technology. For the awarded application, project to confirm the funding, CSTEC will inform the Chinese host institutions in written form, and sign the contract with them
    3. The host institution and group should sign a working agreement with the LAC young scientists, to clarify the responsibilities, obligations, and describe the proposed collaboration research programs.
    4. The host institution and group is responsible for assisting the LAC young scientists to handle all necessary paperwork required for visa applications, and help to arrange accommodations in China.

The deadline for the application is September 15, 2017. If there is anything unclear, please feel free to contact Dr. Wei Wang at wangw@bao.ac.cn.

[Attachments]

1, the 2017 in the young scientists exchange program application form

2, the 2017 in the young scientists exchange program recommended form

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

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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