Astronomers Studied Lenticular Galaxy, “PGC 38025” (Astronomy)

Chen and colleagues presented optical integral field spectroscopic (IFS) observation with the 3.5 meter telescope at Calar Alto (CAHA) Observatory, and high-resolution millimeter observation with the NOrthern Extended Millimeter Array (NOEMA), of the SDSS J120237.07+642235.3 (PGC 38025), a star-forming field lenticular galaxy with an off-nuclear blue core. They estimated star formation rates and metallicities of the galaxy and its blue core. Their study recently appeared on Journal Arxiv.

Lenticular galaxies (S0s) are morphologically situated between ellipticals and spirals, e.g., armless and with dense cores (bulges) as ellipticals, while having disk component as spirals do. They are traditionally considered as having used up most of their gas reservoir which is critical for star formation.

S0s in a group and/or cluster (i.e., dense environment) are considered to be transformed from spirals due to environmental effects, e.g., ram-pressure stripping in hot intergalactic medium (IGM), gravitational tidal effect and harassment, and encounter of galaxies. However, most rare field S0s cannot be fitted into the common formation scenario (environmental triggered formation) of S0s in groups/clusters, and may contribute to the diversity in the properties of S0s. Studying the evolution of S0 galaxies is essential to understanding formation and evolution of all different types of galaxies.

Now, Chen and colleagues carried out study on SDSS J120237.07+642235.3 (also called PGC 38025), a star forming field lenticular galaxy with an off-nuclear blue core, located ∼ 1 kpc away from the galaxy centre (as shown in Featured image). Its early-type morphology, together with the extended star-formation and off-nuclear blue core make PGC 38025 to be an ideal target in studying formation and evolution of S0s.

Table 1: Properties of PGC 38025 © Chen et al.

At first, astronomers obtained CAHA optical IFS observation and compared it to single aperture spectroscopy such as Sloan Digital Sky Survey (SDSS), which is highly competent in the study on spatial extended star formation mechanism of PGC 38025 and nature of its off-nuclear blue core. In order to study the origin of the star forming activity in this galaxy, they also carried out the interferometer radio observation from IRAM NOEMA to reveal molecular gas content and spatial distribution of PGC 38025.

They found that star formation rate of PGC 38025 and its accompanying blue core are 0.446 and 0.023 M yr¯1, respectively. While, the metallicity 12+log(O/H) of them are 8.42 and 8.41, respectively. The metallicity of off-nuclear core is the same within the errors, which indicates that this blue core may be the same origin with the galaxy PGC 38025, or their ISM is already well-mixed during galaxy evolution.

“The ionized gas and cold molecular gas in PGC 38025 show the same spatial distribution and kinematics, whilst rotating misaligned with stellar component.”

— told Chen, first author of the study

They also found that the redshift of off-nuclear blue core is identical to PGC 38025, and the spectrum of the off-nuclear blue core has strong emission-line feature and nearly zero continuum. In addition, they determined through BPT diagnostics that, this off-nuclear blue core is an H ii region excited by star formation. CO detection further revealed the molecular gas served as reservoir (gas fraction MH2 /M∗ reaches ∼ 10%) of PGC 38025, supplying for star formation on an extended region, including this blue core. The external gas (ionized and molecular) built a polar disk in PGC 38025. Astronomers suggested that, this blue core as a part of this disk, relative denser and thermal cold (with low velocity dispersion), generated during misaligned gas accretion and rotation.

Moreover, they suggested that star formation in PGC 38025 is triggered by a gas-rich minor merger, and the off-nuclear blue core might be a local star-formation happened during the accretion/merger process.

Figure 1. PV maps of 3DBarolo modelling, alonging the major and minor axis. Using CO data, is shown in grey and blue contour. The model is shown with red contours, and yellow dots shows the resulting rotation curve of the galaxy, projected on the data. © Chen et al.

“Finally, we found that there is another high velocity component decreasing from the centre to the blue core, which may also be an indication of bipolar outflows. We will further explore the case in a future work in the light of granted VLA HI data.”

— concluded authors of the study

Featured image: Optical grz composite image from DESI Legacy Imaging Surveys © Chen et al.

Reference: Chen Zhengyi, Gu Qiu-Sheng, Rubén García-Benito, Zhang Zhi-Yu, Ge Xue, Xiao Mengyuan, Yu Xiaoling, “PGC 38025: A Star-forming Lenticular Galaxy With an Off-nuclear Star-forming Core”, ArXiv, pp. 1-16, 2021.

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Giant Planet at Large Distance From Sun-like Star Puzzles Astronomers (Planetary Science)

A team of astronomers led by Dutch scientists have directly imaged a giant planet orbiting at a large distance around a sun-like star. Why this planet is so massive, and how it got to be there, is still a mystery. The researchers will publish their findings in the journal Astronomy & Astrophysics.

The planet in question is YSES 2b, located 360 light years from Earth in the direction of the southern constellation of Musca (Latin for The Fly). The gaseous planet is six times heavier than Jupiter, the largest planet in our solar system. The newly discovered planet orbits 110 times more distant from its star than the Earth does from the Sun (or 20 times the distance between the Sun and Jupiter). The accompanying star is only 14 million years old and resembles our Sun in its childhood.

Direct image of exoplanet YSES 2b (bottom right) and its star (centre). (c) ESO/SPHERE/VLT/Bohn et al.

The large distance from the planet to the star presents a puzzle to astronomers, because it does not seem to fit either of the two most well-known models for the formation of large gaseous planets. If the planet had grown in its current location far from the star by means of core accretion, it would be too heavy because there is not enough material to make a huge planet at this large distance from the star. If the planet was created by so-called gravitational instability in the planetary disk, it appears to be not heavy enough. A third possibility is that the planet formed close to the star by core accretion and then migrated outwards. Such a migration, however, would require the gravitational influence of a second planet, which the researchers have not yet found.

Young Suns Exoplanet Survey (YSES)
The astronomers will continue to investigate the surroundings of this unusual planet and its star in the near future and hope to learn more about the system, and they will continue to search for other gaseous planets around young, sun-like stars. Current telescopes are not yet large enough to carry out direct imaging of earth-like planets around sun-like stars.

Lead researcher Alexander Bohn (Leiden University): “By investigating more Jupiter-like exoplanets in the near future, we will learn more about the formation processes of gas giants around sun-like stars.”

The planet YSES 2b was discovered with the Young Suns Exoplanet Survey (YSES). This survey already provided the first direct image of a multi-planet system around a Sun-like star in 2020. The researchers made their observations in 2018 and 2020 using the Very Large Telescope of the European Southern Observatory (ESO) in Chile. They used the telescope’s SPHERE instrument for this. This instrument was co-developed by the Netherlands and can capture direct and indirect light from exoplanets.

Featured image: A direct image of the exoplanet YSES 2b (bottom right) and its star (centre). The star is blocked by a so-called coronagraph. (c) ESO/SPHERE/VLT/Bohn et al.

Scientific paper
Discovery of a directly imaged planet to the young solar analog YSES 2. By: Alexander J. Bohn et al. Accepted for publication in Astronomy & Astrophysics [original | free preprint (pdf)].

Provided by NOVA Astronomy

A Superluminous Supernova from a Massive Progenitor Star (Astronomy)

Stars greater than about eight solar-masses end their lives spectacularly as supernovae. These single-star supernovae are called core collapse supernovae because their dense cores, composed primarily of iron at this late stage of their lives, are no longer able to withstand the inward pressure of gravity and they collapse before exploding. Core collapse supernovae that display strong atomic hydrogen emission lines are thought to result from the explosions of red supergiant stars, massive stars that have evolved beyond their principle hydrogen burning stage and swelled in radius. Until recently, astronomers thought these stars were relatively quiescent until their final demise, but evidence has been accumulating that they actually experience strong mass loss before exploding. In some models, additional radiation is emitted when ejecta from the supernovae encounter these mass loss envelopes in shocks, and variations in this process are responsible for the observed differences in the emission from core collapse supernovae.

Over the last decade, a new subclass of supernovae has been identified, called superluminous supernovae (SLSNe). They can be as much as ten times as luminous as usual supernovae at their peak and fall roughly into two groups depending on whether they have strong or weak hydrogen emission. Some hydrogen-rich SLSNe show no signs of shocked emission from an envelope, however, adding to the complexity of the picture. Supernovae are key cosmological yardsticks because they are so bright and can be seen shining in the early epochs of the universe; the most distant supernova so far dates from an epoch only about three billion years after the big bang. The distances are reliably determined by comparing the measured and intrinsic luminosities, but only when the intrinsic luminosities are accurately modeled. Astronomers are therefore working to account for all the various classes and subclasses.

CfA astronomer Emilio Falco was a member of a team of astronomers who used the “All-Sky Automated Survey for Supernovae” (ASAS-SN) project, consisting of twenty-four telescopes world-wide, to automatically survey the visible sky for supernovae. The team, following up on one source ASASSN-18am (SN2018gk), concludes it is a rare, luminous, hydrogen-rich supernova but with no evidence of ejecta interacting with an envelope. The scientists conclude that the star must have had only a modest wind, only about two ten-thousandths of a solar-mass per year (some X-ray measurements suggest it could have been even smaller). The scientists estimate that the progenitor star probably had a mass of between nineteen and twenty-six solar-masses.

“ASASSN-18am/SN 2018gk: an overluminous Type IIb supernova from a massive progenitor” is published in MNRAS.

Featured image: An optical image showing the superluminous supernova ASASSN-18am in the outskirts of its host galaxy (green markers). The image was taken 131 days after the explosion. Bose et al, 2021

Reference: “ASASSN-18am/SN 2018gk: an overluminous Type IIb supernova from a massive progenitor,” Subhash Bose, Subo Dong, C. S. Kochanek, M. D. Stritzinger, Chris Ashall, Stefano Benetti, E. Falco, Alexei V. Filippenko, Andrea Pastorello, Jose L. Prieto, Auni Somero, Tuguldur Sukhbold, Junbo Zhang, Katie Auchettl, Thomas G. Brink, J. S. Brown, Ping Chen, A. Fiore, Dirk Grupe, T. W.-S. Holoien, Peter Lundqvist , Seppo Mattila, Robert Mutel, David Pooley, R. S. Post, Naveen Reddy, Thomas M. Reynolds, Benjamin J. Shappee, K. Z. Stanek, Todd A. Thompson, S. Villanueva, Jr. and WeiKang Zheng, MNRAS 503, 3472, 2021.

Provided by Harvard-Smithsonian Center for Astrophysics

Research Shows Pain Relieving Effects of CBD (Medicine)

A new study led by researchers at Syracuse University sheds light on the ability of CBD to reduce pain along with the impact that the so-called placebo effect may have on pain outcomes

It’s been hailed as a wonder drug and it’s certainly creating wonder profits. By some estimates, the Cannabidiol (or CBD) market could be worth $20 billion dollars by 2024. While users tout its effectiveness in pain relief, up until now there’s been limited experimental human research on the actual effectiveness of the drug. However, a new study led by researchers at Syracuse University sheds light on the ability of CBD to reduce pain along with the impact that the so-called placebo effect may have on pain outcomes.

“For science and the public at large the question remained, is the pain relief that CBD users claim to experience due to pharmacological effects or placebo effects,” asked Martin De Vita, a researcher in the psychology department at Syracuse University’s College of Arts and Sciences. “That’s a fair question because we know that simply telling someone that a substance has the ability to relieve their pain can actually cause robust changes in their pain sensitivity. These are called expectancy effects.” De Vita, along with Syracuse Emeritus Psychology Professor Stephen Maisto, were uniquely prepared to answer that exact question. The pair, along with fellow lab member and doctoral candidate Dezarie Moskal, previously conducted the first systematic review and meta-analysis of experimental research examining the effects cannabinoid drugs on pain. As the first experimental pain trial to examine CBD, their study yielded consistent and noteworthy results. Among other findings, the data showed that CBD and expectancies for receiving CBD do not appear to reduce experimental pain intensity, but do make the pain feel less unpleasant.

Syracuse University Emeritus Psychology Professor Stephen Maisto is a coauthor of the CBD pain relief study. © Syracuse University

De Vita and Maisto used sophisticated equipment that safely induces experimental heat pain, allowing them to measure how the recipient’s nervous system reacts and responds to it. “Then we administer a drug, like pure CBD, or a placebo and then re-assess their pain responses and see how they change based on which substance was administered,” said De Vita. Researchers then took it a step farther by manipulating the information given to participants about which substances they received. In some cases, participants were told that they got CBD when they actually received a placebo, or told they would be getting a placebo when they actually got CBD. “That way we could parse out whether it was the drug that relieved the pain, or whether it was the expectation that they had received the drug that reduced their pain,” according to De Vita. “We hypothesized that we would primarily detect expectancy-induced placebo analgesia (pain relief). What we found though after measuring several different pain outcomes is that it’s actually a little bit of both. That is, we found improvements in pain measures caused by the pharmacological effects of CBD and the psychological effects of just expecting that they had gotten CBD. It was pretty remarkable and surprising.”

“The data is exciting but pretty complex in that different pain measures responded differently to the drug effect, to the expectancy, or both the drug and expectancy combined–so we’re still trying to figure out what is behind the differential data with different kinds of pain measures,” said Maisto. “The next step is studying the mechanisms underlying these findings and figuring out why giving instructions or CBD itself causes certain reactions to a pain stimulus.”

Dezarie Moskal is a doctoral candidate at Syracuse University and assisted in the CBD pain relief study. © Syracuse University

Most people think of pain as an on and off switch, you either have it or you don’t. But pain, as De Vita describes it, is a complex phenomenon with several dimensions influenced by psychological and biological factors. For example, whereas pain intensity reflects a “sensory” dimension of pain, unpleasantness represents an “affective,” or emotional, aspect of pain. “If you think of pain as the noxious noise coming from a radio the volume can represent the intensity of the pain, while the station can represent the quality,” said De Vita. Results from his previous study showed that while cannabinoid drugs weren’t reducing the volume of pain, they were “changing the channel making it a little less unpleasant.” According to De Vita, “It’s not sunshine and rainbows pleasant, but something slightly less bothersome. We replicated that in this study and found that CBD and expectancies didn’t significantly reduce the volume of the pain, but they did make it less unpleasant–it didn’t bother them as much.” As part of the study De Vita and Maisto developed advanced experimental pain measurement protocols “to pop the hood and start looking at some of these other mechanistic pain processes,” said De Vita. “It’s not just pain, yes or no, but there are these other dimensions of pain, and it would be interesting to see which ones are being targeted. We found that sometimes pharmacological effects of CBD brought down some of those, but the expectancies did not. Sometimes they both did it. Sometimes it was just the expectancy. And so, we were going into this thinking we were going to primarily detect the expectancy-induced pain relief but what we found out was way more complex than that and that’s exciting.”

One important note to also consider is the source of the CBD. “What we used in our study was pure CBD isolate oil,” said De Vita. “Commercially available CBD products differ in their content and purity, so results might be different for different CBD products, depending on what other compounds they may or may not contain.”

Martin De Vita is currently completing a clinical psychology internship at Brooke Army Medical Center, JBSA, TX. The view(s) expressed herein are those of the author(s) and do not reflect the official policy or position of Brooke Army Medical Center, the U.S. Army Medical Department, the U.S. Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force and Department of Defense or the U.S. Government.

Featured image: Martin De Vita is a researcher in the psychology department at Syracuse University’s College of Arts and Sciences and coauthor of the study. © Syracuse University

Reference: De Vita, M. J., Maisto, S. A., Gilmour, C. E., McGuire, L., Tarvin, E., & Moskal, D. (2021). The effects of cannabidiol and analgesic expectancies on experimental pain reactivity in healthy adults: A balanced placebo design trial. Experimental and Clinical Psychopharmacology. Advance online publication.

Provided by Syracuse University

New Laser Damage Mechanism Proposed for Dual-ion Sputtered Coatings under Fundamental Frequency Laser Irradiation (Physics)

Recently, researchers from the Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences (CAS) have proposed a new laser damage mechanism for dual-ion sputtered coatings under fundamental frequency laser irradiation, which can match well the different damage morphology characteristics at high and low energies of sputtered dense coatings. The results have been published in Scientific Reports

Dual ion beam sputtered coatings have excellent mechanical properties and environmental stability, making them suitable for use in space laser systems. Laser damage to coatings is a bottleneck in laser systems, and laser damage to sputtered coatings in space is relevant to the stability of the launch and operation of the entire spacecraft mission. The study of the physical mechanisms of laser damage in sputtered coatings is crucial to finding ways to improve the performance of coatings, and current laser damage models cannot provide a good explanation for the phenomenon of large-size peeling from sputtered coatings. 

In this research, a new model for laser damage of dual-ion sputtered coatings under fundamental frequency laser irradiation has been proposed and matched to experimental results.

Schematic diagram of laser damage process: (d) initial defect absorbing laser energy, thermomechanical coupling effect; (e) ionizing air to form plasma, peeling off effects. (Image by SIOM)

The researchers found that the dual ion beam sputtered multilayer coatings exhibit two typical damage patterns under fundamental frequency laser, one is thermally coupled damage without layer peeling, and the other is a large area layer peeling damage pattern. The large layer peel effect is distinctly different from the honeycomb shape of the e-beam evaporated coatings and the ring ablation shape of fused silica. 

Therefore, they proposed the laser damage model based on the correlation between laser energy and air dissociation to explain the phenomenon by calculating the action process of air ionization waves, including the damage process caused by defects and the damage process of shock waves formed by ionized air. 

The physical model is validated against commonly used combinations of Al2O3/SiO2, Ta2O5/SiO2, and Nb2O5/SiO2 coatings and is found to be a good match, while the peeling effect is also found to be related to the thermal parameters of the different layers.

The analysis of the film damage process can help to improve the resistance to laser damage from the process and design perspectives, while the modified model can be extended to damage mechanisms of other laser materials. 

Related work was supported by the Key Project of International Science and Technology Innovation Cooperation between China and Italy, the National Natural Science Foundation of China, the Youth Innovation Promotion Council of CAS, and the Strategic Pioneer Science and Technology Special Project of CAS. 

Featured image: SEM morphologies of Al2O3/SiO2 coatings after laser irradiation: (a) close to laser damage threshold; (b) middle laser fluence; (c) high laser fluence. (Image by SIOM)

Reference: Guo, K., Wang, Y., Chen, R. et al. Laser-induced layers peeling of sputtering coatings at 1064 nm wavelength. Sci Rep 11, 3783 (2021).

Provided by Chinese Academy of Sciences

Scientists Develop Cost-efficient Diffuse Atmospheric-pressure Plasma Jet Methodologically (Physics)

As a new-type, economic, and convenient plasma technique, atmospheric-pressure plasma jets (APPJs) have received increasing attention in various applications, such as biomedical decontamination, material processing, thin film deposition, chemical analysis, and nanoscience. Atmospheric gas discharge is very likely to constrict into filaments and diffuse plasma formation is inefficient in most cases. Developing cost-efficient diffuse APPJs represents a significant challenge for high performance in the applications mentioned above.

A research group led by Prof. TANG Jie from the Xi’an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) demonstrated an untraditional roadmap to produce a cost-efficient diffuse plasma jet at atmospheric pressure.

In their work, in contrast to the well-known streamer coupling model, an alternative train of thought was demonstrated to generate a stable and diffuse plasma by expanding and quenching the existing filamentary discharge at the initial or middle stage of the streamer development.

Based on this guideline, a promising method was proposed to produce diffuse APPJs by a combination of pseudo-streamer discharge and pulseless glow discharge in the positive and negative alternations of applied voltage, respectively.

This combination process was realized by technically controlling the gas flow in a large gap dielectric-barrier discharges (DBDs), which is equipped with a thin quartz tube in a linear field. These results were published in Communications Physics.

According to the researchers, with the gas flow velocity comparable to the ion drift one, enhancing ambipolar diffusion near the edge of the positive-streamer channel promotes the radial diffusion of newly-produced electrons, realizing the radial expansion of channel.

In addition, weakening electric field in front of the streamer head through head expansion and field offset, prevents the further development of streamer, leading to a positive-pseudo- streamer discharge.

Furthermore, reducing electric field in front of the negative-streamer head through ion compensation, impedes the initial growth of streamer, resulting in a negative pulseless glow discharge.

With these merits, this work breaks through the bottleneck of restricting the formation of diffuse plasmas in atmospheric dielectric-barrier discharge, and provides a brand-new idea for development of large uniform plasma devices that are in urgent need for various plasma applications.

Featured image: Physical appearances of the plasma jet. (Image by XIOPM)

Reference: Li, J., Lei, B., Wang, J. et al. Atmospheric diffuse plasma jet formation from positive-pseudo-streamer and negative pulseless glow discharges. Commun Phys 4, 64 (2021).

Provided by Chinese Academy of Sciences

Researchers Discover Dark Gap Solitons in Dense Ultracold Atoms (Particle Physics)

Bose-Einstein condensates (BECs), created in ultracold bosonic atoms and degenerate quantum gases, are a macroscopic quantum phenomenon and considered as a single particle in mean-field theory. By preparing the BECs or ultracold atomic gases onto optical lattices, the existence of nonlinear matter waves and their dynamics, and simulate the condensed-matter physics can be detailly investigated.

Optical lattices have been a versatile toolbox to control BECs recently, and a wealth of emergent nonlinear phenomena have been found, including bright gap solitons and dark ones. However, the dark localized gap modes with a central dip, have not been well understood yet. In particular, the formation and property of dark gap solitons and how to stabilize them in dense BECs with quintic nonlinearity are still unclear. Are there any methods to explore the dark gap solitons?

A research team led by Prof. Dr. ZENG Jianhua from the Xi’an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) theoretically explored an open issue of creating stable matter-wave dark gap solitons in a one-dimensional optical lattice. The results were published in PHYSICAL REVIEW A.

According to the researchers, the principle of linear-stability analysis solved by means of the finite-difference method was utilized to verify that the stability of the so-found dark gap soliton requires only pure imaginary eigen-values. Moreover, the stability property of the dark gap solitons was also further checked in direct numerical simulation of the perturbed solutions.

In this research, two families of dark gap solitons, including the fundamental solitons and soliton clusters, optical lattices possessing shallow, medium shallow, and moderately deep lattices were found and their stability and instability regions in the underlying linear band-gap structures were identified utilizing linear-stability analysis and direct perturbed simulations.

The stability regions for both fundamental dark gap solitons and soliton clusters within the first band gap are narrow at a shallow lattice and become wider when increasing lattice depth, while both classes of dark gap modes cannot be stabilized in the second band gap. On the contrary, the dark gap solitons lying in the second gap predicted in dilute BECs with repulsive atom-atom interactions can be stable objects.

The results provide further insight into the unobserved dark gap modes in the fifth state of matter—the BEC, driving the development of soliton studies in the theoretical and experimental communities in BEC.

Featured image: Profiles, linear-stability spectra, and evolutions for 1D stable and unstable dark gap solitons. (Image by XIOPM)

Reference: Jiawei Li and Jianhua Zeng, “Dark matter-wave gap solitons in dense ultracold atoms trapped by a one-dimensional optical lattice”, Phys. Rev. A 103, 013320 – Published 27 January 2021. DOI:

Provided by Chinese Academy of Sciences

Chinese Researchers Detect the Largest Number of Galaxy Clusters (Astronomy)

Galaxy clusters are the largest gravitationally bound systems in the universe, which contain a lot of galaxies, gas, and dark matter. They are ideal laboratories to study galaxy formation and evolution in dense environments and also excellent probes to explore the large-scale structure, dark matter, and dark energy. 

A large sample of galaxy clusters at z < 1, when the universe is about 5.7 billion years old, is fundamental for accurately analyzing the late evolution of galaxies in dense environment, especially for those brightest cluster galaxies (BCGs). 

Recently, a research team led by Dr. ZOU Hu from National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) has utilized the deep imaging data from the Dark Energy Spectroscopic Instrument (DESI) imaging surveys and detected more than 540,000 galaxy clusters at z < 1. These clusters are by far the largest sample that has been found. 

Fig. 1 Redshift distribution of the galaxy clusters detected in the study. Others are the redshift distributions of the clusters that are found using the SDSS imaging data. The distributions are scaled by the survey area. (Image by NAOC) 

Their work was published in The Astrophysical Journal Supplement Series on April 13. 

The galaxy clusters detected in this work will be used for further studying the properties of member galaxies, evolution of massive central galaxies, mass assembly and star formation in dense environment, and gas properties in clusters, etc. 

Through international collaboration, Dr. ZOU Hu has participated the DESI project and conducted large-scale multi-wavelength imaging surveys, including the Beijing-Arizona Sky Survey (BASS). 

Before using the imaging data to detect galaxy clusters, the team has accurately estimated the photometric redshifts and stellar masses of about 300 million galaxies with r<23, which is about 6 million times fainter than the stars that the human eyes can see. Based on the photometric redshift catalog, they adopted a new fast peak clustering algorithm and detected more than 540,000 galaxy clusters with the number of members larger than 10. 

By contrast with those cluster finders based on red sequence, the researchers can detect the clusters that are lack of red galaxies. Compared with traditional overdensity detecting methods, the speed performance of the new method is better and member galaxies can be easily identified. In addition, they have preliminarily found more than a hundred strong lensing systems among these clusters. 

This work will play an important role in data analyses and scientific studies of future Chinese large telescopes and large-scale surveys, such as Chinese Space Station Telescope (CSST). 

Featured image: One of the detected clusters at the redshift of about 0.4. Some properties of the cluster and the brightest cluster galaxy (BCG) are displayed. The position of the BCG is marked by the small circle, the average position of the member galaxies by the cross, and the distance of 0.5 Mpc from the BCG by the big circle. (Image by NAOC) 

Reference: Hu Zou, Jinghua Gao, Xin Xu, Xu Zhou, Jun Ma, Zhimin Zhou, Tianmeng Zhang, Jundan Nie, Jiali Wang, and Suijian Xue, “Galaxy Clusters from the DESI Legacy Imaging Surveys. I. Cluster Detection”, Astrophysical Journal, Volume 253, Number 2, 2021. Link to paper

Provided by Chinese Academy of Sciences

What Does 1.5 °C Warming Limit Mean for China? (Maths)

As part of the Paris Agreement, nearly all countries agreed to take steps to limit the average increase in global surface temperature to less than 2 °C, or preferably 1.5 °C, compared with preindustrial levels. Since the Agreement was adopted, however, concerns about global warming suggest that countries should aim for the “preferable” warming limit of 1.5 °C.

What are the implications for China of trying to achieve this lower limit?

Prof. DUAN Hongbo from the University of Chinese Academy of Sciences and Prof. WANG Shouyang from the Academy of Mathematics and Systems Science of the Chinese Academy of Sciences, together with their collaborators, have attempted to answer this question.

Their results were published in an article entitled “Assessing China’s efforts to pursue the 1.5°C warming limit,” which was published in Science on April 22 .

The authors used nine different integrated assessment models (IAMs) to make their evaluation of China’s effort to achieve the warming limit of 1.5 °C.

The various models show different emission trajectories for carbon and noncarbon emissions. The majority of the IAMs will achieve near-zero or negative carbon emissions by around 2050, with a range from -0.13 billion tonnes of CO2 (GtCO2) to 2.34 GtCO2 across models. However, one highly consistent finding among all models is that the 1.5°C warming limit requires carbon emissions decrease sharply after 2020.

The researchers discovered that a steep and early drop in carbon emissions reduces dependency on negative emission technologies (NETs), i.e., technologies that capture and sequester carbon. One implication of this finding is that there is a trade-off between substantial early mitigation of carbon emissions and reliance on NETs, which may have uncertain performance. At the same time, the model showing the lowest carbon emissions by 2050 shows the greatest reliance on carbon capture and storage (CCS) technology—suggesting that NETs have an important role in reducing carbon emissions.

Although carbon emissions were an important focus of the study, the researchers also noted that reducing noncarbon emissions is necessary to stay under the warming limit. Specifically, carbon emissions must be reduced by 90%, CH4 emissions by about 71% and N2O emissions by about 52% to achieve the 1.5 °C goal.

The study showed that mitigation challenges differ across sectors, e.g., industry, residential and commercial, transportation, electricity and “other.” Among these sectors, industry plays a big role in end-use energy consumption. Therefore, substantial changes in industrial energy use must occur to reach deep decarbonization of the entire economy and realization of the given climate goals. Indeed, a highly consistent finding across all models is that the largest proportion of emission reduction will come from a substantial decline in energy consumption.

The study also highlights the importance of replacing fossil fuels with renewables, a strategy that plays the next most important role in emission reduction behind reducing energy consumption. The study suggests that China needs to decrease its fossil energy consumption (as measured by standard coal equivalent, or Gtce) by about 74% in 2050 in comparison with the no policy scenario.

The researchers estimate that achieving the 1.5 °C goal will involve a loss of GDP in 2050 in the range of 2.3% to 10.9%, due to decreased energy consumption and other factors.

The study also noted that China’s recently announced plan to become carbon neutral by 2060 largely accords with the 1.5 °C warming limit; however, achieving the latter goal is more challenging.


Assessing China’s efforts to pursue the 1.5°C warming limit

Provided by Chinese Academy of Sciences