Friday, December 02, 2022

Four Perspectives on Neutron Stars, Pulsars, and Magnetars By Kerry Hensley

Illustration of a neutron star emitting a jet.
Credit:
ICRAR/University of Amsterdam

When a massive star explodes as a supernova, its core collapses into a city-sized sphere of neutrons called a neutron star. These extraordinarily dense stars — just one teaspoon of a neutron star would weigh billions of tons in Earth’s gravity — exhibit some of the most intriguing behavior in the universe: rapid rotation, beams of radio emission, and extremely strong magnetic fields. Today, we’ll introduce four recent research articles that explore different aspects of these stars.


Simulated light curves during an X-ray burst, showing the effects of incorporating different physics. A model without neutrino cooling (labeled “No DU” in reference to the neutrino cooling pathway called direct Urca), peaks at a lower luminosity than models incorporating neutrino cooling. Credit: Adapted from Dohi et al. 2022

Bursting, Cooling, and Bursting Again

Sometimes, neutron stars reveal themselves by interacting with other stars. When a neutron star gathers gas from a stellar companion, the gas can ignite on the star’s scorching surface, resulting in a sudden burst of X-rays. After this sudden influx of heat, how does the neutron star cool, and how is the cooling reflected in the star’s light curve? While this may seem like a simple question, the answer hinges on our understanding of the conditions within the neutron star’s interior as well as the characteristics of the gas being accreted.

In a recent publication, a team led by Akira Dohi (土肥明; Kyushu University, Japan) explored the issue of neutron star cooling with general relativistic stellar evolution models. Specifically, the team investigated the effects of cooling by emitting neutrinos — chargeless, nearly massless particles that scarcely interact with matter — which is expected to speed up the cooling rate. The authors found that neutrino cooling increases the time between outbursts but makes them brighter at their peak, though additional physics to be included in future modeling might suppress this effect.

Simulated pulses showing a change in the phase of the pulse due to the shifting motion of the sparks.
Credit: Adapted from Basu et al. 2022


Simulating Pulsar Sparks

Rahul Basu (University of Zielona Góra, Poland) and collaborators reported on simulations of conditions very close to the surface of a neutron star that emits beams of radio emission. Neutron stars that emit beamed radio waves are called pulsars for the way the beams sweep across our field of view, generating what we see as pulses of emission. Near a pulsar’s surface, extremely high temperatures and strong magnetic and electric fields combine forces to summon a sea of charged particles that are then accelerated to relativistic speeds.

Basu and collaborators focused on a phenomenon called sparking, in which charged particles jump the gap between the pulsar’s surface at its poles and its plasma-rich magnetosphere. The team’s modeling demonstrated that a pulsar’s poles are tightly filled with constant sparks, and the arrangement of these sparks slowly shifts over time. By modeling the emission associated with the simulated sparks, the team showed that the shifting motion of the sparks appears to be responsible for the observed periodic variations in the phases and amplitudes of some pulsars’ pulses.

Example of a pulse observed with the Giant Metrewave Radio Telescope.
Credit: Adapted from Sharma et al. 2022


Pulsars Probing Gravitational Waves

By studying large groups of pulsars, astronomers hope to learn about something seemingly unrelated: gravitational waves. Pulsars provide a method to detect gravitational waves by way of these stars’ impeccable timekeeping abilities — because a pulsar’s radio beat is so reliable, the slight distortion of space caused by a passing gravitational wave should impact the arrival times of a pulsar’s pulses.

However, there’s a complication to this technique: spatial and temporal changes in the interstellar medium plasma can also affect when a pulsar’s radio pulses arrive at Earth. In order to compensate for the effect of the interstellar medium, we need to be able to make precise observations of pulsars across a range of radio frequencies. In a recent research article, Shyam Sharma (Tata Institute of Fundamental Research, India) and collaborators tested a pulsar-timing measurement technique using the Giant Metrewave Radio Telescope, which is highly sensitive to low-frequency radio waves. Sharma and coauthors showed that observing using a wide frequency band yields results comparable to typical narrowband observations, indicating that this technique could be used to disentangle the effects of the interstellar medium and more accurately time the pulses of arrays of pulsars, opening a new window onto gravitational waves.

Temperature maps of the top of a magnetar’s crust (top) and the magnetar’s surface (bottom) after a hotspot is injected.
Credit: De Grandis et al. 2022


Magnetic Outbursts

As if neutron stars could get any wilder: some neutron stars, dubbed magnetars, have extremely strong magnetic fields and exhibit frequent X-ray flares. While the cause of these X-ray outbursts is still unknown, some researchers have suggested that they arise from a sudden upwelling of magnetic energy beneath the magnetar’s crust, creating a hot spot that cools gradually over days or months.

To understand how the injection of heat into a magnetar’s crust might create the spectral features seen during X-ray outbursts, Davide De Grandis (University of Padova, Italy) and coauthors employed a three-dimensional magnetothermal model of hotspot formation and cooling. This model allowed the team to study the effects of asymmetrical hot spots under a magnetar’s crust for the first time. The team was able to confirm that these hot spots can be responsible for outbursts, though we’ll have to wait for future research to fully explore the evolution of the spectral features generated during these events.


Citation

“Impacts of the Direct Urca and Superfluidity inside a Neutron Star on Type I X-Ray Bursts and X-Ray Superbursts,” A. Dohi et al 2022 ApJ 937 124. doi:10.3847/1538-4357/ac8dfe

“Two-dimensional Configuration and Temporal Evolution of Spark Discharges in Pulsars,” Rahul Basu et al 2022 ApJ 936 35. doi:10.3847/1538-4357/ac8479

“Wide-band Timing of GMRT-discovered Millisecond Pulsars,” Shyam S. Sharma et al 2022 ApJ 936 86. doi:10.3847/1538-4357/ac86d8

“Three-dimensional Magnetothermal Simulations of Magnetar Outbursts,” Davide De Grandis et al 2022 ApJ 936 99. doi:10.3847/1538-4357/ac8797

Thursday, December 01, 2022

Emission lines from the simulated interstellar medium


Gas density and gas temperature of the simulated ISM at high gas surface densities of 100 M⦿/pc2 (left panels) and the corresponding emission line maps for hydrogen (middle), nitrogen and oxygen ions (right panels).© MPA


This plot shows the velocity dispersion (y-axis) as a function of the star formation rate (x-axis) for the warm-ionized medium (WIM, ~ 10.000 K, orange squares) and the cold neutral medium (CNM, ~ 300K, blue squares). The sound speed of the WIM is indicated by the grey band. The simulations follow the observed trends (Leroy et al. 2008, data points with black boxes) very well. The velocity dispersion increases with star formation rate and the warm gas motions become supersonic. © MPA



This map shows the diagnostic line-ratios (BPT diagram) with galaxies from the SDSS (grey) in the background. While the simulation overall (pink star) is in the star formation regime (left), a look at higher resolution (green-yellow dots) reveals significant emission in the AGN regime (right). The two lines (dotted, Kauffman et al. 2003 and solid, Kewley et al. 2001) are predictions separating galaxies with ionization by stellar radiation from radiation from active galactic nuclei (AGN, i.e. accreting supermassive black holes). In this simulation, however, the emission is generated by diffuse ionized gas heated by supernova shocks and not by AGN radiation. If this radiation were excluded the whole region would move in the direction of the arrow. © MPA




All stars in galaxies form in the dense gas of the interstellar medium (ISM). Ionizing radiation from newly born massive stars and supernova explosions lets the gas shine at characteristic wavelengths of certain atoms and ions. The relative strength of such line fluxes is an important observational diagnostic to reveal the internal state and composition of the ISM. However, emission by diffuse ionized gas has different flux ratios making accurate predictions difficult. Scientist at MPA and their European collaborators have used supercomputers to simulate a realistic star forming interstellar medium and to quantify the contribution of the diffuse gas. This finding allows for a more accurate interpretation of observations also at early cosmic times when these extreme conditions are more common than in the local Universe. 

The interstellar medium (ISM) is the backbone of every galaxy that actively forms stars. Gas accreted from the cosmic web or returned from previous generations of stars accumulates here. Dense regions in the ISM cool and collapse into molecular clouds, the nursery of newly forming stars. Most of these stars have masses like our Sun or lower. However, about one in a hundred is more massive than eight solar masses. These massive stars emit strong ionizing radiation and expel material from their surfaces as stellar winds. At the end of their lives, they die as supernovae, dumping enormous amounts of energy into the ISM. These processes are termed as “feedback” and change the conditions of the ISM resulting in a complex interplay between star formation and the turbulent, multiphase structure of the gas. Modern supercomputer simulations can study this in detail.

Scientists at MPA and collaborators at the Universities of Cologne and Heidelberg, the Czech Academy of Sciences, the Institute d’Astrophysique de Paris, and the École Polytechnique Fédérale de Lausanne of the SILCC (Simulating the Life Cycle of molecular Clouds) supercomputing project have used SuperMUC-NG at the Leibnitz Supercomputing Center, one of the world’s fastest supercomputers, to simulate a realistic star forming ISM with all fundamental constituents. This includes gas, stars, radiation, and dust, but also the non-thermal components magnetic fields and cosmic-rays. The complex interaction of the ISM with stellar feedback processes has been simulated with conditions prevailing in a typical spiral galaxy in the local Universe, similar to the solar neighborhood. In addition, models with higher gas density represent more extreme conditions in the local Universe, like in interacting galaxies, or galaxies at earlier cosmic epochs with higher gas fractions.

The simulations are very realistic and explain many details seen in observations. Their multi-phase gas structure, star formation properties, and kinematic properties agree very well with direct ISM observations. In regions with higher star formation rates, the supernova explosions trigger higher turbulent velocities in the cold (< 300 Kelvin) and warm (~ 10000 Kelvin) gas with a similar trend as observed. At high star formation rates, the warm ISM motions become supersonic and magneto-hydrodynamic shocks become ubiquitous.

The ISM is mainly composed of hydrogen and helium but is also enriched with traces of heavier elements such as oxygen or nitrogen. When these elements are ionized and excited by stellar radiation, they start emitting at specific wavelengths when they return to lower energy levels. Some of these transitions, like the [OIII] emission of doubly ionized oxygen, happens in extremely rarefied gas which only exist in space, typically in so-called HII regions around massive stars. It is therefore sometimes referred to as a “forbidden” line. The relative strength of this line emission is an important observational diagnostic to reveal the internal state and composition of the ISM at all cosmic epochs.

For example, the flux ratios of emission lines are used to characterize e.g. the density of the ISM, abundances of heavy elements, or the source of the ionizing radiation. However, also in regions without massive stars and their ionizing radiation, shocks can heat up the gas leading to collisional ionization of the same elements. This diffuse ionized gas (DIG) has very different flux ratios than the gas ionized by stellar radiation in HII regions. The uncertain contribution of the DIG in observations makes accurate predictions about the ISM structure difficult.

The research team has used simulations of a large region of the ISM to construct detailed maps for the expected emission in hydrogen, oxygen and nitrogen lines. The whole region has flux ratio properties similar to the ISM of star forming galaxies in the local Universe. However, a much higher resolution reveals the contribution of the DIG. In the line-ratio diagram (known as the BPT diagram) it populates a region, which is traditionally associated with the presence of an active galactic nucleus. In this case, however, the ionized gas with a temperature of ~ 20.000 Kelvin is created by supersonic turbulence in the warm ionized gas (WIM) triggered by many supernova explosions.

Simulations and data analysis were carried out on supercomputers at MPCDF and SuperMUC-NG at the Leibnitz Supercomputing Center (LRZ).

This work is supported by MPCDF and Gauss Centre for Supercomputing

More Information: The SILCC project



Authors

Thorsten Naab
Scientific Staff
tel.2295

tnaab@mpa-garching.mpg.de

Tim-Eric Rathjen

Original publications:

1.
Rahtjen, T.-E., Naab. T. et al.
SILCC VII - Gas kinematics and multiphase outflows of the simulated
ISM at high gas surface densities
submitted to MNRAS
Source

2.
Rahtjen, T.-E., Naab, T. et al.
Optical emission lines from the simulated interstellar medium in prep



Wednesday, November 30, 2022

Most distant detection of a black hole swallowing a star

Artist’s impression of a black hole swallowing a star



Videos

Animation of a black hole swallowing a star  
Animation of a black hole swallowing a star



Earlier this year, the European Southern Observatory’s Very Large Telescope (ESO’s VLT) was alerted after an unusual source of visible light had been detected by a survey telescope. The VLT, together with other telescopes, was swiftly repositioned towards the source: a supermassive black hole in a distant galaxy that had devoured a star, expelling the leftovers in a jet. The VLT determined it to be the furthest example of such an event to have ever been observed. Because the jet is pointing almost towards us, this is also the first time it has been discovered with visible light, providing a new way of detecting these extreme events.

Stars that wander too close to a black hole are ripped apart by the incredible tidal forces of the black hole in what is known as a tidal disruption event (TDE). Approximately 1% of these cause jets of plasma and radiation to be ejected from the poles of the rotating black hole. In 1971, the black hole pioneer John Wheeler [1] introduced the concept of jetted-TDEs as “a tube of toothpaste gripped tight about its middle,” causing the system to “squirt matter out of both ends.

We have only seen a handful of these jetted-TDEs and they remain very exotic and poorly understood events,” says Nial Tanvir from the University of Leicester in the UK, who led the observations to determine the object’s distance with the VLT. Astronomers are thus constantly hunting for these extreme events to understand how the jets are actually created and why such a small fraction of TDEs produce them.

As part of this quest many telescopes, including the Zwicky Transient Facility (ZTF) in the US, repeatedly survey the sky for signs of short-lived, often extreme, events that could then be studied in much greater detail by telescopes such as ESO’s VLT in Chile. “We developed an open-source data pipeline to store and mine important information from the ZTF survey and alert us about atypical events in real time,” explains Igor Andreoni, an astronomer at the University of Maryland in the US who co-led the paper published today in Nature together with Michael Coughlin from the University of Minnesota.

In February of this year the ZTF detected a new source of visible light. The event, named AT2022cmc, was reminiscent of a gamma ray burst — the most powerful source of light in the Universe. The prospect of witnessing this rare phenomenon prompted astronomers to trigger several telescopes from across the globe to observe the mystery source in more detail. This included ESO’s VLT, which quickly observed this new event with the X-shooter instrument. The VLT data placed the source at an unprecedented distance for these events: the light produced from AT2022cmc began its journey when the universe was about one third of its current age.

A wide variety of light, from high energy gamma rays to radio waves, was collected by 21 telescopes around the world. The team compared these data with different kinds of known events, from collapsing stars to kilonovae. But the only scenario that matched the data was a rare jetted-TDE pointing towards us. Giorgos Leloudas, an astronomer at DTU Space in Denmark and co-author of this study, explains that "because the relativistic jet is pointing at us, it makes the event much brighter than it would otherwise appear, and visible over a broader span of the electromagnetic spectrum."

The VLT distance measurement found AT2022cmc to be the most distant TDE to have ever been discovered, but this is not the only record-breaking aspect of this object. “Until now, the small number of jetted-TDEs that are known were initially detected using high energy gamma-ray and X-ray telescopes, but this was the first discovery of one during an optical survey,” says Daniel Perley, an astronomer at Liverpool John Moores University in the UK and co-author of the study. This demonstrates a new way of detecting jetted-TDEs, allowing further study of these rare events and probing of the extreme environments surrounding black holes.




More information

This research was presented in a paper titled “A very luminous jet from the disruption of a star by a massive black hole” to appear in Nature (doi: 10.1038/s41586-022-05465-8)

The team is composed of Igor Andreoni (Joint Space-Science Institute, University of Maryland, USA [JSI/UMD]; Department of Astronomy, University of Maryland, USA [UMD]; Astrophysics Science Division, NASA Goddard Space Flight Center [NASA/GSFC], USA), Michael W. Coughlin (School of Physics and Astronomy, University of Minnesota, USA), Daniel A. Perley (Astrophysics Research Institute, Liverpool John Moores University, UK), Yuhan Yao (Division of Physics, Mathematics and Astronomy, California Institute of Technology, USA [Caltech]), Wenbin Lu (Department of Astrophysical Sciences, Princeton University, USA), S. Bradley Cenko (JSI/UMD; NASA/GSFC), Harsh Kumar (Indian Institute of Technology Bombay, India [IIT/Bombay]), Shreya Anand (Caltech), Anna Y. Q. Ho (Department of Astronomy, University of California, Berkeley, USA [UCB]; Lawrence Berkeley National Laboratory, USA [LBNL]; Miller Institute for Basic Research in Science, USA), Mansi M. Kasliwal (Caltech), Antonio de Ugarte Postigo (Université Côte d’Azur, Observatoire de la Côte d’Azur, France), Ana Sagués-Carracedo (The Oskar Klein Centre, Stockholm University, Sweden [OKC]), Steve Schulze (OKC), D. Alexander Kann (Instituto de Astrofisica de Andalucia, Glorieta de la Astronomia, Spain [IAA-CSIC]), S. R. Kulkarni (Caltech), Jesper Sollerman (OKC), Nial Tanvir (Department of Physics and Astronomy, University of Leicester, UK), Armin Rest (Space Telescope Science Institute, Baltimore, USA [STScI]; Department of Physics and Astronomy, The Johns Hopkins University, USA), Luca Izzo (DARK, Niels Bohr Institute, University of Copenhagen, Denmark), Jean J. Somalwar (Caltech), David L. Kaplan (Center for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin–Milwaukee, USA), Tomás Ahumada (UMD), G. C. Anupama (Indian Institute of Astrophysics, Bangalore, India [IIA]), Katie Auchettl (School of Physics, University of Melbourne, Australia; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions; Department of Astronomy and Astrophysics, University of California, Santa Cruz, USA), Sudhanshu Barway (IIA), Eric C. Bellm (DIRAC Institute, University of Washington, USA), Varun Bhalerao (IIT/Bombay), Joshua S. Bloom (LBNL; UCB), Michael Bremer (Institut de Radioastronomie Millimetrique, France [IRAM]), Mattia Bulla (OKC), Eric Burns (Department of Physics & Astronomy, Louisiana State University, USA), Sergio Campana (INAF-Osservatorio Astronomico di Brera, Italy), Poonam Chandra (National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University, India), Panos Charalampopoulos (DTU Space, National Space Institute, Technical University of Denmark, Denmark [DTU]), Jeff Cooke (Australian Research Council Centre of Excellence for Gravitational Wave Discovery, Swinburne University of Technology, Hawthorn, Australia [OzGrav]; Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Australia [CAS]), Valerio D’Elia (Space Science Data Center - Agenzia Spaziale Italiana, Italy), Kaustav Kashyap Das (Caltech), Dougal Dobie (OzGrav; CAS), Jose Feliciano Agüí Fernández (IAA-CSIC), James Freeburn (OzGrav; CAS), Cristoffer Fremling (Caltech), Suvi Gezari (STScI), Matthew Graham (Caltech), Erica Hammerstein (UMD), Viraj R. Karambelkar (Caltech), Charles D. Kilpatrick (Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, USA), Erik C. Kool (OKC), Melanie Krips (IRAM), Russ R. Laher (IPAC, California Institute of Technology, USA [IPAC]), Giorgos Leloudas (DTU), Andrew Levan (Department of Astrophysics, Radboud University, The Netherlands), Michael J. Lundquist (W. M. Keck Observatory, USA), Ashish A. Mahabal (Caltech; Center for Data Driven Discovery, California Institute of Technology, USA), Michael S. Medford (UCB; LBNL), M. Coleman Miller (JSI/UMD; UMD), Anais Möller (OzGrav; CAS), Kunal Mooley (Caltech), A. J. Nayana (Indian Institute of Astrophysics, India), Guy Nir (UCB), Peter T. H. Pang (Nikhef, The Netherlands; Institute for Gravitational and Subatomic Physics, Utrecht University, The Netherlands), Emmy Paraskeva (IAASARS, National Observatory of Athens, Greece; Department of Astrophysics, Astronomy & Mechanics, University of Athens, Greece; Nordic Optical Telescope, Spain; Department of Physics and Astronomy, Aarhus University, Denmark), Richard A. Perley (National Radio Astronomy Observatory, USA), Glen Petitpas (Center for Astrophysics | Harvard & Smithsonian, Cambridge, USA), Miika Pursiainen (DTU), Vikram Ravi (Caltech), Ryan Ridden-Harper (School of Physical and Chemical Sciences — Te Kura Matu, University of Canterbury, New Zealand), Reed Riddle (Caltech Optical Observatories, California Institute of Technology, USA), Mickael Rigault (Université de Lyon, France), Antonio C. Rodriguez (Caltech), Ben Rusholme (IPAC), Yashvi Sharma (Caltech), I. A. Smith (Institute for Astronomy, University of Hawaii, USA), Robert D. Stein (Caltech), Christina Thöne (Astronomical Institute of the Czech Academy of Sciences, Czech Republic), Aaron Tohuvavohu (Department of Astronomy and Astrophysics, University of Toronto, Canada), Frank Valdes (National Optical Astronomy Observatory, USA), Jan van Roestel (Caltech), Susanna D. Vergani (GEPI, Observatoire de Paris, PSL Research University, France; Institut d’Astrophysique de Paris, France), Qinan Wang (STScI), Jielai Zhang (OzGrav; CAS).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration in astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates APEX and ALMA on Chajnantor, two facilities that observe the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.




Links



Contacts

Igor Andreoni
Joint Space-Science Institute, University of Maryland, NASA Goddard Space Flight Center
Greenbelt, MD, USA
Tel: +1 (626) 487-7545
Email:
andreoni@umd.edu

Daniel Perley
Astrophysics Research Institute, Liverpool John Moores University
Liverpool, UK
Tel: +44 (0)745 6339330
Email:
d.a.perley@ljmu.ac.uk

Nial Tanvir
Department of Physics and Astronomy, University of Leicester
Leicester, UK
Email:
nrt3@leicester.ac.uk

Giorgos Leloudas
DTU Space, National Space Institute, Technical University of Denmark
Lyngby, Denmark
Email:
giorgos@space.dtu.dk

Juan Carlos Muñoz Mateos
ESO Media Officer
Garching bei München, Germany
Tel: +49 89 3200 6176
Email:
press@eso.org

Source: ESO/News



Tuesday, November 29, 2022

Revisiting a Celestial Fireworks Display

Image description: A supernova remnant, in the shape of a flame, occupies the centre and top. It is made of many long strands and thin layers of gas, that brightly glow orange and blue. Faint gas clouds outline its edges. It is surrounded by several scattered blue and red stars, and the background is black and filled with small red stars. Credit: ESA/Hubble & NASA, S. Kulkarni, Y. Chu

Shreds of the luridly coloured supernova remnant DEM L 190 seem to billow across the screen in this image from the NASA/ESA Hubble Space Telescope. The delicate sheets and intricate filaments are debris from the cataclysmic death of a massive star that once lived in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way. DEM L 190 — also known as LMC N49 — is the brightest supernova remnant in the Large Magellanic Cloud and lies approximately 160 000 light-years away from Earth in the constellation Dorado.

This striking image was created with data from two different astronomical investigations, using one of Hubble’s retired instruments, the Wide Field Planetary Camera 2 (WFPC2). This instrument has since been replaced by the more powerful Wide Field Camera 3, but during its operational lifetime it contributed to cutting-edge science and produced a series of stunning public outreach images. The first of the two WFPC2 investigations used DEM L 190 as a natural laboratory in which to study the interaction of supernova remnants and the interstellar medium, the tenuous mixture of gas and dust that lies between stars. In the second project, astronomers turned to Hubble to pinpoint the origin of a Soft Gamma-ray Repeater, an enigmatic object lurking in DEM L 190 which repeatedly emits high-energy bursts of gamma rays.

This is not the first image of DEM L 190 to be released to the public — a previous Hubble portrait of this supernova remnant was published in 2003. This new image incorporates additional data and improved image processing techniques, making this spectacular celestial fireworks display even more striking!

Links



Monday, November 28, 2022

NASA’s Webb Reveals an Exoplanet Atmosphere as Never Seen Before

Exoplanet WASP-39 b and its Star (Illustration)
Credits: Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI)


Exoplanet WASP-39 b (Transmission Spectra)
Credits: Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI)




NASA’s James Webb Space Telescope just scored another first: a molecular and chemical profile of a distant world’s skies.

While Webb and other space telescopes, including NASA's Hubble and Spitzer, previously have revealed isolated ingredients of this broiling planet’s atmosphere, the new readings from Webb provide a full menu of atoms, molecules, and even signs of active chemistry and clouds.

The latest data also give a hint of how these clouds might look up close: broken up rather than a single, uniform blanket over the planet.

The telescope’s array of highly sensitive instruments was trained on the atmosphere of WASP-39 b, a “hot Saturn” (a planet about as massive as Saturn but in an orbit tighter than Mercury) orbiting a star some 700 light-years away. 

The findings bode well for the capability of Webb’s instruments to conduct the broad range of investigations of all types of exoplanets – planets around other stars – hoped for by the science community. That includes probing the atmospheres of smaller, rocky planets like those in the TRAPPIST-1 system.

“We observed the exoplanet with multiple instruments that, together, provide a broad swath of the infrared spectrum and a panoply of chemical fingerprints inaccessible until [this mission],” said Natalie Batalha, an astronomer at the University of California, Santa Cruz, who contributed to and helped coordinate the new research. “Data like these are a game changer.”

The suite of discoveries is detailed in a set of five new scientific papers, three of which are in press and two of which are under review. Among the unprecedented revelations is the first detection in an exoplanet atmosphere of sulfur dioxide (SO2), a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is created in a similar way.

“This is the first time we see concrete evidence of photochemistry – chemical reactions initiated by energetic stellar light – on exoplanets,” said Shang-Min Tsai, a researcher at the University of Oxford in the United Kingdom and lead author of the paper explaining the origin of sulfur dioxide in WASP-39 b’s atmosphere. “I see this as a really promising outlook for advancing our understanding of exoplanet atmospheres with [this mission].” 

This led to another first: scientists applying computer models of photochemistry to data that requires such physics to be fully explained. The resulting improvements in modeling will help build the technological know-how to interpret potential signs of habitability in the future.

“Planets are sculpted and transformed by orbiting within the radiation bath of the host star,” Batalha said. “On Earth, those transformations allow life to thrive.”

The planet’s proximity to its host star – eight times closer than Mercury is to our Sun – also makes it a laboratory for studying the effects of radiation from host stars on exoplanets. Better knowledge of the star-planet connection should bring a deeper understanding of how these processes affect the diversity of planets observed in the galaxy.

To see light from WASP-39 b, Webb tracked the planet as it passed in front of its star, allowing some of the star’s light to filter through the planet’s atmosphere. Different types of chemicals in the atmosphere absorb different colors of the starlight spectrum, so the colors that are missing tell astronomers which molecules are present. By viewing the universe in infrared light, Webb can pick up chemical fingerprints that can’t be detected in visible light.

Other atmospheric constituents detected by the Webb telescope include sodium (Na), potassium (K), and water vapor (H2O), confirming previous space- and ground-based telescope observations as well as finding additional fingerprints of water, at these longer wavelengths, that haven’t been seen before.

Webb also saw carbon dioxide (CO2) at higher resolution, providing twice as much data as reported from its previous observations. Meanwhile, carbon monoxide (CO) was detected, but obvious signatures of both methane (CH4) and hydrogen sulfide (H2S) were absent from the Webb data. If present, these molecules occur at very low levels.

To capture this broad spectrum of WASP-39 b’s atmosphere, an international team numbering in the hundreds independently analyzed data from four of the Webb telescope’s finely calibrated instrument modes.

"We had predicted what [the telescope] would show us, but it was more precise, more diverse, and more beautiful than I actually believed it would be,” said Hannah Wakeford, an astrophysicist at the University of Bristol in the United Kingdom who investigates exoplanet atmospheres.

Having such a complete roster of chemical ingredients in an exoplanet atmosphere also gives scientists a glimpse of the abundance of different elements in relation to each other, such as carbon-to-oxygen or potassium-to-oxygen ratios. That, in turn, provides insight into how this planet – and perhaps others – formed out of the disk of gas and dust surrounding the parent star in its younger years. 

WASP-39 b’s chemical inventory suggests a history of smashups and mergers of smaller bodies called planetesimals to create an eventual goliath of a planet.

“The abundance of sulfur [relative to] hydrogen indicated that the planet presumably experienced significant accretion of planetesimals that can deliver [these ingredients] to the atmosphere,” said Kazumasa Ohno, a UC Santa Cruz exoplanet researcher who worked on Webb data. “The data also indicates that the oxygen is a lot more abundant than the carbon in the atmosphere. This potentially indicates that WASP-39 b originally formed far away from the central star.”  In so precisely parsing an exoplanet atmosphere, the Webb telescope’s instruments performed well beyond scientists’ expectations – and promise a new phase of exploration among the broad variety of exoplanets in the galaxy.

“We are going to be able to see the big picture of exoplanet atmospheres,” said Laura Flagg, a researcher at Cornell University and a member of the international team. “It is incredibly exciting to know that everything is going to be rewritten. That is one of the best parts of being a scientist.”

The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).



About This Release: Credits:

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Friday, November 25, 2022

Tracing the Origins of Rare, Cosmic Explosions

A typical star-forming host galaxy where a short gamma-ray burst originated from.
Credit: W. M. Keck Observatory/Adam Makarenko



Astronomers Produce the Most Robust Catalog to Date of Short Gamma-Ray Burst Hosts


Maunakea, Hawaiʻi A team of astronomers led by Northwestern University has created the most extensive inventory yet of the galaxies where short gamma-ray bursts (sGRBs) come from. Using several highly sensitive instruments at W. M. Keck Observatory on Maunakea, Hawaiʻi and other large observatories, combined with some of the most sophisticated galaxy modeling ever used in the field, the researchers pinpointed the galactic homes of 84 sGRBs.

“This is the largest catalog of sGRB host galaxies to ever exist, so we expect it to be the gold standard for many years to come,” said Anya Nugent, an astronomy graduate student at Northwestern University who led the research, observational efforts with Keck Observatory, and one of two publications about the study.

As an homage to the fact that sGRBs are among the brightest explosions in the universe, the team calls their catalog BRIGHT (Broadband Repository for Investigating Gamma-ray burst Host Traits) with all of their data and modeling products online for community use.

SGRBs are momentary flashes of intense gamma-ray light emitted when two neutron stars collide. While the gamma-rays last only seconds, the optical light can continue for hours before fading below detection, called an afterglow. SGRBs are some of the most luminous explosions in the universe with, at most, a dozen detected and pinpointed each year.




An artistic rendition of the diversity of short gamma-ray burst (sGRB) host environments, in large part discovered and characterized by Keck Observatory. SGRBs may occur in actively star-forming or dead galaxies, nearby or deep into the universe, and close or far from their host’s centers. All data is publicly available on the BRIGHT website (bright.ciera.northwestern.edu). Credit: W. M. Keck Observatory/Adam Makarenko


Since the discovery of sGRB afterglows in 2005 by NASA’s Neil Gehrels Swift Observatory, astronomers have spent the last 17 years trying to find out which galaxies these powerful bursts originated from, as the stars within a galaxy can give insight into the environmental conditions needed to produce these events and can connect them to their neutron star merger origins. Indeed, only one sGRB, GRB 170817A, has a confirmed neutron star merger origin, as it was detected just seconds after gravitational wave detectors observed the binary neutron star merger, GW170817.

“In a decade, the next generation of gravitational wave observatories will be able to detect neutron star mergers out to the same distances as we do sGRBs today. Thus, our catalog will serve as a benchmark for comparison to future detections of neutron star mergers,” said Wen-fai Fong, assistant professor of astronomy and physics at Northwestern University and lead author of one of the publications.

“Building this catalog and finally having enough host galaxies to see patterns and draw significant conclusions is exactly what the field needed to push our understanding of these fantastic events and what happens to stars after they die,” said Nugent.

Learning about sGRB host galaxies is crucial to understanding the blasts themselves and offers clues about the types of stars that created them as well as their distance from Earth. Since neutron star mergers create heavy elements like gold and platinum, the data will also deepen scientists’ understanding of when precious metals were first created in the universe.

The first paper in the study, which is published in The Astrophysical Journal, found that sGRBs occur at higher redshifts, or earlier times in the universe, than previously thought—and with greater distances from their hosts’ centers than understood before. Surprisingly, several of these explosions were found just outside their host galaxies as if they were “kicked out,” raising questions as to how they were able to travel that far.

Published in the same journal, the second research paper in the study probed the characteristics of 69 of the identified sGRB host galaxies. The findings suggest about 85 percent of them are young, actively star-forming galaxies — a stark contrast to earlier studies that characterized the population of sGRB host galaxies as relatively old and approaching death. This means neutron star systems may form in a broad range of environments and many of them have quick formation-to-merger timescales.

Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS), DEep Imaging and Multi-Object Spectrograph (DEIMOS), and Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) were crucial instruments in creating the catalog. Together, they allowed the team to capture deep imaging and spectroscopy of some of the faintest galaxies identified in the survey of sGRB hosts.

“It would simply not be possible to obtain distances to some of these galaxies, or even detect them at all, without the Keck Observatory,” Fong said. “In many cases, Keck enabled the first detection of a very faint host galaxy and ensured we did not misidentify any host galaxies.”

Many questions remain about how neutron stars merge and how long the process takes. But observing sGRBs and their host galaxies provides one of the best perspectives to answer them and can offer more data about neutron star mergers and their hosts at much farther distances, and more frequently, than current gravitational wave detectors. This new sGRB host catalog will therefore serve as a vital reference point in the coming decade to understand the full evolution of these systems over cosmic time. “The catalog can really make impacts beyond just a single class of transients like sGRBs,” said co-author Yuxin “Vic” Dong, an astronomy PhD student at Northwestern University. “With the wealth of data and results presented in the catalog, I believe a variety of research projects will make use of it, maybe even in ways we have yet not thought of.”

“I started observations for this project 10 years ago and it was so gratifying to be able to pass the torch onto the next generation of researchers,” said Fong. “It is one of my career’s greatest joys to see years of work come to life in this catalog, thanks to the young researchers who really took this study to the next level.”

The James Webb Space Telescope (JWST) is poised to further advance our understanding of neutron star mergers and how far back in time they began, as it will be able to detect the faintest host galaxies that exist at very early times in the universe.
 
“I’m most excited about the possibility of using JWST to probe deeper into the source of these rare, explosive events,” said Nugent. “JWST’s ability to observe faint galaxies in the universe could uncover more sGRB host galaxies that are currently evading detection, perhaps even revealing a missing population and a link to the early universe!”





About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then, it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion.

About DEIMOS

The DEep Imaging and Multi-Object Spectrograph (DEIMOS) boasts the largest field of view (16.7arcmin by 5 arcmin) of any of the Keck Observatory instruments, and the largest number of pixels (64 Mpix). It is used primarily in its multi-object mode, obtaining simultaneous spectra of up to 130 galaxies or stars. Astronomers study fields of distant galaxies with DEIMOS, efficiently probing the most distant corners of the universe with high sensitivity.

About MOSFIRE

The Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), gathers thousands of spectra from objects spanning a variety of distances, environments and physical conditions. What makes this large, vacuum-cryogenic instrument unique is its ability to select up to 46 individual objects in the field of view and then record the infrared spectrum of all 46 objects simultaneously. When a new field is selected, a robotic mechanism inside the vacuum chamber reconfigures the distribution of tiny slits in the focal plane in under six minutes. Eight years in the making with First Light in 2012, MOSFIRE’s early performance results range from the discovery of ultra-cool, nearby substellar mass objects, to the detection of oxygen in young galaxies only two billion years after the Big Bang. MOSFIRE was made possible by funding provided by the National Science Foundation.  
 
About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.


Thursday, November 24, 2022

Planets May Have More Time to Form Than Previously Thought

Artist's impression of a young planetary system.
Credit: NASA

A recent study suggests that protoplanetary disks may tend to linger longer than we thought, meaning that planets likely have at least 5 million years to form before their building materials vanish.

One way that protoplanetary disks are dispersed is by radiation and winds from massive stars, as shown in this illustration. 

Disk Dispersal Deadlines
 
Planets arise from gaseous disks called protoplanetary disks. While the details of planet formation are hidden from view within these dusty disks, the big picture is clear: the timeline for planet formation is set by the lifetime of the disk — once the disk disperses, planet formation must come to a halt. Determining how long planets have to form should be a simple task, then: researchers can measure the ages of star clusters and determine whether the stars in those clusters have disks, thus establishing a cutoff point at which disks typically disperse.

In reality, however, this technique has produced a wide range of estimates for the lifetimes of protoplanetary disks, and thus widely varying constraints on how long planets have to form — and the shortest estimates, in the 1.0–3.5 million year range, set a tight deadline for models of planet formation to meet.


Fraction of stars with disks as a function of cluster age and distance. More distant clusters tend to have smaller disk fractions. Credit: Adapted fromPfalzner et al. 2022

Young, Massive, and Misleading?

In a recent publication, a team led by Susanne Pfalzner (Jülich Supercomputing Center and Max Planck Institute for Radio Astronomy, Germany) suggested that careful application of existing techniques can provide a little more wiggle room for modelers, lengthening the typical lifetime of a protoplanetary disk. Researchers often study disks around stars in clusters, since it’s more straightforward to determine their ages than stars outside of clusters. However, it’s easier to identify young, compact clusters than it is to find old, dispersed clusters, especially at large distances from Earth. Since bright, massive stars are easier to detect at large distances, studies biased toward younger clusters are also biased toward more massive stars — which are known to have shorter-lived disks.

As a demonstration of this effect, Pfalzner and coauthors examined how the results of previous studies varied with the properties of the clusters in each study’s sample. They found that samples containing mostly distant (>650 light-years away), young clusters resulted in short estimates for disk lifetimes, while samples containing nearby, old clusters were linked to long disk lifetimes.

The effect of stellar mass and initial disk fraction (IDF) on the median disk lifetime in star clusters.
Credit: Adapted from
Pfalzner et al. 2022

Modelers Everywhere Breathe a Sigh of Relief

To counteract this issue, the team constructed a new sample that is evenly balanced between young and old clusters that are located within 650 light-years of Earth. Analysis of this sample suggested a median disk lifetime of 6.5 million years, with a substantial fraction of disks enduring for 10–20 million years — meaning that in many star systems, planets have far longer to form than expected.

While this result provides much-needed leeway for our models of planet formation, there are still plenty of open questions to explore. For example, it’s important to pin down the fraction of stars that are born with disks; assuming that all stars are initially shrouded in disks implies typical disk lifetimes in the 5–6 million year range, while allowing for a small fraction of stars to be born diskless would allow planets 8–10 million years to form around low-mass stars and 4–5 million years to form around high-mass stars. Regardless of the exact timeframe, understanding how high-mass stars form planets under stricter timescales than low-mass stars will remain a challenging question to answer.

Citation

“Most Planets Might Have More than 5 Myr of Time to Form,” Susanne Pfalzner et al 2022 ApJL 939 L10.
doi:10.3847/2041-8213/ac9839

By Kerry Hensley



Wednesday, November 23, 2022

'Listen' to the Light Echoes From a Black Hole Quick Look: 'Listen' to the Light Echoes From a Black Hole

V404 Cygni

Credit X-ray: Chandra: NASA/CXC/U.Wisc-Madison/S. Heinz et al.; Swift: NASA/Swift/Univ. of Leicester/A. Beardmore; Optical: DSS; Sonification: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

A Quick Look at V404 Cygni - More Animations



One of the surprising features of black holes is that although light (such as radio, visible, and X-rays) cannot escape from them, surrounding material can produce intense bursts of electromagnetic radiation. As they travel outward, these blasts of light can bounce off clouds of gas and dust in space, similar to how light beams from a car’s headlight will scatter off fog.

A new sonification turns these “light echoes” from the black hole called V404 Cygni into sound. Located about 7,800 light-years from Earth, V404 Cygni is a system that contains a black hole, with a mass between five and 10 times the Sun’s, that is pulling material from a companion star in orbit around it. The material is funneled into a disk that encircles the stellar-mass black hole.

This material periodically generates bursts of radiation, including X-rays. As the X-rays travel outward they encounter clouds of gas and dust in between V404 Cygni and Earth and are scattered at various angles. NASA’s Chandra X-ray Observatory and Neil Gehrels Swift Observatory have imaged the X-ray light echoes around V404 Cygni. Because astronomers know exactly how fast light travels and have determined an accurate distance to this system, they can calculate when these eruptions occurred. This data, plus other information, helps astronomers learn more about the dust clouds, including their composition and distances.

Illustration showing how the rings seen by Chandra were produced
Credit: Univ. of Wisconsin-Madison/S.Heinz

The sonification of V404 Cygni translates the X-ray data from both Chandra and Swift into sound. During the sonification, the cursor moves outward from the center of the image in a circle. As it passes through the light echoes detected in X-rays (seen as concentric rings in blue by Chandra and red by Swift in the image), there are tick-like sounds and changes in volume to denote the detection of X-rays and the variations in brightness. To differentiate between the data from the two telescopes, Chandra data is represented by higher-frequency tones while the Swift data is lower. In addition to the X-rays, the image includes optical data from the Digitized Sky Survey that shows background stars. Each star in optical light triggers a musical note. The volume and pitch of the note are determined by the brightness of the star.

More sonifications of astronomical data, as well as additional information on the process, can be found at the "A Universe of Sound" website:https://chandra.si.edu/sound/

These sonifications were led by the Chandra X-ray Center (CXC) and included as part of NASA's Universe of Learning (UoL) program. The collaboration was driven by visualization scientist Kimberly Arcand (CXC), astrophysicist Matt Russo, and musician Andrew Santaguida (both of the SYSTEM Sounds project). NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science from Cambridge Massachusetts and flight operations from Burlington, Massachusetts. NASA's Universe of Learning materials are based upon work supported by NASA under cooperative agreement award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.





Fast Facts for V404 Cygni:

About the Sound:

  • This is an inside-out scan of the light echo rings formed by dust scattering and the background stars.
  • Dust scattering rings
  • The sound is generated by a series of tick-like sounds. The volume and density of ticks is controlled by the ring brightness.
  • Listening to the pattern of rings in this way traces the density of dust clouds that the light has scattered off of on its way towards Earth.
  • The sound generated by the Swift X-ray data is represented as lower frequencies.
  • The Chandra X-ray data represents higher frequency light and its corresponding sound is limited to higher frequencies.
  • Background stars (DSS Optical data)
  • Each visible light star triggers a musical note. The volume and pitch of the note are determined by the brightness of the star. Brighter stars are louder and higher pitched.
Scale: Image is about 35 arcmin (80 light-years) across.
Category:
Black Holes
Coordinates (J2000): RA 20h 24m 03s | Dec +33° 52´ 02"
Constellation:
Cygnus
Observation Date: 2 observations: July 13th and 29th, 2015
Observation Time: 18 hours 51 minutes
Obs. ID: 17701, 17704
Instrument:
ACIS
References: Heinz, S., et al., ApJ, 2016, 825, 15; arXiv:1605.01648
Color Code: X-ray: Chandra: blue & teal, Swift: red, green, blue; Optical: red, green blue
Distance Estimate: About 7,800 light-years



Tuesday, November 22, 2022

Astronomers Observed the Innermost Structure of a Quasar Jet


The left image shows the deepest look yet into the plasma jet of the quasar 3C 273, which will allow scientists to further study how quasar jets are collimated, or narrowed. The powerful, collimated jet extends for hundreds of thousands of light-years beyond the host galaxy, as seen in the right panel image taken by the Hubble Space Telescope. Scientists use radio images at different scales to measure the shape of the entire jet. The arrays used are the Global Millimeter VLBI Array (GMVA) joined by the Atacama Large Millimeter/submillimeter Array (ALMA) and the High Sensitivity Array (HSA). Credits: Hiroki Okino and Kazunori Akiyama; GMVA+ALMA and HSA images: Okino et al.; HST Image: ESA/Hubble & NASA.


The radio telescopes of the Global Millimeter VLBI Array (GMVA) and ALMA, combined into a powerful global array called GMVA+ALMA, which was used in this project. Credit: Kazunori Akiyama



The blue points are the telescopes of the Global Millimeter VLBI Array (GMVA) joined by ALMA. The yellow points are the telescopes of the High Sensitivity Array used in this project. Green indicates where both networks were used. Credit: Kazunori Akiyama




At the heart of nearly every galaxy lurks a supermassive black hole. But not all supermassive black holes are alike: there are many types. Quasars, quasi-stellar objects, are one of the brightest and most active types of supermassive black holes.

An international group of scientists has published new observations of the first quasar ever identified — the one labeled 3C 273, located in the Virgo constellation – that show the innermost, most profound parts of the quasar’s main plasma jet.

Active supermassive black holes emit narrow, mighty jets of plasma that escape at nearly the speed of light. These jets have been studied throughout the modern era of astronomy, yet their formation process is still a mystery to astronomers and astrophysicists. An unresolved issue has been how and where the jets are collimated or concentrated into a narrow beam, which allows them to extend to extreme distances beyond their host galaxy and even affect galactic evolution. These new observations are thus far the deepest into the heart of a black hole, where the plasma flow is collimated into a narrow beam.

This new study, published in The Astrophysical Journal (Okino et al., 2022), includes observations of the 3C 273 jet at the highest angular resolution to date, obtaining data for the innermost portion of the jet, close to the central black hole. The ground-breaking work was made possible by using a closely coordinated set of radio antennas around the globe, a combination of the Global Millimeter VLBI Array (GMVA) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Coordinated observations were also made with the High Sensitivity Array (HSA) to study 3C 273 on different scales and measure the jet’s global shape.

“3C 273 has been studied for decades as the ideal closest laboratory for quasar jets,” says Hiroki Okino, lead author of this paper and a Ph.D. student at the University of Tokyo and the National Astronomical Observatory of Japan. “However, even though the quasar is a close neighbor, until recently, we didn’t have an eye sharp enough to see where this powerful narrow flow of plasma is shaped.”

The image of the 3C 273 jet gives scientists the very first view of the innermost part of the jet in a quasar, where the collimation or narrowing of the beam occurs. The team further found that the angle of the plasma stream flowing from the black hole is tightened up over a very long distance. This narrowing part of the jet continues incredibly far, well beyond the area where the black hole’s gravity rules.

“It is striking to see that the shape of the powerful stream is slowly formed over a long distance in an extremely active quasar. This has also been discovered nearby in much fainter and less active supermassive black holes,” says Kazunori Akiyama, a research scientist at MIT Haystack Observatory and project lead. “The results pose a new question: how does the jet collimation happen consistently across such varied black hole systems?”

The new, incredibly sharp images of the 3C 273 jet were made possible by including ALMA observations. The GMVA and ALMA were connected across continents using very long baseline interferometry (VLBI) to obtain detailed information about distant astronomical sources. The remarkable VLBI capability of ALMA was enabled by the ALMA Phasing Project (APP) team. The international APP team, led by MIT Haystack Observatory, developed the hardware and software to turn ALMA, an array of 66 telescopes, into the world’s most sensitive astronomical interferometry station. Collecting data at these wavelengths dramatically increases the resolution and sensitivity of the array.

“The ability to use ALMA as part of global VLBI networks has been a complete game-changer for black hole science,” says Lynn Matthews, Haystack principal research scientist and commissioning scientist for the APP. “It enabled us to obtain the first-ever images of supermassive black holes, and now it is helping us to see for the first time incredible new details about how black holes power their jets.”

This study opens the door to further exploration of jet collimation processes in other black holes. Data obtained at higher frequencies allows scientists to observe finer details within quasars and other black holes.

“Formation mechanism of the jets from supermassive black holes is still elusive, though they were first identified more than 100 years ago,” says Hiroshi Nagai, project associate professor at NAOJ ALMA Project. “The sharpest images with the aid of ALMA and GMVA have significantly improved our understanding of the jets, and we hope to advance this study with even better angular resolution.”




Additional Information

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The GMVA observes at the 3mm wavelength, using the following stations for this research in April 2017: eight antennas of Very Long Baseline Array (VLBA), the Effelsberg 100m Radio Telescope of the Max-Planck-Institut für Radioastronomie (MPIfR), the IRAM 30m Telescope, the 20m telescope of the Onsala Space Observatory, and the 40m Radio Telescope of Yebes Observatory. The data were correlated at the DiFX VLBI correlator at the MPIfR in Bonn, Germany.




Contacts:

Nicolas Lira Turpaud
Joint ALMA Observatory, Chile
ALMA EPO Coordinator

nicolas.lira@alma.cl
+56 9 94 45 77 26

Alvaro Gonzalez
NAOJ · interim NAOJ ALMA Officer

Alvaro.Gonzalez@nao.ac.jp
+81-422-34-3889

Nancy Wolfe Kotary
[ MIT Haystack Observatory, USA

nwk@mit.edu
+1-617-715-5400




Monday, November 21, 2022

NASA's Webb Draws Back Curtain on Universe's Early Galaxies

Abell 2744 GLASS (NIRCam Image)
Credits: Science: NASA, ESA, CSA, Tommaso Treu (UCLA)
Image Processing: Zolt G. Levay (STScI)

 Release images | Release videos



A few days after officially starting science operations, NASA's James Webb Space Telescope propelled astronomers into a realm of early galaxies, previously hidden beyond the grasp of all other telescopes until now.

“Everything we see is new. Webb is showing us that there's a very rich universe beyond what we imagined," said Tommaso Treu of the University of California at Los Angeles, principal investigator on one of the Webb programs. "Once again the universe has surprised us. These early galaxies are very unusual in many ways."

Two research papers, led by Marco Castellano of the National Institute for Astrophysics in Rome, Italy, and Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology in Cambridge, Massachusetts, have been published in the Astrophysical Journal Letters.

These initial findings are from a broader Webb research initiative involving two Early Release Science (ERS) programs: the Grism Lens-Amplified Survey from Space (GLASS), and the Cosmic Evolution Early Release Science Survey (CEERS).

With just four days of analysis, researchers found two exceptionally bright galaxies in the GLASS-JWST images. These galaxies existed approximately 450 and 350 million years after the big bang (with a redshift of approximately 10.5 and 12.5, respectively), though future spectroscopic measurements with Webb will help confirm.

"With Webb, we were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data," said Naidu of the more distant GLASS galaxy, referred to as GLASS-z12, which is believed to date back to 350 million years after big bang. The previous record holder is galaxy GN-z11, which existed 400 million years after the big bang (redshift 11.1), and was identified in 2016 by Hubble and Keck Observatory in deep-sky programs.

"Based on all the predictions, we thought we had to search a much bigger volume of space to find such galaxies," said Castellano.

"These observations just make your head explode. This is a whole new chapter in astronomy. It's like an archaeological dig, and suddenly you find a lost city or something you didn’t know about. It’s just staggering," added Paola Santini, fourth author of the Castellano et al. GLASS-JWST paper.

"While the distances of these early sources still need to be confirmed with spectroscopy, their extreme brightnesses are a real puzzle, challenging our understanding of galaxy formation," noted Pascal Oesch at the University of Geneva in Switzerland, second author of the Naidu et al. paper.

The Webb observations nudge astronomers toward a consensus that an unusual number of galaxies in the early universe were so much brighter than expected. This will make it easier for Webb to find even more early galaxies in subsequent deep sky surveys, say researchers.

"We've nailed something that is incredibly fascinating. These galaxies would have had to have started coming together maybe just 100 million years after the big bang. Nobody expected that the dark ages would have ended so early," said Garth Illingworth of the University of California at Santa Cruz, a member of the Naidu/Oesch team. "The primal universe would have been just one hundredth its current age. It's a sliver of time in the 13.8 billion-year-old evolving cosmos."

Erica Nelson of the University of Colorado in Boulder, a member of the Naidu/Oesch team, noted that "our team was struck by being able to measure the shapes of these first galaxies; their calm, orderly disks question our understanding of how the first galaxies formed in the crowded, chaotic early universe." This remarkable discovery of compact disks at such early times was only possible because of Webb’s much sharper images, in infrared light, compared to Hubble.

"These galaxies are very different than the Milky Way or other big galaxies we see around us today," said Treu.

Illingworth emphasized the two bright galaxies found by these teams have a lot of light. He said one option is that they could have been very massive, with lots of low-mass stars, like later galaxies. Alternatively, they could be much less massive, consisting of far fewer extraordinarily bright stars, known as Population III stars. Long theorized, they would be the first stars ever born, blazing at blistering temperatures and made up only of primordial hydrogen and helium – before stars could later cook up heavier elements in their nuclear fusion furnaces. No such extremely hot, primordial stars are seen in the local universe.

"Indeed, the farthest source is very compact, and its colors seem to indicate that its stellar population is particularly devoid of heavy elements and could even contain some Population III stars. Only Webb spectra will tell," said Adriano Fontana, second author of the Castellano et al. paper and a member of the GLASS-JWST team.

Present Webb distance estimates to these two galaxies are based on measuring their infrared colors. Eventually, follow-up spectroscopy measurements showing how light has been stretched in the expanding universe will provide independent verification of these cosmic yardstick measurements.

The James Webb Space Telescope is the world’s premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).



About This Release: Credits:

Release: NASA, ESA, CSA, STScI

Media Contact:


Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
 Space Telescope Science Institute, Baltimore, Maryland

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