New Results from a Survey of Active Galactic Nuclei

This mosaic contains 2,200 ultraviolet images taken by the Neil Gehrels Swift Observatory of the Large Magellanic Cloud, requiring 5.4 days of exposure time. Credit: NASA/Swift/S. Immler (Goddard) and M. Siegel (Penn State)

An illustration of the Neil Gehrels Swift Observatory in front of a gamma-ray burst.
Credit: Spectrum and NASA E/PO, Sonoma State University, Aurore Simonnet

Locations of the objects surveyed in the second BASS data release. The symbol shape and color indicates the instrument and telescope used to collect that object’s spectrum. Credit: Koss et al. 2022

Redshift distribution of AGN in the BASS second data release.
Credit:Oh et al. 2022

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Across the universe, luminous galactic centers are fueled by supermassive black holes that accrete gas, dust, and stars from their surroundings. These powerful active galactic nuclei (AGN) radiate across the electromagnetic spectrum and emit jets of energetic particles, potentially shaping the evolution of the galaxies they inhabit. Collecting spectra of AGN is key to understanding the structure of the material that surrounds them and the role they may play in galaxy evolution — and a new public data release from a spectroscopic survey of AGN discovered by the Neil Gehrels Swift Observatory has expanded our ability to probe these objects.

Since 2005, the Neil Gehrels Swift Observatory has monitored the sky from gamma-ray to optical wavelengths, primarily in pursuit of the sources of gamma-ray bursts: extragalactic explosions potentially caused by massive stars going supernova or compact objects merging. However, Swift sees far more than just gamma-ray bursts — its Burst Alert Telescope (BAT), which scans 80% of the sky each day at X-ray and gamma-ray energies (14–195 kiloelectronvolts), has discovered hundreds of AGN in the local universe.

But detecting AGN is just the first step toward understanding the nature and importance of these objects — dedicated spectroscopic follow-up is a critical next step. Enter the BAT AGN Spectroscopic Survey (BASS): a project that aims to survey the most powerful AGN that have been detected in high-energy X-rays by Swift Observatory. In a new special issue of the Astrophysical Journal Supplement Series, the BASS team presents the latest step toward their goal of producing an immense catalog of AGN spectra.

This data release contains 1,449 optical spectra — 1,181 of which have never been released before — and 233 near-infrared spectra, all from 858 AGN in the local universe. The just published special issue presents catalogs of spectra, derived quantities, and first science results, including the following important findings:

• The objects discovered by the Burst Alert Telescope span a wide range of properties. Namely, the black hole masses, luminosities, accretion rates, and degree to which the targets are obscured by gas and dust all vary by at least five orders of magnitude, making this survey a useful probe of a wide variety of AGN. Additionally, few of the sources observed in this survey are contained in other surveys, making the BASS project a source of unique information.
• For the first time, the black hole mass function and the Eddington ratio distribution function — how the black hole mass and AGN luminosity vary with other factors — have been determined directly for heavily obscured objects. The resulting distribution functions show that obscured AGN are intrinsically less luminous compared to their theoretical maximum luminosities than their unobscured counterparts. This suggests that radiation plays a large role in determining the structure of the material close to an AGN.
• The masses of the supermassive black holes at the heart of obscured AGN tend to be underestimated when the mass is determined from measurements of hydrogen emission lines. Researchers can reduce this effect in the future studies by applying multiplicative factors when estimating masses this way.
• New diagnostics based on mid-infrared luminosities can distinguish between obscured and unobscured AGN, yielding new candidate sources that are heavily obscured. However, separating out star-forming galaxies remains a challenge.

The publicly available sample of spectra developed by the BASS team provides a valuable tool for researchers wishing to study AGN in the local universe. Looking forward, the team plans to supplement their current catalog with observations of fainter sources made by the Burst Alert Telescope, expanding our understanding of these cosmic engines.

Citation

Special ApJS Issue on the BAT AGN Spectroscopic Survey Second Data Release

“BAT AGN Spectroscopic Survey XXI: The Data Release 2 Overview,” Michael J. Koss et al 2022 ApJS 261
1. doi:10.3847/1538-4365/ac6c8f

By Kerry Hensley

Source: American Astronomical Society - AAS/Nova

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Follow the LEDA

LEDA 58109
Credit: ESA/Hubble & NASA, W. Keel

This luminescent image features multiple galaxies, perhaps most noticeably LEDA 58109, the lone galaxy in the upper right. LEDA 58109 is flanked by two further galactic objects to its lower left — an active galactic nucleus (AGN) called SDSS J162558.14+435746.4 that partially obscures the galaxy SDSS J162557.25+435743.5, which appears to poke out to the right behind the AGN. 

Galaxy classification is sometimes presented as something of a dichotomy: spiral and elliptical. However, the diversity of galaxies in this image alone highlights the complex web of galaxy classifications that exist, including galaxies that house extremely luminous AGNs at their cores, and galaxies whose shapes defy the classification of either spiral or elliptical. 

The sample of galaxies here also illustrates the wide variety of names that galaxies have: some relatively short, like LEDA 58109, and some very long and challenging to remember, such as the two galaxies to the left. This is due to the variety of cataloguing systems that chart the celestial objects in the night sky. No one catalogue is exhaustive, and they cover overlapping regions of the sky, so that many galaxies belong to several different catalogues. For example, the galaxy on the right is LEDA 58109 in the LEDA galaxy database, but is also known as MCG+07-34-030 in the MCG galaxy catalogue, and SDSS J162551.50+435747.5 in the SDSS galaxy catalogue — the same catalogue that also lists the two galaxies to the left.

Link

• Video of Follow the LEDA

Source: ESA/Hubble/potw

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Lens Flair

SGAS J143845+145407
Credit: ESA/Hubble & NASA, J. Rigby

This intriguing observation from the NASA/ESA Hubble Space Telescope shows a gravitationally lensed galaxy with the long-winded identification SGAS J143845+145407. Gravitational lensing has resulted in a mirror image of the galaxy at the centre of this image, creating a captivating centrepiece.

Gravitational lensing occurs when a massive celestial body — such as a galaxy cluster — causes a sufficient curvature of spacetime for the path of light around it to be visibly bent, as if by a lens. Appropriately, the body causing the light to curve is called a gravitational lens, and the distorted background object is referred to as being "lensed". Gravitational lensing can result in multiple images of the original galaxy, as seen in this image, or in the background object appearing as a distorted arc or even a ring. Another important consequence of this lensing distortion is magnification, allowing astronomers to observe objects that would otherwise be too far away or too faint to be seen.

Hubble has a special flair for detecting lensed galaxies. The telescope's sensitivity and crystal-clear vision allow it to see faint and distant gravitational lenses that cannot be detected with ground-based telescopes because of the blurring effect of Earth's atmosphere. Hubble was the first telescope to resolve details within lensed images of galaxies, and is capable of imaging both their shape and internal structure.

This particular lensed galaxy is from a set of Hubble observations that take advantage of gravitational lensing to peer inside galaxies in the early Universe. The lensing reveals details of distant galaxies that would otherwise be unobtainable, and this allows astronomers to determine star formation in early galaxies. This in turn gives scientists a better insight into how the overall evolution of galaxies has unfolded.

Links

• Video of Lens Flair

Source: ESA/Hubble/potw

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Zeta Ophiuchi: Embracing a Rejected Star

Zeta Ophiuchi

Credit X-ray: NASA/CXC/Dublin Inst. Advanced Studies/S. Green et al
Infrared: NASA/JPL/Spitzer

JPEG (244.6 kb) - Large JPEG (8.7 MB)- Tiff (33.6 MB) -More Images

A Tour of Zeta Ophiuchi -  More Animations

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Zeta Ophiuchi is a star with a complicated past, having likely been ejected from its birthplace by a powerful stellar explosion. A new look by NASA's Chandra X-ray Observatory helps tell more of the story of this runaway star.

Located about 440 light-years from Earth, Zeta Ophiuchi is a hot star that is 20 times more massive than the Sun. Previous observations have provided evidence that Zeta Ophiuchi was once in close orbit with another star, before being ejected at about 100,000 miles per hour when this companion was destroyed in a supernova explosion over a million years ago. Previously released infrared data from NASA's now-retired Spitzer Space Telescope, seen in this new composite image, reveals a spectacular shock wave (red and green) that was formed by matter blowing away from the star's surface and slamming into gas in its path. Data from Chandra shows a bubble of X-ray emission (blue) located around the star, produced by gas that has been heated by the effects of the shock wave to tens of millions of degrees.

A team of astronomers led by Samuel Green from the Dublin Institute for Advanced Studies in Ireland has constructed the first detailed computer models of the shock wave. They have begun testing whether the models can explain the data obtained at different wavelengths, including X-ray, optical, infrared and radio observations. All three of the different computer models predict fainter X-ray emission than observed. The bubble of X-ray emission is brightest near the star, whereas two of the three computer models predict the X-ray emission should be brighter near the shock wave.

In the future these researchers plan to test more complicated models with additional physics — including the effects of turbulence, and particle acceleration — to see whether the agreement with X-ray data will improve.

A paper describing these results has been accepted in the journal Astronomy and Astrophysics and a preprint is available here. The Chandra data used here was originally analyzed by Jesús Toala from the Institute of Astrophysics of Andalucia in Spain, who also wrote the proposal that led to the observations.

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.

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Fast Facts for Zeta Ophiuchi:

Credit X-ray: NASA/CXC/Dublin Inst. Advanced Studies/S. Green et al.; Infrared: NASA/JPL/Spitzer Scale: Image is about 36 arcmin (4.6 light-years) across.
Category:Normal Stars & Star Clusters
Coordinates (J2000): RA 16h 37m 09.54s | Dec -10° 34´ 01.53"
Constellation:Ophiuchus
Observation Date: July 3, 2013
Observation Time: 20 hours 3 minutes
Obs. ID: 14540
Instrument:ACIS
References: Green, S. et al., 2022, A&A, accepted;arXiv:2203.06331
Color Code: X-ray: dark blue; Infrared: red, green, and blue
Distance Estimate: About 440 light-years

Source: NASA's Chandra X-Ray Observatory

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Measuring the Universe with Star-Shattering Explosions

Conceptual image of this research: using Gamma Ray Bursts to determine distance in space
Credit: NAOJ - Original size (2.6MB)

An international team of 23 researchers led by Maria Dainotti, Assistant Professor at the National Astronomical Observatory of Japan (NAOJ), has analyzed archive data for powerful cosmic explosions from the deaths of stars and found a new way to measure distances in the distant Universe.

With no landmarks in space, it is very difficult to get a sense of depth. One technique astronomers use is to look for “standard candles,” objects or events where the underlying physics dictate that the absolute brightness (what you would see if you were right next to it) is always the same. By comparing this calculated absolute brightness to the apparent brightness (what is actually observed from Earth), it is possible to determine the distance to the standard candle, and by extension other objects in the same area. The lack of standard candles bright enough to be seen more than 11 billion light-years away has hindered research on the distance Universe. Gamma-Ray bursts (GRBs), bursts of radiation produced by the deaths of massive stars, are bright enough, but their brightness depends on the characteristics of the explosion.

Embracing the challenge of attempting to use these bright events as standard candles, the team analyzed archive data for the visible light observations of 500 GRBs taken by world-leading telescopes such as the Subaru Telescope (owned and operated by NAOJ), RATIR, and satellites such as the Neil Gehrels Swift Observatory. Studying the light curve’s pattern of how the GRB brightens and dims over time, the team identified a class of 179 GRBs which have common features and have likely been caused by similar phenomena. From the characteristics of the light curves, the team was able to calculate a unique brightness and distance for each GRB which can be used as a cosmological tool.

These findings will provide new insights into the mechanics behind this class of GRBs, and provide a new standard candle for observing the distant Universe. Lead author Dainotti had previously found a similar pattern in X-ray observations of GRBs, but visible light observations have been revealed to be more accurate in determining cosmological parameters.

These results appeared as Dainotti et al. “The Optical Two and Three-Dimensional Fundamental Plane Correlations for Nearly 180 Gamma-Ray Burst Afterglows with Swift/UVOT, RATIR, and the SUBARU Telescope” in the Astrophysical Journal Supplement Series on July 21, 2022.

Related Links

• Measuring the Universe with Star-Shattering Explosions (Subaru Telescope)
• Charting the Expansion History of the Universe with Supernovae (May 14, 2021)

Source: National Astronomical Observatory of Japan (NAOJ)/News

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Can Shock Waves Create the Conditions for Molecule Formation?

This infrared image from the Spitzer Space Telescope shows the dark, dusty cloud Lynds 1157, which hosts young protostars
Credit:NASA/JPL-Caltech/UIUC

The dark, dusty clouds surrounding young, hot protostars are the sites of molecule formation. What can new radio observations tell us about the potential for molecule formation in the shocked surroundings of a nearby protostar system?

A visible-light image of the interstellar dark cloud Lynds 1157. Infrared or radio observations are needed to reveal the young stars hidden by the dust. Credit:NASA/JPL-Caltech/AURA

Making Molecules

Over the past century, astronomers have discovered more than a hundred kinds of molecules in space. Exactly how these molecules form and survive in the cold, tenuous gas of the interstellar medium is an active area of research. One of several ways that molecules are thought to form is in the wake of a shock wave, which condenses and warms the interstellar medium, helping lone atoms link up in the vastness of space.

Shock waves can be produced by outflows from newly forming stars called protostars, which are still wrapped in dense clouds of gas and dust. Luckily, infrared and radio observations allow us to draw back this dusty curtain and peer into the birthplaces of young stars and watch as they collect gas and shoot out jets of material. In a new publication, a team led by Siyi Feng (冯思轶) from Xiamen University presents new radio data that probes the surroundings of a young protostellar system at the heart of the dark cloud Lynds 1157 — one of the best places to study how shocks impact interstellar chemistry.

Example maps of an outflowing jet from Lynds 1157 in two emission lines of ammonia. The shocks are located at the places labeled B0, B1, and B2, while smaller structures are labeled with additional letters. The protobinary is labeled “mm.” Credit: Adapted from Feng et al. 2022

Peering at Protostars

Previous observations of Lynds 1157 have shown that the region hosts organic molecules like methanol and cyanoacetylene — a clear sign of ongoing interstellar chemistry. What makes the region especially interesting is the series of shocks that have formed along a jet that flows outward from the central source, which is likely a protobinary system. Observations show that the outermost shock is 1,000 years old, while the inner shocks are younger, allowing us to study how the temperature and density of the gas changed over time as the shocks passed through.

Using the Karl G. Jansky Very Large Array, Feng and collaborators observed emission lines of ammonia (NH3) to make high-resolution maps of Lynds 1157 and measure how the temperature and density of the gas vary throughout the cloud.

Maps of the mean temperature (left), density (center), and ratio of ammonia molecules in an excited state to those in an unexcited state (right).  Adapted from Feng et al. 2022

Studying Shocks

The ammonia emission lines trace the jet as it moves outward from the central protobinary, and the observations show that the gas is warmest close to the protobinary, cooler farther out along the jet, and densest at the locations of the shocks. And at the locations of the shocks, the team found evidence for ammonia molecules in an excited state, a clear indication that the gas has been heated by the shocks.

The team’s observations show that the passage of shocks heated and compressed the gas, and that as the shocks moved outward, the gas cooled. This illustrates that shocks can provide the warm, dense environment needed for molecules to form. The measurements made in this work should enable detailed chemical modeling, allowing for an even better understanding of how shocks have transformed the gas around these young protostars and paved the way for molecule formation.

Citation

“A Detailed Temperature Map of the Archetypal Protostellar Shocks in L1157,” S. Feng et al 2022 ApJL 933 L35. doi:10.3847/2041-8213/ac75d7

Source:American Astronomical Society - AAS/Nova

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A New Method to Detect Exoplanets

Artist’s impression of a cataclysmic variable system as seen from the surface of an orbiting planet
Credit: Departamento de Imagen y Difusion FIME-UANL/ Lic. Debahni Selene Lopez Morales D.R. 2022
Licence type:Attribution-NonCommercial-NoDerivs (CC BY-NC-ND 4.0)

In recent years, a large number of exoplanets have been found around single ‘normal’ stars. New research shows that there may be exceptions to this trend. Researchers from the Autonomous University of Nuevo León (UANL), the National Autonomous University of Mexico (UNAM), and New York University Abu Dhabi suggest a new way of detecting dim bodies, including planets, orbiting exotic binary stars known as Cataclysmic Variables (CVs).

CVs are binary star systems in which the two stars are in extremely close proximity to each other; so close that the less massive object transfers mass to the more massive. CVs are typically formed of a small, cool type of star known as a red dwarf star, and a hot, dense star – a white dwarf. Red dwarf stars have a mass between 0.07 and 0.30 solar masses and a radius of around 20% of the Sun’s, while white dwarf stars have a typical mass of around 0.75 Solar masses and a very small radius similar to that of planet Earth.

In the CV system, the transfer of matter from the small star forms an accretion disk around the compact, more massive star. The brightness of a CV system mainly comes from this disk, and overpowers the light coming from the two stars. A third dim body orbiting a CV can influence the mass transfer rate between the two stars, and hence the brightness of the entire system. The method described in the new work is based on the change of brightness in the accretion disk due to perturbations of the third body that orbits around the inner two stars.

In their research, team leader Dr Carlos Chavez and his collaborators have estimated the mass and distance of a third body orbiting four different CVs using the changes in the brightness of each system. According to calculations carried out by the team, such brightness variations have very long periods in comparison to the orbital periods in the triple system. Two out of the four CVs appear to have bodies resembling planets in orbit around them.

Dr Chavez comments on the new findings, “Our work has proven that a third body can perturb a cataclysmic variable in such a way that can induce changes in brightness in the system. These perturbations can explain both the very long periods that have been observed - between 42 and 265 days- and the amplitude of those changes in brightness.” He adds, “Of the four systems we studied, our observations suggest that two of the four have objects of planetary mass in orbit around them.”

The scientists believe that this is a promising new technique for finding planets in orbit around binary star systems, adding to the thousands already found in the last three decades.

Source:Royal Astronomical Society (RAS)/News

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Media Contacts

Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)7802 877699
press@ras.ac.uk

Cait Cullen
Royal Astronomical Society
cait.kutassy-clement@warwick.ac.uk

Science Contact

Dr Carlos Chavez
Universidad Autónoma De Nuevo León
carlos.chavezpch@uanl.edu.mx

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Further information

The research appears in ‘Testing the third-body hypothesis in the cataclysmic variables LU Camelopardalis, QZ Serpentis, V1007 Herculis and BK Lyncis’, Carlos E Chavez et al., published in Monthly Notices of the Royal Astronomical Society, in press.

Notes for Editors

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognises outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

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Gemini’s GHOST Captures Exquisite First Light Observations of a Bright, Chemically Rich Star

The two GHOST spectra. This mosaic shows the two GHOST spectra of HD 222925, a remarkably bright, chemically complex star. This star is a prime example of the type of object that GHOST will investigate. The two GHOST spectra shown here, which were produced in the same single observation, measure light from around 350 nm to around 1015 nm. Light that is ‘bluer’ than 380 nm is ultraviolet and is invisible to our eyes. Light that is ‘redder’ than around 750 nm is infrared and is also invisible to our eyes. The dark lines in the rainbow are like the fingerprints of the gasses present in the star, including hydrogen, calcium, iron and gold. See this image comparison to see the most prominent features labeled. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/GHOST Consortium.  download Large JPEG

The two GHOST spectra (labeled). This mosaic shows the two GHOST spectra of HD 222925, a remarkably bright, chemically complex star. This star is a prime example of the type of object that GHOST will investigate. The dark lines in the rainbow are absorption lines — fingerprints of the gasses present in the star, including hydrogen, calcium, and also numerous metals like iron and gold. To the right a number of features from molecules in the Earth’s own atmosphere are seen. Any ground-based observation is subject to contamination from telluric (Earth-originating) sources like water vapor and oxygen. The effect of these lines is normally removed in subsequent steps of the analysis process. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/GHOST Consortium.  download Large JPEG

The full GHOST spectrum. The image shows a representation of the full GHOST spectrum of HD 222925, a remarkably bright, chemically complex star. This star is a prime example of the type of object that GHOST will investigate. The spectrum measures light from around 350 nm to around 1015 nm. Light that is ‘bluer’ than 380 nm is ultraviolet and is invisible to our eyes. Light that is ‘redder’ than around 750 nm is infrared and is also invisible to our eyes. The wiggly line represents the data measured revealing detailed information about the star's chemical composition. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/GHOST Consortium.  download Large JPEG

Diagram of GHOST. This diagram shows the three components of GHOST as they fit into Gemini South. GHOST is an echelle spectrograph and consists of three primary components; the Cassegrain unit mounted on the telescope, the spectrograph bench located in the pier lab for image and wavelength stability, and a fiber cable connecting the two. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/GHOST Consortium.  download Large JPEG

GHOST installed on Gemini South. NOIRLab staff on the telescope floor with the GHOST instrument in the background. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Paredes.  download Large JPEG

Cosmoview Episode 48: Gemini’s GHOST Captures Exquisite First Light Observations of a Bright, Chemically Rich Star. Credit: Images and Videos: International Gemini Observatory/PROGRAM/NOIRLab/NSF/AURA, S. Brunier/Digitized Sky Survey 2, E. Slawik, J. da Silva (Spaceengine), NASA’s Goddard Space Flight Center/Scott Wiessinger, J. Bassett, Caltech/IPAC Image Processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab) Music: Stellardrone - Airglow

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NSF’s NOIRLab-operated Gemini South telescope upgraded with next-generation, high-resolution spectrograph.

Gemini South, one of the world’s most productive and powerful optical-infrared telescopes, received a major capability boost with the successful installation of a new high-resolution spectrograph called GHOST constructed by an international consortium. This cutting-edge scientific instrument will expand our understanding of the earliest stars, the chemical fingerprints of distant planetary systems, and the formation and evolution of galaxies. Gemini South in Chile is one half of the International Gemini Observatory, operated by NSF’s NOIRLab.

The Gemini South telescope’s newest science instrument — GHOST, the Gemini High-resolution Optical SpecTrograph — achieved first light by making exquisite observations of HD 222925, a remarkably bright, chemically complex star located more than 1400 light-years away in the direction of the southern hemisphere constellation Tucana. This star is a prime example of the type of object that GHOST will investigate. Gemini South is one half of the International Gemini Observatory. 

“This is an exciting milestone for astronomers around the globe who rely on Gemini South to study the Universe from this exceptional vantage point in Chile,” said Jennifer Lotz, Director of Gemini Observatory. “Once this next-generation instrument is commissioned, GHOST will be an essential component of the astronomers toolbox.”

Spectrographs are among the most important science instruments in all of astronomy. Unlike high-resolution cameras that capture amazing details of distant stars and galaxies, spectrographs precisely analyze the spectrum of light emitted by these objects, revealing detailed information about their chemical composition, motion and rotation, and ancient counterparts at the edge of the observable Universe. 

GHOST, which has ten times the spectral resolution of GMOS, Gemini’s other major optical spectrograph, is the most sensitive high-resolution spectrograph across the full optical wavelength range of any of the spectrographs currently in operation on comparably-sized telescopes [1]. 

GHOST will also provide crucial follow-up observations of key targets emerging from many ongoing and future surveys, such as Vera C. Rubin Observatory’s Legacy Survey of Space and Time, SkyMapper, and GAIA. The instrument is open-access, meaning any researcher with a compelling science case will be able to submit proposals to use it for their research. NOIRLab will provide a data reduction pipeline for astronomers using the instrument. 

Australian Astronomical Optics (AAO) at Macquarie University leads the GHOST team, which includes the National Research Council of Canada (NRC) Herzberg Astronomy and Astrophysics Research Centre which was responsible for the construction of the spectrograph, and the Australian National University (ANU), leading on the instrument control system and data reduction software.

The design and construction of GHOST began in 2010 and took ten years to complete. The instrument was delivered to Gemini South in early 2020, although COVID-19 restrictions meant that installation by the teams from Canada and Australia had to wait until early 2022. With its successful installation and first-light observations, the commissioning team put GHOST through its paces to verify its systems are performing as designed. Once the commissioning process is complete, it will join Gemini South’s diverse suite of advanced optical and infrared instruments and be offered to astronomers to use. 

“The installation and commissioning have been a long time coming, but the team has been working efficiently and quickly”, said Steve Margheim, GHOST Project Scientist at NSF’s NOIRLab. “It was a really special day when we saw our first rainbow from the instrument”.

“With the successful commissioning of GHOST, NSF congratulates the instrument team on delivering to the international astronomy community enhanced capability to explore planets, stars, and galaxies," said Martin Still Gemini Program Officer at the National Science Foundation. "We eagerly await the new discoveries.”

It is expected that GHOST will be made available to the astronomical community during the first half of 2023.

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Notes

[1] GHOST is an echelle spectrograph and consists of three primary components; the Cassegrain unit mounted on the telescope, the spectrograph bench located in the pier lab for image and wavelength stability, and a fiber cable connecting the two.

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Links

• Photos of Gemini South
• Videos of Gemini South
• Images of GHOST commissioning
• GHOST webpage
• NOIRLab Stories post about GHOST
• Live from NOIRLab about GHOST in English
• Live from NOIRLab about GHOST in Spanish
• Gemini Call for Proposals

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Contacts

Jennifer Lotz
Director, International Gemini Observatory
Email: jennifer.lotz@noirlab.edu

Amanda Kocz
Communications Manager
NSF’s NOIRLab
Tel: +1 520 318 8591
Email:amanda.kocz@noirlab.edu

Source: Gemini Observatory/News

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'Black hole police' discover a dormant black hole outside our galaxy

PR Image eso2210a

Artist’s impression of VFTS 243 in the Tarantula Nebula

PR Image eso2210b

The rich region around the Tarantula Nebula in the Large Magellanic Cloud

PR Image eso2210c

Composite infrared and radio image of 30 Doradus

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Videos

PR Video eso2210a

'Black Hole Police' Spot Extragalactic Black Hole (ESOcast 255 Light)

 

PR Video eso2210b
Artist’s animation of VFTS 243 

PR Video eso2210c

Zooming in on VFTS 243

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A team of international experts, renowned for debunking several black hole discoveries, have found a stellar-mass black hole in the Large Magellanic Cloud, a neighbour galaxy to our own. "For the first time, our team got together to report on a black hole discovery, instead of rejecting one," says study leader Tomer Shenar. Moreover, they found that the star that gave rise to the black hole vanished without any sign of a powerful explosion. The discovery was made thanks to six years of observations obtained with the European Southern Observatory’s (ESO’s) Very Large Telescope (VLT).

“We identified a ‘needle in a haystack’,” says Shenar who started the study at KU Leuven in Belgium [1] and is now a Marie-Curie Fellow at Amsterdam University, the Netherlands. Though other similar black hole candidates have been proposed, the team claims this is the first ‘dormant’ stellar-mass black hole to be unambiguously detected outside our galaxy.

Stellar-mass black holes are formed when massive stars reach the end of their lives and collapse under their own gravity. In a binary, a system of two stars revolving around each other, this process leaves behind a black hole in orbit with a luminous companion star. The black hole is ‘dormant’ if it does not emit high levels of X-ray radiation, which is how such black holes are typically detected. “It is incredible that we hardly know of any dormant black holes, given how common astronomers believe them to be”, explains co-author Pablo Marchant of KU Leuven. The newly found black hole is at least nine times the mass of our Sun, and orbits a hot, blue star weighing 25 times the Sun’s mass.

Dormant black holes are particularly hard to spot since they do not interact much with their surroundings. “For more than two years now, we have been looking for such black-hole-binary systems,” says co-author Julia Bodensteiner, a research fellow at ESO in Germany. “I was very excited when I heard about VFTS 243, which in my opinion is the most convincing candidate reported to date.” [2]

To find VFTS 243, the collaboration searched nearly 1000 massive stars in the Tarantula Nebula region of the Large Magellanic Cloud, looking for the ones that could have black holes as companions. Identifying these companions as black holes is extremely difficult, as so many alternative possibilities exist.

“As a researcher who has debunked potential black holes in recent years, I was extremely skeptical regarding this discovery,” says Shenar. The skepticism was shared by co-author Kareem El-Badry of the Center for Astrophysics | Harvard & Smithsonian in the USA, whom Shenar calls the “black hole destroyer”. “When Tomer asked me to double check his findings, I had my doubts. But I could not find a plausible explanation for the data that did not involve a black hole,” explains El-Badry.

The discovery also allows the team a unique view into the processes that accompany the formation of black holes. Astronomers believe that a stellar-mass black hole forms as the core of a dying massive star collapses, but it remains uncertain whether or not this is accompanied by a powerful supernova explosion.

"The star that formed the black hole in VFTS 243 appears to have collapsed entirely, with no sign of a previous explosion," explains Shenar. "Evidence for this ‘direct-collapse’ scenario has been emerging recently, but our study arguably provides one of the most direct indications. This has enormous implications for the origin of black-hole mergers in the cosmos."

The black hole in VFTS 243 was found using six years of observations of the Tarantula Nebula by the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument on ESO’s VLT [3].

Despite the nickname ‘black hole police’, the team actively encourages scrutiny, and hopes that their work, published today in Nature Astronomy, will enable the discovery of other stellar-mass black holes orbiting massive stars, thousands of which are predicted to exist in Milky Way and in the Magellanic Clouds.

“Of course I expect others in the field to pore over our analysis carefully, and to try to cook up alternative models,” concludes El-Badry. “It's a very exciting project to be involved in.”

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Notes

[1] The work was conducted in the team lead by Hugues Sana at KU Leuven’s Institute of Astronomy.

[2] A separate study led by Laurent Mahy, involving many of the same team members and accepted for publication in Astronomy & Astrophysics, reports on another promising stellar-mass black hole candidate, in the HD 130298 system in our own Milky Way galaxy.

[3] The observations used in the study cover about six years: they consist of data from the VLT FLAMES Tarantula Survey (led by Chris Evans, United Kingdom Astronomy Technology Centre, STFC, Royal Observatory, Edinburgh; now at the European Space Agency) obtained from 2008 and 2009, and additional data from the Tarantula Massive Binary Monitoring programme (led by Hugues Sana, KU Leuven), obtained between 2012 and 2014.

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More Information

This research was presented in a paper titled “An X-ray quiet black hole born with a negligible kick in a massive binary of the Large Magellanic Cloud” to appear in Nature Astronomy (doi: 10.1038/s41550-022-01730-y).

The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement numbers 772225: MULTIPLES) (PI: Sana).

The team is composed of T. Shenar (Institute of Astronomy, KU Leuven, Belgium [KU Leuven]; Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, the Netherlands [API]), H. Sana (KU Leuven), L. Mahy (Royal Observatory of Belgium, Brussels, Belgium), K. El-Badry (Center for Astrophysics | Harvard & Smithsonian, Cambridge, USA [CfA]; Harvard Society of Fellows, Cambridge, USA; Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), P. Marchant (KU Leuven), N. Langer (Argelander-Institut für Astronomie der Universität Bonn, Germany, Max Planck Institute for Radio Astronomy, Bonn, Germany [MPIfR]), C. Hawcroft (KU Leuven), M. Fabry (KU Leuven), K. Sen (Argelander-Institut für Astronomie der Universität Bonn, Germany, MPIfR), L. A. Almeida (Universidade Federal do Rio Grande do Norte, Natal, Brazil; Universidade do Estado do Rio Grande do Norte, Mossoró, Brazil), M. Abdul-Masih (ESO, Santiago, Chile), J. Bodensteiner (ESO, Garching, Germany), P. Crowther (Department of Physics & Astronomy, University of Sheffield, UK), M. Gieles (ICREA, Barcelona, Spain; Institut de Ciències del Cosmos, Universitat de Barcelona, Barcelona, Spain), M. Gromadzki (Astronomical Observatory, University of Warsaw, Poland [Warsaw]), V. Henault-Brunet (Department of Astronomy and Physics, Saint Mary’s University, Halifax, Canada), A. Herrero (Instituto de Astrofísica de Canarias, Tenerife, Spain [IAC]; Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain [IAC-ULL]), A. de Koter (KU Leuven, API), P. Iwanek (Warsaw), S. Kozłowski (Warsaw), D. J. Lennon (IAC, IAC-ULL), J. Maíz Apellániz (Centro de Astrobiología, CSIC-INTA, Madrid, Spain), P. Mróz (Warsaw), A. F. J. Moffat (Department of Physics and Institute for Research on Exoplanets, Université de Montréal, Canada), A. Picco (KU Leuven), P. Pietrukowicz (Warsaw), R. Poleski (Warsaw), K. Rybicki (Warsaw and Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Israel), F. R. N. Schneider (Heidelberg Institute for Theoretical Studies, Heidelberg, Germany [HITS]; Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Heidelberg, Germany), D. M. Skowron (Warsaw), J. Skowron (Warsaw), I. Soszyński (Warsaw), M. K. Szymański (Warsaw), S. Toonen (API), A. Udalski (Warsaw), K. Ulaczyk (Department of Physics, University of Warwick, UK), J. S. Vink (Armagh Observatory & Planetarium, UK), and M. Wrona (Warsaw).

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 two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. 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.

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Links

• Research paper
• Photos of the VLT
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

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Contacts

Tomer Shenar
KU Leuven and University of Amsterdam
Leuven and Amsterdam, Belgium and The Netherlands
Email: t.shenar@uva.nl

Julia Bodensteiner
European Southern Observatory
Garching bei München, Germany
Tel: +49-89-3200-6409
Email: julia.bodensteiner@eso.org

Kareem El-Badry
Center for Astrophysics | Harvard & Smithsonian
Cambridge, USA
Email: kareem.el-badry@cfa.harvard.edu

Pablo Marchant
KU Leuven
Leuven, Belgium
Tel: +32 16 33 05 47
Email: pablo.marchant@kuleuven.be

Hugues Sana
KU Leuven
Leuven, Belgium
Tel: +32 479 50 46 73
Email: hugues.sana@kuleuven.be

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

Source: ESO/News

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Brief Encounter with Mysterious Heavenly Event

Figure 1: Artist’s impression of possible origins of the fast, high-energy event MUSSES2020J
Credit: Kavli IPMU, University of Tokyo

Figure 2: The schematic light curves of MUSSES2020J and other typical energetic transients. Green and orange points denote the stages that MUSSES2020J was observed by the Subaru Telescope and follow-up telescopes, respectively. HSC, g, r, and i composite multicolor thumbnail image of the host galaxy is shown in the bottom-right corner. A blue cross indicates the location of MUSSES2020J, which is almost at the nucleus of the host galaxy. Credit: Kavli IPMU, University of Tokyo

Across many Asian cultures, there is a much-loved story of Tanabata: the Weaving Princess and the Cow Herder, a happy young couple in the heavens who are separated as punishment for neglecting their duties and only allowed to meet one night each year. Every summer there are festivals to celebrate this short but joyous reunion. This Tanabata season, astronomers announced a different kind of brief cosmic encounter, even complete with references to a "cow".

The Subaru Telescope’s wide field-of-view and high sensitivity combined with Big Data techniques have made it possible to search wide areas of the heavens, looking for transient phenomena which change rapidly with time. Dr. Ji-an Jiang, at the National Astronomical Observatory of Japan (formerly at the Kavli Institute for the Physics and Mathematics of the Universe), is leading the "MUltiband Subaru Survey for Early-phase Supernovae" (MUSSES) project to look for fast-evolving transients within one day of their occurrence. The team has discovered 20 fast-evolving transients in December 2020, and one of them, MUSSES2020J (AT 2020afay), caught Jiang's attention.

MUSSES2020J was very dim in the first images but brightened significantly over the course of the observations, indicating that the team caught it at the very beginning of its occurrence. Follow-up observations confirmed that this event evolved much faster than normal supernovae and about 50 times brighter. Astronomers still don’t know what could cause this kind of event. Only a handful of others have ever been observed, the most famous being AT 2018cow. The team proposes calling this new class of events "Fast Blue Ultraluminous Transients" (FBUT).

MUSSES2020J was caught earlier in its evolution than any other FBUTs. "Thanks to the high-cadence survey mode and the excellent performance of Subaru/HSC, we were able to perfectly catch this amazing phenomenon for the first time. The early light-curve information should bring some unique information to understand the origin of these amazing transients," comments Jiang.

Due to the suddenness and power of FBUTs, astronomers suspect that a compact object like a black hole or neutron star is involved, but exactly what happens and how remains a mystery. The team will continue searching for the answers, but this brief encounter with a mysterious heavenly phenomenon has left the astronomers as happy as the reunited Weaving Princess and Cow Herder.

These results appeared as, Jiang et al. "MUSSES2020J: The Earliest Discovery of a Fast Blue Ultraluminous Transient at Redshift 1.063" in The Astrophysical Journal Letters on July 12, 2022.

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Relevant Links

• Kavli IPMU July 13, 2022 Press Release
• NAOJ July 13, 2022 Press Release
• University of Tokyo July 13, 2022 Press Release
• Researchers uncover model for extremely luminous and fast rising supernova (Kavli IPMU January 18, 2022 Press Release)
• Surface Helium Detonation Spells End for White Dwarf (Subaru Telescope October 4, 2017 Press Release)

Source: Subaru Telescope

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Portrait of a Globular Cluster

Terzan 2
Credit: ESA/Hubble & NASA, R. Cohen

The globular cluster Terzan 2 in the constellation Scorpio features in this observation from the NASA/ESA Hubble Space Telescope. Globular clusters are stable, tightly gravitationally bound clusters of tens of thousands to millions of stars found in a wide variety of galaxies. The intense gravitational attraction between the closely packed stars gives globular clusters a regular, spherical shape. As a result, images of the hearts of globular clusters, such as this observation of Terzan 2, are crowded with a multitude of glittering stars.

Hubble used both its Advanced Camera for Surveys and its Wide Field Camera 3 in this observation, taking advantage of the complementary capabilities of these instruments. Despite having only one primary mirror, Hubble’s design allows multiple instruments to be used to inspect astronomical objects. Light from distant astronomical objects enters Hubble and is collected by the telescope's 2.4-metre primary mirror; it is then reflected off the secondary mirror into the depths of the telescope, where smaller mirrors can direct light into individual instruments.

Each of the four operational instruments on Hubble is a masterpiece of astronomical engineering in its own right, and contains an intricate array of mirrors and other optical elements to remove any aberrations or optical imperfections from observations, as well as filters which allow astronomers to observe specific wavelength ranges. The mirrors inside each instrument also correct for the slight imperfection of Hubble's primary mirror. The end result is a crystal-clear observation, such as this glittering portrait of Terzan 2.

Source: ESA/Hubble/potw

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Citizen Scientist Leads Discovery of 34 Ultracool Dwarf Binaries Using Archive at NSF’s NOIRLab

PR Image noirlab2215a

Illustration of an ultracool dwarf with a companion white dwarf

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Videos

PR Video noirlab2215a

Cosmoview Episode 47: Citizen Scientist Leads Discovery of 34 Ultracool Dwarf Binaries Using Archive at NSF’s NOIRLab 

 

PR Video noirlab2215b

CosmoView Episodio 47: Científico ciudadano lidera descubrimiento de 34 sistemas solares binarios enanos

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Amateur astronomer delves into archival data at the Community Science and Data Center to discover 34 ultracool dwarfs accompanying low-mass stars or white dwarfs

How often do stars live alone? For brown dwarfs — objects that straddle the boundary between the most massive planets and the smallest stars — astronomers need to uncover more examples of their companions to find out. Ace citizen scientist Frank Kiwy has done just that by using the Astro Data Lab science platform at NSF’s NOIRLab to discover 34 new ultracool dwarf binary systems in the Sun's neighborhood, nearly doubling the number of such systems known.

A citizen scientist has searched NSF's NOIRLab’s catalog of 4 billion celestial objects, known as NOIRLab Source Catalog DR2, to reveal brown dwarfs with companions. His intensive investigation led to the discovery of 34 ultracool dwarf binary systems, nearly doubling previously known samples [1].

Brown dwarfs lie somewhere between the most massive planets and the smallest stars. Lacking the mass needed to sustain nuclear reactions in their core, brown dwarfs loosely resemble cooling embers on a huge scale. Their faintness and relatively small sizes make them difficult to identify. Data from sensitive telescopes have enabled the discovery of several thousand objects but just a small subset have been identified as binaries. The difficulty in observing these faint embers also means that astronomers are still unsure how often brown dwarfs have companions.

To help find brown dwarfs, the astronomers of the Backyard Worlds: Planet 9 citizen science project have previously turned to a worldwide network of more than 100,000 volunteer citizen scientists who scrutinized telescope images to identify the subtle motion of brown dwarfs against background stars. Despite the abilities of machine learning and supercomputers, the human eye is still a unique resource when it comes to scouring telescope images for moving objects.

“The Backyard Worlds project has fostered a diverse community of talented volunteers,” commented Aaron Meisner, an astronomer at NSF’s NOIRLab and co-founder of Backyard Worlds. “150,000 volunteers across the globe have participated in Backyard Worlds, among which a few hundred ‘super users’ perform ambitious self-directed research projects.”

One such ‘super sleuth — citizen scientist Frank Kiwy — embarked on a research project involving the NOIRLab Source Catalog DR2, a catalog of nearly 4 billion unique celestial objects that contains all of the public imaging data in NOIRLab's Astro Data Archive. By searching the data for objects with the color of brown dwarfs, Kiwy was able to find more than 2500 potential ultracool dwarfs lurking in the archive. These were then scrutinized for hints of comoving companions, yielding a total of 34 systems comprising a white dwarf or low-mass star with an ultracool dwarf companion [2]. Kiwy then led a team of professional astrophysicists in publishing these discoveries in a scientific paper.

“I love the Backyard Worlds: Planet 9 project! Once you master the regular workflow you can dive much deeper into the subject,” commented Kiwy. “If you're a person who is curious and not afraid to learn something new, this might be the right thing for you.” “This amazing result clearly demonstrates that NOIRLab’s data archive has a reach far beyond that of professional astronomers,” notes Chris Davis, NSF’s Program Director for NOIRLab. “Keen members of the public can also participate in cutting-edge research and directly share in the joy of cosmic discovery!”

As well as being an inspiring story of citizen science, these discoveries could help astronomers determine if brown dwarfs are more akin to oversized planets or undersized stars, as well as providing insights into how star systems evolve over time. It also demonstrates the continued exceptional contribution to astronomy made by scientists using astronomical archives and science platforms such as NOIRLab’s Astro Data Archive and Astro Data Lab at the Community Science and Data Center (CSDC).

“These discoveries were made by an amateur astronomer who conquered astronomical big data,” concluded Aaron Meisner. “Modern astronomy archives contain an immense treasure trove of data and often harbor major discoveries just waiting to be noticed.”

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Notes

[1] Previous samples include white dwarf plus ultracool dwarf (L dwarf) pairs separated by more than 150 astronomical units (au), and red dwarf plus L dwarf pairs with separations between 700 and 1800 au. An astronomical unit (au) is a unit used by astronomers that was originally chosen to represent the average distance between the Earth and the Sun: roughly 150 million kilometers or 93 million miles.

[2] The closest-together pair of dwarfs had a physical separation of only ~170 au, and the furthest apart were about 8500 au from one another.

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More Information

This research was presented in the paper “Discovery of 34 low-mass comoving systems using NOIRLab Source Catalog DR2” to appear in The Astronomical Journal.

The team is composed of Frank Kiwy (Backyard Worlds: Planet 9), Jacqueline K. Faherty (Department of Astrophysics, American Museum of Natural History), Aaron Meisner (NSF’s NOIRLab), Adam C. Schneider, (United States Naval Observatory and Department of Physics and Astronomy, George Mason University), J. Davy Kirkpatrick (IPAC, Caltech), Marc J. Kuchner (NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory), Adam J. Burgasser (Center for Astrophysics and Space Science, University of California San Diego), Sarah Casewell (School of Physics and Astronomy, University of Leicester), Rocio Kiman (Kavli Institute for Theoretical Physics, University of California Santa Barbara), Emily Calamari (Department of Physics, Barnard College, Columbia University), Christian Aganze (Department of Physics, University of California San Diego), Chih-Chun Hsu (Department of Physics, University of California San Diego), Arttu Sainio (Backyard Worlds: Planet 9), Vinod Thakur (Backyard Worlds: Planet 9), and The Backyard Worlds: Planet 9 Collaboration.

NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O'odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

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Links

Research paper

American Museum of Natural History blog post

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Contacts:

Aaron Meisner
Astronomer
NSF’s NOIRLab
Cell: +1 650 714 8643
Email: aaron.meisner@noirlab.edu

Amanda Kocz
Communications Manager
NSF’s NOIRLab
Tel: +1 520 318 8591
Email: amanda.kocz@noirlab.edu

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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