NASA’s Webb Reveals Intricate Networks of Gas and Dust in Nearby Galaxies

NGC 1433 (MIRI Image)
Credits: Science: NASA, ESA, CSA, Janice Lee (NOIRLab)
Image Processing: Alyssa Pagan (STScI)

NGC 7496 (MIRI Image)
Science: NASA, ESA, CSA, Janice Lee (NOIRLab)
Image Processing: Joseph DePasquale (STScI)

NGC 1365 (MIRI Image)
Credits: Science: NASA, ESA, CSA, Janice Lee (NOIRLab)
Image Processing: Alyssa Pagan (STScI)

Release Images

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Researchers using NASA’s James Webb Space Telescope are getting their first look at star formation, gas, and dust in nearby galaxies with unprecedented resolution at infrared wavelengths. The data has enabled an initial collection of 21 research papers which provide new insight into how some of the smallest-scale processes in our universe – the beginnings of star formation – impact the evolution of the largest objects in our cosmos: galaxies.

The largest survey of nearby galaxies in Webb’s first year of science operations is being carried out by the Physics at High Angular resolution in Nearby Galaxies (PHANGS) collaboration, involving more than 100 researchers from around the globe. The Webb observations are led by Janice Lee, Gemini Observatory chief scientist at the National Science Foundation’s NOIRLab and affiliate astronomer at the University of Arizona in Tucson.

The team is studying a diverse sample of 19 spiral galaxies, and in Webb’s first few months of science operations, observations of five of those targets – M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433 – have taken place. The results are already astounding astronomers.

“The clarity with which we are seeing the fine structure certainly caught us by surprise,” said team member David Thilker of Johns Hopkins University in Baltimore, Maryland.

“We are directly seeing how the energy from the formation of young stars affects the gas around them, and it’s just remarkable,” said team member Erik Rosolowsky of the University of Alberta, Canada.

The images from Webb’s Mid-Infrared Instrument (MIRI) reveal the presence of a network of highly structured features within these galaxies – glowing cavities of dust and huge cavernous bubbles of gas that line the spiral arms. In some regions of the nearby galaxies observed, this web of features appears built from both individual and overlapping shells and bubbles where young stars are releasing energy.

“Areas which are completely dark in Hubble imaging light up in exquisite detail in these new infrared images, allowing us to study how the dust in the interstellar medium has absorbed the light from forming stars and emitted it back out in the infrared, illuminating an intricate network of gas and dust,” said team member Karin Sandstrom of the University of California, San Diego.

The high-resolution imaging needed to study these structures has long evaded astronomers – until Webb came into the picture. “The PHANGS team has spent years observing these galaxies at optical, radio, and ultraviolent wavelengths using NASA’s Hubble Space Telescope, the Atacama Large Millimeter/Submillimeter Array, and the Very Large Telescope’s Multi Unit Spectroscopic Explorer,” added team member Adam Leroy of the Ohio State University. “But, the earliest stages of a star’s lifecycle have remained out of view because the process is enshrouded within gas and dust clouds.”

Webb’s powerful infrared capabilities can pierce through the dust to connect the missing puzzle pieces.

For example, specific wavelengths observable by MIRI (7.7 and 11.3 microns) and Webb’s Near-Infrared Camera (3.3 microns) are sensitive to emission from polycyclic aromatic hydrocarbons, which play a critical role in the formation of stars and planets. These molecules were detected by Webb in the first observations by the PHANGS program.

Studying these interactions at the finest scale can help provide insights into the larger picture of how galaxies have evolved over time.

“Because these observations are taken as part of what's called a treasury program, they are available to the public as they are observed and received on Earth,” said Eva Schinnerer of the Max Planck Institute for Astronomy in Heidelberg, Germany, and leader of the PHANGS collaboration.

The PHANGS team will work to create and release data sets that align Webb’s data to each of the complementary data sets obtained previously from the other observatories, to help accelerate discovery by the broader astronomical community.

“Thanks to the telescope's resolution, for the first time we can conduct a complete census of star formation, and take inventories of the interstellar medium bubble structures in nearby galaxies beyond the Local Group,” Lee said. “That census will help us understand how star formation and its feedback imprint themselves on the interstellar medium, then give rise to the next generation of stars, or how it actually impedes the next generation of stars from being formed.”

The research by the PHANGS team is being conducted as part of General Observer program 2107. The team’s initial findings, comprised of 21 individual studies, were recently published in a special focus issue of The Astrophysical Journal Letters.

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).

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About This Release

Credits:

Media Contact:

Hannah Braun
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Science:

Janice Lee (NOIRLab), Eva Schinnerer

Permissions: Content Use Policy

Contact Us: Direct inquiries to the News Team.

Related Links and Documents:

• ApJL PHANGS Special Issue

Source: NASA's James Webb Space Telescope/News

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27 million galaxy morphologies quantified and cataloged with the help of machine learning

An image of NGC 1365 collected by the Dark Energy Survey. Also known as the Great Barred Spiral Galaxy, NGC 1365 is an example of a spiral galaxy and is located about 56 million light-years away. (Image: DECam, DES Collaboration) 

Using data from the Dark Energy Survey, researchers from the Department of Physics & Astronomy produced the largest catalog of galaxy morphology classifications to date. 

Research from Penn’s Department of Physics and Astronomy has produced the largest catalog of galaxy morphology classification to date. Led by former postdocs Jesús Vega-Ferrero and Helena Domínguez Sánchez, who worked with professor Mariangela Bernardi, this catalog of 27 million galaxy morphologies provides key insights into the evolution of the universe. The study was published in Monthly Notices of the Royal Astronomical Society.

The researchers used data from the Dark Energy Survey (DES), an international research program whose goal is to image one-eighth of the sky to better understand dark energy’s role in the accelerating expansion of the universe.

A byproduct of this survey is that the DES data contains many more images of distant galaxies than other surveys to date. “The DES images show us what galaxies looked like more than 6 billion years ago,” says Bernardi.

And because DES has millions of high-quality images of astronomical objects, it’s the perfect dataset for studying galaxy morphology. “Galaxy morphology is one of the key aspects of galaxy evolution. The shape and structure of galaxies has a lot of information about the way they were formed, and knowing their morphologies gives us clues as to the likely pathways for the formation of the galaxies,” Domínguez Sánchez says.

Previously, the researchers had published a morphological catalog for more than 600,000 galaxies from the Sloan Digital Sky Survey (SDSS). To do this, they developed a convolutional neural network, a type of machine learning algorithm, that was able to automatically categorize whether a galaxy belonged to one of two major groups: spiral galaxies, which have a rotating disk where new stars are born, and elliptical galaxies, which are larger, and made of older stars which move more randomly than their spiral counterparts.

But the catalog developed using the SDSS dataset was primarily made of bright, nearby galaxies, says Vega-Ferrero. In their latest study, the researchers wanted to refine their neural network model to be able to classify fainter, more distant galaxies. “We wanted to push the limits of morphological classification and trying to go beyond, to fainter objects or objects that are farther away,” Vega-Ferrero says.

To do this, the researchers first had to train their neural network model to be able to classify the more pixelated images from the DES dataset. They first created a training model with previously known morphological classifications, comprised of a set of 20,000 galaxies that overlapped between DES and SDSS. Then, they created simulated versions of new galaxies, mimicking what the images would look like if they were farther away using code developed by staff scientist Mike Jarvis.

Images of a simulated spiral (top) and elliptical galaxy at varying image quality and redshift levels, illustrating how fainter and more distant galaxies might look within the DES dataset. (Image: Jesus Vega-Ferrero and Helena Dominguez-Sanchez).  

Once the model was trained and validated on both simulated and real galaxies, it was applied to the DES dataset, and the resulting catalog of 27 million galaxies includes information on the probability of an individual galaxy being elliptical or spiral. The researchers also found that their neural network was 97% accurate at classifying galaxy morphology, even for galaxies that were too faint to classify by eye.

“We pushed the limits by three orders of magnitude, to objects that are 1,000 times fainter than the original ones,” Vega-Ferrero says. “That is why we were able to include so many more galaxies in the catalog.”

“Catalogs like this are important for studying galaxy formation,” Bernardi says about the significance of this latest publication. “This catalog will also be useful to see if the morphology and stellar populations tell similar stories about how galaxies formed.”

For the latter point, Domínguez Sánchez is currently combining their morphological estimates with measures of the chemical composition, age, star-formation rate, mass, and distance of the same galaxies. Incorporating this information will allow the researchers to better study the relationship between galaxy morphology and star formation, work that will be crucial for a deeper understanding of galaxy evolution.

Bernardi says that there are a number of open questions about galaxy evolution that both this new catalog, and the methods developed to create it, can help address. The upcoming LSST/Rubin survey, for example, will use similar photometry methods to DES but will have the capability of imaging even more distant objects, providing an opportunity to gain even deeper understanding of the evolution of the universe.

Mariangela Bernardi is a professor in the Department of Physics and Astronomy in the School of Arts & Sciences at the University of Pennsylvania.

Helena Domínguez Sánchez is a former Penn postdoc and is currently a postdoctoral fellow at Instituto de Ciencias del Espacio (ICE), which is part of the Consejo Superior de Investigaciones Científicas (CSIC).

Jesús Vega Ferrero is a former Penn postdoc and currently a postdoctoral researcher at the Instituto de Física de Cantabria (IFCA), which is part of the Consejo Superior de Investigaciones Científicas (CSIC).

The Dark Energy Survey is supported by funding from the Department of Energy’s Fermi National Accelerator Laboratory, the National Center for Supercomputing Applications, and the National Science Foundation’s NOIRLab. A complete list of funding organizations and collaborating institutions is at The Dark Energy Survey website.

This research was supported by NSF Grant AST-1816330.

 

Source: Penn Today, University of Pennsylvania

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New Hubble Constant Measurement Adds to Mystery of Universe's Expansion Rate

Galaxies Used to Refine the Hubble Constant

Credit: NASA, ESA, W. Freedman (University of Chicago), ESO, and the Digitized Sky Survey

Release Images

Astronomers have made a new measurement of how fast the universe is expanding, using an entirely different kind of star than previous endeavors. The revised measurement, which comes from NASA's Hubble Space Telescope, falls in the center of a hotly debated question in astrophysics that may lead to a new interpretation of the universe's fundamental properties.

Scientists have known for almost a century that the universe is expanding, meaning the distance between galaxies across the universe is becoming ever more vast every second. But exactly how fast space is stretching, a value known as the Hubble constant, has remained stubbornly elusive.

Now, University of Chicago professor Wendy Freedman and colleagues have a new measurement for the rate of expansion in the modern universe, suggesting the space between galaxies is stretching faster than scientists would expect. Freedman's is one of several recent studies that point to a nagging discrepancy between modern expansion measurements and predictions based on the universe as it was more than 13 billion years ago, as measured by the European Space Agency's Planck satellite.

As more research points to a discrepancy between predictions and observations, scientists are considering whether they may need to come up with a new model for the underlying physics of the universe in order to explain it. 

"The Hubble constant is the cosmological parameter that sets the absolute scale, size and age of the universe; it is one of the most direct ways we have of quantifying how the universe evolves," said Freedman. "The discrepancy that we saw before has not gone away, but this new evidence suggests that the jury is still out on whether there is an immediate and compelling reason to believe that there is something fundamentally flawed in our current model of the universe.”

In a new paper accepted for publication in The Astrophysical Journal, Freedman and her team announced a new measurement of the Hubble constant using a kind of star known as a red giant. Their new observations, made using Hubble, indicate that the expansion rate for the nearby universe is just under 70 kilometers per second per megaparsec (km/sec/Mpc). One parsec is equivalent to 3.26 light-years distance.

This measurement is slightly smaller than the value of 74 km/sec/Mpc recently reported by the Hubble SH0ES (Supernovae H₀ for the Equation of State) team using Cepheid variables, which are stars that pulse at regular intervals that correspond to their peak brightness. This team, led by Adam Riess of the Johns Hopkins University and Space Telescope Science Institute, Baltimore, Maryland, recently reported refining their observations to the highest precision to date for their Cepheid distance measurement technique.

How to Measure Expansion

A central challenge in measuring the universe's expansion rate is that it is very difficult to accurately calculate distances to distant objects.

In 2001, Freedman led a team that used distant stars to make a landmark measurement of the Hubble constant. The Hubble Space Telescope Key Project team measured the value using Cepheid variables as distance markers. Their program concluded that the value of the Hubble constant for our universe was 72 km/sec/Mpc.

But more recently, scientists took a very different approach: building a model based on the rippling structure of light left over from the big bang, which is called the Cosmic Microwave Background. The Planck measurements allow scientists to predict how the early universe would likely have evolved into the expansion rate astronomers can measure today. Scientists calculated a value of 67.4 km/sec/Mpc, in significant disagreement with the rate of 74.0 km/sec/Mpc measured with Cepheid stars.

Astronomers have looked for anything that might be causing the mismatch. "Naturally, questions arise as to whether the discrepancy is coming from some aspect that astronomers don't yet understand about the stars we're measuring, or whether our cosmological model of the universe is still incomplete," Freedman said. "Or maybe both need to be improved upon."

Freedman's team sought to check their results by establishing a new and entirely independent path to the Hubble constant using an entirely different kind of star.

Certain stars end their lives as a very luminous kind of star called a red giant, a stage of evolution that our own Sun will experience billions of years from now. At a certain point, the star undergoes a catastrophic event called a helium flash, in which the temperature rises to about 100 million degrees and the structure of the star is rearranged, which ultimately dramatically decreases its luminosity. 

Astronomers can measure the apparent brightness of the red giant stars at this stage in different galaxies, and they can use this as a way to tell their distance.

The Hubble constant is calculated by comparing distance values to the apparent recessional velocity of the target galaxies — that is, how fast galaxies seem to be moving away. The team's calculations give a Hubble constant of 69.8 km/sec/Mpc — straddling the values derived by the Planck and Riess teams.

"Our initial thought was that if there's a problem to be resolved between the Cepheids and the Cosmic Microwave Background, then the red giant method can be the tie-breaker," said Freedman.

But the results do not appear to strongly favor one answer over the other say the researchers, although they align more closely with the Planck results.

NASA's upcoming mission, the Wide Field Infrared Survey Telescope (WFIRST), scheduled to launch in the mid-2020s, will enable astronomers to better explore the value of the Hubble constant across cosmic time. WFIRST, with its Hubble-like resolution and 100 times greater view of the sky, will provide a wealth of new Type Ia supernovae, Cepheid variables, and red giant stars to fundamentally improve distance measurements to galaxies near and far.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Source: HubbleSite/News

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Contact:  

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Louise Lerner
University of Chicago, Chicago, Illinois
773-702-8366
louise@uchicago.edu

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Related Links:

• The science paper by W. Freedman et al.
• University of Chicago's Release
• Carnegie's Release
• NASA's Hubble portal
• NASA SMD's ScienceCast (Sept. 20, 2017): "Hubble's Contentious Constant"
• Freedman's science paper on astro-pH

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Inside the Fiery Furnace

PR Image eso1612a

VST image of the Fornax Galaxy Cluster

PR Image eso1612b

Finding Chart for the Fornax Galaxy Cluster

PR Image eso1612c

The location of the Fornax Galaxy Cluster

PR Image eso1612d

Wide-field view of the Fornax Galaxy Cluster

Videos
 

PR Video eso1612a

Zooming in on the Fornax Galaxy cluster

PR Video eso1612b

VST image of the Fornax Galaxy Cluster

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VLT Survey Telescope Captures the Fornax Cluster

This new image from the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile captures a spectacular concentration of galaxies known as the Fornax Cluster, which can be found in the southern hemisphere constellation of Fornax (The Furnace). The cluster plays host to a menagerie of galaxies of all shapes and sizes, some of which are hiding secrets.

Galaxies, it seems, are sociable animals and they like to gather together in large groups, known as clusters. Actually it’s gravity that holds the galaxies in the cluster close together as a single entity, with the pull of gravity arising from large amounts of dark matter, as well as from the galaxies we can see. Clusters can contain anything between about 100 and 1000 galaxies and can be between about 5 and 30 million light-years across.

Galaxy clusters do not come in neatly defined shapes so it is difficult to determine exactly where they begin and end. However, astronomers have estimated that the centre of the Fornax Cluster is in the region of 65 million light-years from Earth. What is more accurately known is that it contains nearly sixty large galaxies, and a similar number of smaller dwarf galaxies. Galaxy clusters like this one are commonplace in the Universe and illustrate the powerful influence of gravity over large distances as it draws together the enormous masses of individual galaxies into one region.

At the centre of this particular cluster, in the middle of the three bright fuzzy blobs on the left side of the image, is what is known as a cD galaxy — a galactic cannibal. cD galaxies like this one, called NGC 1399, look similar to elliptical galaxies but are bigger and have extended, faint envelopes [1]. This is because they have grown by swallowing smaller galaxies drawn by gravity towards the centre of the cluster [2].

Indeed, there is evidence that this process is happening before our eyes — if you look closely enough. Recent work by a team of astronomers led by Enrichetta Iodice (INAF – Osservatorio di Capodimonte, Naples, Italy)  [3], using data from ESO’s VST, has revealed a very faint bridge of light between NGC 1399 and the smaller galaxy NGC 1387 to its right. This bridge, which has not been seen before (and is too faint to show up in this picture), is somewhat bluer than either galaxy, indicating that it consists of stars created in gas that was drawn away from NGC 1387 by the gravitational pull of NGC 1399. Despite there being little evidence for ongoing interactions in the Fornax Cluster overall, it seems that NGC 1399 at least is still feeding on its neighbours.

Towards the bottom right of this image is the large barred spiral galaxy NGC 1365. This is a striking example of its type, the prominent bar passing through the central core of the galaxy, and the spiral arms emerging from the ends of the bar. In keeping with the nature of cluster galaxies, there is more to NGC 1365 than meets the eye. It is classified as a Seyfert Galaxy, with a bright active galactic nucleus also containing a supermassive black hole at its centre.

This spectacular image was taken by the VLT Survey Telescope (VST) at ESO’s Paranal Observatory in Chile. At 2.6 metres in diameter, the VST is by no means a large telescope by today’s standards, but it has been designed specifically to conduct large-scale surveys of the sky. What sets it apart is its huge corrected field of view and 256-megapixel camera, called OmegaCAM, which was specially developed for surveying the sky. With this camera the VST can produce deep images of large areas of sky quickly, leaving the really big telescopes — like ESO’s Very Large Telescope (VLT) — to explore the details of individual objects.

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Notes

[1] The image captures only the central regions of the Fornax Cluster; it extends over a larger region of sky.

[2] The central galaxy is often the brightest galaxy in a cluster, but in this case the brightest galaxy, NGC 1316, is situated at the edge of the cluster, just outside the area covered by this image. Also known as Fornax A, it is one of the most powerful sources of radio waves in the sky. The radio waves, which can be seen by specialised telescopes sensitive to this kind of radiation, emanate from two enormous lobes extending far into space either side of the visible galaxy. The energy that powers the radio emission comes from a supermassive black hole lurking at the centre of the galaxy which is emitting two opposing jets of high-energy particles. These jets produce the radio waves when they plough into the rarefied gas which occupies the space between galaxies in the cluster.

[3] “The Fornax Deep Survey with VST. I. The extended and diffuse stellar halo of NGC1399 out to 192 kpc” by E. Iodice, M. Capaccioli , A. Grado , L. Limatola, M. Spavone, N.R. Napolitano, M. Paolillo, R. F. Peletier, M. Cantiello, T. Lisker, C. Wittmann, A. Venhola , M. Hilker , R. D’Abrusco, V. Pota, and P. Schipani has been published in the Astrophysical Journal.

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More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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Links

• Research paper
• Photos of the VST
• Press releases involving the VST

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Contacts

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

 Source: ESO

When did galaxies settle down?

A Hubble Space Telescope image of a spiral galaxy seen when the Universe was less than a third of its current age, yet showing the same barred feature as much older, settled disk galaxies. Credit: NASA, ESA, J. Kartaltepe (NOAO), C. Lintott (Oxford), H. Ferguson (STScI), S. Faber (UCO).

A European Southern Observatory image of the barred spiral galaxy NGC 1365, rotated to match the orientation of the first image. NGC 1365 is about 56 million light years away, so we see it as it appears 56 million years ago, or 10 billion years later than the galaxy in the HST image. Credit: ESO/IDA/Danish 1.5 m/ R. Gendler, J-E. Ovaldsen, C. Thöne, and C. Feron.

Astronomers have long sought to understand exactly how the universe evolved from its earliest history to the cosmos we see around us in the present day. In particular, the way that galaxies form and develop is still a matter for debate. Now a group of researchers have used the collective efforts of the hundreds of thousands of people that volunteer for the Galaxy Zoo project to shed some light on this problem. They find that galaxies may have settled into their current form some two billion years earlier than previously thought.

Dr Brooke Simmons of the University of Oxford and her collaborators describe the work in a paper in Monthly Notices of the Royal Astronomical Society. The team set Zoo volunteers the task of classifying the shapes of tens of thousands of galaxies observed by the Hubble Space Telescope. These objects are typically very distant, so we see them as they appeared more than 10 billion years ago, when the universe was about 3 billion years old, less than a quarter of its present age.

The newly classified galaxies are striking in that they look a lot like those in today’s universe, with disks, bars and spiral arms. But theorists predict that these should have taken another 2 billion years to begin to form, so things seem to have been settling down a lot earlier than expected.

Brooke comments: “When we started looking for these galaxies, we didn't really know what we'd find. We had predictions from galaxy simulations that we shouldn't find any of the barred features that we see in nearby, evolved galaxies, because very young galaxies might be too agitated for them to form.”

‘But we now know that isn't the case. With the public helping us search through many thousands of images of distant galaxies, we discovered that some galaxies settle very early on in the Universe.”

Media contact

Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307 / 4582
Mob: +44 (0)794 124 8035
rm@ras.org.uk

Science contact

Dr Brooke Simmons
University of Oxford
Tel: +44 (0)1865 273637
brooke.simmons@astro.ox.ac.uk

 

Further information

The new work appears in “Galaxy Zoo: CANDELS Barred Disks and Bar Fractions”, B. D. Simmons et al, Monthly Notices of the Royal Astronomical Society, Oxford University Press, 445, pp. 3466-3474.

A preprint of the paper is available on the arXivv

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 organizes scientific meetings, publishes international research and review journals, recognizes 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 3800 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Follow the RAS on Twitter

 

Spinning Black Holes in Galactic Nuclei

An image of the galaxy NGC 1365, whose nucleus contains a massive black hole actively accreting material. Astronomers have used a series of X-ray observations to measure time variations in the iron emission line from the nucleus and thereby determine the value of the black hole's spin. Credit & Copyright:  SSRO-South (R. Gilbert, D. Goldman, J. Harvey, D. Verschatse) - PROMPT (D. Reichart) 

The nuclei of most galaxies contain a massive black hole. In our Milky Way, for example, the nuclear black hole contains about four million solar masses of material, and in other galaxies the black holes are estimated to have masses of hundreds of millions of suns, or even more. In dramatic cases, like quasars, these black holes are suspected of driving the observed bipolar jets of particles outward at nearly the speed of light. How they do this is not known, but scientists think that the spin of the black hole somehow plays a pivotal role.

A black hole is so simple (at least in traditional theories) that it can be completely described by just three parameters: its mass, its spin, and its electric charge. Even though it may have formed out of a complex mix of matter and energy, all the other specific details are lost when it collapses to a singular point. Astronomers are working to measure the spins of black hole in active galaxies in order to probe the connections between spin and jet properties.

One method for measuring black hole spin is X-ray spectra, by looking for distortions in the atomic emission line shapes from the very hot gas in the accreting disk of material around the black hole. Effects due to relativity in these extreme environments can broaden and skew intrinsically narrow emission lines into characteristic profiles that depend on the black hole spin value.

CfA astronomers Guido Risaliti, Laura Brenneman, and Martin Elvis, together with their colleagues, used joint observations from the NuSTAR and XMM-NEWTON space missions to examine the time-varying spectral shape of highly excited iron atoms in the nucleus of the galaxy NGC 1365, a well-studied active galaxy about sixty-six million light-years away and known for exhibiting time-variable line profiles. The team obtained four high quality observations of the source, catching it over an unprecedented range of absorption states, including one with very little line-of-sight absorption to the central nucleus. All the observations, despite the range of absorptions, displayed hallmarks of the innermost regions of the accretion flow. There have been disagreements within the community about the reliability of attributing observed line shapes to the black hole spin (rather than to other effects in the nucleus), but this new result not only demonstrates that it is possible, it shows that even single-epoch observations are likely to provide reliable measurements, making the task of studying other such systems more efficient.

Reference(s): 

"NuSTAR AND XMM-NEWTON Observations of NGC 1365: Extreme Absorption Variability and a Constant Inner Accretion Disk," D. J. Walton, G. Risaliti, F. A. Harrison, A. C. Fabian, J. M. Miller, P. Arevalo, D. R. Ballantyne, S. E. Boggs, L. W. Brenneman, F. E. Christensen, W. W. Craig, M. Elvis, F. Fuerst, P. Gandhi, B. W. Grefenstette C. J. Hailey, E. Kara, B. Luo, K. K. Madsen, A. Marinucci, G. Matt, M. L. Parker, C. S. Reynolds, E. Rivers, R. R. Ross, D. Stern, and W. W. Zhang, ApJ, 788,76, 2014

Source: Smithsonian Astrophysical Observatory

The Rise and Fall of a Supernova

 

NGC 1365 and SN 2012fr

Credit: ESO/IRAP-CNRS-UPS/A.Klotz

An unusual new video sequence shows the rapid brightening and slower fading of a supernova explosion in the galaxy NGC 1365. The supernova, which has been named SN 2012fr, was discovered by French astronomer Alain Klotz on the 27 October 2012. The images captured by the small TAROT robotic telescope, located at ESO’s La Silla Observatory in Chile, have been compiled to create this unique movie.

Supernovae are the results of the explosive and cataclysmic deaths of certain types of stars. They are so brilliant that they can outshine their entire parent galaxy for many weeks before slowly fading from sight.

The supernova 2012fr [1] was discovered by Alain Klotz on the afternoon of 27 October 2012. He was busy measuring the brightness of a faint variable star in an image from the TAROT (Télescope à Action Rapide pour les Objets Transitoires) robotic telescope at ESO’s La Silla Observatory, when he noticed a new object that was not present in an image taken three days earlier. After checking with telescopes and astronomers all across the world the bright object was confirmed to be a Type Ia supernova.

Some stars co-habit with a second star, both orbiting around a common centre of gravity. In some cases one of them might be a very old white dwarf that is stealing material from its companion. At some point the white dwarf has siphoned off so much matter from its companion that it becomes unstable and explodes. This is known as a Type Ia supernova.

This kind of supernova has become very important as they are the most reliable way of measuring distances to very remote galaxies in the early Universe. Beyond the local group of galaxies, astronomers needed to find very bright objects with predictable properties that could act as signposts to help them map out the expansion history of the Universe. Type Ia supernovae are ideal as their brightnesses peak and fade in almost the same way for each explosion. Measurements of the distances to Type Ia supernovae led to the discovery of the accelerating expansion of the Universe, work that was awarded the Nobel Prize for Physics in 2011.

The host galaxy of this supernova is NGC 1365 (see also potw1037a), an elegant barred spiral galaxy, located 60 million light-years away towards the constellation of Fornax (The Furnace). With its diameter of about 200 000 light-years, it stands out among the other galaxies in the Fornax cluster. A colossal straight bar runs through the galaxy, containing the nucleus at the centre. The new supernova can be easily spotted just above the core, in the middle of the image.

Astronomers discovered more than 200 new supernovae in 2012, of which SN 2012fr is among the brightest. The supernova was first spotted when it was very faint on the 27 October 2012, and it reached its peak brightness on 11 November 2012 [2]. It was then easily seen as a faint star through a medium-sized amateur telescope. The video was compiled from a series of images taken of the galaxy over a period of three months, from the discovery in October until mid-January 2013.

TAROT is a 25-centimetre optical robotic telescope, able to move very fast, and to start an observation within a second. It was installed at La Silla Observatory in 2006 with the purpose of detecting cosmic gamma-ray bursts. The images that revealed SN 2012fr were captured using blue, green and red filters.

Notes

[1] Supernovae are designated by the year in which they are discovered, and the order in which they are discovered during that year, by using letters of the alphabet. The fact that the the supernova was discovered by a French team and it has been designated by the letters “fr” is pure coincidence.

[2] At this time it was magnitude 11.9. This is about 200 times too faint to see with the unaided eye even on a clear and dark night. But if the supernova at its peak brightness and our star the Sun were seen together at the same distance from the observer the supernova would appear about 3000 million times brighter than the Sun.

Links

• Video: TAROT discovers a bright supernova in NGC 1365
• Video: TAROT discovers a bright supernova in NGC 1365 (excerpt)

Contacts

Alain Klotz
Institut de Recherche en Astrophysique et Planetologie
Toulouse, France
Tel: +33 05 61 55 66 66
Email: alain.klotz@irap.omp.eu

Richard Hook
ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO

Speedy Black Hole Holds Galaxy's History

 Rapidly rotating black hole accreting matter

ESA’s XMM-Newton and NASA’s NuSTAR have detected a rapidly rotating supermassive black hole in the heart of spiral galaxy NGC 1365. The rate at which a black hole spins encodes the history of its formation. An extremely rapid rotation could result from either a steady and uniform flow of matter spiralling in via an accretion disc (as shown in this artist impression) or as a result of the merger of two galaxies and their smaller black holes.

Also depicted in this image is an outflowing jet of energetic particles, believed to be powered by the black hole’s spin. The regions near black holes contain compact sources of high energy X-ray radiation thought, in some scenarios, to originate from the base of these jets. The nature of the X-ray emission enables astronomers to see how fast matter is swirling in the inner region of the disc, and ultimately to measure the black hole's spin rate. Download Hi-Res (955.29 kB)

A rapidly rotating supermassive black hole has been found in the heart of a spiral galaxy by ESA’s XMM-Newton and NASA’s NuSTAR space observatories, opening a new window into how galaxies grow.

Supermassive black holes are thought to lurk in the centre of almost all large galaxies, and scientists believe that the evolution of a galaxy is inextricably linked with the evolution of its black hole. 

How fast a black hole spins is thought to reflect the history of its formation. In this picture, a black hole that grows steadily, fed by a uniform flow of matter spiralling in, should end up spinning rapidly. Rapid rotation could also be the result of two smaller black holes merging.  

On the other hand, a black hole buffeted by small clumps of material hitting from all directions will end up rotating relatively slowly. 

These scenarios mirror the formation of the galaxy itself, since a fraction of all the matter drawn into the galaxy finds its way into the black hole. Because of this, astronomers are keen to measure the spin rates of black holes in the hearts of galaxies. 

One way of doing so is to observe X-rays emitted just outside the ‘event horizon’, the boundary surrounding a black hole beyond which nothing, including light, can escape. 

In particular, hot iron atoms produce a strong signature of X-rays at a specific energy, which is smeared out by the rotation of the black hole. The nature of this smearing can then be used to infer the spin rate. 

Using this technique, previous observations have suggested there are extremely rapidly spinning black holes in some galaxies. However, confirming the spin rate has been very difficult, because the X-ray spectrum can also be smeared out by absorbing clouds of gas lying close to the disc. Until now, telling the two scenarios apart has been impossible. 

For roughly 36 hours in July 2012, ESA’s XMM-Newton and NASA’s NuSTAR – the Nuclear Spectroscopic Telescope Array – simultaneously observed the spiral galaxy NGC 1365. XMM-Newton captured the lower energy X-rays, NuSTAR the higher energy data. 

The combined data proved to be key to unlocking the puzzle. A spinning black hole model makes a clear prediction for the ratio of high-energy to low-energy X-rays. The same is true for an absorbing cloud of gas. 

But importantly, the predictions are different and the new data agree only with a rapidly spinning black hole. This suggests that the galaxy has grown steadily with time, with material streaming uniformly into the central black hole. 

However, astronomers cannot yet rule out a single large event where two galaxies and their black holes subsequently merged, producing a sudden acceleration of the resulting supermassive black hole. 

“But we can completely rule out the absorption model,” says Guido Risaliti, INAF – Osservatorio Astrofisico di Arcetri, Italy, who led the investigation. 

“Now that we know how to measure black hole spin rates for certain, we can more confidently use them to infer the evolution of their host galaxies.”

Measuring black hole spins also provides a new way to test general relativity. Published in 1915, general relativity is Albert Einstein’s description of gravity. It predicts effects that are most easily seen in extremely strong gravitational fields, such as those found near black holes, and NGC 1365’s black hole is spinning almost as fast as Einstein's theory of gravity will allow. 

“Both physics and astrophysics benefit from this result,’ says Dr Risaliti, who is already applying the X-ray measurement technique to different galaxies. 

“The result is a great example of the synergy that can be achieved when complementary space missions are used together. It would have been impossible to achieve this work without the two spacecraft working in tandem,” says Norbert Schartel, ESA XMM-Newton project scientist.

 

Notes for Editors

 

“A rapidly spinning supermassive black hole at the centre of NGC 1365” by G. Risaliti et al. is published in Nature 28 February 2013; doi:10.1038/nature11938.

The European Space Agency's X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. It is the biggest scientific satellite to have been built in Europe and uses over 170 wafer-thin cylindrical mirrors spread over three high throughput X-ray telescopes. Its mirrors are among the most powerful ever developed. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects. The scientific community can apply for observing time on XMM-Newton on a competitive basis. 

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. 

For further information, please contact:
 
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int

Guido Risaliti
INAF–Osservatorio Astrofisico di Arcetri
Tel: +39 055 2752286
Email: risaliti@arcetri.astro.it

Norbert Schartel
ESA XMM-Newton Project Scientist
Tel: +34 91 8131 184
Email: norbert.schartel@esa.int

An Elegant Galaxy in an Unusual Light

PR Image eso1038a
HAWK-I infrared image of the spectacular barred spiral galaxy NGC 1365

PR Image eso1038b

Comparison of visible-light and infrared images of the galaxy NGC 1365

PR Image eso1038c
NGC 1365 in the constellation of Fornax

PR Video eso1038a

Zooming in on the HAWK-I infrared image of the spectacular barred spiral galaxy NGC 1365

PR Video eso1038b

Visible/infrared cross-fade of images of the spectacular barred spiral galaxy NGC 1365

A new image taken with the powerful HAWK-I camera on ESO’s Very Large Telescope at Paranal Observatory in Chile shows the beautiful barred spiral galaxy NGC 1365 in infrared light. NGC 1365 is a member of the Fornax cluster of galaxies, and lies about 60 million light-years from Earth.

NGC 1365 is one of the best known and most studied barred spiral galaxies and is sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form, with the straight bar and two very prominent outer spiral arms. Closer to the centre there is also a second spiral structure and the whole galaxy is laced with delicate dust lanes.

This galaxy is an excellent laboratory for astronomers to study how spiral galaxies form and evolve. The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images in visible light (potw1037a) and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms. These data were acquired to help astronomers understand the complex flow of material within the galaxy and how it affects the reservoirs of gas from which new stars can form. The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas is compressed and star formation is triggered. Many huge young star clusters trace out the main spiral arms and each contains hundreds or thousands of bright young stars that are less than ten million years old. The galaxy is too remote for single stars to be seen in this image and most of the tiny clumps visible in the picture are really star clusters. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year.

While the bar of the galaxy consists mainly of older stars long past their prime, many new stars are born in stellar nurseries of gas and dust in the inner spiral close to the nucleus. The bar also funnels gas and dust gravitationally into the very centre of the galaxy, where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars.

NGC 1365, including its two huge outer spiral arms, spreads over around 200 000 light-years. Different parts of the galaxy take different times to make a full rotation around the core of the galaxy, with the outer parts of the bar completing one circuit in about 350 million years. NGC 1365 and other galaxies of its type have come to more prominence in recent years with new observations indicating that the Milky Way could also be a barred spiral galaxy. Such galaxies are quite common — two thirds of spiral galaxies are barred according to recent estimates, and studying others can help astronomers understand our own galactic home.

More information

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

NGC 1365 in visible light

Contacts

Richard Hook
ESO Paranal/La SiIlla and E-ELT Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Email: rhook@eso.org