Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA)— an international observatory co-operated by the US National Science Foundation’s National Radio Astronomy Observatory (NRAO)—have observed a significant amount of cold, neutral gas in the outer regions of the young galaxyGalaxyA large body of gas, dust, stars, and their companions (Planets, asteroids, moons, etc.) held together by their mutual gravitational attraction. They are grouped into three main categories: spiral galaxies, elliptical galaxies, and irregular galaxies. (see below) Another class of galaxies is peculiar galaxies, which are thought to be distorted versions of normal galaxies. A1689-zD1, as well as outflows of hot gas coming from the galaxy’s center. These results may shed light on a critical stage of galactic evolution for early galaxies, where young galaxies begin the transformation to be increasingly like their later, more structured cousins. The observations were presented today in a press conference at the 240th meeting of the American Astronomical Society (AAS) in Pasadena, California, and will be published in an upcoming edition of The Astrophysical Journal (ApJ). 

A1689-zD1— a young, active, star-forming galaxy that is slightly less luminous and less massive than the Milky Way— is located roughly 13 billion light-yearsLight-yearsThe distance that light travels in one year in a vacuum. One light year is equivalent to about six trillion miles. away from Earth in the Virgo constellation cluster. It was discovered hiding out behind the Abell 1689 galaxy cluster in 2007 and confirmed in 2015 thanks to gravitational lensing, which amplified the brightness of the young galaxy by more than 9x. Since then, scientists have continued to study the galaxy as a possible analog for the evolution of other “normal” galaxies. That label— normal— is an important distinction that has helped researchers divide A1689-zD1’s behaviors and characteristics into two buckets: typical and uncommon, with the uncommon characteristics mimicking those of later and more massive galaxies.

“A1689-zD1 is located in the very early Universe— only 700 million years after the Big Bang. This is the era where galaxies were just beginning to form,” said Hollis Akins, an undergraduate student in astronomy at Grinnell College and the lead author of the research. “What we’re seeing in these new observations is evidence of processes that may contribute to the evolution of what we call normal galaxies as opposed to massive galaxies. More importantly, these processes are ones we did not previously believe applied to these normal galaxies.”

One of these uncommon processes is the galaxy’s production and distribution of star-forming fuel, and potentially a lot of it. The team used ALMA’s highly-sensitive Band 6 receiver to home in on a halo of carbon gas that extends far beyond the center of the young galaxy. This could be evidence of ongoing star formation in the same region or the result of structural disruptions, such as mergers or outflows, in the earliest stages of the galaxy’s formation. 

According to Akins, this is unusual for early galaxies. “The carbon gas we observed in this galaxy is typically found in the same regions as neutral hydrogen gas, which is also where new stars tend to form. If that is the case with A1689-zD1, the galaxy is likely much larger than previously thought. It’s also possible that this halo is a remnant of previous galactic activity, like mergers that exerted complex gravitational forces on the galaxy leading to the ejection of a lot of neutral gas out to these large distances. In either case, the early evolution of this galaxy was likely active and dynamic, and we’re learning that this may be a common, although previously unobserved, theme in early galaxy formation.”

More than just uncommon, the discovery could have significant implications for the study of galactic evolution, particularly as radio observations uncover details unseen at optical wavelengths. Seiji Fujimoto, a postdoctoral researcher at the Niels Bohr Institute’s Cosmic Dawn Center, and a co-author of the research said, “The emission from the carbon gas in A1689-zD1 is much more extended than what was observed with Hubble Space Telescope, and this could mean that early galaxies are not as small as they appear. If, in fact, early galaxies are larger than we previously believed this would have a major impact on the theory of galaxy formation and evolution in the early Universe.” 

Led by Akins, the team also observed outflows of hot, ionized gas— commonly caused by violent galactic activity like supernovae—  pushing outward from the center of the galaxy. It’s possible, given their potentially explosive nature, that the outflows have something to do with the carbon halo. “Outflows occur as a result of violent activity, such as the explosion of supernovae— which blast nearby gaseous material out of the galaxy— or black holes in the centers of galaxies— which have strong magnetic effects that can eject material in powerful jets. Because of this, there’s a strong possibility that the hot outflows have something to do with the presence of the cold carbon halo,” said Akins. “And that further highlights the importance of the multiphase, or hot to cold, nature of the outflowing gas.”

Darach Watson, an associate professor at the Niels Bohr Institute’s Cosmic Dawn Center, and co-author of the new research confirmed A1689-zD1 as a high-redshift galaxy in 2015, making it the most distant dusty galaxy known. “We have seen this type of extended gas halo emission from galaxies that formed later in the Universe, but seeing it in such an early galaxy means that this type of behavior is universal even in the more modest galaxies that formed most of the stars in the early Universe. Understanding how these processes occurred in such a young galaxy is critical to understanding how star-formation happens in the early Universe.”

Kirsten Knudsen, a professor of astrophysics in the Department of Space, Earth, and Environment at Chalmers University of Technology, and co-author of the research found evidence of A1689-zD1’s dust continuum in 2017. Knudsen pointed out the serendipitous role of extreme gravitational lensing in making each new discovery in the research possible. “Because A1689-zD1 is magnified more than nine times, we can see critical details that are otherwise difficult to observe in ordinary observations of such distant galaxies. Ultimately, what we’re seeing here is that early Universe galaxies are very complex, and this galaxy will continue to present new research challenges and results for some time.” 

Dr. Joe Pesce, NSF program officer for ALMA, added, “This fascinating ALMA research adds to a growing body of results indicating that things aren’t quite as we expected in the early Universe, but they are really interesting and exciting nonetheless!”

Spectroscopy and infrared observations of A1689-zD1 are planned for January 2023, using the NIRSpec Integral Field Unit (IFU) and NIRCam on the James Webb Space Telescope. The new observations will complement previous HST and ALMA data, offering a deeper and more complete multi-wavelength look at the young galaxy. 

Resource

“ALMA reveals extended cool gas and hot ionized out in a typical star-forming galaxy at z = 7.13,” Akins et al, The Astrophysical Journal.

Press Conference Access and Recording

Tuesday, June 14th, 2022 @ 2:15pm PT — Galactic Neighbors, Insights From ALMA, and a Record-Breaking Star

“ALMA Reveals Extended Cool Gas and Hot Ionized Outflows in a Distant Star-Forming Galaxy”

About NRAO

The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA

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

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

Media Contact:

Amy C. Oliver
Public Information Officer, ALMA
Public Information & News Manager, NRAO
+1 434 242 9584
aoliver@nrao.edu

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Three Decades of Space Telescope Observations Converge on a Precise Value for the Hubble Constant

At simultaneous press conferences around the world, including at a National Science Foundation-sponsored press conference at the US National Press Club in Washington, D.C., astronomers have unveiled the first image of the supermassive black hole at the center of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings of such giants, which are thought to reside at the center of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes.

The image is a long-anticipated look at the massive object that sits at the very center of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the center of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) — is a black hole, and today’s image provides the first direct visual evidence of it.

Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.

“We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity,” said EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “These unprecedented observations have greatly improved our understanding of what happens at the very center of our galaxy, and offer new insights on how these giant black holes interact with their surroundings.” The EHT team’s results are being published today in a special issue of The Astrophysical Journal Letters.

Because the black hole is about 27,000 light-years away from Earth, it appears to us to have about the same size in the sky as a donut on the Moon. To image it, the team created the powerful EHT, which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope [1]. The EHT observed Sgr A* on multiple nights, collecting data for many hours in a row, similar to using a long exposure time on a camera.

And just like a high-powered camera, imaging Sgr A* required the support of the most sensitive instruments in radio astronomy. That sensitivity comes from the 1.3mm Band 6 receivers on the Atacama Large Millimeter/submillimeter Array (ALMA), designed by the Central Development Laboratory (CDL) at the US National Science Foundation’s National Radio Astronomy Observatory (NRAO).

“We are very proud at CDL to have provided some critical technology to support this amazing discovery by the EHT collaboration,” said Bert Hawkins, Director of CDL, who explained the role of Band 6 and CDL in making the research and the results possible. “Our team contributed by installing a custom-built atomic clock on ALMA and reprogramming the ALMA correlator to make the telescope a phased array. This effectively turned the telescope into a single dish with an effective diameter of 85 meters– the largest component on the EHT. In addition, the mixers at the heart of the receivers on ALMA, the Submillimeter Telescope (SMT) in Arizona, the Large Millimeter Telescope (LMT) in Mexico, and the South Pole Telescope (SPT) in Antarctica were developed at CDL along with our partners at the University of Virginia.”

The breakthrough follows the EHT collaboration’s 2019 release of the first image of a black hole, called M87*, at the center of the more distant Messier 87 galaxy.

The two black holes look remarkably similar, even though our galaxy’s black hole is more than a thousand times smaller and less massive than M87* [2]. “We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar,” says Sera Markoff, Co-Chair of the EHT Science Council and a professor of theoretical astrophysics at the University of Amsterdam, the Netherlands. “This tells us that General Relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes.”

This achievement was considerably more difficult than for M87*, even though Sgr A* is much closer to us. EHT scientist Chi-kwan (‘CK’) Chan, from Steward Observatory and Department of Astronomy and the Data Science Institute of the University of Arizona, US, explains: “The gas in the vicinity of the black holes moves at the same speed — nearly as fast as light — around both Sgr A* and M87*. But where gas takes days to weeks to orbit the larger M87*, in the much smaller Sgr A* it completes an orbit in mere minutes. This means the brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT Collaboration was observing it — a bit like trying to take a clear picture of a puppy quickly chasing its tail.”

The researchers had to develop sophisticated new tools that accounted for the gas movement around Sgr A*. While M87* was an easier, steadier target, with nearly all images looking the same, that was not the case for Sgr A*. The image of the Sgr A* black hole is an average of the different images the team extracted, finally revealing the giant lurking at the center of our galaxy for the first time.

The effort was made possible through the ingenuity of more than 300 researchers from 80 institutes around the world that together make up the EHT Collaboration. In addition to developing complex tools to overcome the challenges of imaging Sgr A*, the team worked rigorously for five years, using supercomputers to combine and analyze their data, all while compiling an unprecedented library of simulated black holes to compare with the observations.

“This work clearly demonstrates the critical importance of using radio, millimeter and submillimeter frequencies to understand the most extreme environments in the Universe,” said Tony Remijan, Director of the North American ALMA Science Center (NAASC) at NRAO. “Using these frequency ranges is the only way to uncover the unique environment surrounding the black hole that are completely obscured at other frequencies. The addition of ALMA was also critical to the observations as it provided the necessary sensitivity to unambiguously make this observation. Combining all the data from facilities all over the world— with ALMA as the anchor for all these facilities— provided the sensitivity and resolution needed to make these types of discoveries. And this is only the beginning. ALMA is planning a large increase to its sensitivity in the next decade which will lead to even more profound discoveries awaiting us in the Universe.”

Scientists are particularly excited to finally have images of two black holes of very different sizes, which offers the opportunity to understand how they compare and contrast. They have also begun to use the new data to test theories and models of how gas behaves around supermassive black holes. This process is not yet fully understood but is thought to play a key role in shaping the formation and evolution of galaxies.

“Now we can study the differences between these two supermassive black holes to gain valuable new clues about how this important process works,” said EHT scientist Keiichi Asada from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “We have images for two black holes — one at the large end and one at the small end of supermassive black holes in the Universe — so we can go a lot further in testing how gravity behaves in these extreme environments than ever before.”

Progress on the EHT continues: a major observation campaign in March 2022 included more telescopes than ever before. The ongoing expansion of the EHT network and significant technological upgrades will allow scientists to share even more impressive images as well as movies of black holes in the near future.

In 2021, NSF and the ALMA Board approved a multi-million dollar upgrade for the Observatory’s Band 6 receivers through the North American ALMA Development Program. The upgrade will increase the quantity and quality of science measured in wavelengths between 1.4mm and 1.1mm, which will provide research projects like those at EHT with better sensitivity than ever before, and ultimately more accurate and more efficient science results. In addition, NRAO’s Next Generation Very Large Array (ngVLA) received positive support from the Astro2020 decadal survey. Currently, in early-stage planning and development, the ngVLA will achieve high priority goals in astronomy and astrophysics and is slated to become the ultimate black hole hunting machine.

“These new results from EHT are exciting both because they show us how far astronomy has come already, and also because they confirm that there’s still so much out there we haven’t seen and haven’t yet been able to observe and study,” said Dr. Tony Beasley, Director of NRAO.  “The antennas and instrumentation we design and develop at NRAO are making this progress possible, and we look forward to continuing to lead advances in radio astronomy that will uncover black holes and other phenomena lurking in the corners of the galaxy and the Universe.”

Notes

[1] The individual telescopes involved in the EHT in April 2017, when the observations were conducted, were: the Atacama Large Millimeter/submillimeter Array (ALMA), the Atacama Pathfinder Experiment (APEX), the IRAM 30-meter Telescope, the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope Alfonso Serrano (LMT), the Submillimeter Array (SMA), the UArizona Submillimeter Telescope (SMT), the South Pole Telescope (SPT). Since then, the EHT has added the Greenland Telescope (GLT), the NOrthern Extended Millimeter Array (NOEMA) and the UArizona 12-meter Telescope on Kitt Peak to its network.

ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) of Japan, together with the National Research Council (Canada), the Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan), and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, the Associated Universities, Inc./National Radio Astronomy Observatory (AUI/NRAO) and the National Astronomical Observatory of Japan (NAOJ). APEX, a collaboration between the Max Planck Institute for Radio Astronomy (Germany), the Onsala Space Observatory (Sweden) and ESO, is operated by ESO. The 30-meter Telescope is operated by IRAM (the IRAM Partner Organizations are MPG (Germany), CNRS (France) and IGN (Spain)). The JCMT is operated by the East Asian Observatory on behalf of the Center for Astronomical Mega-Science of the Chinese Academy of Sciences, NAOJ, ASIAA, KASI, the National Astronomical Research Institute of Thailand, and organizations in the United Kingdom and Canada. The LMT is operated by INAOE and UMass, the SMA is operated by Center for Astrophysics | Harvard & Smithsonian and ASIAA and the UArizona SMT is operated by the University of Arizona. The SPT is operated by the University of Chicago with specialized EHT instrumentation provided by the University of Arizona.

The Greenland Telescope (GLT) is operated by ASIAA and the Smithsonian Astrophysical Observatory (SAO). The GLT is part of the ALMA-Taiwan project, and is supported in part by the Academia Sinica (AS) and MOST. NOEMA is operated by IRAM and the UArizona 12-meter telescope at Kitt Peak is operated by the University of Arizona.

[2] Black holes are the only objects we know of where mass scales with size. A black hole a thousand times smaller than another is also a thousand times less massive.

About EHT Consortium

The EHT consortium consists of 13 stakeholder institutes; the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the Center for Astrophysics | Harvard & Smithsonian, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, and Radboud University.

About NRAO

The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA

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

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

Contacts

Geoffrey Bower
EHT Project Scientist
Institute of Astronomy and Astrophysics, Academic Sinica, Taipei
Tel: +1-808-961-2945
Email: gbower@asiaa.sinica.edu.tw

Huib Jan van Langevelde
EHT Project Director,
JIVE and University of Leiden, The Netherlands
Mobile: +31-62120 1419
Email: langevelde@jive.eu

Amy C. Oliver
Public Information & News Manager, NRAO
Public Information Officer, ALMA-North America
Tel: +1 434-296-0314
Email: aoliver@nrao.edu

Dave Finley
Public Information Officer, NRAO-VLA, VLBA
(505) 241-9210
dfinley@nrao.edu

The post Astronomers Reveal First Image of the Black Hole at the Heart of Our Galaxy appeared first on National Radio Astronomy Observatory.

The first image of the supermassive black hole at the center of our Milky Way galaxy brings radio astronomy back to its celestial birthplace. The Event Horizon Telescope (EHT), a worldwide collection of millimeter-wave radio telescopes, made the new, landmark image of the same region from which came the first cosmic radio waves ever detected. That detection, by Bell Telephone Laboratories engineer Karl Jansky in 1932, was the beginning of radio astronomy.

The new EHT image is the culmination of a long history of Milky Way research starting with Galileo Galilei, who used his telescope in 1610 to discover that our galaxy, which appears like clouds to the naked eye, actually is composed of stars. In 1785, British astronomer William Herschel produced a rudimentary map of the Milky Way.

In 1918, American astronomer Harlow Shapley located the Milky Way’s center by using the newly discovered distance-measuring tool provided by Cepheid variable stars to determine that a halo of globular star clusters that surrounds the Milky Way is centered on a region in the constellation Sagittarius. That region is obscured from visible-light telescopes by thick clouds of gas and dust.

Jansky was hired by Bell Laboratories in 1928 and given the task of determining the sources of noise that interfered with short-wave radio telephone communications. He designed a highly directional antenna and by 1932 had identified a number of noise sources. However, one mystery remained — “a very steady hiss type static the origin of which is not known.”

The time of day when this hiss appeared changed with the seasons. At the suggestion of an astronomer friend, Jansky consulted some astronomy textbooks and in December of 1932 concluded that the strange hiss is coming “from outside the solar system.” He announced this in a paper he presented at a Washington, D.C. meeting in April of 1933. His announcement was reported on the front page of the New York Times on May 5, 1933.

Ten days later, Jansky was interviewed on a nationwide radio network and said he had located the position in the sky of the noise he had found, and “that seems to confirm Dr. Shapley’s calculation that the radio waves seem to come from the center of gravity of our galaxy.”

That region later would be called Sagittarius A, as the brightest source of radio emission in that constellation. In 1951, Australian radio astronomers further narrowed down the emission’s origin as the galaxy’s center.

In 1974, Bruce Balick and Robert Brown used the National Radio Astronomy Observatory’s Green Bank Interferometer to discover a very bright and compact object to which Brown later attached the name Sagittarius A* (adding the asterisk). A black hole became the leading explanation for what powers the bright radio emission of the object, abbreviated Sgr A*. In 1994, infrared and submillimeter studies estimated the object’s mass at 3 million times that of the Sun.

In 2002, a team led by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics reported on a 10-year study of the orbital motion of a star called S2 near Sgr A*. That study concluded that the central object is more than 4 million times more massive than the Sun.

In 2009, another team reported on further observations of stellar orbits in the region and concluded that the central object probably is a black hole because no other phenomenon is known that can pack that much mass into such a small space. This work and other studies of Sgr A* earned the 2020 Nobel Prize in Physics for Genzel and Andrea Ghez of UCLA for producing “the most convincing evidence yet of a supermassive black hole at the center of the Milky Way.”

The EHT Collaboration’s production of an image consistent with the theoretical predictions of what should be seen around a black hole makes the case even more convincing today.

###

The post Milky Way’s Black Hole Was “Birth Cry” of Radio Astronomy appeared first on National Radio Astronomy Observatory.

The discovery helps explain the puzzle of hydrogen loss pre-supernova, and supports the theory that most massive stars are paired.

Post-starburst galaxiesGalaxyA large body of gas, dust, stars, and their companions (Planets, asteroids, moons, etc.) held together by their mutual gravitational attraction. They are grouped into three main categories: spiral galaxies, elliptical galaxies, and irregular galaxies. (see below) Another class of galaxies is peculiar galaxies, which are thought to be distorted versions of normal galaxies. were previously thought to scatter all of their gas and dust—the fuel required for creating new starsStarA giant ball of hot gas that creates and emits its own radiation through nuclear fusion.—in violent bursts of energy, and with extraordinary speed. Now, new data from the Atacama Large Millimeter/submillimeter Array (ALMA) reveals that these galaxies don’t scatter all of their star-forming fuel after all. Instead, after their supposed end, these dormant galaxies hold onto and compress large amounts of highly-concentrated, turbulent gas. But contrary to expectation, they’re not using it to form stars.

In most galaxies, scientists expect gas to be distributed in a way similar to starlight. But for post-starburst galaxies, or PSBs, this isn’t the case. PSBs are different from other galaxies because they are born in the aftermath of violent collisions, or mergers between galaxies. Galaxy mergers typically trigger massive bursts of star formation, but in PSBs, this outburst slows down and near-completely stops almost as soon as it begins. As a result, scientists previously believed that little or no star-forming fuel was left in these galaxies’ central star-forming factories. And until now, the belief was that the molecular gases had been redistributed to radii well beyond the galaxies, either through stellar processes or by the effects of black holes. The new results challenge this theory. 

“We’ve known for some time that large amounts of molecular gas remains in the vicinity of PSBs but haven’t been able to say where, which in turn, has prevented us from understanding why these galaxies stopped forming stars. Now, we have discovered a considerable amount of remaining gas within the galaxies and that remaining gas is very compact,” said Adam Smercina, an astronomer at the University of Washington and the principal investigator of the study. “While this compact gas should be forming stars efficiently, it isn’t. In fact, it is less than 10-percent as efficient as similarly compact gas is expected to be.”

In addition to being compact enough to make stars, the gas in the observed dormant—or quiescent—galaxies had another surprise in store for the team: it was often centrally-located, though not always, and was surprisingly turbulent. Combined, these two characteristics led to more questions than answers for researchers. 

“The rates of star formation in the PSBs we observed are much lower than in other galaxies, even though there appears to be plenty of fuel to sustain the process,” said Smercina. “In this case, star formation may be suppressed due to turbulence in the gas, much like a strong wind can suppress a fire. However, star formation can also be enhanced by turbulence, just like wind can fan flames, so understanding what is generating this turbulent energy, and how exactly it is contributing to dormancy, is a remaining question of this work.” 

Decker French, an astronomer at the University of Illinois, and a co-author of the research added, “These results raise the question of what energy sources are present in these galaxies to drive turbulence and prevent the gas from forming new stars. One possibility is energy from the accretion disk of the central supermassive black holes in these galaxies.”

A clear understanding of the processes that govern the formation of stars and galaxies is key to providing context to the Universe and our place in it. The discovery of turbulent, compact gas in otherwise dormant galaxies gives researchers one more clue to solving the mystery of how galaxies in particular live, evolve and die over the course of billions of years. And that means additional future research with the help of ALMA’s 1.3mm receiver, which sees the otherwise invisible with stark clarity. 

J.D. Smith, an astronomer at the University of Toledo, and a co-author of the research said, “There is much about the evolution of a typical galaxy we don’t understand, and the transition from their vibrant star-forming lives into quiescence is one of the least understood periods. Although post-starbursts were very common in the early Universe, today they are quite rare. This means the nearest examples are still hundreds of millions of light-years away, but these events foreshadow the potential outcome of a collision, or merger, between the Milky Way Galaxy and the Andromeda Galaxy several billion years from now. Only with the incredible resolving power of ALMA could we peer deep into the molecular reservoirs left behind ‘after the fall.’”

Smercina added, “It’s often the case that we as astronomers intuit the answers to our own questions ahead of observations, but this time, we learned something completely unexpected about the Universe.”

The results of the study are published today in The Astrophysical Journal.

Resource

“After The Fall: Resolving the Molecular Gas in Post-Starburst Galaxies,” Smercina et al (2022), The Astrophysical Journal, doi: 10.3847/1538-4357/ac5d5f

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About NRAO

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

About ALMA

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

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

Media Contact:

Amy C. Oliver
Public Information Officer, ALMA
Public Information & News Manager, NRAO
+1 434 242 9584
aoliver@nrao.edu

The post Scientists Find Elusive Gas From Post-starburst Galaxies Hiding in Plain Sight appeared first on National Radio Astronomy Observatory.

The isolated menagerie of five galaxies is caught in a gravitational dance.

Powerful radar systems have played a major role in the study of planets, moons, asteroids, and other objects in our Solar System for several decades, and now have a “unique role” to play in planetary defense – “providing protection to the nations of the world from devastating asteroid and comet impacts,” according to the newly released Planetary Science and Astrobiology Decadal Survey 2023-2032. The National Radio Astronomy Observatory (NRAO) and the Green Bank Observatory (GBO) are developing new capabilities for the Green Bank Telescope (GBT) and the Very Long Baseline Array (VLBA) that will make them key instruments for meeting this need.

The survey’s report, published by the National Academies of Sciences, Engineering, and Medicine, recounts the dangerous effects of impacts from Near Earth Objects (NEOs). These effects range from the asteroid impact 66 million years ago that wiped out the dinosaurs, to a Siberian impact in 1908 that had the explosive equivalent of 3 to 20 megatons of TNT, to a 2013 impact in Chelyabinsk, Russia, equal to 440 kilotons that injured more than 1,600 people. These are compared to the roughly 15-kiloton Hiroshima nuclear bomb.

The key to mitigating such dangers is to track the objects and measure their sizes and other characteristics to determine the probability that they will strike Earth and the effect they would have if they do. According to the survey, radar is an essential tool for this task.

“Ground-based radar observations of NEOs provide invaluable information for long-term tracking,” the survey said. “Because NEO impact energy scales with density, diameter, and velocity, and radar can constrain all of these, planetary radar observations are an important post-discovery characterization technique,” the survey added.

Prior to its collapse in 2020, the Arecibo telescope possessed the most powerful radar capabilities for the world’s astronomical community, often working with the GBT and VLBA as receivers. The Next Generation radar system being developed for the GBT and VLBA, and later the Next Generation Very Large Array (ngVLA), will help replace the capabilities lost at Arecibo.

The survey recommended developing “a plan for ground-based planetary radar capabilities comparable to or exceeding those of the Arecibo Observatory necessary for achieving planetary defense objectives.”

Since its dedication in 2000, the GBT has been a fundamental instrument for planetary science and planetary defense, observing NEOs and Potentially Hazardous Asteroids, the Moon, and the terrestrial planets as a receiver for radar projects. Now, thanks to new technology under development for the GBT, it is the largest fully steerable antenna in the world capable of transmitting radar signals for research. The GBT’s 100-meter diameter makes it an impressive tool for radar work. The location of the GBT and its maneuverability permits it to observe 85 percent of the celestial sphere, allowing it to quickly track objects across its field of view.

A recent article in the Microwave Journal reported on radar experiments done using the GBT and VLBA that successfully produced high resolution images of the Moon, and detected a Near-Earth Asteroid making a close flyby of Earth, more than 5 times farther away than the Moon – using less power than a microwave oven. In these tests, as a proof of concept, the GBT transmitted a 650-watt radar signal at 13.9 GHz that was received by VLBA antennas, producing radar images of the Moon’s surface with unprecedented detail.

The National Science Foundation has awarded funds for the conceptual design of a higher-power radar system on the GBT – one that would be nearly 1,000 times more powerful than the proof of concept. In addition to a more powerful transmitter, NRAO and GBO, working with industry partners, will leverage new, solid-state amplifier and array receiving-system technologies to maximize the effectiveness of the new system. In parallel to this, as additional funding is allocated, the team plans to move to final design and construction activities, beginning in 2023.

The GBT’s new radar capabilities will introduce a tool that astronomy has not had before, collecting data at higher resolutions and at wavelengths not previously available. NRAO and GBO also are developing advanced data reduction and analysis tools that have not been available before. The flexibility and increased performance of this new system will fill an important need for planetary defense, and also allow astronomers to observe asteroids, comets, planets and moons. The versatility of this system will contribute to many areas of science. 

Responding to the report, U.S. Senator Joe Manchin (D-WV) said, “For many years, I have been committed to ensuring the Green Bank Observatory stays open for the next generation of young scientists in West Virginia and around the world. Through my seat on the Senate Appropriations Committee, I have strongly supported Green Bank’s work observing and cataloging near-earth objects, including the development of new technology that would make it the world’s largest moveable antenna and transmitter. The new decadal survey underscores Green Bank’s importance in planetary research for many more decades to come, and I am proud of the scientists and the entire staff at Green Bank and look forward to seeing their continued efforts to advance our studies of the cosmos.”

U.S. Senator Shelly Moore Capito (R-WV) said, “One of the great benefits of the research and capabilities at Green Bank is the ability to meet the challenges scientists identify at the time. Here again Green Bank stands ready to advance scientific discovery to meet a national concern.”

“At NRAO and GBO, we have a long history of participation in planetary radar studies, and we look forward to adding new capabilities to the GBT and VLBA to produce a next-generation radar system that will serve as an essential tool for researchers in planetary science and planetary defense,” said Patrick Taylor, radar division head for NRAO and GBO.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Media Contacts:

NRAO: Dave Finley, Public Information Officer
dfinley@nrao.edu

GBO: Jill Malusky, Public Information Officer
jmalusky@nrao.edu

The post Future of Earth’s Defense is Ground-Based Planetary Radar appeared first on National Radio Astronomy Observatory.

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