“Little Cub” Gives Astronomers Rare Chance to See Galaxy’s Demise

Pictured above is a zoomed-in image of the Little Cub galaxy, a star-forming dwarf galaxy that is being stripped of gas by its gigantic neighboring galaxy. Credit: SDSS COLLABORATION

A false color image shows the grand design spiral galaxy NGC 3359, which is about 50 million light years from Earth. NGC 3359 appears to be devouring a much smaller gas rich dwarf galaxy, nicknamed the Little Cub, which contains 10,000 times fewer stars than its larger companion. The contours show where the gas is being stripped from the Little Cub, whose stars are located in the central blue circle. Credit: SDSS COLLABORATION

Lead author Tiffany Hsyu, a graduate student in the Department of Astronomy & Astrophysics at UC Santa Cruz. 
Credit: T. HSYU

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Maunakea, Hawaii – Astronomers have spotted a primitive galaxy being devoured by a gigantic neighboring galaxy – a discovery that could provide clues about the early universe.

The Little Cub galaxy – so called because it sits in the Ursa Major or Great Bear constellation – is being stripped of the gas needed to continue forming stars by its larger companion.

This rare opportunity to observe a dwarf galaxy as its gas is removed by the effects of a nearby giant galaxy will allow scientists to learn more about how this process happens.

Since the Little Cub has remained almost pristine since its formation, scientists also hope its elements will reveal more about the chemical signature of the universe just minutes after the Big Bang.

The research, carried out by the University of California, Santa Cruz and Durham University, United Kingdom, is being presented on Tuesday, July 4, at the Royal Astronomical Society’s National Astronomy Meeting.

The Little Cub was initially identified as a potentially pristine dwarf galaxy in data from the Sloan Digital Sky Survey (SDSS). Follow-up observations were conducted at the 10-meter Keck I telescope at the W. M. Keck Observatory on Maunakea, Hawaii, and the 3-meter Shane Telescope at Lick Observatory.

Researchers were able to confirm characteristics of the Little Cub galaxy using Keck Observatory’s Low Resolution Imaging Spectrograph, a faint-light instrument capable of taking spectra and images of the most distant known objects in the universe.

"The Little Cub's discovery is a terrific example of using the smaller 3-meter-class Lick Observatory to scan through hundreds of candidates before focusing on the best sources with the Keck telescope," said co-author J. Xavier Prochaska, Professor of Astronomy and Astrophysics at UC Santa Cruz.

The Little Cub’s larger neighbor, called NGC 3359, is a grand design spiral galaxy, which is a large galaxy that has over 100 billion stars with well-defined spiral arms – similar to our own Milky Way galaxy. The Little Cub and NGC 3359 are about 200 to 300 thousand light years apart, and approximately 50 million light years from Earth.

Gas from the Little Cub is being stripped away by its interaction with NGC 3359, which has up to 10,000 times as many stars as the Little Cub and is similar to our Milky Way.

By observing this cosmic feast, scientists hope to understand more about how and when gas is lost from smaller galaxies.

“We may be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way-like galaxy," said lead author Tiffany Hsyu, a graduate student in the Department of Astronomy & Astrophysics at UC Santa Cruz. “It is rare for such a tiny galaxy to still contain gas and be forming stars when it is in close proximity to a much larger galaxy, so this is a great opportunity to see just how this process works. Essentially the larger galaxy is removing the fuel that the Little Cub needs to form stars, which will eventually shut down star formation and lead to the smaller galaxy’s demise.”

The researchers also hope to gain insight into the make-up of the very early universe, by studying the hydrogen and helium atoms that are being illuminated by the small number of very bright stars within the Little Cub – which also has the less romantic name SDSS J1044+6306. Since this galaxy is so primitive, it may still preserve the hydrogen and helium atoms that were created minutes after the Big Bang.

“By studying the chemistry of the Little Cub, we know that it is one of the most primitive objects currently known in our cosmic neighborhood,” said research co-author Dr. Ryan Cooke, Royal Society University Research Fellow, in Durham University’s Centre for Extragalactic Astronomy.

“Such galaxies, which have remained dormant for most of their lives, are believed to contain the chemical elements forged a few minutes after the Big Bang.By measuring the relative number of hydrogen and helium atoms in the Little Cub we might be able to learn more about what made up the Universe in the moments after it began 13.7 billion years ago,” Cooke added.

The researchers hope further observations will find more pristine galaxies where the chemical signature of the early universe might be found.

A paper describing the discovery of Little Cub has been submitted for publication in the Astrophysical Journal Letters.

The research was funded by the W. M. Keck Foundation, Google, The Royal Society, NASA, the Science and Technology Facilities Council and the National Science Foundation (USA).

The Royal Astronomical Society’s National Astronomy Meeting is taking place at the University of Hull, UK, until Thursday, July 6, 2017.

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About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a versatile visible-wavelength imaging and spectroscopy instrument commissioned in 1993 and operating at the Cassegrain focus of Keck I. Since it has been commissioned it has seen two major upgrades to further enhance its capabilities: addition of a second, blue arm optimized for shorter wavelengths of light; and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument's high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion. Support for this project was generously provided by the Change Happens Foundation, Mt. Cuba Astronomical Foundation, William J. and Dorothy K. O’Neill Foundation, and Sanford and Jeanne Robertson.

About W. M. Keck Observatory

The W. M. Keck Observatory operates the most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. The Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California, and NASA.

Source:  W. M. Keck Observatory

Astronomers Baffled by Discovery of Rare Quasar

Image of the region of the space occupied by the rare quasar quartet. The four quasars are indicated by arrows. The quasars are embedded in a giant nebula of cool dense gas visible in the image as a blue haze. The nebula has an extent of one million light-years across, and these objects are so distant that their light has taken nearly 10 billion years to reach telescopes on Earth. This false color image is based on observations with the Keck 10m telescope on the summit of Maunakea in Hawaii.  Credit: Hennawi & Arrigoni-Battaia, MPIA

Maunakea, Hawaii – Using the W. M. Keck Observatory in Hawaii, a group of astronomers led by Joseph Hennawi of the Max Planck Institute for Astronomy have discovered the first quadruple quasar: four rare active black holes situated in close proximity to one another. The quartet resides in one of the most massive structures ever discovered in the distant universe, and is surrounded by a giant nebula of cool dense gas. Because the discovery comes with one-in-ten-million odds, perhaps cosmologists need to rethink their models of quasar evolution and the formation of the most massive cosmic structures. The results are being published in the May 15, 2015 edition of the journal Science.

Hitting the jackpot is one thing, but if you hit the jackpot four times in a row you might wonder if the odds were somehow stacked in your favor.

Quasars constitute a brief phase of galaxy evolution, powered by the in-fall of matter onto a supermassive black hole at the center of a galaxy. During this phase, they are the most luminous objects in the Universe, shining hundreds of times brighter than their host galaxies, which themselves contain hundreds of billions of stars. But these hyper-luminous episodes last only a tiny fraction of a galaxy’s lifetime, which is why astronomers need to be very lucky to catch any given galaxy in the act. As a result, quasars are exceedingly rare on the sky, and are typically separated by hundreds of millions of light years from one another. The researchers estimate that the odds of discovering a quadruple quasar by chance is one in ten million. How on Earth did they get so lucky? 

Clues come from peculiar properties of the quartet’s environment. The four quasars are surrounded by a giant nebula of cool dense hydrogen gas, which emits light because it is irradiated by the intense glare of the quasars. In addition, both the quartet and the surrounding nebula reside in a rare corner of the universe with a surprisingly large amount of matter. “There are several hundred times more galaxies in this region than you would expect to see at these distances,” said J. Xavier Prochaska, professor at the University of California Santa Cruz and the principal investigator of the Keck Observatory observations. 

Given the exceptionally large number of galaxies, this system resembles the massive agglomerations of galaxies, known as galaxy clusters, that astronomers observe in the present-day universe. But because the light from this cosmic metropolis has been travelling for 10 billion years before reaching Earth, the images show the region as it was 10 billion years ago, less than 4 billion years after the big bang. It is thus an example of a progenitor or ancestor of a present-day galaxy cluster, or proto-cluster for short. 

Piecing all of these anomalies together, the researchers tried to understand what appears to be their incredible stroke of luck. “If you discover something which, according to current scientific wisdom should be extremely improbable, you can come to one of two conclusions: either you just got very lucky, or you need to modify your theory,” Hennawi said. 

The researchers speculate that some physical process might make quasar activity much more likely in specific environments. One possibility is that quasar episodes are triggered when galaxies collide or merge, because these violent interactions efficiently funnel gas onto the central black hole. Such encounters are much more likely to occur in a dense proto-cluster filled with galaxies, just as one is more likely to encounter traffic when driving through a big city. 

“The giant emission nebula is an important piece of the puzzle since it signifies a tremendous amount of dense cool gas,” said Fabrizio Arrigoni-Battaia, a PhD student at the Max Planck Institute for Astronomy who was involved in the discovery.

Supermassive black holes can only shine as quasars if there is gas for them to swallow, and an environment that is gas rich could provide favorable conditions for fueling quasars.

On the other hand, given the current understanding of how massive structures in the universe form, the presence of the giant nebula in the proto-cluster is totally unexpected. “Our current models of cosmic structure formation based on supercomputer simulations predict that massive objects in the early universe should be filled with rarefied gas that is about ten million degrees, whereas this giant nebula requires gas thousands of times denser and colder,” said Sebastiano Cantalupo, currently at ETH Zurich, that led the imaging observations a the Keck Observatory during his previous research appointment at UCSC. “It is really amazing that this discovery was made the same night of the Slug Nebula while we were hunting for giant Lyman alpha nebulae illuminated by quasars – my first night at Keck Observatory and definitely the most exciting observing night I have ever had!” 

“Extremely rare events have the power to overturn long-standing theories” Hennawi said. 

As such, the discovery of the first quadruple quasar may force cosmologists to rethink their models of quasar evolution and the formation of the most massive structures in the universe. 

The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems. 

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile visible-wavelength imaging and spectroscopy instrument commissioned in 1993 and operating at the Cassegrain focus of Keck I. Since it has been commissioned it has seen two major upgrades to further enhance its capabilities: addition of a second, blue arm optimized for shorter wavelengths of light; and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument's high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe.

Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

SCIENCE CONTACT:

Joseph F.Hennawi
Max Planck Institute for Astronomy, Heidelberg, Germany
joe@mpia.de
+49 6221 528 -263

J. Xavier Prochaska
UCO Lick Observatory/University of California Santa Cruz
xavier@ucolick.org
+1 831 459 2135

Sebastiano Cantalupo
ETH Zurich, Switzerland
cantalupo@phys.ethz.ch
+41 44 633 7057


MEDIA CONTACT:

Markus Pössel
Public Information Officer
Max Planck Institute for Astronomy, Heidelberg, Germany
 pr@mpia.de
+49 6221 528 -261

Steve Jefferson
Communications Officer
W. M. Keck Observatory
sjefferson@keck.hawaii.edu
+1 808 881 3827

Source:  W.M. Keck Observatory

Scientists at Keck Discover the Fluffiest Galaxies

A collection of unidentified blobs was discovered toward the Coma cluster of galaxies, using the Dragonfly Telephoto Array. One of these puzzling objects, Dragonfly 44, was studied in detail using the Keck Observatory and confirmed as an ultra-diffuse galaxy. Even though it is 60,000 light years across, It is so far away that it appears as only a faint smudge.  Credit: P. van Dokkum, R. Abraham, J. Brodie. Hi-res image 

Reconstructed spectrum of light spread out from the ultra-diffuse galaxy, DragonFly44, as seen by the Keck/LRIS instrument. Dark bands occur where atoms and molecules absorb the galaxy’s starlight. These bands reveal the compositions and ages of the stars, and also the distance of the galaxy.  Credit: P. van Dokkum, A. Romanowsky, J. Brodie. Hi-res image

An ultra-diffuse galaxy, Dragonfly 17, is shown next to other types of galaxies, to scale. The Andromeda galaxy is a giant spiral like our own Milky Way, and a dwarf elliptical galaxy, NGC 205, is also shown. Ultra-diffuse galaxies have the same number of stars as dwarf ellipticals, but spread out over a much larger region.  Credit: B. Schoening, V. Harvey/REU program/NOAO/AURA/NSF, P. van Dokkum/Hubble Space Telescope. Hi-res image

Maunakea, Hawaii – An international team of researchers led by Pieter van Dokkum at Yale University have used the W. M. Keck Observatory to confirm the existence of the most diffuse class of galaxies known in the universe. These "fluffiest galaxies" are nearly as wide as our own Milky Way galaxy – about 60,000 light years – yet harbor only one percent as many stars. The findings were recently published in the Astrophysical Journal Letters.

“If the Milky Way is a sea of stars, then these newly discovered galaxies are like wisps of clouds”, said van Dokkum. “We are beginning to form some ideas about how they were born and it’s remarkable they have survived at all. They are found in a dense, violent region of space filled with dark matter and galaxies whizzing around, so we think they must be cloaked in their own invisible dark matter ‘shields’ that are protecting them from this intergalactic assault.”

The team made the latest discovery by combining results from one of the world's smallest telescopes as well as the largest telescope on Earth. The Dragonfly Telephoto Array used 14-centimeter state of the art telephoto lens cameras to produce digital images of the very faint, diffuse objects. Keck Observatory’s 10-meter Keck I telescope, with its Low Resolution Imaging Spectrograph, then separated the light of one of the objects into colors that diagnose its composition and distance.

Finding the distance was the clinching evidence. The data from Keck Observatory showed the diffuse "blobs" are very large and very far away, about 300 million light years, rather than small and close by. The blobs can now safely be called Ultra Diffuse Galaxies (UDGs).

“If there are any aliens living on a planet in an ultra-diffuse galaxy, they would have no band of light across the sky, like our own Milky Way, to tell them they were living in a galaxy. The night sky would be much emptier of stars,” said team member Aaron Romanowsky, of San Jose State University.

The UDGs were found in an area of the sky called the Coma cluster, where thousands of galaxies have been drawn together in a mutual gravitational dance. “Our fluffy objects add to the great diversity of galaxies that were previously known, from giant ellipticals that outshine the Milky Way, to ultra compact dwarfs,” said University of California, Santa Cruz Professor Jean Brodie.

“The big challenge now is to figure out where these mysterious objects came from,” said Roberto Abraham, of the University of Toronto. “Are they ‘failed galaxies’ that started off well and then ran out of gas? Were they once normal galaxies that got knocked around so much inside the Coma cluster that they puffed up? Or are they bits of galaxies that were pulled off and then got lost in space?”  The key next step in understanding UDGs is to to pin down exactly how much dark matter they have. Making this measurement will be even more challenging than the latest work.

The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems. 

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile visible-wavelength imaging and spectroscopy instrument commissioned in 1993 and operating at the Cassegrain focus of Keck I. Since it has been commissioned it has seen two major upgrades to further enhance its capabilities: addition of a second, blue arm optimized for shorter wavelengths of light; and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument's high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe.

Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

Source: W.M. Keck Observatory