From astrobites : “Stare into the Void”

Jun 11, 2022
Kayla Kornoelje

Title: Measurements of cosmic expansion and growth rate of structure from voids in the Sloan Digital Sky Survey between redshift 0.07 and 1.0
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Apache Point Observatory
SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft).

Apache Point Observatory near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft).
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Authors: Alex Woodfinden, Seshadri Nadathur, Will J. Percival, Slađana Radinović, Elena Massara, Hans A. Winther

First Author’s Institution: Waterloo Centre for Astrophysics, University of Waterloo

Status: Submitted to ArXiv [12 May 2022]

Pitch: BAOs are Cool

Cosmologists love Baryon Acoustic Oscillations (BAO), and here’s why you should too. Back when the universe was just a baby made out of hot plasma, a battle between gravity and radiation was raging on. Small overdensities in the hot plasma fought to collapse under gravity, while tightly coupled radiation provided pressure that resisted this collapse. The outcome of this battle were oscillations of matter that spread out across the plasma, almost like ripples in a pond. As the universe began to cool, radiation no longer provided support against gravitational collapse, and overdensities of matter contained within these ripples could finally collapse into galaxy clusters. These ripple-like patterns of galaxy clusters are known as BAOs, and they’re extremely important to cosmologists because their size and properties depend on the details of our universe’s composition. Precise measurements of these BAOs can provide constraints on important cosmological parameters such as the amount of baryonic matter, dark matter, and dark energy in the universe. Additionally, monitoring the size of BAOs over a wide range of redshifts can be used to measure how the expansion rate of the universe changes across cosmic time. Given everything that we can learn from studying BAOs, it’s no wonder why cosmologists have been using them as cosmological probes for decades. Have I sold you on BAOs yet?

Pitch 2: So are Cosmic Voids

If so, I have another cosmological probe to sell you on: cosmic voids. If BAOs represent overdense regions in the universe, it’s no surprise that there are regions with extremely low densities as well. These cosmic voids are around a tenth of the average density of the universe, and they’re massive, making up around 90% of our universe. And, as it turns out, these voids are just as exciting to test parameters of cosmology as BAOs are! The properties of voids are sensitive to everything from Dark Energy and “modified gravity” [MOND], to structure growth and galaxy formation. Who knew you could get something from studying nothing!

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The Dark Energy Survey

Dark Energy Camera [DECam] built at DOE’s Fermi National Accelerator Laboratory.

NOIRLab National Optical Astronomy Observatory Cerro Tololo Inter-American Observatory(CL) Victor M Blanco 4m Telescope which houses the Dark-Energy-Camera – DECam at Cerro Tololo, Chile at an altitude of 7200 feet.

NOIRLab NSF NOIRLab NOAO Cerro Tololo Inter-American Observatory(CL) approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.

Timeline of the Inflationary Universe WMAP.

The The Dark Energy Survey is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. The Dark Energy Survey began searching the Southern skies on August 31, 2013.

According to Albert Einstein’s Theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up.
Saul Perlmutter (center) [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt (right) and Adam Riess (left) [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called Dark Energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

The Dark Energy Survey is designed to probe the origin of the accelerating universe and help uncover the nature of Dark Energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

Over six years (2013-2019), the Dark Energy Survey collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.
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MOND [Modified Newtonian dynamics]

MOND Rotation Curves with MOND Tully-Fisher

Mordehai Milgrom, MOND theorist, is an Israeli physicist and professor in the department of Condensed Matter Physics at the Weizmann Institute in Rehovot, Israel http://cosmos.nautil.us

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Figure 1: Measurements of the growth rate of structure (ƒσ₈) compared to the values measured by the cosmic microwave background (blue strip). The red marks represent the measurements from the void-galaxy correlation, the gray marks represent measurements from BAOs, and the green marks represent void-galaxy correlation measurements using different analysis techniques. (Figure 6 in the paper)

But most important for today’s discussion is the information encoded within the void-galaxy cross-correlation function. While it sounds like a mouthful, this function really just describes the properties, such as the density and peculiar velocities, of galaxies surrounding voids. This statistical property is particularly important as it can characterize both red-shift-space distortions (RSDs), and the Alcock-Paczyński (AP) effect. Astronomers use an object’s velocity to determine its redshift, and RSDs are simply biases in our redshift measurement due to an additional peculiar velocity component. Since peculiar velocities are dependent on local gravitational interactions, accurately characterizing RSDs can tell us a lot about the properties of matter in our universe, such as the growth rate of structure. The AP effect, on the other hand, is a distortion of the shape of a distribution of galaxy clusters. If we assume galaxy clusters are distributed like a sphere around voids, the AP effect can make the distribution of clusters appear flattened or elongated if astronomers make incorrect assumptions about the geometry of the universe. Analysis of these distortions provides astronomers with measurements of what is known as the Alcock-Paczyński distance ratio, which is the ratio between the comoving angular diameter distance and the Hubble distance. This is particularly exciting for the study of cosmic voids, as they should be able to constraint this distance ratio even more precisely than BAOs can. All in all, cosmic voids are a novel probe of the properties of our universe. Not sold yet? Well, let’s let the results of today’s paper do the talking then!

The Proof is in the Cosmic Void

The authors of today’s paper examined the cross-correlation of galaxies and cosmic voids to unravel the wealth of cosmological information packed within them. After careful and rigorous treatment of both selection and systematic errors that can arise from the analysis of cosmic voids, the authors found exciting results. First, the authors found that cosmic voids alone can constrain the value of the growth rate of structure just as precisely as BAOs can (Figure 1). While this is not a novel result, this precision points to the fact that voids are a great tool to use in combination with BAOs to get better measurements of cosmological parameters than either of them can do alone. But, perhaps even more compelling is the fact that the author’s results also confirm that cosmic voids do beat BAOs when it comes to measuring the AP distance ratio (Figure 2). Such results demonstrate the importance of voids as cosmological probes, and support a powerful new avenue for cosmologists to explore to unlock the mysteries of our universe. And, as the cherry on top of it all, there are new galaxy surveys such as DESI and Euclid coming up in the near future, which will probe much larger volumes of the universe over a larger redshift range. Watch out world, precision cosmology is about to get even more precise!

DOE’s Lawrence Berkeley National Laboratory(US) DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory, in the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft).

National Optical Astronomy Observatory Mayall 4 m telescope at NSF NOIRLab NOAO Kitt Peak National Observatory in the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft).

National Science Foundation NOIRLab NOAO Kitt Peak National Observatory on the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers (55 mi) west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft).

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/Euclid spacecraft depiction.

Figure 2: Measurements of the AP distance ratio Dₘ/DH. Red points represent measurements from void-galaxy correlations, and gray points represent those from BAOs. The green and blue bands are expected values from the CMB (blue) and the CMB combined with other cosmological probes (green). (Figure 7 in the paper)

See the full article here .

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What do we do?

Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
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Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.

Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

From Ethan Siegel: “These Are The Most Distant Astronomical Objects In The Known Universe”

From Ethan Siegel
Dec 30, 2019

Astronomy’s enduring quest is to go farther, fainter, and more detailed than ever before. Here’s the edge of the cosmic frontier.

The distant galaxy MACS1149-JD1 is gravitationally lensed by a foreground cluster, allowing it to be imaged at high resolution and in multiple instruments, even without next-generation technology.

This galaxy’s light comes to us from 530 million years after the Big Bang, but the stars within it are at least 280 million years old. It is the second-most distant galaxy with a spectroscopically confirmed distance, placing it 30.7 billion light-years away from us. (ALMA (ESO/NAOJ/NRAO), NASA/ESA HUBBLE SPACE TELESCOPE, W. ZHENG (JHU), M. POSTMAN (STSCI), THE CLASH TEAM, HASHIMOTO ET AL.)

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

Astronomers have always sought to push back the viewable distance frontiers.

Although there are magnified, ultra-distant, very red and even infrared galaxies in the eXtreme Deep Field, there are galaxies that are even more distant out there than what we’ve discovered in our deepest-to-date views. These galaxies will always remain visible to us, but we will never see them as they are today: 13.8 billion years after the Big Bang. (NASA, ESA, R. BOUWENS AND G. ILLINGWORTH (UC, SANTA CRUZ))

More distant galaxies appear fainter, smaller, bluer, and less evolved overall.

Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky Way-like are inherently smaller, bluer, more chaotic, and richer in gas in general than the galaxies we see today. For the first galaxies of all, this ought to be taken to the extreme, and remains valid as far back as we’ve ever seen. The exceptions, when we encounter them, are both puzzling and rare. (NASA AND ESA)

Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

Individual planets and stars are only known relatively nearby, as our tools cannot take us farther.

Local Group. Andrew Z. Colvin 3 March 2011

A massive cluster (left) magnified a distant star known as Icarus more than 2,000 times, making it visible from Earth (lower right) even though it is 9 billion light years away, far too distant to be seen individually with current telescopes. It was not visible in 2011 (upper right). The brightening leads us to believe that this was a blue supergiant star, formally named MACS J1149 Lensed Star 1. (NASA, ESA, AND P. KELLY (UNIVERSITY OF MINNESOTA))

As the 2010s end, here are our presently known most distant astronomical objects.

The ultra-distant supernova SN UDS10Wil, shown here, is the farthest type Ia supernova ever discovered, whose light arrives today from a position 17 billion light-years away.

A white dwarf fed by a normal star reaches the critical mass and explodes as a type Ia supernova. Credit: NASA/CXC/M Weiss

Type Ia supernovae are used as distance indicators because of their standard intrinsic brightnesses, and are some of our strongest evidence for the accelerated expansion best explained by dark energy.

Standard Candles to measure age and distance of the universe from supernovae NASA

(NASA, ESA, A. RIESS (STSCI AND JHU), AND D. JONES AND S. RODNEY (JHU))

The farthest type Ia supernova, our most distant “standard candle” for probing the Universe, is SN UDS10Wil, located 17 billion light-years (Gly) away.

This illustration of superluminous supernova SN 1000+0216, the most distant supernova ever observed at a redshift of z=3.90, from when the Universe was just 1.6 billion years old, is the current record-holder for individual supernovae. Unlike SN UDS10Wil, this supernova is a Type II (core collapse) supernova, and may have formed via the pair instability mechanism, which would explain its extraordinarily large intrinsic brightness. (ADRIAN MALEC AND MARIE MARTIG (SWINBURNE UNIVERSITY))

The most distant supernova of all, 2012’s superluminous SN 1000+0216, occurred 23 Gly away.

The most distant X-ray jet in the Universe, from quasar GB 1428, sends us light from when the Universe was a mere 1.25 billion years old: less than 10% its current age. This jet comes from electrons heating CMB photons, and is over 230,000 light-years in extent: approximately double the size of the Milky Way. (X-RAY: NASA/CXC/NRC/C.CHEUNG ET AL; OPTICAL: NASA/STSCI; RADIO: NSF/NRAO/VLA)

NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

The most distant quasar jet, revealed by GB 1428+4217’s X-rays, is 25.4 Gly distant.

This image of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, was created from images taken from surveys made by both the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey.

SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude2,788 meters (9,147 ft)

UKIRT, located on Mauna Kea, Hawai’i, USA as part of Mauna Kea Observatory,4,207 m (13,802 ft) above sea level

The quasar appears as a faint red dot close to the centre. This quasar was the most distant one known from 2011 until 2017, and is seen as it was just 745 million years after the Big Bang. It is the most distant quasar with a visual image available to be viewed by the public. (ESO/UKIDSS/SDSS)

The first discovered object whose light exceeds 13 billion years in age, quasar ULAS J1120+0641, is 28.8 Gly away.

This artist’s concept shows the most distant quasar and the most distant supermassive black hole powering it. At a redshift of 7.54, ULAS J1342+0928 corresponds to a distance of some 29.32 billion light-years; it is the most distant quasar/supermassive black hole ever discovered. Its light arrives at our eyes today, in the radio part of the spectrum, because it was emitted just 686 million years after the Big Bang. (ROBIN DIENEL/CARNEGIE INSTITUTION FOR SCIENCE)

However, quasar ULAS J1342+0928 is even farther at 29.32 Gly: our most distant black hole.

This illustration of the most distant gamma-ray burst ever detected, GRB 090423, is thought to be typical of most fast gamma-ray bursts. When one or two objects violently form a black hole, such as from a neutron star merger, a brief burst of gamma rays followed by an infrared afterglow (when we’re lucky) allows us to learn more about these events. The gamma rays from this event lasted just 10 seconds, but Nial Tanvir and his team found an infrared afterglow using the UKIRT telescope just 20 minutes after the burst, allowing them to determine a redshift (z=8.2) and distance (29.96 billion light-years) to great precision. (ESO/A. ROQUETTE)

Gamma-ray bursts exceed even that; GRB 090423’s verified light comes from 29.96 Gly away in the distant Universe, while GRB 090429B might’ve been even farther.

Here, candidate galaxy UDFj-39546284 appears very faint and red, and from the colors it displays, it has an inferred redshift of 10, giving it an age below 500 million years and a distance greater than 31 billion light-years. Without spectroscopic confirmation, however, this and similar galaxies cannot reliably be said to have a known distance; more data is needed, as photometric redshifts are notoriously unreliable. (NASA, ESA, G. ILLINGWORTH (UNIVERSITY OF CALIFORNIA, SANTA CRUZ), R. BOUWENS (UNIVERSITY OF CALIFORNIA, SANTA CRUZ, AND LEIDEN UNIVERSITY) AND THE HUDF09 TEAM)

Ultra-distant galaxy candidates abound, including SPT0615-JD, MACS0647-JD, and UDFj-39546284, all lacking spectroscopic confirmation.

The most distant galaxy ever discovered in the known Universe, GN-z11, has its light come to us from 13.4 billion years ago: when the Universe was only 3% its current age: 407 million years old. The distance from this galaxy to us, taking the expanding Universe into account, is an incredible 32.1 billion light-years. (NASA, ESA, AND G. BACON (STSCI))

The most distant galaxy of all is GN-z11, located 32.1 Gly away.

The James Webb Space Telescope vs. Hubble in size (main) and vs. an array of other telescopes (inset) in terms of wavelength and sensitivity. It should be able to see the truly first galaxies, even the ones that no other observatory can see. Its power is truly unprecedented. (NASA / JWST SCIENCE TEAM)

With the 2020s promising revolutionary new observatories, these records may all soon fall.

Our deepest galaxy surveys can reveal objects tens of billions of light years away, but there are more galaxies within the observable Universe we still have yet to reveal between the most distant galaxies and the cosmic microwave background [CMB], including the very first stars and galaxies of all.

It is possible that the coming generation of telescopes will break all of our current distance records. (SLOAN DIGITAL SKY SURVEY (SDSS))

See the full article here .

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“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

From University of Portsmouth: “Holes in the Universe sharpen cosmic measurements”

From University of Portsmouth

July 10, 2019

The change in the average shape of voids caused by Doppler distortions and the effects of dark energy and curvature.

Regions of the Universe containing very few or no galaxies – known as voids – can help measure cosmic expansion with much greater precision than before, according to new research.

The study looked at the shapes of voids found in data from the Sloan Digital Sky Survey (SDSS) collaboration.

Voids come in a variety shapes, but because they have no preferred direction of alignment, a large enough sample of them can on average be used as “standard spheres” – objects which should appear perfectly symmetric in the absence of any distortions.

However, the observed shapes of these spheres are distorted by Doppler shifts in the redshifts of nearby galaxies caused by the local velocity field, and by the nature and amounts of dark matter and dark energy that make up 95% of the Universe. This distortion can be theoretically modelled, and the new work shows it can now be precisely measured.

The research was led by the University of Portsmouth, a world leader in cosmology, and is published this week in Physical Review D.

The new measurement of the distortion around voids used the Baryon Oscillation Spectroscopic Survey (BOSS) of galaxies from SDSS, that was designed to measure dark energy and the curvature of space.

BOSS Supercluster Baryon Oscillation Spectroscopic Survey (BOSS)

For measuring a key aspect of the cosmic expansion, the new method greatly outperforms the standard baryon acoustic oscillation (BAO) technique that BOSS was designed for. The new results agree with the simplest model of a flat Universe with a cosmological constant dark energy, and tighten the constraints on alternative theories.

Lead author, Dr Seshadri Nadathur, research fellow at the University’s Institute of Cosmology and Gravitation (ICG), said: “This measurement tremendously upgrades the previous best results from BOSS – the precision is equivalent to getting data from a hypothetical survey four times as large as BOSS, completely for free. It really helps pin down the properties of dark energy.”

“These results also mean that the expected science results from facilities such as the European Space Agency’s Euclid satellite mission and the Dark Energy Spectroscopic Instrument – in which the astronomy community have invested a lot of resources – can be even better than previously thought.”

LBNL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018

NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)

The other authors include Portsmouth’s PhD student Paul Carter, research fellows Dr Hans Winther and Dr Julian Bautista, and former Portsmouth Professor Will Percival, who has recently taken up a new role in Canada.

See the full article here .

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Please help promote STEM in your local schools.

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The University of Portsmouth is a public university in the city of Portsmouth, Hampshire, England. The history of the university dates back to 1908, when the Park building opened as a Municipal college and public library. It was previously known as Portsmouth Polytechnic until 1992, when it was granted university status through the Further and Higher Education Act 1992. It is ranked among the Top 100 universities under 50 in the world.

The university offers a range of disciplines, from Pharmacy, International relations and politics, to Mechanical Engineering, Paleontology, Criminology, Criminal Justice, among others. The Guardian University Guide 2018 ranked its Sports Science number one in England, while Criminology, English, Social Work, Graphic Design and Fashion and Textiles courses are all in the top 10 across all universities in the UK. Furthermore, 89% of its research conducted in Physics, and 90% of its research in Allied Health Professions (e.g. Dentistry, Nursing and Pharmacy) have been rated as world-leading or internationally excellent in the most recent Research Excellence Framework (REF2014).

The University is a member of the University Alliance and The Channel Islands Universities Consortium. Alumni include Tim Peake, Grayson Perry, Simon Armitage and Ben Fogle.

Portsmouth was named the UK’s most affordable city for students in the Natwest Student Living Index 2016. On Friday 4 May 2018, the University of Portsmouth was revealed as the main shirt sponsor of Portsmouth F.C. for the 2018–19, 2019–20 and 2020–21 seasons.

From JPL-Caltech: “In Colliding Galaxies, a Pipsqueak Shines Bright”

From JPL-Caltech

February 20, 2019

Calla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
626-808-2469
calla.e.cofield@jpl.nasa.gov

Bright green sources of high-energy X-ray light captured by NASA’s NuSTAR mission are overlaid on an optical-light image of the Whirlpool galaxy a.k.a. Messier 51a, M51a, and NGC 5194 (in the center of the image) and its companion galaxy, Messier 51b (the bright greenish-white spot above the Whirlpool), taken by the Sloan Digital Sky Survey.Credit: NASA/JPL-Caltech, IPAC

SDSS 2.5 meter Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

In the nearby Whirlpool galaxy and its companion galaxy, Messier 51b, two supermassive black holes heat up and devour surrounding material. These two monsters should be the most luminous X-ray sources in sight, but a new study using observations from NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) mission shows that a much smaller object is competing with the two behemoths.

The most stunning features of the Whirlpool galaxy – officially known as Messier 51a – are the two long, star-filled “arms” curling around the galactic center like ribbons. The much smaller Messier 51b clings like a barnacle to the edge of the Whirlpool. Collectively known as Messier 51, the two galaxies are merging.

At the center of each galaxy is a supermassive black hole millions of times more massive than the Sun. The galactic merger should push huge amounts of gas and dust into those black holes and into orbit around them. In turn, the intense gravity of the black holes should cause that orbiting material to heat up and radiate, forming bright disks around each that can outshine all the stars in their galaxies.

But neither black hole is radiating as brightly in the X-ray range as scientists would expect during a merger. Based on earlier observations from satellites that detect low-energy X-rays, such as NASA’s Chandra X-ray Observatory, scientists believed that layers of gas and dust around the black hole in the larger galaxy were blocking extra emission. But the new study, published in The Astrophysical Journal, used NuSTAR’s high-energy X-ray vision to peer below those layers and found that the black hole is still dimmer than expected.

“I’m still surprised by this finding,” said study lead author Murray Brightman, a researcher at Caltech in Pasadena, California. “Galactic mergers are supposed to generate black hole growth, and the evidence of that would be strong emission of high-energy X-rays. But we’re not seeing that here.”

Brightman thinks the most likely explanation is that black holes “flicker” during galactic mergers rather than radiate with a more or less constant brightness throughout the process.

“The flickering hypothesis is a new idea in the field,” said Daniel Stern, a research scientist at NASA’s Jet Propulsion Laboratory in Pasadena and the project scientist for NuSTAR. “We used to think that the black hole variability occurred on timescales of millions of years, but now we’re thinking those timescales could be much shorter. Figuring out how short is an area of active study.”

Small but Brilliant

Along with the two black holes radiating less than scientists anticipated in Messier 51a and Messier 51b, the former also hosts an object that is millions of times smaller than either black hole yet is shining with equal intensity. The two phenomena are not connected, but they do create a surprising X-ray landscape in Messier 51.

The small X-ray source is a neutron star, an incredibly dense nugget of material left over after a massive star explodes at the end of its life. A typical neutron star is hundreds of thousands of times smaller in diameter than the Sun – only as wide as a large city – yet has one to two times the mass. A teaspoon of neutron star material would weigh more than 1 billion tons.

Despite their size, neutron stars often make themselves known through intense light emissions. The neutron star found in M51 is even brighter than average and belongs to a newly discovered class known as ultraluminous neutron stars. Brightman said some scientists have proposed that strong magnetic fields generated by the neutron star could be responsible for the luminous emission; a previous paper by Brightman and colleagues about this neutron star supports that hypothesis. Some of the other bright, high-energy X-ray sources seen in these two galaxies could also be neutron stars.

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia (now part of Northrop Grumman). NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive.

See the full article here .

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Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge, on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

From Science Blog from the SDSS: “SDSS Fifteenth Data Release”

From Science Blog from the SDSS

On Monday 10 December the Sloan Digital Sky Survey (SDSS) celebrated its fifteenth public data release, DR15. This data release the spotlight was on the MaNGA survey (Mapping Nearby Galaxies at Apache Point Observatory).

DR15 contains 4621 of the 10,000 galaxies that MaNGA will have observed by summer 2020. To keep up to date with all MaNGA news, you can follow this survey on twitter: @MaNGASurvey. Image credit: Dana Berry / SkyWorks Digital Inc., David Law, and the SDSS collaboration.

MaNGA observes nearby galaxies using a technique called Integral-Field Spectroscopy. This technique allows them to take many spectra all across the galaxy, and these spectra are then used to map the stars and gas in the galaxy. MaNGA can then find out how the stars and gas move around in the galaxy, and what kind of stellar populations (young? old? metal-rich? metal-poor?) are present in the galaxy. These maps help the MaNGA team understand how galaxies form and evolve over cosmic time. DR15 includes all these maps, that were produced by a special Data Analysis Pipeline, and with Marvin you can now explore these maps yourself!

Caption: snapshot of Marvin: the new tool to explore MaNGA galaxies. You can find Marvin at https://dr15.sdss.org/marvin/, and you can also follow Marvin on twitter: @Marvin_SDSS. Image taken from Aguado et al. 2018.

But it was not just galaxies that featured in DR15: MaNGA is running a sub-program called MaStar: the MaNGA Stellar Library.

Example spectra from the MaStar library.

This survey observes almost in stealth mode: they use the optical BOSS spectrographs that MaNGA also uses, but only when there is a full moon and the sky is too bright to observe faint galaxies. Bright time is when APOGEE-2 is in charge, using the Sloan telescope to observe Milky Way stars in the infrared.

But the MaStar and APOGEE-2 teams work together, so that both teams can observe their stars at the same time using two different spectrographs (optical and infrared). The MaStar team is interested in learning more about the properties and physics of their stars, but also want to use their stellar spectra as templates for analyzing MaNGA galaxies.

All this new data is now freely available, and we have a brand-new portal to show you all the different ways that you can access and interact with SDSS data: https://dr15.sdss.org/. A very big thank you to all the people in SDSS who made DR15 possible, and a special shout-out to all SDSS team members last spring participated in DocuVana, to write all the documentation that goes with this data release!

What is next? MaNGA’s sibling surveys, APOGEE-2 (APO Galaxy Evolution Experiment 2) and eBOSS (Extended Baryon Oscillation Spectroscopic Survey) took a break during DR15, because they are preparing for a smashing DR16. Next year APOGEE-2 will release lots of new infra-red spectra of stars in the Milky Way, including the very first spectra taken from the Southern hemisphere at Las Campanas Observatory. And eBOSS is currently hard at work putting together new catalogs of the large scale structure of the Universe, that they will release alongside lots of new optical spectra of galaxies and quasars. So stay tuned for DR16!

The “first light” observations for the APOGEE South spectrograph. The dots show stars whose spectra were observed by APOGEE. Some example spectra are shown (colors are representative only, as APOGEE spectra are in the infrared).

The first light observations included spectra of supermassive stars in the Tarantula Nebula. This nebula in the Large Magellanic Cloud is forming stars more rapidly than any other region in our Local Group of galaxies. It can only be seen from the Southern Hemisphere, underscoring the importance of APOGEE South’s location. The spectrograph will allow us to study the chemistry and evolution of the stars in the nebula in greater detail than ever before.

A slice through largest-ever three-dimensional map of the Universe. Earth is at the left, and distances to galaxies and quasars are labelled by the lookback time to the objects (lookback time means how long the light from an object has been traveling to reach us here on Earth). The locations of quasars (galaxies with supermassive black holes) are shown by the red dots, and nearer galaxies mapped by SDSS are also shown (yellow).

The right-hand edge of the map is the limit of the observable Universe, from which we see the Cosmic Microwave Background (CMB) – the light “left over” from the Big Bang. The bulk of the empty space in between the quasars and the edge of the observable universe are from the “dark ages”, prior to the formation of most stars, galaxies, or quasars. Click on the image for a larger version.

Image Credit: Anand Raichoor (École polytechnique fédérale de Lausanne, Switzerland) and the SDSS collaboration

See the full article here .

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Please help promote STEM in your local schools.

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After nearly a decade of design and construction, the Sloan Digital Sky Survey saw first light on its giant mosaic camera in 1998 and entered routine operations in 2000. While the collaboration and scope of the SDSS have changed over the years, many of its key principles have stayed fixed: the use of highly efficient instruments and software to enable astronomical surveys of unprecedented scientific reach, a commitment to creating high quality public data sets, and investigations that draw on the full range of expertise in a large international collaboration. The generous support of the Alfred P. Sloan Foundation has been crucial in all phases of the SDSS, alongside support from the Participating Institutions and national funding agencies in the U.S. and other countries.

The Sloan Digital Sky Survey has created the most detailed three-dimensional maps of the Universe ever made, with deep multi-color images of one third of the sky, and spectra for more than three million astronomical objects.

In its first five years of operations, the SDSS carried out deep multi-color imaging over 8000 square degrees and measured spectra of more than 700,000 celestial objects. With an ever-growing collaboration, SDSS-II (2005-2008) completed the original survey goals of imaging half the northern sky and mapping the 3-dimensional clustering of one million galaxies and 100,000 quasars. SDSS-II carried out two additional surveys: the Supernova Survey, which discovered and monitored hundreds of supernovae to measure the expansion history of the universe, and the Sloan Extension for Galactic Understanding and Exploration (SEGUE), which extended SDSS imaging towards the plane of the Galaxy and mapped the motions and composition of more than a quarter million Milky Way stars.

SDSS-III (2008-2014) undertook a major upgrade of the venerable SDSS spectrographs and added two powerful new instruments to execute an interweaved set of four surveys, mapping the clustering of galaxies and intergalactic gas in the distant universe (BOSS), the dynamics and chemical evolution of the Milky Way (SEGUE-2 and APOGEE), and the population of extra-solar giant planets (MARVELS).

The latest generation of the SDSS (SDSS-IV, 2014-2020) is extending precision cosmological measurements to a critical early phase of cosmic history (eBOSS), expanding its revolutionary infrared spectroscopic survey of the Galaxy in the northern and southern hemispheres (APOGEE-2), and for the first time using the Sloan spectrographs to make spatially resolved maps of individual galaxies (MaNGA).

This is the “Science blog” of the SDSS. Here you’ll find short descriptions of interesting scientific research and discoveries from the SDSS. We’ll also update on activities of the collaboration in public engagement and other arenas. We’d love to see your comments and questions about what you read here!

You can explore more on the SDSS Website.

From Fermi National Accelerator Lab via HostingAdvice.com: “The World-Class Computing Resources Behind the DOE’s Fermilab”

FNAL Art Image by Angela Gonzales

From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

via

HostingAdvice.com

December 14, 2018
Christine Preusler

Fermilab, a DOE-sponsored particle physics and accelerator laboratory, is raising the bar on innovative and cost-effective computing solutions that help researchers explore high-energy physics. As a repository for massive sets of scientific data, the national laboratory is at the forefront of new computing approaches, including HEPCloud, a paradigm for provisioning computing resources.

It’s common knowledge that Tim Berners-Lee invented the World Wide Web in 1989. But if you’re not a quantum physicist, you may be surprised to learn that he accomplished the feat while working at the European Organization for Nuclear Research (CERN), a prominent scientific organization that operates the largest particle physics lab on the globe.

“It was the field of high-energy physics for which the web was started to provide a way for physicists to exchange documents,” said Marc Paterno, Assistant Head for R&D and Architecture at Fermilab, a premier national laboratory for particle physics and accelerator research that serves as the American counterpart to CERN.

Marc told us the particle physics field as a whole has been testing the limits of large-scale data analyzation since it first gained access to high-throughput computational resources. Furthermore, the high-energy physics community is responsible for developing some of the first software and computing tools suitable to meet the demands of the field.

“Of course, Google has now surpassed us in that its data is bigger than any particular set of experimental data; but even a small experiment at Fermilab produces tens of terabytes of data, and the big ones we are involved with produce hundreds of thousands of petabytes of data over the course of the experiment,” Marc said. “Then there are a few thousand physicists wanting to do analysis on that data.”

The lab is named after Nobel Prize winner Enrico Fermi, who made significant contributions to quantum theory and created the world’s first nuclear reactor. Located near Chicago, Fermilab is one of 17 U.S. Department of Energy Office of Science laboratories across the country. Though many DOE-funded labs serve multiple purposes, Marc said Fermilab works toward a single mission: “To bring the world together to solve the mysteries of matter, energy, space, and time.”

And that mission, he said, is made possible through high-powered computing. “For scientists to understand the huge amounts of raw information coming from particle physics experiments, they must process, analyze, and compare the information to simulations,” Marc said. “To accomplish these feats, Fermilab hosts high-performance computing, high-throughput (grid) computing, and storage and networking systems.”

In addition to leveraging high-performance computing systems to analyze complex datasets, Fermilab is a repository for massive sets of priceless scientific data. With plans to change the way computing resources are used to produce experimental results through HEPCloud, Fermilab is continuing to deploy innovative computing solutions to support its overarching scientific mission.

Pushing the Envelope on High-Throughput Computing

While Fermilab wasn’t built to develop computational resources, Marc told us “nothing moves forward in particle physics without computing.” That wasn’t always the case: When the lab was first founded, bubble chambers were used to detect electrically charged particles.

“They were analyzed by looking at pictures of the bubble chamber, taking a ruler, and measuring curvatures of trails to figure out what the particles were doing inside of a detector,” he said. “Now, detectors are enormous, complicated contraptions that cost tens of millions to billions of dollars to make.”

Experiments at Fermilab typically involve massive datasets.

Marc said Fermilab is in possession of a large amount of computing resources and is heavily involved with CERN’s Compact Muon Solenoid (CMS), a general-purpose detector at the world’s largest and most powerful particle accelerator, the Large Hadron Collider (LHC).

LHC

The CMS has an extensive physics agenda ranging from researching the Standard Model of particle physics to searching for extra dimensions and particles that possibly make up dark matter.

The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

Standard Model of Particle Physics from Symmetry Magazine

“Fermilab provides one of the largest pools of resources for the CMS experiment and their worldwide collection,” Marc said.

Almost every experiment at Fermilab includes significant international involvement from universities and laboratories in other countries. “Fermilab’s upcoming Deep Underground Neutrino Experiment (DUNE) for neutrino science and proton decay studies, for example, will feature contributions from scientists in dozens of countries,” Marc said.

FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

These international particle physics collaborations require Fermilab to transport large amounts of data around the globe quickly through high-throughput computing. To that end, Fermilab features 100Gbit connectivity with local, national, and international networks. The technology empowers researchers to quickly process these data to facilitate scientific discoveries.

A Repository for Large Sets of Valuable Scientific Data

Marc told us Fermilab also has mind-boggling storage capacity. “We’re the primary repository for all the data for all of the experiments here at the laboratory,” he said.

Fermilab’s tape libraries, fully automated and manned by robotic arms, provide more than 100 petabytes of storage capacity for data from particle physics and astrophysics experiments. “This includes a copy of the entire CMS experiment dataset and a copy of the dataset for every Fermilab experiment,” Marc said.

Fermilab also houses the entire dataset of The Sloan Digital Sky Survey (SDSS), a collaborative international effort to build the most detailed 3D map of the universe in existence.

Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

The data-rich project has measured compositions and distances of more than 3 million stars and galaxies and captured multicolor images of one-third of the sky.

The lab’s data management capabilities protect precious scientific data.

“SDSS was the first time there was an astronomical survey in which all data were digitized, much bigger than any survey done before,” Marc said. “In fact, even though the data collection has stopped, people are still actively using that dataset for current analysis.”

Marc said much of the particle physics research is done in concert with the academic community and can involve a significantly lengthy process.

“For example, the DUNE experiment is a worldwide collaboration that researchers have been developing for more than 10 years,” he said. “We are starting on the facility where the detector will go. The lifetime of a big experiment these days is measured in tens of years; even a small experiment with 100 collaborators easily takes 10 years to move forward.”

HEPCloud: A New Paradigm for Provisioning Computing Resources

HEPCloud will enable scientists to put computing resources to better use.

Particle physics has historically required extensive computing resources from sources such as local batch farms, grid sites, private clouds, commercial clouds, and supercomputing centers — plus the knowledge required to access and use the resources efficiently. Marc told us all that changes with HEPCloud, a new paradigm Fermilab is pursuing in particle physics computing. The HEPCloud facility will allow Fermilab to provision computing resources through a single managed portal efficiently and cost-effectively.

“HEPCloud is a significant initiative to both simplify how we use these systems and make the process more cost-effective,” Marc said. “Here at Fermilab, trying to provision enough resources to meet demand peaks is just too expensive, and when we’re not on peak, there’d be lots of unused resources.”

The technology will change the way physics experiments use computing resources by elastically expanding resource pools on short notice — for example, by renting temporary resources on commercial clouds. This will allow the facility to respond to peaks without over-provisioning local resources.

“HEPCloud is not a cloud provider,” Marc said. “It’s an intelligent brokerage system that can take a request for a certain amount of resources with a certain amount of data; a portal to use cloud resources, the open science grid, and even supercomputing centers such as the National Energy Research Scientific Computing Center (NERSC).”

Marc said the DOE funds a number of supercomputing sites across the country, and Fermilab’s goal is to make better use of those resources. “It’s not feasible for us to keep on growing larger with traditional computing resources,” Marc said. “So a good deal of our applied computing research is looking at how to do the kind of analysis we need to do on those machines.”

At the end of the day, Marc recognizes the importance of letting the public know how scientists, engineers, and programmers at Fermilab are tackling today’s most challenging computational problems. “This is taxpayer money, and we ought to be able to provide evidence that what we are doing is valuable and should be supported,” he said.

Ultimately, its solutions will help America stay at the forefront of innovation.

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
collaborate at Fermilab on experiments at the frontiers of discovery.

FNAL Short-Baseline Near Detector under construction

Dark Energy Camera [DECam], built at FNAL

From Gemini and Keck: “Dark Matter is a No Show in Ghostly Galaxy”

Gemini Observatory

Keck Observatory

Science Contacts:

Pieter van Dokkum
Astronomy Department
Yale University
pieter.vandokkum@yale.edu
Phone: 203-432-5048

Shany Danieli
Astronomy Department
Yale University
shany.danieli@yale.edu
Phone: 857-919-3674

Media Contacts:

Mari-Ela Chock
W.M. Keck Observatory
mchock@keck.hawaii.edu
Phone: 808-554-0567

Jasmin Silva
Gemini Observatory
jsilva@gemini.edu
Desk: 808 974-2575

Composite color image of NGC1052-DF2 constructed from observations using the Gemini Multi Object Spectrograph (GMOS) on Gemini North on Hawai‘i’s Maunakea. The ultra-diffuse galaxy was observed using deep imaging in two filters (g’ and i’). Image credit: Gemini Observatory/NSF/AURA/Keck/Jen Miller.

Left: The ultra-diffuse galaxy is swarming with globular clusters, which hold the key to understanding this mysterious object’s origin and mass.
Right: A closer look at one of the globular clusters within the galaxy, which are all much brighter than typical, the brightest emitting almost as much light as the brightest within the Milky Way. The spectrum, obtained by Keck Observatory shows the absorption lines used to determine the velocity of this object. Ten clusters were observed, providing the information needed to determine the mass of the galaxy, revealing its lack of dark matter. Image credit: Gemini Observatory/NSF/AURA/Keck/Jen Miller/Joy Pollard.

Astronomers using data from the Gemini and W. M. Keck Observatories in Hawai‘i have encountered a galaxy that appears to have almost no dark matter. Since the Universe is dominated by dark matter, and it is the foundation upon which galaxies are built, “…this is a game changer,” according to Principal Investigator Pieter van Dokkum of Yale University.

Galaxies and dark matter go hand in hand; you typically don’t find one without the other. So when researchers uncovered a galaxy, known as NGC1052-DF2, that is almost completely devoid of the stuff, they were shocked.

“Finding a galaxy without dark matter is unexpected because this invisible, mysterious substance is the most dominant aspect of any galaxy,” said lead author Pieter van Dokkum of Yale University. “For decades, we thought that galaxies start their lives as blobs of dark matter. After that everything else happens: gas falls into the dark matter halos, the gas turns into stars, they slowly build up, then you end up with galaxies like the Milky Way. NGC1052-DF2 challenges the standard ideas of how we think galaxies form.”

The research, published in the March 29th issue of the journal Nature, amassed data from the Gemini North and W. M. Keck Observatories, both on Maunakea, Hawai‘i, the Hubble Space Telescope, and other telescopes around the world.

Given its large size and faint appearance, astronomers classify NGC1052-DF2 as an ultra-diffuse galaxy, a relatively new type of galaxy that was first discovered in 2015. Ultra-diffuse galaxies are surprisingly common. However, no other galaxy of this type yet-discovered is so lacking in dark matter.

“NGC1052-DF2 is an oddity, even among this unusual class of galaxy,” said Shany Danieli, a Yale University graduate student on the team.

To peer even deeper into this unique galaxy, the team used the Gemini Multi Object Spectrograph (GMOS) to capture detailed images of NGC1052-DF2, assess its structure, and confirm that the galaxy had no signs of interactions with other galaxies.

“Without the Gemini images dissecting the galaxy’s morphology we would have lacked context for the rest of the data,” said Danieli. “Also, Gemini’s confirmation that NGC1052-DF2 is not currently interacting with another galaxy will help us answer questions about the conditions surrounding its birth.”

Van Dokkum and his team first spotted NGC1052-DF2 with the Dragonfly Telephoto Array, a custom-built telescope in New Mexico that they designed to find these ghostly galaxies.

U Toronta Dragon Fly Telescope Array housed in New Mexico

NGC1052-DF2 stood out in stark contrast when comparisons were made between images from the Dragonfly Telephoto Array and the Sloan Digital Sky Survey (SDSS).

The Dragonfly images show a faint “blob-like” object, while SDSS data reveal a collection of relatively bright point-like sources.

In addition to the Gemini observations, to further assess this inconsistency the team dissected the light from several of the bright sources within NGC1052-DF2 using Keck’s Deep Imaging Multi-Object Spectrograph (DEIMOS) and Low-Resolution Imaging Spectrometer (LRIS), identifying 10 globular clusters. These clusters are large compact groups of stars that orbit the galactic core.

The spectral data obtained on the Keck telescopes revealed that the globular clusters were moving much slower than expected. The slower the objects in a system move, the less mass there is in that system. The team’s calculations show that all of the mass in the galaxy could be attributed to the mass of the stars, which means there is almost no dark matter in NGC1052-DF2.

“If there is any dark matter at all, it’s very little,” van Dokkum explained. “The stars in the galaxy can account for all of the mass, and there doesn’t seem to be any room for dark matter.”

The team’s results demonstrate that dark matter is separable from galaxies. “This discovery shows that dark matter is real – it has its own separate existence apart from other components of galaxies,” said van Dokkum.

NGC1052-DF2’s globular clusters and atypical structure has perplexed astronomers aiming to determine the conditions this galaxy formed under.

“It’s like you take a galaxy and you only have the stellar halo and globular clusters, and it somehow forgot to make everything else,” van Dokkum said. “There is no theory that predicted these types of galaxies. The galaxy is a complete mystery, as everything about it is strange. How you actually go about forming one of these things is completely unknown.”

However, researchers do have some ideas. NGC1052-DF2 resides about 65 million light years away in a collection of galaxies that is dominated by the giant elliptical galaxy NGC 1052. Galaxy formation is turbulent and violent, and van Dokkum suggests that the growth of the fledgling massive galaxy billions of years ago perhaps played a role in NGC1052-DF2’s dark-matter deficiency.

Another idea is that a cataclysmic event within the oddball galaxy, such as the birth of myriad massive stars, swept out all the gas and dark matter, halting star formation.

These possibilities are speculative, however, and don’t explain all of the characteristics of the observed galaxy, the researchers add.

The team continues the hunt for more dark-matter-deficient galaxies. They are analyzing Hubble images of 23 other diffuse galaxies. Three of them appear to share similarities with NGC1052-DF2, which van Dokkum plans to follow up on in the coming months at Keck Observatory.

“Every galaxy we knew about before has dark matter, and they all fall in familiar categories like spiral or elliptical galaxies,” van Dokkum said. “But what would you get if there were no dark matter at all? Maybe this is what you would get.”

See the full article here .

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The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on 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 spectrometer and world-leading laser guide star adaptive optics systems. 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.

Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.

Gemini/North telescope at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope on Cerro Pachón in central Chile (Gemini South); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

From Science Blog from the SDSS: “APOGEE and Amateur Spectroscopy”

Science Blog from the SDSS

February 17, 2018
David Whelan

Drew Chojnowski, APOGEE plate designer and lead of the emission-line stars science group, discusses SDSS and Be stars observed with the APOGEE instrument.

This weekend, APOGEEans David Whelan and Drew Chojnowski attended the Sacramento Mountains Spectroscopy Workshop. The workshop’s goal? To get amateur astronomers interested in pursuing spectroscopy. With a mix of amateurs and professionals in the room, the expertise was readily available, and the excitement was palatable.

On Friday, David Whelan lead a discussion on spectral classification of intermediate- and high-mass stars. This is a science effort that is essential to both APOGEE’s emission-line stars group and high-mass stars studies more generally. Perhaps some knowledgeable amateurs can begin to contribute?

Then on Saturday, Drew introduced the group to observing with the Sloan Telescope. Below, he is shown with one of SDSS’s APOGEE plates.

Drew and an APOGEE plate – teaching people how the SDSS is done.

These kinds of workshops break down the barrier between the amateur and the professional, and opens both groups to new possibilities. With special thanks to the organizers Ken Hudson and Joe Daglen, as well as François Cochard from Shelyak Instruments, we very much look forward to pursuing the science generated by this workshop.

Amateur astronomer Joe Daglen, center, tells workshop attendants about the equipment that he uses to teach undergraduate students about imaging and spectroscopy.

See the full article here .

Please help promote STEM in your local schools.

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You can explore more on the SDSS Website.

From SDSS: “How massive is Supermassive? Astronomers measure more black holes, farther away”

SDSS Telescope at Apache Point Observatory, NM, USA, Altitude 2,788 meters (9,147 ft)

Sloan Digital Sky Survey

January 9, 2018
Today, astronomers from the Sloan Digital Sky Survey (SDSS) announced new measurements of the masses of a large sample of supermassive black holes far beyond the local Universe.

An artist’s rendering of the inner regions of an active galaxy/quasar, with a supermassive black hole at the center surrounded by a disk of hot material falling in. The inset at the bottom right shows how the brightness of light coming from the two different regions changes with time.
The top panel of the plot shows the “continuum” region, which originates close in to the black hole (the general vicinity is indicated by the “swoosh” shape). The bottom panel shows the H-beta emission line region, which comes from fast-moving hydrogen gas farther away from the black hole (the general vicinity is indicated by the other “swoosh”). The time span covered by these two light curves is about six months.
The bottom plot “echoes” the top, with a slight time delay of about 10 days indicated by the vertical line. This means that the distance between these two regions is about 10 light-days (about 150 billion miles, or 240 million kilometers). Image Credit: Nahks Tr’Ehnl (www.nahks.com) and Catherine Grier (The Pennsylvania State University) and the SDSS collaboration

The results, being presented at the American Astronomical Society (AAS) meeting in National Harbor, Maryland and published in The Astrophysical Journal, represent a major step forward in our ability to measure supermassive black hole masses in large numbers of distant quasars and galaxies.

“This is the first time that we have directly measured masses for so many supermassive black holes so far away,” says Catherine Grier, a postdoctoral fellow at the Pennsylvania State University and the lead author of this work. “These new measurements, and future measurements like them, will provide vital information for people studying how galaxies grow and evolve throughout cosmic time.”

Supermassive Black Holes (SMBHs) are found in the centers of nearly every large galaxy, including those in the farthest reaches of the Universe. The gravitational attraction of these supermassive black holes is so great that nearby dust and gas in the host galaxy is inexorably drawn in. The infalling material heats up to such high temperatures that it glows brightly enough to be seen all the way across the Universe. These bright disks of hot gas are known as “quasars,” and they are clear indicators of the presence of supermassive black holes. By studying these quasars, we learn not only about SMBHs, but also about the distant galaxies that they live in. But to do all of this requires measurements of the properties of the SMBHs, most importantly their masses.

The problem is that measuring the masses of SMBHs is a daunting task. Astronomers measure SMBH masses in nearby galaxies by observing groups of stars and gas near the galaxy center — however, these techniques do not work for more distant galaxies, because they are so far away that telescopes cannot resolve their centers. Direct SMBH mass measurements in galaxies farther away are made using a technique called “reverberation mapping.”

Reverberation mapping works by comparing the brightness of light coming from gas very close in to the black hole (referred to as the “continuum” light) to the brightness of light coming from fast-moving gas farther out. Changes occurring in the continuum region impact the outer region, but light takes time to travel outwards, or “reverberate.” This reverberation means that there is a time delay between the variations seen in the two regions. By measuring this time delay, astronomers can determine how far out the gas is from the black hole. Knowing that distance allows them to measure the mass of the supermassive black hole — even though they can’t see the details of the black hole itself.

Over the past 20 years, astronomers have used the reverberation mapping technique to laboriously measure the masses of around 60 SMBHs in nearby active galaxies. Reverberation mapping requires getting observations of these active galaxies, over and over again for several months — and so for the most part, measurements are made for only a handful of active galaxies at a time. Using the reverberation mapping technique on quasars, which are farther away, is even more difficult, requiring years of repeated observations. Because of these observational difficulties, astronomers had only successfully used reverberation mapping to measure SMBH masses for a handful of more distant quasars — until now.

A graph of known supermassive black hole masses at various “lookback times,” which measures the time into the past we see when we look at each quasar.
More distant quasars have longer lookback times (since their light takes longer to travel to Earth), so we see them as they appeared in the more distant past. The Universe is about 13.8 billion years old, so the graph goes back to when the Universe was about half of its current age.
The black hole masses measured in this work are shown as purple circles, while gray squares show black hole masses measured by prior reverberation mapping projects. The sizes of the squares and circles are related to the masses of the black holes they represent. The graph shows black holes from 5 million to 1.7 billion times the mass of the Sun.
Image Credit: Catherine Grier (The Pennsylvania State University) and the SDSS collaboration

In this new work, Grier’s team has used an industrial-scale application of the reverberation mapping technique with the goal of measuring black hole masses in tens to hundreds of quasars. The key to the success of the SDSS Reverberation Mapping project lies in the SDSS’s ability to study many quasars at once — the program is currently observing about 850 quasars simultaneously. But even with the SDSS’s powerful telescope, this is a challenging task because these distant quasars are incredibly faint.

“You have to calibrate these measurements very carefully to make sure you really understand what the quasar system is doing,” says Jon Trump, an assistant professor at the University of Connecticut and a member of the research team.

Improvements in the calibrations were obtained by also observing the quasars with the Canada-France-Hawaii-Telescope (CFHT) and the Steward Observatory Bok telescope located at Kitt Peak over the same observing season.

CFHT, at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

Bok Telescope U Arizona Steward Observatory, 2.3-metre Bok Telescope at the Steward Observatory at Kitt Peak in Arizona, USA altitude 2,096 m (6,877 ft)

After all of the observations were compiled and the calibration process was completed, the team found reverberation time delays for 44 quasars. They used these time delay measurements to calculate black hole masses that range from about 5 million to 1.7 billion times the mass of our Sun.

“This is a big step forward for quasar science,” says Aaron Barth, a professor of astronomy at the University of California, Irvine who was not involved in the team’s research. “They have shown for the first time that these difficult measurements can be done in mass-production mode.”

These new SDSS measurements increase the total number of active galaxies with SMBH mass measurements by about two-thirds, and push the measurements farther back in time to when the Universe was only half of its current age. But the team isn’t stopping there — they continue to observe these 850 quasars with SDSS, and the additional years of data will allow them to measure black hole masses in even more distant quasars, which have longer time delays that cannot be measured with a single year of data.

“Getting observations of quasars over multiple years is crucial to obtain good measurements,” says Yue Shen, an assistant professor at the University of Illinois and Principal Investigator of the SDSS Reverberation Mapping project. “As we continue our project to monitor more and more quasars for years to come, we will be able to better understand how supermassive black holes grow and evolve.”

The future of the SDSS holds many more exciting possibilities for using reverberation mapping to measure masses of supermassive black holes across the Universe. After the current fourth phase of the SDSS ends in 2020, the fifth phase of the program, SDSS-V, begins. SDSS-V features a new program called the Black Hole Mapper, which plans to measure SMBH masses in more than 1,000 more quasars, pushing farther out into the Universe than any reverberation mapping project ever before.

“The Black Hole Mapper will let us move into the age of supermassive black hole reverberation mapping on a true industrial scale,” says Niel Brandt, a professor of Astronomy & Astrophysics at the Pennsylvania State University and a long-time member of the SDSS. “We will learn more about these mysterious objects than ever before.”

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The SDSS began regular survey operations in 2000, after a decade of design and construction. It has progressed through several phases, SDSS-I (2000-2005), SDSS-II (2005-2008), SDSS-III (2008-2014), and SDSS-IV (2014-). Each of these phases has involved multiple surveys with interlocking science goals. The three surveys that comprise SDSS-IV are eBOSS, APOGEE-2, and MaNGA, described at the links below. You can find more about the surveys of SDSS I-III by following the Prior Surveys link.

Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS- IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is http://www.sdss.org.

SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatory of China, New Mexico State University, New York University, University of Notre Dame, Observatório Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University.

From Universe Today: “Ancient Impacts Shaped the Structure of the Milky Way”

Universe Today

Accroding to new research, the Milky Way may still bear the marks of “ancient impacts”. Credit: NASA/Serge Brunier.

18 July , 2017
Matt Williams

Understanding how the Universe came to be is one of the greater challenges of being an astrophysicist. Given the observable Universe’s sheer size (46.6 billion light years) and staggering age (13.8 billion years), this is no easy task. Nevertheless, ongoing observations, calculations and computer simulations have allowed astrophysicists to learn a great deal about how galaxies and larger structures have changed over time.

For example, a recent study by a team from the University of Kentucky (UK) has challenged previously-held notions about how our galaxy has evolved to become what we see today. Based on observations made of the Milky Way’s stellar disk, which was previously thought to be smooth, the team found evidence of asymmetric ripples. This indicates that in the past, our galaxy may have be shaped by ancient impacts.

The study, titled “Milky Way Tomography with K and M Dwarf Stars: The Vertical Structure of the Galactic Disk“, recently appeared in the The Astrophysical Journal. Led by Deborah Ferguson, a 2016 UK graduate, the team consisted of Professor Susan Gardner – from the UK College of Arts and Sciences – and Brian Yanny, an astrophysicist from the Fermilab Center for Particle Astrophysics (FCPA).

This study evolved from Ferguson’s senior thesis, which was overseen by Prof. Gardner. At the time, Ferguson sought to expand on previous research by Gardner and Yanny, which also sought to understand the presence of ripples in our galaxy’s stellar disk. For the sake of this new study, the team relied on data obtained by the Sloan Digital Sky Survey‘s (SDSS) 2.5m Telescope, located at the Apache Point Observatory in New Mexico.

SDSS Telescope at Apache Point Observatory, NM, USA

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