P-MaNGA: Emission Lines Properties – Gas Ionisation and Chemical Abundances from Prototype Observations

(The following is a guest post by Francesco Belfiore, a PhD student at Cambridge University’s Kavli Institute for Cosmology, and summarizes his recent paper, which uses preliminary MaNGA data to map gas ionisation in several galaxies.)

Galaxies have long been considered island universes. Ordinarily separated by huge cosmological distances (of the order of millions of light years), most galaxies are not interacting in any visible way with their environment. However, modern theories of galaxy evolution claim otherwise. Starburst galaxies (galaxies which are experiencing a rate of formation of new stars much higher than normal) are known to expel large amounts of ionised (and possibly also neutral) gas towards the intergalactic voids. Supermassive black holes, which we believe to live in the centres of most galaxies, can also give rise to powerful outflows during periods of accretion (when the black hole has “switched on” and is feeding on the surrounding material). Some of these events are violent enough to totally strip a galaxy of its fuel: the gas. Without gas, a galaxy loses its ability to form new stars and becomes progressively older. In a sense, the galaxy has “died”.

This is not the whole story, however.

Continue reading

Integral Field Spectroscopy 101

As frequent readers know, the SDSS-IV-MaNGA survey plans to obtain spatially-resolved spectra of somewhere in the neighborhood of 10,000 galaxies using a technique called integral-field spectroscopy (or IFS). IFS essentially relies on placing an array of fiber-optic cables over an object of interest in the sky, and using the fiber-optics to pipe the light into a spectrograph, which produces the useful data by breaking up that light into its constituent wavelengths (an easy way you can do this at home is with a glass prism). The array of fibers is nicknamed a “bundle,” which is a pre-packaged grouping of fibers that we know the arrangement, and packaging the fibers allows more observational efficiency, since we don’t have to re-position the telescope to make a measurement of the same galaxy at a slightly different point.

However, the specific design of the fiber bundles is an important problem. Continue reading

SDSS in the News (Aug-Nov 2014)

Back in mid August I set up a Google alert search on “sloan digital sky surveys”. Here is a summary of 3 months of mentions of SDSS in online news:

August 21st: Discovery of one of the oldest stars in the Universe, SDSS J0018-0939, illustrated with SDSS image of the star:
Space Fellowship.com, IBTimes, KRWG.org

Oldeststar

An optical image of the star SDSS J0018-0939, obtained by the Sloan Digital Sky Survey. This is a low-mass star with a mass about half that of the Sun; the distance to this star is about 1000 light years; its location in the sky is close to the constellation Cetus. (Credit: SDSS/NAOJ)

 

 

Sept 10th, 21st: A report on looking for patterns in the properties of quasars using SDSS spectra:
Arstechnica.com, ScienceCodex.com.

Sept 25th: Discovery of ‘hyper-compact star clusters’ helped by SDSS data: SpartanDaily

Oct 3rd: “Artificial Intelligence Opens a New Window to the Universe”, Huffington Post.

“Robotic telescopes constantly collect astronomical data and generate enormous astronomical databases. For instance, Sloan Digital Sky Survey (SDSS) has imaged over 400 million galaxies since it saw first light in 2000. ”

So obviously this mentions SDSS, but implies it’s a robotic telescope!  Our team of observers, plate pluggers, and drillers, and the hundreds of other people who work hard to keep SDSS observing might object to this….

D120330_07_PlugCrewAfter100kFibers.500

In March 2012, BOSS observed 103,000 spectra, each of which was routed through a fiber-optic cable that was plugged by hand. The industrious APO plugging crew is pictured here showing the deleterious effects of having placed more than 2,000 fibers/finger in a month. But don’t worry, they recovered have continued to plug every fibre optic by hand during the day at APO – they might even be doing it as you read this! (Image Credit: Dan Long, APO).

Amazing that our observing process is so smooth that to outsiders it appears to be like a robot! Stay tuned for a newly planned “The SDSS Telescope is not Robotic” article. 🙂

Oct 8th:
Opinion: “Why More Inventions Don’t Win Nobel Prizes, and Why That’s a Good Thing”, National Geographic.

Cites SDSS as one of the reasons it was right that the invention of the CCD got the 2009 Nobel Prize in Physics because of the realms of discovery it opened up:

“The world could get along well without camera cell phones. What’s exciting about CCDs, whose inventors won the 2009 physics prize, is their use in the Hubble Space Telescope and the Sloan Digital Sky Survey.”

Oct 10th: “New Study of Spiral Arms”, Phys.org

Authors use a sample of 50 non-barred and two armed spiral galaxies selected from SDSS and measure spiral arm pitch angles, finding most are only approximately log spiral, typically having decreasing pitch angle as radius increased. Link to paper.

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NGC 3338, a non-barred two armed spiral in the study. Credit: SDSS.

 

 

Oct 17th: “A 3D Map of true Adolescent Universe”, SpatialNews, RDMag, Nature World News.
Discussion of plans for new redshift surveys mentions SDSS as “The first big 3D map of the universe”:

Oct 22nd: “Chandra Data Archive Comes to Life”, RedOrbit

Report on release of images from the Chandra archive, which us SDSS images (among many others) to make nice multi wavelength images, like the below one of NGC 4736.

NGC 4736 (also known as Messier 94) is a spiral galaxy that is unusual because it has two ring structures. This galaxy is classified as containing a “low ionization nuclear emission region,” or LINER, in its center, which produces radiation from specific elements such as oxygen and nitrogen. Chandra observations (gold) of NGC 4736, seen in this composite image with infrared data from Spitzer (red) and optical data from Hubble and the Sloan Digital Sky Survey (blue), suggest that the X-ray emission comes from a recent burst of star formation. Part of the evidence comes from the large number of point sources near the center of the galaxy, showing that strong star formation has occurred. In other galaxies, evidence points to supermassive black holes being responsible for LINER properties. Chandra’s result on NGC 4736 shows LINERs may represent more than one physical phenomenon. (X-ray: NASA/CXC/Universita di Bologna/S.Pellegrini et al, IR: NASA/JPL-Caltech; Optical: SDSS & NASA/STScI)

NGC 4736 (also known as Messier 94) is a spiral galaxy that is unusual because it has two ring structures. This galaxy is classified as containing a “low ionization nuclear emission region,” or LINER, in its center, which produces radiation from specific elements such as oxygen and nitrogen. Chandra observations (gold) of NGC 4736, seen in this composite image with infrared data from Spitzer (red) and optical data from Hubble and the Sloan Digital Sky Survey (blue), suggest that the X-ray emission comes from a recent burst of star formation. Part of the evidence comes from the large number of point sources near the center of the galaxy, showing that strong star formation has occurred. In other galaxies, evidence points to supermassive black holes being responsible for LINER properties. Chandra’s result on NGC 4736 shows LINERs may represent more than one physical phenomenon. (X-ray: NASA/CXC/Universita di Bologna/S.Pellegrini et al, IR: NASA/JPL-Caltech; Optical: SDSS & NASA/STScI)

 

Oct 27th: “Nothing Can Escape Black Holes – this Lucky Star Did”, TechTimes
Study which revealed a star loosing a portion of its mass to a black hole used some SDSS data.

Oct 31st: “Universe May Face a Darker Future”, PhysOrg, TechTimes, Digital Journal.

Cosmologists use galaxies observed by the Sloan Digital Sky Survey to study the nature of dark energy and find support for a scenario in which dark matter decays into dark energy.

Nov 4th: “The Rise of Astrostatistics”, Symmetry Magazine.

“I believe the large surveys shocked astronomers with how much data there is,” Hilbe says. “The Sloan Digital Sky Survey [one of the first automated and digitized comprehensive astronomical sky surveys] told them they needed statistics.”

Notice another mention of SDSS applying the process is automated, which we addressed above (thanks again to our wonderful observing team). Apparently this idea is fairly ubiquitous in the media….

astrostatistics_header_Artwork by Sandbox Studio, Chicago with Kimberly Boustead

Neat illustration of astrostatistic: Artwork by Sandbox Studio, Chicago with Kimberly Boustead for Symmetry Magazine article.

 

 

Nov 6th:  “Never has so much data been collected so fast” Edmonton Journal.
Article about big data in astronomy begins:

“When the Sloan Digital Sky Survey began in 2000, its telescope in New Mexico collected more data in its first few weeks than had been amassed in the entire history of astronomy.”

Nov 7th: “Exploring the Murky Centers of Dust Shrouded Galaxies”, PhysOrg, Science World Report.

Articles use an SDSS image to illustrate the LMT pointing at galaxy 5MUSES-229, one of the dusty galaxies in the study which was used to study the relative contributions of AGN and star formation in the heating of dust.

usandmexican

The LMT pointed at 5MUSES-229, a galaxy approximately one billion light years distant from the Milky Way. With the LMT, astronomers are able to observe the carbon monoxide emission from this galaxy. Credit: James Lowenthal, the background image showing the galaxy is from SDSS.

 

Nov 14th: “How Young, Massive, Compact Galaxies Evolve into Their Red, Dead Elders”, Science World Report.

Report on study using a sample of poststarburst galaxies identified in SDSS and followed up with HST and Chandra.

 


 

 

To set up your own alert, visit news.google.com, search on “sloan digital sky survey” and click “Create alert” which can be found at the bottom on the page.

 

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BOSS Completes its Main Survey of Distant Galaxies and Quasars!

The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) has completed its main survey of galaxies and quasars. With 1.35 million luminous red galaxies and 230,000 quasars across 10,200 square degrees of the sky, BOSS has exceeded the number of objects and sky area goals from the original SDSS-III proposal.

Reaching this milestone involved the hard work and efforts of many people. In particular, the mountain and observing staff at Apache Point Observatory have been worked hard and efficiently to observe 2,300 plates with the new BOSS spectrograph in 4.5 years of dark time.

survey_mollweide_DR12

The coverage map of the completed BOSS main survey in equatorial coordinates with (RA, Dec)=(90,0) in the center of the image. Completed areas are shown in light blue and yellow. The red area is a 10,500 deg^2 region from which observations were selected. The project goal was to observe the 10,000 deg^2 footprint above declination -3 deg. A 200 deg^2 region was added between declinations of -3 deg to -7 deg to provide overlap with the Dark Energy Survey.

For the remaining 3 months of SDSS-III, the BOSS spectrograph continues to observe new interesting classes of objects as part of a set of ancillary proposals that were internally competed within the SDSS-III collaboration.

All of SDSS-I, SDSS-II, and SDSS-III/SEGUE observed 1.84 million survey-quality spectra with the original SDSS spectrograph during the timeframe 1999-2009. SDSS-III DR12 will be released publicly in 2014 December and the final BOSS data in DR12 is expected to exceed 2.7 million survey-quality spectra, including calibration targets, stars, repeated observations, and ancillary programs.

The Most Precise Measurement Yet of the Expanding Universe

More exciting news from the SDSS! A worldwide team of SDSS astronomers has completed the most precise measurement of the expanding universe ever. The result was announced just hours ago at the meeting of the American Physical Society in Savannah, Georgia.

Click on the illustration below to go to the SDSS press release describing this exciting news!

 

Yellow lines showing light paths pass through circles of increasing size. Each              circle shows in purple the structure of galaxies in the universe at some point in the past.

An illustration of how astronomers used quasar light to trace the expansion of the universe.