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.

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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

IYL2015 Post: SDSS Plates (in Retirement!)

As part of Dresdner Lichtjahr 2015 [Dresden Year of Light 2015], you can now see a previously-used SDSS plate on display at Technische Sammlungen der Stadt Dresden, a museum located in a former Dresden factory. The exhibit will run through June of 2016, and has some really awesome demonstrations of how light propagates, and how much today’s technology depends on light.  Technische_SammlungenThe SDSS plate (below, designated plate 4385) is suspended above a table illustrating principles of how light propagates, what we can do with light of different wavelengths, and a demonstration of fiber optics. If you’re curious why our telescope might need need a metal plate, read this previous post.

Technische_Sammlungen2Used SDSS plates are available for educational purposes by schools, museums, astronomy clubs, and other educational & community organizations. Just contact someone at your nearest SDSS member institution to get started!

Technische_Sammlungen3Elsewhere in the exhibit and the museum, you can find a working infrared camera (selfie-compatible!), a very challenging puzzle involving prisms and laser light, and other neat activities suitable for children of all ages.

While you’re in Dresden, make sure to also stop by the Mathematische-Physikalische Salon [Royal Cabinet of Mathematical and Physical Instruments], at the Zwinger Palace in the center of Dresden, to have a look at old telescopes, clocks, and surveying tools. Of special interest to telescope enthusiasts are two very early reflector telescopes (i.e., telescopes that use a mirror to focus the incoming light, rather than lenses). You can also see them online in a panoramic view (upstairs in “Instruments of Enlightenment”).


This post is part of the SDSS Celebration of the International Year of Light 2015, in which we aim to post an article a month in support of the celebration of light.