Where does my favourite MaNGA galaxy live? ¿Dónde vive mi galaxia MaNGA favorita?

This is a guest post by María Argudo-Fernández (University of Antofagasta).
Esta entrada de blog está escrita por nuestra invitada María Argudo-Fernández (Universidad de Antofagasta).

It is well known that the environment where a galaxy resides plays an important role in its formation and evolution. Galaxies in the MaNGA sample have many different morphologies. There are elliptical, lenticular, and spiral galaxies, but there are also peculiar galaxies such as dwarfs and mergers or interacting galaxies. There are also very bright and large galaxies, with many many stars, but MaNGA is also observing smaller and fainter galaxies. All of these are properties that we know have some relation with the galaxy environment. For example, there are more elliptical galaxies in denser environments than you can find in the field, which is mainly populated by spiral galaxies. This relation is known as the morphology-density relation.

Es bien conocido que el entorno donde viven las galaxias juega un papel importante en su formación y evolución. Las galaxias de la muestra de MaNGA muestran muchas formas diferentes. Hay galaxias que son elípticas, lenticulares y espirales, pero también hay galaxias peculiares como galaxias enanas y fusiones de galaxias o galaxias en interacción. También hay galaxias de gran tamaño, galaxias con muchísimas estrellas y galaxias muy brillantes, aunque MaNGA también ha observado galaxias más pequeñas y galaxias más débiles. Todas estas son propiedades que sabemos que tienen una relación con el entorno. Por ejemplo, se pueden encontrar más galaxias de tipo elíptico en entornos más densos que en el campo, el cual está poblado mayormente por galaxias de tipo espiral. Esta relación se conoce como la relación morfología-densidad.

Messier 51, The Whirlpool Galaxy. The diameter of this spiral galaxy is roughly 75,000 light years, and it is interacting with a smaller neighbour on the left. Credit: The Sloan Digital Sky Survey.
Messier 51, o la Galaxia del Remolino. El diámetro de esta galaxia espiral es de unos 75,000 años luz, y está en interacción con la pequeña galaxia vecina de la izquierda. Crédito: The Sloan
Digital Sky Survey.

MaNGA is opening a new window for observing nearby galaxies. For instance, MaNGA is allowing us to study how galaxies are forming new stars or how galaxies are quenching their star formation. We can also explore how and how fast stars and gas are moving within galaxies, or how old the stars are in different regions of the galaxies (for example bulge and disk). Now it’s our time to investigate what is the role of the environment on these properties, and for that we need to characterise the neighbourhood of the MaNGA galaxies.

MaNGA está abriendo una nueva forma de observar galaxias cercanas. Por ejemplo, MaNGA nos está permitiendo estudiar cómo las galaxias están formando nuevas estrellas o cómo está cesando su formación estelar. También podemos explorar cómo y cuán rápido se mueven las estrellas y el gas dentro de las galaxias, o qué edad tienen las estrellas en diferentes zonas de las galaxias (por ejemplo en el bulbo o en el disco). Ahora es nuestra oportunidad para investigar el papel que juega el entorno en estas propiedades, y para ello necesitamos caracterizar el vecindario alrededor de las galaxias de MaNGA.

How can we do this? We first need to understand how galaxies are distributed. Galaxies are not homogeneously distributed in the Universe. Through gravitational influence galaxies tend to cluster in larger structures as clusters, filaments, and walls, leaving large voids between them.

To better understand this let’s think about people. People are not homogeneously distributed on the planet, and their numbers grow somehow affected by the conditions of the region they live in. The highest populations are concentrated in the largest cities, in the order of tens of millions, and surrounded by suburbs. Moving away from the city we find smaller cities, villages, and in a very extreme situation we could find tribes and hermits in the most isolated regions.

Slices through the SDSS 3-dimensional map of the distribution of galaxies. Earth is at the center, and each point represents a galaxy, typically containing about 100 billion stars. The outer circle is at a distance of two billion light years. Credit: M. Blanton and the Sloan Digital Sky Survey.
Porción del mapa tridimensional de la distribución de las galaxias del SDSS. La Tierra se encuentra en el centro y cada punto representa una galaxia, conteniendo cada una del orden de 100 mil millones de estrellas. El círculo exterior se encuentra a una distancia de dos mil millones de años luz. Créditos: ​M. Blanton y el Sloan Digital Sky Survey.

¿Cómo podemos hacerlo? Tenemos que parametrizar el vecindario alrededor de cada galaxia de MaNGA. Primero necesitamos entender cómo se distribuyen las galaxias. La distribución de las galaxias en el universo no es homogénea. Las galaxias tienden a agruparse por influencia gravitatoria en estructuras cada vez más densas, como cúmulos, filamentos y paredes, dejando grandes vacíos entremedio.

Para entender esto mejor pensemos acerca de las personas. Las personas no están distribuidas homogéneamente en el planeta, y de alguna forma crecen influenciadas por las condiciones de la región en la que viven. Las mayores concentraciones de personas se encuentran en las ciudades más grandes, del orden de decenas de millones, que están además rodeadas de suburbios. Conforme nos alejamos de las grandes ciudades encontramos ciudades más pequeñas, pueblos, y en situaciones más extremas, incluso tribus y personas ermitañas en las regiones más aisladas.

We have some methods to identify the neighbourhood around galaxies. We first define a perimeter (what we name a physical volume) around each MaNGA galaxy. This perimeter can contain a few houses around each galaxy (what we refer as the local environment), a district (what we refer as the intermediate or group environment), or a full city (what we refer as the large-scale environment). We then calculate different parameters in these volumes. For example the local density parameter tells us how many neighbour galaxies are living in that volume. Another parameter, the tidal strength, estimate the gravitational influence that each neighbour galaxy exerts on our favourite MaNGA galaxy. We also use more sophisticated methods to relate MaNGA galaxies with the biggest structures in the Universe (clusters, filaments, sheets, and voids).

Nosotros tenemos algunos métodos para identificar el vecindario alrededor de las galaxias. Para ello primero definimos un perímetro alrededor de cada galaxia de MaNGA (lo que llamamos un volumen físico). Éste perímetro puede contener desde unas pocas casas alrededor (a lo que nos referimos como entorno local), un barrio (a lo que nos referimos como entorno intermedio o grupal), o una ciudad completa (a lo que nos referimos como entorno a gran escala). Una vez definidos estos volúmenes podemos calcular diferentes parámetros. La densidad local, por ejemplo, nos dice cuántas galaxias vecinas viven en ese volumen. Con otro parámetro, el parámetro de marea, estimar la influencia gravitatoria que ejercen todas las galaxias vecinas en mi galaxia MaNGA favorita. También usamos otros parámetros más sofisticados para relacionar las galaxias de MaNGA con las mayores estructuras del universo (los cúmulos, los filamentos, las paredes y los vacíos).

In the Galaxy Environment for MaNGA Galaxies (GEMA) value added catalogue we are providing the quantification of the environment for all MaNGA galaxies observed in the Fiftheenth Data Release of the Sloan Digital Sky Survey (DR15). We have compiled these and other environment parameters, and some of them have been already used to explore the influence on the environment on MaNGA galaxies. For example, using the tidal strength, we have found that the galaxies with counter-rotating stars and gas tend to be more isolated than galaxies where the gas is rotating the same direction than their stars (Chen et al. 2017​, Jin et al. 2017). On the other hand, it seems that the age and metallicity gradients in galaxies (from the center of the galaxies to the outskirts) are not affected by the local and the large-scale environments (Zheng et al. 2017, Goddard et al. 2017).

The GEMA catalogue is publicly available in DR15 here! You can play with it to explore where you favourite MaNGA galaxy lives.

En el catálogo de valor añadido GEMA (Galaxy Environment for MaNGA Galaxies, por sus siglas en inglés), proveemos la cuantificación del entorno para las galaxias de MaNGA observadas en el SDSS-DR15. Hemos calculado éstos y otros parámetros de entorno, donde ya hemos usado algunos de ellos para explorar la influencia del entorno en galaxias de MaNGA. Por ejemplo, hemos encontrado que las galaxias donde sus estrellas y el gas están contra-rotando tienden a estar más aisladas que galaxias similares pero donde sus estrellas y el gas rotan en el mismo sentido (Chen et al. 2017​, Jin et al. 2017). Por otra parte, parece que los gradientes de la edad y metalicidad en las galaxias (desde el centro hacia las partes externas) no están afectados ni por el entorno local ni por el entorno a gran escala (Zheng et al. 2017, Goddard et al. 2017).

El catálogo GEMA está disponible al público en el DR15! Te invitamos a jugar con él para explorar dónde vive tu galaxia MaNGA favorita.

A galaxy observed with MaNGA, showing from left to right: stellar velocity field, Hα emission line map, galactic gas velocity field. In the velocity fields: blue is moving towards us, and red away from us.
Credit: Francesco Belfiore, Univ. of St Andrews Print & Design.
Ejemplo de una galaxia observada por MaNGA, de izquierda a derecha se muestra: mapa de velocidad estelar, mapa de línea de emisión Hα y mapa de velocidad del gas. En los maps de velocidad: la parte en azul se mueve hacia nosotros, y la parte en rojo se aleja. Créditos: Francesco Belfiore, Univ. of St Andrews Print & Design.

Getting a handle on MaNGA’s cold gas with the HI-MaNGA survey

This is a guest post by David V. Stark (Kavli Institute for the Physics and Mathematics of Universe, University of Tokyo).

The SDSS-IV MaNGA survey is providing the most comprehensive census of the stellar and ionized gas content of local galaxies to date, but there is another major component of galaxies the SDSS telescope does not see: the cold gas. Cold gas plays the key role of fueling the formation of new stars. Galaxies with ongoing star formation tend to have lots of cold gas, while those with no ongoing star formation have very little cold gas. Figuring out how and why galaxies acquire, consume, and/or lose their gas over time is fundamentally important to our understanding of galaxy evolution as a whole.

Typically, the largest component of cold gas within galaxies takes the form of neutral hydrogen atoms floating around at very low densities. In the astronomical community, this component is referred to as HI (which in this case is not an enthusiastic greeting, but is rather pronounced “H one”). Our ability to see HI is thanks to a very small transition within hydrogen atoms where the proton and electron go from spinning in the same direction to spinning in opposite directions. This “spin-flip” transition releases a tiny amount of energy in the form a electromagnetic radiation with a wavelength of 21 centimeters. Such a long wavelength lies in the radio regime of the electromagnetic spectrum, so is invisible to optical telescopes like that used for the MaNGA survey. Thankfully there are radio telescopes specifically designed to detect this radiation.

The HI-MaNGA survey led by Professor Karen Masters and myself is an ongoing observing program to measure the HI content of MaNGA galaxies using the 100m Green Bank Telescope (GBT). Located within the Radio Quiet Zone of West Virginia, USA, the GBT is one of the world’s premier radio telescopes, and its large collecting area and “quiet” surroundings makes it an excellent tool to measure the faint 21cm emission from MaNGA galaxies that lie as much as hundreds of megaparsecs away.

The Green Bank Telescope (image credit: NRAO/AUI)

The GBT cannot provide pictures of MaNGA galaxies in the same way as optical telescopes, but rather acts like a spectrometer with a single spatial pixel that measures all the emission from an area on the sky that is about 270 times larger than a single fiber in the MaNGA IFUs. So while we do not map the HI within galaxies, we do measure the integrated radio spectrum emitted by each galaxy. From this spectrum we can measure two fundamental properties: (1) The total amount of light emitted at 21cm, which is directly proportional to the amount of HI gas, and (2) the spread of the 21cm emission line, which reflects a galaxy’s rotation speed and can be used to place crucial constraints on the total enclosed mass (stars, gas, and dark matter).

(left) A MaNGA galaxy with the IFU bundle shape overlaid in purple. (right) The GBT spectrum for this galaxy showing a clear detection of 21cm emission. Wavelength has been converted into recession velocity using the Hubble Law . The total area under the emission line is directly proportional to the total HI present in this galaxy, while the width of the emission line indicates this galaxy’s rotation speed. Figure taken from Masters et al. (submitted).

Data for the first 331 galaxies from HI-MaNGA has been released as a Value Added Catalog in SDSS Data Release 15, with both the processed radio spectra and derived properties made available. This first release is just a taste of what is to come; additional data has been collected for over 2000 additional MaNGA galaxies, and observations are continuing as we speak. This work would not be possible without the amazing team of undergradute and graduate students who have helped with, and continue to help with, observations and data reduction: Zach Pace, Frederika Phipps, Alaina Bonilla, Nile Samanso, Catherine Witherspoon, Catherine Fielder, Emily Harrington, Shoaib Shamsi, Daniel Finnegan, and Lucy Newnham.

Stay tuned for a lot more data and a ton of interesting science!

The Open Cluster Chemical Abundance and Mapping Survey

Guest post by John Donor.


Astronomers have always been fond of the Milky Way, after all, it is our home. But it’s more than just our home, it’s also our most important laboratory for studying galaxy evolution. We can study the Milky Way in tremendous detail, compared to any other galaxy. So what does our host galaxy tell us about galaxy evolution?

Let’s start at the very beginning (as Julie Andrews said, “a very good place to start”). I literally mean the very beginning: the Big Bang. While the “bang” itself was perhaps the most exciting event in cosmic history, the aftermath of the Big Bang was really rather dull. After the Universe calmed down a bit, all of existence was just endless clouds of gas; Hydrogen and Helium gas to be precise. No stars. No galaxies. Certainly no planets or life.

But fortunately this boring state of affairs quickly corrected itself. As gravity took over, gas began to collect into what would become galaxies. As the gas collected, it slowly became dense enough to form the first stars. Stars are very exciting. In their hot, dense cores, they fuse Hydrogen and Helium into the heavier elements (Carbon, Oxygen, Iron, etc.) that we’re all more familiar with. And when they die, they often die spectacularly in supernovae.

Star deaths are particularly important to our story because that’s how heavier elements (everything besides Hydrogen and Helium) are released into a galaxy. But death is not the end! There’s still plenty of gas in a galaxy, so it forms more stars, now with a slightly higher concentration of heavier elements in them from the previous generation of stars. This is the life-cycle of a galaxy: make stars, become enriched by dying stars, make more stars, repeat. Galaxies aren’t homogenous blobs though: they have interesting structure such as spiral arms and central bulges. Due to the effects of gravity, their mass tends to be more concentrated at their centers. More mass means more stars. More stars means more heavy elements enriching the gas in that part of the galaxy.

A simple illustration of the build up of heavier elements in a galaxy (credit: ESA/Hubble & NASA).

This very simple model already points us towards a key piece of observational evidence in studying galaxy evolution: chemical enrichment. Or more specifically, the rate at which that chemical enrichment changes as we move through the galaxy. To measure chemical enrichment, astronomers often simply measure Iron (Fe) and Hydrogen (H). The ratio of Iron to Hydrogen (Fe/H) gives an exact numerical representation of the level of chemical enrichment, often called “metallicity”. The exact rate at which Fe/H changes with respect to the distance from the center of the galaxy, or the Galactic metallicity gradient, has been the topic of numerous studies dating as far back as 1979.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has made measurements of the chemical enrichment (Fe/H) of over 200,000 stars to date. But this is only half the battle. To measure the Galactic metallicity gradient, distances from the center of the Galaxy are needed as well. This might seem easy: measuring distance from the Galactic center is a simple geometry problem, if you know exactly where the object you’re measuring is. Unfortunately, finding the distance to celestial objects can be difficult.
There are a variety of methods for finding astronomical distances, but almost all of them focus on finding the actual intrinsic brightness of an object. Since brightness decreases predictably as we move farther from an object, a change in brightness (intrinsic – observed) must correspond to a certain distance. Of course the observed brightness is very easy to measure! Finding the intrinsic brightness is the focus of entire sub-fields in astronomy.

The perfect measuring stick for studying the galactic abundance gradient will then have both (relatively) easily measured chemistry and a measured reliable distance. Among the best objects fitting this description are open star clusters. Open clusters are large groups of gravitationally bound stars (meaning they’re very close together) that formed at the same time, from the same material. Remember when we discussed stars forming out of gas? Most of these gas clouds are massive (millions of times the mass of our Sun), and thus can produce tens or even hundreds of thousands of stars. The resulting stars tend to remain gravitationally bound in an open cluster.

The open cluster M67, with all the stars observed by APOGEE boxed. (Credit: SDSS)

Open clusters have a number of useful properties. Since all of the stars formed from the same cloud, they all have approximately the same chemical makeup. They are also all approximately the same age (give or take a few million years, but that’s a cosmic eye-blink). These two properties make open clusters particularly easy to model. The models predict both intrinsic and easily observable properties of the cluster (e.g. observed brightness and color patterns), so to determine the intrinsic properties of an open cluster, we only need to find a model that matches it well. With an intrinsic brightness, we can quickly calculate the distance to an open cluster.

APOGEE has observed stars in the fields of hundreds of open clusters (e.g., M67 seen here with observed APOGEE stars marked). But simply being in the same area as an open cluster doesn’t mean the star is part of the gravitationally bound group of stars. It’s an age-old problem for astronomers: we only see a 2D map of the 3D sky. A star in the field of an open cluster could easily be hundreds of light years in front of or behind the gravitationally bound group of stars. The Open Cluster Chemical Abundances and Mapping (OCCAM) survey considers all the APOGEE stars falling in open cluster fields. Determining whether or not a star is in fact a member of the gravitationally bound group can be difficult.

The OCCAM survey relies on the fact that cluster member stars are gravitationally bound. Gravitationally bound stars move through the galaxy together and thus will have similar velocities when measured from Earth. The OCCAM survey combines line-of-sight velocity measurements (Doppler Velocity) from APOGEE with measurements of velocity perpendicular to the line of site (proper motion) from the recent Gaia Data Release 2 to isolate cluster members from non-members.

With uniform APOGEE chemical measurements from member stars in many open clusters, and distance measurements obtained from modeling the open clusters, we can finally measure a high precision Galactic abundance gradient that will be used to calibrate models of galaxy evolution. And that’s one more piece in the puzzle of how our own Milky Way formed and evolved.

SDSS-V Is Underway!

“Everything in this project makes life challenging.”

“Sure, but challenges make life interesting!”

This conversation occurred at a very special SDSS meeting in the middle of last month, and indeed no one could accuse SDSSers of ever taking it easy.  More than two years before the end of SDSS-IV, plans are well underway for its successor, SDSS-V.  Last month’s meeting was the first in-person gathering of the current major players since the Sloan Foundation awarded a $16M grant to the survey.  However, members of the team have been working hard for three years already: identifying the most exciting science goals, simulating survey strategies, and designing new hardware, among other tasks.  Dr. Juna Kollmeier, from The Carnegie Observatories, was selected as SDSS-V Director last spring, and other members of the Management Committee were chosen shortly afterwards. The core projects are now solidifying and the hardware is being prototyped. It’s an exciting (and oh so busy) time!

The science and hardware teams listen to Director Kollmeier open the meeting, in the historic library at the Carnegie Observatories in Pasadena, USA.

The team published a description of the project last fall for the astronomical community, which you can find here. In summary, SDSS-V will consist of three “Mappers,” much like how SDSS-IV now consists of eBOSS, MaNGA, and APOGEE-2.

The Milky Way Mapper will observe millions of stars in our Milky Way Galaxy and in its companion Magellanic Clouds, tabulating their motions and their compositions to study how stars form, disperse throughout space, make heavy elements, and die.  The team will also look for the signatures of planets and invisible companions (including black holes) around the stars.  The Local Volume Mapper will measure the strength of light emitted from interstellar gas in the Milky Way, the Magellanic Clouds, the Andromeda Galaxy, and other nearby galaxies.  This emission tells us about how the gas interacts with stars (especially those that are many times the mass of the Sun) as they form and die, and about how the heavy elements that these stars make are transported throughout the galaxy into later generations of stars. The Black Hole Mapper will observe many thousands of galaxy clusters and supermassive black holes in the distant Universe.  Because light from these objects left when the Universe was much younger, we can use these data to “watch” how these objects grow, change, and influence other galaxies across cosmic time.

An artist conception of the 3D Universe that SDSS-V will explore. The Earth, in the Milky Way, is at the center, and scientists peer outwards in all directions to measure the light from nearby galaxies and distant black holes. Image Credit: Robin Dienel/OCIS.

 

One of the classic symbols of SDSS is its “plates” — big disks of aluminum that hold the hand-plugged fiber optic cables up to our 2.5-meter telescopes.  These plates can be thought of as mini maps of the sky, with holes punched through them at the locations of the stars and galaxies we want to observe.  But all of that is changing in SDSS-V, in two major ways.  First, we’re building a couple of small telescopes to add to the ones that already exist, which the Local Volume Mapper will connect directly to six brand-new instruments for taking their measurements.  Second, SDSS-V is replacing its plates with many little robots (500 of ’em!) that are able to position the fiber optic cables anywhere in the focal plane of the telescope.  Unlike fibers plugged into the plates, the robots can move from target to target during an observation, allowing the survey to observe each star, quasar, or galaxy cluster only as long as needed and to be much more efficient.  We’ll miss our beautiful plates, but robots are pretty cool too, right?

All three Mappers will operate instruments in both hemispheres — on SDSS’s trusty 2.5-meter Sloan Telescope at Apache Point Observatory in New Mexico, USA, and on the 2.5-meter du Pont Telescope and the new small telescopes at Las Campanas Observatory in Chile.  (SDSS-IV has already established an important presence at Las Campanas.)  By using both sites, SDSS-V will have a spectroscopic view of the entire sky, because no single place on Earth can see everything.  Even though each Mapper has different science goals, SDSS scientists from all of the Mappers will continue to meet together regularly and share results, because we’re all interested in the same Universe!

SDSS-V can’t happen without the support of member institutions, though.  So if you are (or if you know) an astronomer who wants to be part of making it happen and have early access to the data and the global network of collaborators within SDSS, talk to your chair or director, and let us know how we can help!

SDSS in the Numbers

Scientists are inordinately fascinated by the turning over of odometers.  SDSS has recently passed three such milestones.  A list of all published refereed papers that mention “SDSS” or “Sloan Survey” in their title and abstract (link to the: custom ADS query) finds that:
-We have just passed 8000 published papers (8009 to be exact);
-We have just passed 400,000 total citations (401,609 to be exact);
-The paper that introduced SDSS to the world, York et al, has just hit 6000 citations.

A few other fun statistics:
-We have 90 papers with 500 or more citations;
-The survey’s h number is 242 (there are 242 papers with 242 or more citations);
-There are 849 papers with 100 or more citations.


This information was contributed by Prof. Michael Strauss (Princeton), Former Project Spokesperson and Deputy Project Scientist in SDSSI/II.

A Visit to Las Campanas

Following the 2017 SDSS Collaboration Meeting, a small number of the scientists in attendance travelled to La Serena, to the North of Santiago, to participate in a trip to Las Campanas, where the APOGEE-2S instrument has been installed on the Irene du Pont Telescope. We made our own way to La Serena (by plane, or overnight bus) and met at 9.30am in the La Serena Plaza del Arms to travel to Las Campanas together.

We started our journey under thick cloud, but quickly climbed out of it for spectacular views of the Chilean Andes.

Finally Las Campanas is visible in the distance (spot the speck on the mountain).

Las Campanas is just visible as a speck on a mountain to the right of centre. Credit: Karen Masters, SDSS.

We arrived at Las Campanas around lunchtime, for a quick meal, before touring both the Irene du Pont Telescope, and the Clay 6.5 Meter Telescope (one of the two Magellan Telescopes).

Both the Magellan Telescope (right) and the du Pont Telescope (left) on Las Campanas. Credit: Karen Masters, SDSS.

We were of course especially interested to see the APOGEE infrastructure, now installed in the Irene du Pont Telescope.

Plug plate storage at the du Pont Telescope. Credit: Karen Masters, SDSS.

The APOGEE-2S Instrument. Credit: Karen Masters, SDSS

Then it was back to La Serena to head out many different ways home. Scientists from as far apart as China, Mexico, the UK, Chile and the USA had joined the trip and enjoyed visiting one of the observatories used by SDSS together.

Group shot outside the du Pont Telescope.

Work for SDSS – Senior Software Developer for Apache Point Observatory

Many people contribute to the success of SDSS, not least the staff working at Apache Point Observatory, where our 2.5m Sloan Telescope is located.

The below job add for a Senior Software Developer to support engineering and observing at Apache Point Observatory is copied from a posting on the New Mexico State University website: http://jobs.nmsu.edu/postings/28105


New Mexico State University is seeking a technical and computer-oriented person for a Senior Software Developer position to support daytime engineering and night-time astronomical observing at Apache Point Observatory (APO), in Sunspot, NM. The observatory at Sunspot NM will be location of work place. Work schedule on site is generally M-F 8-4:30.

Responsibilities include; designs, implements/installs, maintains, and administers computer, network, and phone infrastructure including hardware and software. Monitors Zenoss, overall performance to proactively identify potential issues and tune appropriately. Providse 24/7 high reliability systems with security and analysis – splunk and Bro. Performs root cause analysis on failed components and implements corrective measures. Works with others to address problems, implement new instrumentation and capabilities. Internal and external customer support and good communication skills are required. Familiar with cluster and virtual systems.

Relevant experience includes hands-on system administration, computer system and network management and development and system security. Proficiency in Unix/Linux, RedHat KVM, C, Python, VxWorks, RTEMS,FreePBX, Vyatta and VyOS,Mac OS, Modeling language – UML. Technical writing, HTML5, CSS, js, frameworks and nodej applications.

Must be able to work at 9500 ft MSL, provide critical support off hours, holidays and weekends.

Benefits: Group medical, hospital, life, dental, and disability insurance. State educational retirement, workers compensation, sick and annual leave, and unemployment compensation.
See http://hr.nmsu.edu/benefits/

Paper/email documents will not be accepted. Required documents (CV/Resume, 3 references, unofficial copy of transcripts) must be attached to the NMSU electronic application system at http://jobs.nmsu.edu.

Employment is contingent on funding and eligibility for employment in U.S. and results of a background verification. Target start date is July 1, 2017.

Direct link to the posting on the NMSU website: http://jobs.nmsu.edu/postings/28105

SDSS-IV at #aas229: Friday Abstracts

Here are the SDSS related abstracts for Friday 6th January at #aas229.

Talks:

10:00 AM – 10:10 AM
306.01. The SDSS-IV Extended Baryon Oscillation Spectroscopic Survey: The Clustering of Luminous Red Galaxies Using Photometric Redshifts
Abhishek Prakash

10:50 AM – 11:00 AM
302.05. Composite Spectra of Broad Absorption Line Quasars in SDSS-III BOSS
Hanna Herbst; Fred Hamann; Isabelle Paris; Daniel M. Capellupo

Posters:

347.15. Constraining the Merging History of Massive Galaxies Since Redshift 3 Using Close Pairs. I. Major Pairs from Candels and the SDSS
Kameswara Bharadwaj Mantha et al.

347.34. Correlating The Star Formation Histories Of MaNGA Galaxies With Their Past AGN Activity
Andrea Gonzalez Ortiz

347.35. Incidence of WISE-Selected Obscured AGNs in Major Mergers and Interactions from the SDSS
Madalyn Weston; Daniel H. McIntosh; Mark Brodwin; Justin Mann; Andrew Cooper; Adam McConnell; Jennifer L. Nielson

347.38. Properties of Pseudo-bulges and Classical Bulges Identified Among SDSS Galaxies
Yifei Luo; Aldo Rodriguez; David C. Koo; Joel R. Primack; Sandra M. Faber; Yicheng Guo; Zhu Chen; Jerome J. Fang; Marc Huertas-Company

347.55. Spectral Analysis, Synthesis, & Energy Distributions of Nearby E+A Galaxies Using SDSS-IV MaNGA
Olivia A. Weaver; Miguel R. Anderson; Muhammad Wally; Olivia James; Julia Falcone; Allen Liu; Nicole Wallack; Charles Liu

347.56. A Study of E+A Galaxies Through SDSS-MaNGA Integral Field Spectroscopy
Muhammad Wally; Olivia A. Weaver; Miguel R. Anderson; Allen Liu; Julia Falcone; Nicole L. Wallack; Olivia James; Charles Liu

336.04. Results from a Pilot REU Program: Exploring the Cosmos Using Sloan Digital Sky Survey Data
Nancy J. Chanover; Kelly Holley-Bockelmann; Jon A. Holtzman

336.05. The FAST Initiative: Fostering a More Inclusive SDSS Collaboration
Kelly Holley-Bockelmann; Nancy J. Chanover; Adam J. Burgasser; Kelle L. Cruz; Charles Liu; Paul A. Mason; Jesus Pando; Emily L. Rice; Sarah J. Schmidt; Jose R. Sanchez-Gallego; Sara Lucatello; Alfonso Aragon-Salamanca; Francesco Belfiore; Brian Cherinka; Diane Feuillet; Amy Jones; Karen Masters; Audrey Simmons; Ashley Ross; Keivan G. Stassun; Jamie Tayar

343.01. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Overview and Membership Methods
John Donor; Peter M. Frinchaboy; Julia O’Connell; Katia M. Cunha; Benjamin A. Thompson; Matthew Melendez; Matthew D. Shetrone; Steven R. Majewski; Gail Zasowski; Carlos Allende-Prieto; Marc H. Pinsonneault; Alexandre Roman-Lopes; Mathias Schultheis ; Keivan G. Stassun

343.02. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Gradients using SDSS-IV/DR13 and Gaia
Peter M. Frinchaboy; John Donor; Julia O’Connell; Katia M. Cunha; Benjamin A. Thompson; Matthew Melendez; Matthew D. Shetrone; Steven R. Majewski; Gail Zasowski; Carlos Allende-Prieto; Ricardo Carrera; Ana García Pérez; Michael R. Hayden; Fred R. Hearty; Jon A. Holtzman; Jennifer Johnson; Szabolcs Meszaros; David L. Nidever; Marc H. Pinsonneault; Alexandre Roman-Lopes; Ricardo P. Schiavon; Mathias Schultheis ; Verne V. Smith; Jennifer Sobeck; Keivan G. Stassun

343.03. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Optical Extension for Neutron Capture Elements
Matthew Melendez; Julia O’Connell; Peter M. Frinchaboy; John Donor; Katia M. Cunha; Matthew D. Shetrone; Steven R. Majewski; Gail Zasowski; Marc H. Pinsonneault; Alexandre Roman-Lopes; Keivan G. Stassun

344.18. Searching for Long-Period Companions and False Positives within the APOGEE Catalog of Companion Candidates
Duy Nguyen; Nicholas W. Troup; Steven R. Majewski

344.19. The APOGEE DR13 Catalog of Stellar and Substellar Companion Candidates
Nicholas W. Troup

344.20. APOGEE/Kepler Overlap Yields Orbital Solutions for a Variety of Eclipsing Binaries
Joni Marie C. Cunningham; Diana Windemuth; Aleezah Ali; Meredith L. Rawls; Jason Jackiewicz

SDSS THIRTEENTH DATA RELEASE

This post is now in four languages: English, Chinese, Spanish and Portuguese! It is originally written by Anne-Marie Weijmans in English and translated by Zheng Zheng (to Chinese) ,  Andres Meza (to Spanish) and Ricardo Ogando (to Portuguese). 

This weekend, the Sloan Digital Sky Survey (SDSS) is celebrating its thirteenth public data release, or lucky DR13!

Data releases are an important part of the SDSS. All the data that are observed by the Sloan Telescope for the various surveys that are part of SDSS, get reduced and processed, and eventually are made publicly available. This means that everyone with access to the internet can download the data, use it for their research or teaching, or simply look at all the images and spectra that are available. You just have to go to the SDSS website, and you can start exploring the data for yourself!

So, what does DR13 have in store for you? Apart from including all the data that was released in previous data releases, there is also lots of new data:

  • DR13 is the first data release for the MaNGA survey! MaNGA stands for Mapping Nearby Galaxies at Apache Point Observatory, and it studies galaxies with integral-field spectroscopy. This allows us to study chemical elements and motions of stars and gas not just in the centre of the galaxies, but all over the galaxy outskirts too. MaNGA is releasing its spectra in datacubes for 1351 individual galaxies, making it the biggest integral-field galaxy survey available on-line so far!
  • APOGEE, or the APO Galaxy Evolution Experiment is taking infra-red spectra for hundreds of thousands of stars in the Milky Way. For this data release, they have improved the analysis of all their previously released spectra, and measured the abundances of various chemical elements of stars. This will help us understand how the Milky Way formed over time.
  • eBOSS, short for extended Baryon Oscillation Spectroscopic Survey, is mapping the structure of the Universe, by taking spectra of more than a million galaxies and quasars. Its goal is to measure the expansion rate of the Universe, and the nature of the mysterious Dark Energy that accelerates this expansion. eBOSS is releasing improved analysis of previously released spectra, as well as several catalogs with information on emission line galaxies and variable quasars.

Do you want to have a look at all of this data? Here are some places to get started:

  • The SDSS SkyServer has several tools to explore the data. You can for instance:
    • find stars and galaxies in the Navigate tool
    • look at images and spectra of stars and galaxies with the QuickLook tool
    • search for a particular sample of galaxies or stars with SQL
  • If you are interested in analyzing the data yourself, then you can find more information on how to download the data on the SDSS data access page
  • If you are a teacher and interested in activities that will help your students explore the Universe, then have a look at our SDSS education web page, with lots of resources for the class room.

Anne-Marie Weijmans
SDSS Data Release Coordinator
University of St Andrews

 

 

本周末(7月31日)斯隆数字化巡天(SDSS)迎来了它的第十三次数据释放(DR13)!

数据释放是SDSS的重要事件。所有由斯隆望远镜观测的SDSS各种巡天计划的数据,都会经过处理并对公众开放。这就意味着所有人都可以从网上找到和下载这些数据,并用来做研究、教学、或者仅仅是查看已有的图像和光谱。你只需点击进入SDSS的网站就可以查看这些数据啦!

那么,DR13里面到底都有什么呢?除了包含之前的数据释放中所有的数据以外,它还包含了很多新的数据:

  • DR13是MaNGA巡天的第一次数据释放!MaNGA是对近邻星系进行的积分场光谱巡天。有了MaNGA数据,我们还可以研究整个星系的 — 而不仅仅是星系中心的 — 元素丰度以及恒星和气体的运动。 MaNGA将释放1351个星系的IFU光谱,这也是现今在网上公开的最大的积分场星系巡天数据样本。
  • APOGEE是拍摄几十万颗银河系内恒星的红外光谱的巡天项目。在这次的数据释放中,我们改进了以前的数据处理方式,并且测量了恒星的各种元素丰度。这将会帮助我们理解银河系的形成过程
  • eBOSS巡天用拍摄一百多万个星系和类星体的光谱的方式来描绘宇宙的结构。它的目的是测量宇宙膨胀的速度以及探寻造成宇宙加速膨胀的神秘的暗能量的本质。eBOSS不光会释放经过改进处理的以前释放过的光谱,还会释放几个包含发射线星系和变源类星体信息的星表。

你是不是已经想要看一看这些数据啦?下面列出的这些网址可以帮助你开始探索:

  • 如果你希望自己来分析数据,那么你可以在SDSS数据使用页面找到如何下载数据的相关信息
  • 如果你是一名教师并且希望利用一些活动帮助学生探索宇宙,那么你可以查看SDSS教育网站,这里面有很多相关资源可以帮助课堂教学。

 

 

Este fin de semana, Sloan Digital Sky Survey (SDSS) está celebrando su décimo tercera liberación de datos públicos o ¡afortunado DR13!

La liberación de datos es una parte importante de SDSS. Todos los datos que son observados por el Telescopio Sloan para los distintos estudios que forman parte de SDSS, son reducidos y procesados, y eventualmente puestos a disposición del público. Esto significa que cualquier persona con acceso a Internet puede bajar los datos, usarlos para su investigación, para enseñar o simplemente para ver las imágenes y los espectros que están disponibles. Sólo tienes que ir al sitio web de SDSS y ¡ya puedes comenzar a explorar los datos por ti mismo!

¿Qué tiene DR13 para ti? Además de incluir todos los datos que ya han sido hechos públicos anteriormente, también hay una gran cantidad de nuevos datos:

  • ¡DR13 es la primera liberación de datos para MaNGA! MaNGA es el acrónimo en inglés para Mapeo de Galaxias Cercanas desde el Observatorio de Apache Point, y estudia galaxias con espectroscopia de campo integral. Esto nos permite estudiar los elementos químicos y el movimiento del gas y la estrellas no solo en el centro de las galaxias, sino que también en sus partes externas. MaNGA está liberando sus espectros en cubos de datos para 1351 galaxias individuales, ¡convirtiéndolo en el estudio de campo integral más grande disponible en línea!
  • APOGEE, o experimento de Evolución Galáctica en el APO de sus siglas en inglés, está tomando espectros infrarrojos para cientos de miles de estrellas en la Vía Láctea. Para esta liberación de datos, se ha mejorado el análisis de todos los espectros publicados previamente y medido la abundancia de varios elementos químicos de las estrellas. Esto nos ayudará a entender cómo se ha formado la Vía Láctea en el tiempo.
  • eBOSS, acrónimo en inglés para Muestra Espectroscópica Extendida de la Oscilación Bariónica, está haciendo un mapa de la estructura del Universo, tomando espectros de más de un millón de galaxias y quásares. Su objetivo es medir la tasa de expansión del universo y la naturaleza de la misteriosa Energía Oscura que acelera su expansión. eBOSS está liberando análisis mejorados de sus espectros anteriores, así como también varios catálogos con información para las galaxias con líneas de emisión y quásares variables.

¿Quieres darle un vistazo a todos estos datos? Aquí hay algunos lugares para comenzar:

  • El SDSS SkyServer tiene varias herramientas para explorar los datos. Tu puedes por ejemplo:
    • Encontrar estrellas y galaxias con la herramienta Navigate.
    • Ver las imágenes y espectros de estrellas y galaxias con la herramienta QuickLook
    • Buscar un grupo particular de estrellas y galaxias con SQL.
  • Si eres un profesor y estás interesado en actividades que puedan ayudar a tus estudiantes a explorar el Universo, puedes mirar nuestra página de educación del SDSS donde hay muchos recursos para realizar en las clases.

 

 

 

Esse final de semana, o Sloan Digital Sky Survey (SDSS) celebra seu décimo terceiro lançamento de dados ao público, ou um sortudo DR13!

Os Lançamentos de Dados são uma parte importante do SDSS. Todos os dados que são observados pelo telescópio Sloan, para os vários levantamentos que são parte do SDSS, são reduzidos e processados, e em algum momento são disponibilizados para o público. Isso significa que qualquer pessoa com acesso à internet pode baixar esses dados, usar para sua pesquisa ou ensino, ou simplesmente olhar as imagens e espectros disponíveis. Basta ir à página do SDSS e começar a explorar!

Bom, mas o que é que o DR13 tem? Além dos dados de todos os lançamentos anteriores, um montão de novidades foram incluídas:

  • DR13 é o primeiro a conter dados do levantamento MaNGA! MaNGA significa Mapeamento de Galáxias Próximas no Observatório de Apache Point (em inglês, Mapping Nearby Galaxies at Apache Point Observatory), e estuda galáxias usando espectroscopia de campo integral. Isso nos permite estudar os elementos químicos e o movimento das estrelas e do gás não apenas no centro de galáxias, mas também em sua periferia. MaNGA está liberando seus espectros em cubos de dados para 1.351 galáxias, fazendo dele o maior levantamento disponível online de galáxias observadas com campo integral até hoje.
  • APOGEE, ou o Experimento de Evolução da Galáxia no APO (em inglês, APO Galaxy Evolution Experiment) está observando espectros no infravermelho para centenas de milhares de estrelas na Via-Láctea. Nesse lançamento de dados eles melhoraram a análise de todos os espectros liberados anteriormente, medindo a abundância de vários elementos químicos nas estrelas. Isso vai nos ajudar a entender como a Via-Láctea se formou e evoluiu ao longo do tempo.
  • eBOSS, abreviação de extended Baryon Oscillation Spectroscopic Survey, está mapeando a estrutura do Universo, observando espectros de mais de um milhão de galáxias e quasares. Seu objetivo é medir a taxa de expansão do Universo, e a natureza da misteriosa Energia Escura que acelera essa expansão. eBOSS está disponibilizando análises melhoradas de espectros liberados anteriormente, além de vários catálogos com informação sobre galáxias com linhas de emissão e variabilidade de quasares.

Você quer dar uma olhada em todo esse conjunto de dados? Por onde começar:

  • O SkyServer do SDSS tem várias ferramentas para explorar os dados. Você pode, por exemplo:
    • encontrar estrelas e galáxias usando o Navigate
    • olhar imagens e espectros com o QuickLook
    • procurar por uma amostra de galáxias ou estrelas em particular usando SQL
  • Se você está interessado em analisar os dados você mesmo, você pode encontrar mais informações de como baixar os dados na página SDSS data access
  • Se você for um professor e está interessado em atividades que possam ajudar seus estudantes a explorar o Universo, dê uma olhada em nossa página educativa, com vários recursos para a sala de aula.

 

 

It takes a large team of people to put together a data release: from collecting the data at the telescopes, to processing the data, analyzing the data, and documenting the data. The SDSS DR13 website, that describes all the various datasets now available in DR13, was mostly written at DocuFeest, by a dedicated group of SDSS scientists. Image credit: Jennifer Johnson.  数据释放要经过很多环节:从望远镜收集数据、处理数据、分析数据、以及准备相关文档,这是我们大团队共同努力的结晶。SDSS DR13网站描述了DR13中包含的所有数据,这个网站大部分都是由一批SDSS科学家在DocuFeest上完成的。照片由Jennifer Johnson提供 Se debe reunir un grupo grande de personas para generar los datos públicos: desde recolectar los datos en los telescopios, luego procesar y analizar los datos, hasta finalmente documentarlos. El sitio para el DR13, que describe todos los conjuntos de datos ahora disponibles, fue escrito en su mayor parte en el DocuFeest por un grupo dedicado de científicos de SDSS.  Concluir um lançamento de dados requer um grande time de pessoas: da coleta de dados nos telescópios, ao seu processamento, análise, e documentação. A página do DR13 do SDSS, que descreve todos os distintos conjuntos de dados agora disponíveis no DR13, foi quase toda escrita por um dedicado grupo de cientistas do SDSS numa reunião batizada de DocuFeest (Feest é festa em holandês, origem de uma das organizadoras do evento de documentação). Crédito da imagem: Jennifer Johnson.

 

Caption: all the SDSS data are stored at the servers of the Center for High Performance Computing (CHPC[https://chpc.utah.edu/]), at the University of Utah. This particular server holds all the SDSS data releases, including DR13. The total data volume is about 267 TeraBytes (TB = 1000 Gigabyte = 1012 bytes): that is more than 58,000 DVDs worth of data! Image credit: Adam Bolton.

All the SDSS data are stored at the servers of the Center for High Performance Computing (CHPC), at the University of Utah. This particular server holds all the SDSS data releases, including DR13. The total data volume is about 267 TeraBytes (TB = 1000 Gigabyte = 1012 bytes): that is more than 58,000 DVDs worth of data! Image credit: Adam Bolton.  所有的SDSS数据都存储在美国犹他大学高性能计算中心(CHPC)的服务器上。这台服务器存储着所有SDSS释放过的数据,包括DR13。整个数据容量大约是267T (1T=1000G=1012 bytes):这比58000张DVD包含的数据都要多!照片由Adam Bolton提供 Todos los datos de SDSS están almacenados en los servidores del Centro de Computación de Alto Rendimiento de la Universidad de Utah. Este servidor contiene todos los datos públicos, incluyendo DR13. El volumen total de datos es de alrededor de 267 TB, ¡esto es más de 58.000 DVDs!  Todos os dados estão armazenados em servidores no Center for High Performance Computing (CHPC), na University of Utah. Esses servidores em particular contem todos os lançamentos de dados do SDSS, incluindo o DR13. O volume total de dados é de cerca de 267 Terabytes (TB = 1000 Gigabyte = 1012 bytes): isso é mais que 58.000 DVDs cheios de dados! Crédito da imagem: Adam Bolton.

 

montage_1st_gal_plate

The very first 17 galaxies observed by MaNGA, one plate full! These galaxies are all included in DR13. Some galaxies have been off-set from the centre of the IFU to allow inclusion of foreground stars, to test our measurement precisions (this was only done for this first commissioning plate). Image credit: Kevin Bundy.  这17个星系来自MaNGA的首次观测,是在同一个光纤插板上的所有星系!这些星系都包含在DR13里面。有些星系偏离了IFU的中心,这是因为我们要同时拍摄一些前景恒星用来检测测量精度 (不过这种情况只发生在这第一个光纤插板上)。照片由Kevin Bundy提供 ¡Las primeras 17 galaxias observadas por MaNGA en una sola placa! Todas estas galaxias están incluidas en el DR13. Algunas galaxias han sido desalineadas del centro del IFU para incluir estrellas en el fondo, las cuales permiten probar la precisión de las mediciones (esto fue hecho sólo para esta primera placa).  As 17 primeiríssimas galáxias observadas pelo MaNGA, são um verdadeiro gol de placa! Essas galáxias foram todas incluídas no DR13. Algumas galáxias foram deslocadas do centro do IFU para incluir estrelas, a fim de testar a precisão de nossas medidas (isso foi feito apenas para essa placa inaugural de comissionamento do instrumento). Crédito da imagem: Kevin Bundy.

An artist view of the universe 艺术家眼里的宇宙

Recently, a Chinese artist, Jian Yang, organized his personal exhibition in Beijing, China. The exhibition is called “the beginning of infinity” and one of his art pieces showed in this exhibition has a component made of an SDSS plate.

最近中国的一位艺术家杨健在北京进行了一次个人艺术展。这次展出的名字叫 “无穷的开始”,而其中的一件艺术品是利用了SDSS的一块光纤插板做成的。

The room holding the exhibition was designed as a maze. The art piece with the SDSS plate was placed at the center of a maze. It is named “The Universe” and the idea came from an old fairy tale: The earth is a big whale and the sky is a huge elephant. If you could find a leg of the elephant and climb up along the leg, then you could grab the stars. In the artist’s view, the SDSS telescope is trying to capture and analyze the starlight. So he combined science and the fairy tale by putting the SDSS plate at the bottom of the flying elephant’s leg, which means the plate could help us climb up and reach the stars.

展览的场地被别出心裁的设计成了迷宫的模式。而这件包含SDSS光纤插板的艺术品就被放置在迷宫的正中央。作品的灵感来源于艺术家小时候听到的神话故事:说大地是一只鲸鱼,宇宙是一只巨大的大象,如果你能找到大象的腿,往上爬就能抓到星星。对于艺术家来说,SDSS项目就是在做捕获分析星光的工作。杨健把SDSS光纤插板当作一只升腾起来的大象的脚底板,通过这种形象的建构来联合中国与国际,神话和科学。

 

The room holding the exhibition was designed as a maze.

The room holding the exhibition was designed as a maze. 整个展览场地被设计成一个迷宫的形式。

 

The art piece with an SDSS plate (plate# 3939).

The art piece with an SDSS plate (plate# 3939). The plate (编号3939) is placed at the bottom of an elephant’s leg. 用SDSS光纤插板做成的艺术品. SDSS的板子被当做大象的脚底板。

 

The art piece viewed from the bottom.

The art piece viewed from the bottom. 从下面看这件艺术品。

What is MaNGA (in one sentence)?

MaNGAlogo5small

 

Some months ago, members of the MaNGA (Mapping Nearby Galaxies at Apache point observatory) survey (part of SDSS-IV) were asked to suggest ideas for a suitable taglines/catchphrase which would describe the survey in one sentence. This idea was that this would go on promotional materials SDSS-IV would take to the American Astronomical Society Meeting, and also the main SDSS website.

The working favourite to that point had been “the galaxy survey for people who love galaxies”, but we wanted something which described the scientific goals of the survey more precisely.

In the word of MaNGA PI, Kevin Bundy this request resulted in an “outpouring of creative, collective genius” (a phrase which Kevin suggested might itself be the appropriate one to describe the MaNGA team).

Here are some of the ideas the team came up with, catagorised by Kevin:

Ideas which reference The 3rd Dimension

  1. .. Now in 3D!
  2. Sloan goes 3D
  3. Sloan Galaxies in three dimensions
  4. Galaxies in 3D
  5. A new dimension in galaxy surveys
10 000 (nearby) galaxies mapped in 3D
  6. A multi-dimensional view of galaxies
  7. Galaxies in 3D by the thousands
  8. Thousands of local galaxies in 3D
  9. Ten thousand Galaxies. Three dimensions

Inspirational ideas

  1. To boldly go where no other Galaxy survey has gone before.
  2. Unravelling the galaxy avatar
  3. Ten thousand mysteries unfold

Direct (or descriptive) ideas:

  1. Census of local galaxies
  2. MaNGA: Deciphering galaxies pixel-by-pixel
  3. Observing the dynamical structures and composition of galaxies to unravel their evolutionary histories
  4. Galaxy birth, assembly, growth and ‘death’
  5. Galaxies Beyond the Central Fiber
  6. Spatially resolved spectroscopy of 10,000 nearby galaxies

Ideas Inspired by Biological Analogies

  1. Galaxy dissection
  2. Galaxies under the microscope
  3. Exploring the life cycle of galaxies
  4. Anatomising galaxies dead and alive
  5. Dissecting galaxies in their dark matter haloes

Humorous suggestions

  1. Galaxies do the full monty
  2. Everything you wanted to know about galaxies, and in 3D
  3. Experience galaxies in 3D, without the glasses

Clever/cultural references

  1. Taking spectra of the spectrum of galaxies
  2. Galaxies in 3D! It’s over 9000!!
  3. 10K3D
  4. How galaxies tick

The final decision was made to go with “Mapping the inner workings of thousands of nearby galaxies” for our website, and we have a banner which says “The 3D Lives of Galaxies”, although we also really like the creative idea of making an API to return all of these randomly.

MaNGA - Mapping the inner workings of thousands of nearby galaxies

 

Many thanks to: Jeff Newman, Bob Nichol, Kyle Westfall, Surhud More, Karen Masters, Aaron Dutton, Claire Lackner, Mike Merrifield, Daniel Thomas, Eric Emsellem, Carles Badenes, Anne-Marie Weijmans, Brian Cherinka, Demitri Muna, Brett Andrews, Christy Tremonti and Kevin Bundy for contributing ideas.

 

How SDSS Uses Light to Study the Most Abundant Element in the Universe

When we spread out the light from a source into a rainbow, we can reveal information about its chemical makeup. This is how we understand the spectral signatures that reveal that stars have different temperatures. But to learn about the objects that we study in space, whether they be stars, interstellar gas, or galaxies, we first have to know something about the chemical properties of the elements that make up these objects. And one of these elements is, by far, the most important to study: Hydrogen.

Why is hydrogen the most important element to study in astronomy? Primarily because it is the most abundant. If you count the number of hydrogen atoms in all of space (stars, gas, and galaxies), it can be shown that nine out of ten atoms in space are hydrogen. The second-most abundant is helium, which makes up almost one out of ten atoms in space, and every other element is present in only trace amounts — which is not to say that they are unimportant! But in this post, we are going to focus on the big one.

 

The Hydrogen atom, consisting of a single proton as the nucleus orbited by a single electron.

The Hydrogen atom, consisting of a single proton as the nucleus orbited by a single electron.

Hydrogen is also the simplest element on the Periodic Table, as the above diagram shows — one lone proton being orbited by one electron. And like all elements, hydrogen is able to absorb and emit light of certain wavelengths. If the electron is hanging out in the ground state (the n=1 state), it can absorb photons that will shimmy it to the n=2, n=3, n=4, etc. state (and there are an infinite number of these states). Likewise, if the electron begins in the n=2 state, then the atom can absorb photons of light to push it into the n=3, n=4, n=5, etc. state.

When a hydrogen atom is in one of these “excited” states (i.e., n 1), it also has the opportunity to emit a photon and travel back down to a lower energy level. The photons absorbed have the same wavelengths as the photons emitted, so that they always appear in the same place in a spectrum. In the following illustration, the first four energy levels of the hydrogen atom are shown. Three commonly-studied transitions between different energy levels are named, along with their absorption/emission wavelengths in units of Ångströms (= 10-10 m). The colors of the line are the approximate colors that they might appear to your eye — with the exception of the Lyman-α transition, which emits in the ultraviolet and is therefore invisible to the human eye.

An illustration of the four lowest energy levels of the Hydrogen atom, and commonly studied transitions between these energy levels.

An illustration of the four lowest energy levels of the Hydrogen atom, and commonly studied transitions between these energy levels.

 

When studying spectra from space, it is common to study either absorption spectra (spectra with lines that show that atoms are absorbing photons) or emission spectra (spectra with lines that show that atoms are emitting photons). The absorption process is the most common when studying stellar spectra. And for many stars, it is the hydrogen lines that gives us a first indication about the physical properties of the stars. Here, for instance, is the spectrum of an A-type star, i.e., one with strong Hydrogen absorption features:

Spectrum of an A0 star exhibits strong Hydrogen absorption lines where indicated. Other, smaller absorption lines are due to calcium, magnesium, and sodium absorption. This spectrum is taken from the Science Archive Server -- check it out!

Spectrum of an A0 star exhibits strong Hydrogen absorption lines where indicated. Other, smaller absorption lines are due to calcium, magnesium, and sodium absorption. This spectrum is taken from the Science Archive Server — check it out!

Galaxies, which are large conglomerations of stars, can also show hydrogen absorption features. But many galaxies, like spiral galaxies or else irregular galaxies with ongoing star formation, actually produce strong emission features. This is because the hydrogen gas that exists between the stars in these galaxies is heated by the stars, so that individual atoms are excited to higher energy levels. A great example is the spectrum of the irregular galaxy NGC 6052, shown below:

Spectrum of the irregular galaxy NGC 6052, with hydrogen emission lines labeled.

Spectrum of the irregular galaxy NGC 6052, with hydrogen emission lines labeled.

 

You might have noticed in this galaxy spectrum that these hydrogen emission lines appear to sit on top of what look like hydrogen absorption features. The absorption features, as mentioned above, come from the stars in the galaxy, whereas the emission features come from the gas between the stars.

There is other cool stuff that hydrogen can teach us. One of the coolest is called the Lyman-α Forest, which can be used to tell us how much hydrogen gas exists on large scales between galaxies.


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 about how SDSS uses light in our mission to study the Universe. 

David Schlegel Wins an Ernest Lawrence Award

Prof. David Schlegel of Lawrence Berkeley National Laboratory, the PI of the BOSS part of SDSS-III and a long time contributor to all areas of the Sloan Digital Sky Surveys was announced yesterday as one of the winners of the E.O. Lawrence Award.

David Schelegel, PI of BOSS, shows off a plug plate. Image credit: LBL

David Schelegel, PI of BOSS, shows off a plug plate. Image credit: LBL

The Ernest Orlando Lawrence Award was established in 1959 in honor of Ernest Lawrence, who invented the cyclotron (for which he won 1939 Nobel Laureate in physics). The Lawrence Award honors U.S. scientists and engineers, at mid-career, for exceptional contributions in research and development supporting the Department of Energy and its mission to advance the national, economic and energy security of the United States.

The citation for David’s award (for the High Energy Physics Category of the award) reads:

Honored for his exceptional leadership of major projects making the largest two-dimensional and three-dimensional maps of the universe, which have been used to map the expansion rate of the Universe to 10 billion light years and beyond. His fundamental technical contributions to high precision measurements of the expansion history of the Universe, and his massive galaxy redshift surveys to detect baryon acoustic oscillations, has helped ascertain the nature of Dark Energy, test General Relativity, and positively impact fundamental understanding of matter and energy in the universe.  These efforts have made precision cosmology one of the most important new tools of high-energy physics.

All of us at SDSS are delighted to wish David Schlegel many congratulations for this honor.

Heroes of the Helpdesk

They come in a steady stream: the requests for lost passwords, for aid in correcting a CasJobs query, for insight into the technical details of SDSS photometry, astrometry, and spectroscopy, for help with educational resources and SkyServer, and for general astronomical and database knowledge, all sent to helpdesk@sdss.org. Two or three times a day, they appear in the mailboxes of those on the helpdesk mailing list, representing the hopes and dreams of an astronomer, amateur, student, or professional, to use SDSS data to answer the big questions of the Universe (or at least to get more room on the server).

The helpdesk in action: Ben Weaver making SDSS science possible for yet another scientist.

The helpdesk in action: Ben Weaver making SDSS science possible for
yet another scientist.

The task falls to the volunteers, headed up and organized by Ben Weaver, Archive Scientist at New York University (right). Most questions are handled quickly by Ben, Ani Thakar, Archive Scientist at Johns Hopkins University, or Jordan Raddick, one of our Education Directors, also at Johns Hopkins. Promptness is easiest if the questioners have done us the kindness of including relevant information such as the context or URL they are using and the exact query. Occasionally questions about how parameters were derived or why there are changes between Data Releases requires the advice of other SDSS experts. In this case, Ben sends email to the relevant SDSS mailing list. Excellent answers are gratefully accepted from the wider collaboration, who really do know these data. Our thanks to everyone who has stepped up and contributed to making SDSS data scientifically valuable to an astonishing array of people. Above all, we wish to thank the helpdesk regulars. If you have sent an email to the helpdesk or if you know someone who has sent an email to the helpdesk (and you probably do, trust me), send a cheer their way.