A Statement of Solidarity

The message below was distributed to the SDSS Collaboration on June 2, 2020, as a PDF and also as images on social media.  The message is reproduced here for posterity and for “live” links. Some corrections to the original letter have been made, primarily correcting typographical errors or grammatical mistakes, but also in modifications to linked content after reflection on nuances in their statements. Making mistakes is part of the process of learning and of striving to be better; correcting them isn’t an act of weakness, but rather a statement of a lesson learned.

Dear SDSS Collaboration,

Among the many charges to COINS (the Committee on Inclusiveness in SDSS) is to evaluate the collaboration’s general climate, with respect to having a healthy atmosphere for encouraging young scientists to participate and lead scientifically and to inform the Collaboration on our findings and other resources on inclusivity.

Right now there are events across the world to protest violence and murder by the state. What follows below addresses directly specific issues within the United States, but we acknowledge that colonialism, racism, white supremacy, and other forms of oppression are occurring in many countries, including those of our colleagues in SDSS. We oppose the oppression of human beings in all forms and against all persons globally. We acknowledge that we have not always taken as strong and a stance as we should have in past global events, and we commit to doing better. Below we will ask for your help in doing so.

In accordance with these beliefs, we affirm the following statement:

Black lives matter.

For our Black friends and colleagues, we see your grief, your pain, and your anger. We mourn with you over those lives senselessly cut short: George Floyd, Ahumaud Arbery, Breonna Taylor, and so many others who have been killed before, many without hashtags and video footage.  We recognize the profound anguish and additional trauma that members of the Black community carry as a result of systematic racism and violence.  You are invaluable to this community, and we stand in solidarity with yours. We further denounce all acts of racism and white supremacy and commit ourselves to take every necessary action to eliminate them in our communities and the wider world.

As a first step, we invite everyone to review the Best Practices Document, with regards to the five elements of the SDSS workplace culture: respect, kindness, trust, diversity, and inclusion.

The SDSS Code of Conduct clearly outlines a policy that SDSS welcomes and respects its members regardless of race, ethnic origin, religious beliefs, gender, gender identity, sexual orientation, disability, age, family and socio-economic status, or cultural background. If you experience violations of the code of conduct or experience behavior that makes you feel uncomfortable, please reach out directly to the Ombuds, whose responsibility it is to serve and help you in these situations.

If you are finding it difficult to focus at this time or in prior moments of unrest, you are and were not alone. Moreover, it is natural to feel helpless during these larger events, but these larger events are not unrelated to the everyday actions we implement in our lives. Your choices are significant, and there are many things that you can do to have an impact. The list we provide below is by no means exhaustive, but hopefully provides a meaningful starting point for how to take action, generally.

  • Listen. There are many voices expressing what they see, experience, and feel, not just in this current moment, but in their daily lives. Listen, believe, and validate the voices of your colleagues, both within and beyond SDSS.
  • Express your support. Often the most strongly impacted during these times will feel isolated. Expressing your support is one of the strongest reinforcements of the inclusive community we have committed ourselves toward creating. Ask your colleagues and mentees what they need. Actively create space for those affected to express themselves safely.For those with institutional power, we call on you to be flexible and compassionate with regards to research and deadlines, so that those who need it have space and time to process.
  • Communicate. SDSS members intersect with many other circles and collaborations. We can encourage others to act. Please feel free to use the information and resources in this message as needed.
  • Advocate for your own institutions to adopt Codes of Conduct and Best Practices that encourage supportive and constructive environments.
    Commit specifically to making your communities equal opportunity.
    Feel free to use the SDSS documents as starting points.
  • Stand up. The most pervasive acts of racism occur in everyday interactions and many take the form of uncountable microaggressions. Standing up in these situations is meaningful, as is challenging unconscious bias and following the guidelines of sensitivity training. The COINS Bystander Training provides guidance for how to stand up. Our documents are not yet ready, so we refer you to the following global initiative to enable bystander action.
  • Educate. Learning and sharing knowledge about the broader context of these specific events is a necessary responsibility. The literature on this topic is broad and expansive and even on COINS, we too are still learning both in our home countries and globally. The list below highlights a number of spaces that take racism seriously and provide starting points.
    We invite the collaboration to help us make this list more exhaustive and more global at the following:
    COINS Repository of Reading Material (editable Overleaf document)We also alert your attention to the following Astronomy- or STEM-specific discussions of race and gender:

  • Donate. To facilitate, we have started a list of charitable organizations that aim to eliminate racism, are acting to support those directly affected by the current crisis, and raise Black voices. We invite the collaboration to contribute to our repository to alleviate barriers for those wishing to act: COINS Repository of Charitable Organizations (editable Overleaf document)
    Note: The previous items provide a means of donating your time, energy, and voice to these issues. If you are not financially able to contribute, giving in these ways is just as valuable.

Recent events are also reacting to the COVID19 pandemic that, globally, has disproportionately affected under-represented communities and the socio-economically disadvantaged. The following list provides actions that we can all take both in our scientific lives and in our communities that contribute towards real and long-lasting change.

Please contact COINS (coins@sdss.org) should you have additional suggestions of ways to stand in solidarity or resources to share with the rest of the collaboration.  These are ongoing conversations, and we welcome your voice at the table.

In addition, please feel free to share this letter with other collaborations, academic departments, and beyond. We recognize that these words are a commitment to action towards equity and justice, and we must all do the work together.

Black lives matter, now and always.

Sincerely yours,

Committee on Inclusiveness in SDSS
Karen Masters, SDSS-IV Spokesperson
Gail Zasowski, SDSS-V Spokesperson

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!

SDSS Fifteenth Data Release

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. 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.

Caption: A colourful collage of stars observed with the MaStar observing program. MaStar is also on twitter: @MaStar_library. Image credit: MaStar Team.

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!

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


This is a guest post by William N. Brandt (Penn State).

One of the many university outreach programs with SDSS-IV connections is the Penn State Science Workshops for Educators. This longstanding program at Penn State, with more than 20 years of successful history, provides week-long summer workshops for 10-20 high-school and middle-school teachers, aiming to help them teach their students better about astronomy and astrophysics. Each of these teachers will teach hundreds of students in the coming years.

The first 2018 summer workshop (July 9-13) focused on “Black Holes: Gravity’s Fatal Attraction”, a topic where the SDSS has made fundamental contributions. The lead instructors were Prof. William N. Brandt (Penn State), Dr. Chris Palma (Penn State), and Mr. Glenn Goldsborough (Pennsbury High School). The workshop program included lectures on the subject material; discussions about pedagogical approaches; hands-on activities (inexpensive classroom labs, PC-based software activities, WWW-based labs); examinations of curricular materials; and guest presentations by professional astronomers. The workshop introduced teachers to the predicted properties of black holes and the astronomical evidence for their existence. Along the way, they studied modern ideas about the nature of space, time, and gravity. Topics covered included the predicted properties of black holes, stars and their fates, stellar-mass black holes in our cosmic backyard, supermassive black holes in galactic nuclei, active galaxies and jets, Hawking radiation, and singularities.

Among the guest lecturers, Dr. Kate Grier (Penn State) gave a talk on the exciting results from the SDSS Reverberation Mapping Project, which has now measured direct black hole masses over half of cosmic history (see attached image). Observations for this project are ongoing as part of SDSS-IV, and this work was recently featured in an SDSS-IV Press Release. Dr. Vivek Mariappan (Penn State) furthermore presented a guest lecture on the variability of quasar winds as probed by SDSS and how these winds can provide feedback into quasar host galaxies. Observations of such wind variability continue presently as part of the SDSS-IV Time Domain Spectroscopic Survey. The attending teachers had a chance to inspect SDSS plug plates and learn about how these are used to conduct the massive SDSS spectroscopic surveys (see image below).


These workshops were partly funded by the “Broader Impacts” component of an NSF  grant supporting studies of quasar winds with the SDSS.

Further information about the workshops is available at http://sites.psu.edu/psiwa/

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-IV in South Korea

Last week the SDSS-IV collaboration has been having its annual all survey collaboration meeting in Seoul, South Korea. Hosted by SDSS-IV member Graziano Rossi of Sejong University, over 120 collaboration scientists from all over the world enjoyed 3 days of formal science meeting, with two days of working meetings after.

Photo of seoul plaza. The view many attendees enjoyed of the Seoul Plaza. Credit: Racheal Beaton

Conference group photo. Credit: Sejong Univ.

Photo of Korea. Many members stayed to enjoy some sightseeing before or after the meeting. Credit: Jennifer Johnson

The next collaboration meeting will be held next June in Ensenada, Baja California, Mexico hosted by scientists from UNAM Ensenada.

Text written by Karen Masters (Haverford/Portsmouth).

Documentation Fun: DocuVana 2018

We had DocuFeest in 2016, DocuCeilidh in 2017, and now it was time for DocuVana 2018. Last month, a group of enthusiastic SDSS IV-midables traveled to the University of Washington in Seattle, to prepare the SDSS webpages for its next big public data release. Data Release 15 (DR15) is planned for December 2018, and will contain new MaNGA data. It is also the first public data release for the MaNGA Stellar Library, MaStar, so lots of new documentation was needed! And it was not just the new data that created a lot of work: the APOGEE-2 team took this opportunity to go through their existing webpages, and update and improve where needed. And they already made a head start for the many new stellar spectra that they will release in 2019 in DR16.

SDSS IV-midables hard at work at DocuVana (credit: J. Sobeck)

Lots of writing was done, lost of new pages created, but in between all that typing and editing, the documentation team also took some time to explore Seattle. They enjoyed some amazing food, visited the Museum of Modern Pop Culture, and got a tour from engineer Curtis Bartosz through the UW machine shop, where all the SDSS plates are made.

The food is always good at our documentation feasts! (credit: J. Sobeck)

Inspecting plates in the University of Washington workshop (credit: J. Sobeck)

So, why did all these people take part in DocuVana? Because they care about documentation: they want to make sure that their data is not just available for downloading, but that people also can use their data: for science projects, teaching projects, or just to have a look at for fun. And to be able to do that, the data needs clear and easily accessible descriptions, examples, and tutorials.

Stay tuned for December, when you will be able to see their hard work as DR 15 goes live!


Anne-Marie Weijmans

SDSS Data Release Coordinator

University of St Andrews


PS: a very big thank you to the DocuVana organiser Jennifer Sobeck and José Sanchez-Gallego, at the University of Washington. And also many thanks to all the participants at DocuVana without whose hard work we would not have a website for DR15: Amy Jones, Ben Murphy, Bonnie Souter, Brian Cherinka, David Stark, David Law, Dan Lazarz, Gail Zasowski, Joel Brownstein, Jordan Raddick, Julie Imig, Karen Masters, Kyle Westfall, Maria Argudo-Fernández, Michael Talbot, Rachael Beaton, Renbin Yan and Sten Hasselquist (as well as Becky Smethurst, Rita Tojeiro, Ben Weaver and Ani Thaker via video link)

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!

APOGEE and Amateur Spectroscopy

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.

The attendants of the Sacramento Mountains Spectroscopy Workshop. David and Drew are on the far right.

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

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.

Job Openings: Observe for SDSS

We currently have two openings being advertised for observing staff to work within SDSS at the Apache Point Observatory, New Mexico.

To get a sense of a night of observing at Apache Point Observatory check out our Youtube video:

Please visit the links below to see the details of how to apply to be an SDSS observer.

Support Astronomer:  https://jobregister.aas.org/ad/970e54bd

Telescope Operations Specialist:  https://jobregister.aas.org/ad/bb55b431

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.

2017 Collaboration Meeting in Santiago, Chile

The scientists who are part of the Sloan Digital Sky Surveys gather once a year for a collaboration meeting. One of the themes of this meeting is looking for synergy and collaboration across the different surveys, and institutions which are part of SDSS.

For 2017 the meeting happened July 24-26th 2017 on the beautiful Campus San Joaquin of Pontifica Universidad de Catolica in Santiago, Chile, hosted by the Chilean Participation Group of SDSS (a collaboration of seven different Chilean Universities).

SDSS Collaboration Members attending SDSS2017. Around 120 scientists from all over the collaboration attended the meeting. The plates shown are APOGEE-2S plates brought down specially from Las Campanas.

Job Opening at The Sunspot Astronomy Visitor Center

The Sunspot Astronomy Visitor Center includes content related to the science and observations of the Sloan Digital Sky Surveys. They are seeking a new Program Co-ordinator for Education and Public Outreach. The below is reposted


New Mexico State University is seeking a program coordinator to manage the education and public outreach program at the Sunspot Astronomy Visitor’s Center.

Duties include: Oversees operations of public access to exhibits and daily tours around Sunspot Observatories. Initiates and provides local tours, plans and operates star parties: Coordinates visits from local schools and interested groups; Ensures visitor center facility is staffed during operational periods for visitors and tours as needed;  Develops a  business plan to ensure visitor center solvency; Manages gift shop including stock ordering, pricing and design and/or selection of gift shop merchandise; Manages exhibits including coordination of repairs and updates as needed; Responsible for fiscal management of Visitor’s Center;  and may require grant writing and cooperative agreements with other local tourist attractions and of state and federal agencies.  Manage staff as required.

A bachelor’s degree and/or a strong background in and knowledge of astronomy is preferred.

Job Closing Date: 08/31/2017

Targeted Start Date: 10/01/2017

Please visit to https://jobs.nmsu.edu/hr to apply