The APOGEE survey had stupendously productive October and November bright runs[*] with 206 plates successfully observed. This achievement is a great credit to the Apache Point Observatory mountain observing and engineering staff, who worked hard to complete these observations while simultaneously performing system maintenance and validation. Thanks to their efforts 107 plates were observed during the October bright run and 99 during the November bright run. This total of 206 observations included multiple observations of 120 unique plates covering 87 different fields on the sky, for a total of 54,000 new spectra of over 23,000 stars, including 11,000 previously unobserved stars.

The APOGEE survey is currently on pace to finish its goal of observing 100,000 stars by the end of the SDSS-III survey in 2014.Those interested in the future of APOGEE and the Sloan Foundation 2.5-m Telescope after SDSS-III are invited to read about the plans for a trio of surveys that will study our own galaxy and beyond

http://www.sdss3.org/future

[*] A “bright run” is the time the moon is bright in the sky, roughly from one week before full moon through one week after new moon. The moon makes the background sky much brighter in visual wavelengths (note how many more stars you can see with your eyes when the moon is below the horizon compared to the night of a full moon). But the additional brightness of the moon is much less important in the infrared, so infrared observations are generally scheduled for times the moon is up, while visual-wavelength observations, such as those of the BOSS survey, are scheduled for times when the moon is below the horizon or only partially illuminated from our perspective on Earth.

SDSS-III astronomers announce today the first detection of BAO in the Lyman-alpha forest 11 billion years ago. The paper has been submitted to Astronomy & Astrophysics and is available on arXiv:

“Baryon Acoustic Oscillations in the Ly-α forest of BOSS quasars”
N. Busca et al.
Submitted to Astronomy & Astrophysics
http://arxiv.org/abs/1211.2616

The new BOSS Lyman-alpha measurement of H(z)/(1+z) is illustrated by the red dot.

The Lyman-alpha forest is detected through the imprint of hydrogen cloud absorpt
ion lines on the light from background quasars.

For more details see today’s press release at

http://www.sdss3.org/press/lyabao.php

The SDSS-III BOSS Galaxy Clustering Working Group has collected its primary DR9 science results and ancillary data and made them available to the public on the SDSS-III public web site. The goal is to provide sufficient information for the wider astronomical community to recreate and perhaps even improve these analyses. At http://www.sdss3.org/science/boss_publications.php, one can find the following data products:

* Tabulated correlation function measurements and power spectrum measurements, both pre- and post-reconstruction, used in the detection of the BAO feature in Anderson et al. Covariance matrices for all measurements are included as well.
* Tabulated correlation function measurements and errors from the analysis of the full shape of the CMASS clustering signal from Sanchez et al.
* Tabulated measurements and covariance matrices for the redshift-space multipoles of the CMASS correlation function, from Reid et al and Samushia et al. A software package to compute the theoretical correlation functions is also linked to from the public SDSS-III SVN.
* CosmoMC modules that allow users to incorporate the BAO detection and the theoretical analyses of the redshift-space multipoles into CosmoMC Markov chains.
* Tabulated results from the enhanced redshift distortions analysis of Tojeiro et al.
* Small-scale correlation functions, both redshift-space and projected, and errors from Nuza et al.

At this web page, we also include high-quality figures from these papers that we encourage people to include in presentations that incorporate BOSS results. Questions about the files should be directed at the corresponding author of the paper from which the measurements came.

1) Anderson et al:
“The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 9 Spectroscopic Galaxy Sample”
http://arxiv.org/abs/1203.6594

2) Reid et al:
“The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measurements of the growth of structure and expansion rate at z=0.57 from anisotropic clustering”
http://arxiv.org/abs/1203.6641

3) Sanchez et al:
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the large-scale two-point correlation function
http://arxiv.org/abs/1203.6616

4) Nuza et al:
“The clustering of galaxies at z~0.5 in the SDSS-III Data Release 9 BOSS-CMASS sample: a test for the LCDM cosmology”
http://arxiv.org/abs/1202.6057

5) Manera et al:
“The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: a large sample of mock galaxy catalogues”
http://arxiv.org/abs/1203.6609

6) Samushia et al:
“The Clustering of Galaxies in the SDSS-III DR9 Baryon Oscillation Spectroscopic Survey: Testing Deviations from Lambda and General Relativity using anisotropic clustering of galaxies”
http://arxiv.org/abs/1206.5309

7) Tojeiro et al:
“The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: measuring structure growth using passive galaxies”
http://arxiv.org/abs/1203.6565

A new SDSS press release is up! This time, we’re featuring work led by Nurten Filiz Ak of Penn State, studying disappearing broad absorption line troughs in quasars. They have found several quasars in which the BAL trough disappears over a nine-year period. The simplest explanation for this observation is that as the quasar’s accretion disk has rotated, carrying the absorption region out of the line of sight between us and the quasar. In other words, as the press release says, the gas cloud is…

Gone, with the Wind

One of the most fun parts of the Sloan Digital Sky Survey has been Galaxy Zoo, which connects our survey with citizen scientists all over the world. And now, the fun is still going!

The original Galaxy Zoo launched in July 2007, to immediate success beyond our wildest expectations. Within a few days, thousands of people had signed up to classify images of nearly one million SDSS galaxies as spiral or elliptical. The project released its data in 2009; by that time, hundreds of thousands of citizen scientists had worked together to classify each of the galaxies more than 70 times over. Since then, professional astronomers have used that dataset to publish more than 20 peer-reviewed papers in scientific journals, with more to come.

Last week, a new version of Galaxy Zoo launched. The new site features images from the SDSS’s Data Release 9, including images of thousands of galaxies south of the plane of the Milky Way that are being shown to citizen scientists for the first time. The new site also includes images from the Hubble Space Telescope’s CANDELS survey, allowing us to compare galaxies as seen by SDSS to similar galaxies from the distant past.

The new Galaxy Zoo is open for business, and needs your help! Go to the new site and click “Classify Galaxies” to get started. Have fun, and the sky’s the limit!

The Sloan Digital Sky Survey III (SDSS-III) has released the largest-ever three-dimensional map of massive galaxies and distant black holes, which will help astronomers explain the mysterious dark matter and dark energy that makes up 96 percent of the universe.

Data Release 9 is the latest in a series of data releases stretching back to 2001. This release includes new data from the ongoing SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), which will eventually measure the positions of 1.5 million massive galaxies over the past six billion years of cosmic time, as well as 160,000 quasars — giant black holes actively feeding on stars and gas — from as long ago as 12 billion years in the past.

DR9 is available at: http://www.sdss3.org/dr9.

READ THE PRESS RELEASE HERE

WATCH A FLY-THROUGH BY CLICKING BELOW:

The 2012 SDSS-III Collaboration meeting was held June 26-29 at the Observatório Nacional in Rio de Janeiro, Brazil. Thanks to the hard work of the local organizers a great and productive time was had by all.

The meeting caught the interest of a local major newspaper, “O Globo”, which published a nice summary of the SDSS-III project at:

http://oglobo.globo.com/ciencia/astronomia-de-olhos-bem-abertos-5329246

Today’s post is a personal story of an exciting discovery from SDSS-III, written by SDSS astronomer David Nidever of the University of Virginia.

I just wanted to share the exciting news that APOGEE confirmed a known exoplanet! Now that we’ve shown that APOGEE can measure radial velocities precisely enough to find a known planet, this opens up a whole new range of scientific questions to study.

APOGEE’s spectrometers can now measure changes in a star’s radial velocity of less than 50 meters per second (about 110 miles per hour) – we could see a change in a star’s velocity corresponding to the speed of a sports car, from halfway across the galaxy. And not even a particularly fast sports car! Because we can measure stellar velocities so precisely, we can see the back-and-forth motions of the stars exerted by objects orbiting those stars, such as smaller companion stars or even planets.

And now we’ve seen one: the planet we rediscovered is called HD 114762b. Looking through the first batch of fields that had been observed at least 8 times, APOGEE detected clear signals of radial velocity shifts of 500 m/s from the star HD 114762, a fairly ordinary-looking main sequence star just a little hotter than the Sun^***.

In 1989, Harvard astronomer David Latham discovered an unseen companion around HD 114762. He thought it might be a planet, but he didn’t have quite enough evidence to be totally sure. He wrote up his results in a Nature paper. Ten years later, our colleague Geoff Marcy (UC Berkeley) found fairly convincing evidence that HD 114762b is in fact an exoplanet, which he described in a paper in the Astrophysical Journal. It’s possible that it’s a brown dwarf, but an exoplanet is the more likely explanation.

Let me tell you the story of how we found it again.

The APOGEE^*** project has been running since last summer, measuring spectra of stars in the Milky Way disk. In many cases, we’ve been getting spectra for the same stars over and over again.

For the past few months, I’ve been looking at approximately 1,300 stars – each of which has 8 or more APOGEE observations^*** – that I had flagged as potential binaries due to large variations in their radial velocities. I used data from those observations as input into a computer program that fits the orbits of the binary stars^*** – for each binary star system, the code creates a plot that tells me the most likely orbital path of each star. Of course, if one of the two “stars” in the system turns out to be a brown dwarf or a planet, the code will tell me the orbit of the brown dwarf or planet, as well as its mass.

After I generated the orbit plots, I looked through them all by eye, one by one, to find the ones whose orbits were most certain. We found several hundred good orbital fits; of those several hundred orbits, 45 looked like they could belong to brown dwarfs or planets.

We had the opportunity to observe some of these candidates with the Hobby-Eberly Telescope (HET). With a mirror nine meters (30 feet) in diameter, the HET is much bigger than the SDSS’s 2.5 meter telescope, so we can use it to collect better data – hopefully good enough to confirm whether one or more of these objects is actually a brown dwarf or planet. But observing time on large telescopes is hard to come by, and we only had enough time to get spectra for 10. So which ten would we choose?

Last Thursday night, I was talking with Scott Fleming, Rohit Deshpande, Suvrath Mahadevan, Matthew Shetrone, and Fred Hearty. (I should also mention here that Suvrath and Matthew gave us some of their observing time to look at these spectra – thanks!!) We were coming up with our final list of ten stars when Suvrath suggested that we check whether any of the stars on our list had been spotted as binary stars in previous surveys. Scott checked online, and that’s when we discovered that star #2 on our list was HD 114762! The graph below shows the data we collected from HD 114762. The line going up and down in the top of the graph represents the back-and-forth motion of the star – a clear sign of an orbiting planet!

What we know about the exoplanet HD 114762b is collected in its entry in the Visual Exoplanet Catalogue. HD 114762b’s orbit is known – the orbital parameters are available in its entry at exoplanets.org.

This isn’t an Earth-shattering (galaxy-shattering?) new discovery – after all, we already knew that HD 114762b is most likely an exoplanet, and Geoff Marcy’s team has measured its orbit quite precisely. But we’re very excited about APOGEE’s discovery, because it points to many more exciting things in the future. We knew APOGEE’s radial velocity measurements would be good, but not necessarily good enough to find exoplanets. This new discovery opens up a whole new regime of scientific exploration. Watch this space for many more exciting things to come!

P.S. We didn’t plan it this way, but it turns out that today’s post relates well to today’s today’s xkcd webcomic!

Footnote 1. The “HD” means it was first seen as part of the “Henry Draper Catalog” in the early 1900s. Back to main post

Footnote 2. “APOGEE” stands for “Apache Point Observatory Galactic Evolution Experiment.” Back to main post

Footnote 3. We identified that these stars were binaries due to their highly variable radial velocities, initially using the regular pipeline RVs, then my own RVs using the star’s combined spectrum as the RV template, which reduced the RV errors by a factor of two to three.) Back to main post

Footnote 4. The code was written by Geoff Marcy and his team. I used to work for him as an undergrad at San Francisco State University, and he kindly gave us permission to use the code for APOGEE. Back to main post

Steven Bamford has taken the publically available SDSS image data and a fun shape-identification project from Galaxy Zoo to provide a web page to write with the galaxies in the cosmos:

http://mygalaxies.co.uk/

After writing your word or phrase, click through to see the actual detailed data
on each galaxy as gathered by SDSS.

This is currently limited to the letters, numerals, and common punctuation marks in standard English writing. Internationalizations could follow if someone wanted to classify character shapes in other alphabets.

APOGEE On-Air:
For an introduction to APOGEE, take an hour to listen to this interview on WMRA radio’s Virginia Insight featuring APOGEE PI Steve Majewski, Gail Zasowski, and John Wilson.

http://wmra.org/post/discovering-stars-whole-new-way

APOGEE + Kepler Collaboration Highlighted in New Scientist:
The New Scientist reports in its April 2012 issue (subscription required) on searches for stars formed along with our Sun. The article highlights the SDSS-III APOGEE experiment and the new collaboration between SDSS-III and the Kepler asteroseismology team to jointly study stars in the Milky Way. The New Scientist article explains that while APOGEE

is not looking explicitly for the sun’s siblings, “it’s very possible that these stars will be in the sample”, says Steven Majewski of the University of Virginia in Charlottesville. One advantage of APOGEE is that 10 per cent of the stars it surveys are shared by NASA’s Kepler spacecraft, whose observations of flickering starlight will tell us the ages of these stars. This is crucial, says Majewski, because any solar sibling must be the same age as the sun, as well as share its chemical composition and motion.
(New Scientist, 2012 April 7, pp 40-41, “The sun’s sibilings” by Ken Croswell)

Kepler is a space satellite observing 100,000 stars in our Milky Way galaxy to look for planets around Sun-like stars. Its photometric observations are so precise that it can detect the pulsations of distant stars as they resonate with sound waves, much like the many frequencies of vibration in a ringing bell. The science of studying these pulsations is called asteroseismology.

Image: APOGEE’s targets include star clusters like M67 that have an elemental composition very similar to that of the Sun. This image illustrates the APOGEE spectrum (the blue line in the lower part of the image) of just one of the hundreds of stars APOGEE can observe at one time. By studying M67 and other clusters APOGEE will provide insights into the conditions in which our Sun was born.
Image Credit: Peter Frichaboy (TCU), Robert Lupton (Princeton), and the SDSS collaboration.

The Kepler observations reveal the many frequencies of oscillation of individual stars, data that can be used to determine very precisely the radii and masses of these stars. In principle, the stellar radii and masses can be used to determine very precisely the evolutionary state — and, therefore, the age — of each star, but there remains some uncertainty if the chemical composition of the star is unknown. Thus the APOGEE team and Kepler seismologists are now collaborating on a program to use APOGEE spectroscopy to uncover the chemical compositions of a sample of about 10,000 Kepler asteroseismology targets and to create the largest sample of Milky Way field stars with known ages. In addition to providing a set of very well studied stars for understanding the evolution of the Milky Way, the combined data set will improve the calibration of science done with all of the stars in each project.

A core team of SDSS-III members is meeting this week at NYU to write the documentation for SDSS-III Data Release 9, scheduled for July 2012. This release willpresent the first spectra from the BOSS survey of galaxies and quasars.

One of the key aspects of each data release has been providing as much information as we can about every aspect of the data. Astronomers around the world continue to do new and inventive things with SDSS-III data, and the project strives to do its best to document the properties and caveats of the data to support such great new science.

Team members try to balance tedium and fun. Delegation appears to be an effective strategy. Here we rely on Jeremy Tinker (left), in charge of target tiling, and Ben Weaver (right), in charge of managing all of the bits of SDSS-III data, to do some of the heavy lifting. While the group currently meeting is leading much of the effort, the documentation for each data release represents the culmination of the work of many, many engineers and scientists across the entire collaboration.
(Image Credit: Michael Wood-Vasey)

The Apache Point Observatory operations team reached a new record, observing 103 BOSS plates in March of 2012.

BOSS observes 1000 spectra at a time, organized by “plug plates” whose holes precisely align fiber optic cables that route light from the telescope focal plane to the spectrographs. Each plate has 1000 fibers, 10% of which are dedicated to the sky calibration, so ~90,000 spectra of astronomical objects were taken during this time.

This is the most number of spectra that any astronomical survey has ever observed in a month. In fact, no survey on any telescope other than the Sloan 2.5-m and the Anglo-Australian Telescope have ever even published more spectra than this one-month haul from SDSS-III.

Typically BOSS observes 50-60 plates per month. This March had unusually good weather enabling faster observations, even as the Spring nights are getting shorter and shorter. The entire Apache Point Observatory (APO) staff worked hard and with the utmost efficiency to keep up, resulting in a record breaking 103 plates this month in only 16 nights of active BOSS observing (the other nights went to APOGEE or were lost to bad weather), including the first ever “perfect night” of 9 plates from start to finish (we don’t have a 10th cart to mount another plate).

Congratulations to the entire APO staff!

Image Caption: In March, BOSS observed 103,000 spectra, each of which was routed through a fiber-optic cable that was plugged by hand. The industrious APO plugging crew is pictured here showing the deleterious effects of having placed more than 2,000 fibers/finger in a month. But don’t worry, click through to see that they’ve recovered and are happy to face a new month of plugging. (Image Credit: Dan Long, APO).

The Sloan Digital Sky Survey (SDSS-III) today announced the most accurate measurements yet of the distances to galaxies in the faraway universe, giving an unprecedented look at the time when the universe first began to expand at an ever-increasing rate. The results, announced today in six related papers posted to the arXiv preprint server, are the culmination of more than two years of work by the team of scientists and engineers behind the Baryon Oscillation Spectroscopic Survey (BOSS), one of the SDSS-III’s four component surveys.

The record of baryon acoustic oscillations (white rings) in galaxy maps helps astronomers retrace the history of the expanding universe. Figure Credit: E.M. Huff, the SDSS-III team, and the South Pole Telescope team.
Graphic by Zosia Rostomian.

BOSS scientists announced these results today at the National Astronomy Meeting (NAM) in the UK and will present them at the American Physical Society (APS) meeting in the US on Sunday. These new results provide the best measurements yet that directly compare the distance to galaxies 6 billion years ago and the cosmic microwave background from 13.7 billion years ago. This measurement is thus a key part of determining the nature of dark energy that is currently accelerating the expansion of the Universe. The BOSS results focus on the era when dark energy first emerged as a significant player in the Universe. By understanding how it began to dominate the Universe’s expansion, SDSS-III scientists hope to be able to reveal more about this mysterious substance that makes up 70% of the mass-energy of the Universe.

For more information and reference to the papers, see the SDSS-III press release at

http://www.sdss3.org/press/20120330.bspec.php

One of the most important things scientists need to know when using a spectrograph is precisely how light from different objects and different wavelengths travels through the instrument, and how the instrument changes and moves over the course of a survey. A new device developed at Penn State University adapts techniques from the fiber-optic telecommunications industry to demonstrate a very accurate and precise calibration of the SDSS-III APOGEE spectrograph.

The image shows the three APOGEE camera arrays illuminated with the output from the Fabry-Perot calibration device. The 200nm wavelength range of APOGEE is divided up into three different cameras. The light from each fiber is spread out across a row in this image. When APOGEE is observing the night sky, each row would be the light from a star. If you zoom in on the image you can see the large number of individual peaks that SDSS-III scientists can use to map out all of the details of the APOGEE instrument. (While the APOGEE instrument detects infrared light, we have represented the light in visual wavelengths so that you can see it.)

APOGEE currently uses thorium-argon and uranium-neon lamps for wavelength calibration. These lamps heat up small quantities of their respect elements; the elements in turn emit this energy at specific wavelengths characteristic of those elements. However, the number of lines available is fixed to the properties of the actual elements. Thorium-Argon lamps are commonly used in optical spectroscopy, but don’t have nearly enough bright lines in the near-infrared part of the spectrum to provide a good calibration. Uranium has plenty of lines in the near infrared, but they tend to blend together unless one uses a very high resolution spectrograph. Luckily, the telecommunications industry has developed efficient fibers and light sources in the near-infrared that can be adapted to some of these needs. The near-infrared sensitivity of the APOGEE instrument overlaps some of the standard telecom bands, making it possible to adapt and modify existing technology for use as calibration devices.

A team of scientists and engineers from several SDSS-III institutions recently tested out such a prototype test an entirely new way of calibrating APOGEE. The team brought together experts from several SDSS-III institutions, comprising Suvrath Mahadevan, Sam Halverson (Penn State), Fred Hearty, John Wilson (UVa), Jon Holtzman (NMSU), and Dimitry Bizyaev (APO). Using a Fabry-Perot interferometric cavity, the team was able to generate a precisely-controlled light source that had a stable fixed pattern of peaks. During a three-day run in February this calibration device was tested on the actual APOGEE instrument with great success. The new device, build entirely with commercially available components, consists of a single-mode fiber Fabry-Perot cavity illuminated with a supercontinuum source, and kept very stable with a thermoelectric temperature controller. The output of the cavity results in 400 emission peaks in the APOGEE wavelength regime. This light is fed to APOGEE’s 300 fibers and then passes through the volume-phase holographic grating that disperses the light to separate out different wavelengths onto different places on the camera. In the end, 400 emission peaks times 300 fibers results in 120,000 clearly-defined peaks in the APOGEE focal plane!. These peaks help astronomers to map out many of the important properties of the instrument: the line-spread function, scattered light, persistence effects, point-spread function, as well as providing a grid of stable markers across the focal plane to enable detailed tracking of any overall instrument drift.

The new calibration device is relatively insensitive to vibration and atmospheric pressure changes, and the single mode fiber mitigates issues of collimation and alignment that often affect larger Fabry Perot devices. Ongoing analysis of the dataset acquired over the three-day test is expected to help calibrate many aspects of the APOGEE instrument, including the mosaic Volume Phase Holographic grating at the heart of the APOGEE spectrograph.

A joint analysis of data from the Atacama Cosmology Telescope and the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) has yielded the first robust detection of the kinetic Sunyaev-Zel’dovich effect, first predicted forty years ago. This effect is due to the motions of galaxy clusters with respect to the cosmic microwave background, and its imprint will unveil new information about dark energy, dark matter, and the formation of the galaxy clusters—the largest bound structures in the Universe.

For more, see the joint press releases from the ACT and SDSS-III collaborations:

http://www.princeton.edu/main/news/archive/S33/21/69O40/
http://www.sdss3.org/press/20120319.ksz.php

The paper was posted to the arXiv preprint server today as

“Detection of Galaxy Cluster Motions with the Kinematic Sunyaev-Zel’dovich Effect”
http://arxiv.org/abs/1203.4219