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Large and Long Programs (LLPs)

August 14th, 2014

Large and Long Programs (LLPs) enable high-impact science programs and Gemini, allowing observations that require significantly more time than a partner typically approves for a single program or long-term status. LLPs may extend from two to six semesters, and they are expected to promote collaborations from across the parnership’s communities.

The first LLPs began observations in the 2014B semester:


A second group of LLPs began observations in the 2015B semester:



GN-2014B-LP-1 COL-OSSOS: COLours for the Outer Solar System Object Survey
Principal Investigator: W. Fraser (NRC Herzberg Astronomy and Astrophysics)

The surfaces of trans-Neptunian objects (TNOs) have for a long time been poorly understood. Other than the large objects which exhibit signatures of various ices, astronomers have been able to discern very little about the compositional makeup of most TNOs. In recent years, some concrete knowledge about the distribution of surface colours of small TNOs has come to light. It is now generally accepted that small TNOs fall into at least three classes of object based on their surface colours and albedo. TNO surface type is also highly correlated with dynamical class, with certain types of TNO only being found in certain regions of the outer Solar System. For example, the so-called cold classical objects are both uniquely red and dynamically cold, while more dynamically excited objects such as the Plutinos - of which Pluto is a member - exhibit a bimodal distribution of surface colours from almost entirely neutral reflectors to some of the reddest objects in the Solar System. This colour-dynamical correlation presents the intriguing idea that the surfaces of TNOs contain information on more than composition, but as well hold the key to understanding the dynamical processes that lead to the giant planets violently dispersing the protoplanetesimal disk and populating the Kuiper Belt region. It is around this idea that the COL-OSSOS survey is designed. Using nearly 400 hours GMOS and NIRI observations on Gemini-North, over the next 4 years this program will observe optical and NIR Colours of all targets in the Outer Solar System Origins Survey (OSSOS) brighter than r’=23.5. The focus of the survey is completeness and consistency, with the same SNR=25 being reached in all bands, for all targets brighter than our depth limit.

This survey will, for the first time, provide a combined compositional-dynamical test to answer key questions about the Outer Solar System’s cosmogony. For example, was Neptune’s motion from its primordial formation location to its current locale violent and ‘jumpy’, or smooth? By mapping the fraction of objects with cold-classical like surface colours throughout the Trans-Neptunian region, we will be able to determine how much of the belt was populated by dynamical scattering, a signature of violent motion, versus sweep-up, a signature of smooth motion as Neptune passed through and dispersed the protoplanetesimal disk. As another example, we will be able to determine if the primordial disk was compositionally homogenous, or heterogeneously structured with many ice lines throughout its extent. The surfaces of TNOs must reflect that structure; a heterogeneous disk will result in a clumpy colour distribution with many unique types, while a homogeneous disk will result in a smooth distribution of colours with only a few distinct types. The legacy of COL-OSSOS is a large TNO dynamical and colour database of roughly 140 TNOs with fully understood observational biases from discovery to compositional characterization.

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GN-2014B-LP-2 Rapid Spectroscopy of Elusive Transients and Young Supernovae
Principal Investigator: M. Kasliwal (Carnegie)

The intermediate Palomar Transient Factory (iPTF) is systematically exploring the optical transient sky. We focus on short timescales to optimize the survey discovery rate of very young supernovae and rare ephemeral transients. Building on the PTF legacy, our new iPTF software pipeline is geared towards automated alerts for follow-up within hours of discovery. Rapid response spectroscopy of iPTF transients will unveil (i) progenitors of supernovae: shock cooling, companion, circumstellar material properties, (ii) origin of recently discovered but poorly understood new classes of gap transients, and (iii) redshifts of relativistic afterglows discovered in seventy square degree searches or even independent of a high energy trigger. These unique physical insights into the nature of the explosion cannot be gained from late-time observations. Hence, we will undertake a dedicated iPTF-Gemini program for rapid spectroscopy. The rapid Gemini data will be complemented with panchromatic observations: radio with JVLA and CARMA, UV/X-ray with the Swift satellite and long-term optical/near-IR studies with Palomar/Magellan/Keck.

Figure 1. Gemini Observatory’s queue observing mode and quick response to Target Of Opportunity (ToO) triggers facilitates the early observation of young supernova.

Figure 2. The iPTF team.

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GN-2014B-LP-3 / GS-2014B-LP-4 Where Accretion Meets Feedback: A Galaxy Redshift Survey in HST/COS Quasar Fields
Principal Investigator: J. Werk (University of California, Santa Cruz)

We will perform a new GMOS galaxy redshift survey at z = 0.1 - 0.7 in the fields of 18 QSOs that have been observed with Hubble's Cosmic Origins Spectrograph. With thousands of new galaxy redshifts (a 50x gain over present surveys) we will fill the existing map of circumgalactic medium (CGM) gas out to 3Rvir to address the extent of metal transport and recycling, and the mechanisms of galaxy quenching in halos and large-scale environments, and the 2D structure of the CGM. This program will provide a uniquely rich dataset with a substantial legacy value.

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Figure 3.

GS-2014B-LP-1 The GOGREEN Survey of dense galaxy environments at 1<z<1.5
Principal Investigator: M. Balogh (University of Waterloo)

Clusters of galaxies are among the most massive structures in the Universe, with up to 1000 trillion times the mass of the Sun in stars, gas and dark matter. Such clusters play a central role in studies of cosmology, galaxy and structure formation, as well as plasma physics and supermassive black hole growth, and for the determination of the nature of dark matter. Their enormous gravitational potentials allow them to act as cosmic "calorimeters", maintaining an observable record of all the energy inputs and outputs associated with galaxy formation over the history of the Universe. They host the most massive galaxies, which are among the first luminous objects to form. Clusters are also the ideal places to study rare and extraordinary perturbations to galaxy evolution, such as hydrodynamic stripping of gas, tidal stripping of matter, and high-speed gravitational encounters. Much of what we have learned about galaxy evolution is thanks to years of research on these systems.

The Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) Survey will take advantage of upgraded detectors, which will make Gemini's GMOS spectrographs the best in the world for studying distant galaxy clusters. The survey will obtain multi-object spectroscopy of 21 clusters in the redshift range 1<z<1.5, representing the Universe when it was a third of its present age. The targets are selected to span a wide range of masses, representing the range of building blocks from which today's clusters were built. The sample of over 1000 spectroscopically confirmed members will reach unprecedented stellar masses at this redshift, providing the first look at environmental effects on galaxy evolution at a time when galaxies were growing in a fundamentally different way from today. With up to 15 hours of total integration time on the faintest galaxies, the spectra will allow us to measure the dynamics of different galaxy populations, their stellar populations, and to obtain a robust measurement of the abundance of low-mass, quiescent galaxies. By combining GOGREEN with our existing data on the lower-redshift descendants of these clusters, we will measure the evolution of satellite galaxy dynamics and stellar populations over the last 9.3Gyr of cosmic time. This will provide new leverage to theoretical models, importantly testing them at an epoch where there are currently almost no constraints.

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Figure 4. Distribution of targets on the sky.

GS-2014B-LP-2 Probing the dark halo of the Milky Way with GeMS/GSAOI
Principal Investigator: Tobias Fritz (University of Virginia)

The Local Group, the regime in which detailed star-by-star studies can be done, is becoming a testbed for the study of the processes of galaxy formation in general. This is because the constituents of the Local Group span a wide range of parameters such as star formation efficiency, dark matter halo size, and environment. These parameters can be turned into tests of the pressing questions governing both cold dark matter theory and galaxy formation studies, such as the distribution of matter on small scales, and even the impact of reionization. A better estimate of the total Milky Way halo mass is important for many of these questions. Due to the mass anisotropy degeneracy it is not well determined from radial velocities. Current constraints on the shape of the halo are surprising: it is oblate, but misaligned by 90 degrees with the Disk. Proper motions are required in addition to the (generally known) radial velocities to test such halo models. Turning to the baryonic sector, while accretion evidently plays a role in galaxy formation, as attested to by the existence of tidal debris streams, it is not yet excluded that some halo components formed in situ. To disentangle this process in detail, orbits are necessary.

In this program we use GeMS/GSAOI to obtain proper motions, which are missing phase space components, for a variety of tracers in the Milky Way halo, in order to constrain its shape and total mass, as well as the orbital histories of the tracers. We will employ background galaxies as a reference frame to obtain absolute motions. This pioneering study will also produce an astrometric calibration suitable for other uses of GeMS/GSAOI. Using 143 h distributed over three years we will obtain proper motions for a set of dwarf galaxies, globular clusters, and M-giants in the Sagittarius stream, distributed between 20 and 100 kpc in the halo of our Galaxy (see Figure 4 for the target distribution over the sky).

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GS-2014B-LP-3 Followup of newly discovered Near-Earth objects from the NEOWISE survey
Principal Investigator: J. Masiero (JPL)

Our program's goal is to acquire followup observations of asteroids and comets that pass close to the Earth, which have been newly discovered by the NEOWISE survey. NEOWISE is an Earth-orbiting infrared survey telescope that is constantly scanning the sky 90 degrees from the Sun. Measurements in infrared light allow us not only to find new small bodies of the Solar system, but also constrain their diameters, an important physical parameter for understanding the potential danger they pose to Earth. With ground-based followup at visible wavelengths we can also determine how reflective asteroids are, giving us an idea of their composition, and study the gas and dust properties of comets.

NEOWISE can only observe newly discovered objects for about one day, which is enough to identify asteroids and comets but not constrain their orbits. Followup data are critical to ensuring the orbits of these objects are accurately measured, and thus they can be tracked until their next pass by the Earth. The Gemini South telescope allows our team to ensure that the faintest new discoveries in the Southern Hemisphere are not lost, and that their physical properties are well understood.

Figure 5. The NEOWISE team as seen in the infrared (L-to-R: Carrie Nugent, Rachel Stevenson, Tommy Grav, Joe Masiero, John Dailey, Amy Mainzer, James Bauer, Sarah Sonnett).

Figure 6. Sequence of four Gemini images of near-Earth asteroid 2014 EN45 (circled). This object was discovered by the NEOWISE survey on 6 March 2014 and imaged by GMOS-S on 13 March 2014, which provided critical astrometry needed to confirm the asteroid's orbit. 2014 EN45 is ~800 meters in diameter and is as dark as a piece of coal.

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GS-2014B-LP-5 Spectroscopic Confirmation and AO imaging Follow-Up of Dark Energy Survey Strong Lensing Systems and Spectra for Photometric Redshift Calibration
Principal Investigator: E. Buckley-Geer  (Fermi National Accelerator Laboratory)

Over five observing seasons, which started in August 2013, the Dark Energy Survey (DES) will carry out a wide field survey of 5000 deg2 over the Southern Galactic Cap in the 5 filters grizY and a 30 deg2 supernova survey spread over 10 fields. Among the millions of astronomical objects that will be imaged by DES are rare instances of "strong lensing" systems, where the effects of general relativity, Einstein's theory of gravity, are demonstrated in a visually striking fashion. When a foreground "lens" object is by chance very closely aligned, along the line of sight, on the sky with a much more distant background "source" object, the light from the source may be significantly deflected as it passes by the lens, due to the gravitational field produced by the lensing object's mass. When the distant source is fuzzy single distant background galaxy the this strong lensing effect leads to big distortions in it's appearance: it may be transformed into a long bright arc, maybe into multiple blue knots or, in the rarest cases, into a so-called Einstein ring. On the other hand if the source is a quasar (a quasar is a compact region in the center of a massive galaxy, that surrounds its central supermassive black hole) then it will be transformed into multiple stellar-like objects.

Figure 7. Examples of lensing objects.

Figure 8. Team photo.

This wide variety in appearance of strongly lensed images is a consequence of the complexities of the lensing mass, which can range from an individual galaxy to a rich cluster of many galaxies, together with the much more massive dark matter halos in which the (luminous) galaxies reside. Studies of strong lensing systems can thus reveal to us properties of the distribution of dark matter that accompanies galaxies and galaxy clusters. Moreover strong lensing can provide yet another way to study dark energy. For example, cosmological parameters, including dark energy, will affect the abundance and frequency of strong lensing systems and hence influence how many such systems we'll find in DES. The lensed quasars are particularly useful for determining the Hubble constant which governs the rate of expansion of the universe. We expect to find many new lenses quasars in DES.

In order to use these strong lenses for constraining dark matter and dark energy we need to know how far away they are and we do this by measuring their redshifts. We observe the object and obtain a spectrum of it's light and look for features such as absorption lines and emission lines. These features can be compared with known features in the spectrum of various chemical compounds found on earth. If the same features are seen in an observed spectrum from a distant source but occurring at shifted wavelengths then the redshift can be calculated. Each lensing system typically contains multiple images of the source object so we will use the GMOS instrument in its multi-object mode to efficiently obtain many spectra simultaneously.

In addition to the primary lensing targets, we are also piggybacking observations of about another 50 galaxy targets per field, for a total of about 3000 galaxy redshifts over the course of our full program. This sample will be used to improve the measurement of the redshift distribution of faint DES galaxies, by providing a galaxy sample distributed over many fields spread across the DES footprint, as opposed to our present situation of relying on a small number of fields for this purpose. Better knowledge of the galaxy redshift distribution will in particular be used to help improve the determination of dark energy cosmological parameters by DES.

The team consists of 29 scientists from the USA, Australia, Brazil, the United Kingdom, Switzerland, Japan and Taiwan.

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GS-2015B-LP-6 Characterizing Dusty Debris in Exoplanetary Systems
Principal Investigator: Christine Chen (Space Telescope Science Institute)

Proposal Abstract: Studying debris disks is one of the frontiers of exoplanet science because observations of these objects provide direct constraints on planetary system formation and planet migration around other stars. To date, twenty-four debris disks have been spatially resolved in scattered light, revealing the location of the dust and the albedos of the grains when compared with thermal emission measurements. Although these observations help break some of the degeneracies between composition, size, porosity, and shape, the detailed grain properties are still not well understood. A key limitation is that the previous generation of instruments lacked the contrast and image fidelity to detect dust disks within a ~1.5 arcsec radius. Therefore the thermally emitting dust detected close to the star is not the same cold grain population detected by scattered light observations far from the star. We propose to obtain Gemini Planet Imager (GPI) Integral Field Spectroscopy (IFS) and Polarimetry of all of the debris disks spatially resolved in scattered light observable from Gemini South. GPI offers an unprecedented discovery space by virtue of its small inner working angle and sensitivity using dual channel polarimetry. IFS observations will be sensitive to spectral features and better constrain the color of the scattered light and therefore the particle composition and size. Polarimetry will allow us to break the degeneracy in forward scattering between particle size and porosity. Our team will combine the proposed GPI observations with complementary high contrast imaging and thermal mapping data from HST, MagAO, and ALMA to develop hollistic models that will significantly improve our understanding of the materials available during the late stages of planetary system formation.

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GS-2016A-LP-8 Dynamical Masses of Black Holes and Neutron Stars from the Galactic Bulge Survey
Principal Investigator: Robert Hynes (Louisiana State University)

The Galactic Bulge Survey (GBS) is a Chandra flux-limited X-ray survey of faint X-ray sources towards the Galactic Bulge. Chandra has now completely imaged an area of 12 square degrees in two strips above and below the most extincted regions of the Galactic Plane (see Figure). Our survey is broad in area but shallow in order to maximize the numbers of moderately luminous sources, principally quiescent low-mass X-ray binaries (LMXBs), relatively to less luminous sources such as active stars. The Chandra observations have yielded 1640 unique sources and are complemented by many multiwavelength supporting observations including optical variability surveys, multi-object survey spectroscopy and UV imaging with Swift. It also overlaps with other key surveys such as VVV and OGLE. The Galactic Bulge Survey collaboration includes scientists from the Netherlands, United States, United Kingdom, Chile, and Canada.

Figure 8: GBS sources overlaid on the VVV extinction map. Circles indicate X-ray brightness and the seven brightest objects are numbered: CX1 is a transient LMXB in outburst, CX2 is a background active galaxy, CX3 is a low luminosity persistent LMXB, CX4 is an active K giant, CX5 is a magnetic CV, CX6 is a Be star, and CX7 is a pre-main sequence K star.

We expect the GBS sample to be dominated by i) quiescent LMXBs; ii) cataclysmic variables (CVs), and iii) active stars and binaries. Based on our best estimates of source populations from population synthesis models, typical source properties, and appropriate reddening for our fields, we expect about 300 LMXBs in the X-ray sample, of which half should have accessible optical counterparts. The large predicted number of LMXBs is a consequence of the predictions of population synthesis models that there must be many unseen quiescent systems. Only a fraction of these predicted Galactic LMXBs have been identified leaving the credibility of the population synthesis results in question. The only way to confirm the predictions is to search for the systems while they are in quiescence. This will provide the most robust estimate of the number of black hole binaries in the Galaxy, and test our understanding of binary evolution.

The X-ray selected sample of LMXBs and CVs can be used to measure masses of black holes and neutron stars, and white dwarfs respectively. Dynamical masses are often the only secure way to discriminate between these source classes, and can address multiple science questions in their own right including i) the true stellar mass black hole mass distribution; ii) the reality of the apparent mass-gap between neutron stars and black holes; iii) the maximum mass of neutron stars; and iv) the discrepancy between predicted and observed white dwarf mass distributions. Masses derived from GBS objects will have less selection effects, or at least different selection effects, to the currently known masses.

The GBS collaboration will use this Gemini-S Large and Long program to measure radial velocity curves for a sample of the LMXB and CV candidates discovered by the survey and classified based on photometric lightcurves and spectroscopic snapshots. We will discriminate between LMXBs and CVs, and measure masses for all of the selected objects. This will be the first systematic sample of dynamical masses obtained from an X-ray selected survey, and the LMXBs identified will be the first such objects found in quiescence outside of globular clusters.

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GN-2015B-LP3, GN-2015B-LP-6 The First Survey Dedicated to the Detection and Characterization of Clouds in Exoplanet Atmospheres
Principal Investigator: Catherine Huitson (University of Colorado at Boulder)

Recent exoplanet transit observations have detected evidence of high-altitude clouds in the majority of targets, although the species remain unknown. Our survey is the first program dedicated to not only detecting clouds, but also discovering the cloud condensate species. Knowledge of cloud species is essential in order to dis-entangle cloud signatures from atomic and molecular signatures in exoplanet transit spectra (a transmission spectrum measured when the planet passes in front of the star). The atomic and molecular measurements are the only way to detect atmospheric compositions of these planets, which are important for understanding formation history and searching for biosignatures in future observations.

So far, there is no correlation between presence of clouds and planet temperature, with even >2000 K atmospheres showing evidence of substantial cloud cover. Given the diversity of atmospheres shown to exhibit clouds, we propose to sample a representative cross-section of the hot gas giant population to try to link cloud properties with easily-measurable bulk properties such as planet temperature and surface gravity (Figure 1). This will unable us to better understand cloud formation pathways in the exoplanet population.

Figure 9: Mass-radius diagram of known extrasolar planets focusing on larger objects, which are accessible to transmission spectroscopy. Our target selection will explore a representative sub-sample of the gas giant population.

Figure 10: Example transmission spectra in the blue optical produced by different types of clouds, with different condensate grain sizes. Also shown are the GMOS wavelength coverage and predicted co-added precisions for the data.

We plan to use 95 hours of Gemini/GMOS time over 2 years to observe blue optical transmission spectra of our targets multiple times to reach high-precisions. In the blue optical, planet atmospheres display no atomic or molecular features and cloud scattering signatures dominate the transmission spectra. Modeling of the scattering signatures will be used to identify cloud condensate grain sizes and hence cloud species (Figure 2). The results can then be used to understand the contribution of clouds to the longer-wavelength transmission spectra, where atomic and molecular features are observed. This will enable reliable retrieval of abundance and composition measurements.

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GN-2015B-LP-5 Validating K2’s Habitable and Rocky Planets with AO Imaging
Principal Investigator: Ian Crossfield (University of Arizona)

Proposal Abstract: K2, the repurposed Kepler mission, offers a golden opportunity to find a wide diversity of new planetary systems orbiting bright stars. We are executing a large-scale collaboration using K2, the updated Kepler mission, to find these new systems around all stellar types in the K2 fields. We anticipate finding dozens of potential targets suitable for atmospheric studies with HST and JWST, and many more for which RV spectrosopy will further elucidate the low-mass planetary mass-radius relation. Over the next two years, we request four nights per semester to eliminate false positives and continue validating our K2 planetary systems using GNIRS AO imaging and our DSSI Speckle Camera. Eventually, our program will measure the occurrence rates of planets across the sky, optimize target selection strategies for TESS, and find exciting new targets for early-science JWST atmospheric characterization.

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GN-2015B-LP-7 A GNIRS Near-IR Spectroscopic Survey of z>5.7 Quasars
Principal Investigator: Yue Shen (University of Illinois at Urbana-Champaign)

Recent searches for high-redshift quasars have discovered more than a hundred quasars at z>~6, and start to enable a detailed understanding of the assembly of the earliest supermassive black holes (BHs) and their hosts, one of the latest frontiers in galaxy formation studies. These impressive statistics now enable a transition from individual case studies to the more important ensemble studies of high-z quasars, and motivate novel statistical approaches that were not possible with the earlier small sample. Spectroscopy of these highest-redshift quasars contains rich information about their physical properties and provides the estimation of their BH masses using the broad emission lines. Unfortunately for these high-z quasars, near-IR spectroscopy is necessary to expand the wavelength coverage in the rest-frame UV.

Figure 11:A history of the Universe from the Big Bang to the present day (image credit: STScI). The inset on the left shows the collection of quasar BH masses as a function of redshift. There are currently only ~ a dozen quasars at z>~6 with measured BH masses. Our Gemini Large and Long program will increase this number dramatically, enabling a statistical study of the assembly of these earliest SMBHs at cosmic dawn.

This program will observe 60 z>5.7 quasars with GNIRS near-IR spectroscopy to study their physical properties (such as BH masses, metallicities, and absorption). Combined with our joint efforts from other programs, we will assemble the largest sample of high-z quasars with near-IR spectroscopy, and obtain a complete census on the demography and rest-frame UV properties of these earliest SMBHs. These near-IR spectra will enable a diverse range of science applications and synergy with multi-wavelength investigations, and will remain state-of-the-art throughout the next decade until the era of 30-meter class telescopes (GSMTs). The proposed studies here will provide the anchoring point for future studies with much fainter high-z quasar samples from WFIRST and GSMTs.

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