Keck Science Meeting 2020

Talk Abstracts & Titles

The following talks will be presented at the meeting:

Thomas Bohn (UC Riverside)Near-Infrared Coronal Line Observations in Dwarf Galaxies hosting AGN-driven OutflowsRecent studies have suggested the intriguing possibility that AGN feedback in dwarf galaxies may be just as important as in their more massive counterparts. We have obtained Keck NIRES spectroscopy of a sample of 9 dwarfs, that likely display galaxy-wide, AGN-driven outflows, to search for coronal line (CL) emission that is indicative of AGN activity. We find strong CL emission in 4/9 galaxies (44%) with line ratios incompatible with shocks, confirming the presence of AGN in these galaxies. Similar CL detection rates are found in larger samples of more massive galaxies hosting type 1 and 2 AGN. We investigate the connection between the CLs and galaxy-wide outflows by analyzing the kinematics of the CL region, as well as the scaling of gas velocity with ionization potential of different CLs. In addition, using complementary Keck KCWI observations of these objects, we draw comparisons with the kinematic properties of the spatially resolved outflows with the CL properties in our sample. These results provide further evidence that outflows can be driven by lower mass AGN.
Geoff Chih-Fan Chen (UC Davis)Lens modeling and time-delay prediction of J0924+0219 strong lens system with Keck AO dataThe Hubble constant is one of the most important parameters in cosmology. Its value directly sets the age, the size, and the critical density of the Universe. Despite the success of the flat LCDM model, the derived Hubble constant from Planck data under the assumption of a flat LCDM model has 4.4-sigma tension with the direct measurements. If this tension is not due to the systematics, it may indicate the new physics beyond the standard cosmological model. H_0 from time-delay lensing is a powerful independent tool for addressing the H_0 tension since it is independent of both Planck and the distance ladder. One way to do this is to increase the number of high-quality lens systems since this allows us to look for correlations and other effects due to systematics, and to do hierarchical approaches to assess known systematic effects. Keck AO data is not only the key component to increase the precision of H0 measurement but also provides systematic checks with the H0 results based on HST imaging. I will present the lens modeling results of the J0924+0219 strong lens system using Keck AO data and show its time-delay prediction under the LCDM model.
Jeff Cooke (Swinburne University)The Keck Wide-Field ImagerThe Keck Wide-Field Imager (KWFI) is a proposed wide-field UV-sensitive optical camera for Keck prime focus. With its simple and straightforward design, KWFI will be the most powerful wide-field camera in the world and the only such 8m-class camera sensitive down to ∼3000A for the foreseeable future. The main aims of KWFI are to exploit the superior atmospheric UV transmission on Mauna Kea and the large aperture and fast focal ratio of Keck to enable extremely deep (m ~ 28-29), 3000-10000A wide-field science. KWFI enables science that cannot be done by any other telescope, including future 30m-class telescopes. KWFI has strong synergy with existing and proposed Keck instruments and fills a crucial gap for extremely deep 3000-5000A imaging for upcoming OIR and UV space missions and is capable of detecting extremely faint and rare targets for TMT and JWST. KWFI will enable the Keck community to be the only community able to resolve several long-standing problems that span nearly all areas of astronomy, from the Solar system, to the distant Universe, to the dynamic Universe.
Jeffrey Cummings (Indiana University)Carbon Star Formation as Seen Through the Non-Monotonic Initial-Final Mass RelationThe initial-final mass relation (IFMR) links the birth mass of a star to the mass of the compact white dwarf left at its death. While the relevance of the IFMR across astrophysics is universally acknowledged, not all of its fine details have yet been resolved. Our analysis with Keck/LRIS of low-mass white dwarfs in older open clusters and one globular cluster has led us to identify a kink in the IFMR, located over a range of initial masses: 1.65 to 2.10 Msun. The kink's peak occurs at stars with Minitial of 1.8 to 1.9 Msun, where they are found to produce overmassive white dwarfs at Mfinal of 0.70 to 0.75 Msun. These peak white dwarfs are ~0.1 Msun more massive than modern evolutionary models predict. We interpret this IFMR kink as the signature of carbon star formation in the Milky Way, where this kink's formation can be reproduced in our models by including the sensitivity of AGB mass-loss rate to their surface C/O ratio. This finding is critical to constraining the evolution and chemical enrichment of low-mass stars.
Rajeshwari Dutta (Durham University)Metal-enriched gaseous haloes around z~1 galaxiesGalaxy formation and evolution models are incomplete without a quantitative understanding of the gas flow cycle occurring in haloes around galaxies, i.e. in the circumgalactic medium (CGM). However, at present our understanding of what drives these gas flow processes is limited, especially at intermediate redshifts around z~1, mainly due to lack of sufficient observations that link the gas flows traced in absorption to the emission from galaxies around them. We have recently conducted a study of the cool metal-enriched CGM gas, traced by MgII absorption in high-resolution high-S/N optical spectra from HIRES/KODIAQ of background quasars, around a statistical sample (~200) of z=0.8-1.5 [OII] emitting galaxies using the VLT/MUSE large programme, MUSE Analysis of Gas around Galaxies (MAGG). I will present some key results from this study including: (i) the radial and azimuthal profiles and covering factor of metals around z~1 galaxies, and (ii) the role of galaxy properties like stellar mass and the environment in determining the observed distribution of metals in the CGM. Further, comparison with similar studies at lower redshift (z~0.5) will be used to trace the evolution of the link between CGM gas and galaxies.
James Esdaile (Swinburne University)Velocity dispersion measurements of massive quiescent galaxies at 3 < z < 4.Measuring galaxy kinematics offers the opportunity for independent measurement of the galaxy stellar mass which in turn tests our understanding of the galaxy's stellar populations and distribution of stellar masses in the form of the initial mass function (IMF). High redshift massive and quiescent galaxies are both very compact and contain high stellar masses such that their expected stellar velocity dispersions are on the order of 300-500 km/s. This allows measurements of integrated velocity dispersions with ground based NIR spectrographs with sufficient spectral resolution sampling i.e. $\sigma$ > 3 x instrument dispersion.We present the velocity dispersion measurements of four massive quiescent galaxies at 3 < z < 4, the largest sample of the most distant massive quiescent galaxies to date. Our sample contains deep H and K spectra using the MOSFIRE NIR spectrograph. Using sizes derived from HST imaging and converting velocity dispersion measurements to dynamical masses shows an average = -0.1 dex. Disagreements between stellar and dynamical mass can be attributed to variations in IMF, non-virial kinematics such as rotationally supported galaxies or high inner dark matter fractions. This result indicates one or both of a more top heavy IMF or rotationally supported kinematics.
Sara Faggi (NASA/GSFC)The extraordinary passage of comet C/2020 F3 (NEOWISE): investigations of its organic composition as revealed by NIRSPEC2.0 at Keck IIIn August 2020, we acquired high-resolution spectra of the Oort cloud comet C/2020 F3 (NEOWISE) after its perihelion that occurred on July 3rd 2020. Observations were conducted using NIRSPEC2.0 - the near-IR high-resolution echelle spectrograph at Keck II. Comet C/2020 F3 (NEOWISE) was observed on August 3rd and 5th 2020 using the KL1 customized instrument setting, covering the 2.87 - 3.70 mm range. Fluorescent emissions from water, CH3OH, NH3, NH2, H2CO, CH4, C2H6, C2H2, were detected, and upper limits for C2H4 will be presented. These species are relevant to astrobiology, owing to questions regarding the origin of pre-biotic organics and water on terrestrial planets. A sensitive search for deuterated water was conducted; results will be discussed. Nuclear spin temperatures, rotational temperatures, and production rates were determined for selected species, and will be presented. The unique activity of the comet together with the extraordinary capabilities of NIRSPEC2.0 and the large Keck II collecting area provided unique results. The KL1 NIRSPEC2.0 setting combines a wide instantaneous spectral grasp with high accuracy, thus eliminating many sources of systematic errors when retrieving molecular and isotopic abundances. Future comparisons amongst comets will clarify the nature and meaning of cosmogonic indicators derived from chemical and isotopic compositions.
Abhimat Gautam (UCLA)Discovery of a Candidate Old Ellipsoidal Binary System at the Milky Way Galactic Center and Dynamical Constraints on a Dark CuspSupermassive black holes, like the one in the Milky Way Galactic Center (GC), are predicted to be surrounded by a high density cusp composed of stars and stellar remnants. However, a cusp of dark, stellar remnants is difficult to observe and test the presence of directly. The disruption of stellar binary systems by dynamical encounters is a way to probe such a dark cusp. In my talk, I will present our discovery of a new periodic variable star at the GC, using near-infrared Adaptive Optics photometry and astrometry taken with the W. M. Keck telescope over 13 years. Our observations and models have revealed that this variable star's observed properties are best explained as a red giant ellipsoidal binary system at the GC, with a binary orbital period of ~79 days and an age between 3 to 13.5 Gyr. This is the first candidate old stellar binary system discovered in the GC. If such an old, long-period binary has been present at the GC over its entire lifetime, its presence implies few encounters with sources that would disrupt the binary. The old binary's orbital parameters therefore can place novel upper limits on the number of stellar remnants in the Galactic Center within ~0.1 pc of the central supermassive black hole and the presence of a dark cusp.
Erin Hicks (University of Alaska Anchorage)The Keck OSIRIS Nearby AGN Survey: The Distribution and Kinematics of the Circumnuclear Stars, Molecular Gas, and Ionized Gas in Local Seyfert GalaxiesThe Keck OSIRIS Nearby AGN (KONA) survey aims to characterize the feeding and feedback processes within the central 500 pc of a sample of 40 local, representative AGN. A comparison of the distribution and kinematics of the circumnuclear stars (CO 2.29 micron bandheads), molecular gas ( H2 2.12 microns), and ionized gas (Br G and [Si VI] emission at 2.16 and 1.96 microns, respectively) will be presented. We find that the line of nodes of the central stellar disk generally aligns with the near-IR photometric axis on large scales. The molecular gas emission follows a similar radial distribution as the stars, with half of the sample showing misalignment of the molecular gas and stellar disk. While the molecular gas is primarily rotating in the galaxy plane with relatively low velocity dispersion, the ionized gas is typically more centrally concentrated with higher velocity dispersion indicative of outflows. In addition, the [Si VI] velocity dispersion tends to be higher in Seyfert 1s compared to type 2s while no such subsample difference is found in the molecular gas component. Estimated masses of the central reservoir of gas suggests at least an order of magnitude more gas is available than needed to power these AGN. These circumnuclear properties will be discussed in the context of kpc scale structures traced via HST and NIRC2 generated dust structure maps, and trends of these properties over the three orders of magnitude in hard X-ray and K-band luminosities spanned by the KONA sample will be presented.
Brad Holden (UCO/Lick)Ideas and Concepts for a New LRISThe Low Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) is a flexible and highly efficient instrument. Despite being 27 years old, it is scheduled for ∼100 nights a year and is still producing unique scientific results. LRIS, however, suffers from mechanical instability that compromises observations, an off-axis location leading to significant optical aberrations, and aging subsystems whose maintenance is an increasing burden on the WMKO summit staff. Now is the optimal time to plan a successor. Keck has recently deployed instruments - KCWI and MOSFIRE - that have many of the improvements one would like for LRIS: a wide wavelength range using modern dispersive elements, an on-axis field of view, and extremely stable, repeatable spectral format. We will outline what sort of instrument would be the best replacement for LRIS, leveraging as much as possible the recent engineering work done for KCWI, KCRM, MOSFIRE, and TMT-WFOS. If Keck is upgraded in the future with an adaptive secondary to enable GLAO, the delivery of an optical spectrometer capable of capitalizing on GLAO performance will be crucial. The time required to build a state-of-the-art instrument suggests that the Keck community needs to plan now for new instrument to meet that need.
Denise Hung (University of Hawai'i)Optical/NIR Discovery of Large Scale Structure and the Characterization of the Cluster Mass Function at z~1The Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey is an ongoing imaging and spectroscopic campaign initially designed to study environment effects on galaxy evolution in known high-redshift (z~1) large-scale structures. The combination of rich optical and near-infrared multi-band imaging data, the wealth of spectroscopy obtained primarily from Keck/DEIMOS, and a powerful new technique, Voronoi tessellation Monte-Carlo (VMC) mapping, allows us to find serendipitous galaxy overdensities between redshifts of 0.55 < z < 1.37 with extreme sensitivity across the entire redshift range. Using VMC mapping we are able to measure precise systemic redshifts, provide an estimate of the total gravitating mass, and maintain high levels of purity and completeness at z~1 even with moderate levels of spectroscopy across more than an order of magnitude in total mass. We use the discovered structure to construct a cluster mass function and perform basic cosmological fitting that previously was only accomplished in the local universe for optical datasets. These strengths attest to VMC mapping's potential to be a powerful tool for current and future wide-field galaxy evolution surveys at z~1 and beyond.
James Kirk (CfA)Keck II/NIRSPEC detection of helium in the atmosphere of the sub-Saturn mass exoplanet WASP-107bIn the last two years, the helium triplet at 10833A has emerged as a powerful new method to observe exoplanetary mass-loss. Prior to this line's detection, observations of exoplanet mass-loss were primarily limited to space-based studies of Lyman-alpha, which suffered heavily from interstellar extinction and geo-coronal contamination. The helium triplet, however, can be observed from the ground at high-resolution. I will present the first Keck II/NIRSPEC detection of helium in an exoplanet's atmosphere, which we detected at 30 sigma confidence. Our demonstration of Keck II/NIRSPEC's ability to observe helium in an exoplanet's atmosphere highlights the important role that NIRSPEC can play in our understanding of exoplanetary atmospheric mass-loss; a process that is thought to be responsible for carving key features within the population of known exoplanets.
Nicolas Lehner (University of Notre Dame)KODIAQ-Z: Metallicity of the IGM/Galaxy Interface at z~2-4Our modern understanding of galaxy evolution relies heavily on the exchange of matter between galaxies and the intergalactic medium (IGM) to explain a broad range of observable galaxy properties. The competition between mass gain (via accretion) and loss (via outflows) plays out in the circumgalactic medium (CGM), the interface between the IGM and galaxies. The metallicity of the CGM gas is one of the key diagnostics to characterize since it directly informs us on the level of enrichment of the gas and hence its origins (IGM, galaxies). Here I will discuss new results stemming from the KODIAQ-Z program that uses Keck HIRES and ESI observations to infer properties of the CGM gas at z~2-4. Using results from the COS CGM Compedium z<1, I will discuss the evolution of the metallicity distribution of the IGM/galaxy interface over the last 12 billion years. I will finally present that latest KODIAQ data release in the Keck Observatory Archive that consists of fully reduced ESI spectra of 729 quasars at 0.1
Simon Murphy (The University of Sydney)Confirming invisible compact stellar remnants found by pulsation timing using Keck/HIRESHigh-mass stars almost always form in binary or multiple systems. When the massive component ends its life in a supernova explosion, it leaves behind a massive compact remnant: a neutron star or a black hole, whose dynamical mass is still detectable in systems that are not distrupted. Using a catalogue of ~340 pulsation-timing binaries found with Kepler, we have selectively observed the systems with the largest mass functions with Keck/HIRES. If the large mass functions originate from main-sequence pairs, they are detected as SB2 systems. However, in some systems only the spectrum of the pulsating component is seen, and the measured RVs correspond to the pulsation-timing orbit. That is, they are SB1s and they contain an invisible compact remnant. Two caveats complicate this picture: firstly, the stars are pulsating, so they have line-profile distortions and velocity shifts on timescales of hours; and secondly, these pulsating stars rotate rapidly, with vsini typically 100 km/s or greater. The unique sensitivity of Keck/HIRES and pseudo-queue capabilities through the Caltech/UC/UH HIRES collaboration provide a powerful tool to overcome these obstacles. In this talk I will present first results from the project, including compact stellar remnant candidates that may be the closest known black holes to Earth.
Myriam Prasow-Émond (Université de Montréal)The first high contrast images of near, high-mass X-ray binariesX-ray binaries are unique laboratories for studying a variety of astronomical phenomena under extreme conditions. Some studies indicate that sub-stellar companions such as exoplanets and brown dwarfs can exist in a variety of environments, and it was recently argued that X-ray binaries could host planetary systems. However, in high-mass X-ray binaries (HMXB) - where the donor star is a massive O-B spectral type star - the system is generally orders of magnitude too bright to detect sub-stellar companions. Using the vortex coronagraph from NIRC2, we therefore recently obtained the first high contrast images for nine near HMXBs: RX J1744.7-2713, IGR J18483-0311, SAX J1818.6-1703, 1H2202+501, IGR J17544-2619, 4U1700-37, 4U2206+543, RX J2030.5+4751 and γ Cassiopeiae (Be star). In this talk, we present impressive preliminary results: we found evidence of one or many sub-stellar companions around most of those extreme systems. A statistical study will soon be conducted to better understand, among others, the formation of Jupiter-like exoplanets, the frequency of the sub-stellar companions in X-ray binaries, as well as their impact on the system.
Emily Ramey (UC Berkeley)Analyzing long-term performance of the Keck-II adaptive optics systemAs development begins on new, cutting-edge adaptive optics (AO) technology, it is useful to evaluate the long-term behavior of existing AO systems to determine which factors influence overall performance most strongly. The W. M. Keck Observatory is one of the longest-running laser-guide star (LGS) AO systems in use today and represents an excellent test case for analyzing such long-term AO performance. We utilize Keck LGS AO observations of the Galactic Center, which has been observed consistently since 2006, in order to explore trends in the delivered image quality, combining image metrics such as Strehl, FWHM, and photometric precision with AO telemetry, MASS/DIMM turbulence profiles, seeing information, and weather data. We employ machine learning techniques to evaluate the predictive power of different parameters on our chosen image metrics. We will also release the complete data to the public as a resource for testing new predictive control and PSF-reconstruction algorithms.
Vikram Ravi (Caltech)Fast radio burst science: progress and promiseMore than ten fast radio bursts (FRB) have now been localized to individual host galaxies, at redshifts between 0.03-0.66. A variety of progenitor environments have been revealed, from giant HII regions to unremarkable locations in relatively quiescent galaxies. I will review the critical role played by optical observations in characterizing FRB hosts, with a focus on Keck observations of the field of FRB 190523 localized by the Deep Synoptic Array (DSA) prototype. Using FRB 190523 and the first localized FRB (121102) as case studies, I will present new observations that show how FRBs can probe the bulk contents and density fluctuations of ionized gas in, around, and in between galaxies. I will conclude by outlining plans for a systematic exploration of the FRB host galaxy population based on FRBs detected by the DSA project. These observations will address the two fundamental questions in the study of FRBs: their sources, and the nature of the medium through which they propagate.
Bronwyn Reichardt Chu (Swinburne University)Mapping Outflows in Starbursting Disk Galaxies with DUVETI will present results from our pilot observations for the DUVET survey of starbursting galaxies using the Keck Cosmic Web Imager. DUVET is a collaborative program using time from Swinburne, UC and NASA allocations which aims to use hyper-sensitive observations of starbursting disks to probe the subgrid physics of feedback models. Star formation is regulated within galaxies by the feedback process. However, the details of how feedback works, particularly within galaxies at the peak of cosmic star formation, are unclear. Galaxies at z>1 have different properties to local Milky Way-like spirals, with high star formation surface densities, gas fractions and turbulent motions. The DUVET survey uses KCWI to make resolved observations of star-formation driven outflows in a rare sample of nearby galaxies with properties well-matched to main-sequence galaxies at z~1-2. We are measuring the spatial distribution of outflows and their chemistry in these galaxies at sub-kpc resolution. Our pilot observations reveal that (1) outflows are ubiquitous in these galaxies, with all lines-of-sight having gas flows at 300pc resolution. These results are different from local observations, which find that outflows are generally concentrated in the centre of galaxies in biconical geometries. (2) Using our observed outflows, we are able to discriminate between widely used models of feedback in galaxies.
Lee Rosenthal (Caltech)The California Legacy Survey: Population Statistics With an Expanded Catalog of RV-Detected ExoplanetsThe California Planet Search team has been conducting a radial velocity survey of over 700 nearby F/G/K/M stars for the past three decades, using the Keck-HIRES, Lick-Hamilton, and APF-Levy spectrographs. Our team has collected more than 100,000 observations, using almost three years of open shutter time. We describe a systematic search for periodic signals and long-term trends in our dataset, and a scheme for validating signals as confirmed planets. We present a catalog of over 170 validated exoplanets found in our survey, including more than a dozen discoveries. These newfound exoplanets range from sub-Neptunes within 0.2 AU of their host stars, to eccentric gas giants beyond 10 AU. We highlight some of the newly discovered systems, and use the catalog to explore planet occurrence across several axes. We compare the eccentricity distributions of several planetary and substellar subpopulations, and find that our population of single-giant systems has a long tail not present among multi-giant systems. We also use our catalog to compute the conditional occurrence of cold gas giants given the presence of inner small planets, and place a novel lower limit on the conditional occurrence of inner small planets given the presence of cold gas giants. This last measurement might inform the design and execution of future extreme precision radial velocity searches for small planets.
Namrata Roy (UC Santa Cruz)Galactic-scale AGN driven winds in nearby elliptical galaxiesWe are investigating a population of relatively common early-type galaxies, named "red geysers", that host low-luminosity (L_1.4GHz ~ 10^22 W/Hz) radio AGN in their center. Identified in integral-field spectroscopy from SDSS IV-MaNGA survey, these red galaxies (NUV - r > 5) maintain a fairly low level of star formation (log SFR [Msun/yr] < -3). They are characterized by bi-symmetric pattern in equivalent width maps of strong emission lines (Ha, [NII], [OIII]) which appear to be tracing large scale ionized gas outflows. Ionized gas kinematics from existing MaNGA data show that the 2D velocity field is consistent with radially outflowing wind. We get further evidence for the wind interpretation through followup Keck spectroscopy of 2 red geysers using the Echellete Spectrograph and Imager (ESI) instrument. We take ESI long-slit observations of our two targets for different slit positions to sample different parts of the galaxies. A four times improvement in the spectral resolution over MaNGA allows us to search for detailed kinematic signatures of outflowing winds that were blended in MaNGA. We detect asymmetric emission line profiles that vary in a systematic manner along the wind cone which likely indicate the specific bicone geometry of the wind along the line-of-sight.
Steph Sallum (UC Irvine)SCALES: Instrument Overview and Expected Science OutcomesI will present an overview of the Santa Cruz Array of Lenslets for Exoplanet Spectroscopy (SCALES), an integral field spectrograph currently being developed for Keck. SCALES' unique 2-5 um wavelength range is designed specifically for exoplanet discovery and characterization, and will open new areas of parameter space for direct exoplanet studies. SCALES will also enable new, detailed observations of protoplanetary disks and solar system objects, and will have broader applications for non-planetary science cases (e.g. AGN, and supernovae). I will describe SCALES' modes in the context of science requirements for these various cases. I will also present simulated observations of representative targets that the team has been using to inform requirements, and discuss SCALES' anticipated scientific impacts.
Giacomo Terreran (Northwestern University)Flash spectroscopy with KeckAstronomical surveys are now able to discover supernovae (SNe) within 1-2 days of explosion. The very first light from the SN explosion illuminates and ionizes the material surrounding the progenitor star, leaving key imprints of the composition of the circumstellar Material (CSM) in the form of narrow lines in the very early spectra. These are typically emissions coming from highly ionized CNO elements, along with hydrogen and helium, and are often referred to as "flashed-spectroscopy" lines. These features are very short-lived (~ a few days) and they soon disappear, leaving space to the broad lines from the fast-moving material ejected by the SN. I will present the early evolution of a core-collapse SN showing these flash-spectroscopy lines. Taking full advantage of the fast-turnaround capabilities of Keck, we used 4 different Keck instruments to secure the spectra at these early phases. From the modeling, we were able to infer important physical characteristics of the CSM, like the chemical composition and extension. This allowed us to shed light on the mass-loss history of the progenitor star in the centuries to years before the terminal explosion, offering a deeper insight into what regulates the eruptive mass-loss events in massive stars in the final phases of their lives.
Samantha Trumbo (Caltech)Hydrogen peroxide within chaos terrain on the surface of EuropaHydrogen peroxide is part of an important radiolytic cycle on Europa. The bombardment of surface water ice by energetic magnetospheric particles converts water to hydrogen peroxide, releasing molecular hydrogen in the process. Understanding this cycle is not only important to our knowledge of the chemical composition of Europa's surface and to the study of surface-magnetosphere interactions throughout the Solar System, but it is also critical for our understanding of the potential chemical energy sources to Europa's putative subsurface ocean. The geographic distribution of Europa's hydrogen peroxide may constrain the processes governing its abundance as well as its potential relevance to the subsurface chemistry. Using NIRSPEC and the adaptive optics system at Keck, we have obtained the first high-quality, spatially resolved L-band spectra of Europa's surface. We use these data to map the geographic distribution of Europa's 3.5-micron hydrogen peroxide band. While previous disk-integrated observations seemed consistent with the laboratory expectation that hydrogen peroxide exist primarily in Europa's coldest and iciest regions, we find nearly the exact opposite in the spatially resolved data. Instead, we observe the largest absorptions at low latitudes, correlated with geologically disrupted regions known as "chaos terrain", suggesting important implications for the ocean chemistry.
Aikaterini Vandorou (University of Tasmania)The Combined Power of Microlensing and Keck Adaptive Optics for Mass Measurements of Planetary Systems"Cold exoplanets can be discovered via gravitational microlensing, which relies on the chance alignment between a background source and a planetary system. Microlensing is sensitive to planets down to Earth-masses that have wide orbits, beyond the snow line. Although microlensing provides accurate mass ratios between a planet and its host star, it does not allow direct mass measurements. High angular resolution observations taken several years after the microlensing event has occurred, allows us to resolve the source and lens (host star). By resolving these stars, we can directly measure their flux, and thus obtain precise masses for the host and planet, as well as their distance. This can be achieved with Keck's Osiris and NIRC2 adaptive optics system. The event MOA-2013-BLG-220 that comprises of a cold super-Jupiter planet orbiting a solar-type star, is an example where source and lens were resolved with Keck. There is an ongoing effort to observe other targets with Keck, such as OGLE-2016-BLG-1195, MOA-2009-BLG-387 and many more, with the aim of resolving source and lens star, rigorously measuring their fluxes, and finally, constraining the physical parameters of the planetary systems. With this data we will be able to develop a mass measurement method that will be used by the Roman Galactic Exoplanet Survey of the Nancy Grace Roman Space Telescope (formerly known as WFIRST)."
Alexa Villaume (University of Waterloo)Unexpected Spatially-resolved Age, Iron, and Alpha Gradients for the Ultra-Diffuse Galaxy DF44Initially, the large sizes and diffuse nature of ultra-diffuse galaxies (UDGs) sparked controversy over their possible origins. Now, most of the proposed formation scenarios for UDGs treat them merely as members of the canonical dwarf population with no significant changes to our understanding of galaxy evolution required to explain their presence. However, there are still substantial gaps in our knowledge of the physical properties of UDGs because of the inherent difficulty in obtaining high- or even moderate-S/N observations. Particularly crucial to understanding any galaxy is the ability to measure its stellar population gradients. When feasible to measure, stellar population gradients place strong constraints on star-formation histories and formation scenarios. For the first time, I will present spatially-resolved stellar population gradients measured for a UDG, DF44. These measurements were only feasible due to the significant S/N increase enabled by KCWI. I will show that contrary to the expectations of current UDG formation scenarios, the gradients for DF44 are not consistent with those of the canonical dwarf population and are instead consistent with DF44 being a "failed galaxy."
Jason Wang (Caltech)Early Science Results from the Keck Planet Imager and CharacterizerThe Keck Planet Imager and Characterizer (KPIC) consists of upgrades to the Keck II adaptive optics (AO) system, the NIRC2 imager, and the NIRSPEC spectrograph that have taken place in the last couple of years. I will describe the KPIC instrument and highlight some of the early science results from KPIC. Taking advantage of the improved correction on dusty stars with the new infrared AO system, we imaged the two protoplanets in the PDS 70 system and found them to be two of the lowest mass planets imaged to date. With the novel fiber injection unit of KPIC that isolates and injects planet light from the AO system into NIRSPEC via a single mode fiber, we can perform high-resolution (R~35,000) spectroscopy of high-contrast exoplanets. We obtained the first ever high-resolution spectra of HR 8799 d and e, allowing us to constrain their radial velocities, spins, and atmospheric properties to look for differences in these twin super-Jovian planets. KPIC has opened the door to high resolution spectroscopy of high-contrast directly imaged exoplanets, and I will finish with upcoming upgrades to further enhance the science capabilities of KPIC.
Shelley Wright (UC San Diego)Liger: Next generation AO-fed imager and spectrographLiger is a 2nd generation adaptive optics-fed integral field spectrograph (IFS) and imaging camera for the W. M. Keck Observatory. Liger combines a near-infrared (0.84 - 2.4 μm) imaging camera and IFS that operate simultaneously. A range of transformative science cases are enabled by coupling KAPA with Liger's unique capabilities compared to current AO-fed IFS instruments: selectable spectral resolution reaching 2x higher than any current AO IFS; shorter wavelength coverage extending to <1 micron; 4x larger field of view at fixed plate scale (and 8x larger than JWST/NIRSpec); and par-focal parallel imaging to simultaneously monitor the point spread function. We will present on Liger's instrument status and science case development and planning.
Jinyi Yang (University of Arizona)Exploring Reionization-era Quasars: Study the Early SMBHs at Redshift 7 with Keck/NIRESOur on-going z~7 quasar survey has yielded more than 35 new luminous quasars at 6.3 < z <= 7.6, which forms the first large statistical quasar sample in the epoch of reionization. I will present our recent works related to the black hole mass measurements and the study of super-massive black hole (SMBH) growth using this unique quasar sample. With the near-infrared spectroscopic observations from Keck/NIRES and Gemini/GNIRS, we measure the MgII-based black hole mass and Eddington ratio and study the properties of quasar broad emission lines. I also investigate the distribution of Eddington ratio and compare our result with previous works at high redshift (z>6) and lower redshift. These new quasars set new challenges on the formation and growth history of the earliest SMBHs, in particular our newly discovered z=7.5 and 7.6 quasars that host billion solar mass black holes. These two quasars require the most massive seed black holes compared to any other known quasars, which is more consistent with the direct collapse black hole seed model rather than the Pop III stellar remnant seed model.