| Brent Belland (California Institute of Technology) | NGC 6822 as a probe of morphological evolution of dwarf galaxies | Rotationally supported dwarf irregular galaxies appear to transition into dispersion supported dwarf spheroidal galaxies in the presence of a massive host galaxy. However, in many dwarf irregulars, the old red giant population is dispersion supported. The transition between the rotation supported gas and dispersion supported stellar population over time may reveal information about the formation history of these dwarf irregulars. As the nearest isolated dwarf irregular galaxy, NGC 6822 allows for a detailed study of this dynamical transition. I will discuss some current analysis of the evolution of rotational support with metallicity in the red giant branch stars using Keck DEIMOS observations as well as how future observations can expand upon this work. | Extragalactic | A |
| Rory Bentley (UCLA) | Alpha Element Abundances for Stars Near the Galactic Center | We use adaptive-optics assisted high-resolution (R=24,000) K-band spectra of two stars at a projected distance of >0.4 pc from central supermassive black hole, taken with with NIRSPEC instrument on the Keck II telescope to constrain overall metallicities and alpha-element abundances of the stars. We conducted calibration and testing of the full-spectral fitting technique used to analyze the spectra, using NIRSPEC observations of stars at K-band in star clusters with independently determined physical parameters. We find the galactic center stars have lower alpha element-abundances relative to globular clusters, and are more consistent with dwarf galaxies. These metal-poor chemical signatures could indicate that a population of stars exists in the Milky Way nuclear star cluster originating from infalling dwarf galaxies. | Galactic | A |
| Aparna Bhattacharya (NASA/GSFC) | Mass measurement of cold Jupiter exoplanets and their hosts | We are developing the main mass measurement method of NASA's next flagship mission Roman Space telescope ( formerly WFIRST) to be launched in 2025. This method will give >700 mass measurements of cold low mass (<5MJ) wide orbit exoplanets, a domain mostly unexplored by other methods so far. In this talk I will discuss how we developed a MCMC method to detect and measure the mass of the faintest lens host star (MB-2009-319) detected with Keck microlensing follow-up data so far. We also developed Jackknife method and ran on combination of Keck images to eliminate the uncertainty due to changing PSFs across the images. This method was used for event MB-2007-400 to detect and measure the mass of a host star 100 times fainter than its nearby source star. Both these analyses yielded a cold Jupiter planet mass around faint hosts at 7 kpc distance. Our analyses methods are unprecedented and will be used in microlensing survey (about 23% time) of Roman telescope and will aid in constraining the eta_earth before launch of HABEX/ LUVOIR. | Exoplanets | A |
| Boncho Bonev (American University) | First Comet Observations with NIRSPEC-2 at Keck: Volatile Composition and Outgassing in Prospective Spacecraft Target 46P/Wirtanen | A major upgrade to the NIRSPEC instrument at the Keck 2 telescope was successfully completed in time for near-infrared spectroscopic observations of comet 46P/Wirtanen during its "historic" close fly-by of Earth in December 2018. The exceptional commitment of the NIRSPEC engineering team in completing this upgrade before scheduled observations resulted in one of the best data sets yet obtained for parent (originally stored as ices in comet nuclei) volatiles in ecliptic (i.e., dynamically linked to the Kuiper disk) comets. The improvements in sensitivity and readout electronics are very pronounced with the new 2048 x 2048 HAWAII-2RG detector array. The large spectral grasp of NIRSPEC-2 combined with long-slit capability provides detailed view of parent volatiles that can be accomplished even without any change in instrument configuration (optics). We report findings on composition, volatile associations, and coma environment - information, which will plausibly help future evaluations of 46P/Wirtanen as a prospective spacecraft target. Based on both experience in using NIRSPEC-2 and completed analyses of the rich 46P/Wirtanen data set, this presentation will also discuss direction for future work that would utilize the unique value of Keck for comet science. Keck PI Data Award, NSF, and NASA supported members of the observing team. | Solar System | A |
| Yuguang Chen (Caltech) | Characterizing H I in CGM from Both Emission and Absorption | We present new Lyman-alpha observations focusing on the circumgalactic medium of z~2 star-forming galaxies, in both absorption and emission using Keck-LRIS and KCWI. For absorption, we use the spectra of ~3000 galaxies from the Keck Baryonic Structure Survey (KBSS) to assemble ~200,000 distinct foreground-background galaxy pairs. The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess Lya optical depth as a function of projected galactocentric distance (20 -- 4000 pkpc) and line-of-sight velocity. We compare the map with cosmological zoom-in simulation and a simple two-component (inflow + outflow) analytical model. The comparisons suggest that galaxy-scale outflow dominates the H I kinematics within ~50 pkpc, while infall and Hubble expansion dominate at >100 pkpc. For emission, we obtain deep integral field unit observations on ~50 KBSS galaxies. Their Lya spectra in the CGM is compared to the galactic azimuthal angle, determined from high-spatial-resolution broad-band images from HST. We find that Lya halos at z~2 are symmetric on average within 20 pkpc, showing no correlation with the apparent orientation of the starlight. Similar techniques will be used to study metal lines and the relationship between CGM and other host-galaxy properties in the future. | Extragalactic | A |
| Zhuo Chen (University of California, Los Angeles) | The star formation history of the Milky Way's nuclear star cluster | As the closest galactic nucleus, Milky Way's Nuclear Star Cluster (NSC) provides a distinct opportunity to resolve the stellar population and to study the composition and dynamics of this extreme environment. The complexity of NSC's star formation history has been intensively explored under this region around a supermassive black hole. Current limitation is that all previous studies have so far assumed a uniform solar metallicity in modeling based on limited chemical-abundance samples. However, age and metallicity introduce degeneracy, and bring systematic errors in characterizing the cluster properties and therefore the star formation history. The more recent spectroscopic surveys with a much larger sample size presented a significant spread in metallicity of late-type stars from NSC, which addresses the necessity of revisiting the star formation history by adding metallicity constraints. Here we present our preliminary works of reconstructing the star formation history of the NSC for the first time with metallicity constraints from measurements of individual stars. We also model for the first time 1) the early-type and late-type stars simultaneously and 2) the initial mass function simultaneously along with the star formation history, enabling the predictions of the number of compact objects and compact-objects merger rates for gravitational-wave detections. | Galactic | A |
| Devin Chu (UCLA) | Young S-Stars | The formation mechanism of the young S-stars located within an arcsecond of the supermassive black hole remains a mystery. Proposed formation scenarios for these S-stars include the tidal disruption of a binary system and migration from the clockwise disk of young stars. Identifying current binary systems among the S-stars can provide important constraints for these formation mechanisms. While binary systems are important for understanding the history of the young star cluster at the Galactic Center, there have been limited surveys for binaries of the region. With two decades of Keck integral field spectroscopy data and advanced tools for fitting mid-infrared stellar spectra, it is feasible to conduct a comprehensive spectroscopic binary search of the Galactic Center S-stars. I will present a framework for searching for spectroscopic binaries. This analysis uses 20 years of spectroscopy data and includes a sample of 29 stars located closest to the supermassive black hole. With these data and framework, I can place constraints on potential companion masses and the intrinsic binary fraction. I will also discuss how these limits have implications for the proposed S-stars' formation mechanisms. | Galactic | A |
| Maren Cosens (UC San Diego) | IC-10 3D: Properties of HII regions in Nearby Starburst Galaxy IC-10 | We have commenced a survey using Keck Cosmic Web Imager (KCWI) to map the star forming regions of the Local Group dwarf irregular galaxy, IC-10. This unique galaxy is our nearest starburst, home to over 100 HII regions and complexes, making it an ideal environment to study a large sample of star forming regions. The observations underway with KCWI allow us to study the photometric, kinematic, and ionization properties of a large sample of these regions. The highest resolution mode of KCWI gives us a spatial sampling of ~1.2pc/pixel - fine enough to resolve the most compact HII regions and the components of larger complexes. Paired with a spectral resolution of R~18,000, this allows for detailed study of the kinematic structure of these HII regions, probing the strength and frequency of outflows and the impact of star formation feedback on the interstellar medium. Combining these observations with IFS studies of local and high-redshift star forming regions will help to address the mechanisms and physical properties driving star formation over cosmic time. | Extragalactic | A |
| Thayne Currie (NASA-Ames/Subaru) | First Results from New Type of Exoplanet Direct Imaging Survey Using Keck and Subaru | We present first results from a new type of exoplanet direct imaging survey conducted with Keck/NIRC2 and Subaru/SCExAO+CHARIS. Unlike traditional, `blind' surveys (e.g. GPI, SPHERE) that typically have detection rates of ~a few percent, we use the Hipparcos-GAIA Catalogue of Accelerations to select target stars with an astrometric trend indicative of an unseen, low-mass companion(s). This survey has already yielded multiple new confirmed direct imaging discoveries and half a dozen other candidates, covering a mass range from M stars to jovian mass planets and projected separations ranging from 100 au to 5 au. I will discuss proposed follow-up data that may provide insights into the atmospheric evolution of exoplanets and brown dwarfs and the increased power of this approach due to the next release of GAIA astrometry and performance upgrades to both Keck (KPIC) and Subaru/SCExAO. | Exoplanets | A |
| Kishalay De (Caltech) | The ZTF sample of Calcium-rich gap transients: Evidence for multiple populations from low mass white dwarfs | Using the Zwicky Transient Facility alert stream, we are conducting a systematic campaign to create the largest spectroscopically classified volume-limited sample of supernovae (SNe) in the Census of the Local Universe catalog of galaxies within 200 Mpc. In this talk, I will present the design of the experiment that classified 754 SNe in the first 16 months of operations, achieving 90% completeness down to 20 mag (De et al. 2020; arXiv:2004.09029). I will present results from the first systematic search for the elusive faint and fast evolving Calcium rich gap transients using the unique capabilities of Keck for late-time nebular phase spectroscopy of hydrogen-poor SNe found in the experiment. I will present the identification of eight new events, nearly doubling the known population of events. With a combined analysis of the properties of all events, I will discuss new evidence suggesting that these events likely arise from He shell explosions on low mass white dwarfs, and thus represent lower mass analogs of peculiar thermonuclear supernovae akin to Type Ia SNe. Together, these results open up a unique new window into the fate of old He accreting white dwarfs in binary systems and the progenitors of Type Ia SNe. | Time-Domain | A |
| Simone Dichiara (University of Maryland /NASA - Goddard) | Search of short GRBs within 200 Mpc with Neil Gehrels Swift observatory | A local population of faint short gamma-ray bursts (GRBs) with late afterglow onset and bright optical kilonova was revealed by the discovery of the first binary neutron star merger GW170817/GRB170817A. In our work we investigate whether similar nearby (<200 Mpc) events were observed by NASA's Neil Gehrels Swift observatory. We selected all the events not associated to any X-ray or optical counterpart, finding 4 cases possibly associated with galaxies at distance <200 Mpc. Although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. We used ground based observation, including Keck data, to constrain the possible kilonova component and put constraints the velocity and mass of the ejecta. We then use this subsample to constrain the rate of local SGRBs. By comparing our inferred rates with the most recent results from the Advanced LIGO and Virgo O3 run we derive information about the outflow collimation and its structure. | Time-Domain | A |
| William Drechsler (UC Berkeley) | KAPA performance simulations | KAPA is the new adaptive optics (AO) system that will be installed on the Keck telescope. This will upgrade Keck's current single conjugate adaptive optics (SCAO) to a laser tomography adaptive optics (LTAO) system. This new system will employ multiple laser guide stars (LGS) instead of just one in order to improve the quality of the correction. Our goal is to use the MAOS software to simulate the performance of this proposed AO system. First, we simulated the current AO system installed at Keck to make sure the software worked reliably. Then we moved on to simulating the KAPA AO system in order to compare performance. We looked at the point-spread functions (PSFs) generated by the simulation in various directions and compared metrics such as Strehl ratio, FWHM, encircled energy, and ellipticity. The majority of these metrics were noticeably improved by the new KAPA system. Lastly, we ram simulations to test various parameters of KAPA such as asterism radius, wavelength, and radius to NGS in order to test the new system in a variety of environments. | Instrumentation | A |
| Najmeh Emami (University of Minnesota) | The ionizing photon production efficiency (xi_ion) of lensed dwarf galaxies at z~2 | We investigate the ionizing photon production efficiency, xi_ion, of lensed low-mass galaxies (74) galaxies which are likely responsible for the reionization of the universe. With deep Keck/MOSFIRE spectroscopy we measure the H-alpha luminosity and compare it to the far-UV luminosity derived from Hubble imaging in three lensing clusters (Abell 1689, MACS J1149, and MACS J0717). We found that our z~2 low-mass galaxies have elevated xi_ion (log(xi_ion)~25.4) value relative to their local low-mass counterparts, but this value is consistent with galaxies of low- and high- mass at z~2-6. We will discuss possible explanations for such high xi_ion at z~2 as well as its consequences for the cosmic reionization. | Extragalactic | A |
| Peter Kurczynski (NASA Goddard Space Flight Center) | Bridges to New Worlds: Astrophysics Themes at NASA | Have you ever wondered "How does NASA Astrophysics work?" or "How can I talk to NASA Astrophysics?" NASA supports telescope time at Keck Observatory in support of NASA Astrophysics objectives. NASA interfaces with the astrophysics research community via three main science themes: Exoplanet Exploration (ExEP), Physics of the Cosmos (PCOS) and Cosmic Origins (COR). These themes organize scientific and technical interests and perform analyses that are critical to the agency. This presentation will highlight opportunities and the benefits for researchers, especially early-career researchers to become involved. | Extragalactic | A |
| Chris Theissen (UC San Diego) | Kinematics of the ONC Core Population | We present an ongoing program to obtain high-resolution NIR spectra to measure radial velocities (RVs) of the lowest-mass members (Teff < 3500 K; M < 0.5 M☉) within the ONC core. These spectra are reduced using a custom version of the NIRSPEC Data Reduction Pipeline (NSDRP), and forward-modeled using a custom MCMC implementation. Using these data, we obtain 3-d kinematics for the ONC core population. Additionally, we apply our forward-modeling pipeline to high-resolution APOGEE spectra to extend our sample beyond 1′ of the core. Our combined sample includes the largest number of sources to-date with RVs within the ONC core (41 sources within 1′). Using this combined sample, we examine velocity trends in brightness, effective temperature, and spatial distribution of the ONC core population. Similar to previous studies, we find the ONC to likely be virial rather than supervirial. Future analysis will include robust temperature estimates to investigate kinematics as a function of mass, and search for signatures of very low-mass star/brown dwarf formation mechanisms. | Galactic | A |
| Sarah White (Rhodes University, South Africa) | The GLEAM 4-Jy (G4Jy) Sample: the brightest radio-sources in the southern sky | Powerful radio-galaxies feature heavily in our understanding of galaxy evolution. However, when it comes to studying their properties as a function of redshift and/or environment, the most-detailed studies tend to be limited by small-number statistics. I will present a new sample of ~2,000 of the brightest radio-sources in the southern sky (Dec. < 30 deg). These were observed at low radio-frequencies as part of the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, conducted using the Murchison Widefield Array (MWA). This instrument allows us to select radio galaxies in an orientation-independent way (i.e. minimising the bias caused by Doppler boosting, inherent in high-frequency surveys). Being brighter than 4 Jy at 151 MHz, we refer to these objects as the GLEAM 4-Jy (G4Jy) Sample (White et al., 2020a, 2020b). Following repeated visual inspection (using multi-wavelength information) and thorough checks against the literature, the G4Jy catalogue is now publicly available (see https://github.com/svw26/G4Jy), and includes mid-infrared identifications for 86% of the sources. With over 10 times as many sources as the best-studied, low-frequency radio-source sample that is optically complete (the revised Third Cambridge Catalogue of Radio Sources; 3CRR), the G4Jy Sample will allow models of powerful active galactic nuclei to be tested more robustly. | Extragalactic | A |
| Luke Finnerty (Caltech/UCLA) | Hot DOG Outflows with NIRES | We present rest-frame optical spectroscopic observations of 18 Hot Dust-Obscured Galaxies (Hot DOGs) with KECK/NIRES. These targets are among the highest luminosity sources from the WISE survey. We fit redshifts and emission line profiles in 16 targets, including [OIII], H-beta, [NII], H-alpha, and [SII]. Of the 13 targets with detected [OIII] emission, 12 display broad blueshifted and asymmetric line profiles, with widths ranging from 1000 km/s to 8000 km/s and blueshifts of up to 3000 km/s. These kinematics provide strong evidence for the presence of massive ionized outflows, with a median outflow rate of 230 solar masses per year. In addition, as many as seven sources show optical emission line ratios consistent with vigorous star formation, with a median Balmer-line SFR of 80 solar masses per year without extinction correction. Estimates based on SED fitting of MIR/FIR photometry suggest significantly larger intrinsic values. Black hole mass estimates indicate many Hot DOGs are accreting at or above the Eddington limit. The presence of massive outflows, ongoing star formation, and high Eddington ratios suggest Hot DOGs are a transitional phase of rapid stellar mass and black hole growth before feedback fully quenches star formation. | Extragalactic | A |
| Ben Forrest (UC Riverside) | The Massive Ancient Galaxies At z>3 NEar-infrared (MAGAZ3NE) Survey with Keck/MOSFIRE: Confirmation of Extremely Rapid Star-Formation and Quenching Timescales for Massive Galaxies in the Early Universe | We present near-infrared spectroscopic confirmations of a sample of 16 photometrically-selected galaxies with stellar masses log(M_star/M_sun)>11 at redshift z>3 from the XMM-VIDEO and COSMOS-UltraVISTA fields using Keck/MOSFIRE as part of the MAGAZ3NE survey. Eight of these ultra-massive galaxies (UMGs) have specific star formation rates <0.03 Gyr^{-1}, with negligible emission lines.Another seven UMGs show emission lines consistent with active galactic nuclei and/or star formation, while only one UMG has sSFR>1 Gyr^{-1}. Model star formation histories of these galaxies describe systems that formed the majority of their stars in vigorous bursts of several hundred Myr duration around 4<z<6 during which hundreds to thousands of solar masses were formed per year.Rapid quenching followed these bursty star-forming periods, generally occurring less than 350 Myr before observation, resulting in post-starburst SEDs and spectra for half the sample. The rapid formation timescales are consistent with the extreme star formation rates observed in 4<z<7 dusty starbursts observed with ALMA, suggesting that such dusty galaxies are progenitors of these UMGs.While such formation histories have been suggested in previous studies, the large sample introduced here presents the most compelling evidence yet that vigorous star formation followed by rapid quenching is almost certainly the norm for high mass galaxies in the early universe. | Extragalactic | B |
| Tianmu Gao (Beijing Normal University) | Spectral Energy Distributions of Supermassive Black Holes in Nearby Galaxy Mergers | The coevolution between supermassive black holes (SMBHs) and their host galaxies could be better understood by invoking AGN feedback. However, how and when AGN are triggered, particularly in merging galaxies, is difficult to pinpoint. To follow the maturation of SMBHs, we have constructed a sample of nearby galaxy mergers with the highest resolution multi-wavelength observations currently afforded by state-of-the-art observatories. By combining high-resolution data, we will generate a sub-kiloparsec SED template for obscured SMBHs in galaxy mergers and determine the AGN nature of our precisely located nuclei. As a first step, we have located the nuclear compact source in Chandra X-ray images and extracted both hard and soft X-ray band photometry of the source via spectrum fitting. We will combine the X-ray data with long-wavelength observations, including adaptive-optics near-infrared observations from Keck (which can resolve the nuclear emission in merging galaxies at the level of 10s of parsecs), and isolate its luminosity contribution from that of circumnuclear star formation in the host ISM. Thus, our multiwavelength data set will enable SED modeling that will help constrain contributions from the individual AGN components and paint a wholistic picture of how SMBHs grow through the merging sequence. | Extragalactic | B |
| Tim Gburek (UC Riverside) | The Oxygen Abundance of Dwarf Galaxies at Cosmic High-Noon | We present rest-optical MOSFIRE spectroscopy of typical star-forming dwarf galaxies at the peak of cosmic star formation through a stack of 19 gravitationally-lensed galaxies with a median z~2.41 and log(M*/Msolar) ~ 8.2. Following our study of a rare high-redshift detection of the electron-temperature-sensitive [OIII]4363 emission line in an individual galaxy in our sample (A1689-217; Gburek et al. 2019), we report a preliminary ~2.3 sigma detection of [OIII]4363 in our stack, yielding a typical electron temperature of Te([OIII]) = 15000 +/- 3000 K and a direct oxygen abundance of 12+log(O/H) = 7.9 +/- 0.2 (~0.16 Zsolar). We find preliminary evidence that the strong-line ratios and direct metallicity of the stack are consistent with locally-calibrated, oxygen-based, strong-line ratio - direct metallicity relations, supporting the notion that such relations are reliable at high redshift for estimating metallicity. Given the stellar mass of the stack, we are also able to provide a constraint on the low-mass slope of the mass - metallicity relation at z~2, roughly an order of magnitude lower in stellar mass than existing surveys like MOSDEF. This constraint will inform largely-unconstrained models of star formation and feedback in dwarf galaxies at z~2. | Extragalactic | B |
| Akshay Gowrishankar (California Institute of Technology) | Building Archival Query and Data Visualization Tools for Data-driven Sample Exploration | Telescope time is a valuable resource to the astronomy community. As more and more large data surveys are coming online, archival data science is becoming increasingly important in the field, and the need for an efficient archival query system is imperative. To this end, we have created an archival query system and interactive data visualization tool to display the availability of observational data on user-selected sources. First, the archival query tool takes as input a list of sources, specified by coordinates, and runs queries in a number of astronomical archives, including the Keck Observatory Archive. The data visualization tool then takes the output of these queries and displays the observations with a number of useful attributes, such as angular resolution and frequency coverage. The user can interactively manipulate the selection criteria and filter the data across these variables. The code, to be distributed publicly, will assist the astronomy community in utilizing various data archives and maximize the scientific value of archival science. | Other | A |
| Louis-Simon Guité (Université de Montréal) | The first high-contrast images of X-ray binaries: the case of the Gamma Cassiopeiae-like X-ray binary RX J1744.7-2713 | High-mass X-ray binaries (HMXB) are amongst the most extreme systems in the universe. The strong accretion from a compact object onto a massive star generates enormous amounts of energy. Their brightness is so strong that anything in orbit around them is outshined completely. In order to probe their immediate surroundings and see what could be found, our team obtained the first high contrast images of 10 X-ray binaries with the NIRC2 camera and a vortex coronagraph. Amongst the sample, we observed RX J1744.7-2713, an interesting system hosting a γ Cassiopeiae type star as its massive donor star. We observed 5 candidate sub-stellar companions, including 1 orbiting exceedingly close (≈ 0.25 arcsec, 300 AU) around the central HMXB. From the TRILEGAL galactic model of stellar population, we expect on average only ∼0.5 contaminant from background objects, with typical spectral type of K and M, in the field. This implies that X-ray binaries, such as RX J1744.7-2713, may provide a unique environment that promotes the formation of planets and additional stellar companions. Overall, our study emphasizes that such observations may indeed provide a major breakthrough in the field, not only for our understanding of the circumbinary environment of X-ray binaries, but also our understanding of how planets can form even in the most extreme environments. | Exoplanets | B |
| Santosh Harish (Arizona State University) | Spectroscopic confirmation of z~7 Lya galaxies from LAGER using Keck/LRIS | Lyman-alpha emitters (LAEs) at high-redshifts are powerful probes of cosmic reionization. LAGER (Lyman-Alpha Galaxies in the Epoch of Reionization) survey is the largest survey to find LAEs at z~6.9, covering 24 square-degrees of deep narrow-band imaging from CTIO/DECam. We present results of spectroscopic confirmations using Keck/LRIS. The reductions were carried out using PypeIt, a Python-based data reduction pipeline built for echelle and low-resolution spectrographs. Optimizations for line emitters and faint galaxies were developed and can be shared. We detect Lyα emission in 16 candidates (12 in COSMOS and 4 in WIDE-12 field) showing a success rate of ~80%. Four of these also have confirmations from Magellan/IMACS. These new confirmations increases the sample of spectroscopically confirmed LAEs at z~7 by a factor >3. | Extragalactic | B |
| Phil Hinz (UC Santa Cruz) | Conceptual Development of a New Technology Adaptive Secondary Mirror for Keck Observatory | Integrating adaptive optics into the telescope (via an adaptive secondary mirror(ASM)) can significantly improve sensitivity for both current AO modes, (especially at 2-5 µm), and seeing-limited instruments that employ ground-layer adaptive optics (GLAO). Nearly all science at Keck would benefit. TNO (The Netherlands Organization) has developed a technology with power efficiencies approximately 40 times that of current actuators. This technology can be leveraged to deploy an ASM that is potentially more robust, lower cost, and more maintainable than current ASM designs. I will describe the conceptual design development and testing that is ongoing to validate this technology for a possible future Keck ASM adaptive optics system. | Instrumentation | B |
| Matthew Hosek (UCLA) | A New Tool for Simulating Stellar Populations and Associated Case Study: Predictions for Compact Objects at the Galactic Center | We present the Stellar Population Interface for Stellar Evolution and Atmospheres (SPISEA), a new open-source Python package that simulates simple stellar populations. The strength of SPISEA is its modular interface which offers the user control of 13 input properties including (but not limited to) the Initial Mass Function (IMF), stellar multiplicity, extinction law, and the Initial-Final Mass Relation (IMFR). We explore an application of SPISEA for the Galactic Center: predicting the population of compact objects at the Galactic Center and the corresponding black hole-black hole merger rate as a function of the IMF derived by Lu et al. (2013) using Keck OSIRIS data. | Galactic | B |
| Dino Chih-Chun Hsu (UC San Diego) | Precise Radial and Rotational Velocities for Over 450 Ultracool Dwarfs Observed with NIRSPEC | Precise measurements of radial (RV) and rotational (vsini) velocities of stars are essential for studying stellar kinematics (space velocities and dispersions), binary orbits, and rotational dynamics (angular momentum evolution). The high-resolution spectroscopic observations necessary to make these measurements is challenging for the intrinsically faint and low temperature ultracool dwarfs (stellar and sub-stellar objects with masses below 0.1 Msun), and current velocity samples of these objects are small and incomplete. We present a radial and rotational velocity survey of over 450 late-type M, L, and T dwarfs based on forward modeling analysis of nearly twenty years of archival high-resolution data obtained with Keck NIRSPEC. We evaluate distributions in rotational velocities and atmospheric parameters (Teff, logg), identify very low mass members of nearby moving groups and associations, and statistically analyze Galactic orbits and kinematic ages of the local ultracool dwarf population. | Galactic | B |
| Liam Hunt (UC Irvine) | Ionized gas dynamics in Seyfert 1 Galaxies | Seyfert 1 galaxies exhibit broad emission lines in the optical spectrum that originate from the broad line region around their central active galactic nuclei (AGN), which could drive outflows into the interstellar medium via feedback. How these outflows depend on AGN properties such as the black hole mass is a key question in galaxy evolution. In this study, we examine the ionized gas dynamics in a sample of Sy 1 galaxies with black hole masses determined from reverberation mapping. We observed 10 nearby (z < .04) sources from the LAMP2016 survey using KCWI on the Keck telescope. These galaxies were imaged in the observed spectral range ~4600-5700A which spans our emission lines of interest, [O III] and Hbeta. We used the GIST pipeline, which employs common data routines (pPXF and GandALF) to produce emission-line analysis and stellar population properties, as well as extract gas and stellar kinematics from the provided data cube. We will present the behavior of ionized gas from our sample of AGN to determine the possible effects of feedback on the host galaxy and its evolution at galactic scales. | Extragalactic | B |
| Taylor Hutchison (Texas A&M University) | Keck/MOSFIRE Spectroscopy of Galaxies During Reionization | In the myriad of observational studies surrounding the reionization era (z>6), one point becomes abundantly clear: we are still in the discovery phase of galaxies during this time. Our knowledge of these galaxies is still in its infancy, but what little we know hints that they emit copious UV radiation, powered by massive stars with low metal content and significant ionization.While the Lyman-alpha line is the UV gold standard for finding galaxies during this epoch, the resonant line is sensitive to neutral Hydrogen -- often pushing its redshift hundreds of km/s redwards from systemic. However, the rest-UV spectra of galaxies contain a rich variety of nebular metal emission lines which can trace the systemic redshift of these distant sources, containing highly valuable information about massive stars and physical conditions in galaxies during this epoch. Such UV nebular lines are targetable at these redshifts, yet have been unexplored except in rare, individual cases. I will discuss an ongoing spectroscopic search for rest-UV nebular lines at z>6 in the CANDELS fields, including an analysis of a CIII]1907,1909 detection at z=7.5032, sharing preliminary results from the broader NIR spectroscopic program currently ongoing. | Extragalactic | B |
| Wynn Jacobson-Galan (Northwestern University) | A Double-peaked Calcium-rich Transient with Luminous X-ray Emission | We present multi-wavelength observations of the first calcium-rich transient with a luminous X-ray detection. Our observations of supernova (SN) 2019ehk span -13 to +300 days since maximum light, with our earliest detection being only ~10 hours after explosion. Nebular phase spectroscopy with Keck revealed that SN 2019ehk has the richest calcium emission of all known transients to date. We present the first pre-explosion HST + Spitzer + Chandra imaging of a Ca-rich SN explosion site, all of which place firm constraints on the progenitor system. We observed flash-ionized Hydrogen and Helium emission lines in the pre-max SN spectrum, indicating the presence of circumstellar material (CSM) surrounding the progenitor star. The luminous X-ray emission observed by Swift-XRT is coincident with an optical "flare" at -10 days before peak, both observations being consistent with shock interaction in a dense, confined CSM. We will present modeling of multi-wavelength observations and discuss the preferred progenitor scenario for this object. Finally, we will explore the implications of these observations on Ca-rich diversity and discuss how this SN constrains the formation mechanism of these intriguing explosions. | Time-Domain | B |
| Logan Jones (University of Wisconsin-Madison) | Candidate z ∼ 2.5 Lyman Continuum Sources in the GOODS-South Field | We combine HST/WFC3 F275W imaging from the Hubble Deep UV survey with the trove of deep optical spectroscopy on the GOODS-South field to select candidate high-redshift Lyman continuum (LyC) emitters. We examine the redshift range 2.35 < z < 3.05, where the F275W filter probes only the redshifted LyC, and find five candidate LyC leakers (four detected at > 3sigma significance). However, two of these show contaminating emission lines from intermediate-z galaxies along with lines from the high-z source, indicating contamination from line-of-sight blends. We also perform a stacking analysis on all 129 sources in this redshift range with UV coverage in the GOODS-S and GOODS-N and find that just a handful of candidate objects dominate the total F275W flux of this sample. We then examine the individual candidate emitters and stacked sample as contributors to the ionizing background. After correcting for the effects of LyC transmission in the intergalactic medium (IGM), we find the ionizing output of star-forming galaxies is just consistent with the UV flux required to maintain an ionized IGM at z ~ 2.5. Finally, we note that the spectroscopic properties of our candidates show a remarkable variety, with at least two showing weak or no Lyman-a in emission. This illustrates the need to continue searching for and characterizing lower-redshift analogs to the sources that drove reionization at z > 6. | Extragalactic | B |
| Marie Wingyee Lau (UC Riverside) | KCWI observations of ERQs: absence of feedback in inner halos? | Dust obscured quasars are believed to be in a young stage of quasar/galaxy evolution, when quasar feedback could be more important for driving blowouts and disrupting star formation in their host galaxies. Our team discovered a remarkable population of luminous extremely red quasars (ERQs), at redshifts z ~ 2-3 in the BOSS and WISE data. ERQs are defined by extremely red colors across rest UV to mid-IR, and they also have a suite of other extreme spectral properties that may all be related to exceptionally powerful quasar driven outflows. I will report KCWI observations of the Lya emitting halos of a sample of ERQs. The Lya emission is powered by fluorescence. As the glare of the quasar is obscured, ERQs provide unique laboratories to explore the innermost regions of circumgalactic halos. I will present results on the properties of their extended but kinematically quiet halos traced by Lya emission, and the implications for feedback. | Extragalactic | B |
| Elena Manjavacas (W. M. Keck Observatory) | MOSFIRE Spectro-photometric Variability of the planetary-mass L3 brown dwarf 2M2208+2921 | High precision time-resolved spectro-photometry provides us with information about the cloud structure at different pressure levels of the atmospheres of brown dwarfs, and directly imaged exoplanet analogs. The monitoring of the easier observable exoplanet analogs, provide an idea on how exoplanet analog atmosphere structures look like. We show the results of spectrophotometric monitoring in the J-band of the L3 exoplanet analog, 2M2208136+2921213, during ~2.5h using the MOSFIRE at the Keck 1 telescope. We find a maximum variability amplitude of 3% in the J-band, that decreases with wavelength, and slightly enhanced variability in the alkali lines. | Galactic | B |
| Vighnesh Nagpal (UC Berkeley) | Characterising the long period stellar binary HD 104304 using long baseline radial velocities and direct imaging. | Combining direct imaging astrometry and long-baseline radial velocity (RV) measurements of stellar binaries can provide precise constraints on their 3D orbits and yield dynamical masses for both components. We applied the combination of these methods to study HD104304, a binary system with a decades-long orbit containing a G8IV subgiant and a recently-discovered M dwarf companion. Using radial velocities collected over a time span of two decades by Keck/HIRES and astrometry calculated from adaptive optics images taken by Keck/NIRC2, we explored models to jointly fit the astrometric orbital motion and RV trend. Previous studies of this system (Howard & Fulton, 2016) were unable to distinguish between two and three-body solutions using RVs alone. However, we were able to break this degeneracy by incorporating images into the fit. We made 13-sigma dynamical mass measurements of the primary and secondary, finding that a slightly eccentric solution (e=0.4) is required. Dynamical n-body simulations reveal the sparsity of islands of stability for additional bodies in the system, lending credence to the two-body hypothesis for HD 104304. | Exoplanets | B |
| Casey Lam (UC Berkeley) | Hunting for isolated stellar mass black holes with microlensing | Although there are predicted to be 10^8 - 10^9 stellar mass black holes (BHs) in the Milky Way, only about two dozen of them have been detected, all in binary systems. Gravitational microlensing is one of the few ways to detect isolated BHs, which are necessary to understand the Milky Way BH binary fraction and formation channels. We present in-progress analysis of 10 isolated BH candidates with a combination of OGLE and MOA photometry and Keck and HST astrometry. Using the population synthesis tool PopSyCLE, we place these 10 candidates into an astrophysical context. For future searches, we demonstrate that careful selection of candidates is essential, as the most likely BH candidates tend to have long durations (tE > 120 days) and small microlens parallaxes (the relative parallax between source and lens normalized by the Einstein radius, piE < 0.04). We also note the importance of high spatial resolution photometry in breaking degeneracies present in seeing limited wide-field photometric surveys such as OGLE, MOA, ZTF, KMTNet, and LSST. | Galactic | B |
| Rebecca Larson (The University of Texas at Austin) | Islands of Reionization | While the end of reionization is a frequent target of observations, how this process begins, and what causes it are presently unconstrained. One scenario allows reionization to start late and complete rapidly, where moderately luminous galaxies dominate the ionizing photon budget (Robertson et al. 2015). Another scenario allows a smooth temporal evolution of reionization, where very faint galaxies, common at early times, dominate the photon budget (Finkelstein et al. 2019). These models differ drastically in their predictions for the ionized fraction at z~9 (~20% vs. ~60%), and our recent MOSFIRE program has sought Lyα emission at this epoch to distinguish between these two possibilities. We have implemented improved data reduction and stacking of spectra, which accounts for the drift of objects in the slits throughout the night, and unknown offsets of our objects from the expected location in the slit. In this talk, I will show our probable Lyα detection (5σ) at z=8.661 in the EGS field in 9.53 hours of integration. This galaxy lies physically close (3.5 pMpc) to another confirmed galaxy in this field, with Lyα detected at z=8.684 (Zitrin et al. 2015). This nearby galaxy also has a tenuous NV emission line (Mainali et al. 2018) indicating the presence of an AGN. Our source might suggest the presence of the highest redshift overdensity in the reionization era, indicate the existence of ≥1Mpc ionized bubbles as early as 500Myr after the Big Bang, and shed light on galaxy growth in the early universe. | Extragalactic | C |
| Brian Lemaux (UC Davis) | An Optical/NIR Exploration of Proto-structure Environments with Keck and VLT | The past decade has been witness to immense progress in the understanding of the early stages of cluster formation both from a theoretical and observational perspective. During this time, samples of forming clusters at higher redshift, termed "proto-clusters", once comprised of heterogeneous mix of serendipitous detections or detections arising from dedicated searches around rare galaxy populations, have begun to compete with lower-redshift samples both in terms of numbers and in the homogeneity of the detection methods. Much of this progress has come from optical/near-infrared (NIR) imaging and spectroscopic campaigns designed to target large numbers of typical galaxies to exquisite depth. In this talk I will focus on observations from VIMOS on VLT and MOSFIRE/DEIMOS on Keck, which have uncovered a large number of "proto-structures" at 2 < z < 5 that appear to resemble clusters and groups forming in the early universe. I will discuss the development of the methods for finding, confirming, and characterizing proto-clusters and proto-groups in our sample. Several case studies of spectroscopically-confirmed massive proto-clusters with a diverse set of properties will be presented. I will finally discuss constraints on the relationship between star formation rate and galaxy density at these redshifts. | Extragalactic | C |
| Zhihui Li (Caltech) | Revisiting the Gas Kinematics in SSA22 Lyman-αBlob 1 with Radiative Transfer Modeling in a Multiphase, Clumpy Medium | We present new observations of Lyman-α (Lyα) Blob 1 (LAB1) in the SSA22 protocluster region (z = 3.09) using the Keck Cosmic Web Imager (KCWI). We decode the spatially-resolved Lyα profiles using Monte-Carlo radiative transfer (MCRT) modeling. By fitting a set of multiphase, 'clumpy' models to the observed Lyα profiles, we are able to reasonably constrain many parameters, namely the HI number density in the inter-clump medium (ICM), the cloud volume filling factor, the random velocity and outflow velocity of the clumps, the HI outflow velocity of the ICM and the local systemic redshift. Our model has successfully reproduced the diverse Lyα morphologies at different locations, and the main results are: (1) The observed Lyα spectra require relatively few clumps per line-of-sight as they have significant fluxes at the line center; (2) The velocity dispersion of the clumps yields a significant broadening of the spectra as observed; (3) The clump bulk outflow can also cause additional broadening if the HI in the ICM is optically thick; (4) The HI in the ICM is responsible for the absorption feature close to the Lyα line center. | Extragalactic | C |
| John Mather (NASA/GSFC) | Orbiting Laser Guide Stars for high Strehl adaptive optics everywhere | The ORCAS (Orbiting Configurable Artificial Star) mission would provide ground-based telescopes like Keck with high Strehl diffraction-limited angular resolution at both visible and near-infrared wavelengths, opening the door to an array of unique scientific opportunities. Examples include: Milky Way galactic center; Active galactic nuclei and Supermassive Black Holes; Globular cluster cores; Supernovae and cosmology; Exoplanet imaging; Solar system; and Lensed galaxies. Orbiting laser beacon(s) would replace natural guide stars for adaptive optics, wherever and whenever desired, and could support both single and multiconjugate AO. The ORCAS mission, selected and funded for further development by the NASA AS3 solicitation in May 2020, is the fruit of a collaboration between the W. M. Keck Observatory and NASA Goddard Space Flight Center and includes industry and academia partners. We held an international virtual science workshop on Aug. 13-14 to understand the special advantages of this mission concept, and the instrumentation needs. In our talk and accompanying poster we will illustrate potential scientific objectives, display the operational concept, and discuss the path to implementation. | Instrumentation | C |
| Dimitri Mawet (Caltech) | HISPEC, the High-resolution Infrared Spectrograph for Exoplanet Characterization | HISPEC is an infrared (0.95 to 2.5 microns) cross-dispersed, R=100,000 single mode fiber-fed diffraction-limited echellette spectrograph for the Keck II telescope at W. M. Keck Observatory. HISPEC is fully optimized for: 1. Exoplanet atmosphere characterization of dozens of known systems through both transit and direct high-contrast, high-resolution spectroscopy. Infrared high-resolution spectroscopy is the most powerful exoplanet characterization tool, enabling the direct mapping of molecules present in exoplanet atmospheres (e.g. H2O, CO, CH4) and their relative abundances, spin period (length of day), planet velocity measurements (important for orbital characterization), and Doppler imaging, which can potentially reveal exoplanet weather patterns. 2. Exoplanet detection and mass measurements of hundreds of known and new systems through infrared precision radial velocity (PRV: < 30 cm/s). HISPEC will complement the Keck Planet Finder (KPF; focused on the visible) to provide PRV measurements spanning two octaves in wavelength. HISPEC will allow us to target the reddest and youngest targets and help mitigate stellar noise when combined with KPF. Besides being a timely, cost-effective machine addressing all three major exoplanet detection and characterization techniques (transit spectroscopy, direct spectroscopy, and radial velocity), HISPEC will be a powerful facility for stellar astrophysics, solar system studies, and extra-galactic science. | Instrumentation | C |
| Katherine Melbourne (Ball Aerospace) | Estimating the Ultraviolet Emission of M dwarfs with Exoplanets from Ca II and H$\alpha$ | M dwarf stars are excellent candidates around which to search for exoplanets, including temperate, Earth-sized planets. To evaluate the photochemistry of the planetary atmosphere, it is essential to characterize the UV spectral energy distribution of the planet's host star. This wavelength regime is important because molecules in the planetary atmosphere such as oxygen and ozone have highly wavelength dependent absorption cross sections that peak in the UV (900-3200 \AA{}). M dwarfs present a particular challenge to the interpretation of planetary atmospheric chemistry as they can drive production of haze particles and key planetary biosignatures. In this study, we seek to provide a broadly applicable method of estimating the UV emission of an M dwarf, without direct UV data, by identifying a relationship between non-contemporaneous optical and UV observations. Our work uses the largest sample of low-mass star far- and near-UV observations yet assembled, including data from the Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) and Mega-MUSCLES Treasury surveys, the HAbitable Zones and M dwarf Activity across Time (HAZMAT) survey, and the Far Ultraviolet M-dwarf Evolution Survey (FUMES). We evaluate the usefulness of three optical chromospheric activity indices that have been widely observed in the past. We measure average H$\alpha$ equivalent widths and \Lhabol, and the Mount Wilson \cahk{} S and \rhk{} indices using ground-based optical spectra from the HARPS, UVES, and HIRES archives and new HIRES spectra. Archival and new Hubble Space Telescope COS and STIS spectra are used to measure line fluxes for the brightest chromospheric and transition region emission lines between 1200-2800 \AA{}. Our results show a correlation between UV emission line luminosity normalized to the stellar bolometric luminosity and Ca II \rhk{} with standard deviations in the range of 0.31-0.61 dex (factors of $\sim$2-4) about the best-fit lines. We also find correlations between normalized UV line luminosity and H$\alpha$ \Lhabol~and the S index, although with significantly more scatter than \rhk{} correlations. These relationships allow one to estimate the average UV emission from M0 to M9 dwarfs when UV data are not available. | Galactic | C |
| Maxwell Millar-Blanchaer (Caltech) | Near-infrared polarimetry is coming to Keck | A new upgrade is currently under development that will bring AO-assisted polarimetry in the J-Lp bands to Keck II. The upgrade is expected to be compatible with many of the existing NIRC2 observing modes, including imaging, coronagraphic imaging and grism spectroscopy. Once complete this upgrade will consist of a Wollaston prism (installed in NIRC2 in 2019) and a set of rotatable half-wave plates that will be insertable upstream of the AO optics (currently being designed). Here we provide an update on the status of the upgrade, including a preliminary design for the half-wave plate optomechanics. In this poster will summarize the expected capabilities and present some example data (on-sky and with the telescope simulator) obtained with the Wollaston in several observing modes. The upgrade will enable new polarimetric measurements of circumstellar environments, brown dwarf atmospheres, AGN, the galactic center and more! | Instrumentation | C |
| Abby Mintz (Yale University) | Probing the High-Redshift Circumgalactic Medium (CGM) Through Quasar Absorption Line Tomography | The Circumgalactic Medium (CGM) plays a vital role in understanding the complete picture of galaxy formation and evolution, acting as a lifeline between galaxies and the surrounding Intergalactic Medium (IGM). Here we leverage a unique sample of quasar pairs to investigate the role of the CGM with absorption line tomography. From a sample of medium resolution Keck/ESI and Magellan/MagE spectra of 20 quasar pairs at redshift 2 < z < 3, we construct a catalog of metal-line absorption doublets for triply ionized carbon (C IV) and singly ionized magnesium (Mg II). The final catalog consists of over 150 C IV absorbers and over 150 Mg II absorbers with column densities ranging from 13.0 cm-2 < logN(C IV) < 15.5 cm-2 and 12.0 cm-2 < logN(Mg II) < 14.5 cm-2, respectively. We calculate the line of sight density, l(X), to trace the evolution of C IV and compare with previous studies, finding general agreement. We present the autocorrelation function, (r, v) for 7 kpc < r< 130 kpc, which describes the clustering of absorbers in our unique quasar pair sample and can help constrain the CGM enrichment history. We will combine this recent sample with previously published paired quasar spectra to produce a comprehensive measurement of l(X) and (r, v), expanding redshift coverage and broadening the range of quasar separations. | Extragalactic | C |
| Kerry Paterson (CIERA, Northwestern) | Discovery of the SGRB 181123B at z = 1.754: Implications on the delay time distribution | I will discuss the recent results of the short gamma-ray burst GRB 181123B. Thanks to optical spectroscopy with Keck, we identified this SGRB at z > 1.5, later solidified to z = 1.754 with Gemini NIR spectroscopy. As such, GRB 181123B has the 2nd highest redshift for a secure SGRB discovered with Swift to date. Rapid ToO observations on the order of hours also allowed the discovery of an optical afterglow, making it the most distant Swift SGRB with an optical afterglow detection. This discovery highlights the importance of rapid ToO observations with large telescopes, whose sensitivity can capture these faint signals, across multiple wavelengths. The discovery of the afterglow and follow-up of the host required the sensitivity of large telescopes such as Keck. With the discovered of another high-redshift SGRB, we also explore the effects of a missing high-redshift population among the current Swift sample and the implications on delay time distribution models. | Time-Domain | C |
| Eliad Peretz (NASA Goddard Space Flight Center) | Orbiting Configurable Artificial Star | The ORCAS (Orbiting Configurable Artificial Star) mission would provide the W. M. Keck observatory with high Strehl diffraction-limited angular resolution at both visible and near-infrared wavelengths, opening the door to an array of unique scientific opportunities. In this poster we will discuss the potential scientific objectives, the operational concept, the observable sky, exposure times, and orbital configuration. | Instrumentation | C |
| Alex Polanski (University of Kansas) | Wolf 503b: RV Follow-up and Characterization of a Sub-Neptune Orbiting a K-Dwarf | In 2018 Peterson et al announced the discovery of a 2 Earth Radii exoplanet orbiting the star Wolf 503. Wolf 503b is exceptional in that it orbits a relatively bright, nearby, low-mass star, enabling measurements of its size, mass, and atmosphere. Furthermore, Wolf 503b's size places it just outside of an observed lack of exoplanets between 1.5 to 2 Earth radii known as the Fulton Gap. This gap is thought to be attributed to the photoevaporation of a planet's atmosphere by UV and X-Ray radiation and Wolf503b's radius suggests that it may be in the process of having its atmosphere stripped by its host star. I will present the analysis of both the radial velocity measurements and a Spitzer lightcurve which leads to the refinement of Wolf 503b's orbital ephemeris, size, and the first determination of the planet's mass providing insight into its bulk composition. The combination of the planet's size and its parent star's brightness and proximity to earth make a it an intriguing candidate for further investigation by both the Hubble Space Telescope and the anticipated James Webb Space Telescope. | Exoplanets | C |
| Brittany Vanderhoof (Caltech/Rochester Institute of Technology) | The first optical [OII] and far-IR [CII] analysis of the ISM conditions of a galaxy at z ~ 4.58. | The conditions of the interstellar medium (ISM) in star forming galaxies at high redshift can give insight to the evolution of galaxies across cosmic time. We have analyzed the ISM of the first galaxy at z > 4.5 to have both optical [OII] and far-infrared [CII] detections. This unique combination of emission measurements from galaxies at this epoch opens a new window for studying the ISM. With the upcoming launch of JWST we will observe a more statistically sound sample of galaxies with this combination of data which will develop into a more detailed picture of the ISM in 4 < z < 6 galaxies. The larger part of this analysis was done with the [OII] detection which was observed with MOSFIRE (ID C236, PI: Scoville). This unique galaxy was observed by ALMA as part of the ALPINE project for our [CII] and FIR continuum (dust) detection, and lies in the COSMOS field providing additional ancillary data from UV to Optical. The SFRs analyzed by the [OII], [CII], FIR, and UV emission are consistent within errors indicating no significant dust obscuration of nebular emission lines, although significant dust emission is present in the FIR. This puts important constraints on the distribution of dust and gas in this galaxy and gives us new insights into other physical properties of the ISM (such as metallicity, ionization) at these high redshifts via photoionization modeling codes. | Extragalactic | C |
| Ansh Vashisth (Orange County High School of the Arts (Senior)) | A Multiwavelength Analysis of Obscured SMBH's in Nearby Mergers | This project focuses on understanding the growth pathway of supermassive black holes (SMBHs) using spectral energy distribution (SED) analysis on a sample of 22 galaxy mergers taken from the Great Observatories All-Sky LIRGs Survey. Thanks to high-resolution multiwavelength data now available from various telescope archives, emission from the innermost 50-100pc region surrounding the SMBHs can now be isolated from circumnuclear star formation. The availability of sub-arcsec resolution data across the electromagnetic spectrum from e.g. HST, Keck, and ALMA is the key to identifying the precise location of the nucleus or nuclei of interest. Long-wavelength data in particular can peer through the dust and locate even obscured active galactic nuclei (AGN) if present. Combining this set of resolved SEDs generated from these state-of-the-art images and interferometric data, we will present the aggregate template for SMBHs as they evolve among AGN stages throughout the galaxy merging sequence. | Time-Domain | C |
| Andrey Vayner (Johns Hopkins University) | Integral-field spectroscopy of powerful winds in high-redshift obscured and red quasars | Studying the impact of quasar-driven outflows in highly obscured environments is key to understanding the role of SMBH in regulating the growth of massive galaxies in the early Universe. The majority of stellar and SMBH growth occurs in dense, obscured environments at high redshifts (1.5 < z < 3). Feedback from stellar and AGN processes can drive powerful winds that can suppress star formation and SMBH growth by inducing turbulence, drive material outwards, and prevent cooling and accretion of fresh gas. Extremely-red and type-2 quasars are excellent candidates to gauge feedback in obscured environments and catch the transitional phase from dust-obscured to optically bright nuclear regions of galaxies. I will present rest-frame optical integral field spectrograph (IFS) observations of three extremely red quasars (ERQs) and one type-2 quasar at z=2-3 obtained with the OSIRIS and NIFS instruments at the W. M. Keck and Gemini North observatories along with the assistance of laser-guided adaptive optics. Using kinematics and morphologies of nebular emission lines redshifted into the near-infrared, we measure the extents, kinetic energies, and momentum fluxes of the outflows in the peculiar ERQ host galaxies' for the first time. We detect fast-moving turbulent outflows with velocities up to 3000 km/s, with a maximum extent of 2.5 kpc, likely affecting only the inner regions of these galaxies. I will discuss the potential impact of the outflows on the nuclear regions and why we believe they are excellent transitional objects at z~2 where the winds are responsible for clearing material in the inner regions of each galaxy, unveiling the quasar accretion disk at optical wavelength. | Extragalactic | C |
| Erin Redwing (UC Berkeley) | Solar System Twilight Observing Program at Keck Observatory | Many interesting planetary processes in our solar system occur quickly and suddenly, including volcanic outburst events, storms, and atmospheric phenomena. In order to study and understand the processes which drive the onset of these events, frequent observations over long periods of time are required. These kinds of frequent observations are possible at Keck through the Solar System Twilight Observing Program, which allows classically-scheduled observers to donate non-ideal time (twilight hours, bad weather, etc.) to be used for observations of bright solar system objects. In this presentation, we will explain the new features of the expanded Twilight Observing Program and highlight recent scientific publications from the Twilight Zone team. | Solar System | C |
| Bin Ren (Caltech) | Imaging exoplanets with the help from circumstellar disks | Planets form in gaseous and dusty protoplanetary disks surrounding newborn stars. Therefore, the best way to learn observationally how planets form is to watch them forming in disks. From hydrodynamical simulations we know that planets can gravitationally sculpt disks and produce gaps and spiral arms. Here we discuss how circumstellar disks influence our hunting for exoplanets using three examples. First, for the PDS 70 system, we demonstrate that a proper modeling of disk signals can reveal a known planet that is embedded in the disk. Second, for the MWC 758 system, we show that spiral arm motion can inform the location of a spiral-arm-driving planet. Third, for the Elias 2-20 system, we model the disk to discuss its influence on imaging possible gap-opening planets. | Exoplanets | D |
| Ryan Rickards Vaught (UC San Diego) | Keck Cosmic Web Imager Observations of He II Emission in I Zw 18 | With a metallicity of 12+Log(O/H)~7.1, IZw18 is a canonical low metallicity blue compact dwarf (BCD) galaxy. A growing number of BCDs, including IZw18, have been found to host strong HeII emission of uncertain origin and with enhanced intensities compared to Hβ (e.g. HeII/Hβ >1%). Conventional sources capable of doubly ionizing Helium are Wolf-Rayet and O stars. However, Wolf-Rayet stars are not detected in all HeII emitting galaxies, and modeling of the most massive O stars underpredicts HeII/Hβ by an order of magnitude. Thus far, HeII in IZw18 has been spatially resolved to arc-second scales (Kehrig et al. 2015). To better characterize the morphology of this emission, we observed IZw18 to higher sensitivity/resolution using the Keck Cosmic Web Imager. These observations reveal, for the first time, two additional HeII emitting regions. The two new regions lie along an axis which intercepts the position of IZw18's Ultra-luminous X-ray (ULX) source. Each region exhibits HeII/Hβ greater than 2%. Some of the largest HeII/Hβ enhancement occurs in a region with no detectable stellar population. These observations suggest that HeII emission in IZw18 is consistent with X-ray or shock ionized nebulae powered by IZw18's ULX source, potentially with evidence of a jet and/or ionization cone. | Extragalactic | D |
| Jean-Baptiste Ruffio (Caltech) | Atmospheric characterization of the planets HR 8799 b, c, and d at moderate spectral resolution | The four directly imaged planets orbiting the star HR 8799 represent an ideal laboratory to probe atmospheric physics and formation models. Observations of the planets in this system with OSIRIS for over a decade have provided among the most detailed look at these planets to-date. We present new R~4000 OSIRIS spectra of HR 8799d, the second closest planet to the star, at K band. We use this data and an improved data analysis to derive the first radial velocity for this planet, which is consistent with assumptions of coplanarity and orbit stability for the system. We also find that the ratio of carbon to oxygen (C/O) in this planet is consistent with the stellar composition, in-line with those measured for the other planets in the system. Measurement of this C/O ratio for all the HR 8799 planets is a critical milestone for any multiplanet system, and particularly important for large, widely separated gas giants with uncertain formation processes. The stellar C/O ratio found in all four planets implies formation via a rapid process, but does not yield definitive information about the location or method of formation. | Exoplanets | D |
| Jordan Runco (UCLA) | The MOSDEF Survey: Untangling the Emission-line Properties of z~2.3 Star-forming Galaxies | Understanding the rest-frame optical emission-line properties of star-forming galaxies during the epoch of peak star formation, i.e. z~2, is key for connecting the evolution of the stellar and gaseous content in galaxies from the early universe to today. Here, we analyze the rest-optical emission-line spectra of z~2.3 star-forming galaxies in the complete MOSFIRE Deep Evolution Field (MOSDEF) survey. In investigating the origin of the well-known offset between the sequences of high-redshift and local galaxies in the [N II] BPT diagram, we define two populations of z~2.3 MOSDEF galaxies. These include the high population that is offset towards higher [O III]λ5008/Hβ and/or [N II]λ6585/Hα with respect to the local SDSS sequence and the low population that overlaps the SDSS sequence. The full suite of the combined rest-optical emission-lines from [O II] to [S II] suggest qualitatively that star-forming regions in the more offset galaxies are characterized by harder ionizing spectra at fixed nebular oxygen abundance. Combining the rest-optical emission-line spectra with ancillary HST data and Cloudy+BPASS photoionization models allows us to investigate a wide variety of chemical and star-forming properties of the stellar population and ISM of these galaxies, which provides new insights into the physics of high-redshift star-formation. | Extragalactic | D |
| Sanchit Sabhlok (UC San Diego) | Studying High-Redshift Radio Loud Quasar Environments with KCWI and MOSFIRE | We have developed a comprehensive multi-wavelength survey of high-redshift (1.3 < z < 2.6) radio-loud quasars to study their host galaxies, circumgalactic medium, and environments. We present the latest results from the QUART survey using the Keck Cosmic Web Imager (KCWI) and Multi Object Spectrometer For Infra-Red Exploration (MOSFIRE). Using KCWI, we spatially resolve extended Lyman-alpha nebulae upto a hundred kpc away from the quasar, powered by the quasar fluorescence emission. We present Lyman-alpha images and radially averaged surface brightness profiles for 4 quasars (2.019 < z < 2.589) that have a total integration time on source between 5 and 9 hours. Using MOSFIRE we observed the fields surrounding two quasar targets, 3C9 (z=2.019) and 4C05.84 (z=2.34), to spectroscopically identify potential "proto-group" or "proto-cluster" members. We used existing photometric data from Hubble (WFC3 and ACS), Spitzer (IRAC bands) and Subaru Hyper-Suprime Camera to perform SED fits on potential targets to obtain photometric redshifts using EAZY. We will present our initial MOSFIRE results of spectroscopically confirmed sources surrounding these quasars using Hβ, [OIII] and Hα emission lines. | Extragalactic | D |
| Nathan Sandford (UC Berkeley) | Forecasting Chemical Abundance Precision for Stellar Spectroscopy at Keck | WMKO hosts world-leading spectroscopic facilities capable of measuring chemical abundance patterns for hundreds of thousands of resolved stars in and beyond the Milky Way, enabling a broad range of scientific discovery from galaxy evolution to stellar nucleosynthesis to exoplanet host characterization. However, determining the instrument configuration and observing strategy that most efficiently achieves the desired chemical abundance precision, is frequently non-trivial. In this talk, I demonstrate how Cramér-Rao lower bounds (CRLBs) can be employed to forecast the chemical abundance precision achievable with existing (HIRES, DEIMOS, LRIS) and planned (KPF, FOBOS) Keck spectrographs. Specifically, I focus on observations of (i) metal-poor, low-mass stars outside the Milky Way and (ii) solar-metallicity, FGK dwarf stars in the solar neighborhood. In addition, I show that moderate-resolution (R<5000), blue-optical configurations enable the recovery of 2-4 times as many elements as red-optical configurations at similar or higher resolutions and can constrain the abundances of several neutron capture elements. We further show that high-resolution (R>20,000), low S/N spectra contain rich abundance information when modeled with full spectral fitting techniques. We suggest that, like exposure time calculators, CRLBs should be used when planning stellar spectroscopic observations. | Instrumentation | D |
| Lu Shen (University of Science and Technology of China) | Implications of the environments of radio-detected AGN in a complex proto-structure at z ~ 3.3 | Using new spectroscopic observations obtained from Keck/MOSFIRE and previous spectroscopic data obtained as part of the VIMOS-VLT Deep Survey (VVDS) and VUDS VIMOS Ultra-Deep Survey (VUDS), we revise the three-dimensional (3D) overdensity field in a protocluster at z = 3.3. The protocluster is embedded in a large scale overdensity structure which extends 25 x 21 x 80 comoving Mpc around the original detection and has an estimated total mass of 6x10^14 solar masses. This proto-structure contains three clear density peaks connected by filaments. In this talk, I will focus on two radio-detected AGN (RAGN) in this proto-structure, which have been confirmed by spectroscopic redshifts of their optical counterparts. The RAGN are hosted by the brightest and most massive galaxies, although their hosts show extreme differences in color, indicating that they are dominated by different stellar populations and have experienced different evolutionary paths. We find that the RAGN are offset from the densest regions, both in terms of the local overdensity and distance to their closest density peak. Our results suggest that such a complex and massive photo-structure would have been missed if the traditional method of small-area protocluster searches around very luminous RAGN had been used. | Extragalactic | D |
| Sunil Simha (UC Santa Cruz) | Unraveling the Cosmic Web: Constraints to the Dispersion Measure of the Host Galaxy of FRB 190608 | The Fast Radio Burst FRB190608 was localized by ASKAP to one of the prominent spiral arms of a nearby galaxy (z = 0.118) in the SDSS footprint. We used KCWI to constrain the component dispersion measures (DM) of the host galaxy. Analysis of the H_beta emission line combined with extinction constraints from the ratio of H_gamma/H_beta allowed us to estimate the expected H_alpha flux, which in turn allowed us to estimate a dispersion measure contribution from the host galaxy (DM_hg~½ DM_frb). Kinematic analysis of the host galaxy suggested an unperturbed environment at the FRB position. KCWI observations (a deep 1'x1' mosaic) also allowed us to supplement the extant spectroscopic data (from SDSS) for mapping foreground galaxy halos along the FRB sightline. We estimated the DM contribution of intervening halos assuming a model for the distribution of the virial gas within. We also modeled the gas in cosmic web filaments using the Monte Carlo Physarum Machine (MCPM; Burchett et al 2020) technique applied on data from the SDSS. Combining the cosmic and host DM estimates with a DM estimate of the Milky Way (Cordes & Lazio 2003), our work represents an end-to-end study of matter distribution along an FRB sightline. | Extragalactic | D |
| Christopher Snapp-Kolas (University of California, Riverside) | Keck/LRIS Rest-UV Spectra of Lensed Dwarf Galaxies at z~2 | We present Keck/LRIS spectra of more than 100 highly magnified, z~2 dwarf galaxies behind three lensing galaxy clusters. These data are complimented by MOSFIRE rest-frame optical spectra of nebular emission lines. Together, these data allow us to investigate the gas properties of galaxies with 7| Extragalactic | D | |
| Deno Stelter (UCSC/UCO) | Update on the SCALES Instrument Design | SCALES (Santa Cruz Array of Lenslets for Exoplanet Spectroscopy) is a 2-5 micron high-contrast lenslet integral-field spectrograph (IFS) driven by exoplanet characterization science requirements and will operate at WM Keck Observatory. SCALES is currently in its Preliminary Design phase, with plans to deploy to Keck II by ~2025. Its fully cryogenic optical train uses a custom silicon lenslet array, selectable coronagraphs, and dispersive prisms to carry out integral field spectroscopy over a 3.6 arcsec field of view at Keck with low (<300) spectral resolution. A secondary lenslet array feeds an image slicer module that allows for medium spectral resolution (5,000-10 000), which has not been available at the diffraction limit with a coronagraphic instrument before. Unlike previous IFS exoplanet instruments, SCALES is capable of characterizing cold exoplanet and brown dwarf atmospheres (<600 K) at bandpasses where these bodies emit most of their radiation while capturing relevant atmospheric molecular spectral features. | Instrumentation | D |
| Anthony Taylor (University of Wisconsin-Madison) | The Ultraluminous Lyman-alpha Luminosity Function at z>5 | We present the luminosity functions (LFs) for ultraluminous Lya emitting galaxies (LAEs) at z=5.7 and z=6.6, defining ultraluminous LAEs (ULLAEs) as galaxies with log L (Lya)>43.5 erg/s. Using a 30 sq. degree Subaru Hyper Suprime-Cam survey centered on the North Ecliptic Pole with both broadband (grizy) and narrowband (NB816 and NB921) components, we selected candidates based on color cuts (g',r',i'>26, NB921<23.5, and z'-NB921>1.3 at z=6.6), (g',r'>26, NB816<23.5, i'-NB816>1.3, and z'-NB816>1.3 at z=5.7) and visual inspections. We followed up 14 candidates spectroscopically with DEIMOS on Keck II, confirming 9 candidates as ULLAEs at z=6.6. We recently observed 16 candidates at z=5.7 with DEIMOS and confirming 12 as z=5.7 ULLAEs. We applied a comprehensive incompleteness correction to both LFs based on simulations of over 27 million test sources. We compare our recent z=6.6 ULLAE LF to our new z=5.7 ULLAE LF in order to determine the evolution of the ultraluminous LF near the end of the epoch of reionization. | Extragalactic | D |
| Michael Tucker (University of Hawai'i) | Nebular Spectra of Type Ia Supernovae Disfavor Non-Degenerate Companions | For many years the classic idea of a white dwarf accreting matter from a nearby star until approaching the Chandrasekhar mass then exploding was the prevailing theory for producing Type Ia supernovae. A consequence of this scenario is the donor star will be impacted by the high-speed ejecta shortly after the white dwarf explodes, liberating some of the outer envelope from the star. This stripped material is irradiated by gamma-rays from the radioactively-decaying ejecta and produces strong emission lines of H and He which are visible once the ejecta becomes optically thin. We present the largest compilation of nebular Type Ia supernova spectra, of which 20% were observed with the Keck telescopes, to search for these expected emission features. Our set of 110 supernovae have no detections of the expected H and He emission, placing a strict constraint of <6% for normal Type Ia supernovae forming through this classic progenitor system. Work is on-going to understand how these results apply to unusual Type Ia supernovae, such as those with irregularities in the early light curve, but these results strongly disfavor a nearby non-degenerate star at the time of explosion for the large majority of Type Ia supernovae. | Time-Domain | D |
| Taichi Uyama (Caltech IPAC/NExScI) | The early science result of Keck/NIRC2-PWFS High-contrast Imaging - SR21 disk | High-contrast imaging of exoplanets/protoplanetary-disks depends on wavefront sensing and correction at adaptive optics. Classically wavefront sensing was conducted at optical wavelength, which did not benefit high-contrast imaging of redder targets such as T Tauri star. Keck/NIRC2 has combined near-infrared (NIR) detector technology with the pyramid wavefront sensing (PWFS). In this talk we introduce the early result of science verification with NIR-PWFS by showing SR21 result. | Exoplanets | D |
| EXPERIMENTATION and THEORY: in cosmology, scientific theory gives us a tool to describe the universe that surrounds us. Hence, experimentation has the last word. In 1917, Albert Einstein inserted a correction factor, which he called the cosmological constant, into his general theory of relativity to force his equations to predict the stationary (that is, immutable) universe in which he believed. The cosmological constant is still used to determine values of Dark Energy together with Dark Matter in a completely random way in Theoretical Physics. We will not remember Edwin Powell Hubble for being a visionary. We will remember him for his commitment to science, cementing observational cosmology. TEST: Today it can be shown that there are Black Holes coinciding with the Theory of General Relativity. I assume that the future is to verify the behavior of matter in the Event Horizon. Relationship between mass and diameter of Supermassive and Ultramassive Black Holes (SMBH and UMBH). At the moment, the diameter of the event horizon is theoretically deduced from the Kerr metric. [1] [2] | Coffee and Cosmology | EXPERIMENTATION and THEORY: in cosmology, scientific theory gives us a tool to describe the universe that surrounds us. Hence, experimentation has the last word. In 1917, Albert Einstein inserted a correction factor, which he called the cosmological constant, into his general theory of relativity to force his equations to predict the stationary (that is, immutable) universe in which he believed. The cosmological constant is still used to determine values of Dark Energy together with Dark Matter in a completely random way in Theoretical Physics. We will not remember Edwin Powell Hubble for being a visionary. We will remember him for his commitment to science, cementing observational cosmology. TEST: Today it can be shown that there are Black Holes coinciding with the Theory of General Relativity. I assume that the future is to verify the behavior of matter in the Event Horizon. Relationship between mass and diameter of Supermassive and Ultramassive Black Holes (SMBH and UMBH). At the moment, the diameter of the event horizon is theoretically deduced from the Kerr metric. | Other | D |
| Kent Wallace (Jet Propulsion Laboratory) | Status of the KPIC Zernike Wavefront Sensor | The Zernike wavefront sensor (ZWFS) is a static, common-path, broad-band interferometer that is both easy to implement and very sensitive. It has been adopted for low-order wavefront sensing for the coronagraphic instrument on the Nancy Grace Roman Space Telescope. However, the ZWFS can serve as a general-purpose wavefront sensor as well. The tracking camera on the KPIC instrument enables both pupil plane and focal plane viewing, and is thus well suited for the Zernike sensor. Here, we discuss the Phase I implementation of the Zernike WFS as with a single, static phase shift in the focal plane phase mask. Preliminary results will be shown. We also discuss the plans for Phase II when this static Zernike will be upgraded to a vector Zernike focal plane mask. This new mask is fabricated using meta-surface optics whereby the focal plane is tiled with sub-wavelength features enabling arbitrary electric field phase and amplitude control at very fine spatial scales. This technology development will be described, as well as the increased capability this new device affords. The deployment on Keck allows us to mature wavefront sensing strategies for segmented aperture telescopes with starlight, and provides a unique opportunity to test this method. | Instrumentation | D |
| Nicole Wallack (Caltech) | Survey of Protoplanetary Disks Using the Keck/NIRC2 Vortex Coronagraph | Recent ALMA observations of protoplanetary disks in the millimeter continuum have shown a wide array of radial gaps, cavities, and spiral features. These sub-structures may be signposts for ongoing planet formation and therefore these systems are promising targets for direct imaging planet searches. To this end, we present initial results from a multi-year-long deep imaging survey in the L and M bands (3-5 microns) with the Keck/NIRC2 vortex coronagraph to search for young planets in over 50 disk systems with resolved features in the millimeter continuum. Utilizing the vortex coronagraph for deep observations allows for high sensitivity of faint sources at small angular separations (down to ~0".1), allowing us to place strong constraints on the masses of planets that could be in these systems. In addition to being able to place upper limits on the masses of planets that could be interacting with the dust in the disks to form the observed millimeter sub-structure, we are also able to characterize the micron-sized dust as seen in scattered light for a subset of these systems. Our large sample of systems also allows us to better constrain planet formation models and planetary accretion histories. | Exoplanets | D |
| Lauren Weiss (University of Hawai'i) | The Discovery of the Long-Period, Eccentric Planet Kepler-88 d and System Characterization with Radial Velocities and Photodynamical Analysis | We present the discovery of Kepler-88 d based on six years of radial velocity (RV) follow-up from Keck-HIRES. Kepler-88 has two previously identified planets. Kepler-88 b transits in the NASA Kepler photometry and has very large transit timing variations (TTVs). Nesvorný et al. performed a dynamical analysis of the TTVs to uniquely identify the orbital period and mass of the perturbing planet (Kepler-88 c), which was confirmed with RVs from the Observatoire de Haute-Provence. To fully explore the architecture of this system, we performed photodynamical modeling on the Kepler photometry combined with the RVs from Keck and OHP and stellar parameters from spectroscopy and Gaia. Planet d is not detectable in the photometry, and long-baseline RVs are needed to ascertain its presence. A photodynamical model simultaneously optimized to fit the RVs and Kepler photometry yields the most precise planet masses and orbital properties for b and c. The photodynamical solution also yields that planets b and c have low eccentricities and low mutual inclination, are apsidally anti-aligned, and have conjunctions on the same hemisphere of the star. Continued RV follow-up of systems with small planets will improve our understanding of the link between inner planetary system architectures and giant planets. | Exoplanets | D |
| Ruoyi Yin (University of California, Berkeley) | Binary Star Candidates at the Galactic Center | The stellar populations in the Galactic Center have promoted a series of discussions around velocity dispersion, stellar orbits within central parsecs, Supermassive Black Hole (SMBH) properties, and star formation. Recent studies suggest that the Galactic Center may house a non-negligible amount of binary stars, which could influence apparent orbits and velocities of stars if they are unresolved. We mainly utilize astrometric data for stars within the central half parsec of the Galactic Center from the W. M. Keck Observatory. The data were collected with two techniques: Speckle imaging (1995-2005) and Laser Guide Star Adaptive Optics imaging (2005-2017). From the previous study, there were 76 stars identified which showed significant accelerations not mainly caused by the Supermassive Black Hole. We start from this sample set and use MultiNest for model selection and constraints of binary parameters. An estimation for component masses is also derived based on binary parameters and isochrone conditions generated from SPISEA. | Galactic | D |
| James Wiley (UCSD) | He II Emission from the Circumgalactic Medium Around the High Redshift QSO 4c05.84 | We present recent Keck Cosmic Web Imager (KCWI) observations xof the high redshift quasar 4c05.84 (z=2.32) with a total integration time of 7 hours. These deep observations along with advanced data reduction techniques, such as scaled sky subtraction and PSF subtraction, allow us to study the extended quasar fluorescence emission in the circumgalactic medium (CGM). Ly-alpha emission extends 100 kpc surrounding 4c05.84 and we detect extended He II emission 20 kpc away from the quasar. These measurements show the clumpy, multiphase nature of the CGM and allow us to spatially resolve different ionization mechanisms. We present preliminary analysis of Ly-alpha, C IV, and He II and investigate the He II/Ly-alpha line ratio to study the ionization mechanisms and gas density distributions throughout the CGM. Studying He II provides tighter constraints on gas kinematics and accretion since Ly-alpha is generally optically thick and affected by complex radiative transfer. These high signal-to-noise He II observations are critical for measuring accurate inflow and outflow rates and tracing the formation and evolution of high redshift quasar host galaxies and their CGM. | Extragalactic | D |
