Highlights • We recorded neural activity using standard clinical ECoG grids, micro-ECoG grids, and intracortical micro-electrodes from human patients. • We found that non-penetrating micro-ECoG grid ...recorded neural activity at scales closer to penetrating intracortical micro-electrodes than clinical ECoG grids. • These novel micro-electrode technologies are enabling examination of cortical activity at the scale of cortical columns and could lead to improved diagnostics and neural prosthetic applications.
We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly α forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in ...large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, rd , from eight different samples and six measurements of the growth rate parameter, fσ8, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, Λ CDM model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization, under the same model, the BAO data provide nearly an order of magnitude improvement on curvature constraints relative to primary CMB constraints alone. Independent of distance measurements, the SDSS RSD data complement weak lensing measurements from the Dark Energy Survey (DES) in demonstrating a preference for a flat Λ CDM cosmological model when combined with Planck measurements. The combined BAO and RSD measurements indicate σ8 = 0.85 ± 0.03, implying a growth rate that is consistent with predictions from Planck temperature and polarization data and with General Relativity. When combining the results of SDSS BAO and RSD, Planck, Pantheon Type Ia supernovae (SNe Ia), and DES weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a Λ CDM model. Regardless of cosmological model, the precision on each of the three parameters, ΩΛ, H0, and σ8, remains at roughly 1%, showing changes of less than 0.6% in the central values between models. In a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint Ωk = −0.0022±0.0022. The dark energy constraints lead to w0 = −0.909 ± 0.081 and wa = −0.49 + 0.35−0.30, corresponding to an equation of state of wp = −1.018±0.032 at a pivot redshift zp = 0.29 and a Dark Energy Task Force Figure of Merit of 94. The inverse distance ladder measurement under this model yields H0 = 68.18±0.79 km s−1 Mpc−1, remaining in tension with several direct determination methods; the BAO data allow Hubble constant estimates that are robust against the assumption of the cosmological model. In addition, the BAO data allow estimates of H0 that are independent of the CMB data, with similar central values and precision under a Λ CDM model. Our most constraining combination of data gives the upper limit on the sum of neutrino masses at ∑mν< 0.115 eV (95% confidence). Finally, we consider the improvements in cosmology constraints over the last decade by comparing our results to a sample representative of the period 2000–2010. We compute the relative gain across the five dimensions spanned by w, Ωk, ∑mν, H0, and σ8 and find that the SDSS BAO and RSD data reduce the total posterior volume by a factor of 40 relative to the previous generation. Adding again the Planck, DES, and Pantheon SN Ia samples leads to an overall contraction in the five-dimensional posterior volume of 3 orders of magnitude.
The field of astronomy has entered an age of big data, and this being driven by dedicated telescopes and instruments built for the sole purpose of conducting broad surveys to catalog the night sky. ...The highly successful space-based Gaia mission has already cataloged the broadband colors, 3D locations, and trajectories for nearly 2 billion astronomical sources. The much anticipated Legacy Survey of Space and Time (LSST) is projected to catalog an order of magnitude more objects. Imaging surveys like these are providing an unprecedented number of sources available for spectroscopic followup. Spectroscopy reveals a wealth of astrophysical information that imaging alone cannot, but spectroscopy is an inherently slow process. To spectroscopically observe even a small fraction of what is currently available, observations need to be performed as quickly and efficiently as possible. Robotic fiber positioners are a relatively new technology designed to speed up spectroscopic data collection. The fifth iteration of the Sloan Digital Sky Survey (SDSS-V) has built a pair of instruments each with 500 robots carrying optical fibers for multi-object spectroscopy. The first instrument operates from Apache Point Observatory (APO) in New Mexico and saw first light in December 2021. The second instrument operates from Las Campanas Observatory (LCO) in Chile and saw first light in August 2022. These instruments are designed to perform a spectroscopic survey of 6 million sources in a survey duration of five years. Operationally these instruments are complex, and they are required to perform at very high precision. This work describes the mathematics, algorithms, analysis, and general calibration strategies we have developed to make these instruments operational. A robot's fundamental task is to position a 120 $\mu$m diameter optical fiber in the focal plane of the telescope to capture light from an astronomical source. A software package {\tt coordio} was developed to perform the calculations for determining where an astronomical source will land in the focal plane of the telescope and how a robot should be moved to collect light from that object. This package defines a series of coordinate systems and transforms and provides a computational backbone for many pieces of SDSS-V's survey operations and infrastructure codes. SDSS-V has chosen a spatially-agressive layout for the robotic fiber positioner array in which the physical workspace for a robot heavily overlaps with its neighbors. This layout grants more sky coverage to each robot but introduces a high risk of collision between robots during reconfiguration. A software package {\tt kaiju} was developed to compute safe paths for every robot while moving from one spectroscopic target to the next. This path planning algorithm was an important success for the project, and it allowed the instrument to realize its full potential in using every available robot in every spectroscopic exposure. When instrument assembly was completed, a period of lab testing and calibration was performed. A lab test camera was used to measure positions of back-lit optical fibers as robots were moved through many reconfigurations. From this process we derive a kinematic model unique to each robot for use in {\tt coordio} routines to accurately predict fiber locations. This period also served to test and tune {\tt kaiju} path planning parameters while operating the robot array at full scale, ensuring proper operation prior to shipping the instrument to the telescope. After lab calibration, each instrument was installed at the telescope where a Fiber View Camera (FVC) is used to measure and adjust fiber positions during array reconfiguration. A series of camera distortion models were derived to reach sufficient FVC measurement accuracy. On-sky instrument commissioning consisted of spectroscopic observations of Gaia sources using a telescope dither technique, which allowed us to estimate on-sky fiber position errors. Analysis of these data informed additional layers of instrument calibration which improved overall fiber positioning accuracy. The instrument at APO was commissioned first, and is currently placing robotic fibers with an RMS error of 21 $\mu$m relative to astrophysical sources in the focal plane. Spectroscopic targets are generally well centered within the 120 $\mu$m fiber aperture, and normal survey operations are proceeding. We expect that ongoing efforts will further improve survey efficiencies and fiber positioning performance with an end goal of limiting fiber placement error to $\sim$17 $\mu$m. The instrument at LCO is currently in the commissioning and science verification phase, but initial indications suggest that fiber throughput will be sufficient for achieving SDSS-V science goals. SDSS-V is the third project worldwide to successfully deploy a robotic fiber positioner instrument to conduct a multi-year spectroscopic survey, and several other projects of comparable scale are nearing deployment. Throughout the process of designing, building, and using these instruments, the we have developed a number of strategies and techniques that are directly applicable to contemporary instruments today. Robotic fiber positioner arrays will likely continue to grow in importance, and proposals for building instruments with tens of thousands of robots on large aperture telescopes are already in place. The solutions derived from today's robotic multi-object spectrosopic surveys will directly influence the feasibility and design of future projects.
Abstract
Robotic fiber positioner (RFP) arrays are becoming heavily adopted in wide-field massively multiplexed spectroscopic survey instruments. RFP arrays decrease nightly operational overheads ...through rapid reconfiguration between fields and exposures. In comparison to similar instruments, SDSS-V has selected a very dense RFP packing scheme where any point in a field is typically accessible to three or more robots. This design provides flexibility in target assignment. However, the task of collisionless trajectory planning is especially challenging. We present two multiagent distributed control strategies that are highly efficient and computationally inexpensive for determining collision-free paths for RFPs in heavily overlapping workspaces. We demonstrate that a reconfiguration path between two arbitrary robot configurations can be efficiently found if a “folded” state, in which all robot arms are retracted and aligned in a lattice-like orientation, is inserted between the initial and final states. Although developed for SDSS-V, the approach we describe is generic and thus applicable to a wide range of RFP designs and layouts. Robotic fiber positioner technology continues to advance rapidly, and in the near future ultra-densely packed RFP designs may be feasible. Our algorithms are especially capable in routing paths in very crowded environments, where we see efficient results even in regimes significantly more crowded than the SDSS-V RFP design.
By selecting astrometric and photometric data from the Sloan Digital Sky Survey (SDSS), the Lepine & Shara Proper Motion North Catalog (LSPM-North), the Two Micron All Sky Survey (2MASS), and the ...USNO-B1.0 catalog, we use a succession of methods to isolate white dwarf (WD) candidates for follow-up spectroscopy. Our methods include reduced proper motion diagram cuts, color cuts, and atmospheric model adherence. We present spectroscopy of 26 WDs obtained from the CTIO 4 m and APO 3.5 m telescopes. Additionally, we confirm 28 WDs with spectra available in the SDSS DR7 database but unpublished elsewhere, presenting a total of 54 WDs. We label one of these as a recovered WD while the remaining 53 are new discoveries. We determine physical parameters and estimate distances based on atmospheric model analyses. Three new WDs are modeled to lie within 25 pc. Two additional WDs are confirmed to be metal-polluted (DAZ). Follow-up time series photometry confirms another object to be a pulsating ZZ Ceti WD.
We present the Sloan Digital Sky Survey V (SDSS-V) Local Volume Mapper (LVM). The LVM is an integral-field spectroscopic survey of the Milky Way, Magellanic Clouds, and of a sample of local volume ...galaxies, connecting resolved pc-scale individual sources of feedback to kpc-scale ionized interstellar medium (ISM) properties. The 4-year survey covers the southern Milky Way disk at spatial resolutions of 0.05 to 1 pc, the Magellanic Clouds at 10 pc resolution, and nearby large galaxies at larger scales totaling \(>4300\) square degrees of sky, and more than 55M spectra. It utilizes a new facility of alt-alt mounted siderostats feeding 16 cm refractive telescopes, lenslet-coupled fiber-optics, and spectrographs covering 3600-9800A at R ~ 4000. The ultra-wide field IFU has a diameter of 0.5 degrees with 1801 hexagonally packed fibers of 35.3 arcsec apertures. The siderostats allow for a completely stationary fiber system, avoiding instability of the line spread function seen in traditional fiber feeds. Scientifically, LVM resolves the regions where energy, momentum, and chemical elements are injected into the ISM at the scale of gas clouds, while simultaneously charting where energy is being dissipated (via cooling, shocks, turbulence, bulk flows, etc.) to global scales. This combined local and global view enables us to constrain physical processes regulating how stellar feedback operates and couples to galactic kinematics and disk-scale structures, such as the bar and spiral arms, as well as gas in- and out-flows.
Robotic fiber positioner (RFP) arrays are becoming heavily adopted in wide field massively multiplexed spectroscopic survey instruments. RFP arrays decrease nightly operational overheads through ...rapid reconfiguration between fields and exposures. In comparison to similar instruments, SDSS-V has selected a very dense RFP packing scheme where any point in a field is typically accessible to three or more robots. This design provides flexibility in target assignment. However, the task of collision-less trajectory planning is especially challenging. We present two multi-agent distributed control strategies that are highly efficient and computationally inexpensive for determining collision-free paths for RFPs in heavily overlapping workspaces. We demonstrate that a reconfiguration path between two arbitrary robot configurations can be efficiently found if "folded" state, in which all robot arms are retracted and aligned in a lattice-like orientation, is inserted between the initial and final states. Although developed for SDSS-V, the approach we describe is generic and so applicable to a wide range of RFP designs and layouts. Robotic fiber positioner technology continues to advance rapidly, and in the near future ultra-densely packed RFP designs may be feasible. Our algorithms are especially capable in routing paths in very crowded environments, where we see efficient results even in regimes significantly more crowded than the SDSS-V RFP design.
Digital planetariums can provide a broader range of educational experiences than the more classical planetariums that use star-balls. This is because of their ability to project images, content from ...current research and the 3D distribution of the stars and galaxies. While there are hundreds of planetariums in the country the reason that few of these are full digital is the cost. In collaboration with Microsoft Research (MSR) we have developed a way to digitize existing planetariums for approximately \$40,000 using software freely available. We describe here how off the shelf equipment, together with MSR's WorldWide Telescope client can provide a rich and truly interactive experience. This will enable students and the public to pan though multi-wavelength full-sky scientific data sets, explore 3d visualizations of our Solar System (including trajectories of millions of minor planets), near-by stars, and the SDSS galaxy catalog.
By selecting astrometric and photometric data from the Sloan Digital Sky Survey (SDSS), the L{é}pine & Shara Proper Motion North Catalog (LSPM-North), the Two Micron All Sky Survey (2MASS), and the ...USNO-B1.0 catalog, we use a succession of methods to isolate white dwarf candidates for follow-up spectroscopy. Our methods include: reduced proper motion diagram cuts, color cuts, and atmospheric model adherence. We present spectroscopy of 26 white dwarfs obtained from the CTIO 4m and APO 3.5m telescopes. Additionally, we confirm 28 white dwarfs with spectra available in the SDSS DR7 database but unpublished elsewhere, presenting a total of 54 WDs. We label one of these as a recovered WD while the remaining 53 are new discoveries. We determine physical parameters and estimate distances based on atmospheric model analyses. Three new white dwarfs are modeled to lie within 25 pc. Two additional white dwarfs are confirmed to be metal-polluted (DAZ). Follow-up time series photometry confirms another object to be a pulsating ZZ Ceti white dwarf.
SDSS-V will be an all-sky, multi-epoch spectroscopic survey of over six million objects. It is designed to decode the history of the Milky Way, trace the emergence of the chemical elements, reveal ...the inner workings of stars, and investigate the origin of planets. It will also create an integral-field spectroscopic map of the gas in the Galaxy and the Local Group that is 1,000x larger than the current state of the art and at high enough spatial resolution to reveal the self-regulation mechanisms of galactic ecosystems. SDSS-V will pioneer systematic, spectroscopic monitoring across the whole sky, revealing changes on timescales from 20 minutes to 20 years. The survey will thus track the flickers, flares, and radical transformations of the most luminous persistent objects in the universe: massive black holes growing at the centers of galaxies. The scope and flexibility of SDSS-V will be unique among extant and future spectroscopic surveys: it is all-sky, with matched survey infrastructures in both hemispheres; it provides near-IR and optical multi-object fiber spectroscopy that is rapidly reconfigurable to serve high target densities, targets of opportunity, and time-domain monitoring; and it provides optical, ultra-wide-field integral field spectroscopy. SDSS-V, with its programs anticipated to start in 2020, will be well-timed to multiply the scientific output from major space missions (e.g., TESS, Gaia, eROSITA) and ground-based projects. SDSS-V builds on the 25-year heritage of SDSS's advances in data analysis, collaboration infrastructure, and product deliverables. The project is now refining its science scope, optimizing the survey strategies, and developing new hardware that builds on the SDSS-IV infrastructure. We present here an overview of the current state of these developments as we seek to build our worldwide consortium of institutional and individual members.
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