Ultrastable environment control for the NEID spectrometer: design and performance demonstration

Two key areas of emphasis in contemporary experimental exoplanet science are the detailed characterization of transiting terrestrial planets and the search for Earth analog planets to be targeted by future imaging missions. Both of these pursuits are dependent on an order-of-magnitude improvement in the measurement of stellar radial velocities (RV), setting a requirement on single-measurement instrumental uncertainty of order 10 cm/s. Achieving such extraordinary precision on a high-resolution spectrometer requires thermomechanically stabilizing the instrument to unprecedented levels. We describe the environment control system (ECS) of the NEID spectrometer, which will be commissioned on the 3.5-m WIYN Telescope at Kitt Peak National Observatory in 2019, and has a performance specification of on-sky RV precision <50 cm/s. Because NEID's optical table and mounts are made from aluminum, which has a high coefficient of thermal expansion, sub-milliKelvin temperature control is especially critical. NEID inherits its ECS from that of the Habitable-Zone Planet Finder (HPF), but with modifications for improved performance and operation near room temperature. Our full-system stability test shows the NEID system exceeds the already impressive performance of HPF, maintaining vacuum pressures below 10(-6) Torr and a root mean square (RMS) temperature stability better than 0.4 mK over 30 days. Our ECS design is fully open-source; the design of our temperature-controlled vacuum chamber has already been made public, and here we release the electrical schematics for our custom temperature monitoring and control system. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)JPL [1547612]; Center for Exoplanets and Habitable Worlds; Pennsylvania State University; Eberly College of Science; Pennsylvania Space Grant Consortium; NASA through the Sagan Fellowship Program by the NASA Exoplanet Science Institute; NASA Headquarters under the NASA Earth and Space Science Fellowship Program [NNX16AO28H]; NSF [AST-1006676, AST-1126413, AST-1310885]; NASA Astrobiology Institute (NAI) [NNA09DA76A]; Penn State Astrobiology Research CenterThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Probing conditions at ionized/molecular gas interfaces with high resolution near-infrared spectroscopy

Regions of star formation and star death in our Galaxy trace the cycle of gas and dust in the interstellar medium (ISM). Gas in dense molecular clouds collapses to form stars, and stars at the end of their lives return the gas that made up their outer layers back out into the Galaxy. Hot stars generate copious amounts of ultraviolet photons which interact with the surrounding medium and dominate the energetics, ionization state, and chemistry of the gas. The interface where molecular gas is being dissociated into neutral atomic gas by far-UV photons from a nearby hot source is called a photodissociation or photon-dominated region (PDR). PDRs are found primarily in star forming regions where O and B stars serve as the source of UV photons, and in planetary nebulae where the hot core of the dying star acts as the UV source. The main target of this dissertation is molecular hydrogen (H₂), the most abundant molecule in the Universe, made from hydrogen formed during the Big Bang. H₂ makes up the overwhelming majority of molecules found in the ISM and in PDRs. Far-UV radiation absorbed by H₂ will excite an electron in the molecule. The molecule then either dissociates (~10% of the time; Field et al. 1966) or decays into excited ro- tational and vibrational (“rovibrational”) levels of the electronic ground state. These excited rovibrational levels then decay via a radiative cascade to the ground rovibrational state (v = 0, J = 0), giving rise to a large number of transitions observable in emission from the mid-IR to the optical (Black & van Dishoeck, 1987). These transitions provide an excellent probe of the excitation and conditions within the gas. These transitions are also observed in warm H₂, such as in shocks, where collisions excite H₂ to higher rovibrational levels. High resolution near-infrared spectroscopy, with its ability to see through dust, and avoid telluric absorption and emission, serves as an effective tool to detect emission from ions, atoms, and molecules within PDRs. The Immersion Grating INfrared Spectrometer (IGRINS), with a high spectral resolution of ~45,000 and simultaneous wavelength coverage of the near infrared H and K bands (1.45–2.45 μm) has proven to be an excellent instrument for such studies. Over 200 H₂ rovibrational transitions are observable within the wavelength coverage of IGRINS. In this dissertation, we use IGRINS on the 2.7m telescope at McDonald Observatory, to observe a variety of PDRs in the ISM and use the rovibrationally excited H₂ to probe the physical conditions within them. We fit our data with grids of Cloudy models (Ferland et al., 2013), which reproduce the observed H₂ rovibrational level populations, to determine the physical parameters in the gas such as temperature, density, and UV field intensity. This dissertation is split into five chapters. In the first chapter, we introduce our science questions and explain our observations, data processing, and how to analyze H₂ emission. In the second chapter, we present a deep near-infrared spectrum of the Orion Bar PDR. In the third chapter, we analyze several other PDRs in star forming regions in a similar fashion to the Orion Bar, finding significant differences in their H₂ excitation and conditions. In the fourth chapter, we use the high spectral resolution of IGRINS to reveal kinematically and energetically distinct components of H₂ emission in three planetary nebulae (M 1-11, Vy 2-2, and Hen 2-459) consisting of UV-excited (PDR) H₂ and red- and blue-shifted thermal H₂ “bullets” that likely represent shocked molecular gas that is distinct from the UV-excited PDR components. In the fifth chapter, we summarize this dissertation, discuss the broader implications of this work, and suggest future directions for near-IR ISM research.Astronom

Time Series Modeling of Baseball Performance​

The 162 game long Major League Baseball season provides ample time for a player’s performance to vary and trend in different directions. Managers must set daily rosters for their teams, using past performance to help make decisions. But which prior performance periods tell us the most about upcoming performance? To answer this, it\u27s helpful to view a player’s future performance, for any given statistic, as a function of his performance in previous playing periods (e.g. previous game, previous week, previous year, etc.). In this on-going research project, we consider two approaches to predicting future performance from the past. In the first, we build a probability mass function for each of a set of discrete, disjoint past time periods and we use Expectation Maximization to learn the appropriate weights for each period to best predict future outcomes. In our second approach, we predict a player\u27s performance in the next game based on all previous history using a recurrent neural network

Neutron-Capture elements in planetary nebulae: first detections of near-Infrared [Te III] and [Br V] emission lines

We have identified two new near-infrared emission lines in the spectra of planetary nebulae (PNe) arising from heavy elements produced by neutron capture reactions: [Te III] 2.1019 $\mu$m and [Br V] 1.6429 $\mu$m. [Te III] was detected in both NGC 7027 and IC 418, while [Br V] was seen in NGC 7027. The observations were obtained with the medium-resolution spectrograph EMIR on the 10.4m Gran Telescopio Canarias at La Palma, and with the high-resolution spectrograph IGRINS on the 2.7m Harlan J. Smith telescope at McDonald Observatory. New calculations of atomic data for these ions, specifically A-values and collision strengths, are presented and used to derive ionic abundances of Te$^{2+}$ and Br$^{4+}$. We also derive ionic abundances of other neutron-capture elements detected in the near-infrared spectra, and estimate total elemental abundances of Se, Br, Kr, Rb, and Te after correcting for unobserved ions. Comparison of our derived enrichments to theoretical predictions from AGB evolutionary models shows reasonable agreement for solar metallicity progenitor stars of $\sim$2 - 4 M$_{\odot}$. The spectrally-isolated [Br V] 1.6429 $\mu$m line has advantages for determining nebular Br abundances over optical [Br III] emission lines that can be blended with other features. Finally, measurements of Te are of special interest because this element lies beyond the first peak of the s-process, and thus provides new leverage on the abundance pattern of trans-iron species produced by AGB stars.Comment: 9 pages, 1 figure, 4 tables. Accepted for publication in ApJ Letter

Combining Different Motivation and Cognitive Supports in Undergraduate Biology in Different Contexts: Lessons Learned

Researchers acknowledge that students’ learning and achievement requires both effective cognition and the motivation to apply it. In addition, both cognition and motivation are multidimensional, each involving different processes that may be less or more salient in different contexts. However, most basic research and intervention studies focus on either cognition OR motivation, and commonly only target a single process. We designed an intervention to investigate the role of different combinations of cognitive and motivational supports in first-year undergraduate introductory biology courses. We sought an online delivery approach with minimal burden on the instructor that can accompany any such course. Building on prior research, we selected four types of cognitive supports and three types of motivational supports. Cognitive supports: Priming Prior Knowledge, Demonstrating Worked Examples, Instructing Study Strategies and Scaffolding Organization of Lectures. Motivational supports: Self-Efficacy Promoting Feedback, Value Enhancement Through Relevance Writing, and Perceived Cost Alleviation Through Persuasion. The intervention study was designed to test the effects of different combinations of these cognition and motivation supports. Initial development began in 2015-2016 with post-iterative experiments in 2017. Overall, there were 3,092 undergraduate student participants, tested in 10 studies at 3 universities over 4 years. Students were randomly assigned to either a no-treatment control condition or one of 17 combinations of cognition and motivation intervention modules delivered via the Internet, each over the course of a semester. A meta-analysis of the overall effect of all interventions on grades across the 10 studies was positive (g = .30), with significant moderation of fidelity (i.e., students’ access; g = .24) and research phase (stronger effect in later administrations; g = .26). Moreover, certain combinations had little effect across administrations (e.g., any combination with Priming Prior Knowledge). However, the development and testing process also pointed to contextual and situational factors that influenced the effect of mostly effective interventions. For example, in one institution, Scaffolding Organization of Lectures through thematically segmenting lecture videos had the unintended consequence of students stopping lecture attendance. Or, in one institution but not in others, students “crammed” on the supports, which undermined the effect and required modifying the intervention in order to regulate timely access in that institution. Additionally, for yet to be explored reasons, successful combinations of modules were more effective in certain administrations in some institutions than in others. Finally, in certain administrations, there were unanticipated direct effects of motivational modules on cognitive biological reasoning, and cognitive modules on motivational beliefs The current study demonstrated that, when aggregated across context, time, and participants, a “hands-off” administration of a combination of certain cognitive and motivational supports can meaningfully improve undergraduate students’ motivation, biological reasoning, and course grades, with a stronger effect than a cognitive or motivation intervention alone. In addition, however, the findings point to important contextual as well as potentially unpredictable factors as moderating the effect of such interventions. “Evidence-based practice” might need to be considered a “first-step” in a systematic design process of catering any intervention to the particular educational context

Combined SRL-Based Cognitive-Motivational Modules Increase Undergraduate Biology Grades

Students’ success in undergraduate STEM courses requires effective study strategies, but also the motivation to enact them, drawing on two key tenets of Self-Regulated Learning. Interventions designed to promote students’ achievement and retention in STEM have commonly focused on either cognition or motivation. Building on Pintrich’s (2000) SRL framework, we iteratively-developed and tested the effect of different combinations of one of four cognition-focused with one of three motivation-focused intervention modules. Initial development took place in 2015-2016 and post-iterative experiments occurred in 2017. Participants were 3,092 undergraduate introductory biology students tested in 10 studies at 3 universities over 4 academic years. They were randomly assigned to either a no-treatment control condition or one of 17 conditions involving either a cognition, motivation, or a combined cognition and motivation intervention module, that was delivered via the Internet over the course of an entire semester. Course grades were provided by the instructor. We used a meta-analysis to capture the overall effect of students’ access to the interventions on grades, and to test whether differences across experiments such as fall versus spring implementation changed the effect size for the interventions. Averaging across all 10 studies, the combined intervention had an effect of g = .30. All 10 moderators were significant: cognitive+motivational versus either one alone, timely access to the intervention, iterative development phase, type of cognitive or type of motivation module, the specific cognitive-motivation combination, university, academic year, semester, first versus second semester of biology, and course content. We conclude that interventions based in SRL theory and delivered online can meaningfully improve undergraduate students’ course grades (corresponding to 6.6 percentage points on final course grade), with minimal extra work for instructors. However, these effects were dependent on a variety of contextual factors