Metals AM Design for Manufacturing

We are looking to improve upon the current post processing techniques for metal additive manufacturing (AM). This project, sponsored by Lawrence Livermore National Laboratory (LLNL), will investigate ways to improve the design of stainless steel 316 parts made by AM, and how these designs will help with post processing techniques. We hope that the findings regarding stainless steel will apply to to improve the AM and post processing handshake in general. In particular, the project will focus on including different features in different basic part design shapes to aid in fixturing and post-processing of the part made by AM. This will largely focus on including features for kinematic mounting that can be used to fixture the part in a machine for post processing or for inspection. Kinematic mounts will be added to parts that are to be milled and extension will be added to parts processed by the mill. This type of mounting can improve the accuracy of the part orientation in the machines as well as making positioning of the part more easily repeatable. Various ways of incorporating these mounts into the part design will be tested with post-processing to determine the most beneficial configuration. The information gathered will be used to create a design guide for LLNL to use with their AM processes when determining which type of mounting system would be the most useful in each situation

Detector Characterization of a Near-Infrared Discrete Avalanche Photodiode 5x5 Array for Astrophysical Observations

We present detector characterization of a state-of-the-art near-infrared (950nm - 1650 nm) Discrete Avalanche Photodiode detector (NIRDAPD) 5x5 array. We designed an experimental setup to characterize the NIRDAPD dark count rate, photon detection efficiency (PDE), and non-linearity. The NIRDAPD array was illuminated using a 1050 nm light-emitting diode (LED) as well as 980 nm, 1310 nm, and 1550 nm laser diodes. We find a dark count rate of 3.3x10$^6$ cps, saturation at 1.2x10$^8$ photons per second, a photon detection efficiency of 14.8% at 1050 nm, and pulse detection at 1 GHz. We characterized this NIRDAPD array for a future astrophysical program that will search for technosignatures and other fast (>1 Ghz) astrophysical transients as part of the Pulsed All-sky Near-infrared Optical Search for Extraterrestrial Intelligence (PANOSETI) project. The PANOSETI program will consist of an all-sky optical (350 - 800 nm) observatory capable of observing the entire northern hemisphere instantaneously and a wide-field NIR (950 - 1650 nm) component capable of drift scanning the entire sky in 230 clear nights. PANOSETI aims to be the first wide-field fast-time response near-infrared transient search.Comment: 8 pages, 7 figures, 1 tabl

A local baseline of the black hole mass scaling relations for active galaxies. III. The MBH-σ relation

We create a baseline of the black hole (BH) mass ()—stellar-velocity dispersion (σ) relation for active galaxies, using a sample of 66 local () Seyfert-1 galaxies, selected from the Sloan Digital Sky Survey (SDSS). Analysis of SDSS images yields AGN luminosities free of host-galaxy contamination, and morphological classification. 51/66 galaxies have spiral morphology. Out of these, 28 bulges have Sérsic index and are considered candidate pseudo-bulges, with eight being definite pseudo-bulges based on multiple classification criteria met. Only 4/66 galaxies show signs of interaction/merging. High signal-to-noise ratio Keck spectra provide the width of the broad Hβ emission line free of Fe ii emission and stellar absorption. AGN luminosity and Hβ line widths are used to estimate . The Keck-based spatially resolved kinematics is used to determine stellar-velocity dispersion within the spheroid effective radius (). We find that σ can vary on average by up to 40% across definitions commonly used in the literature, emphasizing the importance of using self-consistent definitions in comparisons and evolutionary studies. The –σ relation for our Seyfert-1 galaxy sample has the same intercept and scatter as that of reverberation-mapped AGNs as well as that of quiescent galaxies, consistent with the hypothesis that our single epoch estimator and sample selection function do not introduce significant biases. Barred galaxies, merging galaxies, and those hosting pseudo-bulges do not represent outliers in the –σ relation. This is in contrast with previous work, although no firm conclusion can be drawn on this matter due to the small sample size and limited resolution of the SDSS images

Panoramic optical and near-infrared SETI instrument: prototype design and testing

The Pulsed All-sky Near-infrared Optical Search for ExtraTerrestrial Intelligence (PANOSETI) is an instrument program that aims to search for fast transient signals (nano-second to seconds) of artificial or astrophysical origin. The PANOSETI instrument objective is to sample the entire observable sky during all observable time at optical and near-infrared wavelengths over 300 - 1650 nm$^1$. The PANOSETI instrument is designed with a number of modular telescope units using Fresnel lenses ($\sim$0.5m) arranged on two geodesic domes in order to maximize sky coverage$^2$. We present the prototype design and tests of these modular Fresnel telescope units. This consists of the design of mechanical components such as the lens mounting and module frame. One of the most important goals of the modules is to maintain the characteristics of the Fresnel lens under a variety of operating conditions. We discuss how we account for a range of operating temperatures, humidity, and module orientations in our design in order to minimize undesirable changes to our focal length or angular resolution.Comment: 12 pages, 8 figures, 1 tabl

Broad H\u3cem\u3eβ\u3c/em\u3e emission-line variability in a sample of 102 local active galaxies

A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses MBH \u3e 107M⊙ was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate MBH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (~66%) of the objects, resulting in a Seyfert-type change for ~38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (~3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies

Studying the [OIII]λ\lambda5007A emission-line width in a sample of ∼\sim80 local active galaxies: A surrogate for σ⋆\sigma_{\star}?

For a sample of $\sim$80 local ($0.02 \leq z \leq 0.1$) Seyfert-1 galaxies with high-quality long-slit Keck spectra and spatially-resolved stellar-velocity dispersion ($\sigma_{\star}$) measurements, we study the profile of the [OIII]$\lambda$5007A emission line to test the validity of using its width as a surrogate for $\sigma_{\star}$. Such an approach has often been used in the literature, since it is difficult to measure $\sigma_{\star}$ for type-1 active galactic nuclei (AGNs) due to the AGN continuum outshining the stellar-absorption lines. Fitting the [OIII] line with a single Gaussian or Gauss-Hermite polynomials overestimates $\sigma_{\star}$ by 50-100%. When line asymmetries from non-gravitational gas motion are excluded in a double Gaussian fit, the average ratio between the core [OIII] width ($\sigma_{\rm {[OIII],D}}$) and $\sigma_{\star}$ is $\sim$1, but with individual data points off by up to a factor of two. The resulting black-hole-mass-$\sigma_{\rm {[OIII],D}}$ relation scatters around that of quiescent galaxies and reverberation-mapped AGNs. However, a direct comparison between $\sigma_{\star}$ and $\sigma_{\rm {[OIII],D}}$ shows no close correlation, only that both quantities have the same range, average and standard deviation, probably because they feel the same gravitational potential. The large scatter is likely due to the fact that line profiles are a luminosity-weighted average, dependent on the light distribution and underlying kinematic field. Within the range probed by our sample (80-260 km s$^{-1}$), our results strongly caution against the use of [OIII] width as a surrogate for $\sigma_{\star}$ on an individual basis. Even though our sample consists of radio-quiet AGNs, FIRST radio-detected objects have, on average, a $\sim$10% larger [OIII] core width.Comment: 15 pages, 10 figures, 6 tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Societ