We present a systematic study of the HNCO, C18O,13CS, and C34S emission toward 13 selected molecular clouds in the Galactic center region. The molecular emission in these positions is used as a template of the different physical and chemical processes claimed to be dominant in the circumnuclear molecular gas of galaxies. The relative abundance of HNCO shows a variation of more than a factor of 20 among the observed sources. The HNCO/13CS abundance ratio is highly contrasted (up to a factor of 30) between the shielded molecular clouds mostly affected by shocks, where HNCO is released to gas phase from grain mantles, and those pervaded by an intense UV radiation field, where HNCO is photodissociated and CS production favored via ion reactions. We propose the relative HNCO to CS abundance ratio as a highly contrasted diagnostic tool to distinguish between the influence of shocks and/or the radiation field in the nuclear regions of galaxies and their relation to the evolutionary state of their nuclear star formation bursts.

http://iopscience.iop.org/article/10.1086/533409/pdf

Tracing Shocks and Photodissociation in the Galactic Center Region

Nanomanufacturing involves scaled-up, reliable, and cost-effective manufacturing of nanoscale materials, structures, devices, and systems. Nanomanufacturing methods can be classified into top-down and bottom-up approaches, including additive, subtractive, and replication/mass conservation processes. These include a cluster of various techniques such as nanomachining, nanofabrication, and nanometrology to produce nanotechnology components and conduct evaluation. This paper mainly focuses on the manufacturing methods for complex shapes or structures, such as textures on curves and hierarchical structures, and outlines the research perspectives and the current application status of nanomanufacturing fundamentals and key technologies.

https://orbit.dtu.dk/files/138286168/1_s2.0_S0007850617301439_main.pdf

Nanomanufacturing—Perspective and applications

Context. The isocyanic acid (HNCO) has an extended distribution in the centers of the Milky Way and the spiral galaxy IC342. Based on both the morphology of the emission and the HNCO abundance with respect to H2, several authors hypothesized that HNCO could be a good tracer of interstellar shocks. Aims. We test this hypothesis by observing a well-known Galactic source whose chemistry is dominated by shocks. Methods. We observed several transitions of HNCO towards L1157-mm and two positions (B1 and B2) in the blue lobe of the molecular outflow. Results. The HNCO line profiles exhibit the same characteristics as other well-known shock tracers such as CH3OH, H2CO, SO, or SO2. The three molecules HNCO, SO2, and OCS are the only ones detected so far whose emission is more intense in B2 than in B1, making these species valuable probes of chemical differences along the outflow. The HNCO abundance with respect to H2 is (0.4–1.8) × 10 −8 in B1 and (0.3–1) × 10 −7 in B2. These abundances are the highest ever measured, and imply an increment with respect to L1157-mm of up to a factor of 83, demonstrating that this molecule is a good shock tracer. Conclusions. we demonstrate that shocks can produce the HNCO abundance measured in galactic nuclei and even higher values. We propose that the gas phase abundance of HNCO is produced by both grain mantle erosion by the shock waves and by neutral-neutral reactions in gas phase involving CN and O2. The observed anticorrelation between CN and HNCO fluxes supports this scenario. The observed similarities between the HNCO emission and sulfur-bearing molecules may be caused by formation pathways that also involve O2.

/pdf/hnco-enhancement-by-shocks-in-the-l1157-molecular-outflow-4kfv5wyimz.pdf

HNCO enhancement by shocks in the L1157 molecular outflow

Context. Sagittarius B2 is one of the most massive and luminous star-forming regions in the Galaxy and shows a very rich chemistry and physical conditions similar to those in much more distant extragalactic starbursts. Aims. We present large-scale far-infrared/submillimeter photometric images and broadband spectroscopic maps taken with the PACS and SPIRE instruments onboard Herschel. Methods. High angular resolution dust images (complemented with Spitzer MIPS 24 μm images) as well as atomic and molecular spectral maps were made and analyzed in order to constrain the dust properties, the gas physical conditions, and the chemical content of this unique region. Results. The spectra towards the Sagittarius B2 star-forming cores, B2(M) and B2(N), are characterized by strong CO line emission (from J = 4 to 16), emission lines from high-density tracers (HCN, HCO + ,a nd H 2S), [N ii] 205μm emission from ionized gas, and a large number of absorption lines from light hydride molecules (OH + ,H 2O + ,H 2O, CH + ,C H, SH + , HF, NH, NH2 ,a nd NH 3). The rotational population diagrams of CO suggest the presence of two different gas temperature components: an extended warm component with Trot ∼ 50–100 K, which is associated with the extended envelope, and a hotter component at Trot ∼ 200 K and Trot ∼ 300 K, which is only seen towards the B2(M) and B2(N) cores, respectively. As observed in other Galactic center clouds, such gas temperatures are significantly higher than the dust temperatures inferred from photometric images (Td � 20–30 K). We ,

/pdf/herschel-observations-of-the-sagittarius-b2-cores-hydrides-3lvuqjppf3.pdf

Herschel observations of the Sagittarius B2 cores: Hydrides, warm CO, and cold dust

We highlight three emerging NASA optical technologies that enhance our ability to remotely sense , analyze, and explore ocean worlds – FluidCam and fluid lensing, MiDAR, and NeMO-Net. Fluid lensing is the first remote sensing technology capable of imaging through ocean waves without distortions in 3D at sub-cm resolutions. Fluid lensing and the purpose-built FluidCam CubeSat instruments have been used to provide refraction-corrected 3D multispectral imagery of shallow marine systems from unmanned aerial vehicles (UAVs). Results from repeat 2013 and 2016 airborne fluid lensing campaigns over coral reefs in American Samoa present a promising new tool for monitoring fine-scale ecological dynamics in shallow aquatic systems tens of square kilometers in area. MiDAR is a recently-patented active multispectral remote sensing and optical communications instrument which evolved from FluidCam. MiDAR is being tested on UAVs and autonomous underwater vehicles (AUVs) to remotely sense living and nonliving structures in light-limited and analog planetary science environments. MiDAR illuminates targets with high-intensity narrowband structured optical radiation to measure an object’s spectral reflectance while simultaneously transmitting data. MiDAR is capable of remotely sensing reflectance at fine spatial and temporal scales, with a signal-to-noise ratio 10-103 times higher than passive airborne and spaceborne remote sensing systems, enabling high-framerate multispectral sensing across the ultraviolet, visible, and near-infrared spectrum. Preliminary results from a 2018 mission to Guam show encouraging applications of MiDAR to imaging coral from airborne and underwater platforms whilst transmitting data across the air-water interface. Finally, we share NeMO-Net, the Neural Multi-Modal Observation & Training Network for Global Coral Reef Assessment. NeMO-Net is a machine learning technology under development that exploits high-resolution data from FluidCam and MiDAR for augmentation of low-resolution airborne and satellite remote sensing. NeMO-Net is intended to harmonize the growing diversity of 2D and 3D remote sensing with in situ data into a single open-source platform for assessing shallow marine ecosystems globally using active learning for citizen-science based training. Preliminary results from four-class coral classification have an accuracy of 94.4%. Together, these maturing technologies present promising scalable, practical, and cost-efficient innovations that address current observational and technological challenges in optical sensing of marine systems.

/pdf/next-generation-optical-sensing-technologies-for-exploring-1l1tgdvkic.pdf

Next-Generation Optical Sensing Technologies for Exploring Ocean Worlds—NASA FluidCam, MiDAR, and NeMO-Net

Freeform mirrors can be readily fabricated by a single point diamond turning (SPDT) machine. However, this machining process often leaves mid-frequency errors (MFEs) that generate undesirable diffraction effects and stray light. In this work, we propose a novel thin electroless nickel plating procedure to remove MFE on freeform surfaces. The proposed procedure has a distinct advantage over a typical thick plating method in that the machining process can be endlessly repeated until the designed mirror surface is obtained. This is of great importance because the sophisticated surface of a freeform mirror cannot be optimized by a typical SPDT machining process, which can be repeated only several times before the limited thickness of the nickel plating is consumed. We will also describe the baking process of a plated mirror to improve the hardness of the mirror surface, which is crucial for minimizing the degradation of that mirror surface that occurs during the polishing process. During the whole proposed process, the changes in surface figures and textures are monitored and cross checked by two different types of measurements, as well as by an interference pattern test. The experimental results indicate that the proposed thin electroless nickel plating procedure is very simple but powerful for removing MFEs on freeform mirror surfaces.

Fabrication of electroless nickel plated aluminum freeform mirror for an infrared off-axis telescope.

http://iopscience.iop.org/article/10.3847/1538-4365/aa7de5/pdf

The Infrared Medium-deep Survey. III. Survey of Luminous Quasars at 4.7 ≤ z ≤ 5.4

We present our first results of the survey for high redshift quasars at $5 \lesssim {\rm z} \lesssim 5.7$. The search for quasars in this redshift range has been known to be challenging due to limitations of filter sets used in previous studies. We conducted a quasar survey for two specific redshift ranges, 4.60 $\leq$ z $\leq$ 5.40 and 5.50 $\leq$ z $\leq$ 6.05, using multi-wavelength data that include observations using custom-designed filters, $is$ and $iz$. Using these filters and a new selection technique, we were able to reduce the fraction of interlopers. Through optical spectroscopy, we confirmed seven quasars at 4.7 $\leq$ z $\leq$ 5.4 with $-27.4 < M_{1450} < -26.4$ which were discovered independently by another group recently. We estimated black hole masses and Eddington ratios of four of these quasars from optical and near-infrared spectra, and found that these quasars are undergoing nearly Eddington-limited accretion which is consistent with the rapid growth of supermassive black holes in luminous quasars at z $\sim$ 5.

The Infrared Medium-deep Survey. III. Survey of Luminous Quasars at 4.7 $\leq$ z $\leq$ 5.4

Osteoporosis is a serious bone disease which leads to the increased risk of bone fractures. For prevention and therapy, early detection of osteoporosis is critical. In general, for diagnosis of osteoporosis, dual-energy X-ray absoptiometry (DXA) or densitometry is most commonly used. However DXA exhibits some disadvantages such as ionizing radiation, relatively expensive cost, and limited information on mineralization and geometry of the bone. As an alternative method of DXA, quantitative ultrasound (QUS) is being investigated. In contrast to DXA, QUS is non-ionizing and relatively inexpensive. It can also provide some bone-related parameters (e.g., quantitative measurements including speed of sound and frequency-dependent attenuation). However the estimation of these parameters is difficult and few analytical solutions exist due to the complex behavior of ultrasound propagation in bone. As an alternative to the analytical methods, in most attempts, finite difference time domain (FDTD) method is used for simulation of ultrasound propagation in bone with a limited capability of modeling complex geometries of the bone. Finite element method (FEM) is a better solution since it can handle the complex geometry, but has been rarely applied due to its computational complexity. In this work, we propose an approach of FEM-based simulation of ultrasound propagation in bone. To validate our approach, we have tested simulated and real bone models from micro-CT using the index of speed-of-sound. Our results achieve an average of 97.54% in the computational accuracy.

Finite element simulation of ultrasound propagation in bone for quantitative ultrasound toward the diagnosis of osteoporosis

Multiple color selection techniques are successful in identifying quasars from wide-field broad-band imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at 5 . z . 5.7 due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R ~ 15. By conducting medium-band observations of high redshift quasars at 4.7≤z ≤ 6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color section in separating high redshift quasars from brown dwarfs. In addition, we show that redshifts of high redshift quasars can be determined to an accuracy of △z/(1 + z) = 0.002 – 0.026. The selection technique can be extended to z ~ 7, suggesting that the medium-band observation can be powerful in identifying quasars even at the re-ionization epoch.

/pdf/the-infrared-medium-deep-survey-v-a-new-selection-strategy-3dpn8kzqb0.pdf

Sanghyuk Kim

Papers

Fabrication of electroless nickel plated aluminum freeform mirror for an infrared off-axis telescope.

The Infrared Medium-deep Survey. III. Survey of Luminous Quasars at 4.7 ≤ z ≤ 5.4

The Infrared Medium-deep Survey. III. Survey of Luminous Quasars at 4.7 $\leq$ z $\leq$ 5.4

Finite element simulation of ultrasound propagation in bone for quantitative ultrasound toward the diagnosis of osteoporosis

THE INFRARED MEDIUM-DEEP SURVEY. V. A NEW SELECTION STRATEGY FOR QUASARS AT z > 5 BASED ON MEDIUM-BAND OBSERVATIONS WITH SQUEAN