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Thumbnail of The Tadpole Galaxy from Hubble
Why does this galaxy have such a long tail? In this stunning vista, based on image data from the Hubble Legacy Archive, distant galaxies form a dramatic backdrop for disrupted spiral galaxy Arp 188, the Tadpole Galaxy. The cosmic tadpole is a mere 420 million light-years distant toward the northern constellation of the Dragon (Draco). Its eye-catching tail is about 280 thousand light-years long and features massive, bright blue star clusters. One story goes that a more compact intruder galaxy crossed in front of Arp 188 - from right to left in this view - and was slung around behind the Tadpole by their gravitational attraction. During the close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust forming the spectacular tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper right. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail's star clusters forming smaller satellites of the large spiral galaxy. APOD in world languages: Arabic (IG), Bulgarian, Catalan, Chinese (Beijing), Chinese (Taiwan), Czech, Dutch, Farsi, French, German, Hebrew, Japanese, Portuguese, Russian, Serbian, Slovenian, Spanish, Taiwanese, Turkish, and Ukrainian
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Selected Publications

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By Henry D. Davis, James G. Harkness, Isa M. Kohls, Brian D. Jensen, Richard Vanfleet, Nathan B. Crane, and Robert C. Davis
Abstract:

High-temperature microfluidic devices (such as gas chromatography microcolumns) have traditionally been fabricated using photolithography, etching, and wafer bonding which allow for precise microscale features but lack the ability to form complex 3D designs. Metal additive manufacturing could enable higher complexity microfluidic designs if reliable methods for fabrication are developed, but forming small negative features is challenging-especially in powder-based processes. In this paper, the formation of sealed metal microchannels was demonstrated using stainless-steel binder jetting with bronze infiltration. To create small negative features, bronze infiltrant must fill the porous part produced by binder jetting without filling the negative features. This was achieved through sacrificial powder infiltration (SPI), wherein sacrificial powder reservoirs (pore size similar to 60 mu m) are used to control infiltrant pressure. With this pressure control, the infiltrant selectively filled the small pores between particles in the printed part (pore size similar to 3 mu m) while leaving printed microchannels (700 mu m and 930 mu m) empty. To develop the SPI method, a pore filling study was performed in this stainless-steel/bronze system with 370 mu m, 650 mu m, and 930 mu m microchannel segments. This study enabled SPI process design on these length scales by determining variations in pore filling across a sample and preferential filling between different sized pores.

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By Jacob A. Guerrette, Aleksandr V. Mosenkov, Dallin Spencer, and Zacory D. Shakespear
Abstract:

The structural parameters of a galaxy can be used to gain insight into its formation and evolution history. In this paper, we strive to compare the Milky Way's structural parameters to other, primarily edge-on, spiral galaxies in order to determine how our Galaxy measures up to the Local Universe. For our comparison, we use the galaxy structural parameters gathered from a variety of literature sources in the optical and near-infrared wave bands. We compare the scale length, scale height, and disk flatness for both the thin and thick disks, the thick-to-thin disk mass ratio, the bulge-to-total luminosity ratio, and the mean pitch angle of the Milky Way's spiral arms to those in other galaxies. We conclude that many of the Milky Way's structural parameters are largely ordinary and typical of spiral galaxies in the Local Universe, though the Galaxy's thick disk appears to be appreciably thinner and less extended than expected from zoom-in cosmological simulations of Milky Way-mass galaxies with a significant contribution of galaxy mergers involving satellite galaxies.

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By Mitchell C. Cutler, Mylan R. Cook, Mark K. Transtrum, and Kent L. Gee
Abstract:

Separating crowd responses from raw acoustic signals at sporting events is challenging because recordings contain complex combinations of acoustic sources, including crowd noise, music, individual voices, and public address (PA) systems. This paper presents a data-driven decomposition of recordings of 30 collegiate sporting events. The decomposition uses machine-learning methods to find three principal spectral shapes that separate various acoustic sources. First, the distributions of recorded one-half-second equivalent continuous sound levels from men's and women's basketball and volleyball games are analyzed with regard to crowd size and venue. Using 24 one-third-octave bands between 50 Hz and 10 kHz, spectrograms from each type of game are then analyzed. Based on principal component analysis, 87.5% of the spectral variation in the signals can be represented with three principal components, regardless of sport, venue, or crowd composition. Using the resulting three-dimensional component coefficient representation, a Gaussian mixture model clustering analysis finds nine different clusters. These clusters separate audibly distinct signals and represent various combinations of acoustic sources, including crowd noise, music, individual voices, and the PA system.

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By Aleksandr V Mosenkov, Savanah Turner, and Crystal-Lynn Bartier (et al.)
Abstract:

In this paper, we look to analyse the spiral features of grand-design, multiarmed, and flocculent spiral galaxies using deep optical imaging from DESI Legacy Imaging Surveys. We explore the resulting distributions of various characteristics of spiral structure beyond the optical radius, such as the distributions of azimuthal angle, the extent of spiral arms, and of the spiral arm widths for the aforementioned galaxy classes. We also compare the measured properties for isolated galaxies and galaxies in groups and clusters. We find that, on average, compared to multiarmed and flocculent spiral galaxies, the spiral arms of grand-design galaxies exhibit slightly larger azimuthal angles, greater extent, and larger widths in the periphery of the galaxy. Furthermore, on average, isolated galaxies tend to have slightly smaller widths of outer spiral arms compared to galaxies in tight environments, which is likely related to the tidally induced mechanism for generating wider outer spiral arms. We also report that breaks of the disc surface brightness profiles are often related to the truncation of spiral arms in galaxies.

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By Michael D. Joner (et al.)
Abstract:

We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce maps of the accretion disk temperature fluctuations delta T resolved in time and radius. The delta T maps are dominated by coherent radial structures that move slowly (v c) inward and outward, which conflicts with the idea that disk variability is driven only by reverberation. Instead, these slow-moving temperature fluctuations are likely due to variability intrinsic to the disk. We test how modifying the input lightcurves by smoothing and subtracting them changes the resulting delta T maps and find that most of the temperature fluctuations exist over relatively long timescales (hundreds of days). We show how detrending active galactic nucleus (AGN) lightcurves can be used to separate the flux variations driven by the slow-moving temperature fluctuations from those driven by reverberation. We also simulate contamination of the continuum emission from the disk by continuum emission from the broad-line region (BLR), which is expected to have spectral features localized in wavelength, such as the Balmer break contaminating the U band. We find that a disk with a smooth temperature profile cannot produce a signal localized in wavelength and that any BLR contamination should appear as residuals in our model lightcurves. Given the observed residuals, we estimate that only similar to 20% of the variable flux in the U and u lightcurves can be due to BLR contamination. Finally, we discus how these maps not only describe the data but can make predictions about other aspects of AGN variability.

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By A. V. Mosenkov, S. K. H. Bahr, and Z. Shakespear (et al.)
Abstract:

Polar-ring galaxies are photometrically and kinematically decoupled systems that are highly inclined to the major axis of the host. These galaxies have been explored since the 1970s, but the rarity of these systems has made such systematic studies difficult. However, over 250 good candidates have been identified. In this work, we examine a sample of over 18 000 galaxies from the Sloan Digital Sky Survey (SDSS) Stripe 82 for the presence of galaxies with polar structures. Using deep SDSS Stripe 82, DESI Legacy Imaging Surveys, and Hyper Suprime-Cam Subaru Strategic Program, we selected 53 good candidate galaxies with photometrically decoupled polar rings, 9 galaxies with polar halos, 6 galaxies with polar bulges, and 34 possibly forming polar-ring galaxies, versus 13 polar-ring candidates previously selected in Stripe 82. Our results suggest that the occurrence rate of galaxies with polar structures may be significantly underestimated, as revealed by the deep observations, and may amount to 1-3% of non-dwarf galaxies.