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Authors = Daniel Kennefick ORCID = 0000-0002-5219-456X

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35 pages, 2394 KiB  
Article
Probing the Low-Mass End of the Black Hole Mass Function via a Study of Faint Local Spiral Galaxies
by Michael S. Fusco, Benjamin L. Davis, Julia Kennefick, Daniel Kennefick and Marc S. Seigar
Universe 2022, 8(12), 649; https://doi.org/10.3390/universe8120649 - 6 Dec 2022
Cited by 5 | Viewed by 2847
Abstract
We present an analysis of the pitch angle distribution function (PADF) for nearby galaxies and its resulting black hole mass function (BHMF) via the well-known relationship between pitch angle and black hole mass. Our sample consists of a subset of 74 spiral galaxies [...] Read more.
We present an analysis of the pitch angle distribution function (PADF) for nearby galaxies and its resulting black hole mass function (BHMF) via the well-known relationship between pitch angle and black hole mass. Our sample consists of a subset of 74 spiral galaxies from the Carnegie-Irvine Galaxy Survey with absolute B-band magnitude MB>19.12 mag and luminosity distance DL25.4 Mpc, which is an extension of a complementary set of 140 more luminous (MB19.12 mag) late-type galaxies. We find the PADFs of the two samples are, somewhat surprisingly, not strongly dissimilar; a result that may hold important implications for spiral formation theories. Our data show a distinct bimodal population manifest in the pitch angles of the Sa–Sc types and separately the Scd–Sm types, with Sa–Sc types having tighter spiral arms on average. Importantly, we uncover a distinct bifurcation of the BHMF, such that the Sa–Sc galaxies typically host so-called “supermassive” black holes (M106M), whereas Scd–Sm galaxies accordingly harbor black holes that are “less-than-supermassive” (M106M). It is amongst this latter population of galaxies where we expect fruitful bounties of elusive intermediate-mass black holes (IMBHs), through which a better understanding will help form more precise benchmarks for future generations of gravitational wave detectors. Full article
(This article belongs to the Section Galaxies and Clusters)
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27 pages, 1873 KiB  
Article
Spirality: A Novel Way to Measure Spiral Arm Pitch Angle
by Deanna Shields, Benjamin Boe, Casey Pfountz, Benjamin L. Davis, Matthew Hartley, Ryan Miller, Zac Slade, M. Shameer Abdeen, Daniel Kennefick and Julia Kennefick
Galaxies 2022, 10(5), 100; https://doi.org/10.3390/galaxies10050100 - 17 Oct 2022
Cited by 19 | Viewed by 3358
Abstract
We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 min per galaxy, assuming 8 GB of working memory. [...] Read more.
We present the MATLAB code Spirality, a novel method for measuring spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Computation time is typically on the order of 2 min per galaxy, assuming 8 GB of working memory. We tested the code using 117 synthetic spiral images with known pitches, varying both the spiral properties and the input parameters. The code yielded correct results for all synthetic spirals with galaxy-like properties. We also compared the code’s results to two-dimensional Fast Fourier Transform (2DFFT) measurements for the sample of nearby galaxies defined by DMS PPak. Spirality’s error bars overlapped 2DFFT’s error bars for 26 of the 30 galaxies. The two methods’ agreement correlates strongly with galaxy radius in pixels and also with i-band magnitude, but not with redshift, a result that is consistent with at least some galaxies’ spiral structure being fully formed by z=1.2, beyond which there are few galaxies in our sample. The Spirality code package also includes GenSpiral, which produces FITS images of synthetic spirals, and SpiralArmCount, which uses a one-dimensional Fast Fourier Transform to count the spiral arms of a galaxy after its pitch is determined. All code is freely available. Full article
(This article belongs to the Special Issue Galactic Structure and Dynamics)
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