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1. Mitigating Eddington and Malmquist Biases in Latent-Inclination Inference of the Tully-Fisher Relation

   Fu, H (August 2025, Astrophysical journal)

   The Tully-Fisher relation is a vital distance indicator, but its precise inference is challenged by selection bias, statistical bias, and uncertain inclination corrections. This study presents a Bayesian framework that simultaneously addresses these issues. To eliminate the need for individual inclination corrections, inclination is treated as a latent variable with a known probability distribution. To correct for the distance-dependent Malmqvist bias arising from sample selection, the model incorporates Gaussian scatter in the dependent variable, the distribution of the independent variable, and the observational selection function into the data likelihood. To mitigate the statistical bias -- termed the ``general Eddington bias'' -- caused by Gaussian scatter and the non-uniform distribution of the independent variable, two methods are introduced: (1) analytical bias corrections applied to the dependent variable before likelihood computation, and (2) a dual-scatter model that accounts for Gaussian scatter in the independent variable within the likelihood function. The effectiveness of these methods is demonstrated using simulated datasets. By rigorously addressing selection and statistical biases in a latent-variable regression analysis, this work provides a robust approach for unbiased distance estimates from standardizable candles, which is critical for improving the accuracy of Hubble constant determinations. 

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2. SAMI-H  i : The H  i view of the Hα Tully–Fisher relation and data release

   https://doi.org/10.1093/mnras/stac3556  

   Catinella, Barbara; Cortese, Luca; Tiley, Alfred L.; Janowiecki, Steven; Watts, Adam B.; Bryant, Julia J.; Croom, Scott M.; d’Eugenio, Francesco; van de Sande, Jesse; Bland-Hawthorn, Joss; et al (December 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present SAMI-H i, a survey of the atomic hydrogen content of 296 galaxies with integral field spectroscopy available from the SAMI Galaxy Survey. The sample spans nearly 4 dex in stellar mass ($$M_\star = 10^{7.4}-10^{11.1}~ \rm M_\odot$$), redshift z < 0.06, and includes new Arecibo observations of 153 galaxies, for which we release catalogues and H i spectra. We use these data to compare the rotational velocities obtained from optical and radio observations and to show how systematic differences affect the slope and scatter of the stellar-mass and baryonic Tully–Fisher relations. Specifically, we show that $$\rm H\alpha$$ rotational velocities measured in the inner parts of galaxies (1.3 effective radii in this work) systematically underestimate H i global measurements, with H i/$$\rm H\alpha$$ velocity ratios that increase at low stellar masses, where rotation curves are typically still rising and $$\rm H\alpha$$ measurements do not reach their plateau. As a result, the $$\rm H\alpha$$ stellar mass Tully–Fisher relation is steeper (when M⋆ is the independent variable) and has larger scatter than its H i counterpart. Interestingly, we confirm the presence of a small fraction of low-mass outliers of the $$\rm H\alpha$$ relation that are not present when H i velocity widths are used and are not explained by ‘aperture effects’. These appear to be highly disturbed systems for which $$\rm H\alpha$$ widths do not provide a reliable estimate of the rotational velocity. Our analysis reaffirms the importance of taking into account differences in velocity definitions as well as tracers used when interpreting offsets from the Tully–Fisher relation, at both low and high redshifts and when comparing with simulations. 

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3. Preliminary results on the Arecibo Pisces-Perseus Supercluster Survey

   Cortes, Rosemary; Lebron, Mayra; Jones, Michael G.; Koopmann, Rebecca A.; Haynes, Martha P.; APPSS Team, Undergraduate ALFALFA (January 2018, American Astronomical Society, AAS Meeting)

   The Arecibo Pisces-Perseus Supercluster Survey (APPSS) aims to exploit the Baryonic Tully-Fisher Relation to derive distances and peculiar velocities of galaxies in and near the main ridge of the Pisces-Perseus Supercluster (PPS), one of the most prominent features of the Cosmic Web in the nearby Universe. The sample of galaxies contains ~ 600 sources in the low-mass range (8 < log MHI / M⊙ < 9). The source selection was based on the ALFALFA HI survey, SDSS and GALEX photometric data. The sample galaxies have HI masses just below the ALFALFA detection threshold, and were selected to be blue disk systems (low surface brightness sources from optical photometry data). The HI data were obtained at the Arecibo Observatory between the years 2015 and 2016. With this sample, the nature of the galaxy population in and around the PPS will be investigated. The HIMF to log MHI ~ 8.0 along the PPS filament will be measured and using the Tully-Fisher relation it will be possible to make a robust measurement of the infall and backflow onto the filamentary structure.APPSS is collaborative project between more than 10 Undergraduate ALFALFA Team institutions in which each group contributes to the analysis of a subset of the HI PPS data. In this poster, we will present the contributions of the U.P.R. team to the APPSS project. We will show the procedure used for the Arecibo HI data analysis, including some examples, and will show our preliminary results. 

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4. The Arecibo Pisces-Perseus Supercluster Survey: Applying the Baryonic Tully-Fisher Relation

   Ramirez, R.; Rothenberg, E.; Viscardi, T.; Gartenstein, S.; Crone-Odekon, M. (January 2020, American Astronomical Society meeting)

   The Arecibo Pisces-Perseus Supercluster Survey (APPSS) will map out infall to the Pisces-Perseus Supercluster filament using redshift-independent distances from the Baryonic Tully-Fisher Relation (BTFR). Here we examine the properties of outliers to the BTFR, with an emphasis on low mass galaxies. Our goal is partly to determine which galaxies should be excluded from our analysis in order to use the BTFR to obtain accurate distances, and partly to understand the dynamical properties of this population of galaxies. This work has been supported by NSF grant AST-1637339. 

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5. VLA Imaging of HI-bearing Ultra-Diffuse Galaxies from the ALFALFA Survey

   Leisman, L.; Gault, L.; Adams, E.; Mancera Pina, P.; Reiter, K.; Team, Alfalfa "Almost (January 2020, American Astronomical Society meeting)

   Here we present resolved HI and deep optical imaging of 11 HI-bearing ultra-diffuse galaxies (HUDs) from the Karl G. Jansky Very Large Array and the WIYN 3.5m at Kitt Peak National Observatory. We find that the HUDs show blue, mostly irregular stellar populations, and ordered gas distributions with evidence of rotation. Comparing the HI and stellar populations, we find that the HI extends significantly beyond the stellar component, and that the HI disk is often misaligned with respect to the stellar one. We explore the HI mass-diameter scaling relation, and find that though the HUDs have diffuse stellar populations, they fall along this relation, with typical global HI surface densities. We also use 3D kinematic modeling to explore the Baryonic Tully Fisher Relation, and find that the HUDs fall off the relation, rotating too slowly for their baryonic mass, and are compatible with having no "missing baryons." 

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