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  2. We present an HI-optical catalog of ~ 30,000 galaxies based on the 100% complete Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey combined with data from the Sloan Digital Sky Survey (SDSS). Our goal is to facilitate public use of the completed ALFALFA catalog by providing carefully determined matches to SDSS counterparts, including matches for ~ 10,000 galaxies that do not have SDSS spectra. These identifications can provide a basis for further cross-matching with other surveys using SDSS photometric IDs as a reference point. We derive absolute magnitudes and stellar masses for each galaxy using optical colors combined withmore »an internal reddening correction designed for small- and intermediate-mass galaxies with active star formation. We also provide measures of stellar masses and star formation rates based on infrared and/or ultraviolet photometry for galaxies that are detected by the Wide-field Infrared Survey Explorer (WISE) and/or the Galaxy Evolution Explorer (GALEX). Finally, we compare the galaxy population in the ALFALFA-SDSS sample with the populations in several other publicly-available galaxy catalogs, and confirm that ALFALFA galaxies typically have lower masses and bluer colors.« less
  3. We present our work on constructing a template Baryonic Tully-Fisher Relation (BTFR) from galaxies in the local universe that have primary distances. We utilize HI 21 cm line data from the complete Arecibo Legacy Fast ALFA (ALFALFA) survey and the digital HI archive from Springob et al. 2005; we also use photometry from the Sloan Digital Sky Survey (SDSS) and the NASA Sloan Atlas (NSA) MANGA v1_0_2 database; lastly, we have also made use of the Extragalactic Distance Database (EDD) for identifying galaxies with primary distances. After cross-matching the galaxies in these catalogues, we identify some 144 galaxies which meetmore »our requirements for having all the necessary HI and photometry data, having primary distances, residing within 30 Mpc, and having low enough uncertainties to be considered reliable data points. An important trait of this data set is the prominence of low-mass, low-luminosity dwarves. Notably, we find the values for the slope, intercept and intrinsic scatter of the relation to be around 2.3, 4.8, and 0.4, respectively. Further, while unresolved velocity widths have historically produced shallower slopes, and while the BTFR has been shown to have a higher intrinsic scatter for low-mass galaxies, these precedents are not enough to explain the deviation of our data from the “standard” values of the BTFR. This work therefore raises several questions about why this discrepancy exists, how it can be resolved, and what we can learn from it. The authors would like to acknowledge the support of NSF/AST-1714828 and the Brinson Foundation.« less
  4. We present a method for estimating the amount of matter in large-scale (approximately 50 Mpc) filaments using the surrounding velocity infall pattern, based on 242 filaments in the Millennium simulation. We identify filaments using a minimal spanning tree to link large groups and clusters, and find the axis of each filament using a weighted principle component analysis. We improve our previous determination of a typical infall velocity profile by rescaling the profile for each filament by the distance where the infall speed reaches a maximum. We use the resulting average profile to determine a two-parameter piecewise function that can bemore »used to estimate the maximum infall speed and location for individual filaments. Finally, we present the correlation between the maximum infall speed and the mass of the filament. These results will be used as part of the Arecibo Pisces-Perseus Supercluster Survey (APPSS), a project to map the infall pattern around the Pisces-Perseus Supercluster filament. This work is supported by NSF grant AST-1637339.« less
  5. We study how several published baryonic Tully-Fisher relations (BTFRs) fit a large sample of galaxies from the Arecibo legacy fast ALFA (ALFALFA) 21cm survey to determine which BTFR is a better template for calculating the distances and peculiar velocities of the ALFALFA galaxies. In particular, the BTFRs studied were those published by Papastergis et al. (2016) and Lelli et al. (2019). To do so, we first derived the rotational velocities and baryonic masses of a sub sample of galaxies with ”good” data, which make up 68% of the ALFALFA galaxies. We then calculated the best-fit line of the sample usingmore »fivedifferent fitting methods: (1) the ordinary least squares (OLS), (2) the maximum likelihood method assuming no intrinsic scatter as defined by Papastergis et al. (2016), (3) the maximum likelihood method with intrinsic scatter along the perpendicular direction (σ⊥,intr) also defined by Papastergis et al. (2016), (4) the maximum likelihood method assuming intrinsic scatter along the vertical direction (σy) as defined by Lelli et al. (2019)., and (5) the maximum likelihood method with intrinsic scatter along the perpendicular direction (σ⊥) also defined by Lelli et al. (2019). We find that fitting method (2) yields the steepest slope, 3.42, which agrees well with the values obtained in previous studies. We use this fit-line to compare with the two published BTFRs and determine that the BTFR derived by Papastergis et al.(2016) is the better template for calculating the distances and pecu-liar velocities of the ALFALFA catalog. This work was supported by NSF/AST-1714828 and by grants from the Brinson Foundation.« less
  6. The Arecibo Pisces-Perseus Supercluster Survey (APPSS) aims to observationally measure the dark matter mass density of Pisces-Perseus by detecting the peculiar velocities of galaxies falling onto the supercluster. To do this, APPSS will measure galaxies' distances using the Baryonic Tully Fisher Relation (BTFR), which relates a galaxy's baryonic mass and rotational velocity. Recovering the signature of infall as robustly as possible requires a careful choice of rotational velocity measurement, as the use of various velocity definitions changes the scatter and systematics of the relation. We introduce and compare multiple automated methods for measuring a galaxy's rotational velocity using its unresolvedmore »line profile. The velocities discussed include global HI profile width measures commonly reported in large surveys, velocity widths derived from best-fit parametrizations to profiles, and velocity widths derived using more novel methods including the spectral line's curve of growth and neural network-derived velocities which incorporate information about the profile's width and shape. We compare these velocity measures by finding best-fit BTFR relations for two samples of galaxies - the SPARC sample and a selected sample of gas-dominated ALFALFA galaxies (Papastergis et al. 2016). With these best-fit BTFRs, we compare intrinsic scatters and residual correlations with source properties to investigate how velocity choice affects the absolute and systematic uncertainties of BTFR-derived galaxy distances. This research is supported by NSF/AST-1714828 and the Brinson Foundation.« less
  7. ABSTRACT We study the gas kinematics of a sample of six isolated gas-rich low surface brightness galaxies, of the class called ultra-diffuse galaxies (UDGs). These galaxies have recently been shown to be outliers from the baryonic Tully–Fisher relation (BTFR), as they rotate much slower than expected given their baryonic mass, and to have a baryon fraction similar to the cosmological mean. By means of a 3D kinematic modelling fitting technique, we show that the H i in our UDGs is distributed in ‘thin’ regularly rotating discs and we determine their rotation velocity and gas velocity dispersion. We revisit the BTFR addingmore »galaxies from other studies. We find a previously unknown trend between the deviation from the BTFR and the exponential disc scale length valid for dwarf galaxies with circular speeds ≲ 45 km s−1, with our UDGs being at the extreme end. Based on our findings, we suggest that the high baryon fractions of our UDGs may originate due to the fact that they have experienced weak stellar feedback, likely due to their low star formation rate surface densities, and as a result they did not eject significant amounts of gas out of their discs. At the same time, we find indications that our UDGs may have higher-than-average stellar specific angular momentum, which can explain their large optical scale lengths.« less
  8. The Pisces-Perseus Supercluster is one of the most massive and cosmologically significant structures in the local universe. The Arecibo Pisces-Perseus Supercluster Survey (APPSS) will provide observational constraints as to the mass-infall rate onto the main filament of the Supercluster through a detailed analysis of the mass and motion of galaxies within and around the cluster. The APPSS galaxy sample consists of over 2,000 galaxies detected during the ALFALFA survey (a blind, HI 21-cm emission line survey of the local universe) combined with galaxies identified through our recent targeted observing campaign - designed to probe below the HI mass cutoff ofmore »the ALFALFA survey. These APPSS-candidates were observed using the L-band Wide receiver at the Arecibo Observatory over the last 4 years; to date the APPSS targeted observing has led to an HI 21-cm emission line detection rate of ~70% - corresponding to ~500 galaxies with cz < 9,000 km/s. Combining these new observations with the ALFALFA galaxies gives a total of ~2,500 galaxies in the current APPSS sample. Here, we describe and demonstrate the methods used by the APPSS team to reduce and analyze these targeted observations and explore the properties of the entire APPSS galaxy sample (while comparing the properties of the ALFALFA galaxies with the detections from the APPSS targeted observing campaign). This work has been supported by NSF AST-1637339.« less