Search

We present H-alpha velocity maps for the HIghMass galaxies UGC 7899, UGC 8475, UGC 9037 and UGC 9334, obtained with the SITELLE Imaging Fourier Transform Spectrometer on the Canada-France-Hawaii Telescope, to search for kinematic signatures of late gas accretion to explain their large atomic gas reservoirs. The maps for UGC 7899, UGC 9037, and UGC 9334 are amenable to disk wide radial flow searches with the DiskFit algorithm, and those for UGC 7899 and UGC 9037 are also amenable to inner-disk kinematic analyses. We find no evidence for outer disk radial flows down to Vr ~ 20 km/s in UGC 9037 and UGC 9334, but hints of such flows in UGC 7899. Conversely, we find clear signatures of inner (r ~ 5 kpc) noncircularities in UGC 7899 and UGC 9037 that can be modelled as either bisymmetric (which could be produced by a bar) or radial flows. Comparing these models to the structure implied by photometric disk-bulge-bar decompositions, we favour inner radial flows in UGC 7899 and an inner bar in UGC 9037. With hints of outer disk radial flows and an outer disk warp, UGC 7899 is the best candidate for late accretion among the galaxies examined, but additional modelling is required to disentangle potential degeneracies between these signatures in H I and H-alpha velocity maps. Our search provides only weak = constraints on hot-mode accretion models that could explain the unusually high H I content of HIghMass galaxies., Comment: 14 pages, 11 figures, published in MNRAS Oct 8th, 2021

The NSF-sponsored Undergraduate ALFALFA Team (UAT) promotes long-term collaborative research opportunities for faculty and students from 23 U.S. public and private primarily undergraduate institutions (PUIs) within the context of the extragalactic ALFALFA HI blind legacy survey project. Over twelve project years of partnering with Arecibo and Green Bank Observatories, the UAT has had a demonstrable impact on the health of a legacy astronomy project, science education, and equity/inclusion in astronomy, with successful outcomes for 373 UAT students (39% women; ~30% members of underrepresented groups) and 34 faculty (44% women). The UAT model is adaptable to many large scientific projects and can be supported by relatively modest funding. We recommend that granting agencies identify funding resources to support the model, either as an add-on to legacy grant support or as a stand-alone funding source. This could include encouragement of UAT-like components in large scale projects currently being developed, such as the LSST and TMT. By doing this, we will recognize the high numbers of astronomy research-trained heavy-teaching-load faculty at PUIs as an under-utilized resource of the astronomy community (see also White Paper by Ribaudo et al.). These members of our community have the skills and the strong desire to contribute meaningfully to their field, as well as the ability to encourage and interact closely with many talented and motivated undergraduate students from all backgrounds., Comment: Astro2020 White Paper submission, 12 pages

We report a multi-objective campaign of targeted 21 cm HI line observations of sources selected from the Arecibo Legacy Fast ALFA (Arecibo L-band Feed Array) survey (ALFALFA) and galaxies identified by their morphological and photometric properties in the Sloan Digital Sky Survey (SDSS). The aims of this program have been (1) to confirm the reality of some ALFALFA sources whose enigmatic nature suggest additional multiwavelength observations; (2) to probe the low signal-to-noise ratio regime, below the ALFALFA reliability limit; and (3) to explore the feasibility of using optical morphology, color and surface brightness to identify gas-rich objects in the region of the Pisces-Perseus Supercluster (PPS) whose HI fluxes are below the ALFALFA sensitivity limit at that distance. As expected, the reliability of ALFALFA detections depends strongly on the signal-to-noise ratio of the HI line signal and its coincidence with a probable stellar counterpart identified by its optical properties, suggestive of on-going star formation. The identification of low mass, star forming populations enables targeted HI line observations to detect galaxies with HI line fluxes below the ALFALFA sensitivity limits in fixed local volumes (D < 100 Mpc). The method explored here serves as the basis for extending the sample of gas-bearing objects as part of the on-going Arecibo Pisces-Perseus Supercluster Survey (APPSS)., Comment: 22 pages, 2 tables, 7 figures. Submitted to the Astronomical Journal

We present the catalog of ~31500 extragalactic HI line sources detected by the completed ALFALFA survey out to z < 0.06 including both high signal-to-noise ratio (> 6.5) detections and ones of lower quality which coincide in both position and recessional velocity with galaxies of known redshift. We review the observing technique, data reduction pipeline, and catalog construction process, focusing on details of particular relevance to understanding the catalog's compiled parameters. We further describe and make available the digital HI line spectra associated with the catalogued sources. In addition to the extragalactic HI line detections, we report nine confirmed OH megamasers and ten OH megamaser candidates at 0.16 < z < 0.22 whose OH line signals are redshifted into the ALFALFA frequency band. Because of complexities in data collection and processing associated with the use of a feed-horn array on a complex single-dish antenna in the terrestrial radio frequency interference environment, we also present a list of suggestions and caveats for consideration by users of the ALFALFA extragalactic catalog for future scientific investigations., Comment: 24 pages 8 figures See http://egg.astro.cornell.edu/alfalfa/data for ASCII and CSV datafiles corresponding to Table 2. To appear in Astrophys.J.Suppl

We present new high-resolution HI spectral line imaging of Coma P, the brightest HI source in the system HI 1232$+$20. This extremely low surface brightness galaxy was first identified in the ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic HI source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the HI morphology and kinematics at a variety of physical scales. The HI morphology is irregular, reaching only moderate maxima in mass surface density (peak $\sigma_{\rm HI}\sim 10$ $M_{\odot}$ pc$^{-2}$). Gas of lower surface brightness extends to large radial distances, with the HI diameter measured at 4.0$\pm$0.2 kpc inside the 1 $M_{\odot}$ pc$^{-2}$ level. We quantify the relationships between HI gas mass surface density and various types of star formation by considering GALEX far ultraviolet observations and H$\alpha$ nondetections. We describe Coma P's complex HI kinematics using spatially resolved position-velocity analysis and three-dimensional modeling. Both methods of analysis suggest that Coma P's kinematics show signatures of either the collision of two HI disks or a significant infall event. Coma P is just consistent (within 3$\sigma$) with the known M$_{\rm HI}$ -- D$_{\rm HI}$ scaling relation. It is either too large for its HI mass, has too low an HI mass for its HI size, or the two HI components artificially extend its HI size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully--Fisher relation, although the complexity of the HI dynamics complicates the interpretation. The collective HI characteristics of Coma P make it unusual among known galaxies in the nearby universe. [Abridged], Comment: 26 pages, 17 figures. Published in the Astronomical Journal 155, 65

We use the ALFALFA HI survey to examine whether the cold gas reservoirs of galaxies are inhibited or enhanced in large-scale filaments. Our sample includes 9947 late-type galaxies with HI detections, and 4236 late-type galaxies with well-determined HI detection limits that we incorporate using survival analysis statistics. We find that, even at fixed local density and stellar mass, and with group galaxies removed, the HI deficiency of galaxies in the stellar mass range 8.5

We investigate a sample of 3 dwarf elliptical galaxies in the Virgo Cluster which have significant reservoirs of HI. We present deep optical imaging (from CFHT and KPNO), HI spectra (Arecibo) and resolved HI imaging (VLA) of this sample. These observations confirm their HI content and optical morphologies, and indicate that the gas is unlikely to be recently accreted. The sample has more in common with dwarf transitionals, although dwarf transitionals are generally lower in stellar mass and gas fraction. VCC 190 has an HI tidal tail from a recent encounter with the massive spiral galaxy NGC 4224. In VCC 611, blue star-forming features are observed which were unseen by shallower SDSS imaging., Comment: 11 pages, 6 figures, accepted in AJ

We present a sample of 115 very low optical surface brightness, highly extended, HI-rich galaxies carefully selected from the ALFALFA survey that have similar optical absolute magnitudes, surface brightnesses, and radii to recently discovered "ultra-diffuse" galaxies (UDGs). However, these systems are bluer and have more irregular morphologies than other UDGs, are isolated, and contain significant reservoirs of HI. We find that while these sources have normal star formation rates for HI selected galaxies of similar stellar mass, they have very low star formation efficiencies. We further present deep optical and HI synthesis follow up imaging of three of these HI-bearing ultra-diffuse sources. We measure HI diameters extending to ~40 kpc, but note that while all three sources have large HI diameters for their stellar mass, they are consistent with the HI mass - HI radius relation. We further analyze the HI velocity widths and rotation velocities for the unresolved and resolved sources respectively, and find that the sources appear to inhabit halos of dwarf galaxies. We estimate spin parameters, and suggest that these sources may exist in high spin parameter halos, and as such may be potential HI-rich progenitors to the ultra-diffuse galaxies observed in cluster environments., Comment: 19 pages, 9 figures, accepted to ApJ

We present resolved HI and CO observations of three galaxies from the HIghMass sample, a sample of HI-massive ($M_{HI} > 10^{10} M_\odot$), gas-rich ($M_{HI}$ in top $5\%$ for their $M_*$) galaxies identified in the ALFALFA survey. Despite their high gas fractions, these are not low surface brightness galaxies, and have typical specific star formation rates (SFR$/M_*$) for their stellar masses. The three galaxies have normal star formation rates for their HI masses, but unusually short star formation efficiency scale lengths, indicating that the star formation bottleneck in these galaxies is in the conversion of HI to H$_2$, not in converting H$_2$ to stars. In addition, their dark matter spin parameters ($\lambda$) are above average, but not exceptionally high, suggesting that their star formation has been suppressed over cosmic time but are now becoming active, in agreement with prior H$\alpha$ observations., Comment: 20 pages, 13 figures

We present the HI content of galaxies in nearby groups and clusters as measured by the 70% complete Arecibo Legacy Fast-ALFA (ALFALFA) survey, including constraints from ALFALFA detection limits. Our sample includes 22 systems at distances between 70-160 Mpc over the mass range 12.5

We present VLA HI spectral line imaging of 5 sources discovered by ALFALFA. These targets are drawn from a larger sample of systems that were not uniquely identified with optical counterparts during ALFALFA processing, and as such have unusually high HI mass to light ratios. These candidate "Almost Dark" objects fall into 4 categories: 1) objects with nearby HI neighbors that are likely of tidal origin; 2) objects that appear to be part of a system of multiple HI sources, but which may not be tidal in origin; 3) objects isolated from nearby ALFALFA HI detections, but located near a gas-poor early-type galaxy; 4) apparently isolated sources, with no object of coincident redshift within ~400 kpc. Roughly 75% of the 200 objects without identified counterparts in the $\alpha$.40 database (Haynes et al. 2011) fall into category 1. This pilot sample contains the first five sources observed as part of a larger effort to characterize HI sources with no readily identifiable optical counterpart at single dish resolution. These objects span a range of HI mass [7.41 < log(M$_{\rm HI}$) < 9.51] and HI mass to B-band luminosity ratios (3 < M$_{\rm HI}$/L$_{\rm B}$ < 9). We compare the HI total intensity and velocity fields to SDSS optical imaging and to archival GALEX UV imaging. Four of the sources with uncertain or no optical counterpart in the ALFALFA data are identified with low surface brightness optical counterparts in SDSS imaging when compared with VLA HI intensity maps, and appear to be galaxies with clear signs of ordered rotation. One source (AGC 208602) is likely tidal in nature. We find no "dark galaxies" in this limited sample. The present observations reveal complex sources with suppressed star formation, highlighting both the observational difficulties and the necessity of synthesis follow-up observations to understand these extreme objects. (abridged), Comment: Astronomical Journal, in press

We present first results of the study of a set of exceptional HI sources identified in the 40% ALFALFA extragalactic HI survey catalog alpha.40 as being both HI massive (M_HI > 10^10 Msun) and having high gas fractions for their stellar masses: the HIghMass galaxy sample. We analyze UV- and optical-broadband and Halpha images to understand the nature of their relatively underluminous disks in optical and to test whether their high gas fractions can be tracked to higher dark matter halo spin parameters or late gas accretion. Estimates of their star formation rates (SFRs) based on SED-fitting agree within uncertainties with the Halpha luminosity inferred SFRs. The HII region luminosity functions have standard slopes at the luminous end. The global SFRs demonstrate that the HIghMass galaxies exhibit active ongoing star formation (SF) with moderate SF efficiency, but relative to normal spirals, a lower integrated SFR in the past. Because the SF activity in these systems is spread throughout their extended disks, they have overall lower SFR surface densities and lower surface brightness in the optical bands. Relative to normal disk galaxies, the majority of HIghMass galaxies have higher Halpha equivalent widths and are bluer in their outer disks, implying an inside-out disk growth scenario. Downbending double exponential disks are more frequent than upbending disks among the gas-rich galaxies, suggesting that SF thresholds exist in the downbending disks, probably as a result of concentrated gas distribution., Comment: 66 pages, 17 figures, 3 tables; accepted for publication in ApJ; higher resolution figures available via http://www.asiaa.sinica.edu.tw/~shan/HIghMass_140728.pdf

We present resolved HI observations of two galaxies, UGC 9037 and UGC 12506, members of a rare subset of galaxies detected by the ALFALFA extragalactic HI survey characterized by high HI mass and high gas fraction for their stellar masses. Both of these galaxies have M$_*>10^{10}$ M$_\odot$ and M$_\text{HI}>$ M$_*$, as well as typical star formation rates for their stellar masses. How can such galaxies have avoided consuming their massive gas reservoirs? From gas kinematics, stability, star formation, and dark matter distributions of the two galaxies, we infer two radically different histories. UGC 9037 has high central HI surface density ($>10$ M$_\odot$ pc$^{-2}$). Its gas at most radii appears to be marginally unstable with non-circular flows across the disk. These properties are consistent with UGC 9037 having recently acquired its gas and that it will soon undergo major star formation. UGC 12506 has low surface densities of HI, and its gas is stable over most of the disk. We predict its gas to be HI-dominated at all except the smallest radii. We claim a very high dark matter halo spin parameter for UGC 12506 ($\lambda=0.15$), suggesting that its gas is older, and has never undergone a period of star formation significant enough to consume the bulk of its gas., Comment: 36 pages, 10 figures, AJ accepted

We investigate the dwarf (M_B> -16) galaxies in the Virgo cluster in the radio, optical, and ultraviolet regimes. Of the 365 galaxies in this sample, 80 have been detected in HI by the Arecibo Legacy Fast ALFA survey. These detections include 12 early-type dwarfs which have HI and stellar masses similar to the cluster dwarf irregulars and BCDs. In this sample of 12, half have star-formation properties similar to late type dwarfs, while the other half are quiescent like typical early-type dwarfs. We also discuss three possible mechanisms for their evolution: that they are infalling field galaxies that have been or are currently being evolved by the cluster, that they are stripped objects whose gas is recycled, and that the observed HI has been recently reaccreted. Evolution by the cluster adequately explains the star-forming half of the sample, but the quiescent class of early-type dwarfs is most consistent with having recently reaccreted their gas., Comment: 18 pages, 9 figures

We present a current catalog of 21 cm HI line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800 square degrees of sky: the alpha.40 catalog. Covering 40% of the final survey area, the alpha.40 catalog contains 15855 sources in the regions 07h30m < R.A. < 16h30m, +04 deg < Dec. < +16 deg and +24 deg < Dec. < +28 deg and 22h < R.A. < 03h, +14 deg < Dec. < +16 deg and +24 deg < Dec. < +32 deg. Of those, 15041 are certainly extragalactic, yielding a source density of 5.3 galaxies per square degree, a factor of 29 improvement over the catalog extracted from the HI Parkes All Sky Survey. In addition to the source centroid positions, HI line flux densities, recessional velocities and line widths, the catalog includes the coordinates of the most probable optical counterpart of each HI line detection, and a separate compilation provides a crossmatch to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented of the completeness, width dependent sensitivity function and bias inherent in the current alpha.40 catalog. The impact of survey selection, distance errors, current volume coverage and local large scale structure on the derivation of the HI mass function is assessed. While alpha.40 does not yet provide a completely representative sampling of cosmological volume, derivations of the HI mass function using future data releases from ALFALFA will further improve both statistical and systematic uncertainties., Comment: 62 pages, 28 figures. See http://egg.astro.cornell.edu/alfalfa/data for ASCII and CSV datafiles corresponding to Tables 1, 2 and 3. A higher resolution PDF version can be found at http://egg.astro.cornell.edu/alfalfa/pubs.php. To appear in Nov 2011 Astron. J

We investigate the potential of the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) to discriminate between two theoretical models predicting anomalous events with jets and large missing transverse energy, minimal supersymmetry and Little Higgs with T Parity. We focus on a simple test case scenario, in which the only exotic particles produced at the LHC are heavy color-triplet states (squarks or T-quarks), and the only open decay channel for these particles is into the stable missing-energy particle (neutralino or heavy photon) plus a quark. We find that in this scenario, the angular and momentum distributions of the observed jets are sufficient to discriminate between the two models with a few inverse fb of the LHC data, provided that these distributions for both models and the dominant Standard Model backgrounds can be reliably predicted by Monte Carlo simulations., Comment: 19 pages, 6 figures. v3: included calibration procedure of PGS to CMS detector and an estimate of new physics discovery significance levels