74 research outputs found

    HI in Virgo's "Red and Dead" Dwarf Ellipticals - A Tidal Tail and Central Star Formation

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    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 A

    HIghMass - High HI Mass, HI-Rich Galaxies at z∼0z\sim0: Combined HI and H2_2 Observations

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    We present resolved HI and CO observations of three galaxies from the HIghMass sample, a sample of HI-massive (MHI>1010M⊙M_{HI} > 10^{10} M_\odot), gas-rich (MHIM_{HI} in top 5%5\% for their M∗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∗/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 H2_2, not in converting H2_2 to stars. In addition, their dark matter spin parameters (λ\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 Hα\alpha observations.Comment: 20 pages, 13 figure

    You are not like the rest of them: disrupting meta-perceptions dilutes dehumanization

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    Political polarization, fueled by conflicting meta-perceptions, presents a critical obstacle to constructive discourse and collaboration. These meta-perceptions-how one group perceives another group's views of them-are often inaccurate and can lead to detrimental outcomes such as increased hostility and dehumanization. Across two studies, we introduce and experimentally test a novel approach that exposes participants to atypical, counter-stereotypical members of an opposing group who either confirm or disrupt their existing meta-perceptions. We find that disrupting meta-perceptions decreases dehumanization of the partner, increases interest in wanting to learn more about them, but fails to increase willingness to interact in the future with the partner. We conduct an exploratory text analysis to uncover differences in word choice by condition. Our research adds a new dimension to the existing body of work by examining the efficacy of alternative intervention strategies to improve intergroup relations in politically polarized settings

    The ALFALFA "Almost Darks" Campaign: Pilot VLA HI Observations of Five High Mass-to-Light Ratio Systems

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    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 α\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(MHI_{\rm HI}) < 9.51] and HI mass to B-band luminosity ratios (3 < MHI_{\rm HI}/LB_{\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 pres

    HIghMass—High H I Mass, H I-rich Galaxies at z ~ 0: Combined H I and H_2 Observations

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    We present resolved and CO observations of three galaxies from the HIghMass sample, a sample of -massive (M_(H I) > 10^(10) M⊙), gas-rich (M_(H I) in the 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 SFRs for their masses, but unusually short star formation efficiency scale lengths, indicating that the star formation bottleneck in these galaxies is in the conversion of H I to H_2, not in converting H_2 to stars. In addition, their dark matter spin parameters (λ) are above average, but not exceptionally high, suggesting that their star formation has been suppressed over cosmic time but is now becoming active, in agreement with prior Hα observations
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