Search for: All records

Context. Outflows from low-mass star-forming galaxies are a fundamental ingredient for models of galaxy evolution and cosmology. Despite seemingly favourable conditions for outflow formation in compact starbursting galaxies, convincing observational evidence for kiloparsec-scale outflows in such systems is scarce. Aims. The onset of kiloparsec-scale ionised filaments in the halo of the metal-poor compact dwarf SBS 0335−052E was previously not linked to an outflow. In this paper we investigate whether these filaments provide evidence for an outflow. Methods. We obtained new VLT/MUSE WFM and deep NRAO/VLA B-configuration 21 cm data of the galaxy. The MUSE data provide morphology, kinematics, and emission line ratios of H β /H α and [O  III ] λ 5007/H α of the low surface-brightness filaments, while the VLA data deliver morphology and kinematics of the neutral gas in and around the system. Both datasets are used in concert for comparisons between the ionised and the neutral phase. Results. We report the prolongation of a lacy filamentary ionised structure up to a projected distance of 16 kpc at SB H α  = 1.5 × 10 −18 erg s cm −2 arcsec −2 . The filaments exhibit unusual low H α /H β  ≈ 2.4 and low [O  III ]/H α  ∼ 0.4 − 0.6 typical of diffuse ionised gas. They are spectrally narrow (∼20 km s −1 ) and exhibit no velocity sub-structure. The filaments extend outwards from the elongated H  I halo. On small scales, the N HI peak is offset from the main star-forming sites. The morphology and kinematics of H  I and H  II reveal how star-formation-driven feedback interacts differently with the ionised and the neutral phase. Conclusions. We reason that the filaments are a large-scale manifestation of star-formation- driven feedback, namely limb-brightened edges of a giant outflow cone that protrudes through the halo of this gas-rich system. A simple toy model of such a conical structure is found to be commensurable with the observations. 

The effects of total ionizing dose (TID) on SRAM physical unclonable functions (PUF) are studied through x-ray and proton irradiation of commercially available SRAM. Negative shifts in the Fractional Hamming Weight (FHW) were measured with increasing TID, indicating a migration of bistable cells towards logic low. Additionally, positive shifts in the intra-die Fractional Hamming Distance (FHD) were measured and indicate changes to the virtual fingerprint of an SRAM PUF with TID, especially in devices that were dosed while holding data. Shifts in inter-die FHD were negligible, allowing individual SRAMs still to be easily identified based on the FHD between a known and unknown sample even after moderate amounts of TID. In some cases, SRAMs could still be identified by their PUFs after the devices had failed. In all cases, the irradiated SRAM devices retain their virtual fingerprint after recovery through annealing. 

The ALFALFA blind extragalactic survey has populated the faint end of the neutral hydrogen (HI) mass function with statistical confidence for the first time. Of particular interest is a subset of the ALFALFA detections, termed "ultra-compact high-velocity clouds" (UCHVCs). These systems, if located within ~1 Mpc, would populate the lowest-mass end of the HI mass function. Subsequent optical imaging has revealed that some of these UCHVCs harbor associated (though sparse) stellar populations, revealing that they may be some of the most extreme galaxies known in the Local Volume, with optical properties akin to ultra-faint dwarf galaxies but with significant neutral gas reservoirs. In this campaign, we investigate the neutral hydrogen properties of six UCHVC candidate galaxies using deep VLA HI spectral line imaging. A companion poster (Bralts-Kelly et al.) presents 3D kinematic modeling of selected sources. Here, we show the imaging products and discuss the morphological and kinematic properties of the six chosen sources: AGC 198606, AGC 215417, AGC219656, AGC 249525, AGC 258237, and AGC 268069. 

We present new Spitzer 3.6 µm images of the 82 galaxies in the "Survey of HI in Extremely Low-mass Dwarfs" (SHIELD). Selected from the ALFALFA blind HI survey, SHIELD is a volumetrically complete sample of galaxies with HI mass reservoirs smaller than 2x107 M☉. These galaxies populate extreme portions of parameter space and they offer unique opportunities to explore the physical properties of very low-mass halos in the local Universe. The new Spitzer images allow us to measure the stellar masses of the SHIELD galaxies. We discuss methods used to remove image artifacts and to excise foreground and background contaminants. We then measure the total 3.6 µm fluxes of the systems and apply a mass to light ratio in order to derive their stellar masses. We discuss the application of this technique to the Leoncino dwarf (AGC198691, one of the most extremely metal-poor galaxies known), resulting in a stellar mass of 7.3x107 M☉. This work has been supported by NSF AST-1637339 and by Macalester College. 

The ALFALFA blind extragalactic survey has populated the faint end of the neutral hydrogen (HI) mass function with statistical confidence for the first time. Of particular interest is a subset of the ALFALFA detections, termed "ultra-compact high-velocity clouds" (UCHVCs). These systems, if located within ~1 Mpc, would populate the lowest-mass end of the HI mass function. Subsequent optical imaging has revealed that some of these UCHVCs harbor associated (though sparse) stellar populations, revealing that they may be some of the most extreme galaxies known in the Local Volume, with optical properties akin to ultra-faint dwarf galaxies but with significant neutral gas reservoirs. In this campaign, we investigate the neutral hydrogen properties of six UCHVC candidate galaxies using deep VLA HI spectral line imaging. A companion poster (Paine et al.) presents details on the data reduction, imaging, and resulting products. Here, we examine the morphological and kinematic properties of selected sources. We apply the modeling software 3D-Barolo to our deep HI images in order to derive the rotation curve and constrain the inclination angle for each source. Successful modeling allows us to determine the dynamical masses of these objects and thus to consider them in the context of various fundamental scaling relations defined by more massive galaxies.