Search for: All records

https://peer.asee.org/37700

https://peer.asee.org/37296

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."

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 scalingmore »relations defined by more massive galaxies.« less

We present the serendipitous detection of the two main OH maser lines at 1667 and 1665 MHz associated with IRAS 10597+5926 at z ⊙  = 0.19612 in the untargeted Apertif Wide-area Extragalactic imaging Survey (AWES), and the subsequent measurement of the OH 1612 MHz satellite line in the same source. With a total OH luminosity of log( L / L ⊙ ) = 3.90 ± 0.03, IRAS 10597+5926 is the fourth brightest OH megamaser (OHM) known. We measure a lower limit for the 1667/1612 ratio of R 1612  > 45.9, which is the highest limiting ratio measured for the 1612 MHz OH satellite line to date. OH satellite line measurements provide a potentially valuable constraint by which to compare detailed models of OH maser pumping mechanisms. Optical imaging shows that the galaxy is likely a late-stage merger. Based on published infrared and far ultraviolet fluxes, we find that the galaxy is an ultra-luminous infrared galaxy (ULIRG) with log( L TIR / L ⊙ ) = 12.24 that is undergoing a starburst with an estimated star formation rate of 179 ± 40 M ⊙ yr −1 . These host galaxy properties are consistent with the physical conditions responsible for very bright OHM emission. Finally, we provide anmore »update on the predicted number of OH masers that may be found in AWES and estimate the total number of OH masers that will be detected in each of the individual main and satellite OH 18 cm lines.« less