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The halo of our Galaxy is populated with a significant number of high-velocity clouds (HVCs) moving with a speed up to $500$ km/s. It is suggested that these HVCs might contain a non-negligible fraction of the missing baryons. The main aim…

Astrophysics of Galaxies · Physics 2024-12-03 Noraiz Tahir , Martin Lopez Corredoira , Francesco De Paolis

We present the first installment of HI sources extracted from the Arecibo Legacy Fast ALFA (ALFALFA) extragalactic survey, initiated in 2005. Sources have been extracted from 3-D spectral data cubes and then examined interactively to yield…

We combine HI 21cm observations of the Milky Way, M31, and the local galaxy population with QSO absorption-line measurements to geometrically model the three-dimensional distribution of infalling neutral gas clouds (HVCs) in the extended…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Philipp Richter

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…

CO--0.40--0.22 is a peculiar molecular cloud that is compact and has an extraordinary broad velocity width. It is found in the central molecular zone of our Galaxy. In this direction, there is another cloud with an H$_2$O maser spot at a…

Astrophysics of Galaxies · Physics 2017-05-10 Yuhei Iwata , Haruka Kato , Daisuke Sakai , Tomoharu Oka

We determine the distance to 38 clusters of galaxies in the redshift range 0.14 < z < 0.89 using X-ray data from Chandra and Sunyaev-Zeldovich Effect data from the Owens Valley Radio Observatory and the Berkeley-Illinois-Maryland…

Astrophysics · Physics 2009-11-11 M. Bonamente , M. Joy , S. La Roque , J. Carlstrom , E. Reese , K. Dawson

We have recently identified several high velocity (V < -100 km/s) clouds in the directions of Mrk 509 and PKS 2155-304 that have unusual ionization properties. The clouds exhibit strong C IV absorption with little or no detectable low ion…

Astrophysics · Physics 2009-10-30 Kenneth R. Sembach , Blair D. Savage , Limin Lu , Edward M. Murphy

Radio observations of gas in the Milky Way and Local Group are vital for understanding how galaxies function as systems. The unique sensitivity of Arecibo's 305m dish, coupled with the 7-beam Arecibo L-Band Feed Array (ALFA), provides an…

Growing evidence supports the suggestion that the compact high-velocity clouds of HI (CHVCs) are located throughout the Local Group and continue to fuel galactic evolution. Recent distance estimates to individual objects lie in the range…

Astrophysics · Physics 2009-10-31 Robert Braun , W. Butler Burton

We have detected over 400 HI clouds in the lower halo of the Galaxy within the pilot region of the Galactic All-Sky Survey (GASS), a region of the fourth quadrant that spans 18 degrees in longitude, 40 degrees in latitude and is centered on…

We present a catalog of 59 ultra-compact high velocity clouds (UCHVCs) extracted from the 40% complete ALFALFA HI-line survey. The ALFALFA UCHVCs have median flux densities of 1.34 Jy km/s, median angular diameters of 10', and median…

Cosmology and Nongalactic Astrophysics · Physics 2013-04-18 Elizabeth A. K. Adams , Riccardo Giovanelli , Martha P. Haynes

We characterize the kinematic and magnetic properties of HI filaments located in a high Galactic latitude region ($165^\circ < \alpha < 195^\circ$ and $12^\circ < \delta < 24^\circ$). We extract three-dimensional filamentary structures…

Astrophysics of Galaxies · Physics 2023-09-20 Doyeon Avery Kim , Susan E Clark , Mary E Putman , Larry Li

The cold dark matter (CDM) structure formation model predicts that about 5-10 percent of a typical galactic halo of mass $\sim 10^{12} \ms$ is in substructures with masses $\lesssim 10^8 \ms$. To directly detect such substructures, we…

Astrophysics · Physics 2008-11-26 Kaiki Taro Inoue , Masashi Chiba

The high-velocity clouds (HVCs) in the outer Milky Way at $20^{\circ} < l < 190^{\circ}$ have similar spatial locations, metallicities, and kinematics. Moreover, their locations and kinematics are coincident with several extraplanar stellar…

Astrophysics of Galaxies · Physics 2022-10-21 Todd M. Tripp

The Leading Arm is a tidal feature that is in front of the Magellanic Clouds on their orbit through the Galaxy's halo. Many physical properties of the Leading Arm, such as its mass and size, are poorly constrained because it has few…

Astrophysics of Galaxies · Physics 2020-04-22 Jacqueline Antwi-Danso , Kathleen A. Barger , L. Matthew Haffner

We study the hypothesis that high-velocity clouds (HVCs) may originate from instabilities within the gaseous phase of the Galactic halo. According to the hydrostatic equilibrium model of Kalberla & Kerp (1998), we determine the probability…

Astrophysics · Physics 2007-05-23 P. M. W. Kalberla , J. Kerp , U. Haud

We present a new technique to determine distances to major star-forming regions across the Perseus Molecular Cloud, using a combination of stellar photometry, astrometric data, and $\rm ^{12} CO$ spectral-line maps. Incorporating the Gaia…

We have imaged the extended HI environment of M31 with an unprecedented combination of high resolution and sensitivity. We detect a number of distinct High Velocity Cloud components associated with M31. A sub-set of the features within 30…

Astrophysics · Physics 2007-05-23 Robert Braun , David Thilker

In this study, we analyze molecular gas formation in neutral atomic hydrogen (HI) clouds using the latest CO data obtained from the four-beam receiver system on a 45-m telescope (FOREST) unbiased Galactic plane imaging survey with the…

We present 21 cm observations of a 5 x degree region in the Virgo cluster, obtained as part of the Arecibo Galaxy Environment Survey. 13 cluster members are detected, together with 36 objects in the background. We compare and contrast the…

Astrophysics of Galaxies · Physics 2015-06-11 R. Taylor , J. I. Davies , R. Auld , R. F. Minchin , R. Smith