arXiv subjects

W. Miller Goss

Publications and source records attributed to W. Miller Goss.

6 recordsLinked to original sources

arXiv2011

Ionized Gas Kinematics and Morphology in Sgr B2 Main on 1000 AU Scales

We have imaged the Sgr B2 Main region with the Very Large Array in the BnA configuration ($θ_{beam}$ = 0\farcs13) in both the H52$α$ (45.453 GHz) radio recombination line (RRL) and 7 mm continuum emission. At a distance of 8500 pc, this spatial resolution corresponds to a physical scale of 0.005 pc ($\sim$1100 AU). The current observations detect H52$α$ emission in 12 individual ultracompact (UC) and hypercompact (HC) HII regions. Two of the sources with detected H52 $α$ emission have broad ($Δ$V$_{FWHM}\sim$50 \kms) recombination lines, and two of the sources show lines with peaks at more than one velocity. We use line parameters from the H52$α$ lines and our previous H66$α$ line observations to determine the relative contribution of thermal, pressure and kinematic broadening, and electron density. These new observations suggest that pressure broadening can account for the broad lines in some of the sources, but that gas motions (e.g. turbulence, accretion or outflow) contribute significantly to the broad lines in at least one of the sources (Sgr B2 F3).

astro-ph.GA↗

arXiv2011

Radio Astrometry Of The Triple Systems Algol And UX Arietis

We have used multi-epoch long-baseline radio interferometry to determine the proper motion and orbital elements of Algol and UX Arietis, two radio-bright, close binary stellar systems with distant tertiary components. For Algol, we refine the proper motion and outer orbit solutions, confirming the recent result of Zavala et al. (2010) that the inner orbit is retrograde. The radio centroid closely tracks the motion of the KIV secondary. In addition, the radio morphology varies from double-lobed at low flux level to crescent-shaped during active periods. These results are most easily interpreted as synchrotron emission from a large, co-rotating meridional loop centered on the K-star. If this is correct, it provides a radio-optical frame tie candidate with an uncertainty {\pm}0.5 mas. For UX Arietis, we find a outer orbit solution that accounts for previous VLBI observations of an acceleration term in the proper motion fit. The outer orbit solution is also consistent with previously published radial velocity curves and speckle observations of a third body. The derived tertiary mass, 0.75 solar masses, is consistent with the K1 main-sequence star detected spectroscopically. The inner orbit solution favors radio emission from the active K0IV primary only. The radio morphology, consisting of a single, partially resolved emission region, may be associated with the persistent polar spot observed using Doppler imaging.

astro-ph.SR↗

arXiv2010

A High-Resolution Survey of HI Absorption toward the Central 200 pc of the Galactic Center

We present an HI absorption survey of the central 250 pc of the Galaxy. Very Large Array (VLA) observations were made at 21 cm in the DnC and CnB configurations and have a resolution of ~15"(0.6 pc at the Galactic Center (GC) distance) and a velocity resolution of ~2.5 km/s. This study provides HI data with high spatial resolution, comparable with the many high resolution observations which have been made of GC sources over the past ten years. Here we present an overview of the HI absorption toward ~40 well-known continuum sources and a detailed comparison of the ionized, atomic and molecular components of the interstellar medium for the Sgr B, Radio Arc and Sgr C regions. In these well-known regions, the atomic gas appears to be closely correlated in both velocity and distribution to the ionized and molecular gas, indicating that it resides in photo-dissociation regions related to the HII regions in the GC. Toward the majority of the radio continuum sources, HI absorption by the 3-kpc arm is detected, constraining these sources to lie beyond a 5 kpc distance in the Galaxy.

astro-ph.GA↗

arXiv2002

Investigation of the large-scale neutral hydrogen near the supernova remnant W28

The distribution and kinematics of neutral hydrogen have been studied in a wide area around the supernova remnant W28. A 2.5 x 2.5 arcdeg field centered at l = 6.5 arcdeg, b = 0 arcdeg was surveyed using the Parkes 64-m radio telescope (HPBW 14.7 arcmin at lambda 21 cm). Even though W28 is located in a complex zone of the Galactic plane, we have found different HI features which are evidence of the interaction between W28 and its surrounding gas.

astro-ph↗

arXiv2001

Australia Telescope Compact Array Observations of the OH Star Roberts 22: Resolved Images of OH Emission

We have imaged the unusual OH/IR object G 284-0.8 (Roberts 22) in the OH transitions at 1612, 1665 and 1667 MHz using the Australia Telescope Compact Array in Narrabri, NSW, Australia. The angular resolution of the OH images we present here is 6 arcsec (12000 AU at a distance of 2 kpc). We find OH emission, of extent 1.5 arcsec (2800 AU), located inside the optical bipolar flow region (size 8 arcsec) discovered by Allen et al. (1980) and imaged recently by Sahai et al. (1999) with the Hubble Space Telescope. We present astrometry of Roberts 22, providing registration of the OH and Hubble Space Telescope images to within ~0.35 arcsec. We describe the OH velocity field in Roberts 22 and discuss the kinematic properties of the source and its evolutionary status.

astro-ph↗

arXiv1996

Nomenclature of The Galactic Center Radio Sources

Since its identification as the Galactic Center, the radio source Sagittarius A has been a target of intense research. Due to the high density of sources in the Galactic Center and differing observing techniques, the nomenclature of sources in this region has changed over the years, with sources having several names, as well as the same names being used for different sources. We review this historical evolution in the context of current and previous scientific discussions, and outline how, why and when some of the commonly accepted names of Galactic Center sources were established.

astro-ph↗