The Sizes of OH (1720 MHz) Supernova Remnant Masers: MERLIN and VLBA Observations of IC443

Abstract

MERLIN and VLBA observations of the 1720 MHz maser emission from the OH molecule in the supernova remnant IC443 are presented. Based on MERLIN data with a resolution of 160 mas, the deconvolved sizes of the maser sources are in the range 90 to 180 mas (135 to 270 AU). The 12 mas resolution VLBA images show compact cores with sizes in the range 15 to 55 mas. The maser brightness temperatures are (2-34)x10^6 K for the MERLIN sources and (5-19)x10^8 K for the VLBA cores, in agreement with theory. Unlike the Zeeman Stokes V profiles observed in other OH (1720 MHz) SNR masers, single-handed circular polarization line profiles are observed in IC443 on all angular scales from 1000 to 10 mas resolution. For one line component, the observed line width is 0.24+/-0.07 km/s, compared to an estimated Doppler width of 0.49 km/s. This discrepancy in line widths can be accounted for if the maser emission arises from an elongated ellipsoidal region of masing gas.

arXiv comment22 pages, 4 figures, 3 tables, AASTex, accepted to ApJ

References in corpus (18)

• Massive star formation in 100,000 years from turbulent and pressurized molecular clouds
• Dense Gas and Star Formation: Characteristics of Cloud Cores Associated with Water Masers
• Polarization Observations of 1720 MHz OH Masers toward the Three Supernova Remnants W28, W44, and IC443
• Nonthermal Emission from a Supernova Remnant in a Molecular Cloud
• OH 1720 MHz Masers in Supernova Remnants --- C-Shock Indicators
• Shock-Excited Maser Emission from Supernova Remnants: G32.8-0.1, G337.8-0.1, G346.6-0.2, and the HB3/W3 Complex
• Shock Excited Maser Emission from the Supernova Remnant W28
• Enhanced OH in C-type shock waves in molecular clouds
• Investigation of the large-scale neutral hydrogen near the supernova remnant W28
• A Possible Site of Cosmic Ray Acceleration in the Supernova Remnant IC 443
• OH Zeeman Magnetic Field Detections Toward Five Supernova Remnants Using the VLA
• Three New Supernova Remnant OH Masers Near the Galactic Center: Evidence for Large Scale Maser Emission from Supernova Remnants
• The Sizes of 1720 MHz OH Masers: VLBA and MERLIN Observations of the Supernova Remnants W44 and W28
• Polarization of Astronomical Maser Radiation. IV. Circular Polarization Profiles
• Radio continuum emission from the central stars of M20 and the detection of a new supernova remnant near M20
• The Size of the Extragalactic Source J1801-231 and the Association of Pulsar PSR B1758-23 with the Supernova Remnant W28
• The Radial Extent and Warp of the Ionized Galactic Disk. II. A Likelihood Analysis of Radio-Wave Scattering Toward the Anticenter
• The Radial Extent and Warp of the Ionized Galactic Disk. I. A VLBA Survey of Extragalactic Sources Toward the Anticenter

Cited by in corpus (19)

• XMM-Newton observations of the supernova remnant IC 443: II. evidence of stellar ejecta in the inner regions
• XMM-Newton observations of the supernova remnant IC443: I. soft X-ray emission from shocked interstellar medium
• GBT Observations of IC 443: the Nature of OH(1720 MHz) Masers and OH Absorption
• High-resolution radio study of SNR IC443 at low radio frequencies
• OH (1720 MHz) Masers: A Multiwavelength Study of the Interaction between the W51C Supernova Remnant and the W51B Star Forming Region
• The OH (1720 MHz) Supernova Remnant Masers in W44: MERLIN and VLBA Polarization Observations
• The OH (1720 MHz) Supernova Remnant Masers in W28: MERLIN and VLBA Polarization Observations
• Excited-state OH Masers and Supernova Remnants
• Non-Zeeman Circular Polarization of CO rotational lines in SNR IC 443
• A hot molecular outflow driven by the ionized jet associated with IRAS 16562-3959
• OH (1720 MHz) Maser Search Toward the Large Magellanic Cloud
• AKARI Near-infrared Spectral Observations of Shocked H2 Gas of the Supernova Remnant IC 443
• NuSTAR Detection of a Hard X-ray Source in the Supernova Remnant - Molecular Cloud Interaction Site of IC 443
• Evidence of a Hadronic Origin for the TeV Source J1834-087
• Interstellar anatomy of the TeV gamma-ray peak in the IC443 supernova remnant
• A new look at the integrated radio/microwave continuum spectrum of Galactic supernova remnant IC443
• OH Masers and Supernova Remnants
• Extended OH(1720 MHz) Maser Emission from Supernova Remnants
• A search for 53 MHz OH line near G48.4$-$1.4 using the National MST Radar Facility