OH masers trace diverse physical processes, from the expanding envelopes around evolved stars to star-forming regions or supernovae remnants. Providing a survey of the ground-state OH maser transitions in the northern hemisphere inner Milky Way facilitates the study of a broad range of scientific topics. We want to identify the ground-state OH masers at 18 cm wavelength in the area covered by "The HI/OH/Recombination line survey of the Milky Way (THOR)". We will present a catalogue of all OH maser features and their possible associated environments. The THOR survey covers longitude and latitude ranges of 14.3{deg}<l<66.8{deg} and b<+/-1.25{deg}. All OH ground state lines ^2^{PI}_3/2_(J=3/2) at 1612 (F=1-2), 1665 (F=1-1), 1667 (F=2-2) and 1720MHz (F=2-1) have been observed, employing the Very Large Array (VLA) in its C configuration. The spatial resolution of the data varies between 12.5" and 19", the spectral resolution is 1.5km/s, and the rms sensitivity of the data is 10mJy/beam per channel. We identify 1585 individual maser spots (corresponding to single spectral features) distributed over 807 maser sites (regions of size ~10^3^-10^4^AU). Based on different criteria from spectral profiles to literature comparison, we try to associate the maser sites with astrophysical source types. Approximately 51% of the sites exhibit the double-horned 1612MHz spectra typically emitted from the expanding shells of evolved stars. The separations of the two main velocity features of the expanding shells typically vary between 22 and 38km/s. In addition to this, at least 20% of the maser sites are associated with star-forming regions. While the largest fraction of 1720MHz maser spots (21 out of 53) is associated with supernova remnants, a significant fraction of the 1720MHz maser spots (17) are also associated with star-forming regions. We present comparisons to the thermal ^13^CO(1-0) emission as well as to other surveys of class II CH_3_OH and H_2_O maser emission. The catalogue attempts to present associations to astrophysical sources where available, and the full catalogue is available in electronic form. This OH maser catalogue presents a unique resource of stellar and interstellar masers in the northern hemisphere. It provides the basis for a diverse range of follow-up studies from envelopes around evolved stars to star-forming regions and Supernova remnants.
We present the final results from the Arecibo Observatory OH megamaser survey. We discuss in detail the properties of the remaining 18 OH megamasers detected in the survey, including three redetections. We place upper limits on the OH emission from 85 nondetections and examine the properties of 25 ambiguous cases for which the presence or absence of OH emission could not be determined. The complete survey has discovered 50 new OH megamasers (OHMs) in (ultra)luminous infrared galaxies ([U]LIRGs), which doubles the sample of known OHMs and increases the sample at z>0.1 sevenfold.
Using 766 compact objects found in a systematic survey of the Galactic plane in the 1612MHz masing OH line, new light is cast on the IR properties of evolved stars on the thermally pulsing asymptotic giant branch (AGB) and beyond. The usual mid-IR selection criteria for post-AGB, based on IRAS colors, largely fail to distinguish early post-AGB stages. A two-color diagram from much narrower band MSX flux densities, with bimodal distributions, provides a better tool for doing this. Four mutually consistent selection criteria for OH-masing red protoplanetary nebulae are given, as well as two for early post-AGB masers and one for all post-AGB masers including the earliest ones. All these criteria miss a group of blue, high-outflow post-AGB sources with 60{mu}m excess; these will be discussed in detail in Paper II (Sevenster, 2002AJ....123.2772S). The majority of post-AGB sources show regular double-peaked spectra in the OH 1612MHz line, with fairly low outflow velocities, although the fractions of single peaks and irregular spectra may vary with age and mass. The OH flux density shows a fairly regular relation with the stellar flux and the envelope optical depth, with the maser efficiency increasing with IRAS color R_21_. The OH flux density is linearly correlated with the 60{mu}m flux density.
Optical astrometry of Benchmark radio sources. III
Short Name:
J/A+AS/115/75
Date:
21 Oct 2021
Publisher:
CDS
Description:
Optical positions, relative to the International Reference Stars catalogue (IRS), and therefore in the system of the FK5, have been obtained for the optical counterparts of 35 extragalactic radio sources south of {delta}~+3deg. Many of these sources are being considered as possible Benchmark objects for the establishment of a quasi-inertial unified radio/optical reference frame. Precision levels better than 0.2" in both coordinates were achieved. A comparison with VLBI radio positions available for these sources is presented. We give evidence for a possible offset in RA between the radio and optical reference frames.
Results are presented of deep identifications of 40 steep spectrum radio sources detected on RATAN-600 in an area ~100deg in the 'Kholod' experiment and then studied using the VLA. Candidates for optical objects responsible for the radio emission were found for 32 sources. With the exception of a few quasars and objects with ill-defined morphology, a large fraction of the radio sources are associated either with gE galaxies or with galaxies of an unknown nature.
Two hundred and forty radio sources that are common for RC (RATAN-600) and UTRAO (VLA, Douglas J.N.+, 1980PAUTx..17....1D) catalogs were identified on the enlarged prints of the Palomar Sky Atlas. The number of identified radio sources with flux density between 15 and 300 mJy drops with decreasing flux density in the centimeter wavelength range.
Optical identifications, magnitudes, and redshifts have been compiled for the 185 radio sources of the S5 catalogue, representing its current optical identification status. Reliable optical counterparts are found for more than 75% of the sources, nearly 50% of which have measured redshifts. Our tabulation also includes radio positions, radio fluxes, and radio spectral indices. References to other catalogues and detailed supplementary notes are given for a large fraction of the sources.
An update of the optical identification status of the S4 radio source catalogue is presented. An extensive literature search has been made to gather the types of the optical counterparts, their magnitudes and redshifts. As far as possible, references to other optical catalogues are given for these data, which are often supplemented by more detailed notes on individual sources. Accurate radio positions taken from the literature are given for a large fraction of the sources.
Optical identifications have been sought for 304 radio sources from the declination -20{deg} region of the first Molonglo deep survey. Optical objects have been measured using the Palomar sky survey to an accuracy of 1 arcsec and magnitude estimates are to 0.4mag. Finding charts are given for all fields with optical objects within +/-2{sigma} of the radio position. Sixteen QSOs have been confirmed (details have been reported elsewhere) amongst the blue stellar-like objects and spectroscopy is complete to m_o_=19.5. The mean magnitude of the QSOs is 19.2 and the mean redshift is 1.34. A study of the background densities of objects indicates that about half of the remaining blue stellar-like objects are QSOs and about 80 per cent of the galaxies are associated with the radio emission. The QSOs are amongst the fainter and the bluer of the blue stellar-like objects. There is no evidence for any average offset between the radio and optical positions.
CCD images of the fields of 115 radio sources from the 1Jy, S4 and S5 catalogues are presented. New optical counterparts have been found for a total of 34 sources, a large fraction of which had as yet only been described as empty fields on Sky Survey Plates. Of the 54 radio sources with previously published identifications, 50 optical counterparts have been confirmed while for 4 sources new identifications are proposed. R band magnitudes, derived from the CCD images, are provided for all but a few identified optical counterparts. The fields at the positions of 27 radio sources are still empty down to a limiting magnitude of at least m_R_=22mag, requiring much deeper optical as well as additional infrared images for establishing their optical counterparts.
