GMRTK2F1LF - Giant Metrewave Radio Telescope 150-MHz Survey of Kepler K2 Field 1

Overview

This table contains some of the results from the first dedicated radio continuum survey of a Kepler K2 mission field, Field 1, covering the North Galactic Cap. The survey was wide-field, contemporaneous, multi-epoch, and multi-resolution in nature and was conducted at low radio frequencies between 140 and 200 MHz. The multi-epoch and ultra-wide-field (but relatively low-resolution) part of the survey was provided by 15 nights of observation using the Murchison Widefield Array (MWA) over a period of approximately a month, contemporaneous with K2 observations of this field. The multi-resolution aspect of the survey was provided by the low-resolution (4 arcminutes) MWA imaging, complemented by non-contemporaneous but much higher resolution (20 arcseconds) observations using the Giant Metrewave Radio Telescope (GMRT). The survey is, therefore, sensitive to the details of radio structures across a wide range of angular scales. Consistent with other recent low radio frequency surveys, no significant radio transients or variables were detected in the survey. The resulting source catalogs consist of 1,085 and 1,468 detections in the two MWA observation bands (centered at 154 and 185 MHz, respectively) and 7,445 detections in the GMRT observation band (centered at 148 MHz), over 314 square degrees. The survey is presented as a significant resource for multi-wavelength investigations of the more than 21,000 target objects in the K2 field. In the reference paper, the authors briefly examined their survey data against K2 target lists for dwarf star types (stellar types M and L) that had been known to produce radio flares.

This survey included contemporaneous observations of the K2 Field 1 made with the MWA and historical (from 2010-2012) observations made with the Tata Institute of Fundamental Research (TIFR) GMRT Sky Survey (TGSS; see http://tgss.ncra.tifr.res.in/), via the TGSS Alternative Data Release 1 (ADR1; Intema et al. 2016, in prep.). The MWA and GMRT are radio telescopes operating at low radio frequencies (approximately 140-200 MHz for the work described here). The K2 mission Campaign 1 was conducted on Field 1 (center at J2000.0 coordinates RA of 11:35:45.51 and Dec of +01:25:02.28;), covering the North Galactic Cap, between 2014 May 30 and August 21.

A full survey of the radio sky at 150 MHz as visible from the GMRT was performed within the scope of the PI-driven TGSS project between 2010 and early 2012, covering the declination range from -55 to +90 degrees. Summarizing the observational parameters as given on the TGSS project website (http://tgss.ncra.tifr.res.in/150MHz/obsstrategy.html), the survey consists of more than 5,000 pointings on an approximate hexagonal grid. Data were recorded in full polarization (RR, LL, RL, LR) every 2 seconds, in 256 frequency channels across 16 MHz of bandwidth (140-156 MHz). Each pointing was observed for about 15 minutes, split over three or more scans spaced in time to improve UV-coverage. Typically, 20-40 pointings were grouped together into single night-time observing sessions, bracketed and interleaved by primary (flux density and bandpass) calibrator scans on 3C48, 3C147, and/or 3C286. Interleaving secondary (phase) calibrator scans on a variety of standard phase calibrators were also included, but were typically too faint to be of significant benefit at these frequencies. The single epoch TGSS image was processed in the same way as each of the MWA images using the background and noise characterization source finding techniques outlined in Section 3.1.3 of the reference paper. A source catalog was produced from the single TGSS image. For the high-resolution TGSS images, the sources were resolved in some cases and so morphology information is included in this catalog.

The final set of MWA images after source finding yielded a total of 1,085 radio sources at 154 MHz, and 1,471 sources at 185 MHz over 314 square degrees, at an angular resolutions of ~4 arcminutes: this MWA catalog is contained in the HEASARC table MWAK2F1HFC, which thus has 1,085 + 1,471 = 2,556 entries. The GMRT images, after source finding, yielded a total of 7,445 radio sources over the same field, at an angular resolution of ~0.3 arcminutes: this GMRT source catalog is contained in the present HEASARC table. Thus, the overall survey covers multiple epochs of observation, spans approximately 140-200 MHz, is sensitive to structures on angular scales from arcseconds to degrees, and the MWA part is contemporaneous with the K2 observations of the field over a period of approximately one month.

Catalog Bibcode

2016AJ....152...82T

References

A multi-resolution, multi-epoch low radio frequency survey of the Kepler K2
mission campaign 1 field.
    Tingay S.J., Hancock P.J., Wayth R.B., Intema H., Jagannathan P., Mooley K.
   <Astron. J., 152, 82-82 (2016)>
   =2016AJ....152...82T    (SIMBAD/NED BibCode).

Provenance

This table was created by the HEASARC in December 2016 based on CDS Catalog J/AJ/152/82 file table3.dat (the GMRT Kepler 2 Field 1 source catalog).

Parameters

Source_Number
A unique identification number for each radio source in this catalog. The ID numbers given in this table for sources detected by the GMRT at 148 MHz are completely independent from those used in the MWA catalog of the sources detected in the Kepler 2 Field 1 at 154 and 185 MHz (available in the HEASARC database as the MWAK2F1LFC table).

Name
The name of the radio source, using the '[THW2016] GMRT' prefix (for Tingay, Hancock, Wayth 2016 Giant Metrewave Radio Telescope) and the source number, e.g., '[THW2016] GMRT 6'. These names were created by the HEASARC in the style recommended by the Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10^-4 degrees (0.36 arcseconds) in the original table.

RA_Error
The mean error in the Right Ascension of the radio source, in degrees.

Dec
The Declination of the radio source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10^-4 degrees (0.36 arcseconds) in the original table.

Dec_Error
The mean error in the Declination of the radio source, in degrees.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Flux
The flux density of the radio source, in mJy (converted by the HEASARC from the Jy units used in the original reference). The HEASARC assumes that since the original units specified therein were Jy rather than Jy/beam that this is an integrated rather than a peak flux density.

Flux_Error
The uncertainty in the flux density of the radio source, in mJy (converted by the HEASARC from the Jy units used in the original reference).

Major_Axis
The major axis of the best-fit elliptical Gaussian to the radio source, in arcseconds.

Major_Axis_Error
The uncertainty in the major axis of the best-fit elliptical Gaussian model of the radio source, in arcseconds. When the source finding algorithm cannot assign a meaningful error for the morphology parameters (in the low signal to noise detections), a null value is entered into the relevant uncertainty.

Minor_Axis
The minor axis of the best-fit elliptical Gaussian to the radio source, in arcseconds.

Minor_Axis_Error
The uncertainty in the minor axis of the best-fit elliptical Gaussian model of the radio source, in arcseconds. When the source finding algorithm cannot assign a meaningful error for the morphology parameters (in the low signal to noise detections), a null value is entered into the relevant uncertainty.

Position_Angle
The position angle of the best-fit elliptical Gaussian to the radio source, in degrees.

Position_Angle_Error
The uncertainty in the position angle of the best-fit elliptical Gaussian to the radio source, in degrees. When the source finding algorithm cannot assign a meaningful error for the morphology parameters (in the low signal to noise detections), a null value is entered into the relevant uncertainty.

Contact Person

Questions regarding the GMRTK2F1LF database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:28:15 EDT