Discovery of new non-thermal radio sources in the W40 region
ATel #4236; L. Pirogov (IAP RAS), I. Zinchenko (IAP RAS), D. K. Ojha (TIFR), S. K. Ghosh (NCRA, TIFR)
on 3 Jul 2012; 15:33 UT
Credential Certification: Lev Pirogov (pirogov@appl.sci-nnov.ru)
Subjects: Radio, AGN, Quasar
We report the discovery of new compact radio sources in the neighbourhood of star-forming complex W40. Observations centered at the position (J2000) 18h31m15.75s -02d06m49.3s were carried out with the GMRT array on November 15 and 18, 2011 at 1280 MHz and 610 MHz, respectively. The synthesised beams at 1280 MHz and 610 MHz are 2.60''x2.25'' and 5.24''x4.79'', respectively. The primary beams at these frequencies are about 26' and 43', respectively. An extended emission region and point sources associated with a cluster that excites the W40 HII region have been detected in the central part of the area observed. Recently, this cluster of point sources has been studied at 3.6 cm with VLA (Rodriguez et al., 2010, ApJ, 140, 968). In addition, we have detected several new point sources at the distances of several arcminutes from the center. No associations with known objects from the SIMBAD database have been found for these sources. All the new sources are detected at both frequencies. The most intensive sources (PS0, PS5(1+2) and PS8) have associations on the 150 MHz maps of the TIFR GMRT Sky Survey (TGSS)(maps provided to us by the TGSS team; to appear in a future data release of TGSS at their website http://tgss.ncra.tifr.res.in ). The source coordinates and fluxes are given below. The 150 MHz fluxes are also provided by the TGSS team.
| Source | RA(2000) | Dec(2000) | F(1280) | F(610) | F(150) |
| | | | (mJy) | (mJy) | (mJy) |
| PS0 | 18h31m13.22s | -02d10m11.35s | 101.0(0.1) | 167.8(0.4) | 874(12) |
| PS1 | 18h31m36.99s | -01d53m10.40s | 10.3(0.7) | 22.0(0.4) |
| PS3 | 18h31m18.70s | -01d54m55.57s | 5.2(0.7) | 10.6(0.3) |
| PS5(1) | 18h31m02.40s | -01d57m05.42s | 14.4(0.1) | 33.0(0.3) | 224(13) (The total value for PS5(1)+PS5(2)) |
| PS5(2) | 18h31m02.26s | -01d56m58.70s | 12.9(0.1) | 39.4(0.3) |
| PS6 | 18h30m34.16s | -01d56m36.90s | 2.4(0.6) | 12.5(0.4) |
| PS7 | 18h30m53.28s | -02d07m31.64s | 2.2(0.4) | 4.2(0.3) |
| PS8 | 18h30m15.32s | -02d19m22.00s | 6.1(0.7) | 45.7(0.7) | 248(12) |
| PS9 | 18h30m44.12s | -02d01m45.64s | 2.1(0.6) | 4.0(0.3) |
Deconvolved sizes of the strongest source PS0 are 1.15''(0.04) and 1.85''(0.05) at 1280 MHz and 610 MHz, respectively. For all the sources F(1280)<F(610) or F(1280)<F(610)<F(150). Their spectral indices are lower than -0.1 implying non-thermal nature of the sources. In order for better understanding the nature of the discovered sources the studies in other frequency ranges are needed.
