J/MNRAS/397/281 Radio imaging in Lockman Hole (Ibar+, 2009) ================================================================================ Deep multi-frequency radio imaging in the Lockman Hole using the GMRT and VLA. I. The nature of the sub-mJy radio population. Ibar E., Ivison R.J., Biggs A.D., Lal D.V., Best P.N., Green D.A. =2009MNRAS.397..281I ================================================================================ ADC_Keywords: Galaxies, radio ; Morphology Keywords: techniques: interferometric - galaxies: evolution - galaxies: starburst - radio continuum: galaxies Abstract: In the run up to routine observations with the upcoming generation of radio facilities, the nature of sub-mJy radio population has been hotly debated. Here, we describe multi-frequency data designed to probe the emission mechanism that dominates in these faint radio sources. Our analysis is based on observations of the Lockman Hole using the Giant Metrewave Radio Telescope (GMRT) - the deepest 610-MHz imaging yet reported - together with 1.4-GHz imaging from the Very Large Array (VLA), well matched in resolution and sensitivity to the GMRT data: {sigma}_610_MHz~15uJy/beam, {sigma}_1.4GHz_~6uJy/beam, full width at half-maximum (FWHM) ~5arcsec. The GMRT and VLA data are cross-matched to obtain the radio spectral indices for the faint radio emitters. Description: During six 12-hr sessions in 2006 February and July, we obtained data at 610MHz for three pointings (FWHM~43-arcmin) in the LH (see Table 1), separated by 11-arcmin (lockman-e, lock-3, lhex4), typically with 28 of the 30 antennas that comprise the GMRT near Pune, India. The total integration time in each field, after overheads, was 16hr. New and archival data were obtained in the same three positions using the National Radio Astronomy Observatory's (NRAO2) VLA, largely in its B configuration. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table3.dat 115 1619 *The full sample of the sources found in the Lockman Hole field at 610MHz using the GMRT table4.dat 112 1479 The 1.4-GHz catalogue -------------------------------------------------------------------------------- Note on table3.dat: Source extraction is based on peak brightness >5{sigma} the local r.m.s. and integrated flux density >3{sigma} the local r.m.s. criteria. -------------------------------------------------------------------------------- See also: J/A+A/329/482 : ROSAT Deep Survey in the Lockman Hole (Hasinger+, 1998) J/PASJ/53/445 : ASCA Deep survey in Lockman Hole Field (Ishisaki+, 2001) J/A+A/393/425 : Spectral analysis of Lockman Hole (Mainieri+, 2002) J/A+A/398/901 : VLA survey at 6 cm in the Lockman Hole (Ciliegi+, 2003) J/AJ/125/2521 : 2MASS6x survey of the Lockman Hole (Beichman+, 2003) J/AJ/128/1501 : CLASXS: X-ray catalog (Yang+, 2004) J/A+A/413/843 : Far IR survey in the Lockman Hole (Kawara+, 2004) J/A+A/427/23 : 14.3um survey in the Lockman Hole (Fadda+, 2004) J/A+A/427/773 : Lockman Hole ISOCAM 14.3{mu}m Deep Survey (Rodighiero+ 2004) J/A+A/434/801 : X-ray sources near Lockman Hole (Zappacosta+, 2005) J/A+A/444/79 : Lockman Hole brightest AGNs XMM observations (Mateos+, 2005) J/A+A/473/105 : Lockman Hole AGN variability with XMM (Mateos+, 2007) J/MNRAS/371/963 : Deep VLA survey in LH, HDFN, ELAIS N2 (Biggs+, 2007) J/A+A/487/475 : X-ray variability of AGNs in Lockman Hole (Papadakis+, 2008) J/A+A/479/283 : XMM observations of the Lockman Hole (Brunner+, 2008) J/MNRAS/387/1037 : 610-MHz survey of Lockman Hole with GMRT (Garn+, 2008) J/ApJS/185/433 : SWIRE/Chandra survey in Lockman Hole Field (Wilkes+, 2009) Byte-by-byte Description of file: table[34].dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- --- [LH610MHz1.4G] 9- 24 A16 --- Name IAU name, LH610MHzJHHMMSS.s+DDMMSS (table3) or LH1.4GHzJHHMMSS.s+DDMMSS (table4) 25 A1 --- m_Name [abc] Multiplicity index for components of double and triple sources 26- 27 I2 h RAh Right ascension (J2000.0) (1) 29- 30 I2 min RAm Right ascension (J2000.0) (1) 32- 36 F5.2 s RAs Right ascension (J2000.0) (1) 38 A1 --- DE- Declination sign (J2000.0) (1) 39- 40 I2 deg DEd Declination (J2000.0) (1) 42- 43 I2 arcmin DEm Declination (J2000.0) (1) 45- 48 F4.1 arcsec DEs [0/60] Declination (J2000.0) (1) 50- 53 I4 --- PNR Peak flux to local noise ratio 55- 58 F4.2 --- BWSC Bandwidth smearing correction (Sect. 3.2.1) 60- 64 F5.1 arcsec Size Observed maximum angular size (2) 66- 68 I3 deg PA Orientation angle (position angle) of the source with respect to North 70- 75 I6 uJy S Integrated flux density at 610MHz (table3) or 1.4GHz (table4), from AIPS routine SAD 77- 81 I5 uJy e_S rms uncertainty on Sdens 83- 84 A2 --- Class Extended or multiple classification code (3) 85- 88 A4 --- n_Class [(*2) ] Note on Class (3) 90 A1 --- l_alpha Limit flag on alpha 91- 95 F5.2 --- alpha ? Radio spectral index between 610MHz and 1.4GHz (4) 96 A1 --- --- [+] 97-100 F4.2 --- E_alpha ? Error on alpha (upper limit) 101 A1 --- --- [-] 102-105 F4.2 --- e_alpha ? Error on alpha (lower limit) 107 A1 --- f_alpha [!-] Flag for unreliable alpha (5) 109-115 A7 --- n_alpha Spectral flags (6) -------------------------------------------------------------------------------- Note (1): Position at 610MHz for table3, at 1.4GHz for table4. We note in 3.5 there is an astrometric offset between the VLA with respect to the GMRT sources, {Delta}RA=-0.60+/-0.03" and {Delta}DE=0.40+/-0.03" (mean offset in RA and DE, respectively). For double and triple systems the position is given by the brightest component. For extended sources it is given by the most central component. Note (2): These values are not deconvolved source sizes but those fitted from the observed mosaic. For single sources, this value corresponds to twice the maximum FWHM. For multiple sources, it is given by the distance between the furthest components plus the FWHMs of each of them, in the direction they define in the sky. (See Sect. 3.3). Note (3): Classification of the source as follows: S = single D = double (d1 & d2 as components) T = triple (t1, t2 & t3 as components) M = extended (Table 2). (*2) = sources extracted from the convolved, Area_beam_*sqrt(2), image (See sect. 3.4) Note (4): including the 68.3 per cent confidence range (based on the SAD flux density errors) and upper limits. Note (5): Flags as follows: - = outside cross-matching region ! = unreliable spectral index Note (6): Special flags in spectral indexes as follows: 1 = upper limit 2 = source which has split the counterpart's flux density in a relative contribution 3 = estimation which has used the original SAD extraction before multiple classification 4 = cross-matched sources separated by a distance >3" 5 = counterparts having a fitted area ratio twice bigger than the expected from point sources (A^610MHz^_source_/A^1.4GHz^_source_>2*A^610MHz^_beam_/A^1.4GHz^_beam_) 6 = estimation based on a cross-match involving more than one counterpart 7 = spectral index affected by close companion 8 = source affected by overlapping facets in the 3-D imaging approach -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 02-May-2011