J/A+A/648/A9 Lockman Hole Apertif map at 1.4GHz (Morganti+, 2021)
The best of both worlds: combining LOFAR and Apertif to derive resolved radio
spectral index images.
Morganti R., Oosterloo T.A., Brienza M., Jurlin N., Prandoni I., Orru E.,
Shabala S.S., Adams E.A.K., Adebahr B., Best P.N., Coolen A.H.W.M.,
Damstra S., de Blok W.J.G., de Gasperin F., Denes H., Hardcastle M.,
Hess K.M., Hut B., Kondapally R., Kutkin A.M., Loose G.M., Lucero D.M.,
Maan Y., Maccagni F.M., Mingo B., Moss V.A., Mostert R.I.J., Norden M.J.,
Oostrum L.C., Roettgering H.J.A., Ruiter M., Shimwell T.W., Schulz R.,
Vermaas N.J., Vohl D., van der Hulst J.M., van Diepen G.M., van Leeuwen J.,
Ziemke J.
<Astron. Astrophys. 648, A9 (2021)>
=2021A&A...648A...9M 2021A&A...648A...9M (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources
Keywords: radio continuum: galaxies - galaxies: active
Abstract:
Supermassive black holes at the centres of galaxies can cycle through
periods of activity and quiescence. Characterising the duty cycle of
active galactic nuclei (AGN) is crucial for understanding the impact
of the energy they release on the host galaxy. For radio AGN, this can
be done by identifying dying (remnant) and restarted radio galaxies
from their radio spectral properties. Using the combination of the
images at 1400MHz produced by Apertif, the new phased-array feed
receiver installed on the Westerbork Synthesis Radio Telescope, and
images at 150MHz provided by LOFAR, we have derived resolved spectral
index images (at a resolution of 15 arcsec) for all the sources within
an approximately 6 deg2 area of the Lockman Hole region. In this
way, we were able to select 15 extended radio sources with emission
(partly or entirely) characterised by extremely steep spectral indices
(steeper than 1.2). These objects represent cases of radio sources in
the remnant or the restarted phases of their life cycle. Our findings
confirm that these objects are not as rare as previously thought,
suggesting a relatively fast cycle. They also show a variety of
properties that can be relevant for modelling the evolution of radio
galaxies. For example, the restarted activity can occur while the
remnant structure from a previous phase of activity is still visible.
This provides constraints on the duration of the 'off' (dying)
phase. In extended remnants with ultra-steep spectra at low
frequencies, the activity likely stopped a few hundred megayears ago,
and they correspond to the older tail of the age distribution of radio
galaxies, in agreement with the results of simulations of radio source
evolution. We find remnant radio sources with a variety of structures
(from double-lobed to amorphous), possibly suggesting different types
of progenitors. The present work sets the stage for exploiting the
powerful tool of low-frequency spectral index studies of extended
sources by taking advantage of the large areas common to the LOFAR and
the Apertif surveys.
Description:
The launch of imaging surveys with the APERture Tile In Focus
(Apertif) phased-array feed (PAF) system, recently installed on the
Westerbork Synthesis Radio Telescope (WSRT) and working at 1400MHz
has provided an ideal complement to the surveys done with LOFAR at
frequencies centred on 150 and 54 MHz.
The Apertif observations of the Lockman Hole were done on April 28,
2019, during the Apertif commissioning phase.
Objects:
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RA (2000) DE Designation(s)
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10 45 00.0 +58 00 00 Lockman Hole = NAME Lockman Hole
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 125 1 Information of fits map
fits/* . 1 Fits map
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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/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 : ISOCAM 14.3µm Deep Survey in Lockman Hole
(Rodighiero+, 2004)
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/MNRAS/397/281 : Radio imaging in Lockman Hole (Ibar+, 2009)
J/ApJS/185/433 : SWIRE/Chandra survey in Lockman Hole Field (Wilkes+, 2009)
J/ApJS/198/1 : Photometry catalogs for the Lockman Hole (Fotopoulou+, 2012)
J/other/BASI/38.103 : 6Lockman Hole 10-MHz survey with GMRT. II. (Garn+, 2010)
J/A+A/551/A97 : Lockman Hole/XMM VLBI observations (Middelberg+, 2013)
J/MNRAS/462/2934 : Lockman Hole North 3GHz catalogue (Vernstrom+, 2016)
J/MNRAS/463/2997 : Lockman Hole low-frequency radio sources (Mahony+, 2016)
J/MNRAS/429/2080 : Lockman Hole 10C sources radio spectral indices
(Whittam+ 2018)
J/ApJ/856/67 : Lockman Hole VLA 3GHz radio source catalog (Cotton+, 2018)
J/MNRAS/495/4084 : Lockman Hole region 325MHz source catalog (Mazumder+, 2020)
J/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source catalog
(Shimwell+, 2019)
J/A+A/648/A2 : LOFAR Two-metre Sky Survey Deep Fields DR1 (Sabater+, 2021)
J/A+A/648/A3 : LOFAR Two-metre Sky Survey Deep Fields DR1 (Kondapally+, 2021)
J/A+A/648/A4 : LoTSS Deep Fields DR1 photometric redshifts (Duncan+, 2021)
https://lofar-surveys.org/releases.html : LOFAR Home Page
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.date Observation date
52- 58 F7.5 GHz Freq Observed frequency
60- 64 I5 Kibyte size Size of FITS file
66- 85 A20 --- FileName Name of FITS file, in subdirectory fits
87-125 A39 --- Title Title of the FITS file
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Acknowledgements:
Raffaella Morganti, morganti(at)astron.nl
References:
Brienza et al., 2017A&A...606A..98B 2017A&A...606A..98B, Search and modelling of remnant radio
galaxies in the LOFAR Lockman Hole field
Jurlin et al., 2020A&A...638A..34J 2020A&A...638A..34J, The life cycle of radio galaxies in the
LOFAR Lockman Hole field
Shabala et al., 2020MNRAS.496.1706S 2020MNRAS.496.1706S, The duty cycle of radio galaxies revealed
by LOFAR: remnant and restarted radio source populations in the Lockman Hole
Tasse et al., Paper I 2020A&A...248A...1T 2020A&A...248A...1T
Sabater et al., Paper II 2020A&A...248A...2S 2020A&A...248A...2S, Cat. J/A+A/648/A2
Kondapally et al., Paper III 2020A&A...248A...3S 2020A&A...248A...3S, Cat. J/A+A/648/A3
Duncan et al., Paper IV 2020A&A...248A...4D 2020A&A...248A...4D, Cat. J/A+A/648/A4
Mandal et al., Paper V 2020A&A...248A...5M 2020A&A...248A...5M
Smith et al., Paper VI 2020A&A...248A...6S 2020A&A...248A...6S
Gloudemans et al., Paper VII 2020A&A...248A...7G 2020A&A...248A...7G
Wang et al., Paper VIII 2020A&A...248A...8W 2020A&A...248A...8W
Hardcastle et al., Paper X 2020A&A...248A..10H 2020A&A...248A..10H
Osinga et al., Paper XI 2020A&A...248A..11O 2020A&A...248A..11O
Herrera Ruiz et al., Paper XII 2020A&A...248A..12H 2020A&A...248A..12H
Callingham et al., Paper XIII 2020A&A...248A..13C 2020A&A...248A..13C
(End) Patricia Vannier [CDS] 29-Oct-2020