J/A+A/638/A29 3C388 145, 392, 614, 1400 and 4850MHz images (Brienza+, 2020)
Radio spectral properties and jet duty cycle in the restarted radio galaxy
3C388.
Brienza M., Morganti R., Harwood J., Duchet T., Rajpurohit K., Shulevski A.,
Hardcastle M.J., Mahatma V., Godfrey L.E.H., Prandoni I., Shimwell T.W.,
Intema H.
<Astron. Astrophys. 638, A29 (2020)>
=2020A&A...638A..29B 2020A&A...638A..29B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; Radio continuum
Keywords: galaxies : active - radio continuum : galaxy - individual: 3C388
Abstract:
Restarted radio galaxies represent a unique tool to investigate the
duty cycle of the jet activity in Active Galactic Nuclei. Due to a
sharp discontinuity of the GHz spectral index distribution within its
lobes, the radio galaxy 3C388 has for long being claimed to be a
peculiar example of AGN with multi-epoch activity
The goal of this work is to perform for the first time a spatially
resolved study of the radio spectrum of this source down to
MHz-frequencies, in order to investigate its radiative age and
constrain its duty cycle.
We have used new low frequency observations at 144MHz performed with
the Low Frequency Array and at 350MHz performed with the Very Large
Array combined with archival data at higher frequencies (614, 1400,
4850MHz). Results. We find that the spectral indices in the lower
frequency range 144-614MHz have flatter values
(αlow∼0.55-1.14) than those observed in the higher frequency
range 1400-4850MHz (αhigh∼0.75-1.57) but follow the same
distribution across the lobes, with a systematic steepening towards
the edges. However, the spectral shape throughout the source is not
uniform and often deviates from standard models. This suggests that
mixing of different particle populations is occurring, although it
remains difficult to understand whether this is caused by
observational limitations (insufficient spatial resolution and/or
projection effects) or by the intrinsic presence of multiple particle
populations, possibly related to the two different outbursts.
By using single-injection radiative models we compute that the total
source age is ≲80Myr and that the duty cycle is about
ton/ttot∼60%, which is enough to prevent the intracluster medium
from cooling according to X-ray estimates. While to date the radio
spectral distribution of 3C388 remains a rare case among radio
galaxies, multi-frequency surveys performed with new generation
instruments will soon allow us to investigate whether more sources
with the same characteristics do actually exist.
Description:
We used a recent dataset obtained on June 26th, 2019, as part of the
LOFAR Two-metre Sky Survey (LoTSS, see Shimwell et al.,
2019A&A...622A...1S 2019A&A...622A...1S, Cat. J/A+A/622/A1).
We observed the source with the Very Large Array (VLA) in A
configuration on July 28th 2015 using the P-band receiver centered at
350MHz.
We reprocessed the data used by Roettiger et al. (1994ApJ...421L..23R 1994ApJ...421L..23R)
at 1400MHz and 4850MHz. The data consists of observations in B array
at 1400MHz and in C array at 4850MHz. The target was observed for 7
hours at 1400MHz and for 5 hours at 4850MHz.
The target was observed with the legacy Giant Metrewave Radio
Telescope (GMRT) at 614MHz and 240MHz in dual frequency mode and
data were published in Lal et al. (2008MNRAS.390.1105L 2008MNRAS.390.1105L). The
observations were performed on July 29th and 30th, 2005.
3C388 was observed by Chandra on February 9th and 29th, 2004 with the
ACIS-I detector (obs ID 4756 and 5295, respectively) and the data were
published by Kraft et al. (2006ApJ...639..753K 2006ApJ...639..753K).
Objects:
--------------------------------------------------
RA (2000) DE Designation(s)
--------------------------------------------------
18 44 02.42 +45 33 29.8 3C 388 = LEDA 62332
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 121 5 List of fits images
fits/* . 5 Individual fits images
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See also:
J/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source catalog (Shimwell+, 2019)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
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- 59 F8.3 MHz Freq Observed frequency
61- 64 I4 Kibyte size Size of FITS file
66- 96 A31 --- FileName Name of FITS file, in subdirectory fits
98-121 A24 --- Title Title of the FITS file
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Acknowledgements:
Marisa Brienza, m.brienza(at)ira.inaf.it
(End) Patricia Vannier [CDS] 07-Apr-2020