J/A+A/691/A287 LoTSS DR2 restarted radio galaxies in HETDEX field (Nair+, 2024)
Core prominence as a signature of restarted jet activity in the LOFAR
radio-galaxy population.
Nair D.G., Morganti R., Brienza M., Mingo B., Croston J.H., Jurlin N.,
Shimwell T.W., Callingham J.R., Hardcastle M.J.
<Astron. Astrophys. 691, A287 (2024)>
=2024A&A...691A.287N 2024A&A...691A.287N (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Radio sources
Keywords: surveys - galaxies: active - radio continuum: galaxies
Abstract:
Recurrent phases of dormancy and activity occur in the supermassive
black holes in active galactic nuclei. Characterizing the duty cycles
of this process is crucial in understanding the impact of the energy
released on the host galaxies, and their evolution. However, it is
challenging to identify sources in the quiescent and restarted phases.
Our goal is to identify and characterize a substantial sample of radio
galaxies in a restarted phase and explore the idea of core prominence
as a signature of restarted activity. We expand our prior study of
identifying restarted sources from a 30deg2 area in the Lockman Hole
to a larger 424deg2 region in the Hobby-Eberly Telescope Dark Energy
Experiment (HETDEX) extragalactic field using a sample of
core-dominated radio galaxies selected visually.
We used the 144 MHz LOFAR survey images of the HETDEX field to
identify galaxies with restarting jets. By assessing diverse selection
criteria including radio core dominance along with low surface
brightness extended emission, spectral index properties (e.g., steep
or inverted spectra of a core and an ultra-steep spectrum of extended
emission), and morphology, we found 69 candidate restarted radio
galaxies in the HETDEX field.
The restarted candidates show a diverse intrinsic morphology, spanning
from FRI, FRII, core-with-halo, to asymmetric forms, feasibly
proposing different progenitors. Within these 69 restarted candidates,
we identified a subset of nine galaxies characterized by ultra-steep
spectrum extended emission combined with high radio core prominence,
representing previous and current epochs of jet activity. We interpret
our findings for this small subset as support for a model in which the
switch-on and switch-off mechanism happens with a relatively fast duty
cycle in these sources. We found a peculiar case, J131728.61+561544.8,
which appears to have altered its jet orientation, possibly due to
changes in the angular momentum or spin of its supermassive black
hole, interactions with surrounding material, and/or variations in the
magnetic flux threading its accretion disk.
The restarted candidates span a range of radio luminosities from
log10(L144MHz/(W/Hz)=23.24 to log10(L144MHz/(W/Hz)=26.80, and
linear sizes between 88 and 1659 kpc at 144 MHz, with 16 sources
identified as giant radio galaxies with sizes exceeding 0.7Mpc. The
total stellar content of restarted sources is consistent with massive
elliptical galaxies, with at least 17% inhabiting cluster
environments. Our findings at z<0.4 suggest that many restarting radio
galaxies are not found in rich cluster environments, aligning with the
environmental properties of the broader radio-galaxy population. The
present study confirms the core prominence as an effective parameter
for selecting candidate restarted radio sources.
Description:
Supermassive black holes in active galactic nuclei undergo recurrent
phases of dormancy and activity, making it crucial to characterize
their duty cycles to understand their impact on host galaxies.
We identified and characterized 69 candidate restarted radio galaxies
in a 424deg2 region of the HETDEX extragalactic field, using diverse
selection criteria, including radio core dominance, low surface
brightness extended emission, spectral index properties, and
morphology, with 144 MHz LOFAR Two-meter Sky Survey (LoTSS) Data
Release 2 images.
The tables provide a list of the 69 candidate restarted radio galaxies
identified in the HETDEX field using LoTSS DR2, along with their flux
densities and other properties (tables A1 and A2). A list of excluded
sources from the restarted candidate sample, including their flux
densities and other properties, is also provided (tables A3 and A4).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 103 69 List of 69 candidate restarted radio galaxies
tablea2.dat 89 69 Flux densities for candidate restarted galaxies
tablea3.dat 112 30 Excluded sources from restarted galaxy sample
tablea4.dat 89 30 Flux densities of excluded sources
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Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- No [1/69] Sequential source number
3- 4 A2 --- n_No [*+ ] Note (1)
7- 25 A19 --- Source Source name (J2000 coordinates)
26- 27 A2 --- n_Source [*+ ] Note (1)
29- 33 F5.3 --- z Redshift
35 A1 --- n_z [sp] Redshift spectroscopic (s)
or photometric (p)
38- 43 F6.2 mJy Sint144MHz Integrated flux density at 144MHz
45 A1 --- l_CP1.4GHz Limit flag on CP1.4GHz
46- 49 F4.2 --- CP1.4GHz Radio core prominence at 1.4GHz
50 A1 --- n_CP1.4GHz [+] Note (2)
52- 57 F6.2 mJy/arcmin2 SB144MHz Surface brightness at 144MHz
59 A1 --- l_alphacore Limit flag on alphacore
60- 64 F5.2 --- alphacore Core spectral index
66- 70 F5.3 --- e_alphacore ? Core spectral index error
72 A1 --- l_alphaext Limit flag on alphaext
73- 77 F5.2 --- alphaext Extended emission SI
79- 83 F5.3 --- e_alphaext ? Extended emission SI error
85- 97 A13 --- Selection Criteria for restarted galaxies (3)
100-103 F4.2 --- CP144MHz Radio core prominence at 144MHz
--------------------------------------------------------------------------------
Note (1): Notes as follows:
* = denotes ultra-steep spectrum galaxies
+ = denotes sources with broad emission lines in their SDSS spectra
Note (2): Note as follows:
+ = denotes values poorly constrained
Note (3): Selection criteria as follows:
CP+SB = high radio core prominence + low surface brightness at 144MHz
SSC = steep spectrum core
USS = ultra-steep spectrum of extended emission
-------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- No [1/69] Sequential source number
3 A1 --- n_No [+* ] Note (1)
6- 24 A19 --- Source Source name (J2000 coordinates)
25 A1 --- n_Source [+* ] Note (1)
27- 31 F5.2 mJy Sc1400MHz Total core flux density at 1400MHz
32 A1 --- l_Sc1400MHz [+] Limit code on Sc1400MHz (2)
34- 38 F5.2 mJy Sp1400MHz Peak core flux density at 1400MHz
39 A1 --- l_Sp1400MHz [+] Limit code on Sp1400MHz (2)
41- 46 F6.2 mJy Stot1400MHz Total core flux density at 1400MHz
47 A1 --- l_Stot1400MHz [±] Limit code on Stot1400MHz (2)
49- 54 F6.2 mJy Sc144MHz Total core flux density at 144MHz
57- 62 F6.2 mJy Sp144MHz Peak core flux density at 144MHz
64- 71 E8.3 W/Hz L144MHz Radio luminosity at 144MHz
73- 79 F7.2 kpc Size Linear size at 144MHz
81- 85 F5.2 10+11Msun Mstellar ?=- Stellar mass
87 A1 --- NVSS [PYN,] NVSS detection (3)
88 A1 --- --- [,]
89 A1 --- FIRST [PYN,] FIRST detection (3)
--------------------------------------------------------------------------------
Note (1): Notes as follows:
* = denotes giant radio galaxies
+ = denotes galaxies residing in a cluster environment
Note (2): Notes as follows:
+ = value represents upper limit
- = value represents lower limit for NVSS partial detection
Note (3): NVSS and FIRST detections as follows:
Y = full detection
P = partial detection
N = no detection
-------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- No [70/99] Sequential source number
3 A1 --- n_No [+] Note (1)
5- 23 A19 --- Source Source name (J2000 coordinates)
24 A1 --- n_Source [+] Note (1)
26- 30 F5.3 --- z Redshift
32 A1 --- n_z [sp] Redshift spectroscopic (s)
or photometric (p)
34- 39 F6.2 mJy Sint144MHz Integrated flux density at 144MHz
41 A1 --- l_CP1.4GHz Limit flag on CP1.4GHz
42- 45 F4.2 --- CP1.4GHz Radio core prominence at 1.4GHz
46 A1 --- n_CP1.4GHz [+] Note (2)
48- 53 F6.2 mJy/arcmin2 SB144MHz Surface brightness at 144MHz
55 A1 --- l_alphacore Limit flag on alphacore
56- 60 F5.2 --- alphacore Core spectral index
62- 66 F5.3 --- e_alphacore ? Core spectral index error
68 A1 --- l_alphaext Limit flag on alphaext
69- 73 F5.2 --- alphaext ?=- Extended emission SI
75- 79 F5.3 --- e_alphaext ? Extended emission SI error
81-112 A32 --- Reason Reason for exclusion
--------------------------------------------------------------------------------
Note (1): Notes as follows:
+ = denotes sources with broad emission lines in their SDSS spectra
Note (2): Notes as follows:
+ = denotes values poorly constrained
-------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- No [70/99] Sequential source number
3- 4 A2 --- n_No [+* ] Note (1)
7- 25 A19 --- Source Source name (J2000 coordinates)
26- 27 A2 --- n_Source [+* ] Note (1)
29- 33 F5.2 mJy Sc1400MHz Total core flux density at 1400 MHz
34 A1 --- n_Sc1400MHz [+] Limit code on Sc1400MHz (2)
36- 40 F5.2 mJy Sp1400MHz Peak core flux density at 1400 MHz
41 A1 --- n_Sp1400MHz [+] Limit code on Sp1400MHz (2)
43- 48 F6.2 mJy Stot1400MHz Total core flux density at 1400 MHz
49 A1 --- n_Stot1400MHz [±] Limit code on Stot1400MHz (2)
51- 56 F6.2 mJy Sc144MHz Total core flux density at 144MHz
58- 62 F5.2 mJy Sp144MHz Peak core flux density at 144MHz
64- 71 E8.3 W/Hz L144MHz Radio luminosity at 144MHz
73- 79 F7.2 kpc Size Linear size at 144MHz
81- 84 F4.2 10+11Msun Mstellar ?=- Stellar mass
87 A1 --- NVSS [YNP] NVSS detections (3)
88 A1 --- --- [,]
89 A1 --- FIRST [YNP] FIRST detections (3)
--------------------------------------------------------------------------------
Note (1): Notwes as follows:
* = denotes giant radio galaxies
+ = denotes galaxies residing in a cluster environment
Note (2): Limit xode as follows:
+ = value represents upper limit
- = value represents lower limit for NVSS partial detection
Note (3): NVSS and FIRST detections as follows:
Y = full detection
P = partial detection
N = no detection
-------------------------------------------------------------------------------
Acknowledgements:
Dhanya G. Nair, dhanyagnair01(at)gmail.com
(End) Patricia Vannier [CDS] 09-Oct-2024