J/ApJS/257/30 BL Lac morphologies with LoTSS-DR2 144MHz data (Mooney+, 2021)
Characterising the extended morphologies of BL Lacertae objects at 144MHz with
LOFAR.
Mooney S., Massaro F., Quinn J., Capetti A., Baldi R.D., Gurkan G.,
Hardcastle M.J., Horellou C., Mingo B., Morganti R., O'Sullivan S.,
Pajdosz-Smierciak U., Pandey-Pommier M., Rottgering H.
<Astrophys. J. Suppl. Ser., 257, 30 (2021)>
=2021ApJS..257...30M 2021ApJS..257...30M
ADC_Keywords: BL Lac objects; Radio sources; Morphology; Redshifts; Surveys;
Gamma rays
Keywords: BL Lacertae objects ; Radio source catalogs
Abstract:
We present a morphological and spectral study of a sample of 99 BL Lac
objects using the LOFAR Two-Metre Sky Survey Second Data Release
(LDR2). Extended emission has been identified at gigahertz frequencies
around BL Lac objects, but with LDR2 it is now possible to
systematically study their morphologies at 144MHz, where more diffuse
emission is expected. LDR2 reveals the presence of extended radio
structures around 66/99 of the BL Lac nuclei, with angular extents
ranging up to 115", corresponding to spatial extents of 410kpc. The
extended emission is likely to be both unbeamed diffuse emission and
beamed emission associated with relativistic bulk motion in jets. The
spatial extents and luminosities of the extended emission are
consistent with the unification scheme for active galactic nuclei,
where BL Lac objects correspond to low-excitation radio galaxies with
the jet axis aligned along the line of sight. While extended emission
is detected around the majority of BL Lac objects, the median
144-1400MHz spectral index and core dominance at 144MHz indicate that
the core component contributes ∼42% on average to the total
low-frequency flux density. A stronger correlation was found between
the 144MHz core flux density and the γ-ray photon flux (r=0.69)
than between the 144MHz extended flux density and the γ-ray
photon flux (r=0.42). This suggests that the radio-to-γ-ray
connection weakens at low radio frequencies because the population of
particles that give rise to the γ-ray flux are distinct from the
electrons producing the diffuse synchrotron emission associated with
spatially extended features.
Description:
The Low Frequency Array (LOFAR) is conducting a
high-angular-resolution, highly sensitive survey of the Northern
Hemisphere sky at 144MHz (LoTSS; the LOFAR Two-Metre Sky Survey;
Shimwell+ 2017, J/A+A/598/A104), with more than 21% of the sky
observed to date.
We present LoTSS Second Data Release (LDR2;
Shimwell+, 2022, J/A+A/659/A1) data for a sample of BL Lac objects
from the blazar catalog Roma-BZCAT (BZBs; Massaro+ 2015, VII/274) and
measure the spatial extents, core dominances, and spectral indices to
characterize the diffuse emission.
A ΛCDM cosmological model is used in this paper with h=0.70,
{Ometa}m=0.26, and {Ometa}Λ=0.74, where
H0=100h.km/s.Mpc-1 is the Hubble constant.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 387 99 Details of the Roma-BZCAT BL Lac (BZB) sample
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
VII/274 : The Roma BZCAT - 5th edition (Massaro+, 2015)
J/MNRAS/323/757 : Deep X-Ray Radio Blazar Survey (DXRBS). II. (Landt+, 2001)
J/ApJS/171/61 : All-Sky Survey of Flat-Spectrum Radio Sources (Healey+, 2007)
J/ApJ/741/30 : Radio/γ-ray correlation in AGN (Ackermann+, 2011)
J/ApJ/740/98 : Synchroton peak for blazars & radio galaxies (Meyer+, 2011)
J/MNRAS/421/1569 : Properties of 18286 SDSS radio galaxies (Best+, 2012)
J/ApJS/207/4 : Unidentified γ-ray sources. III. Radio (Massaro+, 2013)
J/ApJS/213/3 : Low-frequency flat spectrum sources (LORCAT) (Massaro+, 2014)
J/A+A/588/A141 : The MWA view of Fermi blazars (Giroletti+, 2016)
J/A+A/598/A104 : LOFAR Two-metre Sky Survey (Shimwell+, 2017)
J/MNRAS/474/5008 : Radio spectral index 147-1400MHz (de Gasperin+, 2018)
J/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source cat. (Shimwell+, 2019)
J/ApJS/247/33 : The Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
J/ApJ/892/105 : 4th catalog of Fermi LAT-detected AGNs (4LAC) (Ajello+, 2020)
J/ApJ/900/L34 : BL Lac objects and radio galaxies comparison (Massaro+, 2020)
J/ApJS/247/71 : Large-scale environment of radio gal. II. (Massaro+, 2020)
J/A+A/648/A104 : LOFAR LBA Sky Survey. I. (de Gasperin+, 2021)
J/A+A/659/A1 : LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name (JHHMM+DDMM)
12- 33 A22 --- LoTSS LoTSS DR2 name (ILTJHHMMSS.ss+DDMMSS.s)
35- 38 A4 --- --- [5BZB]
40- 49 A10 --- 5BZB BZCAT v5 (Cat. VII/274) name (JHHMM+DDMM;
<[MML2015] 5BZB JHHMM+DDMMa> in Simbad)
51- 54 A4 --- --- [4FGL]
56- 67 A12 --- 4FGL 4FGL name (JHHMM.m+DDMM)
69- 79 F11.7 deg RAdeg [11.98/356] Right Ascension (J2000)
81- 90 F10.7 deg DEdeg [18.6/67.7] Declination (J2000)
92- 98 F7.5 --- zspec [0.03/0.761] Spectroscopic Redshift
100-103 A4 --- Class Class, resolved ("rBZB": 66 occurrences)
or "uBZB"=unresolved BZB
105-111 A7 --- Morph Morphology ("Beamed", "Compact" or
"Diffuse")
113-132 F20.15 mJy Stot [0.8/2162] Integrated flux density
at 144MHz from LDR2
134-152 F19.15 mJy e_Stot [0.16/433] Uncertainty in Stot
154-158 A5 --- Res Flag indicating source resolved ("TRUE")
160-173 E14.7 ph/cm2/s SGeV [7.6e-11/3.8e-8]? γ-ray flux
from 4LAC
175-187 E13.8 ph/cm2/s e_SGeV [2.3e-11/3.6e-10]? Uncertainty in SGeV
189-206 F18.15 --- alpha [-1.26/1.95] Spectral index,
144-1400MHz with LDR2 and NVSS
208-224 F17.15 --- e_alpha [0.002/0.4] Uncertainty in alpha
226-242 F17.15 --- rho144 [0.02/2.97]? Core dominance at 144MHz
(see Section 3.2)
244-260 F17.15 --- e_rho144 [0.004/0.6]? Uncertainty in rho144
262-266 A5 --- Limit Flag indicating spatial/angular
extents are upper limits ("TRUE")
268-285 F18.14 kpc D [3.7/411] Spatial extent
287-305 F19.15 kpc e_D [0.002/136] Uncertainty in D
307-324 F18.14 arcsec phi [2.68/116] Angular extent
326-343 F18.15 arcsec e_phi [0.002/21] Uncertainty in phi
345-365 E21.15 W/Hz L144 [5.8e+23/6.5e+26] Radio luminosity
367-387 E21.15 W/Hz e_L144 [1.1e+23/1.3e+26] L144 uncertainty
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Feb-2022