scholarly journals A BL Lacertae object at a cosmic age of 800 Myr

2021 ◽  
Author(s):  
Ekaterina Koptelova ◽  
Chorng-Yuan Hwang
Keyword(s):  
Galaxy Formation ◽  
Near Infrared ◽  
Radio Continuum ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Relativistic Jet ◽  
Bl Lac ◽  
Age Of The Universe ◽  
Stellar Masses ◽  
Bl Lacs

Abstract BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs), known as blazars, are low- and high-luminosity radio-loud Active Galactic Nuclei (AGNs) with relativistic jets pointed towards Earth (1). Evolving from FSRQs (2,3), BL Lac objects host ~109 Msun supermassive black holes (SMBHs, where Msun is the mass of the Sun) and reside preferentially in giant elliptical galaxies of stellar masses 1011-1012Msun (4-7). The known BL Lacs are relatively nearby objects found below redshift 3.6 (3,8,9). Here, we report the discovery of a BL Lac object, FIRST J233153.20+112952.11 (hereafter J2331+11), at a redshift of 6.57 corresponding to an age of the Universe of ~800 Myr. As the typical BL Lac, J2331+11 is a compact radio source with the flat power-law radio continuum, no emission lines in its near-infrared spectrum, and significant variability. The optical-to-radio continuum of J2331+11 is entirely dominated by the synchrotron emission of a relativistic jet. J2331+11 provides evidence for the shorter formation timescale of massive SMBHs with jets and bulge-dominated galaxies than that expected from the Eddington-limited growth of SMBHs and hierarchical galaxy formation. The rapid formation of BL Lacs at early cosmic epochs should have taken place in the densest regions of the early Universe.

scholarly journals The Environment of OJ 287: Nearby Galaxies and a Long Optical Jet?

1996 ◽  
Vol 175 ◽  
pp. 47-48
Author(s):  
A. Sillanpää ◽  
L. Takalo ◽  
K. Nilsson ◽  
T. Pursimo ◽  
P. Teerikorpi ◽  
...  
Keyword(s):  
Large Scale ◽  
Radio Galaxies ◽  
Trigger Mechanism ◽  
Galaxy Clustering ◽  
Bl Lac Objects ◽  
Close Interaction ◽  
Relativistic Jet ◽  
Bl Lac ◽  
Nearby Galaxies ◽  
Bl Lacs

A widely accepted model for BL Lac objects is that they are radio galaxies with a relativistic jet pointing almost directly towards us. But we need a clear trigger mechanism for these jets. One possibility is the close interaction between the BL Lac host and the closeby galaxies (e.g. Heckman et al. 1986). This interaction has been seen many times in the case of quasars (Hutchings et al. 1989) but not so much is known about the close surroundings of the BL Lac objects although there has been some pioneer work like Stickel et al. (1993). The problem has usually been that the images are not deep enough and that the seeing has not been so good. To clarify the situation we have started an observing program to get very deep images in the sub-arcsecond seeing conditions from the whole 1 Jy sample (Stickel et al. 1991) of BL Lac objects. The aims of this study are: 1. to search for very close companions to the BL Lacs, 2. to study the large scale galaxy clustering around the BL Lacs and 3. to study the BL Lac hosts themselves.

VERITAS OBSERVATIONS OF RELATIVISTIC OUTFLOWS IN LOW- AND INTERMEDIATE-FREQUENCY-PEAKED BL LAC OBJECTS

2014 ◽  
Vol 28 ◽  
pp. 1460178
Author(s):  
◽  
HEIKE PROKOPH
Keyword(s):  
Gamma Ray ◽  
Intermediate Frequency ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Bl Lacs ◽  
Gamma Ray Telescopes ◽  
Very High

The majority of blazars detected at very high energies (VHE; E > 100 GeV) are high-frequency-peaked BL Lac objects (HBLs). Low- and intermediate-frequency-peaked BL Lacs (LBLs/IBLs with synchrotron-peak frequencies in the infrared and optical regime) are generally more powerful, more luminous, and have a richer jet environment than HBLs. However, only a handful of these IBL and LBLs have been detected by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array has been monitoring five known VHE LBLs/IBLs since 2009: 3C 66A, W Comae, PKS 1424+240, S5 0716+714 and BL Lacertae, with typical exposures of 5-10 hours per year. The results of these long-term observations are presented, including a bright, subhour-scale VHE flare of BL Lacertae in June 2011, the first low-state detections of 3C 66A and W Comae, and the detection and characterization of the IBL B2 1215+30.

scholarly journals The estimation of γ-ray Doppler factor for Fermi/LAT-detected blazars

2020 ◽  
Vol 37 ◽  
Author(s):  
Zhiyuan Pei ◽  
Junhui Fan ◽  
Jianghe Yang ◽  
Denis Bastieri
Keyword(s):  
Lower Limit ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Bl Lac Objects ◽  
Relativistic Jet ◽  
Spectrum Radio ◽  
Bl Lac ◽  
Doppler Factor ◽  
Bl Lacs ◽  
Extreme Observation

Abstract Blazars are a subclass of active galactic nuclei with extreme observation properties, which is caused by the beaming effect, expressed by a Doppler factor ( $\delta$ ), in a relativistic jet. Doppler factor is an important parameter in the blazars paradigm to indicate all of the observation properties, and many methods were proposed to estimate its value. In this paper, we present a method following Mattox et al. to calculate the lower limit on $\gamma$ -ray Doppler factor ( $\delta_{\gamma}$ ) for 809 selected Fermi/LAT-detected $\gamma$ -ray blazars by adopting the available $\gamma$ -ray and X-ray data. Our sample included 342 flat-spectrum radio quasars (FSRQs) and 467 BL Lac objects (BL Lacs), out of which 507 sources are compiled with available radio core-dominance parameter (R) from our previous study. Our calculation shows that the average values of the lower limit on $\delta_{\gamma}$ for FSRQs and BL Lacs are $\left\langle\delta_{\gamma}|_{\textrm{FSRQ}}\right\rangle = 6.87 \pm 4.07$ and $\left\langle\delta_{\gamma}|_{\textrm{BL\ Lac}}\right\rangle=4.31 \pm 2.97$ , respectively. We compare and discuss our results with those from the literature. We found that the derived lower limit on $\delta_{\gamma}$ for some sources is higher than that from the radio estimation, which could be possibly explained by the jet bending within those blazars. Our results also suggest that the $\gamma$ -ray and radio regions perhaps share the same relativistic effects. The $\gamma$ -ray Doppler factor has been found to be correlated with both the $\gamma$ -ray luminosity and core-dominance parameter, implying that the jet is possibly continuous in the $\gamma$ -ray bands, and R is perhaps an indicator for a beaming effect.

scholarly journals Cm-Wavelength Flux Variability: Constraints on AGN Modeling

1994 ◽  
Vol 159 ◽  
pp. 497-497
Author(s):  
M.F. Aller ◽  
H.D. Aller ◽  
P.A. Hughes
Keyword(s):  
Flux Density ◽  
Linear Polarization ◽  
Total Flux ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Flux Variability ◽  
Bl Lac ◽  
Bl Lacs

To study whether the radio properties of BL Lacertae type objects and QSOs differ, we initiated a program in 1979 to monitor the total flux density and linear polarization at 14.5, 8.0 and 4.8 GHz of the strongest then known BL Lac objects which met the Hewitt-Burbidge criteria (Ledden, private communications) plus 3 subsequently identified high declination BL Lacs (Biermann et al. 1981). Results based on the behavior of the 45 brightest sample members are compared here with the properties of the QSOs in the flux-limited Pearson-Readhead sample (Pearson and Readhead 1988).

scholarly journals BL Lacertae objects as an evolutionary population

1986 ◽  
Vol 119 ◽  
pp. 491-492
Author(s):  
A. Cavaliere ◽  
E. Giallongo ◽  
F. Vagnetti
Keyword(s):  
Luminosity Function ◽  
Bl Lacertae Objects ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Bl Lacs

If the BL Lac Objects are active nuclei with a beamed component that is dominant when directed at us, their observed luminosity function must comprise a flat faint branch: N(L)dL ∝ L1+1/pdL with p=4.5 (Urry and Shafer 1984). If this is flatter than the LF NP(L) of the parent objects at equal observed L, then we expect the counts of BL Lacs to flatten out in turn at fluxes quite higher than the counts of the parents, even when both populations evolve strongly and uniformly with comparable timescales (Cavaliere, Giallongo and Vagnetti 1985).

scholarly journals The Compact Magnetic Field Structures of AGN from Space VLBI Polarization Observations

2001 ◽  
Vol 205 ◽  
pp. 134-135
Author(s):  
D.C. Gabuzda ◽  
J.L. Gómez
Keyword(s):  
Magnetic Field ◽  
Active Galactic Nuclei ◽  
Linear Polarization ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Emission Mechanism ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Optical Line

BL Lacertae objects are active galactic nuclei with weak, sometimes undetectable, optical line emission and strong variability in total intensity and linear polarization over a broad range of wavelengths from ultraviolet to radio. It is believed that synchrotron radiation is the dominant emission mechanism virtually throughout the spectrum. Their strong linear polarization makes BL Lac objects prime targets for space VLBI polarization observations.

The optical to near-infrared emission of BL Lac objects - Simultaneous observations

1993 ◽  
Vol 106 ◽  
pp. 11 ◽  
Author(s):  
R. Falomo ◽  
M. Bersanelli ◽  
P. Bouchet ◽  
E. G. Tanzi
Keyword(s):  
Near Infrared ◽  
Infrared Emission ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Near Infrared Emission

scholarly journals Discovery of Five New X-ray–Selected BL Lacertae Objects and Three New Quasars

1997 ◽  
Vol 159 ◽  
pp. 423-424
Author(s):  
G.Z. Xie ◽  
W. Brinkmann ◽  
G.W. Cha ◽  
S. Laurent-Muehleisen ◽  
Y.H. Zhang ◽  
...  
Keyword(s):  
Astronomical Observatory ◽  
Bl Lacertae Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lacertae ◽  
Bl Lac

Through combined ROSAT and VLA observations, we have identified 19 BL Lac/quasar candidates. In 1994 December, 1995 January and October, and 1996 January 1996, we obtained spectra of all 19 candidates using the 2.16-m telescope of Beijing Astronomical Observatory. The dispersion used is 195 Å mm−1, which yields a dispersion of about 4.65 Å pixel−1, and the wavelength coverage is 3500–7800 Å. Five of these objects are uniformly featureless, and we identify them as BL Lac objects. Three new quasars are also identified. Table 1 presents VLA positions and redshifts for the 5 new BL Lac objects and three new quasars. By checking them in the NASA/IPAC Extragalactic Database (NED) and Véron-Cetty & Véron’s (1993) Catalogue of Quasars and AGNs, and other recent reports about discovery of new BL Lac objects and quasars, we find that these sources are previously unreported.

scholarly journals Frequency Dependence of the Parsec-scale Polarization Structures of BL Lac Objects

2001 ◽  
Vol 205 ◽  
pp. 140-141
Author(s):  
A.B. Pushkarev ◽  
D.C. Gabuzda ◽  
T.V. Cawthorne
Keyword(s):  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Sky Survey ◽  
Radiation Sources ◽  
Wide Wavelength Range ◽  
Bl Lac ◽  
5 Ghz

BL Lacertae objects are active galactic nuclei with weak or undetectable line emission and strong variability in total intensity and linear polarization over a wide wavelength range from optical to radio. The radio emission and much of the optical emission is believed to be synchrotron radiation. Sources in the complete sample of BL Lac objects defined by Kühr and Schmidt (1990) have: 5 GHz fluxes of at least 1 Jy, radio spectral index α ≥ −0.5 (Sv ˜ v+α), rest frame equivalent width of the strongest emission lines less than 5 Å, and optical counterparts on the Sky Survey plates with brightness greater than 20m.

scholarly journals Spectral Variability of BL Lac Objects

2002 ◽  
Vol 19 (1) ◽  
pp. 111-113 ◽  
Author(s):  
R. D'Amicis ◽  
R. Nesci ◽  
E. Massaro ◽  
M. Maesano ◽  
F. Montagni ◽  
...  
Keyword(s):  
The Other ◽  
Time Interval ◽  
Spectral Slope ◽  
Spectral Variability ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Bl Lac

AbstractWe present the relation between optical luminosity and spectral slope for eight BL Lac objects (3C66A, PKS 0422+00, S5 0716+71, OJ 287, ON 231, OQ 530, S5 1803+78 and BL Lacertae), derived from B, V, R, and I observations spanning a time interval of about 5 years. Four objects show a marked correlation between spectral slope and luminosity, being bluer when brighter, while for the other four the correlation is weaker or absent. Possible explanations are briefly discussed in the framework of current models of the BL Lac phenomenon.

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