Abstract
We use the distributions of spectral indices (αv ) of a large homogenous sample of Fermi-detected blazars to re-investigate the relationship between flat spectrum radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute the broadband synchrotron and Compton spectral indices from radio-to-X-ray and X-ray to y-ray bands, respectively. Analyses of our data show continuity in the distributions of the spectral indices from FSRQs to HSP through LSP and ISP subclasses of BL Lacs. We find from y-ray luminosity distribution that the jetted radio galaxies form the low-luminosity tail of the distribution, which is suggestive that the sequence can be extended to the young jetted galaxy populations. We observe a significant difference in the shape of Compton and synchrotron spectra: significant anti-correlation (r ∼−0.80) exists between the broadband Compton and synchrotron spectral indices. Furthermore, the broadband spectral indices vary significantly with redshift (z) at low redshift (z < 0.3) and remain fairly constant at high (z ≥ 0.3) redshift. The trend of the variations suggests a form of evolutionary connection between subclasses of blazars. Thus, while selection effect may be significant at low redshift, evolutionary sequence can also be important. Our results are not only consistent with a unified scheme for blazars and their young jetted galaxy counterparts but also suggest that the broadband spectral sequence of blazars is not a secondary effect of redshift dependence.
References
Abdo A A, Ackermann M, Ajello M, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Baughman BM, et al. 2009. Bright active galactic nuclei source list from the first three months of the Fermi large area telescope all-sky survey. ApJ.700: 597-622Search in Google Scholar
Abdo AA, Ackermann M, Agudo I, Ajello M, Aller HD, Aller MF, Angelakis E, Arkharov AA, Axelsson M, Bach U, et al. 2010c. The spectral energy distribution of Fermi bright blazars. ApJ. 716:30–70Search in Google Scholar
Abdo AA, Ackermann M, Ajello M, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bechtol K, et al. 2010a. Spectral properties of bright Fermi-detected blazars in the gamma-ray band. ApJ. 710: 1271-1285Search in Google Scholar
Abdo AA, Ackermann M, Ajello M, Allafort A, Antolini E, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, et al. 2010b. The first catalogue of active galactic nuclei detected by the Fermi large area telescope. ApJ. 715: 429–457Search in Google Scholar
Ackermann M, Ajello M, Atwood WB, Baldini L, Ballet J, Barbiellini G, Bastieri D, Becerra J, Bellazzini R, Bissaldi E, et al. 2015. The third catalogue of active galactic nuclei detected by the Fermi large area telescope. ApJ. 810: 14-47Search in Google Scholar
Ackermann M, Ajello M, Allafort A, Antolini E, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, et al. 2011. The second catalogue of active galactic nuclei detected by the Fermi large area telescope. ApJ. 743:171-208Search in Google Scholar
Acero F, Ackermann M, Ajello M, Albert A, Atwood WB, Axelsson M, Baldini L, Ballet J, Barbiellini G, Bastieri D, et al. 2015. Fermi large area telescope third source catalogue. ApJS. 218: 23-64Search in Google Scholar
Ajello, M, Romani, RW, Gasparrini D, Shaw MS, Bolmer J, Cotter G, Finke J, Greiner J, Healey SE, King O, et al. 2014. The cosmic evolution of Fermi BL Lacertae objects. ApJ. 780: 73-10710.1088/0004-637X/780/1/73Search in Google Scholar
Alhassan JA, Ubachukwu AA, Odo FC, Onuchukwu CC. 2019. Relativistic beaming effects and structural asymmetries in highly asymmetric double radio sources. Rev MexAA. 55: 151-15910.22201/ia.01851101p.2019.55.02.03Search in Google Scholar
Alhassan JA, Ubachukwu AA, Odo FC. 2013. On the absence of core luminosity-core dominance parameter (Pc-R) correlation in radio galaxies and BL lacs. Jour. Astrophy. & Astro. 34: 61-6710.1007/s12036-013-9161-0Search in Google Scholar
Andruchow I, Romero GE, Cellone SA. 2005. Polarization microvari-ability of BL lacerate objects. Astron. & Astrophys. 442: 97-10710.1051/0004-6361:20053325Search in Google Scholar
Athreya RM, Kapahi VK. 1998. The redshift dependence of spectral index in powerful radio galaxies. Jour. of Astrophys. & Astron. 19: 63-7710.1007/BF02714911Search in Google Scholar
Blandford RD, Rees MJ. 1978. In Pittsburgh conference on BL Lac Objects, ed. A. M. Wolfe (Pittsburgh: University of Pittsburgh), 328-341Search in Google Scholar
Beckmann V, Engles D, Bade N, Wucknitz O. 2003. The HRX-BL Lac sample - evolution of BL Lac objects. A&A. 401: 927–93810.1051/0004-6361:20030184Search in Google Scholar
Böttcher M. 2007. Modeling the emission processes in blazars. in the multi-messenger approach to high-energy gamma-ray sources. Astrophys. & Space Sci. 309: 95-10410.1007/978-1-4020-6118-9_16Search in Google Scholar
Cellone SA, Romero GE, Araudo AT. 2007. Extremely violent optical micro-variability in blazars: fact or fiction? MNRAS. 374: 357-36410.1111/j.1365-2966.2006.11140.xSearch in Google Scholar
Chen YY, Zhang X, Xiong DR, Wang SJ, Yu XL. 2016. The beaming effect and γ-ray emission for Fermi blazars. Res. Astron. & Astrophys. 16: 13-2310.1088/1674-4527/16/1/013Search in Google Scholar
Comastri A, Fossati G, Ghisellini G, Molendi S. 1997. On the soft x-ray spectra of γ-loud blazars. ApJ. 480: 534-54610.1086/303986Search in Google Scholar
Dermer CD, Giebels B. 2016. Active galactic nuclei at gamma-ray energies. Com. Rend. Physique. 17: 594-61010.1016/j.crhy.2016.04.004Search in Google Scholar
Fan JH, Yang JH, Liu Y, Luo GY, Lin C, Yuan YH, Xiao HB, Zhou AY, Hua TX, Pei ZY. 2016. The Spectral energy distributions of Fermi blazars. ApJS. 226: 20-3810.3847/0067-0049/226/2/20Search in Google Scholar
Finke JD. 2013. Compton dominance and the blazar sequence. ApJ. 763 (2) 134-145Search in Google Scholar
Foffano L, Prandini E, Franceschini A, Paiano S. 2019. A new hard X-ray-selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties. MNRAS, 486(2):1741–1762,10.1093/mnras/stz812Search in Google Scholar
Fossati G, Maraschi L, Celotti A, Comastri, A, Ghisellini G. 1998. A unifying view of the spectral energy distributions of blazars. MNRAS. 299: 433–44810.1046/j.1365-8711.1998.01828.xSearch in Google Scholar
Gaur H, Gupta AC, Lachowerez P, Wiita P. 2010. Detection of intraday variability of four high-energy peaked blazars with XMM-NEWTON. ApJ. 718: 279-29110.1088/0004-637X/718/1/279Search in Google Scholar
Ghisellini G, Celotti A, Fossati G, Maraschi L, Comastri A. 1998. A theoretical unifying Scheme for gamma-ray bright blazars. MNRAS. 301: 451–46810.1046/j.1365-8711.1998.02032.xSearch in Google Scholar
Ghisellini G, Tavecchio F. 2008. The blazar sequence: a new perspective. MNRAS. 387: 1669-168010.1111/j.1365-2966.2008.13360.xSearch in Google Scholar
Giommi P, Padovani P, Polenta G. 2013. A simplified view of blazars: the γ-ray case. MNRAS. 431: 1914–192210.1093/mnras/stt305Search in Google Scholar
Giommi P, Padovani P, Polenta G, Turriziani S, D’Elia V, Piranomonte S, et al. 2012. A simplified view of blazars: clearing the fog around long-standing selection effects. MNRAS. 420: 2899– 291110.1111/j.1365-2966.2011.20044.xSearch in Google Scholar
Giommi P, Ansari SG, Micol A. 1995. Radio to x-ray energy distribution of BL Lacertae objects. A&A. 109: 267-29110.1007/978-94-010-9537-2_204Search in Google Scholar
IceCube Collaboration; Aartsen MG, Ackermann M, Adams J, Aguilar JA, Ahlers M, Ahrens M, Al Samarai I, Altmann D, Andeen K, et al. 2018. Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A. Science. 361: eaat1378.Search in Google Scholar
Keivan A, Murase K, Petropoulou M, Fox DB, Cenko SB, Chaty S, Coleiro A, Delaunay JJ, Dimitrakoudis S, Evans PA, et al. 2018. A Multimessenger picture of the flaring blazar TXS 0506 +056, implications for high energy neutrino emission and cosmic ray accelerations. ApJ. 864: 84-10010.3847/1538-4357/aad59aSearch in Google Scholar
Kharb P, Lister ML, Cooper NJ. 2010. Extended radio emission in MOJAVE blazars: challenges to unification. ApJ. 710: 764-78210.1088/0004-637X/710/1/764Search in Google Scholar
Kollgaard RI. 1994. Relativistic jets and nature of BL Lacertae objects. Vistas in Astronomy, 38: 29-7510.1016/0083-6656(94)90003-5Search in Google Scholar
Ledden JE, Odell SL. 1985. The radio-optical-x-ray spectral flux distributions of blazars. ApJ. 298: 630-64310.1086/163647Search in Google Scholar
Li HZ, Xie GZ, Yi TF, Chen LE, Dai H. 2010. The spectral energy distributions of the Fermi blazars and connections among low-energy peaked, high energy peaked BL Lacertae and flat spectrum radio quasars. ApJ. 709, 1407-141110.1088/0004-637X/709/2/1407Search in Google Scholar
Li HZ, Cheng LE, Jiang TF, Jiang YG, Yi TF. 2015. The broadband spectral energy distributions of SDSS blazars. Res. Astron. & Astrophys. 15(7), 929-93810.1088/1674-4527/15/7/001Search in Google Scholar
Li YT, Fu SY, Feng HJ, He SL, Lin C, Fan JH, et al. 2017. Ratio of the core to the extended emissions in the commoving frame for blazars. Jour. of Astrophy. & Astro. 38: 22-3410.1007/s12036-017-9442-0Search in Google Scholar
Lind KR, Blandford RD.1985. Semi-dynamical models of radio jets -relativistic beaming and source counts. ApJ. 295: 358 - 36710.1086/163380Search in Google Scholar
Lister ML, Aller M, Aller H, Hovatta T, Kellermann KI, Kovalev YY, Meyer ET, Pushkarev AB, Ros E, Ackermann M, et al. 2011. Gamma-ray and parsec-scale jet properties of blazars from the MOJAVE program. ApJ. 742: 27-52Search in Google Scholar
Meyer ET, Fossati G, Georganopoulos M, Lister ML. 2011. From the blazar sequence to the blazar envelope: revisiting the relativistic jet dichotomy in radio-loud active galactic nuclei. ApJ. 740: 98 -11310.1088/0004-637X/740/2/98Search in Google Scholar
Mukherjee R, Bertsch DL, Bloom SD, Dingus BL, Esposito JA, Fichtel CE, Hartman RC, Hunter SD, Kanbach G, Kniffen DA, et al. 1997. EGRET observations of high-energy gamma-ray emission from blazars: an update. ApJ. 490:116-13510.1086/304851Search in Google Scholar
Nalewajko K, Gupta M. 2017. The sequence of compton dominance in blazars based on data from WISE and Fermi-LAT. A&A, 606: A44 - A5110.1051/0004-6361/201731329Search in Google Scholar
Nieppola E, Tornikoski M, Valtaoja E. 2006. Spectral energy distributions of a large sample of BL Lacertae objects. A&A. 445:441-45010.1051/0004-6361:20053316Search in Google Scholar
Odo FC, Aroh BE. 2020. On the unified view of gamma-ray energy distribution of BL Lac objects and flat spectrum radio quasars. Jour. Astrophy. & Astro. 41: 9 -1910.1007/s12036-020-9626-xSearch in Google Scholar
Odo FC, Chukwude AE, Ubachukwu AA. 2017. Relativistic beaming effects in BL Lactertae objects: evidence for RBL/XBL dichotomy. Astrophys. & Space Sci. 362: 23-3510.1007/s10509-016-2999-2Search in Google Scholar
Odo FC, Chukwude AE, Ubachukwu AA. 2014. Luminosity-redshift (L- z) relation and the blazar sequence for low power blazars. Astrophys. & Space Sci. 349: 939 -94510.1007/s10509-013-1694-9Search in Google Scholar
Padovani P, Oikonomou F, Petropoulou M, Giommi P, Resconi E. 2019. TXS 0506 + 056, the first cosmic neutrino source, is not a BL Lac? MNRAS. 484(1): L104-L10810.1093/mnrasl/slz011Search in Google Scholar
Padovani P. 2007. The blazar sequence: validity and predictions. Astrophys. & Space Scie, 309: 63-7110.1007/978-1-4020-6118-9_12Search in Google Scholar
Padovani P. 1992. Is there a relationship between BL Lacertae objects and flat spectrum radio quasars? MNRAS. 257: 404-41410.1093/mnras/257.3.404Search in Google Scholar
Palladino A, Rodrigues X, Gao S, Winter W. 2019. Interpretation of the diffuse astrophysical neutrino flux in terms of the blazar sequence. ApJ. 871: 41-5710.3847/1538-4357/aaf507Search in Google Scholar
Pei ZY, Fan JH, Bastieri D, Sawangwit U, Yang JH. 2019. The relationship between the radio core-dominance parameter and spectral index in different classes of extragalactic radio sources (II). Res. Astron. Astrophys. 19: 70-8610.1088/1674-4527/19/5/70Search in Google Scholar
Raiteri CM, Capetti A. 2016. Testing the blazar sequence with the least luminous BL Lacerate objects. A&A. 587: A8-A2310.1051/0004-6361/201527679Search in Google Scholar
Rani B, 2019. The TeV challenge. Galaxies. 7: 23-4210.3390/galaxies7010023Search in Google Scholar
Sambruna RM, Maraschi L, Urry CM. 1996. On the spectral energy distributions of blazars. ApJ. 463: 444-46510.1086/177260Search in Google Scholar
Savolainen T, Homan DC, Hovatta T, Kadler M, Kovalev YY, Lister ML, Ros E, et al. 2010. Relativistic beaming and gamma-ray brightness of blazars. A&A. 512: A24-A3010.1051/0004-6361/200913740Search in Google Scholar
Scarpa R, Falomo R. 1997. Are high polarization quasars and BL Lacertae objects really different? a study of the optical spectral properties. A &A. 325: 109-123Search in Google Scholar
Teng SH, Mushotxky RF, Sambruna RM, Davies DS, Reynolds CS. 2011. Ferm/LAT observations of SWIFT/BAT Seyfert galaxies: on the contributions of radio-quiet active galactic nuclei to the extragalactic γ-ray background. ApJ. 742, 66 -7410.1088/0004-637X/742/2/66Search in Google Scholar
Ubachukwu AA, Okoye SE, Onuora LI. 1993. On the luminosity evolution of extragalactic radio sources with epoch. Proceedings of Nig. Acade. Sci. 5: 63 – 73Search in Google Scholar
Urry CM. 2011. Gamma-ray and multi-wavelength emission from blazars. Jour. of Astrophy. & Astro. 32: 139 -14510.1007/s12036-011-9072-xSearch in Google Scholar
Urry CM, Padovani P. 1995. Unified schemes for radio-loud active galactic nuclei. Publ. Astron. Soc. Pacific 107: 715 - 80310.1086/133630Search in Google Scholar
Xie GZ, Dai BZ, Mei DC, Fan JH. 2001. The Doppler effect and spectral energy distribution of blazars. Chin. J. Astro. & Astrophys. 1: 213-22010.1088/1009-9271/1/3/213Search in Google Scholar
Yang JH, Fan JH, Liu Y, Zhang YL, Tuo MX, Nie JJ, et al. 2018. Effective spectral index properties for Fermi blazars, Sci. China-Phys. Mech. Astron. 61, 059511 https://doi.org/10.1007/s11433-017-9136-710.1007/s11433-017-9136-7Search in Google Scholar
Yefimov Y. 2011. Blazar observations in infrared optical regions: magnetic field strength evaluation. Jour. of Astrophys. & Astron. 32: 73-7710.1007/s12036-011-9062-zSearch in Google Scholar
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