An emerging population of BL Lacs with extreme properties: towards a class of EBL and cosmic magnetic field probes?

High energy observations of extreme BL Lac objects, such as 1ES 0229+200 or 1ES 0347-121, recently focused interest both for blazar and jet physics and for the implication on the extragalactic background light and intergalactic magnetic field estimate. However, the number of these extreme highly peaked BL Lac objects (EHBL) is still rather small. Aiming at increase their number, we selected a group of EHBL candidates starting from the BL Lac sample of Plotkin et al. (2011), considering those undetected (or only barely detected) by the Large Area Telescope onboard Fermi and characterized by a high X-ray vs. radio flux ratio. We assembled the multi-wavelength spectral energy distribution of the resulting 9 sources, profiting of publicly available archival observations performed by the Swift, Galex and Fermi satellites, confirming their nature. Through a simple one-zone synchrotron self-Compton model we estimate the expected VHE flux, finding that in the majority of cases it is within the reach of present generation of Cherenkov arrays or of the forthcoming Cherenkov Telescope Array (CTA).

[1]  C. Boisson,et al.  A hadronic origin for ultra-high-frequency-peaked BL Lac objects , 2014, 1411.5968.

[2]  J. Chiang,et al.  THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV , 2014, The Astrophysical Journal.

[3]  J. Conrad,et al.  Sensitivity of the Cherenkov Telescope Array to the detection of axion-like particles at high gamma-ray opacities , 2014, 1410.1556.

[4]  K. Murase,et al.  Synchrotron pair halo and echo emission from blazars in the cosmic web: application to extreme TeV blazars , 2014, 1406.6075.

[5]  Yasuyuki T. Tanaka,et al.  EXTREME BLAZARS STUDIED WITH FERMI-LAT AND SUZAKU: 1ES 0347−121 AND BLAZAR CANDIDATE HESS J1943+213 , 2014, 1404.3727.

[6]  J. Ellis,et al.  The CTA sensitivity to Lorentz-violating effects on the gamma-ray horizon , 2014, 1401.8178.

[7]  G. Richards,et al.  A THREE-YEAR MULTI-WAVELENGTH STUDY OF THE VERY-HIGH-ENERGY γ-RAY BLAZAR 1ES 0229+200 , 2013, 1312.6592.

[8]  F. Tavecchio.  On the hadronic cascade scenario for extreme BL Lacs , 2013, 1312.4281.

[9]  P. Schady,et al.  THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS , 2013, 1310.0006.

[10]  K. Satalecka,et al.  Physics performance of the upgraded MAGIC telescopes obtained with Crab Nebula data , 2013, 1308.0141.

[11]  M. Cerruti.  VERITAS results from a three-year observing campaign on the BL Lac object 1ES 0229+200 , 2013, 1307.8091.

[12]  D. Fantinel,et al.  Towards the ASTRI mini-array , 2013 .

[13]  C. Dermer,et al.  DISENTANGLING HADRONIC AND LEPTONIC CASCADE SCENARIOS FROM THE VERY-HIGH-ENERGY GAMMA-RAY EMISSION OF DISTANT HARD-SPECTRUM BLAZARS , 2013, 1305.2138.

[14]  M. V. Fernandes,et al.  Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9–185406 , 2013, 1304.4023.

[15]  A. Prakash,et al.  LEPTONIC AND HADRONIC MODELING OF FERMI-DETECTED BLAZARS , 2013, 1304.0605.

[16]  D. Fantinel,et al.  The ASTRI Mini-Array Science Case , 2013, 1307.5671.

[17]  T. Kang,et al.  EVIDENCE FOR SECONDARY EMISSION AS THE ORIGIN OF HARD SPECTRA IN TeV BLAZARS , 2013, 1609.09148.

[18]  William W. Zhang,et al.  THE NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY (NuSTAR) HIGH-ENERGY X-RAY MISSION , 2013, Astronomical Telescopes and Instrumentation.

[19]  William H. Lee,et al.  Introducing the CTA concept , 2013 .

[20]  K. Ioka,et al.  Upper limit on the cosmological gamma-ray background , 2012, 1206.2923.

[21]  J. Beacom,et al.  Gamma-ray and neutrino backgrounds as probes of the high-energy universe: hints of cascades, general constraints, and implications for TeV searches , 2012, 1205.5755.

[22]  D. Semikoz,et al.  FERMI/LAT OBSERVATIONS OF 1ES 0229+200: IMPLICATIONS FOR EXTRAGALACTIC MAGNETIC FIELDS AND BACKGROUND LIGHT , 2011, 1112.2534.

[23]  Hajime Takami,et al.  BLAZARS AS ULTRA-HIGH-ENERGY COSMIC-RAY SOURCES: IMPLICATIONS FOR TeV GAMMA-RAY OBSERVATIONS , 2011, 1107.5576.

[24]  V. Golev,et al.  Design concepts for the Cherenkov Telescope Array CTA: an advanced facility for ground-based high-energy gamma-ray astronomy , 2011 .

[25]  M. Hauser,et al.  1ES 0229+200: an extreme blazar with a very high minimum Lorentz factor , 2011, 1109.3628.

[26]  F. Aharonian,et al.  FORMATION OF VERY HARD GAMMA-RAY SPECTRA OF BLAZARS IN LEPTONIC MODELS , 2011, 1106.4201.

[27]  F. Aharonian,et al.  MODELING THE HARD TeV SPECTRA OF BLAZARS 1ES 0229+200 AND 3C 66A WITH AN INTERNAL ABSORPTION SCENARIO , 2011, 1106.3129.

[28]  L. A. Antonelli,et al.  Mrk 421 active state in 2008: the MAGIC view, simultaneous multi-wavelength observations and SSC model constrained , 2011, 1106.1589.

[29]  A. M. Taylor,et al.  EGMF Constraints from Simultaneous GeV-TeV Observations of Blazars , 2011, 1101.0932.

[30]  Charles D. Dermer,et al.  TIME DELAY OF CASCADE RADIATION FOR TeV BLAZARS AND THE MEASUREMENT OF THE INTERGALACTIC MAGNETIC FIELD , 2010, 1011.6660.

[31]  J. Beacom,et al.  ROLE OF LINE-OF-SIGHT COSMIC-RAY INTERACTIONS IN FORMING THE SPECTRA OF DISTANT BLAZARS IN TeV GAMMA RAYS AND HIGH-ENERGY NEUTRINOS , 2010, 1011.6340.

[32]  U. Washington,et al.  Dynamical black hole masses of BL Lac objects from the Sloan Digital Sky Survey , 2010, 1012.1601.

[33]  G. Ghisellini,et al.  Extreme TeV blazars and the intergalactic magnetic field , 2010, 1009.1048.

[34]  L. Sironi,et al.  PARTICLE ACCELERATION IN RELATIVISTIC MAGNETIZED COLLISIONLESS ELECTRON–ION SHOCKS , 2010, 1009.0024.

[35]  M. C. Cooper,et al.  Extragalactic background light inferred from AEGIS galaxy-SED-type fractions , 2010, 1103.4534.

[36]  Ievgen Vovk,et al.  Evidence for Strong Extragalactic Magnetic Fields from Fermi Observations of TeV Blazars , 2010, Science.

[37]  D. York,et al.  OPTICALLY SELECTED BL LACERTAE CANDIDATES FROM THE SLOAN DIGITAL SKY SURVEY DATA RELEASE SEVEN , 2009, 0911.0423.

[38]  R. D. Baldi,et al.  Radio and spectroscopic properties of miniature radio galaxies: revealing the bulk of the radio-loud AGN population , 2009, 0910.4261.

[39]  L. Costamante,et al.  The hard TeV spectrum of 1ES 0229+200: new clues from Swift , 2009, 0905.0899.

[40]  S. Ostapchenko,et al.  BLAZAR HALOS AS PROBE FOR EXTRAGALACTIC MAGNETIC FIELDS AND MAXIMAL ACCELERATION ENERGY , 2009, 0903.2842.

[41]  Charles D. Dermer,et al.  The Hard VHE γ-Ray Emission in High-Redshift TeV Blazars: Comptonization of Cosmic Microwave Background Radiation in an Extended Jet? , 2008, 0804.3515.

[42]  L. Costamante,et al.  Formation of hard very high energy gamma-ray spectra of blazars due to internal photon-photon absorption , 2008, 0801.3198.

[43]  HESS Collaboration F. Aharonian,et al.  New constraints on the mid-IR EBL from the HESS discovery of VHE gamma-rays from 1ES 0229+200 , 2007, 0709.4584.

[44]  M. J. Page,et al.  Photometric calibration of the Swift ultraviolet/optical telescope , 2007, 0708.2259.

[45]  M. Tornikoski,et al.  Spectral energy distributions of a large sample of BL Lacertae objects , 2005, astro-ph/0509045.

[46]  W. B. Burton,et al.  The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI - Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections , 2005, astro-ph/0504140.

[47]  G. Ghisellini,et al.  Correlation between the TeV and X-ray emission in high-energy peaked BL Lac objects , 2004, astro-ph/0412405.

[48]  A. Szalay,et al.  The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission , 2004, astro-ph/0411302.

[49]  Wolfgang A. Rolke,et al.  Limits and confidence intervals in the presence of nuisance parameters , 2004, physics/0403059.

[50]  P. Giommi,et al.  The Sedentary Survey of Extreme High Energy Peaked BL Lacs. II. The Catalog and Spectral Properties , 2004, astro-ph/0411093.

[51]  C. Carilli,et al.  Science with the Square Kilometer Array , 2004, astro-ph/0409274.

[52]  G. Giovannini,et al.  A Sample of Low-Redshift BL Lacertae Objects. I. The Radio Data , 2004, astro-ph/0406255.

[53]  Peter W. A. Roming,et al.  The Swift Ultra-Violet/Optical Telescope , 2002, SPIE Optics + Photonics.

[54]  D. Watson,et al.  The Swift X-Ray Telescope , 1999, SPIE Optics + Photonics.

[55]  C. Dermer,et al.  Neutral Beams from Blazar Jets , 2002, astro-ph/0209231.

[56]  T. Stanev,et al.  BL Lac objects in the synchrotron proton blazar model , 2002, astro-ph/0206164.

[57]  L. Maraschi,et al.  The Jet-Disk Connection and Blazar Unification , 2002, astro-ph/0205252.

[58]  T. Weekes,et al.  Detection of the BL Lacertae Object H1426+428 at TeV Gamma-Ray Energies , 2002, astro-ph/0202185.

[59]  L. Costamante,et al.  TeV candidate BL Lac objects , 2001, astro-ph/0112201.

[60]  P. Giommi,et al.  Extreme synchrotron BL Lac objects , 2001, astro-ph/0103343.

[61]  F. Aharonian.  TeV gamma rays from BL Lac Objects due to synchrotron radiation of extremely high energy protons , 2000, astro-ph/0003159.

[62]  Milano,et al.  Constraints on the Physical Parameters of TeV Blazars , 1998, astro-ph/9809051.

[63]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[64]  Italy.,et al.  A unifying view of the spectral energy distributions of blazars , 1998, astro-ph/9804103.

[65]  D. L. Bertsch,et al.  The Likelihood Analysis of EGRET Data , 1996 .

[66]  Y. Pei,et al.  Interstellar dust from the Milky Way to the Magellanic Clouds , 1992 .

[67]  N. A. Dobrotin,et al.  INTERNATIONAL COSMIC RAY CONFERENCE , 1960 .