The BL-Lac gamma-ray blazar PKS 1424+240 associated with a group of galaxies at z=0.6010

Abstract

PKS 1424+240 is a BL-Lac blazar with unknown redshift that was detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. At VHE, it was first detected by VERITAS and later confirmed by MAGIC. Its spectral energy distribution is highly attenuated at VHE gamma rays, which is coherent with distant sources. Several estimations enabled the redshift to be constrained to the range 0.6 < z < 1.3. These results place PKS 1424+240 in the very interesting condition of being probably the most distant blazar that has been detected at VHE. The ambiguity in the redshift is still large enough to prevent precise studies of the EBL and the intrinsic blazar spectrum. Given the difficulty of measuring spectroscopic redshifts for BL-Lac objects directly, we aim to establish a reliable redshift value for this blazar by finding its host group of galaxies. Elliptical galaxies are associated with groups, and BL-Lac objects are typically hosted by them, so we decided to search for the host group of the blazar. For this, we performed optical spectroscopic observations of thirty objects in the field of view of PKS 1424+240 using the Gemini MOS. After analysing the data for groups, we evaluated the probability of finding groups of galaxies by chance around the position of PKS 1424+240, using a deep catalogue of groups. We also used photometric data from the SDSS catalogue to analyse the red sequence of the proposed blazar host group. We found a new group of galaxies with eight members at z = 0.6010 +- 0.003, a virial radius of R_vir = 1.53 Mpc, and a velocity dispersion of sigma_v = 813 +- 187 km/s. The photometric study indicates that more members are probably populating this previously uncatalogued group of galaxies. The probability of PKS 1424+240 being a member of this group was found to be 98%. The new group of galaxies found at z = 0.6010 +- 0.003 is very likely hosting PKS 1424+240.

arXiv commentAccepted for publication in A&A. Second version: references added and typo corrected

References in corpus (28)

• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• The Cosmic Evolution Survey (COSMOS) -- Overview
• A low level of extragalactic background light as revealed by gamma-rays from blazars
• Estimating Fixed Frame Galaxy Magnitudes in the SDSS
• Science Objectives and Early Results of the DEEP2 Redshift Survey
• Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is the Universe?
• The Extragalactic Background Light and the Gamma-ray Opacity of the Universe
• HST/COS Observations of the Ly alpha Forest toward the BL Lac Object 1ES1553+113
• Imaging redshifts of BL Lac objects
• Fermi observations of TeV-selected AGN
• Galaxies in SDSS and DEEP2: a quiet life on the blue sequence?
• The zCOSMOS 20k Group Catalog
• BL Lacertae objects beyond redshift 1.3 - UV-to-NIR photometry and photometric redshift for Fermi/LAT blazars
• The classification of BL Lacertae objects: the Ca H&K break
• The Firm Redshift Lower Limit of the Most Distant TeV-Detected Blazar PKS 1424+240
• Discovery of very high energy gamma rays from PKS 1424+240 and multiwavelength constraints on its redshift
• Strong New Constraints on the Extragalactic Background Light in the Near- to Mid-IR
• A Fast Flare and Direct Redshift Constraint in Far-UV Spectra of the Blazar S50716+714
• MAGIC long-term study of the distant TeV blazar PKS 1424+240 in a multiwavelength context
• Constraints on the Extragalactic Background Light from Very High Energy Gamma-Ray Observations of Blazars
• Understanding the TeV emission from a distant blazar PKS 1424+240 in a lepto-hadronic jet model
• Groups in the Millennium Simulation and in SDSS DR7
• On the Redshift of the Very High Energy Blazar 3C 66A
• An Empirical Determination of the Intergalactic Background Light Using NIR Deep Galaxy Survey Data out to 5 microns and the Gamma-ray Opacity of the Universe
• The BL-Lac gamma-ray blazar PKS 0447-439 as a probable member of a group of galaxies at z=0.343
• Redshifts of distant blazar limited by Fermi and VHE $\gamma$-ray observations
• Studies of active galactic nuclei with CTA
• A self-consistent interpretation of the GeV-TeV emission from a distant blazar PKS 1424+240

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• The Physical Origins of the Identified and Still Missing Components of the Warm-Hot Intergalactic Medium: Insights from Deep Surveys in the Field of Blazar 1ES1553+113
• Testing two-component models on very-high-energy gamma-ray emitting BL Lac objects
• PKS 1424+240: yet another masquerading BL Lac object as a possible IceCube neutrino source
• On the origin of the soft photons of the high synchrotron peaked blazar : PKS 1424+240
• Redshift determination of the BL Lac object 3C66A by the detection of its host galaxy cluster at $z=0.340$
• Luminous and high-frequency peaked blazars: the origin of the $\gamma$-ray emission from PKS 1424+240
• High-energy neutrinos from X-rays flares of blazars frequently observed by the Swift X-Ray Telescope
• Testing CIBER cosmic infrared background measurements and axionlike particles with observations of TeV blazars
• The COS-legacy survey of C IV absorbers: properties and origins of the intervening systems
• Optical Spectroscopy of Blazars for the Cherenkov Telescope Array -- II
• 3C 17: The BCG of a galaxy cluster at z=0.22
• The Intrinsic Gamma-Ray Spectrum of TXS 0506+056: Intergalactic Propagation Effects
• The fraction of BL Lac objects in groups of galaxies
• Constraining the redshifts of TeV BL Lac objects
• New GTC Spectroscopic Data and a Statistical Study to Better Constrain the Redshift of the BL Lac RGB J2243+203
• Solar-Metallicity Gas in the Extended Halo of a Galaxy at $z\sim 0.12$
• Redshift constrain of BL Lac PKS 1424+240
• Distance estimation of gamma-ray emitting BL Lac objects from imaging observations