An optical overview of blazars with LAMOST I: Hunting changing-look blazars and new redshift estimates

Abstract

The extragalactic $\gamma$-rays sky observed by Fermi-Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi-LAT Point Source Catalog (4FGL), are sources showing a multifrequency behavior similar to that of blazars but lacking an optical spectroscopic confirmation of their nature known as Blazar Candidate of Uncertain type (BCUs). We aim at confirming the blazar nature of BCUs and test if new optical spectroscopic observations can reveal spectral features, allowing us to get a redshift estimate for known BL Lac objects. We also aim to search for and discover changing-look blazars (i.e., blazars that show a different classification at different epochs). We carried out an extensive search for optical spectra available in the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We selected sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified or unassociated $\gamma$-ray sources, and the multifrequency catalog of blazars: the Roma-BZCAT. We selected a total of 392 spectra. We also compare some of the LAMOST spectra with those available in the literature. We classified 20 BCUs confirming their blazar-like nature. Then we obtained 15 new redshift estimates for known blazars. We discovered 26 transitional (i.e., changing-look) blazars that changed their classification. Finally, we were able to confirm the blazar-like nature of six BL Lac candidates. All remaining sources analyzed agree with previous classifications. BL Lac objects are certainly the most elusive type of blazars in the $\gamma$-ray extragalactic sky.

arXiv comment16 pages, 2 figures, 4 tables

References in corpus (132)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• Fermi Large Area Telescope Fourth Source Catalog
• Fermi Large Area Telescope Second Source Catalog
• Fermi Large Area Telescope First Source Catalog
• A Unifying View of the Spectral Energy Distributions of Blazars
• The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures
• The Spectral Energy Distribution of Fermi bright blazars
• An Exceptional VHE Gamma-Ray Flare of PKS 2155-304
• The 6dF Galaxy Survey: Samples, Observational Techniques and the First Data Release
• Variable VHE gamma-ray emission from Markarian 501
• The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Fast TeV variability in blazars: jets in a jet
• Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope
• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• MOJAVE. X. Parsec-Scale Jet Orientation Variations and Superluminal Motion in AGN
• The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Roma-BZCAT: A multifrequency catalogue of Blazars
• Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects: Superluminal Motion of Gamma-Ray Bright Blazars
• The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA Derived Quantities, Data Visualization Tools and Stellar Library
• The transition between BL Lac objects and Flat Spectrum Radio Quasars
• The 5th edition of the Roma-BZCAT. A short presentation
• 2FHL: The Second Catalog of Hard Fermi-LAT Sources
• A simplified view of blazars: clearing the fog around long-standing selection effects
• The Cosmic Evolution of Fermi BL Lacertae Objects
• The Imprint of The Extragalactic Background Light in the Gamma-Ray Spectra of Blazars
• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• Spectroscopy of The Largest Ever Gamma-ray Selected BL Lac Sample
• Spectroscopy of Broad Line Blazars from 1LAC
• Rapid Variability of Blazar 3C 279 during Flaring States in 2013-2014 with Joint Fermi-LAT, NuSTAR, Swift, and Ground-Based Multi-wavelength Observations
• A Tight Connection between Gamma-Ray Outbursts and Parsec-Scale Jet Activity in the Quasar 3C 454.3
• The Spectral Energy Distributions of Fermi Blazars
• Identification of the infrared non-thermal emission in Blazars
• Radiation Mechanisms and Physical Properties of GeV-TeV BL Lac Objects
• Similarity of the Optical-IR and Gamma-Ray Time Variability of Fermi Blazars
• The WISE gamma-ray strip parametrization: the nature of the gamma-ray Active Galactic Nuclei of Uncertain type
• The WISE Blazar-Like Radio-Loud Sources: An All-Sky Catalog Of Candidate Gamma-Ray Blazars
• A Statistical Approach to Recognizing Source Classes for Unassociated Sources in the First Fermi-LAT Catalog
• Ultraviolet and Multiwavelength Variability of the Blazar 3C 279: Evidence for Thermal Emission
• Infrared Colors of the gamma-ray detected blazars
• A simplified view of blazars: the gamma-ray case
• A Northern Survey of Gamma-Ray Blazar Candidates
• Flare-like variability of the Mg IIλ2800Å emission line in the gamma-ray blazar 3C 454.3
• Unveiling the nature of the unidentified gamma-ray sources I: a new method for the association of gamma-ray blazars
• The classification of BL Lacertae objects: the Ca H&K break
• Optical Flux and Spectral Variability of Blazars
• Two new catalogs of blazar candidates in the WISE infrared sky
• Stringent Constraints On The Dark Matter Annihilation Cross Section From Subhalo Searches With The Fermi Gamma-Ray Space Telescope
• Discovery of Variability in the Very High Energy Gamma-Ray Emission of 1ES 1218+304 with VERITAS
• Optical spectroscopic observations of gamma-ray blazars candidates I: preliminary results
• Optical spectroscopic observations of $\gamma$-ray blazar candidates VI. Further observations from TNG, WHT, OAN, SOAR and Magellan telescopes
• The Extragalactic Gamma-ray Sky in the Fermi era
• The evolution of quiescent galaxies at high redshift (z > 1.4)
• Australia Telescope Compact Array observations of Fermi unassociated sources
• 1WHSP: an IR-based sample of $\sim$1,000 VHE $\gamma$-ray blazar candidates
• Unveiling the nature of the unidentified gamma-ray sources II: radio, infrared and optical counterparts of the gamma-ray blazar candidates
• Optical spectroscopic observations of blazars and gamma-ray blazar candidates in the Sloan Digital Sky Survey Data Release Nine
• Identification of the Early Fermi LAT Gamma-Ray Bright Objects with Extragalactic VLBI sources
• Unveiling the nature of the unidentified gamma-ray sources III: gamma-ray blazar-like counterparts at low radio frequencies
• Unveiling the nature of the unidentified gamma-ray sources IV: the $\text{Swift}$ catalog of potential X-ray counterparts
• New Associations of Gamma-Ray Sources from the Fermi Second Source Catalog
• Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. V. TNG, KPNO, and OAN Observations of Blazar Candidates of Uncertain Type in the Northern Hemisphere
• Optical spectroscopic observations of gamma-ray blazar candidates II. The 2013 KPNO campaign in the Northern Hemisphere
• Unidentifed gamma-ray sources: hunting gamma-ray blazars
• Optical spectroscopic observations of gamma-ray blazar candidates III. The 2013/2014 campaign in the Southern Hemisphere
• Blue Fermi Flat Spectrum Radio Quasars
• BL Lac candidates for TeV observations
• An Excess of Mg II Absorbers in BL Lac Objects
• The Gamma-ray Blazar Quest: new optical spectra, state of art and future perspectives
• Doppler Boosting, Superluminal Motion, and the Kinematics of AGN Jets
• Hunting for treasures among the Fermi unassociated sources: a multi-wavelength approach
• Optical spectroscopic observations of gamma-ray blazar candidates IV. Results of the 2014 follow-up campaign
• Search for gamma-ray-emitting active galactic nuclei in the Fermi-LAT unassociated sample using machine learning
• The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Quasar Survey: the 4th and 5th Data Release
• Dark matter subhaloes as gamma-ray sources and candidates in the first Fermi-LAT catalogue
• A simplified view of blazars: contribution to the X-ray and gamma-ray cosmic backgrounds
• Unveiling the nature of the unidentified gamma-ray sources V: analysis of the radio candidates with the kernel density estimation
• Refining the associations of the Fermi Large Area Telescope Source Catalogs
• The optical variability of flat-spectrum radio quasars in the SDSS stripe 82 region
• Optical spectroscopic survey of a sample of Unidentified Fermi objects
• The Infrared-Gamma-Ray Connection: A WISE View of the Extragalactic Gamma-Ray Sky
• A Time Resolved Study of the Broad Line Region in Blazar 3C 454.3
• Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. VII. Follow-up Campaign in the Southern Hemisphere
• 3FGLzoo. Classifying 3FGL Unassociated Fermi-LAT Gamma-ray Sources by Artificial Neural Networks
• The ROSAT BRIGHT survey: I. Identification of an AGN sample with hard ROSAT X-ray spectra
• The colours of BL Lac objects: a new approach to their classification
• High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars
• The UV-bright Quasar Survey (UVQS): DR1
• Radio Follow-up on all Unassociated Gamma-ray Sources from the Third Fermi Large Area Telescope Source Catalog
• The Nature of Transition Blazars
• Optical spectroscopic survey of a sample of Unidentified Fermi objects: II
• Multiband Diagnostics of Unidentified 1FGL Sources with Suzaku and Swift X-ray Observations
• Multi-wavelength Intra-day Variability and Quasi-periodic Oscillation in Blazars
• Optical archival spectra of blazar candidates of uncertain type in the 3${}^{rd}$ Fermi Large Area Telescope Catalog
• Is BL Lacertae an "orphan" AGN? Multiband and spectroscopic constraints on the parent population
• Unveiling the nature of the unidentified gamma-ray sources VI: gamma-ray blazar candidates in the WISH survey and their radio properties
• Long term variability and correlation study of the blazar 3C 454.3 in radio, NIR and optical wavebands
• VERITAS detection of $\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observations
• Optical spectroscopy of BL Lac objects: TeV candidates
• Spectroscopy of 10 gamma-ray BL Lac objects at high redshift
• Optical spectroscopic observations of gamma-ray blazar candidates VIII: the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR telescopes
• Radio Weak BL Lac objects in the Fermi era
• Chandra X-ray Observations of the Two Brightest Unidentified High Galactic Latitude Fermi-LAT gamma-ray Sources
• Flare-like Variability of the Mg~II $\lambda$2798 Å Emission Line and UV Fe~II band in the Blazar CTA~102
• High redshift BL Lac objects: spectroscopy of candidates
• The Time-Domain Spectroscopic Survey: Target Selection for Repeat Spectroscopy
• A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift
• Revealing the Nature of Blazar Radio Cores through Multi-Frequency Polarization Observations with the Korean VLBI Network
• Spectroscopy of Optically Selected BL Lac Objects and their gamma-ray emission
• Classification of New X-ray Counterparts for Fermi Unassociated Gamma Ray Sources Using the Swift X-Ray Telescope
• Optical spectroscopic observations of gamma-ray blazar candidates. IX. Optical archival spectra and further observations from SOAR and OAGH
• Optical spectroscopic observations of gamma-ray blazar candidates. X. Results from the 2018--2019 SOAR and OAN-SPM observations of blazar candidates of uncertain type
• Identifying the 3FHL catalog: CTIO results
• Swift/XRT counterparts to unassociated Fermi high-energy LAT sources
• Optical spectroscopic observations of low-energy counterparts of Fermi-LAT gamma-ray sources
• Optical characterization of WISE selected blazar candidates
• Identification of New Gamma-Ray Blazar Candidates With Multifrequency Archival Observations
• Multi-scale time- and frequency-domain likelihood analysis with photon weights
• Intra-Night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J C Bhattacharya Telescope
• New high-z BL Lacs using the photometric method with Swift and SARA
• Radio and optical intra-day variability observations of five blazars
• Long-term optical spectroscopic variations in blazar 3C 454.3
• FERMI transient J1544-0649: a flaring radio-weak BL Lac
• The changing look of PKS 2149-306
• The $\gamma$-ray sky seen at X-ray energies I. Searching for the connection between X-rays and $\gamma$-rays in Fermi BL Lac objects
• ZBLLAC -- A spectroscopic database of BL Lacertae objects
• Multiwavelength analysis and the difference in the behavior of the spectral features during the 2010 and 2014 flaring periods of the blazar 3C 454.3
• Probing the unidentified Fermi blazar-like population using optical polarization and machine learning
• The $\gamma$-ray sky seen at X-ray energies II: the Swift hunt of Fermi BL Lac objects among unidentified gamma-ray sources
• Optical spectroscopic classification of a selection of Southern Hemisphere Fermi-LAT unclassified blazars
• Diversity of gamma-ray and Radio Variabilities of Bright Blazars and Implications for gamma-ray Emission Location
• Search for AGN counterparts of unidentified Fermi-LAT sources with optical polarimetry: Demonstration of the technique

Cited by in corpus (11)

• Incremental Fermi Large Area Telescope Fourth Source Catalog
• The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope -- Data Release 3
• Constraints on the intergalactic magnetic field using Fermi-LAT and H.E.S.S. blazar observations
• The Estimation of Fundamental Physics Parameters for Fermi-LAT Blazars
• Autoencoding Galaxy Spectra II: Redshift Invariance and Outlier Detection
• An extensive study of blazar broad emission line: Changing-look blazars and Baldwin effect
• The Physical Properties of Changing-look Blazars
• Radio properties of high-redshift galaxies at $z\ge 1$
• The physical properties of candidate neutrino-emitter blazars
• A New Sample of Gamma-Ray Emitting Jetted Active Galactic Nuclei -- Preliminary Results
• Deepening gamma-ray point-source catalogues with sub-threshold information