Two New Catalogs of Blazar Candidates in the <i>WISE</i> Infrared Sky

D’Abrusco, R.; Crespo, Nuria Álvarez; Massaro, F.; Campana, R.; Chavushyan, V.; Landoni, M.; Franca, F. La; Masetti, N.; Milisavljevic, Dan; Paggi, A.; Ricci, F.; Smith, H. A.

doi:10.3847/1538-4365/ab16f4

Cited by 68 publications

(74 citation statements)

References 95 publications

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“…About 57% (906 out of 1580) of ABC sources are detected in all four WISE bands. This has allowed us to re-examine the selection of γ-ray blazars by means of mid-IR colors discussed by D'Abrusco et al (2019). Making use of the KDE contours in the WISE color-color diagrams containing 90% of WISEdetected 4FGL blazar subclasses, we were able to classify about 80% (715 out of 906) of the ABC WISE-detected sources as candidate γ-ray blazar.…”

Section: Discussionmentioning

confidence: 99%

A new multiwavelength census of blazars

Paggi

Bonato

Raiteri

et al. 2020

A&A

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Context. Blazars are the rarest and most powerful active galactic nuclei. They play a crucial and expanding role in the multifrequency and multimessenger astrophysics of today. Dominating the high-energy extragalactic sky, they have been recently associated with high-energy astrophysical neutrinos and they may be among the accelerators of the ultra-high energy cosmic rays. Current blazar catalogs, however, are incomplete and they are depleted, in particular, at low Galactic latitudes. Aims. Our study is aimed at augmenting the current blazar census, starting from a sample of ALMA calibrators that provides more homogeneous sky coverage, especially at low Galactic latitudes, to build a catalog of blazar candidates that can provide candidate counterparts to unassociated γ-ray sources and sources of high-energy neutrino emission or ultra-high energy cosmic rays. Methods. Based on the ALMA Calibrator Catalog, we compiled a selection of 1580 ALMA Blazar Candidates (ABCs) for which we collected multiwavelength information, including Gaia photometric, parallax, and proper motion data, as well as SDSS and LAMOST photometric and spectral data, WISE photometric data, X-ray (Swift-XRT, Chandra-ACIS and XMM-Newton-EPIC) count-rates and spectra, and Fermi-LAT fluxes and spectral slopes. We also compared our ALMA Blazar Candidates with existing blazar catalogs, such as 4FGL, 3HSP, WIBRaLS2, and the KDEBLLACS. Results. The ABC catalog fills in the gaps with regard to low Galactic latitude sources in current blazar catalogs. By cross-matching this catalog with Gaia DR2, SDSS DR12, LAMOST DR5, AllWISE, and 4FGL catalogs, we obtained 805, 295, 31, 1311, and 259 matches, respectively. ALMA Blazar Candidates are significantly dimmer than known blazars in the Gaia g band, while the difference in the Gaia b − r color between the two populations is less pronounced. Also, ABC sources appear bluer in SDSS than known blazars, although with low statistical significance. Most ABCs classified as QSO and BL Lac fall into the SDSS color regions of low redshift quasars, with some QSOs entering the regions of higher redshift quasars. We collected 110 optical spectra in SDSS DR12 and LAMOST DR5, which mostly classify the corresponding sources as QSO (98), while 12 sources turned out to be galactic objects. Regarding the WISE colors, we found that ABC sources are significantly bluer than known blazars in the w2 − w3 and w3 − w4 colors. In X-ray, we detected 173 ABCs and we were able to extract X-ray spectra for 92 of them. Our sources are, on average, similar in the X-ray band to known blazars in terms of count rates and spectral slopes, implying that our sample covers the same region of the blazar parameter space in this band. A comparison of γ-ray properties shows that the ABCs are, on average, dimmer and that their γ-ray spectra are softer than known blazars, indicating a significant contribution on the part of FSRQ sources. Making use of WISE colors, we classified 715 ABCs as candidate γ-ray blazar of different classes. Conclusions. We built a new catalog of 1580 candidate blazars with a rich multiwavelength data-set, filling in the gaps for low Galactic latitude sources in current blazar catalogs. This will be particularly important for the identification of the source population of high-energy neutrinos or ultra-high energy cosmic rays, or to verify the Gaia optical reference frame. In addition, ALMA Blazar Candidates can be investigated both through optical spectroscopic observation campaigns or through repeated photometric observations for variability studies. In this context, the data collected by the upcoming LSST surveys will provide a key tool for investigating the possible blazar nature of these sources.

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Section: Discussionmentioning

confidence: 99%

A new multiwavelength census of blazars

Paggi

Bonato

Raiteri

et al. 2020

A&A

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“…The color uncertainty ellipses of each source in KDEBLLACS must be fully contained in this 90% contour. Sources in KDEBLLACS are radio-loud according to the q 12 parameter, defined as q 12 = log(S 12µm /S radio ), with S 12µm and S radio being the flux densities at 12µm and in radio respectively (D'Abrusco et al 2019).…”

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confidence: 99%

“…One of the catalogs that provides the largest number of associated blazar candidates for Fermi catalogs is the WISE Blazar-Like Radio-Loud Sources catalog (WIBRaLS;D'Abrusco et al 2014D'Abrusco et al , 2019. Selected sources in the WIBRaLS are detected in all four mid-IR WISE bands (nominally at 3.4, 4.6, 12 and 22 µm) and show mid-IR colors similar to confirmed Fermi blazars.…”

Section: Introductionmentioning

confidence: 99%

Optical characterization of WISE selected blazar candidates

Menezes

Peña-Herazo

Marchesini

et al. 2019

A&A

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Context. Over the last decade more than five thousand γ-ray sources were detected by the Large Area Telescope (LAT) on board Fermi Gamma-ray Space Telescope. Given the positional uncertainty of the telescope, nearly 30% of these sources remain without an obvious counterpart in lower energies. This motivated the release of new catalogs of γ-ray counterpart candidates and several follow up campaigns in the last decade. Aims. Recently, two new catalogs of blazar candidates were released, they are the improved and expanded version of the WISE Blazar-Like Radio-Loud Sources (WIBRaLS2) catalog and the Kernel Density Estimation selected candidate BL Lacs (KDEBLLACS) catalog, both selecting blazar-like sources based on their infrared colors from the Wide-field Infrared Survey Explorer (WISE). In this work we characterized these two catalogs, clarifying the true nature of their sources based on their optical spectra from SDSS data release 15, thus testing how efficient they are in selecting true blazars. Methods. We first selected all WIBRaLS2 and KDEBLLACS sources with available optical spectra in the footprint of Sloan Digital Sky Survey data release 15. Then we analyzed these spectra to verify the nature of each selected candidate and see which fraction of the catalogs is composed by spectroscopically confirmed blazars. Finally, we evaluated the impact of selection effects, specially those related to optical colors of WIBRaLS2/KDEBLLACS sources and their optical magnitude distributions. Results. We found that at least ∼ 30% of each catalog is composed by confirmed blazars, with quasars being the major contaminants in the case of WIBRaLS2 (≈ 58%) and normal galaxies in the case of KDEBLLACS (≈ 38.2%). The spectral analysis also allowed us to identify the nature of 11 blazar candidates of uncertain type (BCUs) from the Fermi-LAT 4th Point Source Catalog (4FGL) and to find 25 new BL Lac objects.

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“…Bottom: same as upper panel but for W2-W3 × W3-W4. methods, as the Fermi-LAT γ-ray blazars are known to occupy a distinct area in the WISE MIR color-color-color diagram(D'Abrusco et al 2012;D'Abrusco et al 2019).…”

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confidence: 99%

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

Menezes

Amaya-Almazán

Marchesini

et al. 2020

Astrophys Space Sci

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The fourth Fermi Large Area Telescope Source Catalog (4FGL) lists over 5000 γ-ray sources with statistical significance above 4σ. About 23% of the sources listed in this catalog are unidentified/unassociated γ-ray sources while ∼ 26% of the sources are classified as blazar candidates of uncertain type (BCUs), lacking optical spectroscopic information. To probe the blazar nature of candidate counterparts of UGSs and BCUs, we started our optical spectroscopic follow up campaign in 2012, which up to date account for more than 350 observed sources. In this paper, the tenth of our campaign, we report on the spectroscopic observations of 37 sources, mostly BCUs, whose observations were carried out predominantly at the Observatorio Astronómico Nacional San Pedro Mártir and the Southern Astrophysical Research Observatory between August 2018 and September 2019. We confirm the BL Lac nature of 27 sources and the flat spectrum radio quasar nature of three sources. The remaining ones are classified as six BL Lacs galaxydominated and one normal galaxy. We were also able to measure the redshifts for 20 sources, including 10 BL Lacs. As in previous analyses, the largest fraction of BCUs revealed to be BL Lac objects.

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Two New Catalogs of Blazar Candidates in the WISE Infrared Sky

Cited by 68 publications

References 95 publications

A new multiwavelength census of blazars

A new multiwavelength census of blazars

Optical characterization of WISE selected blazar candidates

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

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