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Showing 1-20 of about 76 results.
Extended X-Ray Emission around FR II Radio Galaxies: Hot Spots, Lobes, and Galaxy ClustersJimenez-Gallardo, A.Massaro, F.Paggi, A.D'Abrusco, RaffaelePrieto, M. A.Peña-Herazo, H. A.Berta, V.Ricci, F.Stuardi, C.Wilkes, Belinda J.O'Dea, C. P.Baum, S. A.Kraft, Ralph P.Forman, William R.Jones-Forman, ChristineMingo, B.Liuzzo, E.Balmaverde, B.Capetti, A.Missaglia, V.Hardcastle, M. J.Baldi, R. D.Morabito, L. K.DOI: info:10.3847/1538-4365/abcecdv. 25231
Jimenez-Gallardo, A., Massaro, F., Paggi, A., D'Abrusco, Raffaele, Prieto, M. A., Peña-Herazo, H. A., Berta, V., Ricci, F., Stuardi, C., Wilkes, Belinda J., O'Dea, C. P., Baum, S. A., Kraft, Ralph P., Forman, William R., Jones-Forman, Christine, Mingo, B., Liuzzo, E., Balmaverde, B., Capetti, A., Missaglia, V., Hardcastle, M. J., Baldi, R. D., and Morabito, L. K. 2021. "Extended X-Ray Emission around FR II Radio Galaxies: Hot Spots, Lobes, and Galaxy Clusters." The Astrophysical Journal Supplement Series 252:31. https://doi.org/10.3847/1538-4365/abcecd
ID: 159641
Type: article
Authors: Jimenez-Gallardo, A.; Massaro, F.; Paggi, A.; D'Abrusco, Raffaele; Prieto, M. A.; Peña-Herazo, H. A.; Berta, V.; Ricci, F.; Stuardi, C.; Wilkes, Belinda J.; O'Dea, C. P.; Baum, S. A.; Kraft, Ralph P.; Forman, William R.; Jones-Forman, Christine; Mingo, B.; Liuzzo, E.; Balmaverde, B.; Capetti, A.; Missaglia, V.; Hardcastle, M. J.; Baldi, R. D.; Morabito, L. K.
Abstract: We present a systematic analysis of the extended X-ray emission discovered around 35 FR II radio galaxies from the revised Third Cambridge Catalog (3CR) Chandra Snapshot Survey with redshifts between 0.05 and 0.9. We aimed to (i) test for the presence of extended X-ray emission around FR II radio galaxies, (ii) investigate whether the extended emission origin is due to inverse Compton (IC) scattering of seed photons arising from the cosmic microwave background (CMB) or thermal emission from an intracluster medium (ICM), and (iii) test the impact of this extended emission on hot-spot detection. We investigated the nature of the extended X-ray emission by studying its morphology and compared our results with low-frequency radio observations (i.e., ∼150 MHz) in the TGSS and LOFAR archives, as well as with optical images from Pan-STARRS. In addition, we optimized a search for X-ray counterparts of hot spots in 3CR FR II radio galaxies. We found statistically significant extended emission (>3σ confidence level) along the radio axis of ∼90% and in the perpendicular direction of ∼60% of the galaxies in our sample. We confirmed the detection of seven hot spots in the 0.5-3 keV energy range. In the cases where the emission in the direction perpendicular to the radio axis is comparable to that along the radio axis, we suggest that the underlying radiative process is thermal emission from the ICM. Otherwise, the dominant radiative process is likely nonthermal IC/CMB emission from lobes. We found that nonthermal IC/CMB is the dominant process in ∼70% of the sources in our sample, while thermal emission from the ICM dominates in ∼15% of them.
Extended X-Ray Emission in Compton Thick AGN with Deep Chandra ObservationsJones, Mackenzie L.Parker, KieranFabbiano, G.Elvis, MartinMaksym, W. P.Paggi, A.Ma, JingzheKarovska, M.Siemiginowska, AnetaWang, JunfengDOI: info:10.3847/1538-4357/abe128v. 91019
Jones, Mackenzie L., Parker, Kieran, Fabbiano, G., Elvis, Martin, Maksym, W. P., Paggi, A., Ma, Jingzhe, Karovska, M., Siemiginowska, Aneta, and Wang, Junfeng. 2021. "Extended X-Ray Emission in Compton Thick AGN with Deep Chandra Observations." The Astrophysical Journal 910:19. https://doi.org/10.3847/1538-4357/abe128
ID: 159608
Type: article
Authors: Jones, Mackenzie L.; Parker, Kieran; Fabbiano, G.; Elvis, Martin; Maksym, W. P.; Paggi, A.; Ma, Jingzhe; Karovska, M.; Siemiginowska, Aneta; Wang, Junfeng
Abstract: We present the spatial analysis of five Compton thick (CT) active galactic nuclei (AGNs), including MKN 573, NGC 1386, NGC 3393, NGC 5643, and NGC 7212, for which high-resolution Chandra observations are available. For each source, we find hard X-ray emission (>3 keV) extending to ∼kiloparsec scales along the ionization cone, and for some sources, in the cross-cone region. This collection represents the first, high-signal sample of CT AGN with extended hard X-ray emission for which we can begin to build a more complete picture of this new population of AGN. We investigate the energy dependence of the extended X-ray emission, including possible dependencies on host galaxy and AGN properties, and find a correlation between the excess emission and obscuration, suggesting a connection between the nuclear obscuring material and the galactic molecular clouds. Furthermore, we find that the soft X-ray emission extends farther than the hard X-rays along the ionization cone, which may be explained by a galactocentric radial dependence on the density of molecular clouds due to the orientation of the ionization cone with respect to the galactic disk. These results are consistent with other CT AGN with observed extended hard X-ray emission (e.g., ESO 428-G014 and the Ma et al. CT AGN sample), further demonstrating the ubiquity of extended hard X-ray emission in CT AGN.
Peering into the extended X-ray emission on megaparsec scale in 3C 187Paggi, A.Massaro, F.Peña-Herazo, H. A.Missaglia, V.Ricci, F.Stuardi, C.Kraft, R. P.Tremblay, G. R.Baum, S. A.Wilkes, B. J.DOI: info:10.1051/0004-6361/202039813v. 647A79
Paggi, A., Massaro, F., Peña-Herazo, H. A., Missaglia, V., Ricci, F., Stuardi, C., Kraft, R. P., Tremblay, G. R., Baum, S. A., and Wilkes, B. J. 2021. "Peering into the extended X-ray emission on megaparsec scale in 3C 187." Astronomy and Astrophysics 647:A79. https://doi.org/10.1051/0004-6361/202039813
ID: 159555
Type: article
Authors: Paggi, A.; Massaro, F.; Peña-Herazo, H. A.; Missaglia, V.; Ricci, F.; Stuardi, C.; Kraft, R. P.; Tremblay, G. R.; Baum, S. A.; Wilkes, B. J.
Abstract: Context. The diffuse X-ray emission surrounding radio galaxies is generally interpreted either as due to inverse Compton scattering of nonthermal radio-emitting electrons on the cosmic microwave background (IC/CMB), or as due to thermal emission arising from the hot gas of the intergalactic medium (IGM) permeating galaxy clusters hosting such galaxies, or as a combination of both. In this work, we present an imaging and spectral analysis of Chandra observations for the radio galaxy 3C 187 to investigate its diffuse X-ray emission and constrain the contribution of these various physical mechanisms.
Aims: The main goals of this work are the following: (i) to evaluate the extension of the diffuse X-ray emission from this source; (ii) to investigate the two main processes, IC/CMB and thermal emission from the IGM, which can account for the origin of this emission; and (iii) to test the possibility that 3C 187 belongs to a cluster of galaxies, which can account for the observed diffuse X-ray emission.
Methods: To evaluate the extension of the X-ray emission around 3C 187, we extracted surface flux profiles along and across the radio axis. We also extracted X-ray spectra in the region of the radio lobes and in the cross-cone region to estimate the contribution of the nonthermal (IC/CMB) and thermal (IGM) processes to the observed emission, making use of radio (VLA and GMRT) data to investigate the multiwavelength emission arising from the lobes. We collected Pan-STARRS photometric data to investigate the presence of a galaxy cluster hosting 3C 187, looking for the presence of a "red sequence" in the source field in the form of a tight clustering of galaxies in the color space. In addition, we made use of observations performed with the COSMOS spectrograph at the Victor Blanco Telescope to estimate the redshift of the sources in the field of 3C 187 to verify if they are gravitationally bound, as we would expect in a cluster of galaxies.
Results: The diffuse X-ray emission around 3C 187 is found to extend in the soft 0.3 - 3 keV band up to ∼850 kpc along the radio lobe direction and ∼530 kpc in the cross-cone direction, and it appears enhanced in correspondence with the radio lobes. Spectral X-ray analysis in the cross-cones indicates a thermal origin for the emission in this region with a temperature ∼4 keV. In the radio lobes, the X-ray spectral analysis in combination with the radio data suggests a dominant IC/CMB radiation in these regions, however we do not rule out a significant thermal contribution. Assuming that the radiation observed in the radio lobes is due to the IGM, the emission from the N and S cones can be interpreted as arising from hot gas with temperatures of ∼3 keV and ∼5 keV, respectively, and found to be in pressure equilibrium with the surrounding gas. Using Pan-STARRS optical data we found that 3C 187 belongs to a red sequence of ∼40 optical sources in the field whose color distribution is significantly different from background sources. We were able to collect optical spectra for only one of these cluster candidates and for 22 field (i.e., noncluster candidates) sources. While the latter show stellar spectra, the former feature a galactic spectrum with a redshift close to 3C 187 nucleus.
Conclusions: The diffuse X-ray emission around 3C 187 is elongated along the radio axis and enhanced in correspondence with the radio lobes. This indicates a morphological connection between the emission in the two energy bands and thus suggests a dominating IC/CMB mechanism in these regions. This scenario is reinforced by multiwavelength radio X-ray emission, which in these regions is compatible with IC/CMB radiation. The X-ray spectral analysis however does not rule out a significant contribution to the observed emission from thermal gas, which would be able to emit over tens of gigayears and in pressure equilibrium with the surroundings. Optical data indicate that 3C 187 may belong to a cluster of galaxies, whose IGM would contribute to the X-ray emission observed around the source. Additional X-ray and optical spectroscopic observations are however needed to secure these results and get a more clear picture of the physical processes at play in 3C 187.
Optical spectroscopic observations of gamma-ray blazar candidates. X. Results from the 2018-2019 SOAR and OAN-SPM observations of blazar candidates of uncertain typede Menezes, R.Amaya-Almazán, R. A.Marchesini, E. J.Peña-Herazo, H. A.Massaro, F.Chavushyan, V.Paggi, A.Landoni, M.Masetti, N.Ricci, F.D'Abrusco, RaffaeleLa Franca, F.Smith, Howard A.Milisavljevic, D.Tosti, G.Jiménez-Bailón, E.Cheung, C. C.DOI: info:10.1007/s10509-020-3727-5v. 36512
de Menezes, R., Amaya-Almazán, R. A., Marchesini, E. J., Peña-Herazo, H. A., Massaro, F., Chavushyan, V., Paggi, A., Landoni, M., Masetti, N., Ricci, F., D'Abrusco, Raffaele, La Franca, F., Smith, Howard A., Milisavljevic, D., Tosti, G., Jiménez-Bailón, E., and Cheung, C. C. 2020. "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." Astrophysics and Space Science 365:12. https://doi.org/10.1007/s10509-020-3727-5
ID: 156234
Type: article
Authors: de Menezes, R.; Amaya-Almazán, R. A.; Marchesini, E. J.; Peña-Herazo, H. A.; Massaro, F.; Chavushyan, V.; Paggi, A.; Landoni, M.; Masetti, N.; Ricci, F.; D'Abrusco, Raffaele; La Franca, F.; Smith, Howard A.; Milisavljevic, D.; Tosti, G.; Jiménez-Bailón, E.; Cheung, C. C.
Abstract: The fourth Fermi Large Area Telescope Source Catalog (4FGL) lists over 5000 γ -ray sources with statistical significance above 4 σ . 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 galaxy-dominated 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.
Revisiting the Complex Nuclear Region of NGC 6240 with ChandraFabbiano, GiuseppinaPaggi, A.Karovska, MargaritaElvis, MartinNardini, E.Wang, JunfengDOI: info:10.3847/1538-4357/abb5adv. 90249
Fabbiano, Giuseppina, Paggi, A., Karovska, Margarita, Elvis, Martin, Nardini, E., and Wang, Junfeng. 2020. "Revisiting the Complex Nuclear Region of NGC 6240 with Chandra." The Astrophysical Journal 902:49. https://doi.org/10.3847/1538-4357/abb5ad
ID: 158817
Type: article
Authors: Fabbiano, Giuseppina; Paggi, A.; Karovska, Margarita; Elvis, Martin; Nardini, E.; Wang, Junfeng
Abstract: We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5-5.9 keV), the redshifted Fe I Ka line (6.0-6.4 keV), and the redshifted Fe XXV line (6.4-6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches-(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images-we are able to resolve structures extending from ˜1 kpc to <200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ˜2" (˜1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120-210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe I Ka emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240.
Completing the 3CR Chandra Snapshot Survey: Extragalactic Radio Sources at High RedshiftJimenez-Gallardo, A.Massaro, F.Prieto, M. A.Missaglia, V.Stuardi, C.Paggi, A.Ricci, F.Kraft, Ralph P.Liuzzo, E.Tremblay, Grant R.Baum, S. A.O'Dea, C. P.Wilkes, Belinda J.Kuraszkiewicz, JoannaForman, William R.Harris, Dan E.DOI: info:10.3847/1538-4365/aba5a0v. 2507
Jimenez-Gallardo, A., Massaro, F., Prieto, M. A., Missaglia, V., Stuardi, C., Paggi, A., Ricci, F., Kraft, Ralph P., Liuzzo, E., Tremblay, Grant R., Baum, S. A., O'Dea, C. P., Wilkes, Belinda J., Kuraszkiewicz, Joanna, Forman, William R., and Harris, Dan E. 2020. "Completing the 3CR Chandra Snapshot Survey: Extragalactic Radio Sources at High Redshift." The Astrophysical Journal Supplement Series 250:7. https://doi.org/10.3847/1538-4365/aba5a0
ID: 157477
Type: article
Authors: Jimenez-Gallardo, A.; Massaro, F.; Prieto, M. A.; Missaglia, V.; Stuardi, C.; Paggi, A.; Ricci, F.; Kraft, Ralph P.; Liuzzo, E.; Tremblay, Grant R.; Baum, S. A.; O'Dea, C. P.; Wilkes, Belinda J.; Kuraszkiewicz, Joanna; Forman, William R.; Harris, Dan E.
Abstract: We present the analysis of nine radio sources belonging to the Third Cambridge Revised catalog (3CR) observed with Chandra during Cycle 20 in the redshift range between 1.5 and 2.5. This study completes the 3CR Chandra Snapshot Survey thus guaranteeing the X-ray coverage of all 3CR sources identified to date. This sample lists two compact steep spectrum sources, four radio galaxies, and three quasars. We detected X-ray emission from all nuclei, with the only exception of 3C 326.1 and 3C 454.1 and from radio lobes in six out of nine sources at a level of confidence larger than ∼5σ. We measured X-ray fluxes and luminosities for all nuclei and lobes in the soft (0.5-1 keV), medium (1-2 keV), and hard (2-7 keV) X-ray bands. Since the discovered X-ray extended emission is spatially coincident with the radio structure in all cases, its origin could be due to inverse Compton (IC) scattering of the cosmic microwave background (CMB) occurring in radio lobes.
Chandra Observations of NGC 7212: Large-scale Extended Hard X-Ray EmissionJones, Mackenzie L.Fabbiano, GiuseppinaElvis, MartinPaggi, A.Karovska, MargaritaMaksym, W. PeterSiemiginowska, AnetaRaymond, JohnDOI: info:10.3847/1538-4357/ab76c8v. 891133
Jones, Mackenzie L., Fabbiano, Giuseppina, Elvis, Martin, Paggi, A., Karovska, Margarita, Maksym, W. Peter, Siemiginowska, Aneta, and Raymond, John. 2020. "Chandra Observations of NGC 7212: Large-scale Extended Hard X-Ray Emission." The Astrophysical Journal 891:133. https://doi.org/10.3847/1538-4357/ab76c8
ID: 156368
Type: article
Authors: Jones, Mackenzie L.; Fabbiano, Giuseppina; Elvis, Martin; Paggi, A.; Karovska, Margarita; Maksym, W. Peter; Siemiginowska, Aneta; Raymond, John
Abstract: Recent observations of nearby Compton thick (CT) active galactic nuclei (AGNs) with Chandra have resolved hard (>3 keV) X-ray emission extending out from the central supermassive black hole to kiloparsec scales, challenging the long-held belief that the characteristic hard X-ray continuum and fluorescent Fe K lines originate in the inner ∼parsec due to the excitation of obscuring material. In this paper we present the results of the most recent Chandra ACIS-S observations of NGC 7212, a CT AGN in a compact group of interacting galaxies, with a total effective exposure of ∼150 ks. We find ∼20% of the observed emission is found outside of the central kiloparsec, with ∼17% associated with the soft X-rays, and ∼3% with hard X-ray continuum and Fe K line. This emission is extended both along the ionization cone and in the cross-cone direction up to ∼3.8 kpc scales. The spectrum of NGC 7212 is best represented by a mixture of thermal and photoionization models that indicate the presence of complex gas interactions. These observations are consistent with what is observed in other CT AGN (e.g., ESO 428-G014, NGC 1068), providing further evidence that this may be a common phenomenon. High-resolution observations of extended CT AGN provide an especially valuable environment for understanding how AGN feedback impacts host galaxies on galactic scales.
Temperature profiles of hot gas in early-type galaxiesKim, Dong-WooTraynor, LiamPaggi, AlessandroO'Sullivan, EwanAnderson, CraigBurke, DouglasD'Abrusco, RaffaeleFabbiano, GiuseppinaFruscione, AntonellaLauer, JenniferMcCollough, MichaelMorgan, DouglasMossman, AmyVrtilek, SaeqaTrinchieri, GinevraDOI: info:10.1093/mnras/stz3530v. 4922095–2118
Kim, Dong-Woo, Traynor, Liam, Paggi, Alessandro, O'Sullivan, Ewan, Anderson, Craig, Burke, Douglas, D'Abrusco, Raffaele, Fabbiano, Giuseppina, Fruscione, Antonella, Lauer, Jennifer, McCollough, Michael, Morgan, Douglas, Mossman, Amy, Vrtilek, Saeqa, and Trinchieri, Ginevra. 2020. "Temperature profiles of hot gas in early-type galaxies." Monthly Notices of the Royal Astronomical Society 492:2095– 2118. https://doi.org/10.1093/mnras/stz3530
ID: 155834
Type: article
Authors: Kim, Dong-Woo; Traynor, Liam; Paggi, Alessandro; O'Sullivan, Ewan; Anderson, Craig; Burke, Douglas; D'Abrusco, Raffaele; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer; McCollough, Michael; Morgan, Douglas; Mossman, Amy; Vrtilek, Saeqa; Trinchieri, Ginevra
Abstract: Using the data products of the Chandra Galaxy Atlas (Kim et al.), we have investigated the radial profiles of the hot gas temperature in 60 early-type galaxies (ETGs). Considering the characteristic temperature and radius of the peak, dip, and break (when scaled by the gas temperature and virial radius of each galaxy), we propose a universal temperature profile of the hot halo in ETGs. In this scheme, the hot gas temperature peaks at RMAX = 35 ± 25 kpc (or ∼0.04 RVIR) and declines both inward and outward. The temperature dips (or breaks) at RMIN (or RBREAK) = 3-5 kpc (or ∼0.006 RVIR). The mean slope between RMIN (RBREAK) and RMAX is 0.3 ± 0.1. Allowing for selection effects and observational limits, we find that the universal temperature profile can describe the temperature profiles of 72 per cent (possibly up to 82 per cent) of our ETG sample. The remaining ETGs (18 per cent) with irregular or monotonically declining profiles do not fit the universal profile and require another explanation. The temperature gradient inside RMIN (RBREAK) varies widely, indicating different degrees of additional heating at small radii. Investigating the nature of the hot core (HC with a negative gradient inside RMIN), we find that HC is most clearly visible in small galaxies. Searching for potential clues associated with stellar, active galactic nucleus (AGN) feedback, and gravitational heating, we find that HC may be related to recent star formation. But we see no clear evidence that AGN feedback and gravitational heating play any significant role for HC.
Optical spectroscopic observations of low-energy counterparts of Fermi-LAT ?-ray sourcesPeña-Herazo, H. A.Amaya-Almazán, R. A.Massaro, F.de Menezes, R.Marchesini, E. J.Chavushyan, V.Paggi, A.Landoni, M.Masetti, N.Ricci, F.D'Abrusco, RaffaeleCheung, C. C.La Franca, F.Smith, H. A.Milisavljevic, D.Jiménez-Bailón, E.Patiño-Álvarez, V. M.Tosti, G.DOI: info:10.1051/0004-6361/202037978v. 643A103
Peña-Herazo, H. A., Amaya-Almazán, R. A., Massaro, F., de Menezes, R., Marchesini, E. J., Chavushyan, V., Paggi, A., Landoni, M., Masetti, N., Ricci, F., D'Abrusco, Raffaele, Cheung, C. C., La Franca, F., Smith, H. A., Milisavljevic, D., Jiménez-Bailón, E., Patiño-Álvarez, V. M., and Tosti, G. 2020. "Optical spectroscopic observations of low-energy counterparts of Fermi-LAT ?-ray sources." Astronomy and Astrophysics 643:A103. https://doi.org/10.1051/0004-6361/202037978
ID: 158785
Type: article
Authors: Peña-Herazo, H. A.; Amaya-Almazán, R. A.; Massaro, F.; de Menezes, R.; Marchesini, E. J.; Chavushyan, V.; Paggi, A.; Landoni, M.; Masetti, N.; Ricci, F.; D'Abrusco, Raffaele; Cheung, C. C.; La Franca, F.; Smith, H. A.; Milisavljevic, D.; Jiménez-Bailón, E.; Patiño-Álvarez, V. M.; Tosti, G.
Abstract: Context. A significant fraction of all ?-ray sources detected by the Large Area Telescope aboard the Fermi satellite is still lacking a low-energy counterpart. In addition, there is still a large population of ?-ray sources with associated low-energy counterparts that lack firm classifications. In the last 10 years we have undertaken an optical spectroscopic campaign to address the problem of unassociated or unidentified ?-ray sources (UGSs), mainly devoted to observing blazars and blazar candidates because they are the largest population of ?-ray sources associated to date.
Aims: Here we describe the overall impact of our optical spectroscopic campaign on sources associated in Fermi-LAT catalogs, coupled with objects found in the literature. In the literature search we kept track of efforts by different teams that presented optical spectra of counterparts or potential counterparts of Fermi-LAT catalog sources. Our summary includes an analysis of additional 30 newly collected optical spectra of counterparts or potential counterparts of Fermi-LAT sources of a previously unknown nature.
Methods: New spectra were acquired at the Blanco 4 m and OAN-SPM 2.1 m telescopes, and those available in the Sloan Digital Sky Survey (data release 15) archive.
Results: All new sources with optical spectra analyzed here are classified as blazars. Thanks to our campaign, altogether we discovered and classified 394 targets with an additional 123 objects collected from a literature search. We began our optical spectroscopic campaign between the release of the second and third Fermi-LAT source catalogs (2FGL and 3FGL, respectively), classified about 25% of the sources that had uncertain nature and discovered a blazar-like potential counterpart for ˜10% of UGSs listed therein. In the 4FGL catalog, about 350 Fermi-LAT sources have been classified to date thanks to our campaign.
Conclusions: The most elusive class of blazars are found to be BL Lacs since the largest fraction of Fermi-LAT sources targeted in our observations showed a featureless optical spectrum. The same conclusion applied to the literature spectra. Finally, we confirm the high reliability of mid-IR color-based methods to select blazar-like candidate counterparts of unassociated or unidentified ?-ray sources.
Full Tables B.1 and B.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/643/A103
Two New Catalogs of Blazar Candidates in the WISE Infrared SkyD'Abrusco, RaffaeleÁlvarez Crespo, NuriaMassaro, FrancescoCampana, RiccardoChavushyan, VahramLandoni, MarcoLa Franca, FabioMasetti, NicolaMilisavljevic, DanPaggi, AlessandroRicci, FedericaSmith, Howard A.DOI: info:10.3847/1538-4365/ab16f4v. 2424
D'Abrusco, Raffaele, Álvarez Crespo, Nuria, Massaro, Francesco, Campana, Riccardo, Chavushyan, Vahram, Landoni, Marco, La Franca, Fabio, Masetti, Nicola, Milisavljevic, Dan, Paggi, Alessandro, Ricci, Federica, and Smith, Howard A. 2019. "Two New Catalogs of Blazar Candidates in the WISE Infrared Sky." The Astrophysical Journal Supplement Series 242:4. https://doi.org/10.3847/1538-4365/ab16f4
ID: 151855
Type: article
Authors: D'Abrusco, Raffaele; Álvarez Crespo, Nuria; Massaro, Francesco; Campana, Riccardo; Chavushyan, Vahram; Landoni, Marco; La Franca, Fabio; Masetti, Nicola; Milisavljevic, Dan; Paggi, Alessandro; Ricci, Federica; Smith, Howard A.
Abstract: We present two catalogs of radio-loud candidate blazars whose Wide-Field Infrared Survey Explorer (WISE) mid-infrared colors are selected to be consistent with the colors of confirmed γ-ray-emitting blazars. The first catalog is the improved and expanded release of the WISE Blazar-like Radio-Loud Sources (WIBRaLS) catalog presented by D'Abrusco et al. It includes sources detected in all four WISE filters, spatially cross-matched with radio sources in one of three radio surveys and radio-loud based on their q 22 spectral parameter. WIBRaLS2 includes 9541 sources classified as BL Lacs, flat-spectrum radio quasars, or mixed candidates based on their WISE colors. The second catalog, called KDEBLLACS, based on a new selection technique, contains 5579 candidate BL Lacs extracted from the population of WISE sources detected in the first three WISE passbands ([3.4], [4.6], and [12]) only, whose mid-infrared colors are similar to those of confirmed, γ-ray BL Lacs. Members of KDBLLACS are also required to have a radio counterpart and be radio-loud based on the parameter q 12, defined similarly to the q 22 used for the WIBRaLS2. We describe the properties of these catalogs and compare them with the largest samples of confirmed and candidate blazars in the literature. We cross-match the two new catalogs with the most recent catalogs of γ-ray sources detected by the Fermi Large Area Telescope. Since spectroscopic observations of candidate blazars from the first WIBRaLS catalog within the uncertainty regions of γ-ray unassociated sources confirmed that ∼90% of these candidates are blazars, we anticipate that these new catalogs will again play an important role in the identification of the γ-ray sky.
Optical characterization of WISE selected blazar candidatesde Menezes, RanierePeña-Herazo, Harold A.Marchesini, Ezequiel J.D'Abrusco, RaffaeleMasetti, NicolaNemmen, RodrigoMassaro, FrancescoRicci, FedericaLandoni, MarcoPaggi, AlessandroSmith, Howard A.DOI: info:10.1051/0004-6361/201936195v. 630A55
de Menezes, Raniere, Peña-Herazo, Harold A., Marchesini, Ezequiel J., D'Abrusco, Raffaele, Masetti, Nicola, Nemmen, Rodrigo, Massaro, Francesco, Ricci, Federica, Landoni, Marco, Paggi, Alessandro, and Smith, Howard A. 2019. "Optical characterization of WISE selected blazar candidates." Astronomy and Astrophysics 630:A55. https://doi.org/10.1051/0004-6361/201936195
ID: 154630
Type: article
Authors: de Menezes, Raniere; Peña-Herazo, Harold A.; Marchesini, Ezequiel J.; D'Abrusco, Raffaele; Masetti, Nicola; Nemmen, Rodrigo; Massaro, Francesco; Ricci, Federica; Landoni, Marco; Paggi, Alessandro; Smith, Howard A.
Abstract: Context. Over the last decade more than five thousand γ-ray sources have been detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. Given the positional uncertainty of the telescope, nearly 30% of these sources remain without an obvious counterpart at lower energies. This has 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. These 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 characterize these two catalogs, clarifying the true nature of their sources based on their optical spectra from SDSS data release 15, thus testing their efficiency 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. We then analyzed these spectra to verify the nature of each selected candidate and to measure the fraction of the catalogs composed by spectroscopically confirmed blazars. Finally, we evaluated the impact of selection effects, especially 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 made up of 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 fourth Point Source Catalog (4FGL) and to find 25 new BL Lac objects.
X-Ray Photons in the CO 2-1 Lacuna of NGC 2110Fabbiano, GiuseppinaPaggi, A.Elvis, MartinDOI: info:10.3847/2041-8213/ab1c63v. 876L18
Fabbiano, Giuseppina, Paggi, A., and Elvis, Martin. 2019. "X-Ray Photons in the CO 2-1 "Lacuna" of NGC 2110." The Astrophysical Journal 876:L18. https://doi.org/10.3847/2041-8213/ab1c63
ID: 155158
Type: article
Authors: Fabbiano, Giuseppina; Paggi, A.; Elvis, Martin
Abstract: A recent Atacama Large Millimeter/submillimeter Array study of the Seyfert 2 active galactic nucleus (AGN) NGC 2110 by Rosario et al. has reported a remarkable lack of CO 2-1 emission from the circumnuclear region, where optical lines and H2 emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. As interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report the discovery of an extra-nuclear ∼1″ (∼170 pc) feature in the soft ( emission are observed, leading to the suggestion of excitation of the molecular clouds by the AGN. As interaction with X-ray photons could be the cause of this excitation, we have searched the archival Chandra data for corroborating evidence. We report the discovery of an extra-nuclear ∼1″ (∼170 pc) feature in the soft (2 emission in this region, which is devoid of CO 2-1 emission. The Chandra image completes the emerging picture of a multiphase circumnuclear medium excited by the X-rays from the AGN, with dense warm molecular clouds emitting in H2 but depleted of CO 2-1 line emission.
Deep Chandra Observations of ESO 428-G014. IV. The Morphology of the Nuclear Region in the Hard Continuum and Fe Kα LineFabbiano, GiuseppinaSiemiginowska, AnetaPaggi, AlessandroElvis, MartinVolonteri, M.Mayer, L.Karovska, MargaritaMaksym, W. PeterRisaliti, G.Wang, JunfengDOI: info:10.3847/1538-4357/aaf0a4v. 87069
Fabbiano, Giuseppina, Siemiginowska, Aneta, Paggi, Alessandro, Elvis, Martin, Volonteri, M., Mayer, L., Karovska, Margarita, Maksym, W. Peter, Risaliti, G., and Wang, Junfeng. 2019. "Deep Chandra Observations of ESO 428-G014. IV. The Morphology of the Nuclear Region in the Hard Continuum and Fe Kα Line." The Astrophysical Journal 870:69. https://doi.org/10.3847/1538-4357/aaf0a4
ID: 150426
Type: article
Authors: Fabbiano, Giuseppina; Siemiginowska, Aneta; Paggi, Alessandro; Elvis, Martin; Volonteri, M.; Mayer, L.; Karovska, Margarita; Maksym, W. Peter; Risaliti, G.; Wang, Junfeng
Abstract: We report the results of high-resolution subpixel imaging of the hard continuum and Fe Kα line of the Compton-thick (CT) active galactic nucleus (AGN) ESO 428-G014, observed with Chandra ACIS. While the 3–4 keV emission is dominated by an extended component, a single nuclear point source is prominent in the 4–6 keV range. Instead, two peaks of similar intensity, separated by ∼36 pc in projection on the plane of the sky are detected in the Fe Kα emission. The SE knot could be marginally associated with the heavily obscured hard continuum source. We discuss four possible interpretations of the nuclear morphology. (1) Given the bolometric luminosity and likely black hole mass of ESO 428-G014, we may be imaging two clumps of the CT obscuring torus in the Fe Kα line. (2) The Fe Kα knots may be connected with the fluorescent emission from the dusty bicone, or (3) with the light echo of a nuclear outburst. (4) We also explore the less likely possibility that we may be detecting the rare signature of merging nuclei. Considering the large-scale kiloparsec-size extent of the hard continuum and Fe Kα emission (Papers I and II), we conclude that the AGN in ESO 428-G014 has been active for at least 104 yr. Comparison with the models of Czerny et al. suggests high accretion rates during this activity.
LOFAR Observations of 4C+19.44: On the Discovery of Low-frequency Spectral Curvature in Relativistic Jet KnotsHarris, D. E.Moldón, J.Oonk, J. R. R.Massaro, F.Paggi, A.Deller, A.Godfrey, L.Morganti, R.Jorstad, S. G.DOI: info:10.3847/1538-4357/ab01ffv. 873No. 121
Harris, D. E., Moldón, J., Oonk, J. R. R., Massaro, F., Paggi, A., Deller, A., Godfrey, L., Morganti, R., and Jorstad, S. G. 2019. "LOFAR Observations of 4C+19.44: On the Discovery of Low-frequency Spectral Curvature in Relativistic Jet Knots." The Astrophysical Journal 873 (1):21. https://doi.org/10.3847/1538-4357/ab01ff
ID: 153343
Type: article
Authors: Harris, D. E.; Moldón, J.; Oonk, J. R. R.; Massaro, F.; Paggi, A.; Deller, A.; Godfrey, L.; Morganti, R.; Jorstad, S. G.
Chandra Early-type Galaxy AtlasKim, Dong-WooAnderson, Craig S.Burke, Douglas J.D'Abrusco, RaffaeleFabbiano, GiuseppinaFruscione, AntonellaLauer, JenniferMcCollough, MichaelMorgan, DouglasMossman, AmyO'Sullivan, EwanPaggi, AlessandroVrtilek, SaeqaTrinchieri, GinevraDOI: info:10.3847/1538-4365/ab0ca4v. 24136
Kim, Dong-Woo, Anderson, Craig S., Burke, Douglas J., D'Abrusco, Raffaele, Fabbiano, Giuseppina, Fruscione, Antonella, Lauer, Jennifer, McCollough, Michael, Morgan, Douglas, Mossman, Amy, O'Sullivan, Ewan, Paggi, Alessandro, Vrtilek, Saeqa, and Trinchieri, Ginevra. 2019. "Chandra Early-type Galaxy Atlas." The Astrophysical Journal Supplement Series 241:36. https://doi.org/10.3847/1538-4365/ab0ca4
ID: 155313
Type: article
Authors: Kim, Dong-Woo; Anderson, Craig S.; Burke, Douglas J.; D'Abrusco, Raffaele; Fabbiano, Giuseppina; Fruscione, Antonella; Lauer, Jennifer; McCollough, Michael; Morgan, Douglas; Mossman, Amy; O'Sullivan, Ewan; Paggi, Alessandro; Vrtilek, Saeqa; Trinchieri, Ginevra
Abstract: The hot interstellar medium (ISM) in early-type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. The structural features of the hot gas identified by Chandra observations point to key evolutionary mechanisms, (e.g., active galactic nuclei, AGN, and stellar feedback, merging history). In our Chandra Galaxy Atlas (CGA) project, taking full advantage of the Chandra capabilities, we systematically analyzed the archival Chandra data of 70 ETGs and produced uniform data products for the hot gas properties. The primary data products are spatially resolved 2D spectral maps of the hot gas from individual galaxies. We emphasize that new features can be identified in the spectral maps that are not readily visible in the surface brightness maps. The high-level images can be viewed at the dedicated CGA website, and the CGA data products can be downloaded to compare with data at other wavelengths and to perform further analyses. Using our data products, we address a few focused science topics.
CHEERS Results from NGC 3393. III. Chandra X-Ray Spectroscopy of the Narrow Line RegionMaksym, W. PeterFabbiano, GiuseppinaElvis, MartinKarovska, MargaritaPaggi, AlessandroRaymond, JohnWang, JunfengStorchi-Bergmann, ThaisaRisaliti, GuidoDOI: info:10.3847/1538-4357/aaf4f5v. 87294
Maksym, W. Peter, Fabbiano, Giuseppina, Elvis, Martin, Karovska, Margarita, Paggi, Alessandro, Raymond, John, Wang, Junfeng, Storchi-Bergmann, Thaisa, and Risaliti, Guido. 2019. "CHEERS Results from NGC 3393. III. Chandra X-Ray Spectroscopy of the Narrow Line Region." The Astrophysical Journal 872:94. https://doi.org/10.3847/1538-4357/aaf4f5
ID: 150511
Type: article
Authors: Maksym, W. Peter; Fabbiano, Giuseppina; Elvis, Martin; Karovska, Margarita; Paggi, Alessandro; Raymond, John; Wang, Junfeng; Storchi-Bergmann, Thaisa; Risaliti, Guido
Abstract: We present spatially resolved Chandra narrow-band imaging and imaging spectroscopy of NGC 3393. This galaxy hosts a Compton-thick Seyfert 2 active galactic nucleus (AGN) with sub-kpc bipolar outflows that are strongly interacting with the circumnuclear gas. We identify narrow-band excess emission associated with the Ne IX 0.905 keV transition (with likely contributions due to intermediate-state iron emission) that points to strong shocks driven by AGN feedback. Imaging spectroscopy resolves outflow-interstellar medium (ISM) interaction sites and the surrounding ISM at ∼100 pc scales, and suggests the presence of a hot AGN wind above the plane at radii beyond the shock sites. The cross-cone shows evidence for reprocessing of photoionization that has passed through gaps in the torus, and also for collisionally excited plasma that may be powered by a shock-confined equatorial outflow. Deep X-ray observations at subarcsecond resolution (such as may be performed very efficiently by Lynx, which would also energetically resolve the complex line emission) are necessary to eliminate model degeneracies and reduce uncertainties in local feedback properties.
The γ-ray sky seen at X-ray energies. I. Searching for the connection between X-rays and γ-rays in Fermi BL Lac objectsMarchesini, E. J.Paggi, A.Massaro, F.Masetti, N.D'Abrusco, RaffaeleAndruchow, I.de Menezes, R.DOI: info:10.1051/0004-6361/201936285v. 631A150
Marchesini, E. J., Paggi, A., Massaro, F., Masetti, N., D'Abrusco, Raffaele, Andruchow, I., and de Menezes, R. 2019. "The γ-ray sky seen at X-ray energies. I. Searching for the connection between X-rays and γ-rays in Fermi BL Lac objects." Astronomy and Astrophysics 631:A150. https://doi.org/10.1051/0004-6361/201936285
ID: 154594
Type: article
Authors: Marchesini, E. J.; Paggi, A.; Massaro, F.; Masetti, N.; D'Abrusco, Raffaele; Andruchow, I.; de Menezes, R.
Abstract: Context. BL Lac objects are an extreme type of active galactic nuclei (AGNs) that belong to the largest population of γ-ray sources: blazars. This class of AGNs shows a double-bumped spectral energy distribution that is commonly described in terms of a synchrotron self-Compton (SSC) emission process, whereas the low-energy component that dominates their emission between the infrared and the X-ray band is tightly connected to the high-energy component that peaks in the γ-rays. Two strong connections that link radio and mid-infrared emission of blazars to the emission in the γ-ray band are well established. They constitute the basis for associating γ-ray sources with their low-energy counterparts. Aims: We searched for a possible link between X-ray and γ-ray emissions for the subclass of BL Lacs using all archival Swift/XRT observations combined with Fermi data for a selected sample of 351 sources. Methods: Analyzing ̃2400 ks of Swift/XRT observations that were carried out until December 2018, we discovered that above the γ-ray flux threshold Fγ ≈ 3 × 10-12 erg cm-2 s-1, 96% of all Fermi BL Lacs have an X-ray counterpart that is detected with signal-to-noise ratio > 3. Results: We did not find any correlation or clear trend between X-ray and γ-ray fluxes and/or spectral shapes, but we discovered a correlation between the X-ray flux and the mid-infrared color. Finally, we discuss on a possible interpretation of our results in the SSC framework. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/631/A150
Optical spectroscopic observations of gamma-ray blazar candidates VIII: the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR telescopesMarchesini, E. J.Peña-Herazo, H. A.Álvarez Crespo, N.Ricci, FedericaNegro, M.Milisavljevic, D.Massaro, F.Masetti, N.Landoni, M.Chavushyan, V.D'Abrusco, RaffaeleJiménez-Bailón, E.La Franca, F.Paggi, A.Smith, Howard A.Tosti, G.DOI: info:10.1007/s10509-018-3490-zv. 3645
Marchesini, E. J., Peña-Herazo, H. A., Álvarez Crespo, N., Ricci, Federica, Negro, M., Milisavljevic, D., Massaro, F., Masetti, N., Landoni, M., Chavushyan, V., D'Abrusco, Raffaele, Jiménez-Bailón, E., La Franca, F., Paggi, A., Smith, Howard A., and Tosti, G. 2019. "Optical spectroscopic observations of gamma-ray blazar candidates VIII: the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR telescopes." Astrophysics and Space Science 364:5. https://doi.org/10.1007/s10509-018-3490-z
ID: 150415
Type: article
Authors: Marchesini, E. J.; Peña-Herazo, H. A.; Álvarez Crespo, N.; Ricci, Federica; Negro, M.; Milisavljevic, D.; Massaro, F.; Masetti, N.; Landoni, M.; Chavushyan, V.; D'Abrusco, Raffaele; Jiménez-Bailón, E.; La Franca, F.; Paggi, A.; Smith, Howard A.; Tosti, G.
Abstract: The third Fermi source catalog lists 3033 γ -ray sources above 4σ significance. More than 30% are classified as either unidentified/unassociated Gamma-ray sources (UGSs), with about 20% classified as Blazar candidates of uncertain types (BCUs). To confirm the blazar-like nature of candidate counterparts of UGSs and BCUs, we started in 2012 an optical spectroscopic follow up campaign. We report here the spectra of 36 targets with observations from the Observatorio Astronómico Nacional San Pedro Mártir, the Southern Astrophysical Research Observatory, the Kitt Peak National Observatory and the Northern Optical Telescope, between 2016 and 2017. We confirm the BL Lac nature of 23 sources, and the flat spectrum radio quasar nature of other 7 ones. We also provide redshift estimates for 19 out of these 30 confirmations, with only one being a lower limit due to spectral features ascribable to intervening systems along the line of sight. As in previous analyses, the largest fraction of now-classified BCUs belong to the class of BL Lac objects, that appear to be the most elusive class of active galactic nuclei. One of the BL Lacs identified in this work, associated with 3FGL J2213.6-4755, lies at a redshift of z>1.529, making it one of the few distant gamma-ray BL Lac objects.
WATCAT: a tale of wide-angle tailed radio galaxiesMissaglia, V.Massaro, F.Capetti, A.Paolillo, M.Kraft, Ralph P.Baldi, R. D.Paggi, A.DOI: info:10.1051/0004-6361/201935058v. 626A8
Missaglia, V., Massaro, F., Capetti, A., Paolillo, M., Kraft, Ralph P., Baldi, R. D., and Paggi, A. 2019. "WATCAT: a tale of wide-angle tailed radio galaxies." Astronomy and Astrophysics 626:A8. https://doi.org/10.1051/0004-6361/201935058
ID: 152907
Type: article
Authors: Missaglia, V.; Massaro, F.; Capetti, A.; Paolillo, M.; Kraft, Ralph P.; Baldi, R. D.; Paggi, A.
Abstract: We present a catalog of 47 wide-angle tailed radio galaxies (WATs), the WATCAT, mainly built including a radio morphological classification; WATs were selected by combining observations from the National Radio Astronomy Observatory/Very Large Array Sky Survey (NVSS), the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST), and the Sloan Digital Sky Survey (SDSS). We included in the catalog only radio sources showing two-sided jets with two clear "warmspots" (i.e., jet knots as bright as 20% of the nucleus) lying on the opposite side of the radio core, and having classical extended emission resembling a plume beyond them. The catalog is limited to redshifts z ≤ 0.15, and lists only sources with radio emission extended beyond 30 kpc from the host galaxy. We found that host galaxies of WATCAT sources are all luminous (-20.5 ≳ Mr ≳ -23.7), red early-type galaxies with black hole masses in the range 108 ≲ MBH ≲ 109 M. The spectroscopic classification indicates that they are all low-excitation galaxies (LEGs). Comparing WAT multifrequency properties with those of FR I and FR II radio galaxies at the same redshifts, we conclude that WATs show multifrequency properties remarkably similar to FR I radio galaxies, having radio power of typical FR IIs.
Optical spectroscopic observations of gamma-ray blazar candidates. IX. Optical archival spectra and further observations from SOAR and OAGHPeña-Herazo, H. A.Massaro, F.Chavushyan, V.Marchesini, E. J.Paggi, A.Landoni, M.Masetti, N.Ricci, F.D'Abrusco, RaffaeleMilisavljevic, D.Jiménez-Bailón, E.La Franca, F.Smith, Howard A.Tosti, G.DOI: info:10.1007/s10509-019-3574-4v. 36485
Peña-Herazo, H. A., Massaro, F., Chavushyan, V., Marchesini, E. J., Paggi, A., Landoni, M., Masetti, N., Ricci, F., D'Abrusco, Raffaele, Milisavljevic, D., Jiménez-Bailón, E., La Franca, F., Smith, Howard A., and Tosti, G. 2019. "Optical spectroscopic observations of gamma-ray blazar candidates. IX. Optical archival spectra and further observations from SOAR and OAGH." Astrophysics and Space Science 364:85. https://doi.org/10.1007/s10509-019-3574-4
ID: 155155
Type: article
Authors: Peña-Herazo, H. A.; Massaro, F.; Chavushyan, V.; Marchesini, E. J.; Paggi, A.; Landoni, M.; Masetti, N.; Ricci, F.; D'Abrusco, Raffaele; Milisavljevic, D.; Jiménez-Bailón, E.; La Franca, F.; Smith, Howard A.; Tosti, G.
Abstract: Nearly one third of the sources in the Fermi-LAT catalogs lacks a lower energy counterpart, hence being referred as unidentified/unassociated gamma-ray sources (UGSs). In order to firmly classify them, dedicated multifrequency follow-up campaigns are necessary. These will permit to unveil their nature and identify the fraction that could belong to the class of active galaxies known as blazars that is the largest population of extragalactic γ -ray sources. In Fermi-LAT catalogs there are also gamma-ray sources associated with multifrequency blazar-like objects known as Blazars Candidates of Uncertain type (i.e., BCUs) for which follow up spectroscopic campaigns are mandatory to confirm their blazar nature. Thus, in 2013 we started an optical spectroscopic campaign to identify blazar-like objects potential counterparts of UGSs and BCUs. Here we report the spectra of 31 additional targets observed as part of our follow up campaign. Thirteen of them are BCUs for which we acquired spectroscopic observations at Observatorio Astrofísico Guillermo Haro (OAGH) and at Southern Astrophysical Research Observatory (SOAR) telescopes, while the rest has been identified thanks to the archival observations available from the Sloan Digital Sky Survey (SDSS). We confirm the blazar nature of all BCUs: three of them are in blazar of quasar type (BZQs) while the remaining ones can be spectroscopically classified as BL Lac objects (BZBs). Then we also discovered 18 BL Lac objects lying within the positional uncertainty regions of UGSs that could be their potential counterparts.