Compton-thick AGNs in the NuSTAR Era Marchesi, S.; Ajello, M.; Marcotulli, L. ...
The Astrophysical journal,
02/2018, Letnik:
854, Številka:
1
Journal Article
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We present the 2-100 keV spectral analysis of 30 candidate Compton-thick-(CT-)active galactic nuclei (AGNs) selected in the Swift-Burst Alert Telescope (BAT) 100 month survey. The average redshift of ...these objects is , and they all lie within ∼500 Mpc. We used the MyTorus model to perform X-ray spectral fittings both without and with the contribution of the Nuclear Spectroscopic Telescope Array (NuSTAR) data in the 3-50 keV energy range. When the NuSTAR data are added to the fit, 13 out of 30 of these objects (43% of the whole sample) have intrinsic absorption NH < 1024 cm−2 at the >3 confidence level, i.e., they are reclassified from Compton thick to Compton thin. Consequently, we infer an overall observed fraction of the CT-AGN, with respect to the whole AGN population, lower than the one reported in previous works, as low as ∼4%. We find evidence that this overestimation of NH is likely due to the low quality of a subsample of spectra, either in the 2-10 keV band or in the Swift-BAT one.
A majority of the γ-ray emission from star-forming galaxies is generated by the interaction of high-energy cosmic rays with the interstellar gas and radiation fields. Star-forming galaxies are ...expected to contribute to both the extragalactic γ-ray background and the IceCube astrophysical neutrino flux. Using roughly 10 yr of γ-ray data taken by the Fermi Large Area Telescope, in this study we constrain the γ-ray properties of star-forming galaxies. We report the detection of 11 bona fide γ-ray-emitting galaxies and 2 candidates. Moreover, we show that the cumulative γ-ray emission of below-threshold galaxies is also significantly detected at ∼5 confidence. The γ-ray luminosity of resolved and unresolved galaxies is found to correlate with the total (8-1000 m) infrared luminosity as previously determined. Above 1 GeV, the spectral energy distribution of resolved and unresolved galaxies is found to be compatible with a power law with a photon index of 2.2-2.3. Finally, we find that star-forming galaxies account for roughly 5% and 3% of the extragalactic γ-ray background and the IceCube neutrino flux, respectively.
The Central Engines of Fermi Blazars Paliya, Vaidehi S.; Domínguez, A.; Ajello, M. ...
The Astrophysical journal. Supplement series,
04/2021, Letnik:
253, Številka:
2
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Abstract
We present a catalog of central engine properties, i.e., black hole mass (
M
BH
) and accretion luminosity (
L
disk
), for a sample of 1077 blazars detected with the Fermi Large Area ...Telescope. This includes broad emission-line systems and blazars whose optical spectra lack emission lines but are dominated by the absorption features arising from the host galaxy. The average
M
BH
for the sample is
, and there is evidence suggesting the association of more massive black holes with absorption-line systems. Our results indicate a bimodality of
L
disk
in Eddington units (
L
disk
/
L
Edd
) with broad-line objects tend to have a higher accretion rate (
L
disk
/
L
Edd
> 0.01). We have found that
L
disk
/
L
Edd
and Compton dominance (CD; the ratio of the inverse Compton to synchrotron peak luminosities) are positively correlated at the >5
σ
confidence level, suggesting that the latter can be used to reveal the state of accretion in blazars. Based on this result, we propose a CD-based classification scheme. Sources with CD > 1 can be classified as high-Compton-dominated or HCD blazars, whereas those with CD ≲ 1 are low-Compton-dominated (LCD) objects. This scheme is analogous to that based on the mass accretion rate proposed in the literature; however, it overcomes the limitation imposed by the difficulty in measuring
L
disk
and
M
BH
for objects with quasi-featureless spectra. We conclude that the overall physical properties of Fermi blazars are likely to be controlled by the accretion rate in Eddington units. The catalog is made public at
http://www.ucm.es/blazars/engines
and Zenodo.
We present the results of a multi-frequency, time-averaged analysis of blazars included in the Candidate Gamma-ray Blazar Survey catalog. Our sample consists of 324 γ-ray detected (γ-ray loud) and ...191 γ-ray undetected (γ-ray quiet) blazars; we consider all the data up to 2016 April 1. We find that both the γ-ray loud and γ-ray quiet blazar populations occupy similar regions in the WISE color-color diagram, and γ-ray loud sources are brighter in the radio and X-ray bands. A simple one-zone synchrotron inverse-Compton emission model is applied to derive the physical properties of both populations. We find that the central black hole mass and accretion disk luminosity ( L disk ) computed from the modeling of the optical-UV emission with a Shakura-Sunyaev disk reasonably matches that estimated from the optical spectroscopic emission-line information. A significantly larger Doppler boosting in the γ-ray loud blazars is noted, and their jets are more radiatively efficient. On the other hand, the γ-ray quiet objects are more MeV-peaked and thus could be potential targets for next-generation MeV missions. Our results confirm earlier findings about the accretion-jet connection in blazars; however, many of the γ-ray quiet blazars tend to deviate from the recent claim that the jet power exceeds L disk in blazars. A broadband study, considering a larger set of γ-ray quiet objects and also including BL Lacs, will be needed to confirm/reject this hypothesis as well as to verify the evolution of the powerful high-redshift blazars into their low-power nearby counterparts.
We present a 2-78 keV spectral analysis of the deep NuSTAR and XMM-Newton observation of a nearby Seyfert 2 galaxy, ESO 116-G018, which is selected as a candidate Compton-thick (CT) active galactic ...nucleus (AGN) based on a previous Chandra-Swift-BAT study. Through our analysis, the source is, for the first time, confirmed to be a CT AGN at a >3 confidence level, with the "line-of-sight" column density NH,Z = 2.46-2.76 × 1024 cm−2. The "global average" column density of the obscuring torus is NH,S = 0.46-0.62 × 1024 cm−2, which suggests a clumpy, rather than uniform, distribution of the obscuring material surrounding the accreting supermassive black hole. The excellent-quality data given by the combined NuSTAR and XMM-Newton observations enable us to produce a strong constraint on the covering factor of the torus of ESO 116-G018, which is found to be fc = 0.13-0.15. We also estimate the bolometric luminosity from the broadband X-ray spectrum to be Lbol = 2.57-3.41 × 1044 erg s−1.
With 10 years of operation and an exceptional data set, the Fermi-Large Area Telescope allows us to unveil the detailed composition of the extragalactic γ-ray sky above 100 MeV. In this paper, we ...derive the intrinsic source-count distribution (logN-logS) of extragalactic sources (i.e., blazars) at via the efficiency correction method. With this approach, we are able to measure the distribution down to a photon flux of and to an energy flux of ∼10−12 . In both cases, the logN-logS becomes flatter at low fluxes. Moreover, we show that this logN-logS is representative of the blazar population (assuming the majority of unassociated sources are blazars) and allows us to constrain its evolution quite effectively. Among recently proposed evolutionary models, we find that the Pure Density Evolution model best describes the evolutionary properties of the blazar population and that their integrated emission accounts for of the total extragalactic γ-ray background.
We characterize the environments of local accreting supermassive black holes by measuring the clustering of AGNs in the Swift/BAT Spectroscopic Survey (BASS). With 548 AGN in the redshift range 0.01 ...< z < 0.1 over the full sky from the DR1 catalog, BASS provides the largest, least biased sample of local AGNs to date due to its hard X-ray selection (14-195 keV) and rich multiwavelength/ancillary data. By measuring the projected cross-correlation function between the AGN and 2MASS galaxies, and interpreting it via halo occupation distribution and subhalo-based models, we constrain the occupation statistics of the full sample, as well as in bins of absorbing column density and black hole mass. We find that AGNs tend to reside in galaxy group environments, in agreement with previous studies of AGNs throughout a large range of luminosity and redshift, and that on average they occupy their dark matter halos similar to inactive galaxies of comparable stellar mass. We also find evidence that obscured AGNs tend to reside in denser environments than unobscured AGNs, even when samples were matched in luminosity, redshift, stellar mass, and Eddington ratio. We show that this can be explained either by significantly different halo occupation distributions or statistically different host halo assembly histories. Lastly, we see that massive black holes are slightly more likely to reside in central galaxies than black holes of smaller mass.
Abstract Active galactic nuclei (AGNs) can power relativistic jets, which are called blazars when pointed close to our line of sight. Depending on the presence or absence of emission lines in their ...optical spectra, blazars are categorized into flat spectrum radio quasars (FSRQs) or BL Lacertae (BL Lac) objects. According to the “blazar sequence,” as synchrotron peak frequency ( ν pk sy ) shifts to higher energies, the synchrotron peak luminosity decreases. This means that BL Lac objects as luminous as FSRQs, and with synchrotron peak frequencies ν pk sy > 10 15 Hz, should not exist. Detected as a high-synchrotron peak (HSP; ν pk sy > 10 15 Hz) BL Lac object, 4FGL J1520.8-0348 shows high γ -ray luminosity ( L γ > 10 46 erg s −1 ), being at a high redshift of z = 1.46. Since it is an outlier in the “blazar sequence,” the process of its jet acceleration and power may be different from bona fide BL Lac objects. In this work, we constrain its spectral energy distribution (SED) by modeling the multiwavelength data from infrared to γ -ray regime. Simultaneous X-ray data were obtained from X-ray Multi-Mirror Mission and Nuclear Spectroscopic Telescope Array to constrain the synchrotron emission and underlying electron distribution. On undertaking the SED modeling of the source, including the effect of extragalactic background light, we conclude that the source is more likely to be a “blue FSRQ” or “masquerading BL Lac” where the BL Lac object is actually an FSRQ in disguise.
The extragalactic background light (EBL) can be probed via the absorption imprint it leaves in the spectra of gamma-ray sources ( ). We recently developed a dedicated technique to reconstruct the ...EBL, and its evolution with redshift, from γ-ray optical depth data using a large sample of blazars detected by the Fermi Large Area Telescope. Here, we extend this data set to the TeV regime using ground-based Cherenkov observations of 38 blazars and report the first homogeneous measurement of the EBL spectral intensity covering the ultraviolet to infrared wavelengths (∼0.1-100 m). A minimal EBL throughout the wavelength range with respect to integrated galaxy light is found, allowing little additional unresolved emission from faint or truly diffuse populations setting an upper limit of 4 nW m−2 sr−1 at 1.4 m. In particular, the cosmic optical background at z = 0 is found to be . This work lays the foundation for accurate gamma-ray measurements of the EBL across its whole spectral range using a combination of GeV and TeV data.
The detection of significant γ-ray emission from radio-loud narrow-line Seyfert 1 (NLSy1s) galaxies enables us to study jets in environments different than those in blazars. However, due to the small ...number of known γ-ray-emitting NLSy1 (γ-NLSy1) galaxies, a comprehensive study could not be performed. Here, we report the first detection of significant γ-ray emission from four active galactic nuclei (AGNs), recently classified as NLSy1 from their Sloan Digital Sky Survey (SDSS) optical spectrum. Three flat-spectrum radio quasars (FSRQs) present in the third Large Area Telescope AGN catalog (3LAC) are also found as γ-NLSy1 galaxies. Comparing the γ-ray properties of these objects with 3LAC blazars reveals their spectral shapes to be similar to FSRQs, however, with low γ-ray luminosity ( 1046-47 erg s−1). In the Wide-field Infrared Survey Explorer color-color diagram, these objects occupy a region mainly populated by FSRQs. Using the Hβ emission line parameters, we find that on average γ-NLSy1 have smaller black hole masses than FSRQs at similar redshifts. In the low-resolution SDSS image of one of the γ-NLSy1 source, we find the evidence of an extended structure. We conclude by noting that overall many observational properties of γ-NLSy1 sources are similar to FSRQs, and therefore these objects could be their low black hole mass counterparts, as predicted in the literature.
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