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Showing 1-20 of about 67 results.
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.
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.
Chandra View of the LINER-type Nucleus in the Radio-loud Galaxy CGCG 292-057: Ionized Iron Line and Jet-ISM InteractionsBalasubramaniam, K.Stawarz, L.Marchenko, V.Sobolewska, Magorzata A.Cheung, C. C.Siemiginowska, AnetaThimmappa, R.Kosmaczewski, E.DOI: info:10.3847/1538-4357/abc4e2v. 905148
Balasubramaniam, K., Stawarz, L., Marchenko, V., Sobolewska, Magorzata A., Cheung, C. C., Siemiginowska, Aneta, Thimmappa, R., and Kosmaczewski, E. 2020. "Chandra View of the LINER-type Nucleus in the Radio-loud Galaxy CGCG 292-057: Ionized Iron Line and Jet-ISM Interactions." The Astrophysical Journal 905:148.
ID: 158661
Type: article
Authors: Balasubramaniam, K.; Stawarz, L.; Marchenko, V.; Sobolewska, Magorzata A.; Cheung, C. C.; Siemiginowska, Aneta; Thimmappa, R.; Kosmaczewski, E.
Abstract: We present an analysis of the new, deep (94 ksec) Chandra ACIS-S observation of radio-loud active galaxy CGCG 292-057, characterized by a LINER-type nucleus and a complex radio structure that indicates intermittent jet activity. On the scale of the host galaxy bulge, we detected excess X-ray emission with a spectrum best fit by a thermal plasma model with a temperature of ˜0.8 keV. We argue that this excess emission results from compression and heating of the hot diffuse fraction of the interstellar medium displaced by the expanding inner, ˜20 kpc-scale lobes observed in this restarted radio galaxy. The nuclear X-ray spectrum of the target clearly displays an ionized iron line at ˜6.7 keV, and is best fitted with a phenomenological model consisting of a power-law (photon index ? 1.8) continuum absorbed by a relatively large amount of cold matter (hydrogen column density ?0.7 × 1023 cm-2), and partly scattered (fraction ˜3%) by ionized gas, giving rise to a soft excess component and Ka line from iron ions. We demonstrate that the observed X-ray spectrum, particularly the equivalent width of Fe XXV Ka (of order 0.3 keV) can in principle, be explained in a scenario involving a Compton-thin gas located at the scale of the broad-lined region in this source and photoionized by nuclear illumination. We compare the general spectral properties of the CGCG 292-057 nucleus, with those of other nearby LINERs studied in X-rays.
Powerful ionized gas outflows in the interacting radio galaxy 4C+29.30Couto, Guilherme S.Storchi-Bergmann, ThaisaSiemiginowska, AnetaRiffel, Rogemar A.Morganti, RaffaellaDOI: info:10.1093/mnras/staa2268v. 4975103–5117
Couto, Guilherme S., Storchi-Bergmann, Thaisa, Siemiginowska, Aneta, Riffel, Rogemar A., and Morganti, Raffaella. 2020. "Powerful ionized gas outflows in the interacting radio galaxy 4C+29.30." Monthly Notices of the Royal Astronomical Society 497:5103– 5117.
ID: 157808
Type: article
Authors: Couto, Guilherme S.; Storchi-Bergmann, Thaisa; Siemiginowska, Aneta; Riffel, Rogemar A.; Morganti, Raffaella
Abstract: We investigate the ionized gas excitation and kinematics in the inner $4.3\, \times \, 6.2$ kpc2 of the merger radio galaxy 4C+29.30. Using optical integral field spectroscopy with the Gemini North Telescope, we present flux distributions, line-ratio maps, peak velocities and velocity dispersion maps as well as channel maps with a spatial resolution of $\approx\! 955\,$ pc. We observe high blueshifts of up to $\sim\! -650\,$$\rm km\, s^{-1}$ in a region ∼1 arcsec south of the nucleus (the southern knot - SK), which also presents high velocity dispersions ($\sim\! 250\,$$\rm km\, s^{-1}$), which we attribute to an outflow. A possible redshifted counterpart is observed north from the nucleus (the northern knot - NK). We propose that these regions correspond to a bipolar outflow possibly due to the interaction of the radio jet with the ambient gas. We estimate a total ionized gas mass outflow rate of $\dot{M}_{\mathrm{ out}} = 25.4 ^{+11.5 }_{ -7.5}\,$ M yr-1with a kinetic power of $\dot{E} = 8.1 ^{+10.7 }_{ -4.0} \times 10^{42}\,$ erg s-1, which represents $5.8 ^{+7.6 }_{ -2.9} {{\ \rm per\ cent}}$ of the active galactic nucleus (AGN) bolometric luminosity. These values are higher than usually observed in nearby active galaxies with the same bolometric luminosities and could imply a significant impact of the outflows in the evolution of the host galaxy. The excitation is higher in the NK - that correlates with extended X-ray emission, indicating the presence of hotter gas - than in the SK, supporting a scenario in which an obscuring dust lane is blocking part of the AGN radiation to reach the southern region of the galaxy.
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.
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.
Mid-infrared Diagnostics of the Circumnuclear Environments of the Youngest Radio GalaxiesKosmaczewski, E.Stawarz, Ł.Siemiginowska, AnetaCheung, C. C.Ostorero, L.Sobolewska, MalgorzataKozieł-Wierzbowska, D.Wójtowicz, A.Marchenko, V.DOI: info:10.3847/1538-4357/ab9b1fv. 897164
Kosmaczewski, E., Stawarz, Ł., Siemiginowska, Aneta, Cheung, C. C., Ostorero, L., Sobolewska, Malgorzata, Kozieł-Wierzbowska, D., Wójtowicz, A., and Marchenko, V. 2020. "Mid-infrared Diagnostics of the Circumnuclear Environments of the Youngest Radio Galaxies." The Astrophysical Journal 897:164.
ID: 157705
Type: article
Authors: Kosmaczewski, E.; Stawarz, Ł.; Siemiginowska, Aneta; Cheung, C. C.; Ostorero, L.; Sobolewska, Malgorzata; Kozieł-Wierzbowska, D.; Wójtowicz, A.; Marchenko, V.
Abstract: We present a systematic analysis of the mid-infrared (MIR) properties of the youngest radio galaxies, based on low-resolution data provided by the Wide-field Infrared Survey Explorer and IRAS satellites. We restrict our analysis to sources with available X-ray data that constitute the earliest phase of radio galaxy evolution, I.e., those classified as gigahertz-peaked spectrum and/or compact symmetric objects. In our sample of 29 objects, we find that the host galaxies are predominantly red/yellow ellipticals, with some of them displaying distorted morphology. We find a variety of MIR colors and observe that the sources in which the MIR emission is dominated by the ISM component uniformly populate the region occupied by galaxies with a wide range of pronounced (≥0.5M yr-1) star formation activity. We compare the MIR color distribution in our sample to that in the general population of local active galactic nuclei (AGNs), in the population of evolved FR II radio galaxies, and also in the population of radio galaxies with recurrent jet activity. We conclude that the triggering of radio jets in AGNs does not differentiate between elliptical hosts with substantially different fractions of young stars; instead, there is a relationship between the jet duty cycle and the ongoing star formation. The distribution of the subsample of our sources with z < 0.4 on the low-resolution MIR versus absorption-corrected X-ray luminosity plane is consistent with the distribution of a sample of local AGNs. Finally, we comment on the star formation rates of the two γ-ray-detected sources in our sample, 1146+596 and 1718-649.
TXS 0128+554: A Young Gamma-Ray-emitting Active Galactic Nucleus with Episodic Jet ActivityLister, Matthew L.Homan, Daniel C.Kovalev, Yuri Y.Mandal, S.Pushkarev, Alexander B.Siemiginowska, AnetaDOI: info:10.3847/1538-4357/aba18dv. 899141
Lister, Matthew L., Homan, Daniel C., Kovalev, Yuri Y., Mandal, S., Pushkarev, Alexander B., and Siemiginowska, Aneta. 2020. "TXS 0128+554: A Young Gamma-Ray-emitting Active Galactic Nucleus with Episodic Jet Activity." The Astrophysical Journal 899:141.
ID: 157702
Type: article
Authors: Lister, Matthew L.; Homan, Daniel C.; Kovalev, Yuri Y.; Mandal, S.; Pushkarev, Alexander B.; Siemiginowska, Aneta
Abstract: We have carried out a Chandra X-ray and multifrequency radio Very Long Baseline Array study of the active galactic nucleus (AGN) TXS 0128+554, which is associated with the Fermi γ-ray source 4FGL J0131.2+5547. The AGN is unresolved in a target 19.3 ks Chandra image, and its spectrum is well fit by a simple absorbed power-law model, with no distinguishable spectral features. Its relatively soft X-ray spectrum compared to other compact symmetric objects (CSOs) may be indicative of a thermal emission component, for which we were able to obtain an upper temperature limit of kT = 0.08 keV. The compact radio morphology and measured advance speed of 0.32 c ± 0.07 c indicate a kinematic age of only 82 yr ± 17 yr, placing TXS 0128+554 among the youngest members of the CSO class. The lack of compact, inverted spectrum hotspots and an emission gap between the bright inner jet and outer radio lobe structure indicate that the jets have undergone episodic activity, and were relaunched a decade ago. The predicted γ-ray emission from the lobes, based on an inverse Compton-emitting cocoon model, is three orders of magnitude below the observed Fermi-LAT flux. A comparison to other Fermi-detected and non-Fermi-detected CSOs with redshift z < 0.1 indicates that the γ-ray emission likely originates in the inner jet/core region, and that nearby, recently launched AGN jets are primary candidates for detection by the Fermi-LAT instrument.
Two Candidate High-redshift X-Ray Jets without Coincident Radio JetsSchwartz, Daniel A.Siemiginowska, AnetaSnios, BradfordWorrall, D. M.Birkinshaw, M.Cheung, C. C.Marshall, H.Migliori, G.Wardle, J. F. C.Gobeille, DougDOI: info:10.3847/1538-4357/abbd99v. 90457
Schwartz, Daniel A., Siemiginowska, Aneta, Snios, Bradford, Worrall, D. M., Birkinshaw, M., Cheung, C. C., Marshall, H., Migliori, G., Wardle, J. F. C., and Gobeille, Doug. 2020. "Two Candidate High-redshift X-Ray Jets without Coincident Radio Jets." The Astrophysical Journal 904:57.
ID: 158824
Type: article
Authors: Schwartz, Daniel A.; Siemiginowska, Aneta; Snios, Bradford; Worrall, D. M.; Birkinshaw, M.; Cheung, C. C.; Marshall, H.; Migliori, G.; Wardle, J. F. C.; Gobeille, Doug
Abstract: We report the detection of extended X-ray emission from two high-redshift radio quasars. These quasars, J1405+0415 at z = 3.208 and J1610+1811 at z = 3.118, were observed in a Chandra snapshot survey selected from a complete sample of the radio-brightest quasars in the overlap area of the VLA-FIRST radio survey and the Sloan Digital Sky Survey. The extended X-ray emission is located along the line connecting the core to a radio knot or hotspot, favoring the interpretation of X-ray jets. The inferred rest-frame jet X-ray luminosities from 2 to 30 keV would be of order 1045 erg s-1 if emitted isotropically and without relativistic beaming. In the scenario of inverse Compton scattering of the cosmic microwave background (CMB), X-ray jets without a coincident radio counterpart may be common, and should be readily detectable to redshifts even beyond 3.2 due to the (1+z)4 increase of the CMB energy density compensating for the (1+z)-4 cosmological diminution of surface brightness. If these can be X-ray confirmed, they would be the second and third examples of quasar X-ray jets without detection of underlying continuous radio jets.
X-Ray Properties of Young Radio Quasars at z > 4.5Snios, BradfordSiemiginowska, AnetaSobolewska, MałgosiaCheung, C. C.Kashyap, VinayMigliori, GiuliaSchwartz, Daniel A.Stawarz, ŁukaszWorrall, Diana M.DOI: info:10.3847/1538-4357/aba2cav. 899127
Snios, Bradford, Siemiginowska, Aneta, Sobolewska, Małgosia, Cheung, C. C., Kashyap, Vinay, Migliori, Giulia, Schwartz, Daniel A., Stawarz, Łukasz, and Worrall, Diana M. 2020. "X-Ray Properties of Young Radio Quasars at z > 4.5." The Astrophysical Journal 899:127.
ID: 157703
Type: article
Authors: Snios, Bradford; Siemiginowska, Aneta; Sobolewska, Małgosia; Cheung, C. C.; Kashyap, Vinay; Migliori, Giulia; Schwartz, Daniel A.; Stawarz, Łukasz; Worrall, Diana M.
Abstract: We present a comprehensive analysis of Chandra X-ray observations of 15 young radio quasars at redshifts 4.5 45 erg s-1. The optical-X-ray power-law spectral index ${\alpha }_{\mathrm{ox}}$ is calculated for each source using optical/UV data available in the literature. The ${\alpha }_{\mathrm{ox}}$ -UV relationship is compared with other quasar surveys, and an anticorrelation is observed that agrees with independent estimates. Rest-frame radio and X-ray luminosities are established for the sample, and a correlation between the luminosities is detected. These multiwavelength results reinforce a lack of spectral evolution for quasars over a broad redshift range. We additionally identify three quasars from our multiwavelength analysis that are statistically significant outliers, with one source being a Compton-thick candidate in the early universe, and discuss each in detail.
Chandra Imaging of the Western Hotspot in the Radio Galaxy Pictor A: Image Deconvolution and Variability AnalysisThimmappa, R.Stawarz, L.Marchenko, V.Balasubramaniam, K.Cheung, C. C.Siemiginowska, AnetaDOI: info:10.3847/1538-4357/abb605v. 903109
Thimmappa, R., Stawarz, L., Marchenko, V., Balasubramaniam, K., Cheung, C. C., and Siemiginowska, Aneta. 2020. "Chandra Imaging of the Western Hotspot in the Radio Galaxy Pictor A: Image Deconvolution and Variability Analysis." The Astrophysical Journal 903:109.
ID: 158819
Type: article
Authors: Thimmappa, R.; Stawarz, L.; Marchenko, V.; Balasubramaniam, K.; Cheung, C. C.; Siemiginowska, Aneta
Abstract: Here we present an analysis of the X-ray morphology and flux variability of the particularly bright and extended western hotspot in the nearest powerful (FR II-type) radio galaxy, Pictor A, based on data obtained with the Chandra X-ray Observatory. The hotspot marks the position where the relativistic jet, which originates in the active nucleus of the system, interacts with the intergalactic medium, at hundreds-of-kiloparsec distances from the host galaxy, forming a termination shock that converts jet bulk kinetic energy to internal energy of the plasma. The hotspot is bright in X-rays due to the synchrotron emission of electrons accelerated to ultrarelativistic energies at the shock front. In our analysis, we make use of several Chandra observations targeting the hotspot over the last decades with various exposures and off-axis angles. For each pointing, we study in detail the point-spread function, which allows us to perform the image deconvolution, and to resolve the hotspot structure. In particular, the brightest segment of the X-ray hotspot is observed to be extended in the direction perpendicular to the jet, forming a thin, ˜3 kpc long, feature that we identify with the front of the reverse shock. The position of this feature agrees well with the position of the optical intensity peak of the hotspot, but is clearly offset from the position of the radio intensity peak, located ˜1 kpc further downstream. In addition, we measure the net count rate on the deconvolved images, finding a gradual flux decrease by about 30% over the 15 yr timescale of the monitoring.
On the Jet Production Efficiency in a Sample of the Youngest Radio GalaxiesWójtowicz, A.Stawarz, Ł.Cheung, C. C.Ostorero, L.Kosmaczewski, E.Siemiginowska, AnetaDOI: info:10.3847/1538-4357/ab7930v. 892116
Wójtowicz, A., Stawarz, Ł., Cheung, C. C., Ostorero, L., Kosmaczewski, E., and Siemiginowska, Aneta. 2020. "On the Jet Production Efficiency in a Sample of the Youngest Radio Galaxies." The Astrophysical Journal 892:116.
ID: 157293
Type: article
Authors: Wójtowicz, A.; Stawarz, Ł.; Cheung, C. C.; Ostorero, L.; Kosmaczewski, E.; Siemiginowska, Aneta
Abstract: Here we discuss the jet production efficiency in a sample of 17 young radio galaxies with measured redshifts, kinematic ages, and nuclear X-ray fluxes, for which the observed luminosities of compact jets/lobes and accretion disks correspond to the same episode of AGN activity. For the targets, we analyze the available optical data, estimating the bolometric luminosities of the accretion disks Lbol, and the black hole masses; we also derive the minimum jet kinetic luminosities, Pj. With this information we investigate the distribution of our sample in the three-dimensional space of the accretion rate λEdd &Congruent Lbol/LEdd, the nuclear X-ray luminosity LX considered here as a limit for the emission of the disk coronae, and Pj, expressing the latter two parameters either in the Eddington units, or in the units of the disk luminosity. We find that (I) the accretion rate λEdd in our sample is distributed within a narrow range λEdd ∼ 0.01-0.2; (II) the normalized jet power Pj/LEdd formally correlates with the accretion rate λEdd, with some saturation at the largest values λEdd > 0.05; (III) the jet production efficiency ηjet ≡ Pj/\dot{M}acc c2 spans a range from ηjet ≲ 10-3 up to ∼0.2 at maximum, which is below the level expected for magnetically arrested disks around maximally spinning black holes; and (IV) there is a diversification in ηjet on the hardness-intensity diagram LX/Lbol - λEdd, with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.
Inverse-Compton scattering in the resolved jet of the high-redshift quasar PKS J1421-0643Worrall, D. M.Birkinshaw, M.Marshall, H. L.Schwartz, Daniel A.Siemiginowska, AnetaWardle, J. F. C.DOI: info:10.1093/mnras/staa1975v. 497988–1000
Worrall, D. M., Birkinshaw, M., Marshall, H. L., Schwartz, Daniel A., Siemiginowska, Aneta, and Wardle, J. F. C. 2020. "Inverse-Compton scattering in the resolved jet of the high-redshift quasar PKS J1421-0643." Monthly Notices of the Royal Astronomical Society 497:988– 1000.
ID: 157704
Type: article
Authors: Worrall, D. M.; Birkinshaw, M.; Marshall, H. L.; Schwartz, Daniel A.; Siemiginowska, Aneta; Wardle, J. F. C.
Abstract: Despite the fact that kpc-scale inverse-Compton (iC) scattering of cosmic microwave background (CMB) photons into the X-ray band is mandated, proof of detection in resolved quasar jets is often insecure. High redshift provides favourable conditions due to the increased energy density of the CMB, and it allows constraints to be placed on the radio synchrotron-emitting electron component at high energies that are otherwise inaccessible. We present new X-ray, optical, and radio results from Chandra, HST, and the VLA for the core and resolved jet in the z = 3.69 quasar PKS J1421-0643. The X-ray jet extends for about 4.5 arcsec (32 kpc projected length). The jet's radio spectrum is abnormally steep and consistent with electrons being accelerated to a maximum Lorentz factor of about 5000. Results argue in favour of the detection of iC X-rays for modest magnetic field strength of a few nT, Doppler factor of about 4, and viewing angle of about 15°, and predict the jet to be largely invisible in most other spectral bands including the far- and mid-infrared and high-energy gamma-ray. The jet power is estimated to be about 3 × 1046 erg s-1 which is of order a tenth of the quasar bolometric power, for an electron-positron jet. The jet radiative power is only about 0.07 per cent of the jet power, with a smaller radiated power ratio if the jet contains heavy particles, so most of the jet power is available for heating the intergalactic medium.
Evidence for a TDE origin of the radio transient Cygnus A-2de Vries, M. N.Wise, M. W.Nulsen, Paul E. J.Siemiginowska, AnetaRowlinson, A.Reynolds, C. S.DOI: info:10.1093/mnras/stz1078v. 4863388–3401
de Vries, M. N., Wise, M. W., Nulsen, Paul E. J., Siemiginowska, Aneta, Rowlinson, A., and Reynolds, C. S. 2019. "Evidence for a TDE origin of the radio transient Cygnus A-2." Monthly Notices of the Royal Astronomical Society 486:3388– 3401.
ID: 154171
Type: article
Authors: de Vries, M. N.; Wise, M. W.; Nulsen, Paul E. J.; Siemiginowska, Aneta; Rowlinson, A.; Reynolds, C. S.
Abstract: In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with the Very Large Array. Because of its radio brightness (νFν ≈ 6 × 1039 erg s-1), this transient likely represents a secondary black hole in orbit around the active galactic nucleus. Using Chandra ACIS observations from 2015 to 2017, we have looked for an X-ray counterpart to Cygnus A-2. The separation of 0.42 arcsec means that Cygnus A-2 cannot be spatially resolved, but by comparing the data with simulated MARX data, we put an upper limit to the 2-10 keV X-ray luminosity of Cygnus A-2 of 1 × 1043 erg s-1. Using the Fundamental Plane for accreting black holes, we find that our upper limit to the X-ray flux of Cygnus A-2 in 2015-2017 disfavours the interpretation of Cygnus A-2 as a steadily accreting black hole. We suggest instead that Cygnus A-2 is the radio afterglow of a tidal disruption event (TDE) and that a peak in the 2-10 keV luminosity of the nuclear region in 2013, when it was observed by Swift and NuSTAR, is X-ray emission from the TDE. A TDE could naturally explain the X-ray light curve of the nuclear region, as well as the appearance of a short-lived, fast, and ionized outflow previously detected in the 2013 NuSTAR spectrum. Both the radio and X-ray luminosities fall in between typical luminosities for `thermal' and `jetted' TDE types, suggesting that Cygnus A-2 would be unlike previously seen TDEs.
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.
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.
Characteristic Variability Timescales in the Gamma-Ray Power Spectra of BlazarsRyan, J. L.Siemiginowska, AnetaSobolewska, Magorzata A.Grindlay, JonathanDOI: info:10.3847/1538-4357/ab426av. 88512
Ryan, J. L., Siemiginowska, Aneta, Sobolewska, Magorzata A., and Grindlay, Jonathan. 2019. "Characteristic Variability Timescales in the Gamma-Ray Power Spectra of Blazars." The Astrophysical Journal 885:12.
ID: 154566
Type: article
Authors: Ryan, J. L.; Siemiginowska, Aneta; Sobolewska, Magorzata A.; Grindlay, Jonathan
Abstract: Characteristic variability timescales in blazar γ-ray light curves can provide insights into the physical processes responsible for γ-ray variability. The power spectral density (PSD) is capable of revealing such timescales, which may appear as breaks or periodicities. Continuous-time autoregressive moving-average (CARMA) models can be used to accurately estimate a light curve's PSD. Through a light-curve simulation study, we develop a methodology to identify PSD breaks using CARMA models. Using this methodology, we study the γ-ray light curves of 13 bright blazars observed with the Fermi Large Area Telescope in the 0.1-300 GeV band over 9.5 yr. We present the blazar γ-ray PSDs, which provide evidence for low-frequency breaks on timescales ̃1 yr in four sources, and an additional high-frequency break on a timescale ̃9 days in one source.
First Hard X-Ray Observation of a Compact Symmetric Object: A Broadband X-Ray Study of a Radio Galaxy OQ+208 with NuSTAR and ChandraSobolewska, MałgosiaSiemiginowska, AnetaGuainazzi, MatteoHardcastle, MartinMigliori, GiuliaOstorero, LuisaStawarz, ŁukaszDOI: info:10.3847/1538-4357/ab3ec3v. 884166
Sobolewska, Małgosia, Siemiginowska, Aneta, Guainazzi, Matteo, Hardcastle, Martin, Migliori, Giulia, Ostorero, Luisa, and Stawarz, Łukasz. 2019. "First Hard X-Ray Observation of a Compact Symmetric Object: A Broadband X-Ray Study of a Radio Galaxy OQ+208 with NuSTAR and Chandra." The Astrophysical Journal 884:166.
ID: 154719
Type: article
Authors: Sobolewska, Małgosia; Siemiginowska, Aneta; Guainazzi, Matteo; Hardcastle, Martin; Migliori, Giulia; Ostorero, Luisa; Stawarz, Łukasz
Abstract: Compact symmetric objects (CSOs) have been observed with Chandra and XMM-Newton to gain insights into the initial stages of a radio source evolution and to probe the black hole activity at the time of relativistic outflow formation. However, there have been no CSO observations to date at the hard X-ray energies (>10 keV), impeding our ability to robustly constrain the properties of the intrinsic X-ray emission and of the medium surrounding the young expanding jets. We present the first hard X-ray observation of a CSO performed with the Nuclear Spectroscopic Telescope Array (NuSTAR). Our target, OQ +208, is detected up to 30 keV, and thus we establish CSOs as a new class of the NuSTAR sources. We analyze the NuSTAR data jointly with our new Chandra and archival XMM-Newton data and find that a young (̃250 yr old) radio jet spanning the length of 10 pc coexists with cold obscuring matter, consistent with a dusty torus, with an equivalent hydrogen column density of N H = 1023-1024 cm-2. The primary X-ray emission is characterized by a photon index of Γ ̃ 1.45 and an intrinsic 0.5-30 keV luminosity of L ≃ 1043 erg s-1. The results of our spectral modeling and broad-line optical classification of the source suggest a porous structure of the obscuring torus. Alternatively, the source may belong to the class of optically unobscured/X-ray-obscured active galactic nucleus. The observed X-ray emission is too weak compared to that predicted by the expanding radio lobes model, leaving an accretion disk corona or jets as the possible origins of the X-ray emission from this young radio galaxy.
The Impact of the Environment on the Early Stages of Radio Source EvolutionSobolewska, MałgosiaSiemiginowska, AnetaGuainazzi, MatteoHardcastle, MartinMigliori, GiuliaOstorero, LuisaStawarz, ŁukaszDOI: info:10.3847/1538-4357/aaee78v. 87171
Sobolewska, Małgosia, Siemiginowska, Aneta, Guainazzi, Matteo, Hardcastle, Martin, Migliori, Giulia, Ostorero, Luisa, and Stawarz, Łukasz. 2019. "The Impact of the Environment on the Early Stages of Radio Source Evolution." The Astrophysical Journal 871:71.
ID: 150434
Type: article
Authors: Sobolewska, Małgosia; Siemiginowska, Aneta; Guainazzi, Matteo; Hardcastle, Martin; Migliori, Giulia; Ostorero, Luisa; Stawarz, Łukasz
Abstract: Compact symmetric objects (CSOs) show radio features such as jets, lobes, and hot spots that are contained within the central 1 kpc region of their host galaxy. Thus, they are thought to be among the progenitors of large-scale radio galaxies. A debate regarding whether the CSOs are compact primarily because they are young or because they are surrounded by a dense medium impacting their expansion is ongoing. Until now, attempts to discriminate between the environmental and genuine youthfulness scenarios have been inconclusive. We present a study of three CSOs selected on the basis of their puzzling X-ray absorbing properties in prior Beppo-SAX and/or Chandra X-ray Observatory data. Our new XMM-Newton observations unambiguously confirm the nature of their X-ray absorbers. Furthermore, for the first time, our X-ray data reveal the existence of a population of CSOs with intrinsic hydrogen column density N H > 1023 cm‑2 that is different from the population of X-ray unabsorbed CSOs. The two groups appear to be separated in the linear size versus radio power plane. This finding suggests that a dense medium in X-ray obscured CSOs may be able to confine the radio jets. Alternatively, X-ray obscured CSOs could be seen as radio brighter than their unobscured counterparts either because they reside in a dense environment or because they have larger jet powers. Our results help constrain the origin of the X-ray emission and the location and size of the X-ray obscurer in CSOs, and indicate that the environment may play a key role during the initial expansion of a radio source.
Faint γ-ray sources at low redshift: the radio galaxy IC 1531Bassi, T.Migliori, G.Grandi, P.Vignali, C.Pérez-Torres, M. A.Baldi, R. D.Torresi, E.Siemiginowska, AnetaStanghellini, C.DOI: info:10.1093/mnras/sty2622v. 4815236–5246
Bassi, T., Migliori, G., Grandi, P., Vignali, C., Pérez-Torres, M. A., Baldi, R. D., Torresi, E., Siemiginowska, Aneta, and Stanghellini, C. 2018. "Faint γ-ray sources at low redshift: the radio galaxy IC 1531." Monthly Notices of the Royal Astronomical Society 481:5236– 5246.
ID: 150173
Type: article
Authors: Bassi, T.; Migliori, G.; Grandi, P.; Vignali, C.; Pérez-Torres, M. A.; Baldi, R. D.; Torresi, E.; Siemiginowska, Aneta; Stanghellini, C.
Abstract: We present a multiwavelength study of IC 1531 (z = 0.02564), an extragalactic radio source associated with the γ-ray object 3FGL J0009.9 - 3206 and classified as a blazar of uncertain type in the Third Fermi-Large Area Telescope AGN catalog (3LAC). A core-jet structure, visible in radio and X-rays, is enclosed within a ˜220 kpc wide radio structure. The morphology and spectral characteristics of the kiloparsec jet in radio and X-rays are typical of Fanaroff-Riley type I galaxies. The analysis of the radio data and optical spectrum and different diagnostic methods based on the optical, infrared, and γ-ray luminosities also support a classification as a low-power RG seen at moderate angles (θ = 10°-20°). In the framework of leptonic models, the high-energy peak of the non-thermal nuclear spectral energy distribution can be explained in terms of synchrotron-self-Compton emission from a jet seen at θ ˜ 15°. Similarly to other misaligned AGNs detected by Fermi, the required bulk motion is lower (Γbulk = 4) than the values inferred in BL Lac objects, confirming that, because of the de-boosting of emission from the highly relativistic blazar region, these nearby systems are valuable targets to probe the existence of multiple sites of production of the most energetic emission in the jets.
Chandra Detection of the Circumnuclear Molecular Torus of the Compton-thick Active Galactic Nucleus in NGC 5643Fabbiano, GiuseppinaPaggi, AlessandroSiemiginowska, AnetaElvis, MartinDOI: info:10.3847/2041-8213/aaf73ev. 869L36
Fabbiano, Giuseppina, Paggi, Alessandro, Siemiginowska, Aneta, and Elvis, Martin. 2018. "Chandra Detection of the Circumnuclear Molecular Torus of the Compton-thick Active Galactic Nucleus in NGC 5643." Astrophysical Journal Letters 869:L36.
ID: 150189
Type: article
Authors: Fabbiano, Giuseppina; Paggi, Alessandro; Siemiginowska, Aneta; Elvis, Martin
Abstract: We report a clumpy elongated feature found with deep Chandra Advanced CCD Imaging Spectrometer high-resolution imaging of the Fe Kα line emission in the nuclear region of the Compton-thick active galactic nucleus galaxy NGC 5643. This feature extends for ˜65 pc north to south (N-S). No corresponding feature is seen in the 3.0–6.0 keV continuum. The Fe Kα feature is spatially consistent with the N-S elongation found in the CO(2–1) high-resolution imaging with the Atacama Large Millimeter/submillimeter Array, but slightly more extended than the rotating molecular disk of diameter 26 pc indicated by the kinematics of the CO(2–1) line. The Chandra detection of a corresponding north to south structure in the neutral Fe Kα line would argue for both CO and Fe Kα emission originating from the obscuring torus.
Stochastic Modeling of Multiwavelength Variability of the Classical BL Lac Object OJ 287 on Timescales Ranging from Decades to HoursGoyal, A.Stawarz, L.Zola, S.Marchenko, V.Soida, M.Nilsson, K.Ciprini, S.Baran, A.Ostrowski, M.Wiita, P. J.Gopal-KrishnaSiemiginowska, AnetaSobolewska, M.Jorstad, S.Marscher, A.Aller, M. F.Aller, H. D.Hovatta, T.Caton, D. B.Reichart, D.Matsumoto, K.Sadakane, K.Gazeas, K.Kidger, M.Piirola, V.Jermak, H.Alicavus, F.Baliyan, K. S.Baransky, A.Berdyugin, A.Blay, P.Boumis, P.Boyd, D.Bufan, Y.Campas Torrent, M.Campos, F.Carrillo Gómez, J.Dalessio, J.Debski, B.Dimitrov, D.Drozdz, M.Er, H.Erdem, A.Escartin Pérez, A.Fallah Ramazani, V.Filippenko, A. V.Gafton, E.Garcia, F.Godunova, V.Gómez Pinilla, F.Gopinathan, M.Haislip, J. B.Haque, S.Harmanen, J.Hudec, R.Hurst, G.Ivarsen, K. M.Joshi, A.Kagitani, M.Karaman, N.Karjalainen, R.Kaur, N.Koziel-Wierzbowska, D.Kuligowska, E.Kundera, T.Kurowski, S.Kvammen, A.LaCluyze, A. P.Lee, B. C.Liakos, A.Lozano de Haro, J.Moore, J. P.Mugrauer, M.Naves Nogues, R.Neely, A. W.Ogloza, W.Okano, S.Pajdosz, U.Pandey, J. C.Perri, M.Poyner, G.Provencal, J.Pursimo, T.Raj, A.Rajkumar, B.Reinthal, R.Reynolds, T.Saario, J.Sadegi, S.Sakanoi, T.Salto González, J. L.SameerSimon, A. O.Siwak, M.Schweyer, T.Soldán Alfaro, F. C.Sonbas, E.Strobl, J.Takalo, L. O.Tremosa Espasa, L.Valdes, J. R.Vasylenko, V. V.Verrecchia, F.Webb, J. R.Yoneda, M.Zejmo, M.Zheng, W.Zielinski, P.Janik, J.Chavushyan, V.Mohammed, I.Cheung, C. C.Giroletti, M.DOI: info:10.3847/1538-4357/aad2dev. 863175
Goyal, A., Stawarz, L., Zola, S., Marchenko, V., Soida, M., Nilsson, K., Ciprini, S., Baran, A., Ostrowski, M., Wiita, P. J., Gopal-Krishna, Siemiginowska, Aneta, Sobolewska, M., Jorstad, S., Marscher, A., Aller, M. F., Aller, H. D., Hovatta, T., Caton, D. B., Reichart, D., Matsumoto, K., Sadakane, K., Gazeas, K., Kidger, M., Piirola, V. et al. 2018. "Stochastic Modeling of Multiwavelength Variability of the Classical BL Lac Object OJ 287 on Timescales Ranging from Decades to Hours." The Astrophysical Journal 863:175.
ID: 148985
Type: article
Authors: Goyal, A.; Stawarz, L.; Zola, S.; Marchenko, V.; Soida, M.; Nilsson, K.; Ciprini, S.; Baran, A.; Ostrowski, M.; Wiita, P. J.; Gopal-Krishna; Siemiginowska, Aneta; Sobolewska, M.; Jorstad, S.; Marscher, A.; Aller, M. F.; Aller, H. D.; Hovatta, T.; Caton, D. B.; Reichart, D.; Matsumoto, K.; Sadakane, K.; Gazeas, K.; Kidger, M.; Piirola, V.; Jermak, H.; Alicavus, F.; Baliyan, K. S.; Baransky, A.; Berdyugin, A.; Blay, P.; Boumis, P.; Boyd, D.; Bufan, Y.; Campas Torrent, M.; Campos, F.; Carrillo Gómez, J.; Dalessio, J.; Debski, B.; Dimitrov, D.; Drozdz, M.; Er, H.; Erdem, A.; Escartin Pérez, A.; Fallah Ramazani, V.; Filippenko, A. V.; Gafton, E.; Garcia, F.; Godunova, V.; Gómez Pinilla, F.; Gopinathan, M.; Haislip, J. B.; Haque, S.; Harmanen, J.; Hudec, R.; Hurst, G.; Ivarsen, K. M.; Joshi, A.; Kagitani, M.; Karaman, N.; Karjalainen, R.; Kaur, N.; Koziel-Wierzbowska, D.; Kuligowska, E.; Kundera, T.; Kurowski, S.; Kvammen, A.; LaCluyze, A. P.; Lee, B. C.; Liakos, A.; Lozano de Haro, J.; Moore, J. P.; Mugrauer, M.; Naves Nogues, R.; Neely, A. W.; Ogloza, W.; Okano, S.; Pajdosz, U.; Pandey, J. C.; Perri, M.; Poyner, G.; Provencal, J.; Pursimo, T.; Raj, A.; Rajkumar, B.; Reinthal, R.; Reynolds, T.; Saario, J.; Sadegi, S.; Sakanoi, T.; Salto González, J. L.; Sameer; Simon, A. O.; Siwak, M.; Schweyer, T.; Soldán Alfaro, F. C.; Sonbas, E.; Strobl, J.; Takalo, L. O.; Tremosa Espasa, L.; Valdes, J. R.; Vasylenko, V. V.; Verrecchia, F.; Webb, J. R.; Yoneda, M.; Zejmo, M.; Zheng, W.; Zielinski, P.; Janik, J.; Chavushyan, V.; Mohammed, I.; Cheung, C. C.; Giroletti, M.
Abstract: We present the results of our power spectral density analysis for the BL Lac object OJ 287, utilizing the Fermi-LAT survey at high-energy gamma-rays, Swift-XRT in X-rays, several ground-based telescopes and the Kepler satellite in the optical, and radio telescopes at GHz frequencies. The light curves are modeled in terms of continuous-time autoregressive moving average (CARMA) processes. Owing to the inclusion of the Kepler data, we were able to construct for the first time the optical variability power spectrum of a blazar without any gaps across ~6 dex in temporal frequencies. Our analysis reveals that the radio power spectra are of a colored-noise type on timescales ranging from tens of years down to months, with no evidence for breaks or other spectral features. The overall optical power spectrum is also consistent with a colored noise on the variability timescales ranging from 117 years down to hours, with no hints of any quasi-periodic oscillations. The X-ray power spectrum resembles the radio and optical power spectra on the analogous timescales ranging from tens of years down to months. Finally, the gamma-ray power spectrum is noticeably different from the radio, optical, and X-ray power spectra of the source: we have detected a characteristic relaxation timescale in the Fermi-LAT data, corresponding to ~150 days, such that on timescales longer than this, the power spectrum is consistent with uncorrelated (white) noise, while on shorter variability timescales there is correlated (colored) noise.
A Multi-band Study of the Remarkable Jet in Quasar 4C+19.44Harris, D. E.Lee, N. P.Schwartz, D. A.Siemiginowska, AnetaMassaro, F.Birkinshaw, M.Worrall, D. M.Cheung, C. C.Gelbord, J. M.Jorstad, Svetlana G.Marscher, Alan P.Landt, H.Marshall, H.Perlman, E. S.Stawarz, L.Uchiyama, Y.Urry, C. M.DOI: info:10.3847/1538-4357/aa845cv. 846119
Harris, D. E., Lee, N. P., Schwartz, D. A., Siemiginowska, Aneta, Massaro, F., Birkinshaw, M., Worrall, D. M., Cheung, C. C., Gelbord, J. M., Jorstad, Svetlana G., Marscher, Alan P., Landt, H., Marshall, H., Perlman, E. S., Stawarz, L., Uchiyama, Y., and Urry, C. M. 2017. "A Multi-band Study of the Remarkable Jet in Quasar 4C+19.44." The Astrophysical Journal 846:119.
ID: 144715
Type: article
Authors: Harris, D. E.; Lee, N. P.; Schwartz, D. A.; Siemiginowska, Aneta; Massaro, F.; Birkinshaw, M.; Worrall, D. M.; Cheung, C. C.; Gelbord, J. M.; Jorstad, Svetlana G.; Marscher, Alan P.; Landt, H.; Marshall, H.; Perlman, E. S.; Stawarz, L.; Uchiyama, Y.; Urry, C. M.
Abstract: We present arcsecond-resolution data in the radio, IR, optical, and X-ray for 4C+19.44 (=PKS 1354+195), the longest and straightest quasar jet with deep X-ray observations. We report results from radio images with half to one arcsecond angular resolution at three frequencies, plus Hubble Space Telescope and Spitzer data. The Chandra data allow us to measure the X-ray spectral index in 10 distinct regions along the 18″ jet and compare with the radio index. The radio and X-ray spectral indices of the jet regions are consistent with a value of α =0.80 throughout the jet, to within 2σ uncertainties. The X-ray jet structure to the south extends beyond the prominent radio jet and connects to the southern radio lobe, and there is extended X-ray emission, both in the direction of the unseen counter-jet, and also coincident with the northern radio lobe. This jet is remarkable because its straight appearance over a large distance allows the geometry factors to be taken as fixed along the jet. Using the model of inverse Compton scattering of the cosmic microwave background (iC/CMB) by relativistic electrons, we find that the magnetic field strengths and Doppler factors are relatively constant along the jet. If instead the X-rays are synchrotron emission, they must arise from a population of electrons distinct from the particles producing the radio synchrotron spectrum.