arXiv subjects

F. Panessa

Publications and source records attributed to F. Panessa.

At least 55 records · Page 3Linked to original sources

arXiv2019

From radio-quiet to radio-silent: low luminosity Seyfert radio cores

A strong effort has been devoted to understand the physical origin of radio emission from low-luminosity AGN (LLAGN), but a comprehensive picture is still missing. We used high-resolution ($\le$1 arcsec), multi-frequency (1.5, 5.5, 9 and 14 GHz) NSF's Karl G. Jansky Very Large Array (VLA) observations to characterise the state of the nuclear region of ten Seyfert nuclei, which are the faintest members of a complete, distance-limited sample of 28 sources. With the sensitivity and resolution guaranteed by the VLA-A configuration, we measured radio emission for six sources (NGC3185, NGC3941, NGC4477, NGC4639, NGC4698 and NGC4725), while for the remaining four (NGC0676, NGC1058, NGC2685 and NGC3486) we put upper limits at tens uJy/beam level, below the previous 0.12 mJy/beam level of Ho&Ulvestad (2001), corresponding to luminosities down to L$\le10^{19}$ W/Hz at 1.5 GHz for the highest RMS observation. Two sources, NGC4639 and NGC4698, exhibit spectral slopes compatible with inverted spectra ($α\le$0, $S_ν\,\propto\,ν^{-α}$), hint for radio emission from an optically-thick core, while NGC4477 exhibits a steep (+0.52$\pm$0.09) slope. The detected sources are mainly compact on scales $\le$ arcseconds, predominantly unresolved, except NGC3185 and NGC3941, in which the resolved radio emission could be associated to star-formation processes. A significant X-ray - radio luminosities correlation is extended down to very low luminosities, with slope consistent with inefficient accretion, expected at such low Eddington ratios. Such sources will be one of the dominant Square Kilometre Array (SKA) population, allowing a deeper understanding of the physics underlying such faint AGN.

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arXiv2019

Probing restarting activity in hard X-ray selected giant radio galaxies

With their sizes larger than 0.7 Mpc, Giant Radio Galaxies (GRGs) are the largest individual objects in the Universe. To date, the reason why they reach such enormous extensions is still unclear. One of the proposed scenarios suggests that they are the result of multiple episodes of jet activity. Cross-correlating the INTEGRAL+Swift AGN population with radio catalogues (NVSS, FIRST, SUMSS), we found that 22% of the sources are GRG (a factor four higher than those selected from radio catalogues). Remarkably, 80% of the sample shows signs of restarting radio activity. The X-ray properties are consistent with this scenario, the sources being in a high-accretion, high-luminosity state with respect to the previous activity responsible for the radio lobes.

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arXiv2019

An XMM-Newton look at the strongly variable radio-weak BL Lac Fermi J1544-0639

Fermi J1544-0639/ASASSN-17gs/AT2017egv was identified as a gamma-ray/optical transient on May 15, 2017. Subsequent multiwavelength observations suggest that this source may belong to the new class of radio-weak BL Lacs. We studied the X-ray spectral properties and short-term variability of Fermi J1544-0639 to constrain the X-ray continuum emission mechanism of this peculiar source. We present the analysis of an XMM-Newton observation, 56 ks in length, performed on February 21, 2018. The source exhibits strong X-ray variability, both in flux and spectral shape, on timescales of ~10 ks, with a harder-when-brighter behaviour typical of BL Lacs. The X-ray spectrum is nicely described by a variable broken power law, with a break energy of around 2.7 keV consistent with radiative cooling due to Comptonization of broad-line region photons. We find evidence for a `soft excess', nicely described by a blackbody with a temperature of ~0.2 keV, consistent with being produced by bulk Comptonization along the jet.

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arXiv2018

Early Science with the Large Millimeter Telescope: an energy-driven wind revealed by massive molecular and fast X-ray outflows in the Seyfert Galaxy IRAS 17020+4544

We report on the coexistence of powerful gas outflows observed in millimeter and X-ray data of the Radio-Loud Narrow Line Seyfert 1 Galaxy IRAS 17020+4544. Thanks to the large collecting power of the Large Millimeter Telescope, a prominent line arising from the 12CO(1-0) transition was revealed in recent observations of this source. The complex profile is composed by a narrow double-peak line and a broad wing. While the double-peak structure may be arising in a disk of molecular material, the broad wing is interpreted as the signature of a massive outflow of molecular gas with an approximate bulk velocity of -660 km/s. This molecular wind is likely associated to a multi-component X-ray Ultra-Fast Outflow with velocities reaching up to ~0.1c and column densities in the range 10^{21-23.9} cm^-2 that was reported in the source prior to the LMT observations. The momentum load estimated in the two gas phases indicates that within the observational uncertainties the outflow is consistent with being propagating through the galaxy and sweeping up the gas while conserving its energy. This scenario, which has been often postulated as a viable mechanism of how AGN feedback takes place, has so far been observed only in ULIRGs sources. IRAS 17020+4544 with bolometric and infrared luminosity respectively of 5X10^{44} erg/s and 1.05X10^{11} L_sun appears to be an example of AGN feedback in a NLSy1 Galaxy (a low power AGN). New proprietary multi-wavelength data recently obtained on this source will allow us to corroborate the proposed hypothesis.

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arXiv2018

Hard X-ray selected giant radio galaxies - I. The X-ray properties and radio connection

We present the first broad-band X-ray study of the nuclei of 14 hard X-ray selected giant radio galaxies, based both on the literature and on the analysis of archival X-ray data from NuSTAR, XMM-Newton, Swift and INTEGRAL. The X-ray properties of the sources are consistent with an accretion-related X-ray emission, likely originating from an X-ray corona coupled to a radiatively efficient accretion flow. We find a correlation between the X-ray luminosity and the radio core luminosity, consistent with that expected for AGNs powered by efficient accretion. In most sources, the luminosity of the radio lobes and the estimated jet power are relatively low compared with the nuclear X-ray emission. This indicates that either the nucleus is more powerful than in the past, consistent with a restarting of the central engine, or that the giant lobes are dimmer due to expansion losses.

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arXiv2018

SKA-Athena Synergy White Paper

The Advanced Telescope for High Energy Astrophysics (Athena) is the X-ray observatory large mission selected by the European Space Agency (ESA), within its Cosmic Vision 2015-2025 programme, to address the "Hot and Energetic Universe" scientific theme (Nandra et al. 2013), and it is provisionally due for launch in the early 2030s. The Square Kilometer Array (SKA) is the next generation radio observatory and consists of two telescopes, one comprised of dishes operating at mid frequencies (SKA1-MID) and located in South Africa, and the other comprised of Log-Periodic antennas operating at low radio frequencies (SKA1-LOW), which will be located in Australia (Braun et al. 2017). The scientific commissioning of the radio telescope is planned to begin in 2021-2022. The SKA-Athena Synergy Team (SAST) has been tasked to single out the potential scientific synergies between Athena and SKA. The astrophysical community was involved in this exercise primarily through a dedicated SKA-Athena Synergy Workshop, which took place on April 24-25, 2017 at SKAO, Jodrell Bank, Manchester. The final result of the synergy exercise, this White Paper, describes in detail a number of scientific opportunities that will be opened up by the combination of Athena and SKA, these include: 1. the Cosmic Dawn; 2. the Evolution of black holes and galaxies; 3. Active galaxy feedback in galaxy clusters; 4. Non-thermal phenomena in galaxy clusters; 5. Detecting the cosmic web; 6. Black-hole accretion physics and astrophysical transients; 7. Galactic astronomy: stars, planets, pulsars and supernovae.

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arXiv2018

Variable broad lines and outflow in the weak blazar PBC J2333.9-2343

PBC J2333.9-2343 is a peculiar active nucleus with two giant radio lobes and a weak blazar-like nucleus at their center. In the present work we show new optical, UV, and X-ray data taken from the San Pedro Mártir telescope, the New Technology Telescope, NTT/EFOSC2, and the Swift/XRT satellite. The source is highly variable at all frequencies, in particular the strongest variations are found in the broad H$α$ component with a flux increase of 61$\pm$4 per cent between 2009 and 2016, following the X-ray flux increase of 62$\pm$6 per cent between 2010 and 2016. We also detected a broad H$β$ component in 2016, making the optical classification change from type 1.9 to type 1.8 in one year. We have also detected a broad component of the [OIII]$λ$5007 line, which is blue-shifted and of high velocity, suggesting an origin from a highly disturbed medium, possibly an outflow. The line flux variability and broad widths are indicative of a jet that is, at least in part, responsible for the ionization of the BLR and NLR.

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arXiv2018

LeMMINGs. I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

We present the first data release of high-resolution ($\leq0.2$ arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (LINER and Seyfert) and quiescent (HII galaxies and Absorption line galaxies, ALG), which are reclassified based upon revised emission-line diagrams. We detect radio emission $\gtrsim$ 0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for HII galaxies and 5/14 for ALGs) with radio sizes typically of $\lesssim$100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 10$^{32}$ to 10$^{40}$ erg s$^{-1}$: LINERs and HII galaxies show the highest and the lowest radio powers respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to $\sim$10$^{7}$ M$_{\odot}$, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted HII galaxies follow an optical fundamental plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; HII galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

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arXiv2018

FERMI transient J1544-0649: a flaring radio-weak BL Lac

On May 15th, 2017, the \emph{FERMI}/LAT gamma-ray telescope observed a transient source not present in any previous high-energy catalogue: J1544-0649. It was visible for two consecutive weeks, with a flux peak on May 21st. Subsequently observed by a \emph{Swift}/XRT follow-up starting on May 26, the X-ray counterpart position was coincident with the optical transient ASASSN-17gs = AT2017egv, detected on May 25, with a potential host galaxy at $z$=0.171. We conducted a 4-months follow-up in radio (Effelsberg-100m) and optical (San Pedro Mártir, 2.1m) bands, in order to build the overall Spectral Energy Distribution (SED) of this object. The radio data from 5 to 15 GHz confirmed the flat spectrum of the source, favoring a line of sight close to jet axis, not showing significant variability in the explored post-burst time-window. The Rx ratio, common indicator of radio loudness, gives a value at the border between the radio-loud and radio-quiet AGN populations. The Ca$_{\rm{II}}$ H\&K break value (0.29$\pm$0.05) is compatible with the range expected for the long-sought intermediate population between BL Lacs and FRI radio galaxies. An overall SED fitting from Radio to $γ$-ray band shows properties typical of a low-power BL Lac. As a whole, these results suggest that this transient could well be a new example of the recently discovered class of radio-weak BL Lac, showing for the first time a flare in the gamma/X-ray bands.

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arXiv2017

Where are Compton-thick radio galaxies? A hard X-ray view of three candidates

We present a broad-band X-ray spectral analysis of the radio-loud active galactic nuclei NGC 612, 4C 73.08 and 3C 452, exploiting archival data from NuSTAR, XMM-Newton, Swift and INTEGRAL. These Compton-thick candidates are the most absorbed sources among the hard X-ray selected radio galaxies studied in Panessa et al. (2016). We find an X-ray absorbing column density in every case below $1.5 \times 10^{24}$ cm$^{-2}$, and no evidence for a strong reflection continuum or iron K $α$ line. Therefore, none of these sources is properly Compton-thick. We review other Compton-thick radio galaxies reported in the literature, arguing that we currently lack strong evidences for heavily absorbed radio-loud AGNs.

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arXiv2017

Radio jets in NGC 4151: where eMERLIN meets HST

We present high-sensitivity eMERLIN radio images of the Seyfert galaxy NGC 4151 at 1.5 GHz. We compare the new eMERLIN images to those from archival MERLIN observations in 1993 to determine the change in jet morphology in the 22 years between observations. We report an increase by almost a factor of 2 in the peak flux density of the central core component, C4, thought to host the black hole, but a probable decrease in some other components, possibly due to adiabatic expansion. The core flux increase indicates an AGN which is currently active and feeding the jet. We detect no significant motion in 22 years between C4 and the component C3, which is unresolved in the eMERLIN image. We present a spectral index image made within the 512 MHz band of the 1.5 GHz observations. The spectrum of the core, C4, is flatter than that of other components further out in the jet. We use HST emission line images (H$α$, [O III] and [O II]) to study the connection between the jet and the emission line region. Based on the changing emission line ratios away from the core and comparison with the eMERLIN radio jet, we conclude that photoionisation from the central AGN is responsible for the observed emission line properties further than 4" (360 pc) from the core, C4. Within this region, several evidences (radio-line co-spatiality, low [O III]/H$α$ and estimated fast shocks) suggest additional ionisation from the jet.

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arXiv2017

ESO-Athena Synergy White Paper

The Advanced Telescope for High ENergy Astrophysics (Athena) is the X-ray observatory mission selected by ESA within its Cosmic Vision 2015-2025 programme to address the Hot and Energetic Universe scientific theme. The ESO-Athena Synergy Team (EAST) has been tasked to single out the potential scientific synergies between Athena and optical/near-infrared (NIR) and sub/mm ground based facilities, in particular those of ESO (i.e., the VLT and ELT, ALMA and APEX), by producing a White Paper to identify and develop the: 1. needs to access ESO ground-based facilities to achieve the formulated Athena science objectives; 2. needs to access Athena to achieve the formulated science objectives of ESO facilities contemporary to Athena; 3. science areas where the synergetic use of Athena and ESO facilities in the late 2020s will result in scientific added value. Community input to the process happened primarily via a dedicated ESO - Athena Synergy Workshop that took place on Sept. 14 - 16, 2016 at ESO, Garching. This White Paper presents the results of the EAST's work, sorted by synergy area, and deals with the following topics: 1. the Hot Universe: Early groups and clusters and their evolution, Physics of the Intracluster medium, Missing baryons in cosmic filaments; 2. the Energetic Universe: Supermassive black hole (SMBH) history, SMBH accretion disks, Active Galactic Nuclei feedback - Molecular outflows, Ultra-fast outflows, Accretion Physics, Transient Science; 3. Observatory Science: Star Formation, Stars. It then discusses the optical-NIR-sub-mm perspective by providing details on VLT/MOONS, the E-ELT instruments, in particular the MOS, VISTA/4MOST, the ESO and ALMA archives, future ALMA and ESO developments, and finally the (likely) ESO - Athena astronomical scene in the 2020s. (abridged)

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arXiv2017

Restarting activity in the nucleus of PBC J2333.9-2343: an extreme case of jet realignment

PBC J2333.9-2343 is a giant radio galaxy which shows different characteristics at different wavebands that are difficult to explain within the actual generic schemes of unification of active galactic nuclei (AGN), thus being a good candidate to host different phases of nuclear activity. We aim at disentangling the nature of this AGN by using simultaneous multiwavelength data. We obtained data in 2015 from the Very Long Baseline Array (VLBA), the San Pedro Mártir telescope, and the XMM-Newton}observatories. This allows the study of the nuclear parts of the galaxy through its morphology and spectra, as well as the analysis of the spectral energy distribution (SED). We also reanalysed optical data from the San Pedro Mártir telescope from 2009 previously presented in Parisi et al. (2012) for a homogeneous comparison. At X-ray frequencies, the source is unabsorbed. The optical spectra are of a type 1.9 AGN, both in 2009 and 2015, although showing a broader component in 2015. The VLBA radio images show an inverted spectrum with self-absorbed, optically thick compact core and steep spectrum, optically thin jet. The SED resembles that of typical blazars and is best represented by an external Compton (EC) model with a viewing angle of $\sim$ 3-6 degrees. The apparent size of the large scale structure of PBC J2333.9-2343 must correspond to an intrinsic deprojected value of $\sim 7$ Mpc for $θ_v<10^\circ$, and to $> 13$ Mpc for $θ_v<5^\circ$, a value much larger than the bigger giant radio galaxy known (4.5 Mpc). The above arguments suggest that PBC J2333.9-2343 has undergone through a new episode of nuclear activity and that the direction of the new jet has changed, in the plane of the sky and is now pointing towards us, making this source from being a radio galaxy to become a blazar, a very exceptional case of restarting activity.

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arXiv2017

Investigating the X-ray counterparts to unidentified sources in the 1000-orbit INTEGRAL/IBIS catalogue

The latest INTEGRAL/IBIS all-sky survey lists 219 hard X-ray sources whose nature is still unknown. We report on our ongoing campaign aimed at identifying these high-energy emitters by exploiting the focusing capabilities of the X-ray Telescope (XRT, 0.2-10 keV) on board Swift, which allow an enhancement of the source localisation to arcsec level, thus facilitating the identification of the likely counterpart. By cross-correlating the list of the unidentified IBIS sources included in the latest IBIS catalogue with Swift/XRT archival data, we found a set of 14 objects, not yet reported in the literature, for which XRT data were available. We found no detection in only one case, a single X-ray association in 9 sources, and 2/3 associations in the remaining objects. We then made use of multi-waveband archives to search for counterparts at other wavelengths of these XRT detections and exploited X-ray spectral information in an attempt to determine their nature and association with the IBIS object. As a result of our analysis, we identified a single counterpart for 13 sources, although in some cases its nature/class could not be assessed on the basis of the information collected. More specifically, we found that SWIFT J0924.2-3141 and SWIFT J1839.1-5717 are absorbed AGN, while SWIFT J0800.7-4309 and 1SWXRT J230642.8+550817 are Cataclysmic Variable binary systems. Finally, we found that IGR J14059-6116 is likely associated with the Fermi source 3FGL J1405.4-6119. In the case of XMMSL1 J030715.5-545536 no XRT counterpart was detected. In all the other cases, optical/infrared spectroscopy is necessary to classify properly each X-ray counterpart and confirm their association with the INTEGRAL/IBIS detection.

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arXiv2017

Coexistence of a non thermal jet and a complex ultra fast X-ray outflow in a moderately luminous AGN

Context: Recent XMM-Newton observations have revealed that IRAS 17020+4544 is a very unusual example of black hole wind-produced feedback by a moderately luminous AGN in a spiral galaxy. Aims: Since the source is known for being a radio emitter, we investigated about the presence and the properties of a non-thermal component. Methods: We observed IRAS 17020+4544 with the Very Long Baseline Array at 5, 8, 15, and 24 GHz within a month of the 2014 XMM-Newton observations. We further analysed archival data taken in 2000 and 2012. Results: We detect the source at 5 GHz and on short baselines at 8 GHz. At 15 and 24 GHz, the source is below our baseline sensitivity for fringe fitting, indicating the lack of prominent compact features. The morphology is that of an asymmetric double, with significant diffuse emission. The spectrum between 5 and 8 GHz is rather steep ($S(ν)\simν^{-(1.0\pm0.2)}$). Our re-analysis of the archival data at 5 and 8 GHz provides results consistent with the new observations, suggesting that flux density and structural variability are not important in this source. We put a limit on the separation speed between the main components of $<0.06c$. Conclusions: IRAS 17020+4544 shows interesting features of several classes of objects: its properties are typical of compact steep spectrum sources, low power compact sources, radio-emitting narrow line Seyfert 1 galaxies. However, it can not be classified in any of these categories, remaining so far a one-of-a-kind object.

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arXiv2016

The column density distribution of hard X-ray radio galaxies

In order to investigate the role of absorption in AGN with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/IBIS and Swift/BAT AGN catalogues (~7-10% of the total AGN population). The 64 radio galaxies have a typical FRII radio morphology and are characterized by high 20-100 keV luminosities (from 10^42 to 10^46 erg/s) and high Eddington ratios (Log L_{Bol}/L_{Edd} typically larger than ~0.01). The observed fraction of absorbed AGN (N_{H} > 10^{22} cm^{-2}) is around 40% among the total sample, and ~75% among type 2 AGN. The majority of obscured AGN are narrow line objects, while unobscured AGN are broad line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ~2-3%, in comparison with the 5-7% found in radio-quiet hard X-ray selected AGN. We have estimated the absorption and Compton thick fractions in a hard X-ray sample containing both radio galaxies and non-radio galaxies and therefore affected by the same selection biases. No statistical significant difference was found in the absorption properties of radio galaxies and non radio galaxies sample. In particular, the Compton thick objects are likely missing in both samples and the fraction of obscured radio galaxies appears to decrease with luminosity as observed in hard X-ray non-radio galaxies.

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arXiv2016

Soft Gamma-ray selected radio galaxies: favouring giant size discovery

Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of 64 confirmed plus 3 candidate radio galaxies selected in the soft gamma-ray band. The sample covers all optical classes and is dominated by objects showing a FR II radio morphology; a large fraction (70%) of the sample is made of radiative mode or High Excitation Radio Galaxies (HERG). We have measured the source size on NVSS, FIRST and SUMSS images and have compared our findings with data in the literature obtaining a good match. We surprisingly found that the soft gamma-ray selection favours the detection of large size radio galaxies: 60% of objects in the sample have size greater than 0.4 Mpc while around 22% reach dimension above 0.7 Mpc at which point they are classified as Giant Radio Galaxies or GRGs, the largest and most energetic single entities in the Universe. Their fraction among soft gamma ray selected radio galaxies is significantly larger than typically found in radio surveys, where only a few percent of objects (1-6%) are GRGs. This may partly be due to observational biases affecting radio surveys more than soft gamma ray surveys, thus disfavouring the detection of GRGs at lower frequencies. The main reasons and/or conditions leading to the formation of these large radio structures are still unclear with many parameters such as high jet power, long activity time and surrounding environment all playing a role; the first two may be linked to the type of AGN discussed in this work and partly explain the high fraction of GRGs found in the present sample. Our result suggests that high energy surveys may be a more efficient way than radio surveys to find these peculiar objects.

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arXiv2014

The physics of the radio emission in the quiet side of the AGN population with the SKA

Despite targets of many multiwavelength campaigns, the main physical processes at work in AGN are still under debate. In particular the origin of the radio emission and the mechanisms involved are among the open questions in astrophysics. In the radio-loud AGN population the radio emission is linked to the presence of bipolar outflows of relativistic jets. However, the large majority of the AGN population do not form powerful highly-relativistic jets on kpc scales and are characterized by radio luminosity up to 10^23 W/Hz at 1.4 GHz, challenging our knowledge on the physical processes at the basis of the radio emission in radio-quiet objects. The main mechanisms proposed so far are synchrotron radiation from mildly relativistic mini-jets, thermal cyclo-synchrotron emission by low-efficiency accretion flow (like ADAF or ADIOS), or thermal free-free emission from the X-ray heated corona or wind. The difficulty in understanding the main mechanism involved is related to the weakness of these objects, which precludes the study of non-local radio-quiet AGN. Multifrequency, high-sensitivity radio observations are crucial to constrain the nature of the power engine, and they may help in distinguishing between the contribution from star formation and AGN activity. The advent of the SKA, with its sub-arcsecond resolution and unprecedented sensitivity will allow us to investigate these processes in radio-quiet AGN, even at high redshift for the first time. Both the broad-band radio spectrum and the polarization information will help us in disentangling between non-thermal and thermal origin of the radio emission. The jump in sensitivity of a few order of magnitudes at the (sub-)uJy level will enable us to detect radio emission from a large number of radio-quiet AGN at high redshift, providing a fundamental step in our understanding of their cosmological evolution. (Abridged)

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