Winds in the AGN environment : new perspectives from high resolution X-ray spectroscopy

In recent years, winds were recognized as an important ingredient in the AGN picture. Outflows of photoionized gas, which produce blueshifted absorption features detectable in the X-ray and in the UV band, are present in about 50% of Seyfert 1 galaxies. Combining observations at high spectral resolution with photoionization modeling techniques, the kinetics, and the ionization conditions of the outflowing gas can be diagnosed with high accuracy. In this thesis, we applied these methods to three cases of study, obtaining a variety of results. In the X-ray spectrum of the Seyfert 1 galaxy 1H 0419-577, we detected the absorption lines from a galactic scale outflow already observed in the UV. In the case of the prototypical type 1 AGN NGC 5548, we discovered a lowly-ionized, patchy wind located in the nuclear region. We show that the emergence of this obscuring wind have drastically changed the spectral appearance of the source in the soft X-ray and in the UV band. Finally, we characterized a photoionized gas outflow in 4C +74.26, which is one of the few radio-loud AGN in which signatures of photoionized gas could be detected.High Energy Astrophysic

Chandra imaging of the ∼\simkpc extended outflow in 1H 0419-577

The Seyfert 1 galaxy 1H 0419-577 hosts a $\sim$kpc extended outflow that is evident in the [\ion{O}{iii}] image and that is also detected as a warm absorber in the UV/X-ray spectrum. Here, we analyze a $\sim$30 ks Chandra-ACIS X-ray image, with the aim of resolving the diffuse extranuclear X-ray emission and of investigating its relationship with the galactic outflow. Thanks to its sub-arcsecond spatial resolution, Chandra resolves the circumnuclear X-ray emission, which extends up to a projected distance of at least $\sim$16 kpc from the center. The morphology of the diffuse X-ray emission is spherically symmetrical. We could not recover a morphological resemblance between the soft X-ray emission and the ionization bicone that is traced by the [\ion{O}{iii}] outflow. we argue that the photoionized gas nebula must be distributed mostly along the polar directions, outside our line of sight. In this geometry, the X-ray/UV warm absorber must trace a different gas component, physically disconnected from the emitting gas, and located closer to the equatorial plane.Comment: accepted for publications A&

Edge-weighting of gene expression graphs

In recent years, considerable research efforts have been directed to micro-array technologies and their role in providing simultaneous information on expression profiles for thousands of genes. These data, when subjected to clustering and classification procedures, can assist in identifying patterns and providing insight on biological processes. To understand the properties of complex gene expression datasets, graphical representations can be used. Intuitively, the data can be represented in terms of a bipartite graph, with weighted edges corresponding to gene-sample node couples in the dataset. Biologically meaningful subgraphs can be sought, but performance can be influenced both by the search algorithm, and, by the graph-weighting scheme and both merit rigorous investigation. In this paper, we focus on edge-weighting schemes for bipartite graphical representation of gene expression. Two novel methods are presented: the first is based on empirical evidence; the second on a geometric distribution. The schemes are compared for several real datasets, assessing efficiency of performance based on four essential properties: robustness to noise and missing values, discrimination, parameter influence on scheme efficiency and reusability. Recommendations and limitations are briefly discussed

Simultaneous XMM-\textit{Newton} and HST-COS observation of 1H0419-577: II. Broadband spectral modeling of a variable Seyfert galaxy

In this paper we present the longest exposure (97 ks) XMM-Newton EPIC-pn spectrum ever obtained for the Seyfert 1.5 galaxy 1H 0419-577. With the aim of explaining the broadband emission of this source, we took advantage of the simultaneous coverage in the optical/UV that was provided in the present case by the XMM-Newton Optical Monitor and by a HST-COS observation. Archival FUSE flux measurements in the FUV were also used for the present analysis. We successfully modeled the X-ray spectrum together with the optical/UV fluxes data points using a Comptonization model. We found that a blackbody temperature of $T \sim 56$ eV accounts for the optical/UV emission originating in the accretion disk. This temperature serves as input for the Comptonized components that model the X-ray continuum. Both a warm ($T_{\rm wc} \sim 0.7$ keV, $\tau_{\rm wc} \sim 7$) and a hot corona ($T_{\rm hc} \sim 160$ keV, $\tau_{\rm hc} \sim 0.5$) intervene to upscatter the disk photons to X-ray wavelengths. With the addition of a partially covering ($C_v\sim50\%$) cold absorber with a variable opacity (${\it N}_{\rm H}\sim [10^{19}- 10^{22}] \,\rm cm^{-2}$), this model can well explain also the historical spectral variability of this source, with the present dataset presenting the lowest one (${\it N}_{\rm H}\sim 10^{19} \, \rm cm^{-2}$). We discuss a scenario where the variable absorber, getting ionized in response to the variations of the X-ray continuum, becomes less opaque in the highest flux states. The lower limit for the absorber density derived in this scenario is typical for the broad line region clouds. Finally, we critically compare this scenario with all the different models (e.g. disk reflection) that have been used in the past to explain the variability of this sourceComment: 12 pages, 9 figure

Anatomy of the AGN in NGC 5548: V. A clear view of the X-ray narrow emission lines

Context. Our consortium performed an extensive multi-wavelength campaign of the nearby Seyfert 1 galaxy NGC 5548 in 2013-14. The source appeared unusually heavily absorbed in the soft X-rays, and signatures of outflowing absorption were also present in the UV. He-like triplets of neon, oxygen and nitrogen, and radiative recombination continuum (RRC) features were found to dominate the soft X-ray spectrum due to the low continuum flux. Aims. Here we focus on characterising these narrow emission features using data obtained from the XMM-Newton RGS (770 ks stacked spectrum). Methods. We use SPEX for our initial analysis of these features. Self-consistent photoionisation models from Cloudy are then compared with the data to characterise the physical conditions of the emitting region. Results. Outflow velocity discrepancies within the O VII triplet lines can be explained if the X-ray narrow-line region (NLR) in NGC 5548 is absorbed by at least one of the six warm absorber components found by previous analyses. The RRCs allow us to directly calculate a temperature of the emitting gas of a few eV ($\sim10^{4}$ K), favouring photoionised conditions. We fit the data with a Cloudy model of log $\xi = 1.45 \pm 0.05$ erg cm s$^{-1}$, log $N_H = 22.9 \pm 0.4$ cm$^{-2}$ and log v$_{turb} = 2.25 \pm 0.5$ km s$^{-1}$ for the emitting gas; this is the first time the X-ray NLR gas in this source has been modelled so comprehensively. This allows us to estimate the distance from the central source to the illuminated face of the emitting clouds as $13.9 \pm 0.6$ pc, consistent with previous work.Comment: Accepted by A&A, 15 pages, 6 figure

Sloshing cold fronts in galaxy groups and their perturbing disk galaxies: an X-ray, Optical and Radio Case Study

We present a combined X-ray, optical, and radio analysis of the galaxy group IC 1860 using the currently available Chandra and XMM data, literature multi-object spectroscopy data and GMRT data. The Chandra and XMM imaging and spectroscopy reveal two surface brightness discontinuities at 45 and 76 kpc shown to be consistent with a pair of cold fronts. These features are interpreted as due to sloshing of the central gas induced by an off-axis minor merger with a perturber. This scenario is further supported by the presence of a peculiar velocity of the central galaxy IC 1860 and the identification of a possible perturber in the optically disturbed spiral galaxy IC 1859. The identification of the perturber is consistent with the comparison with numerical simulations of sloshing. The GMRT observation at 325 MHz shows faint, extended radio emission contained within the inner cold front, as seen in some galaxy clusters hosting diffuse radio mini-halos. However, unlike mini-halos, no particle reacceleration is needed to explain the extended radio emission, which is consistent with aged radio plasma redistributed by the sloshing. There is strong analogy of the X-ray and optical phenomenology of the IC 1860 group with two other groups, NGC 5044 and NGC 5846, showing cold fronts. The evidence presented in this paper is among the strongest supporting the currently favored model of cold-front formation in relaxed objects and establishes the group scale as a chief environment to study this phenomenon.Comment: 22 pages, 21 figures, accepted for publication in the Astrophysical Journa

Discovery of X-ray polarization angle rotation in the jet from blazar Mrk 421

Full list of the authors: Di Gesu, Laura; Marshall, Herman L.; Ehlert, Steven R.; Kim, Dawoon E.; Donnarumma, Immacolata; Tavecchio, Fabrizio; Liodakis, Ioannis; Kiehlmann, Sebastian; Agudo, Iván; Jorstad, Svetlana G.; Muleri, Fabio; Marscher, Alan P.; Puccetti, Simonetta; Middei, Riccardo; Perri, Matteo; Pacciani, Luigi; Negro, Michela; Romani, Roger W.; Di Marco, Alessandro; Blinov, Dmitry; Bourbah, Ioakeim G.; Kontopodis, Evangelos; Mandarakas, Nikos; Romanopoulos, Stylianos; Skalidis, Raphael; Vervelaki, Anna; Casadio, Carolina; Escudero, Juan; Myserlis, Ioannis; Gurwell, Mark A.; Rao, Ramprasad; Keating, Garrett K.; Kouch, Pouya M.; Lindfors, Elina; Aceituno, Francisco José; Bernardos, Maria I.; Bonnoli, Giacomo; Casanova, Víctor; García-Comas, Maya; Agís-González, Beatriz; Husillos, César; Marchini, Alessandro; Sota, Alfredo; Imazawa, Ryo; Sasada, Mahito; Fukazawa, Yasushi; Kawabata, Koji S.; Uemura, Makoto; Mizuno, Tsunefumi; Nakaoka, Tatsuya; Akitaya, Hiroshi; Savchenko, Sergey S.; Vasilyev, Andrey A.; Gómez, José L.; Antonelli, Lucio A.; Barnouin, Thibault; Bonino, Raffaella; Cavazzuti, Elisabetta; Costamante, Luigi; Chen, Chien-Ting; Cibrario, Nicolò; De Rosa, Alessandra; Di Pierro, Federico; Errando, Manel; Kaaret, Philip; Karas, Vladimir; Krawczynski, Henric; Lisalda, Lindsey; Madejski, Grzegorz; Malacaria, Christian; Marin, Frédéric; Marinucci, Andrea; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; O'Dell, Stephen L.; Paggi, Alessandro; Peirson, Abel L.; Petrucci, Pierre-Olivier; Ramsey, Brian D.; Tennant, Allyn F.; Wu, Kinwah; Bachetti, Matteo; Baldini, Luca; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Brez, Alessandro; Bucciantini, Niccolò; Capitanio, Fiamma; Castellano, Simone; Ciprini, Stefano; Costa, Enrico; Del Monte, Ettore; Di Lalla, Niccolò; Doroshenko, Victor; Dovčiak, Michal; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Ferrazzoli, Riccardo; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Heyl, Jeremy; Iwakiri, Wataru; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; La Monaca, Fabio; Latronico, Luca; Maldera, Simone; Manfreda, Alberto; Ng, C. -Y.; Omodei, Nicola; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Pesce-Rollins, Melissa; Pilia, Maura; Possenti, Andrea; Poutanen, Juri; Rankin, John; Ratheesh, Ajay; Roberts, Oliver J.; Sgrò, Carmelo; Slane, Patrick; Soffitta, Paolo; Spandre, Gloria; Swartz, Douglas A.; Tamagawa, Toru; Taverna, Roberto; Tawara, Yuzuru; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Vink, Jacco; Weisskopf, Martin C.; Xie, Fei; Zane, SilviaThe magnetic-field conditions in astrophysical relativistic jets can be probed by multiwavelength polarimetry, which has been recently extended to X-rays. For example, one can track how the magnetic field changes in the flow of the radiating particles by observing rotations of the electric vector position angle ¿. Here we report the discovery of a ¿X rotation in the X-ray band in the blazar Markarian¿421 at an average flux state. Across the 5¿days of Imaging X-ray Polarimetry Explorer observations on 4¿6 and 7¿9 June 2022, ¿X rotated in total by ¿360°. Over the two respective date ranges, we find constant, within uncertainties, rotation rates (80¿±¿9° per day and 91¿±¿8° per day) and polarization degrees (¿X¿=¿10%¿±¿1%). Simulations of a random walk of the polarization vector indicate that it is unlikely that such rotation(s) are produced by a stochastic process. The X-ray-emitting site does not completely overlap the radio, infrared and optical emission sites, as no similar rotation of ¿ was observed in quasi-simultaneous data at longer wavelengths. We propose that the observed rotation was caused by a helical magnetic structure in the jet, illuminated in the X-rays by a localized shock propagating along this helix. The optically emitting region probably lies in a sheath surrounding an inner spine where the X-ray radiation is released. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC), and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC). The IAA-CSIC group acknowledges financial support from the grant CEX2021-001131-S funded by MCIN/AEI/10.13039/501100011033 to the Instituto de Astrofisica de Andalucia-CSIC and through grant PID2019-107847RB-C44. The POLAMI observations were carried out at the IRAM 30?m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The Submillimetre Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. Mauna Kea, the location of the SMA, is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit. Some of the data reported here are based on observations made with the Nordic Optical Telescope, owned in collaboration with the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. E.L. was supported by Academy of Finland projects 317636 and 320045. The data presented here were obtained (in part) with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOT. We are grateful to V. Braga, M. Monelli and M. Saenchez Benavente for performing the observations at the Nordic Optical Telescope. Part of the French contributions is supported by the Scientific Research National Center (CNRS) and the French spatial agency (CNES). The research at Boston University was supported in part by National Science Foundation grant AST-2108622, NASA Fermi Guest Investigator grants 80NSSC21K1917 and 80NSSC22K1571, and NASA Swift Guest Investigator grant 80NSSC22K0537. This research was conducted in part using the Mimir instrument, jointly developed at Boston University and Lowell Observatory and supported by NASA, NSF and the W.M. Keck Foundation. We thank D. Clemens for guidance in the analysis of the Mimir data. This work was supported by JST, the establishment of university fellowships towards the creation of science and technology innovation, grant number JPMJFS2129. This work was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grant number JP21H01137. This work was also partially supported by the Optical and Near-Infrared Astronomy Inter-University Cooperation Program from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. We are grateful to the observation and operating members of the Kanata Telescope. Some of the data are based on observations collected at the Observatorio de Sierra Nevada, owned and operated by the Instituto de Astrofisica de Andalucia (IAA-CSIC). Further data are based on observations collected at the Centro Astronomico Hispano en Andalucia (CAHA), operated jointly by Junta de Andalucia and Consejo Superior de Investigaciones Cientificas (IAA-CSIC). This research has made use of data from the RoboPol programme, a collaboration between Caltech, the University of Crete, IA-FORTH, IUCAA, the MPIfR and the Nicolaus Copernicus University, which was conducted at Skinakas Observatory in Crete, Greece. D.B., S.K., R.S. and N.M., acknowledge support from the European Research Council (ERC) under the European Unions Horizon 2020 Research and Innovation programme under grant agreement no. 771282. C.C. acknowledges support from the European Research Council (ERC) under the HORIZON ERC Grants 2021 programme under grant agreement no. 101040021. The research at Boston University was supported in part by National Science Foundation grant AST-2108622, NASA Fermi Guest Investigator grant 80NSSC21K1917 and 80NSSC22K1571, and NASA Swift Guest Investigator grant 80NSSC22K0537. This work was supported by NSF grant AST-2109127. We acknowledge the use of public data from the Swift data archive. Data from the Steward Observatory spectropolarimetric monitoring project were used. This programme is supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G and NNX15AU81G. We acknowledge funding to support our NOT observations from the Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Finland (Academy of Finland grant no 306531). This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284 and 80NSSC18K1575; by-products of the NEO search include images and catalogues from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen's University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory and The Millennium Institute of Astrophysics (MAS), Chile. The Very Long Baseline Array is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc