Active Galaxies Newsletter
An electronic publication dedicated to the observations and theory of active galaxiesEdited by Megan Argo
The Active Galaxies Newsletter is an electronic publication dedicated to the observation and theory of active galaxies. It is intended to be used to notify others in the field of recently accepted papers, conference proceedings and dissertations, and also contains announcements of jobs and conferences. It is produced monthly and sent to over 600 subscribers.
The Latex macros for submitting contributions of all sorts is available here and are also appended to each issue of the newsletter. The editor may reject submissions which do not use the template.
Information and web-links for upcoming meetings, conferences, jobs and special announcements, as well as recent thesis abstracts can now be directly linked to on the left hand side bar. These pages are updated throughout the month as soon as adverts and announcements are received. To advertise forthcoming job opportunities and meetings please email the editor with the relevant information. These adverts are also run in newsletter itself.
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Latest Issue:
| Active | An electronic publication dedicated to |
| Galaxies | the observation and theory of |
| Newsletter | active galaxies |
| No. 225 -- July 2016 | Editor: Megan Argo (agnews@manchester.ac.uk) |
Jobs Adverts - Meetings Adverts - Special Announcements
Welcome to all the new subscribers, and thanks to everyone who contributed to this issue of the Active Galaxies Newsletter.
This newsletter is intended to disseminate paper abstracts, meeting announcements, job adverts and other information which may be of interest to the active galaxies community. It is produced monthly and, whilst the deadline for contributions is the last day of the month, contributions may be submitted at any time.
The Latex macros for submitting abstracts and dissertation abstracts are appended to each issue of the newsletter and are also available on the web page. Please note that the editor may reject submissions which do not use the template. As always, any suggestions or feedback regarding the newsletter are welcome.
Thanks for your continued subscription.
Soft X-Ray Excess from Shocked Accreting Plasma in Active Galactic Nuclei
K. Fukumura1,2, D. Hendry1, P. Clark1, F. Tombesi3,4, and M. Takahashi5
1. Department of Physics and Astronomy, James Madison University, Harrisonburg, VA 22807
2. KITP Scholar at UC Santa Barbara
3. Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771
4. Department of Astronomy and CRESST, University of Maryland, College Park, MD20742
5. Department of Physics and Astronomy, Aichi University of Education, Kariya, Aichi 448-8542, Japan
We propose a novel theoretical model to describe a physical identity of the soft X-ray excess, ubiquitously detected in many Seyfert galaxies, by considering a steady-state, axisymmetric plasma accretion within the innermost stable circular orbit (ISCO) around a black hole (BH) accretion disk. We extend our earlier theoretical investigations on general relativistic magnetohydrodynamic (GRMHD) accretion which has implied that the accreting plasma can develop into a standing shock for suitable physical conditions causing the downstream flow to be sufficiently hot due to shock compression. We numerically calculate to examine, for sets of fiducial plasma parameters, a physical nature of fast MHD shocks under strong gravity for different BH spins. We show that thermal seed photons from the standard accretion disk can be effectively Compton up-scattered by the energized sub-relativistic electrons in the hot downstream plasma to produce the soft excess feature in X-rays. As a case study, we construct a three-parameter Comptonization model of inclination angle θobs, disk photon temperature kTin and downstream electron energy kTe to calculate the predicted spectra in comparison with a 60 ks XMM-Newton/EPIC-pn spectrum of a typical radio-quiet Seyfert 1 AGN, Ark 120. Our χ2-analyses demonstrate that the model is plausible in successfully describing data for both non-spinning and spinning BHs with the derived range of 61.3 keV ≲ kTe ≲ 144.3 keV, 21.6 eV ≲ kTin ≲ 34.0≲eV and 17.5° ≲θobs ≲ 42.6° indicating a compact Comptonizing region of 3−4 gravitational radii that resembles the putative X-ray coronae.
Accepted to ApJ (2016), 39 pages, 3 table, 11 figures
E-mail contact: fukumukx@jmu.edu
Preprint available at http://adsabs.harvard.edu/abs/2016arXiv160601851F
Theoretical reevaluations of the black hole mass - bulge mass relation - I. Effect of the seed black hole mass
Hikari Shirakata1, Toshihiro Kawaguchi2, Takashi Okamoto1, Ryu Makiya3,4, Tomoaki Ishiyama5, Yoshiki Matsuoka6,7, Masahiro Nagashima8, Motohiro Enoki9, Taira Oogi3, and Masakazu A. R. Kobayashi10
1. Department of Cosmosciences, Hokkaido University, N10 W8, Kitaku, Sapporo, 060-0810, Japan
2. Department of Liberal Arts and Sciences, Sapporo Medical University, S1W17, Chuo-ku, Sapporo, 060-8556, Japan
3. Kavli Institute for the Physics and Mathematics of the universe, Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa, 277-8583 Japan
4. Max-Planck-Institut fur Astrophysik, Karl-Schwarzschild Str. 1, D-85741 Garching, Germany
5. Institute of Management and Information Technologies, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan
6. National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
7. Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588, Japan
8. Faculty of Education, Bunkyo University, Koshigaya, Saitama 343-8511, Japan
9. Faculty of Business Administration, Tokyo Keizai University, Kokubunji, Tokyo, 185-8502, Japan
10. Faculty of Natural Sciences, National Institute of Technology, Kure College, 2-2-11, Agaminami, Kure, Hiroshima, 737-8506, Japan
We explore the effect of varying the mass of the seed black hole on the resulting black hole mass - bulge mass relation at z ∼ 0, using a semi-analytic model of galaxy formation combined with large cosmological N-body simulations. We constrain our model by requiring the observed properties of galaxies at z ∼ 0 are reproduced. In keeping with previous semi-analytic models, we place a seed black hole immediately after a galaxy forms. When the mass of the seed is set at 105 M⊙, we find that the model results become inconsistent with recent observational results of the black hole mass - bulge mass relation for dwarf galaxies. In particular, the model predicts that bulges with ∼109 M⊙ harbour larger black holes than observed. On the other hand, when we employ seed black holes with 103 M⊙, or randomly select their mass within a 103-5 M⊙ range, the resulting relation is consistent with observation estimates, including the observed dispersion. We find that to obtain stronger constraints on the mass of seed black holes, observations of less massive bulges at z ∼0 are a more powerful comparison than the relations at higher redshifts.
Accepted by MNRAS Letter DOI: 10.1093/mnrasl/slw125
E-mail contact: shirakata@astro1.sci.hokudai.ac.jp
Preprint available at http://arxiv.org/abs/1604.05317
Upholding the Unified Model for Active Galactic Nuclei: VLT/FORS2 Spectropolarimetry of Seyfert 2 galaxies
C. Ramos Almeida1,2, M. J. Martínez González1,2, A. Asensio Ramos1,2, J. A. Acosta-Pulido1,2, S. F. Hönig3, A. Alonso-Herrero4,5, C. N. Tadhunter6, and O. González-Martín7
1. Instituto de Astrofísica de Canarias, Calle Vía Láctea, s/n, E-38205, La Laguna, Tenerife, Spain
2. Departamento de Astrofísica, Universidad de La Laguna, E-38205, La Laguna, Tenerife, Spain
3. School of Physics & Astronomy, University of Southampton, Southampton, SO17 1BJ, UK
4. Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, E-28692, Villanueva de la Cañada, Madrid, Spain
5. Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
6. Department of Physics & Astronomy, University of Sheffield, Sheffield S3 7RH, UK
7. Instituto de Radioastronomía y Astrofísica (IRAF-UNAM), 3-72 (Xangari), 8701, Morelia, Mexico
The origin of the unification model for Active Galactic Nuclei (AGN) was the detection of broad hydrogen recombination lines in the optical polarized spectrum of the Seyfert 2 galaxy (Sy2) NGC1068. Since then, a search for the hidden broad-line region (HBLR) of nearby Sy2s started, but polarized broad lines have only been detected in ∼30−40% of the nearby Sy2s observed to date. Here we present new VLT/FORS2 optical spectropolarimetry of a sample of 15 Sy2s, including Compton-thin and Compton-thick sources. The sample includes six galaxies without previously published spectropolarimetry, some of them normally treated as non-hidden BLR (NHBLR) objects in the literature, four classified as NHBLR, and five as HBLR based on previous data. We report ≥4σ detections of a HBLR in 11 of these galaxies (73% of the sample) and a tentative detection in NGC5793, which is Compton-thick according to the analysis of X-ray data performed here. Our results confirm that at least some NHBLRs are misclassified, bringing previous publications reporting differences between HBLR and NHBLR objects into question. We detect broad Hα and Hβ components in polarized light for 10 targets, and just broad Hα for NGC5793 and NGC6300, with line widths ranging between 2100 and 9600 km s-1. High bolometric luminosities and low column densities are associated with higher polarization degrees, but not necessarily with the detection of the scattered broad components.
Accepted by MNRAS.
E-mail contact: cra@iac.es
Preprint available at http://arxiv.org/abs/1606.02204
A growth-rate indicator for Compton-thick active galactic nuclei
M. Brightman1, A. Masini2,3, D. R. Ballantyne4, M. Balokovic1, W. N. Brandt5, C.-T. Chen5, A. Comastri2, D. Farrah6, P. Gandhi7, F. A. Harrison1, C. Ricci8, D. Stern9, D. J. Walton9,1
1. Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Pasadena, CA 91125, USA
2. INAF Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna, Italy
3. Dipartimento di Fisica e Astronomia (DIFA), Universitá di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
4. Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
5. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
6. Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
7. Department of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
8. Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
9. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGN) is difficult to measure. A statistically significant correlation between the Eddington ratio, λEdd, and the X-ray power-law index, Γ, observed in unobscured AGN offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line-of-sight to the central engine is heavily obscured, the recovery of the intrinsic Γ is challenging. Here we study a sample of local, predominantly Compton-thick megamaser AGN, where the black hole mass, and thus Eddington luminosity, are well known. We compile results on X-ray spectral fitting of these sources with sensitive high-energy (E>10 keV) NuSTAR data, where X-ray torus models which take into account the reprocessing effects have been used to recover the intrinsic Γ values and X-ray luminosities, LX. With a simple bolometric correction to LX to calculate λEdd, we find a statistically significant correlation between Γ and λEdd (p=0.007). A linear fit to the data yields Γ = (0.41±0.18)log10 λEdd + (2.38±0.20), which is statistically consistent with results for unobscured AGN. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (MBH≈106−107 M⊙) and are highly inclined, our results extend the Γ−λEdd relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of Γ as a growth-rate indicator for accreting black holes, even for Compton-thick AGN.
Accepted by ApJ.
E-mail contact: murray@srl.caltech.edu
Preprint available at http://adsabs.harvard.edu/abs/2016arXiv160609265B
Seoul National University
Deadline: open until filled
Further Information: http://astro2.snu.ac.kr
Applications are invited for two post-doctoral research positions at Seoul National University. Successful candidates will work with Prof. Jong-Hak Woo and his research group to carry out research projects, i.e., 1) gas outflows based on IFU data, and 2) AGN variability and reverberation mapping project. Various research topics on AGNs and galaxy evolution are also available. Preference will be given to those who have experience in AGN-related topics and/or spectroscopic data analysis. Substantial amount of time for independent research will be available.
Astronomy Department at SNU provides a lively research environment. Currently, 12 faculty members (including 2 non-Koreans), and 60 graduate students are actively working on a broad range of topics. Postdoc researchers can work with graduate and undergraduate students in various levels. Korean community has various observational facilities, including access to ALMA and JCMT through EAO, and Gemini telescopes based on short-term contract.
Applicants must hold a Ph.D. degree or equivalent in astronomy. The duration of this position is 2 + 2 years, contingent upon satisfactory research performance. University-subsidized housing is available on campus for monthly rent of 500-600 USD. Travel support and research budget will be also provided.
Two positions are available, but the starting date is negotiable. Applications will be evaluated immediately and applications will be accepted until the positions are filled. Applicants should submit CV, publication list, research summary, research plan, and three letters of reference to woo at astro.snu.ac.kr. Early submission is also encouraged.
Please feel free to contact Jong-Hak Woo if you need further information.
