scholarly journals An X-ray view of central engines of low-luminosity quasars (LLQSO) in the local Universe

2018 ◽  
Vol 480 (2) ◽  
pp. 1522-1546 ◽  
Author(s):  
Sibasish Laha ◽  
Ritesh Ghosh ◽  
Matteo Guainazzi ◽  
Alex G Markowitz
Keyword(s):  
Local Universe ◽  
X Ray

scholarly journals Host galaxy properties of X-ray active galactic nuclei in the local Universe

2021 ◽  
Author(s):  
L. Koutoulidis ◽  
G. Mountrichas ◽  
I. Georgantopoulos ◽  
E. Pouliasis ◽  
M. Plionis
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Host Galaxy ◽  
Local Universe ◽  
X Ray

scholarly journals The SIX survey: evolution and properties of AGN in the local universe

2013 ◽  
Vol 9 (S304) ◽  
pp. 139-139
Author(s):  
Eugenio Bottacini
Keyword(s):  
Ad Hoc ◽  
High Redshift ◽  
Local Universe ◽  
X Ray ◽  
Systematic Effects ◽  
Coded Mask ◽  
X Ray Background ◽  
Cross Calibration ◽  
End Stage ◽  
Calibration Techniques

AbstractCurrent most sensitive surveys at soft X-ray (~ 0.5–10 keV) energies by Chandra and XMM-Newton preferably sample AGN at high-redshift (z > 0.5). At low-redshift (z < 0.5), where AGN are supposed to be in their evolution end-stage, these sources are very sparsely sampled. The low-redshift universe is best fathomed at hard X–ray energies (> 15 keV) by the INTEGRAL and the Swift missions with their coded-mask telescopes IBIS/ISGRI and BAT respectively. These instruments have two major advantages: 1) they have a huge field of view, hence allowing to sample a large number of AGN at low-redshift; 2) they operate at energies above 15 keV, hence allowing detecting photons with enough power to efficiently pierce even through the Compton-thick torus of AGN. Estimates based on observations with PDS on board the BeppoSAX satellite predict that Compton-thick AGN should dominate over unabsorbed AGN in the local universe playing an important role in reproducing the shape and intensity of the cosmic X-ray background (CXB). However coded-mask detectors suffer from heavy systematic effects preventing them from reaching their theoretical limiting sensitivity. We overcome this limit with a new and alternative approach, which has been designed ad hoc to improve the sensitivity of hard X–ray surveys by using IBIS/ISGRI and BAT. Both telescopes are so close in design that their observations can be combined to obtain a more sensitive survey. The observations are combined with resampling, merging, and cross-calibration techniques. We are able to sample limiting fluxes of the order of ~3.3 times 10−12 erg cm−2 s−1 in the 18–55 keV energy range. This is called the SIX survey, that stands for Swift-INTEGRAL X-ray survey. The SIX survey extends over a wide sky area of 6200 deg2 and it is used to obtain a persistent sample of faint AGN. The source number density (log N - log S) is a factor of 3 better than current parent surveys of BAT and IBIS/ISGRI alone. I will present a study of the evolution of AGN in the local universe discussing the X-ray luminosity function. The properties of the AGN circum-nuclear environment will be discussed checking the consistency with the AGN unification scheme. Also I will compare the results from the SIX survey to the results predicted for the NuSTAR survey. Finally preliminary results of the all-sky SIX survey are presented.

Probing the building blocks of galaxies: Sub-galactic scaling relations between X-ray luminosity, SFR and stellar mass

2019 ◽  
Vol 15 (S341) ◽  
pp. 162-166
Author(s):  
K. Kouroumpatzakis ◽  
A. Zezas ◽  
P. H. Sell ◽  
P. Bonfini ◽  
M. L. N. Ashby ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Building Blocks ◽  
Stellar Mass ◽  
High Mass ◽  
Scaling Relations ◽  
Local Universe ◽  
X Ray ◽  
Star Formation Activity ◽  
X Ray Binaries

AbstractIt is well known that X-ray luminosity (Lx) originating from high mass X-ray binaries (HMXBs) is tightly correlated with the host galaxy’s star formation rate (SFR). We explore this connection using a sample representative of the star-formation activity in the local Universe (Star-Formation Reference Survey; SFRS) along with a comprehensive set of star-formation (radio, FIR, 24μm, 8 μm, Hα, UV, SED fitting) and stellar mass (K-band, 3.6 μm, SED fitting) indicators, and Chandra observations. We investigate the Lx–SFR and Lx– stellar mass (M*) scaling relations down to sub-galactic scales of ∼lkpc2. This way we extend these relations to extremely low SFR (∼10−6M⊙.yr−1) and M* (∼104M⊙). We also quantify their scatter and their dependence on the age of the local stellar populations as inferred from the different age sensitive SFR indicators. These results are particularly important for setting the benchmark for the formation of X-ray binaries in vigorous, but low SFR objects such as galaxies in the early Universe.

Large Scale structure of the local Universe traced by hard X-ray emitting AGNs

2010 ◽  
Author(s):  
Roman Krivonos ◽  
Mikhail Revnivtsev ◽  
A. Comastri ◽  
L. Angelini ◽  
M. Cappi
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Local Universe ◽  
X Ray

Spectroscopic Observations of Baryons in the Local Universe

2005 ◽  
Vol 216 ◽  
pp. 274-289
Author(s):  
Kenneth R. Sembach
Keyword(s):  
Large Scale ◽  
Intergalactic Gas ◽  
Local Universe ◽  
X Ray ◽  
Spectroscopic Observations ◽  
Spectral Diagnostics ◽  
The Galaxy ◽  
X Ray Absorption ◽  
The Universe ◽  
Velocity Cloud

There is increasing observational evidence that hot, highly-ionized interstellar and intergalactic gas plays a significant role in the evolution of galaxies in the local universe. Recent observations from several ultraviolet and X-ray observatories have been used to study the highly ionized high velocity cloud system in the vicinity of the Galaxy, the hot gaseous corona of the Galaxy, and highly ionized absorption-line systems at low redshift. The primary spectral diagnostics of this warm-hot interstellar/intergalactic medium are ultraviolet and X-ray absorption lines of O vi and O vii. The observational data fit well into the framework of current theories for the evolution of large-scale structure in the universe, which predict that a significant fraction of the baryonic material at low redshift is contained in highly ionized intergalactic gas. In this paper, I summarize some of the recent highlights of spectroscopic observations of the hot baryons in the local universe.

scholarly journals Compton-thick AGN in the NuSTAR Era VI: The Observed Compton-thick Fraction in the Local Universe

2021 ◽  
Vol 922 (2) ◽  
pp. 252
Author(s):  
N. Torres-Albà ◽  
S. Marchesi ◽  
X. Zhao ◽  
M. Ajello ◽  
R. Silver ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Limited Sample ◽  
Local Universe ◽  
Telescope Array ◽  
Full Sample ◽  
X Ray ◽  
Ongoing Effort

Abstract We present the analysis of simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR) and XMM-Newton data of eight Compton-thick active galactic nuclei (CT-AGN) candidates selected in the Swift-BAT 100 month catalog. This work is part of an ongoing effort to find and characterize all CT-AGN in the Local (z ≤ 0.05) Universe. We used two physically motivated models, MYTorus and borus02, to characterize the sources in the sample, finding five of them to be confirmed CT-AGN. These results represent an increase of ∼19% over the previous NuSTAR-confirmed, BAT-selected CT-AGN at z ≤ 0.05, bringing the total number to 32. This corresponds to an observed fraction of ∼8% of all AGN within this volume-limited sample, although it increases to 20% ± 5% when limiting the sample to z ≤ 0.01. Out of a sample of 48 CT-AGN candidates, selected using BAT and soft (0.3−10 keV) X-ray data, only 24 are confirmed as CT-AGN with the addition of the NuSTAR data. This highlights the importance of NuSTAR when classifying local obscured AGN. We also note that most of the sources in our full sample of 48 Seyfert 2 galaxies with NuSTAR data have significantly different lines of sight and average torus column densities, favoring a patchy torus scenario.

scholarly journals Investigating ultraluminous X-ray sources through their multiwavelength variability and broadband spectra

2016 ◽  
Vol 12 (S324) ◽  
pp. 31-34
Author(s):  
Luca Zampieri ◽  
Elena Ambrosi ◽  
Amid Nayerhoda
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Stars ◽  
Compact Objects ◽  
Intermediate Mass ◽  
Local Universe ◽  
X Ray ◽  
Multiwavelength Variability ◽  
Black Hole Masses ◽  
Eddington Limit

AbstractThe population of ultraluminous X-ray sources encompasses accreting compact objects with significantly different masses, from black holes of intermediate mass, to black holes of stellar origin, to neutron stars. Investigating these sources will help us answering crucial questions on the distribution of black hole masses and on mass accretion above the Eddington limit in the local Universe, that have potential implications in other astrophysical areas. In order to perform a detailed investigation of ultraluminous X-ray sources, an accurate modeling of their evolution and multiwavelength emission properties is needed. We report some preliminary results of the activities that we are carrying out at present in this area.

scholarly journals NuSTAR observations of heavily obscured Swift/BAT AGNs: Constraints on the Compton-thick AGNs fraction

2019 ◽  
Vol 621 ◽  
pp. A28 ◽  
Author(s):  
I. Georgantopoulos ◽  
A. Akylas
Keyword(s):  
High Energy ◽  
Selection Function ◽  
Number Density ◽  
Local Universe ◽  
X Ray ◽  
Photon Index ◽  
Very High Energy ◽  
History Of ◽  
X Ray Background ◽  
Reflection Component

The evolution of the accretion history of the Universe has been studied in unprecedented detail owing to recent X-ray surveys performed by Chandra and XMM-Newton. A focus on the most heavily obscured or Compton-thick active galactic nuclei (AGNs) is missing in these studies. These AGNs evade detection even in X-ray surveys owing to their extreme hydrogen column densities, which exceed 1024 cm−2. Recently, the all-sky hard X-ray survey performed by Swift/BAT brought a breakthrough, allowing the detection of many of these AGNs. This is because of the very high energy bandpass (14–195 keV) of this instrument, which helps to minimise attenuation effects. In our previous work, we identified more than 50 candidate Compton-thick AGNs in the local Universe, corresponding to an observed fraction of about 7% of the total AGNs population. This number can only be converted to the intrinsic Compton-thick AGNs number density if we know their exact selection function. This function sensitively depends on the form of the Compton-thick AGN spectrum, that is the energy of their absorption turnover, photon-index and its cut-off energy at high energies, and the strength of the reflection component on the matter surrounding the nucleus. For example, the reflection component at hard energies 20–40 keV antagonises the number density of missing Compton-thick AGNs in the sense that the stronger the reflection the easier these sources are detected in the BAT band. In order to constrain their number density, we analysed the spectra of 19 Compton-thick AGNs that have been detected with Swift/BAT and have been subsequently observed with NuSTAR in the 3–80 keV band. We analysed their X-ray spectra using the MYTORUS models which properly take into account the Compton scattering effects. These were combined with physically motivated Comptonisation models, which accurately describe the primary coronal X-ray emission. We derived absorbing column densities that are consistent with those derived by the previous Swift/BAT analyses. We estimate the coronal temperatures to be roughly between 25 and 80 keV corresponding to high energy cut-offs roughly between 75 and 250 keV. Furthermore, we find that the majority of our AGNs lack a strong reflection component in the 20–40 keV band placing tighter constraints on the intrinsic fraction of Compton-thick AGNs. Combining these results with our X-ray background synthesis models, we estimate a percentage of Compton-thick AGNs in the local Universe of ≈20 ± 3 % relative to the type-II AGNs population.

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