scholarly journals State-of-the-art AGN SEDs for photoionization models: BLR predictions confront the observations

2020 ◽  
Vol 494 (4) ◽  
pp. 5917-5922 ◽  
Author(s):  
G J Ferland ◽  
C Done ◽  
C Jin ◽  
H Landt ◽  
M J Ward
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
X Ray ◽  
Line Region ◽  
Energy Conserving ◽  
Far Ultraviolet ◽  
New Generation

ABSTRACT The great power offered by photoionization models of active galactic nuclei emission line regions has long been mitigated by the fact that very little is known about the spectral energy distribution (SED) between the Lyman limit, where intervening absorption becomes a problem, and  0.3 keV, where soft X-ray observations become possible. The emission lines themselves can, to some degree, be used to probe the SED, but only in the broadest terms. This paper employs a new generation of theoretical SEDs that are internally self-consistent, energy conserving, and tested against observations, to infer properties of the emission-line regions. The SEDs are given as a function of the Eddington ratio, allowing emission-line correlations to be investigated on a fundamental basis. We apply the simplest possible tests, based on the foundations of photoionization theory, to investigate the implications for the geometry of the emission-line region. The SEDs become more far-ultraviolet bright as the Eddington ratio increases, so the equivalent widths of recombination lines should also become larger, an effect that we quantify. The observed lack of correlation between Eddington ratio and equivalent width shows that the cloud covering factor must decrease as Eddington ratio increases. This would be consistent with recent models proposing that the broad-line region is a failed dusty wind off the accretion disc.

scholarly journals To TDE or not to TDE: the luminous transient ASASSN-18jd with TDE-like and AGN-like qualities

2020 ◽  
Vol 494 (2) ◽  
pp. 2538-2560 ◽  
Author(s):  
J M M Neustadt ◽  
T W-S Holoien ◽  
C S Kochanek ◽  
K Auchettl ◽  
J S Brown ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
Tidal Disruption ◽  
Optical Telescope ◽  
X Ray ◽  
Radiated Energy ◽  
The Galaxy ◽  
Order Of Magnitude

ABSTRACT We present the discovery of ASASSN-18jd (AT 2018bcb), a luminous optical/ultraviolet(UV)/X-ray transient located in the nucleus of the galaxy 2MASX J22434289–1659083 at z = 0.1192. Over the year after discovery, Swift UltraViolet and Optical Telescope (UVOT) photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking blackbody with temperature $T \sim 2.5 \times 10^{4} \, {\rm K}$, a maximum observed luminosity of $L_{\rm max} = 4.5^{+0.6}_{-0.3}\times 10^{44} \, {\rm erg \,s}^{-1}$, and a radiated energy of $E = 9.6^{+1.1}_{-0.6} \times 10^{51} \, {\rm erg}$. X-ray data from Swift X-Ray Telescope (XRT) and XMM–Newton show a transient, variable X-ray flux with blackbody and power-law components that fade by nearly an order of magnitude over the following year. Optical spectra show strong, roughly constant broad Balmer emission and transient features attributable to He ii, N iii–v, O iii, and coronal Fe. While ASASSN-18jd shares similarities with tidal disruption events (TDEs), it is also similar to the newly discovered nuclear transients seen in quiescent galaxies and faint active galactic nuclei (AGNs).

scholarly journals Photometric redshifts for X-ray-selected active galactic nuclei in the eROSITA era

2019 ◽  
Vol 489 (1) ◽  
pp. 663-680 ◽  
Author(s):  
M Brescia ◽  
M Salvato ◽  
S Cavuoti ◽  
T T Ananna ◽  
G Riccio ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Large Fraction ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Training Sample ◽  
Spectral Energy ◽  
Ancillary Data ◽  
Photometric Redshifts ◽  
X Ray

ABSTRACT With the launch of eROSITA (extended Roentgen Survey with an Imaging Telescope Array), successfully occurred on 2019 July 13, we are facing the challenge of computing reliable photometric redshifts for 3 million of active galactic nuclei (AGNs) over the entire sky, having available only patchy and inhomogeneous ancillary data. While we have a good understanding of the photo-z quality obtainable for AGN using spectral energy distribution (SED)-fitting technique, we tested the capability of machine learning (ML), usually reliable in computing photo-z for QSO in wide and shallow areas with rich spectroscopic samples. Using MLPQNA as example of ML, we computed photo-z for the X-ray-selected sources in Stripe 82X, using the publicly available photometric and spectroscopic catalogues. Stripe 82X is at least as deep as eROSITA will be and wide enough to include also rare and bright AGNs. In addition, the availability of ancillary data mimics what can be available in the whole sky. We found that when optical, and near- and mid-infrared data are available, ML and SED fitting perform comparably well in terms of overall accuracy, realistic redshift probability density functions, and fraction of outliers, although they are not the same for the two methods. The results could further improve if the photometry available is accurate and including morphological information. Assuming that we can gather sufficient spectroscopy to build a representative training sample, with the current photometry coverage we can obtain reliable photo-z for a large fraction of sources in the Southern hemisphere well before the spectroscopic follow-up, thus timely enabling the eROSITA science return. The photo-z catalogue is released here.

scholarly journals The Nuclear Reddening Curve for Active Galactic Nuclei and the Shape of the Infrared to X‐Ray Spectral Energy Distribution

2004 ◽  
Vol 616 (1) ◽  
pp. 147-156 ◽  
Author(s):  
C. Martin Gaskell ◽  
Rene W. Goosmann ◽  
Robert R. J. Antonucci ◽  
David H. Whysong
Keyword(s):  
Energy Distribution ◽  
Active Galactic Nuclei ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
X Ray

scholarly journals Lifting the curtain: The Seyfert galaxy Mrk 335 emerges from deep low-state in a sequence of rapid flare events

2020 ◽  
Vol 643 ◽  
pp. L7
Author(s):  
S. Komossa ◽  
D. Grupe ◽  
L. C. Gallo ◽  
P. Poulos ◽  
D. Blue ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Optical Emission ◽  
Line Of Sight ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Partial Covering

Context. The narrow-line Seyfert 1 galaxy Mrk 335 was one of the X-ray brightest active galactic nuclei, but it has systematically faded since 2007. Aims. We report the discovery with Swift of a sequence of bright and rapid X-ray flare events that reveal the emergence of Mrk 335 from its ultra-deep multiyear low state. Methods. Results are based on our dedicated multiyear monitoring of Mrk 335 with Swift. Results. Unlike other bright active galactic nuclei, the optical–UV is generally not correlated with the X-rays in Mrk 335 on a timescale of days to months. This fact either implies the absence of a direct link between the two emission components; or else implies that the observed X-rays are significantly affected by (dust-free) absorption along our line of sight. The UV and optical, however, are closely correlated at the 99.99% confidence level. The UV is leading the optical by Δt = 1.5 ± 1.5 d. The Swift X-ray spectrum shows strong deviations from a single power law in all brightness states of the outbursts, indicating that significant absorption or reprocessing is taking place. Mrk 335 displays a softer-when-brighter variability pattern at intermediate X-ray count rates, which has been seen in our Swift data since 2007 (based on a total of 590 observations). This pattern breaks down at the highest and lowest count rates. Conclusions. We interpret the 2020 brightening of Mrk 335 as a decrease in column density and covering factor of a partial-covering absorber along our line of sight in the form of a clumpy accretion-disk wind that reveals an increasing portion of the intrinsic emission of Mrk 335 from the disk and/or corona region, while the optical emission-line regions receive a less variable spectral energy distribution. This then also explains why Mrk 335 was never seen to change its optical Seyfert type (not “changing look”) despite its factor ∼50 X-ray variability with Swift.

scholarly journals Optical Singly-Ionized Iron Emission in Radio-Quiet and Relativistically Jetted Active Galactic Nuclei

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 484
Author(s):  
Paola Marziani ◽  
Marco Berton ◽  
Swayamtrupta Panda ◽  
Edi Bon
Keyword(s):  
Active Galactic Nuclei ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Detailed Comparison ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Ionized Gas ◽  
Line Region ◽  
The Difference

The issue of the difference between optical and UV properties of radio-quiet and radio-loud (relativistically “jetted”) active galactic nuclei (AGN) is a long standing one, related to the fundamental question of why a minority of powerful AGN possess strong radio emission due to relativistic ejections. This paper examines a particular aspect: the singly-ionized iron emission in the spectral range 4400–5600 Å, where the prominent HI Hβ and [Oiii]λλ4959,5007 lines are also observed. We present a detailed comparison of the relative intensity of Feii multiplets in the spectral types of the quasar main sequence where most jetted sources are found, and afterwards discuss radio-loud narrow-line Seyfert 1 (NLSy1) nuclei with γ-ray detection and with prominent Feii emission. An Feii template based on I Zw 1 provides an accurate representation of the optical Feii emission for RQ and, with some caveats, also for RL sources. CLOUDY photoionization simulations indicate that the observed spectral energy distribution can account for the modest Feii emission observed in composite radio-loud spectra. However, spectral energy differences alone cannot account for the stronger Feii emission observed in radio-quiet sources, for similar physical parameters. As for RL NLSy1s, they do not seem to behave like other RL sources, likely because of their different physical properties, that could be ultimately associated with a higher Eddington ratio. active galactic nuclei; optical spectroscopy; ionized gas; broad line region

scholarly journals Molecular hydrogen and [Fe ii] in active galactic nuclei – III. Low-ionization nuclear emission-line region and star-forming galaxies

2013 ◽  
Vol 430 (3) ◽  
pp. 2002-2017 ◽  
Author(s):  
R. Riffel ◽  
A. Rodríguez-Ardila ◽  
I. Aleman ◽  
M. S. Brotherton ◽  
M. G. Pastoriza ◽  
...  
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Molecular Hydrogen ◽  
Galactic Nuclei ◽  
Star Forming ◽  
Line Region
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