scholarly journals Elusive Accretion Discs in Low Luminosity AGN

2016 ◽  
Vol 12 (S324) ◽  
pp. 192-195
Author(s):  
J.A. Fernández-Ontiveros ◽  
M.A. Prieto Escudero ◽  
S. Markoff ◽  
L. Reb ◽  
D. Espada ◽  
...  
Keyword(s):  
Thermal Radiation ◽  
Energy Distribution ◽  
Accretion Disk ◽  
Spectral Energy Distribution ◽  
Unified Model ◽  
Accretion Discs ◽  
Continuum Emission ◽  
Spectral Energy

AbstractLow luminosity AGN (LLAGN) represent the vast majority of the AGN population in the near universe. However, they show intrinsic differences when compared to the Unified Model scenario, i.e. a lack of both the big blue bump and the IR bump in their spectral energy distribution (SED), which are the signatures of an accretion disk and a torus, respectively. In this work we present SED for a sample of six LLAGN in the nearby Universe obtained from subarcsec resolution observations. The nature of the IR continuum emission is discussed in the context of non-thermal radiation powered by compact jets.

scholarly journals Nature of the Dusty S-cluster Object (DSO/G2): Pre-main-sequence star with non-spherical dusty envelope

2016 ◽  
Vol 11 (S322) ◽  
pp. 231-232
Author(s):  
M. Zajaček ◽  
M. Valencia-S. ◽  
B. Shahzamanian ◽  
F. Peissker ◽  
A. Eckart ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Main Sequence ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Main Sequence Star ◽  
Continuum Emission ◽  
Spectral Energy ◽  
Galactic Centre ◽  
Infrared Excess ◽  
Sgr A

AbstractNear-infrared observations reveal several infrared-excess sources near the Galactic Centre with emission lines present in their spectra. One of these objects, DSO/G2, which moves around the supermassive black hole (Sgr A*) on a highly eccentric orbit, passed the pericentre at approximately 160 AU in 2014. It remained compact, which implies that at least in this case it is a star embedded in a dusty envelope. The spectral energy distribution and the detection of polarized continuum emission indicate that it is probably a pre-main-sequence star surrounded by a dense envelope with bipolar cavities. In addition, the star associated with DSO/G2 plausibly develops a bow shock due to its supersonic motion. The model of the star surrounded by the non-spherical dusty envelope can reproduce the main characteristics of the DSO/G2 source: 1. spectral energy distribution in near-infrared bands; 2. linear polarization in Ks band; and 3. the overall compact behaviour.

scholarly journals Imaging of 2-mm dust continuum emission towards S106 FIR and its spectral energy distribution

2002 ◽  
Vol 206 ◽  
pp. 22-25
Author(s):  
Ray S. Furuya ◽  
Yoshimi Kitamura ◽  
Alwyn Wootten ◽  
Mark J. Claussen ◽  
Ryohei Kawabe
Keyword(s):  
Star Formation ◽  
Energy Distribution ◽  
Early Phase ◽  
Spectral Energy Distribution ◽  
Continuum Emission ◽  
Spectral Energy ◽  
Bolometric Luminosity ◽  
The Core ◽  
Dust Temperature

The class 0 source S106 FIR is a good candidate to investigate a very early phase of star formation because of the presence of an AU-scale Microjet, discovered by our VLBA H2O maser observations and the absence of an extensive CO outflow. In order to reveal the properties of S106 FIR, we conducted observations of 2-mm continuum emission with the Nobeyama Millmeter Array. We detected a weak compact continuum emission around S106 FIR. We analysed the spectral energy distribution of S106 FIR. It is found that the dust temperature and the β index of the dust opacity range from 31 to 55 K and from 1.4 to 1.6, respectively. Using these results, we computed the mass of the core aound S106 FIR and the bolometric luminosity of 3.1 to 5.8 M⊙ and 230 to 1070 L⊙, respectively.

scholarly journals The inner gaseous accretion disk around a Herbig Be star revealed by near- and mid-infrared spectro-interferometry

2007 ◽  
Vol 3 (S243) ◽  
pp. 337-344
Author(s):  
S. Kraus ◽  
Th. Preibisch ◽  
K. Ohnaka
Keyword(s):  
Accretion Disk ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Continuum Emission ◽  
Spectral Energy ◽  
Be Stars ◽  
Radial Temperature ◽  
Mid Infrared ◽  
Be Star ◽  
Dust Disks

AbstractHerbig Ae/Be stars are pre-main-sequence stars of intermediate mass, which are still accreting material from their environment, probably via a disk composed of gas and dust. Here we present a recent study of the geometry of the inner (AU-scale) circumstellar region around the Herbig Be star MWC 147 using long-baseline interferometry. By combining for the first time near- and mid-infrared spectro-interferometry on a Herbig star, our VLTI/AMBER and VLTI/MIDI data constrain not only the geometry of the brightness distribution, but also the radial temperature distribution in the disk. The emission from MWC 147 is clearly resolved and has a characteristic physical size of ∼1.3 AU and ∼9 AU at 2.2 μm and 11 μm respectively. This increase in apparent size towards longer wavelengths is much steeper than predicted by analytic disk models assuming power-law radial temperature distributions. For a detailed modeling of the interferometric data and the spectral energy distribution of MWC 147, we employ 2-D frequency-dependent radiation transfer simulations. This analysis shows that passive irradiated Keplerian dust disks can easily fit the SED, but predict much lower visibilities than observed, so these models can clearly be ruled out. Models of a Keplerian disk with emission from an optically thick inner gaseous accretion disk (inside the dust sublimation zone), however, yield a good fit of the SED and simultaneously reproduce the observed near- and mid-infrared visibilities. We conclude that the near-infrared continuum emission from MWC 147 is dominated by accretion luminosity emerging from an optically thick inner gaseous disk, while the mid-infrared emission also contains strong contributions from the passive irradiated dust disk.

scholarly journals Active galactic nuclei at z ∼ 1.5 – I. Spectral energy distribution and accretion discs

2014 ◽  
Vol 446 (4) ◽  
pp. 3427-3446 ◽  
Author(s):  
D. M. Capellupo ◽  
H. Netzer ◽  
P. Lira ◽  
B. Trakhtenbrot ◽  
Julián Mejía-Restrepo
Keyword(s):  
Energy Distribution ◽  
Active Galactic Nuclei ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Accretion Discs ◽  
Spectral Energy

scholarly journals Strong FeII emission in NLS1s: An unsolved mystery

2019 ◽  
Vol 15 (S341) ◽  
pp. 297-298
Author(s):  
Swayamtrupta Panda ◽  
Katarzyna Małek ◽  
Marzena Śniegowska ◽  
Bożena Czerny
Keyword(s):  
Energy Distribution ◽  
Accretion Disk ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Photometric Data ◽  
Spectral Energy ◽  
Spectral Fitting ◽  
Main Driver ◽  
Multi Band

AbstractIn Panda et al.2018a, we constructed a refined sample from the original Shen et al.(2011) QSO catalog. Based on our hypothesis — the main driver of the Quasar Main Sequence is the maximum of the accretion disk temperature (TBBB) defined by the Big Blue Bump on the Spectral Energy Distribution (Panda et al.2017; Panda et al.2018b). We select the four extreme sources that have RFeII ⩾ 4.0 and use {CIGALE (Boquien et al.2018) to fit their multi—band photometric data. We also perform detailed spectral fitting including the Fe II pseudo—continuum (based on Śniegowska et al.2018)) to estimate and compare the value of RFEII. We show the dependence of FeII strength on changing metallicity.

scholarly journals Influence of Microlensing on Spectral Anomalies of the Lensed Objects

2011 ◽  
Vol 20 (3) ◽  
Author(s):  
S. Simić ◽  
L. Č. Popović ◽  
P. Jovanović
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Angular Size ◽  
Black Body ◽  
Spectral Energy

AbstractHere we consider the influence of microlensing on the spectrum of a lensed object with the angular size 5 μas accepting that the composite emission of this object originates from three different regions arranged around its center. We assume that the lensed object has three concentric regions with a black-body emission; the temperatures of these regions are 10 000 K, 7500 K and 5000 K. We investigate how the integral spectral energy distribution (SED) of such stratified source changes due to microlensing by a group of solarmass stars. We find that the SED and flux ratios in the photometric B, V and R passbands show considerable changes during a microlens event. This indicates that the flux anomaly observed in some lensed quasars may be caused by microlensing of a stratified object.

scholarly journals Galaxy And Mass Assembly: the evolution of the cosmic spectral energy distribution from z = 1 to z = 0

2017 ◽  
Vol 470 (2) ◽  
pp. 1342-1359 ◽  
Author(s):  
S. K. Andrews ◽  
S. P. Driver ◽  
L. J. M. Davies ◽  
P. R. Kafle ◽  
A. S. G. Robotham ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Mass Assembly
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