scholarly journals Physical Properties of the Extranuclear Emitting Regions in Irregular and Interacting AGNs

1989 ◽  
Vol 134 ◽  
pp. 478-479
Author(s):  
P. Rafanelli
Keyword(s):  
Physical Properties ◽  
Power Law ◽  
Seyfert Galaxies ◽  
Photon Spectrum ◽  
H Ii Regions ◽  
Hard Photon ◽  
Scattering Of Light ◽  
Shock Heating ◽  
Thermal Sources

CCD slit spectra have been obtained at Lick Observatory of a sample of fourteen close interacting and irregular Seyfert galaxies. The spectra of the extranuclear emitting regions have been investigated and classified using the quantitative criteria recommended by Veilleux and Osterbrock to distinguish objects photoionized by thermal sources from objects photoionized by a “power law” continuum. From our data it results that four out of the twenty emitting regions identified are typical H II regions, while eight have spectra photoionized by a hard-photon spectrum. Seven regions show a twofold behavior which is interpreted in terms of a combination of photoionization, shock heating and scattering of light by dust.

scholarly journals Physical properties of the nuclear region in Seyfert galaxies derived from EVN observations

2016 ◽  
Author(s):  
Marcello Giroletti ◽  
Francesca Panessa ◽  
Monica Orienti ◽  
Akihiro Doi
Keyword(s):  
Physical Properties ◽  
Seyfert Galaxies ◽  
Nuclear Region

scholarly journals Dust Distribution in IRAS Seyfert Galaxies

1994 ◽  
Vol 159 ◽  
pp. 355-355
Author(s):  
M. G. Pastoriza ◽  
Charles Bonatto ◽  
Eduardo Bica ◽  
T. Storchi-Bergmann
Keyword(s):  
Emission Line ◽  
Power Law ◽  
Dust Emission ◽  
Seyfert Galaxies ◽  
Emission Model ◽  
Line Region ◽  
Population Type ◽  
The Galaxy ◽  
Dilution Effects ◽  
Dust Distribution

Observational evidences of dust in the nuclear region of AGNs are substantial (Rudy 1984, ApJ, 284, 33; Jones et al. 1984, PASP, 96, 692). The ionization cones observed in several Seyfert galaxies has been interpreted as shadowing effects by a dust obscuring torus which hides the broad emission line region (BLR) and the central source (Wilson 1992; Storchi-Bergmann, Mulchaey and Wilson 1992, ApJ 395, L73). A large sample of optical and far-IR data for IRAS Seyfert galaxies has been analysed together with dust emission models (Bonatto and Pastoriza 1993), where it has been concluded that the same dust emission model can be applied to both Seyfert types. In order to further study the effects of dust in the spectra of active galactic nuclei, we have obtained spectrophotometry of 21 IRAS Seyfert galaxies in the range 3500–7200 Å and analyse them in conjuction with their IRAS fluxes. The stellar population type is derived from comparisons with normal galaxy templates using dilution effects in the K CaII line as discriminator. For 55% of the sample the population is of late type. For the rest, blue continua due to recent star formation and/or power-law may amount up to 30% at 4000Å. We conclude that the bulge stellar populations of IRAS Seyfert galaxies are similar to those of normal spirals, except that they are more reddened by E(B-V)i ∼ 0.20. Population-subtracted emission line ratios indicate on average stronger reddening for the narrow-line region (E(B-V)l ∼ 0.8. From photoionization models a power-law index for the ionizing continuum α=1.5, and a metallicity larger than solar are obtained. The most luminous IRAS galaxy of the sample (IRAS555) is discuss in detail: in order to be compatible with the observed IRAS fluxes and the optical stellar continuum, the ionizing continuum must be reddened by AV > 10 magnitudes. Consequently a dust structure in this galaxy appears to be increasingly affecting stars and gas towards the galaxy center.

scholarly journals 11.12. X-ray emission from LINERs observed with ASCA

1998 ◽  
Vol 184 ◽  
pp. 479-480 ◽  
Author(s):  
Y. Terashima ◽  
H. Kunieda ◽  
P.J. Serlemitsos ◽  
A. Ptak
Keyword(s):  
Power Law ◽  
Seyfert Galaxies ◽  
X Ray ◽  
Photon Index

We present X-ray observations of LINERs with ASCA. We detected a hard point-like source of X-ray luminosity of 1040–1041 erg s−1 at the nucleus. Their hard X-ray continuum is well represented by power-law of photon index ~ 1.8. The X-ray to Hα luminosity ratio LX/LHα is quite similar to Seyfert galaxies and strongly support the presence of low luminosity AGNs.

scholarly journals On the ionizing populations in GEHRs: unveiling integrated properties from the analysis of the Wolf-Rayet population

2003 ◽  
Vol 212 ◽  
pp. 698-699
Author(s):  
Marcelo Castellanos ◽  
Ángeles I. Díaz ◽  
Elena Terlevich
Keyword(s):  
Physical Properties ◽  
Emission Line ◽  
Massive Stars ◽  
Current Understanding ◽  
Evolutionary Synthesis ◽  
H Ii Regions ◽  
Expanding Atmospheres ◽  
Stars Evolution

In recent years, the detection of Wolf-Rayet stars in Giant Extragalactic H ii Regions (GEHRs) has yielded several questions about our current understanding of massive stars evolution and hot expanding atmospheres, the age of the ionizing populations and their impact onto the physical properties of GEHRs. Here, we present spectrophotometric observations of four extragalactic GEHRs which show WR features in their spectra. Our goal is to reproduce simultaneously the observed WR properties and the emission-line spectra with the help of current evolutionary synthesis models.

scholarly journals Radio Emission from the Vela?Puppis Region

1958 ◽  
Vol 11 (4) ◽  
pp. 550 ◽  
Author(s):  
H Rishbeth
Keyword(s):  
Radio Emission ◽  
Galactic Structure ◽  
H Ii Regions ◽  
Radio Telescopes ◽  
Outstanding Feature ◽  
Thermal Origin ◽  
Thermal Sources

The Vela-Puppis region has been surveyed with Mills Cross radio telescopes, and radio isophotes plotted at two wavelengths. Many discrete sources have been observed. Several H II regions have been detected in emission at 3�5 m and in absorption at 15�2 m; the radiation from such objects is of thermal origin. The outstanding feature of this region is a group of strong non-thermal sources near the galactic equator. These are superimposed on an intense belt of radiation along the equator, and this, too, is certainly non-thermal in origin. Some correlation with galactic structure is suggested.

Influence of Planets on the Magnetic Activity of Sun-Like Stars

2018 ◽  
Vol 13 (S340) ◽  
pp. 242-243
Author(s):  
Shashanka R. Gurumath ◽  
K. M. Hiremath ◽  
V. Ramasubramanian
Keyword(s):  
Physical Properties ◽  
Power Law ◽  
Magnetic Activity ◽  
The Sun ◽  
Stellar Activity ◽  
Index Data ◽  
Planetary Mass ◽  
Power Law Decay ◽  
Host Stars

AbstractBy considering the physical properties of Sun-like G stars and their exoplanets, present study examines whether presence of planets near the host stars enhances their stellar activity. In order to attain this goal, chromospheric RHK index data-a proxy for the magnetic activity-for the stars with and without planets is considered. With the reasonable constraints on the exoplanetary data, we obtained a power law decay relationship between the magnetic activity of host stars and their ages, for stars with and without planets. Both these results strongly suggest that there is no difference in magnetic activity of the sun-like stars with and without presence of planets. In order to confirm this result, further we also examine an association between the host stars RHK index that have exoplanets and their respective exoplanetary masses. We find that magnitude of RHK (hence magnetic activity) of the host stars is independent of presence of planetary mass in its vicinity.

scholarly journals Infrared Radiation from Compact Objects

1972 ◽  
Vol 44 ◽  
pp. 163-163
Author(s):  
G. Neugebauer
Keyword(s):  
Power Law ◽  
Infrared Radiation ◽  
Optical Emission ◽  
Seyfert Galaxies ◽  
Compact Objects ◽  
Infrared Excess ◽  
Large Variability ◽  
Infrared Observations ◽  
Ngc 1068 ◽  
To Come

Current infrared observations of Seyfert galaxies, QSOs, and compact galaxies in the lists of Markarian and Zwicky have been reviewed. The bright Seyfert galaxies generally show similar infrared excesses at the longer wavelengths accessible from the ground. Only NGC 1068 has been observed, by F. J. Low, in the 100μ region; if the spectral distributions of all Seyfert galaxies are similar to that of NGC 1068, the intrinsic luminosities vary from 1 to 100 × 1044 erg s−1. Measurements by Kleinmann and Low, Gillett and Stein, Pacholczyk, and Penston and Neugebauer at 10 and 2μ apparently confirm variability of NGC 1068 and NGC 4151 on a time scale too short to allow the infrared radiation to come predominantly from dust shells.The published infrared observations of QSOs have been limited to wavelengths shorter than 3.5μ except for 3C 273. The energy distributions either show a power law fall-off, a flat spectrum, or a combination of these two. Those four QSOs which show large variability all have steep power law spectra. If one accepts that the distance of QSOs are cosmological, the extrapolated luminosity at 2μ of several QSOs exceeds that of 3C 273. The integrated luminosity of 3C 273 depends critically on the spectrum in the unobserved 10–1000μ region, but is probably in the range 1047 to 1048 erg s−1.The infrared observations of the compact Markarian and Zwicky objects show a correlation between the infrared excess and the broad optical emission lines. Presumably the infrared can be used to differentiate between the stellar and non-thermal components of the radiation from these objects.

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